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Turbulent drag effectiveness and shear stability of xanthan‐gum‐based graft copolymers
Abstract
A number of graft copolymers of xanthan gum and polyacrylamide have been synthesized by grafting acrylamide onto xanthan gum using the ceric-ion-initiated solution polymerization technique. The effects of various synthesis parameters such as amount of catalyst, reaction time, and ratio of xanthan and acrylamide on drag reduction effectiveness of the graft copolymers have been studied. The scaling up of grafting reaction has been accomplished in 40-L reactor. The drag reduction effectiveness of the graft copolymers is investigated over a wide range of concentrations and Reynolds numbers. It is shown that the maximum drag reduction obtainable in xanthan gum solutions above 300 ppm can be obtained in solutions of graft copolymers at concentrations of 100–150 ppm. The grafting also improves the shear stability at higher Reynolds numbers. The shear stability of the graft copolymers at constant wall stress has been found to be superior to polyacrylamide and the mixtures of polyacrylamide and xanthan gum. In general, the shear stability of graft copolymers and polyacrylamide is shown to increase with concentration. The drag reduction characteristics and shear stability have been discussed in terms of structural features of the graft copolymers. The drag reduction characteristics of the graft copolymers are found to be similar to those of flexible polymers.
... It has been observed that relative viscosity of xanthan gum-g-2- Acrylamidoglycolic acid is lower than xanthan gum (Fig. 5). This might be due to presence of grafted chains which make the molecule more flexible and reduce the viscosity drastically ( Singh et al., 1989). Xanthan gum, like other polysaccharide solutions, is highly prone to biodegradation, and it was found that its solution after 72 h of its preparation starts degrading and during 10 days the solution showed considerable loss of viscosity (Fig. 5, Line A). ...
... The graft copolymer solution was subjected for same type of study for biodegradation, and it has been observed that graft copoly- mer solution showed no loss of viscosity up to 10 days (Fig. 5, Line B). These results show that the graft copolymer is less sus- ceptible to biodegradation and results have also been reported by others (Ungeheur, Bewersdorff, & Singh 1989). This is in an agreement with the fact that by incorporating relatively poly (2- Acrylamidoglycolic acid) chains in graft copolymer it can be made less susceptible to bacterial attack (Seaman, 1980). ...
... It has been observed that relative viscosity of partially carboxymethy- lated guar gum-g-2-acrylamidoglycolic acid is lower than partially carboxymethylated guar gum (Fig. 5). This might be due to pres- ence of grafted chains which make the molecule more flexible and reduce the viscosity drastically ( Singh et al., 1989). Partially car- boxymethylated guar gum, like other polysaccharide solutions, is highly prone to biodegradation, and it was found that its solu- tion after 72 h of its preparation starts degrading and during 10 days the solution showed considerable loss of viscosity (Fig. 5, Line A). ...
... The graft copolymer solution was subjected for same type of study for biodegradation, and it has been observed that graft copolymer solution showed no loss of viscosity up to 10 days (Fig. 5, Line B). These results show that the graft copoly- mer is less susceptible to biodegradation and results have also been reported by others (Ungeheur, Bewersdorff, & Singh, 1989). This is in an agreement with the fact that by incorporating relatively poly (2-acrylamidoglycolic acid) chains in graft copoly- mer it can be made less susceptible to bacterial attack (Seaman, 1980). ...
... It has been observed that relative viscosity of partially carboxymethylated guar gum-g-2-acrylamidoglycolic acid is lower than partially carboxymethylated guar gum (Fig. 5). This might be due to presence of grafted chains which make the molecule more flexible and reduce the viscosity drastically (Singh et al., 1989). Partially carboxymethylated guar gum, like other polysaccharide solutions, is highly prone to biodegradation, and it was found that its solution after 72 h of its preparation starts degrading and during 10 days the solution showed considerable loss of viscosity (Fig. 5, Line A). ...
... The graft copolymer solution was subjected for same type of study for biodegradation, and it has been observed that graft copolymer solution showed no loss of viscosity up to 10 days (Fig. 5, Line B). These results show that the graft copolymer is less susceptible to biodegradation and results have also been reported by others (Ungeheur, Bewersdorff, & Singh, 1989). This is in an agreement with the fact that by incorporating relatively poly (2-acrylamidoglycolic acid) chains in graft copolymer it can be made less susceptible to bacterial attack (Seaman, 1980). ...
Carbohydrate Polymers j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c a r b p o l a b s t r a c t An unreported graft copolymer of 2-acrylamidoglycolic acid with partially carboxymethylated guar gum has been synthesized under nitrogen atmosphere using peroxymonosulphate/thiourea redox pair at 40 • C. The effect of reaction conditions on grafting parameters i.e., grafting ratio, efficiency, conversion, add on, homopolymer and rate of grafting has been studied. Experimental results show that maximum grafting has been obtained at 0.1 g dm −3 concentration of partially carboxymethylated guar gum and 5.3 × 10 −2 mol dm −3 concentration of 2-acrylamidoglycolic acid. It has been observed that grafting ratio, add on, conversion, efficiency and rate of grafting increase up to 5.0 × 10 −3 mol dm −3 of hydrogen ion, 2.4 × 10 −3 mol dm −3 of thiourea, 10 × 10 −3 mol dm −3 of peroxymonosulphate and 40 • C of temperature. Grafted copolymer has been characterized by FTIR spectroscopy and thermogravimetric analysis. Physico-chemical properties of partially carboxymethylated guar gum-g-2-acrylamidoglycolic acid have been determined.
... It was observed that relative viscosity of acrylic acid-g-carrageenan is lower than the carrageenan (Figure 4). This might be due to the presence of grafted chains, which make the molecule more flexible and reduce the viscosity drastically [37]. Initially up to 40 hours, viscosity of the grafted copolymer solution was increased that was due the swelling nature of polyacrylic acid chains, which absorbs water resulting in swelling in grafted copolymer. ...
... The graft copolymer solution was subjected to the same type of study for biodegradation, and it was observed that graft copolymer solution showed no loss of viscosity up to 10 days ( Figure 4). These results show that the grafted copolymer is less susceptible to biodegradation, and similar results were reported by others [37] also. This is in agreement with the fact that by incorporating relatively poly(acrylic acid) chains onto carrageenan, the carrageenan can be made less susceptible to bacterial attack [38]. ...
The effects of concentrations of peroxymonosulphate, mercaptosuccinic acid, hydrogen ion, acrylic acid, and carrageenan on grafting parameters were studied to find out the maximum grafting ratio. The corresponding values were found to be
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g dm−3, respectively. The optimal reaction time duration and reaction temperature were found to be 120 min and 40°C, respectively. The effect of hydrogen ion variation from 5.0 up to
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mol dm−3 shows prompt changes on grafting parameter. The grafted copolymer was found more thermally stable than the ungrafted substrate. Also the grafted copolymer absorbed more water, namely hazardous metal cations. Hg2+, Pb2+, and Cd2+, showed better flocculation behavior than carrageenan.
... It has been observed that relative viscosity of partially carboxymethylated guar gum-g-2-acrylamidoglycolic acid is lower than partially carboxymethylated guar gum (Fig. 5). This might be due to presence of grafted chains which make the molecule more flexible and reduce the viscosity drastically ( Singh et al., 1989). Partially carboxymethylated guar gum, like other polysaccharide solutions, is highly prone to biodegradation, and it was found that its solution after 72 h of its preparation starts degrading and during 10 days the solution showed considerable loss of viscosity (Fig. 5, Line A). ...
... The graft copolymer solution was subjected for same type of study for biodegradation, and it has been observed that graft copolymer solution showed no loss of viscosity up to 10 days (Fig. 5, Line B). These results show that the graft copolymer is less susceptible to biodegradation and results have also been reported by others (Ungeheur, Bewersdorff, & Singh, 1989). This is in an agreement with the fact that by incorporating relatively poly (2-acrylamidoglycolic acid) chains in graft copolymer it can be made less susceptible to bacterial attack (Seaman, 1980). ...
a b s t r a c t An unreported graft copolymer of 2-acrylamidoglycolic acid with partially carboxymethylated guar gum has been synthesized under nitrogen atmosphere using peroxymonosulphate/thiourea redox pair at 40 • C. The effect of reaction conditions on grafting parameters i.e., grafting ratio, efficiency, conversion, add on, homopolymer and rate of grafting has been studied. Experimental results show that maximum grafting has been obtained at 0.1 g dm −3 concentration of partially carboxymethylated guar gum and 5.3 × 10 −2 mol dm −3 concentration of 2-acrylamidoglycolic acid. It has been observed that grafting ratio, add on, conversion, efficiency and rate of grafting increase up to 5.0 × 10 −3 mol dm −3 of hydrogen ion, 2.4 × 10 −3 mol dm −3 of thiourea, 10 × 10 −3 mol dm −3 of peroxymonosulphate and 40 • C of temperature. Grafted copolymer has been characterized by FTIR spectroscopy and thermogravimetric analysis. Physico-chemical properties of partially carboxymethylated guar gum-g-2-acrylamidoglycolic acid have been determined.
... Starch nanoparticle, like other polysaccharide solutions, is highly susceptible to biodegradation, and it was found that its solution after 3 days of preparation started to degrade, and after 10 days, the solution showed considerable loss of relative viscosity µrel ( Figure 5). The poly (AN)-starch nanoparticle graft copolymer (60.1% G.Y.) solution was subjected to the same type of study for biodegradation, and it was observed that graft copolymer solution showed no loss of viscosity up to 10 days .These results showed that the grafted product is less susceptible to biodegradation, and similar results were reported by others [19] also. This is in agreement with the fact that by incorporating relatively poly (acrylonitrile) chains onto starch nanoparticle, the latter can be made less susceptible to bacterial attack and its resistance to biodegradation can be amended [20]. ...
Unreported peroxymonosulfate/mandelic acid as a redox pair initiation system has been used to graft copolymerizes acrylonitrile onto our previously prepared starch nanoparticle (SNPs) in aqueous medium under nitrogen atmosphere. Optimization of the grafting conditions was studied and the grafting parameters were expressed in terms of graft yield %, graft reaction efficiency % and homopolymer %. Fourier transformer infrared spectroscopy (FTIR), Scanning electron microscope (SEM) and thermal gravimetric analysis (TGA) techniques confirmed the synthesis of the precursor’s materials and the success of the grafting onto starch nanoparticle. The resultant copolymer was found to be more thermally stable and more resistance to biodegradability than the starch nanoparticle counterparts. Besides, the optimum conditions were obtained when using 1 g starch nanoparticle, 2 ml of AN (based on weight of substrate), 30 m mol/l potassium peroxymonosulphate, 8 m mol/l mandelic acid, 2 hours reaction time and 45°C of temperature.
... The graft copolymer solution was subjected for same type of study for biodegradation, and it has been observed that graft copoly- mer solution showed no loss of viscosity up to 10 days (Fig. 5, Line B). These results show that the graft copolymer is less sus- ceptible to biodegradation and results have also been reported by others (Ungeheur, Bewersdorff, & Singh, 1989). This is in an agreement with the fact that by incorporating relatively inert poly (k-carrageenan-g-N-vinyl-2-pyrrolidone) chains in graft copoly- mer it can be made less susceptible to bacterial attack (Seaman, 1980). ...
... that relative viscosity of partially carboxymethylated guar gum-g- N-vinyl-2-pyrrolidone is lower than partially carboxymethylated guar gum (Fig. 5). This might be due to presence of grafted chains which make the molecule more flexible and reduce the viscos- ity drastically (Ungeheur, Bewersdorff, & Singh, 1989). Partially carboxymethylated guar gum solution, like other polysaccharide solutions, is highly prone to biodegradation, and it was found that its solution after 72 h of its preparation starts degrading and during 10 days the solution showed considerable loss of viscosity (Fig. 5, curve A). ...
... It has been observed that relative viscosity of j-carrageenan-g-N-vinyl formamide is lower than j-carrageenan (Fig. 4). This might be due to presence of grafted chains which make the molecule more flexible and reduce the viscosity drastically (Ungeheur, Bewersdorff, & Singh, 1989). j-Carrageenan solution, like other polysaccharide solutions, is highly prone to biodegradation, and it was found that its solution after 72 h of its preparation starts degrading and during 10 days the solution showed considerable loss of viscosity (Fig. 4, Line A). ...
... It has been observed that relative viscosity of partially carboxymethylated guar gum-g- vinylsulfonic acid is lower than partially carboxymethylated guar gum (Fig. 6). This might be due to presence of grafted chains which make the molecule more flexible and reduce the viscos- ity drastically (Ungeheur, Bewersdorff, & Singh, 1989). Partially carboxymethylated guar gum solution, like other polysaccharide solutions, is highly prone to biodegradation, and it was found that its solution after 72 h of its preparation starts degrading and during 10 days the solution showed considerable loss of viscosity (Fig. 6, Line A). ...
... The graft copolymer solution was subjected for same type of study for biodegradation, and it has been observed that graft copolymer solution showed no loss of viscosity up to 10 days (Fig. 5, Line B). These results show that the graft copolymer is less susceptible to biodegradation and results have also been reported by others (Ungeheur, Bewersdorff, & Singh, 1989). This is in an agreement with the fact that by incorporating relatively poly (vinyl sulfonic acid) chains in graft copolymer it can be made less susceptible to bacterial attack (Seaman, 1980). ...
... Xanthan gum can form very viscous aqueous solutions, and at sufficiently high polymer concentration, it exhibits weak gel-like properties. Therefore, it has been widely used and investigated in areas such as food (e.g. as thickener), pharmaceutical, cosmetics, biomedical, tissue engineering and oil industries (Ungeheuer et al. 1989;Zirnsak et al. 1999;Lachke 2004;Mendes et al. 2012). The production of electrospun xanthan fibers has been challenging due to the insufficient entanglements required for electrospinning using water as solvent (Stijnman et al. 2011). ...
Electrohydrodynamic processing, including electrospinning and electrospraying, is an emerging technique for the encapsulation of bioactive ingredients (e.g. omega-3, vitamins, antioxidants, probiotics) with interest for the functional food industry. This chapter presents the fundamentals of electrohydrodynamic processes for the production of nano-microstructures (fibers or capsules) loaded with bioactive compounds. Particularly, it focuses on the properties as well as electrospinning and electrospray processing of food-grade polymers. The physicochemical characteristics of the resulting nano-microencapsulates will also be discussed. Electrospun and electrospray food-grade polymers include biopolymers such as proteins (e.g. zein, gelatin, whey, casein, amaranth, soy, egg and fish protein) and polysaccharides (e.g. pullulan, dextran, chitosan, starch, alginate, cellulose, cyclodextrin, xanthan gum), as well as blends of biopolymers with biocompatible synthetic polymers (e.g. poly-vinyl alcohol).
... Over the past years, the xanthan gum has received a great attention due to its friendly features such as non-toxicity, biocompatibility and biodegradability. Also, it exhibits unique and valuable properties that enhance its versatility in many applications (oils, cosmetics, consumer products, pharmaceutical and biomedical applications, tissue engineering, etc.) as thickening, water binding or gelling agent, emulsion/suspension stabilizer [1][2][3][4][5]. Xanthan gum provides stability to the emulsion for long periods, up to 1 year, being of interest in food industry [6] . ...
The properties of xanthan gum (XG) aqueous solutions were investigated by using viscometric, electrokinetic and surface tension measurements. The effects of polymer concentration, temperature and pH on the viscosity of the XG solutions were evaluated and discussed. Zeta potential data determined for XG solutions in water in the temperature range of 15–45 °C corroborated with the results obtained from the viscometric investigations suggest the occurence of conformational changes above 36 °C. The activation energy of flow and that associated with the electrophoretic migration of the charged particles were estimated for XG solutions in water. In acid medium, xanthan gum determines a slight decrease of the surface tension of pure water at all investigated temperatures.
... It has been observed that relative viscosity of j-carrageenan-g-N-vinyl formamide is lower than j-carrageenan (Fig. 4). This might be due to presence of grafted chains which make the molecule more flexible and reduce the viscosity drastically (Ungeheur, Bewersdorff, & Singh, 1989). j-Carrageenan solution, like other polysaccharide solutions, is highly prone to biodegradation, and it was found that its solution after 72 h of its preparation starts degrading and during 10 days the solution showed considerable loss of viscosity (Fig. 4, Line A). ...
Thermal analysis N-vinyl formamide Metal ion sorption Water swelling behaviour Flocculation Resistance to biodegradability a b s t r a c t j-Carrageenan-g-N-vinyl formamide was synthesized by free radical initiation using the potassium mon-opersulphate (PMS)/malonic acid redox pair in an inert atmosphere. The effects of variation of different reactant on grafting parameters have been studied by varying the concentration. Grafting ratio, add on and conversion showed an increasing trend on increasing the concentration of N-vinyl formamide, malonic acid, j-carrageenan and the concentration of PMS from 6 Â 10 À3 to 22 Â 10 À3 mol dm À3 . The optimum temperature and time for grafting of N-vinyl formamide onto j-carrageenan was found to be 40 °C and 120 min, respectively. The metal ion sorption, swelling behaviour, flocculation and resistance to biodegradation properties have been studied. Flocculation capability of j-carrageenan and j-carra-geenan-g-N-vinyl formamide for both coking and non-coking coals has been studied for the treatment of coal mine waste water. The graft copolymer was characterized by FT-IR spectroscopy and thermogravi-metric analysis.
... Intrinsic viscosity of sodium carboxymethylcellulose and sodium carboxymethylcellulose-g-N-vinylformamide is found to be 7.9 and 6.5, respectively, and results are presented in Fig. 6. The graft copolymer of N-vinylformamide shows lower intrinsic viscosity than sodium carboxymethylcellulose because longer grafted chains are available to make the molecule very flexible and thus reduces the viscosity drastically (Ungeheur, Bewersdorff, & Singh, 1989). ...
a b s t r a c t The present paper reports the graft copolymerization of N-vinylformamide onto sodium carboxymeth-ylcellulose by free radical polymerization using potassium peroxymonosulphate/thiourea redox sys-tem in an inert atmosphere. The reaction conditions for maximum grafting have been optimized by varying the reaction variables, including the concentration of N-vinylformamide (12.0 Â 10 À2 – 28.0 Â 10 À2 mol dm À3), potassium peroxymonosulphate (4.0 Â 10 À3 –12.0 Â 10 À3 mol dm À3), thiourea (1.2 Â 10 À3 –4.4 Â 10 À3 mol dm À3), sulphuric acid (2.0 Â 10 À3 –10.0 Â 10 À3 mol dm À3), sodium carboxy-methylcellulose (0.2–1.8 g dm À3) along with time duration (60–180 min) and temperature (25–45° C). Water swelling capacity, metal ion sorption and flocculation studies of synthesized graft copolymer have been performed with respect to the parent polymer. The graft copolymer has been characterized by FTIR spectroscopy and thermogravimetric analysis.
... The graft copolymer of 4-vinyl pyridine shows lower intrinsic viscosity than partially carboxymethylated guar gum because longer grafted chains are available. Sufficiently longer graft chains make the molecules very flexible and thus reduce the viscosity drastically (Ungeheur, Bewersdorff, & Singh, 1989). ...
Unreported graft copolymer of 4-vinyl pyridine (4VP) with partially carboxymethylated guar gum (Cmg) was synthesized and reaction conditions were optimised using a bromate/thiourea redox pair under an inert atmosphere at 40 °C. Studies have been done to observe the effect of reactants on grafting parameters by varying the reactant concentration. Grafting ratio, add on and conversion show a decrement on increasing the concentration of partially carboxymethylated guar gum beyond 1.0 g dm−3. The grafting parameters increase on increasing the concentration of 4-vinyl pyridine from 13 × 10−2 to 25 × 10−2 mol dm−3, BrO3- from 4 × 10−3 to 10 × 10−3 mol dm−3 and thiourea from 1.6 × 10−3 to 4.8 × 10−3 mol dm−3. Optimum temperature and time for grafting of 4-vinyl pyridine on partially carboxymethylated guar gum are found to be 40 °C and 120 min, respectively. Metal ion uptake and flocculation behaviour have been also studied and found that graft copolymer shows enhancement in these properties than substrate. Swelling behaviour of graft copolymer has been investigated. The graft copolymer is characterized by FTIR and thermal analysis.
... Recently, a new class of flocculating agents based on graft copolymers [12,13] of natural polysaccharides and synthetic polymers such as polyacrylamide (PAM) has been reported. The graft copolymers have also been found to be reasonably shear stable [14] because of the attachment of flexible synthetic polymers onto the rigid polysaccharide backbones. ...
Superabsorbent hydrogels were prepared by grafting copolymerization of cross-linked
polyacrylamide chains onto carboxymethyl cellulose (CMC) via a free radical polymerization
method. These graft copolymers hydrogel were characterized by infrared spectroscopy, thermogravimetric
analysis, and scanning electron microscopy. Hydrogels with different chemical
composition were obtained through variation of grafting polymerization conditions such
as CMC concentration, Acrylamide (AM) concentration, N,N´-methylene bis acrylamide concentration,
Ammonium per Sulphate concentration, reaction time, and reaction temperature.
The impact of hydrogels’ composition on the water uptake capacity was monitored. Maximum
water uptake, 158 g/g, was obtained with graft copolymer of 90% grafting percentage
and 95% grafting efficiency compared to 37 g/g for the native polyacrylamide. Variation of
CMC and AM concentration was found of determined effect. Direct impact of grafting percentage
variation on the water uptake was observed. Sensitivity to pH of the swelling
medium was recognized in both distilled and tap water. Sharp phase transition was recognized
between pH 3.0 and 4.0 in swelling in tap water where this transition was broader in
swelling in distilled water and recognized between pH 3.0 and 7.0. The hydrogel particle size
was found also of determining effect where maximum swelling was observed with particles
size ranged from 500 lm to 1000 lm. Maximum swelling was obtained at 40°C after 4 h
swelling time at both tap and distilled water.
... The graft copolymer solution was subjected for same type of study for biodegradation, and it has been observed that graft copolymer solution showed no loss of viscosity up to 10 days (Fig. 5, Line B). These results show that the graft copolymer is less susceptible to biodegradation and results have also been reported by others (Ungeheur, Bewersdorff, & Singh, 1989). This is in an agreement with the fact that by incorporating relatively inert poly (k-carrageenan-g-N-vinyl-2-pyrrolidone) chains in graft copolymer it can be made less susceptible to bacterial attack (Seaman, 1980). ...
a b s t r a c t In the present article, the graft copolymer of k-carrageenan with N-vinyl-2-pyrrolidone (NVP) has been synthesized using PMS/maleic acid as a redox initiator in aqueous medium and reaction conditions have been optimized to obtain maximum % grafting ratio (%G). The optimum conditions of maximum grafting have been found by varying the different parameters. On increasing the concentration of maleic acid and peroxymonosulphate from 1.6 × 10 −3 to 4.8 × 10 −3 mol dm −3 and 0.6 × 10 −2 to 2.2 × 10 −2 mol dm −3 respectively, the initially grafting parameters increased and after a certain range of concentration graft-ing parameters showed decreasing trend. The small increment of concentration in hydrogen ion causes increment in percentage grafting. It was observed that the grafting parameters increase as the concentra-tion of N-vinyl-2-pyrrolidone increases up to 16 × 10 −2 mol dm −3 after that it decreased. The optimum condition for maximum grafting has obtained at concentration 1.0 g dm −3 of k-carrageenan at 40 • C and 120 min, respectively.
Purpose
This paper aims to study previously prepared and fully characterized chitosan nanoparticles (CNPs) as a starting substrate and microwave initiation technique for grafting acrylic acid (AA). This was done to see the influence of both CNPs with respect to well-dispersed nanosized particles, large surface areas, biodegradability, biocompatibility and reactivity and microwave initiation technique with respect to reduction in organic solvents, toxic chemical initiator and exposer time on exploiting the graft yield % and enhancing water solubility and antibacterial properties.
Design/methodology/approach
For evaluating the best accurate standard metrological method for calculating the graft yield %, the grafting parameters were stated in terms of graft yield percent and measured gravimetrically (based on dry weight method) and titrimetrically (based on carboxyl content). Microwave power, AA and CNPs concentrations and reaction duration were shown to be the most important parameters influencing the grafting process.
Findings
The optimum reaction conditions were obtained when CNPs 1.5 g, AA 150 bows, microwave irradiation power 500 W and reaction duration 120 s were used. Various analytical methods were used to characterize CNPs and poly(AA)–CNPs graft copolymers. According to the findings, Fourier transform infrared spectroscopy examination determines the attachment of carboxyl groups to CNPs chains. The thermogravimetric analysis revealed that the copolymers were more thermally stable than CNPs counterparts. Furthermore, the resulting copolymers were shown to have greater water solubility biodegradability resistance and antibacterial properties than CNPs counterpart. Finally, a preliminary mechanism demonstrating all occasions that occur during the polymerization reaction has been proposed.
Originality/value
The advancement addressed here is undertaken using previously prepared and fully characterized CNPs as a green bio-nanocompatible polymer and microwave initiation technique as green and efficient tool with respect to reduction in organic solvents toxic chemical initiator and exposer time for grafting AA.
Background
Natural polymers are fascinating category of small chain molecules originating for the natural resources, and few examples include Sodium Alginate and Xanthan Gum which are water-soluble in the nature; used for mainly food packaging, biomedical and pharmaceutical applications. In proposed research work, an effort was made to overcome the polymer challenges emerging from the development of polymer blends, as the miscibility between polymers, is a vital aspect.
Objective
This work focuses on the miscibility studies of natural origin polymers. In regards to that, Sodium Alginate/ Xanthan Gum blends were prepared in variable concentrations in aqueous medium and it was utilized for viscosity analysis, FTIR, Ultraviolet spectroscopic studies at variable temperatures.
Methods
It was observed that the developed, Sodium Alginate / Xanthan Gum blends are miscible with each other at most of the temperatures (at 20°C, 40°C and 60°C) considering their viscosity parameters, FTIR and UV spectral data.
Results
Viscosity studies revealed that the miscibility windows of polymeric ratio increases as the temperature increases whereas FTIR spectral patterns exhibited that the composition having 60:40 ratio of polymers exhibits high intensity stretches and represented to be miscible when compared to other combinations.
Conclusion
The present study has reported the simple and efficient method in exploration of the miscibility windows of Sodium alginate and Xanthan gum blend.
Xanthan gum (XG)-based hydrogels containing sodium hydroxide (NaOH) salt were synthesized with the use of distilled water (DW) at room temperature and characterized through FTIR, TGA/DTG, and rheological studies. Sodium hydroxide is used to control pH toward neutral region along with improvement in ionic conductivity and stability of the electrolyte. The stabilized hydrogel has been obtained by applying heat treatment at ambient temperature for 5 wt% XG in 0.015 M solution of NaOH, which exhibits nearly neutral pH value at room temperature. The modification/shifting of the various peaks in FTIR spectra of xanthan gum with the addition of salt indicates the interaction or cross-linking between the constituents (xanthan gum, distilled water, and NaOH) and disappearing of peaks after heat treatment of the gel confirms its stability. DTG and TGA studies have been carried out to investigate thermal stability of these gels and illustrate the effect of heat treatment as a result of salt addition with thermogravimetric analysis up to 400 °C. However, rheological studies were performed for these hydrogels to analyze their viscosity behavior and mechanical stability. Along with the above characterization, gel sample (5 wt% XG in 0.015 M NaOH solution in DW) exhibits high ionic conductivity of 4.71 × 10−3 S/cm with 6.45 pH value at room temperature after heat treatment. These highly ion conducting, thermally and mechanically stable biodegradable xanthan gum-based hydrogels can also be used as an electrolyte for various device applications like supercapacitors, fuel cells, solar cells, etc.
Electrospinning and electrospraying are versatile techniques for the production of nano- to micro-scale fibers and particles. Over the past 2 decades, significant progresses have been made to advance the fundamental understandings of these electrohydrodynamic processes. Researchers have investigated different polymeric and non-polymeric substrates for producing submicron electrospun/electrosprayed materials of unique morphologies and physicochemical properties. This chapter provides an overview on the basic principles of electrospinning and electrospraying, highlighting the effects of key processing and solution parameters. Electrohydrodynamic phenomena of edible substrates, including polysaccharides (xanthan, alginate, starch, cyclodextrin, pullulan, dextran, modified celluloses, and chitosan), proteins (zein, what gluten, whey protein, soy protein, gelatin, etc.), and phospholipids are reviewed. Selected examples are presented on how ultrafine fibers and particles derived from these substrates are being exploited for food and nutraceutical applications. Finally, the challenges and opportunities of the electrostatic methods are discussed.
The specific features of synthesis, structure in the block, and behaviour in solution and a number of functional properties of graft copolymers with chemically complementary polymeric components are considered. The influence of the system of intramolecular bonds between the backbone and grafted chains and between the neighbouring grafted chains on the polymer properties is analysed. It is shown that these graft polymers refer to a special class of polymers, intramolecular complexes.
The main objective of this research work is to synthesize crosslinked hydrogel from xanthan gum and acrylamide under the influence of microwave radiations by graft polymerization technique in presence of potassium persulphate-N,N'-methylene-bis-acrylamide as initiator-crosslinker system. Different reaction parameters such as reaction time, pH, solvent and initiator concentration were optimized a function of percentage grafting. Monomer and cross-linker concentrations were optimized as a function of percentage swelling for getting the polymer with maximum water absorption capacity. The superabsorbent was characterized using different characterization techniques like, FTIR, TGA / DTA / TDG and X-ray diffraction. The candidate polymer was found to be thermally more stable than the xanthan gum.
Synthetic Polyacrylamide based polymers and polysaccharides such as guar gum, xanthan gum carboxymethylcellulose and starch have been used for long. The Polyacrylamides are easily amenable to shear degradation although they are very efficient drag reducing and flocculating agents even at low ppm concentrations. On the other hand polysaccharides are fairly shear stable but are not very efficient drag reducers and flocculants. Their aqueous solution are also subjected to rapid biodegradation. It was contemplated that in the case where Polyacrylamide chains are grafted on polysaccharide backbones, efficient shear and biodegradation drag reducing and flocculating agents may be developed.
Water soluble polysaccharides have myriad of industrial and agricultural applications as flocculants, drag reducers, viscosity controllers, controlled drug delivery agents, adsorbent polymers, stabilizers, water-borne polymer coatings, dispersants, etc. Among various water soluble polysaccharides, guar gum (GG) is one of the most important polysaccharides. It is being used in a wide variety of applications. It has been established in the authors' laboratory that the performance is enhanced considerably on purification, grafting by polyacrylamide (PAM), and subsequent hydrolysis and canonization. The most significant performance is enhanced in flocculation where it has been found that the modified guar gum outperforms several existing flocculants in national and international markets. Similar effects are observed in the performance in rheology. The present chapter outlines the development of modified guar gum and applications of these modified and unmodified guar gums in the fields of flocculation, drag reduction, and rheology.
Although existing since the concept of macromolecules, polymer mechanochemistry is a burgeoning field which attracts great scientific interest in its ability to bias conventional reaction pathways and its potential to fabricate mechanoresponsive materials. We review here the effect of topology on the mechanical degradation of polymer chains and the activation of mechanophores in polymer backbones. The chapter focuses on both experimental and theoretical work carried out in the past 70 years. After a general introduction (Sect. 1), where the concept, the history, and the application of polymer mechanochemistry are briefly described, flow fields to study polymer mechanochemistry are discussed (Sect. 2), results of mechanochemistry study are presented for linear polymers (Sect. 3), cyclic polymers (Sect. 4), graft polymers (Sect. 5), star-shaped polymers (Sect. 6), hyperbranched polymers and dendrimers (Sect. 7), and systems with dynamic topology (Sect. 8). Here we focus on (1) experimental results involving the topological effect on the coil-to-stretch transition and the fracture of the polymer chains, (2) the underlying mechanisms and the key factor that determines the mechanical stability of the macromolecules, (3) theoretical models that relate to the experimental observations, and (4) rational design of mechanophores in complex topology to achieve multiple activations according to the existing results observed in chain degradation.
Star copolymers of acrylamide (AM) and N,N-dimethyl-Nvinylnonadecan- 1- aminium chloride (C18DMAAC) were synthesized by photopolymerization in water. Some properties of these star hydrophobically modified acrylamide copolymers (SHMPAM) with different C18DMAAC contents and the linear hydrophobically modified acrylamide copolymers (LHMPAM) in brine were characterized. The increase in C18DMAAC content resulted in decreased intrinsic viscosity and increased Huggins constant for SHMPAM. Similar results were observed for LHMPAM. With similar intrinsic viscosity and C18DMAAC content, the Huggins constant of SHMPAM was much higher than that of LHMPAM, which might be due to the fact that SHMPAM had much stronger intramolecular interaction in dilute polymer solutions. In semi-dilute solutions, the apparent viscosity of SHMPAM was increased with increasing C18DMAAC content, which was similar to that of LHMPAM. However SHMPAM exhibited higher apparent viscosity than LHMPAM because it had more arms and thus had more chances to form three-dimensional networks in semi-dilute solutions. In the flowinduced scission experiment, SHMPAM exhibited superior shear stability in comparison with LHMPAM. When the extensional shear rate was ≈ 40000 s-1, the reduction ratios of the apparent viscosities of the four SHMPAMs after the scission were about 80%. In contrast, when the extensional shear rate was ≈20000 s-1, the reduction ratio of the apparent viscosity of LHMPAM-0.40 had already reached around 80%.
Star copolymers of acrylamide and N,N-dimethyl-N-vinylnonadecan-1-aminium chloride (C18DMAAC) were synthesized by photopolymerization in water. Solution behaviors of these star hydrophobically modified acrylamide copolymers (SHMPAMs) with different C18DMAAC contents and the linear hydrophobically modified acrylamide copolymers (LHMPAMs) were characterized. The increase in C18DMAAC content resulted in decreased intrinsic viscosity and increased the Huggins constant for SHMPAMs. Similar results were observed for LHMPAMs. With similar intrinsic viscosity and C18DMAAC content, the Huggins constant of SHMPAMs was much higher than that of LHMPAMs, which could be due to the fact that SHMPAMs had much stronger intramolecular interaction in dilute polymer solutions. In semi-dilute solutions, the apparent viscosity of SHMPAMs was increased with increasing C18DMAAC content, which was similar to that of LHMPAMs. However, SHMPAMs exhibited higher apparent viscosity than LHMPAMs because it had more arms and thus had more chances to form three-dimensional networks in semi-dilute solutions. In the flow-induced scission experiment, SHMPAMs exhibited superior shear stability in comparison with LHMPAMs. When the strain rate was ≈40,000 s-1, the reduction ratios of the apparent viscosities of the four SHMPAMs after the scission were approximately 80%. By contrast, when the strain rate was ≈20,000 s-1, the reduction ratio of the apparent viscosity of LHMPAM-0.40 had already reached around 80%.
An experimental study of the flow-induced scission behaviour of four star hydrolyzed polyacrylamides (HPMA) with different arms during planar elongational flow in a cross-slot flow cell is described. The results showed that the shear stability of linear HPAM in distilled water was not essentially different from star HPAM. Polymer scission was not observed in either system in a shear rate range from 20,000 to 100,000s-1, which can be attributed to the strong polyelectrolyte behaviour of HPAM in distilled water. However, at the same shear rate, the star HPAMs exhibited superior shear stability in comparison to the linear HPAMs in aqueous solutions containing NaCl (CNaCl=0.2-1.0%wt) and, in particular, the initial reduction rate of relative viscosity (R) decreased with the degree of branching of the HPAMs. In addition, it was found that the R of five HPAMs in NaCl aqueous solutions exhibited an exponential dependence on shear rate, in which the coefficient C1 can be used to quantitatively evaluate shear stability. In star HPAM NaCl aqueous solutions, the increase of R with shear rate is very likely due to the decrease of the hydrodynamic radius (Rh) of these HPAMs, while the increase of R with NaCl concentrations can be attributed to the relatively low viscosity of these polymers at high NaCl concentrations.
Using amylopectin (AP) and a derivative, we systematically investigated their turbulent drag reduction characteristics and shear stability. The expected shear stability of polysaccharides as drag reducing and flocculating agents triggered our study on structural modification of AP. For this purpose, we prepared a derivative of AP, viz. AP grafted with polyacrylamide (GA), in which the granular form of AP powder (≈10 μm) changed into a mixture of larger fibrils and lumps. Using a rotating-disk apparatus, we measured the shaft torque and calculated the turbulent drag reduction (DR) efficiency under various experimental conditions, i.e., different polymer concentration, rotation speed, and temperature. Contrary to AP, GA showed relatively high DR efficiencies (27%) and very strong shear resistance.
The synthesis of graft copolymer (κ-carrageenan-g-vinylsulfonic acid) is carried out in nitrogen atmosphere using potassium peroxymonosulfate (PMS) and malonic acid (MA) as redox system. The effect of reaction variables including the concentration of vinylsulfonic acid 1.3×10(-2) to 6.7×10(-2) mol dm(-3), PMS 4×10(-3) to 20×10(-3) mol dm(-3), MA 1.6×10(-3) to 4.8×10(-3) mol dm(-3), sulfuric acid 1×10(-3) to 8×10(-3) mol dm(-3), κ-carrageenan 0.4-1.8 g dm(-3) as well as time duration 60-180 min and temperature 25-45 °C has been studied. The water swelling capacity of graft copolymer is investigated. Flocculation property for both coking and non-coking coals is studied for the treatment of coal mine waste water. The graft copolymer has been characterized by FTIR and thermogravimetric analysis.
The viscoelasticity and thermal properties of aqueous
solutions of blended xanthan gum (XA) with chitosan were investigated in order
to study the electrostatic interaction established between two polysaccharides.
Storage modulus G’, loss modulus G” and zero shear rate viscosity ηO
attain a maximum at a chitosan concentration C
max.
The above results indicate that the junction between XA and chitosan is formed
in a concentration range lower than C
max
and the viscoelasticity of systems increases with increasing concentration.
In a concentration range higher than C
max,
junction formation may not occur effectively since the excess amount of chitosan
completely screens anions of XA. The chain rigidity of XA decreases by the
screening of the repulsive interaction between anions on XA chains. The ineffective
junction formation and the decrease of XA chain rigidity may cause the decrease
of viscoelasticity of systems with increasing concentration. The value of C
max decreases with increasing
molecular mass of chitosan. From melting enthalpy of the above system measured
by DSC, the amount of non-freezing water (W
nf)
was evaluated. W
nf
shows a minimum at the concentration C
max.
This fact suggests that hydrophobic fields increased by junction structure
formation through ion-complexation between XA and chitosan molecules.
In recent literature relating to drag reduction by polymeric additives, it has been purported that grafting side chains is a way of enhancing their shear stability. A careful analysis of the experimental reports shows that grafting in fact reduces the shear stability of long-chain polymers. A simple mechanistic analysis of the fracture of an ideal grafted chain molecule has been performed to support this finding. Some guidelines for the design of stable and effective drag reducing macromolecules are proposed.
The aim of the paper is to study the physico-chemical phenomenon of synthesized graft copolymer (carboxymethylated guar gum-g-vinylsulfonic acid). The reaction optimum conditions for grafting has also been determined by studying the effect of vinylsulfonic acid, hydrogen ion, peroxymonosulphate, glycolic acid concentration and carboxymethylated guar gum along with time and temperature. Experimental results show that maximum grafting has been obtained at 1.8gdm(-3) concentration of partially carboxymethylated guar gum and 5.3×10(-2)moldm(-3) concentration of vinylsulfonic acid. It has been observed that grafting ratio, add on, conversion, efficiency increase up to 4.0×10(-3)moldm(-3) of hydrogen ion, 4×10(-3)moldm(-3) of glycolic acid, 14×10(-3)moldm(-3) of peroxymonosulphate and 35°C of temperature. Grafted copolymer has been characterized by FTIR spectroscopy and thermogravimetric analysis. Water swelling, flocculating, metal ion uptake and resistance to biodegradability properties of partially carboxymethylated guar gum-g-vinylsulfonic acid have been determined.
Using the method of Brownian dynamics simulations, we have analyzed chain conformations and the presence of chain overlaps and entanglements in dilute polymer solutions. The results show that polymer + polymer interactions exist in static dilute solutions as well as in solutions under shear flow. The effect of solution concentration and the shear rate is examined. The fundamental problem of existence of chain overlaps in dilute solutions is related to the drag reduction phenomenon and is discussed.
Polysaccharides are abundantly available from farm, forest, and microbial resources. They are used in myriad applications. It has been established in the authors' laboratory that their performance is enhanced considerably on purification, grafting by polyacrylamide (PAM), and subsequent hydrolysis as well as cationization. The most significant performance is enhanced in flocculation where it has been found that the modified polysaccharides outperform existing flocculants in national and international markets. Similar effects are observed in their performance in turbulent drag reduction (DR), percolation, and rheology. The present article outlines the details of materials, mechanisms, and practical applications of these novel materials.
The existence and temperature stability of the hydrogen bond system in triblock copolymers based on chemically complementary polyacrylamide and poly(ethylene oxide) are studied. The participation of the trans-multimers of PAA amide groups and oxygen atoms of PEO in the formation of hydrogen bonds between both polymer blocks is established. It is shown that the hydrogen bond system in the copolymers is stable enough in the wide temperature region T = (308 ÷ 473) K. The insignificant destruction of the H-bonds between PAA and PEO blocks and also the cis-trans- and trans-multimers of amide groups in the triblock copolymers is revealed at the temperature increasing.
A device has been specifically designed to measure the hydrodynamic friction of special coatings under turbulent flow conditions; it consists of two concentric cylinders, the outer one of which rotates. A lineat velocity of 4·7 m s−1 can be attained for the coating and drag reductions as small as 1% may be measured. The system includes on-line experimental data acquisition and processing facilities which provide rapid and accurate assessment of a large number of tests conducted over widely varying time periods.
The waste water and industrial effluent-treatment requires both inorganic and organic flocculants. Among the organic type, polymeric flocculants (synthetic as well as natural) are preferred because of their low dosage, easy handling, inertness to pH changes, production of large cohesive flocs and versatile tailorability. The concern for environmental and ecological issues warrants the use of the biodegradable flocculant in waste water and industrial effluent treatments. Natural polysaccharides such as starch, gums, glues, alginate, etc. function as bridging flocculants. This could be accounted for by the purification and chemical modification. It has been established that by grafting polyacrylamide branches on polysaccharides, the dangling grafted chains have easy approachability to the contaminants. Among the grafted guar gum, xanthan gum, carboxy methyl cellulose and starch, grafted starch flocculates better. Starch consists of amylose (a low molecular weight linear polymer) and amylopectin (a high molecular weight, branched polymer). The grafted amylopectin is found to be a suitable flocculant for various kinds of industrial effluents. Here we summarize the various investigations carried out using flocculants based on polysaccharides.
The primary objective of this work was to prepare star copolymers of acrylamide and N,N-dimethyl-N-vinylnonadecan-1-aminium chloride(C18DMAAC) and to investigate the dilute solution behavior of these star hydrophobically modified acrylamide (SHMPAM) copolymers with different C18DMAAC content. The SHMPAMs were prepared using photopolymerization. For the different polymer solutions, the relationship between specific viscosity and polymer concentration obeyed the Rabin's relation well, which means that the conformations of these polymer chains were nearly spherical in dilute solution. The data of these dilute solutions were fitted by four different equations. The results showed that Schulz–Blaschke(S–B) and Fedors equations more accuratly described the dilute solution properties of these kinds of copolymers. The intrinsic viscosities calculated by different equations were different from each other, which is different from the results found for linear HMPAM. The equivalent hydrodynamic volume (voluminosity VE ) of these star copolymer solutions can not calculated by the regular method because the relationship between Y (Y = (ηr 0.5−1)/C (1.35ηr 0.5−0.1), ηr is relative viscosity and C is polymer concentration) and polymer concentration was abnormal.
a b s t r a c t The present paper reports the graft copolymerization of vinyl sulfonic acid onto sodium carboxymethyl cellulose by free radical polymerization using potassium peroxydiphosphate/thiourea redox system in an inert atmosphere. The reaction conditions for maximum grafting have been optimized by varying the concentration of vinyl sulfonic acid (2.6 Â 10 À2 –8.0 Â 10 À2 mol dm À3), potassium peroxydiphosphate (4.0 Â 10 À2 –20 Â 10 À2 mol dm À3), thiourea (0.8 Â 10 À3 –4.0 Â 10 À3 mol dm À3), sulphuric acid (1.0 Â 10 À3 –6 Â 10 À3 mol dm À3), sodium carboxymethyl cellulose (0.6–1.6 g dm À3) along with time duration (60–180 min) and temperature (30–50 °C). Water swelling capacity, metal ion sorption, flocculation stud-ies and resistance to biodegradability of synthesized graft copolymer have been performed with respect to the parent polymer. The graft copolymer has been characterized by FTIR spectroscopy and thermo-gravimetric analysis.
Linear high molecular weight polymers undergo central scission in strong flows due to buildup of stress from fluid drag. An alternative to linear architecture is the star branched polymer that shows higher shear stability against such scission. We consider two six-arm star polymers differing in the connectivity of the arms at the core. The first is a fused-core star PMMA, where the arms are interconnected at a triphenylene core, with the multiple bonds therein supporting one another against possible tensile fracture. The second is a linear-core star PMMA, containing linearly linked single bonds within the core as potential fracture sites under tensile stress. Their stress-induced scission tendency is analyzed during planar elongational flow of their dilute solutions in dibutyl phthalate in a cross-slot flow cell. We find that scission of the star PMMA at the arms dominates their degradation behavior, and both the linear-core and fused-core star PMMAs show similar flow-induced scission. These results are analyzed first in terms of the critical-stress-to-fracture (CSF) and then in terms of scission kinetics as described by the thermally activated barrier to scission (TABS). The experimentally observed scission kinetics of the arms can be represented by the TABS model, but a description of the core scission appears to demand consideration of several possible conformations of the branched polymers.
a b s t r a c t The present paper reports the modification of alginate through the grafting of 2-acrylamidoglycolic acid by free radical polymerization using an efficient potassium peroxydiphosphate/silver nitrate redox system in an inert atmosphere. The reaction conditions for maximum grafting have been opti-mized by varying the reaction variables including the concentration of 2-acrylamidoglycolic acid (2.0 × 10 −2 –7.3 × 10 −2 mol dm −3), potassium peroxydiphosphate (0.4 × 10 −2 –2.0 × 10 −2 mol dm −3), sil-ver nitrate (1.2 × 10 −3 –4.4 × 10 −3 mol dm −3), sulphuric acid (1.0 × 10 −3 –8 × 10 −3 mol dm −3), alginate (0.4–1.8 g dm −3) along with time duration (60–180 min) and temperature (30–50 • C). Water swelling capacity, metal ion sorption, flocculation and resistance to biodegradability studies of synthesized graft copolymer have been performed with respect to the parent polymer. The graft copolymer has been characterized by Fourier transform infrared spectroscopy and thermogravimetric analysis.
a b s t r a c t Graft copolymer of xanthan gum and 2-Acrylamidoglycolic acid has been synthesized by free radical polymerization using bromate/thiourea redox pair in an inert atmosphere. The grafting parameters, i.e. grafting ratio, add on and efficiency decrease with increase in concentration of xanthan gum from 1.0 g dm −3 and hydrogen ion from 5 × 10 −3 mol dm −3 , but these grafting parameters increase with increase in concentration of 2-Acrylamidoglycolic acid from 2.6 × 10 −2 to 8.0 × 10 −2 mol dm −3 , and bro-mate 6 × 10 −3 to 14 × 10 −3 mol dm −3 . Water swelling capacity, metal ion sorption, flocculation studies and resistance to biodegradation of synthesized graft copolymer has been performed with respect to the parent polymer. The graft copolymer has been characterized by infrared (IR) spectroscopy and thermo-gravimetric analysis.
In this article, the synthesis of j-carrageenan-g-methacrylic acid has been reported by free radical poly-merization initiated by Potassium peroxymonosulphate/ glycolic acid redox pair under nitrogen atmosphere. The reaction conditions have been optimized by varying the reac-tion conditions, including the concentration of monomer, peroxymonosulphate, glycolic acid, sulphuric acid, j-carra-geenan along with reaction time and temperature. It has been observed that the maximum yield has been obtained at time 120 min, temperature 40 C, at 20 Â 10 À2 mol dm À3 con-centration of methacrylic acid, 1.0 g dm À3 concentration of j-carrageenan and 16 Â 10 À3 mol dm À3 concentration of per-oxymonosulphate. The graft copolymer is characterized by Forier Transform Infrared Spectroscopy and Thermal analy-sis. Water swelling capacity of graft copolymer has been determined. Intrinsic viscosity has been obtained for both grafted and ungrafted j-carrageenan. Metal ion sorption and flocculation performance of synthesized graft copolymer has been studied with respect to the ungrafted substrate. V
Water is scarce commodity now. Recycling of municipal wastewater, industrial and mineral processing effluents require treatment with the inorganic or organic flocculants. Both synthetic and natural polymers are used as flocculants. Natural polymers are biodegradable and are effective at very large dosages but are very shear stable. The synthetic polymers are highly effective flocculants at very small dosages and have high tailorability, but have poor shear stability. In the authors' laboratory, a novel polymeric flocculant has been developed by grafting polyacrylamide onto the backbone of carboxymethyl tamarind (CMT-g-PAM). Various grades were developed to optimize the best flocculant. The grafted polymers were characterized by various characterization techniques such as intrinsic viscosity measurement, FTIR spectroscopy, 13C-NMR spectroscopy, elemental analysis etc. The flocculation studies were carried out using turbidity test as well as settling test. The optimized CMT-g-PAM was then compared with some of the commercial flocculants available in national and international markets in colloidal suspensions and it has been found that our synthesized flocculant surpasses most of the commercial flocculants in performance.
Graft copolymers of polyacrylamide with starch, amylose, and amylopectin have been synthesized using ceric-ion-induced redox initiation technique. The polymers were characterized using different instrumental techniques like thermal, XRD, SEM, IR, NMR, and elemental analysis. The results indicated that there is a substantial amount of grafting with minimum formation of homopolyacrylamide. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1795–1810, 1998
Dilute solutions of many polysaccharides have lower frictional resistance in pipe flow than pure water. As yet unexplained, this effect may have important industrial ramifications.
This state of-the-art review is published in two parts: Part 1 has already appeared and deals with basic aspects of the subject, while this part sets out details of specific drag reduction applications. These include oil pipelines, oil well fracturing, sewers, open channels, hydropower penstocks and culverts, the hydrotransport of pulverised solids, the effect of drag reducing additives on fluid machinery, marine applications, their use in heating systems, firefighting and jet cutting. The preparation and injection of polymer solutions, the economics of their use, their degradation in flow and the pollution implications of their release into water courses are aslo covered. Wherever possible field test results are included and discussed. The bibliography contains 154 references to published material.
Data are presented which show that highly viscous, pseudoplastic, and viscoelastic solutions can be made from low molecular weight polymers by designing polymers with high radii of gyration. Solutions of starch-acrylamide, graft copolymers, one type of high radius, low molecular weight polymer, have relaxation times which increase with increasing copolymer concentration, increasing copolymer molecular weight, or, at constant molecular weight, decreasing number of grafts per starch molecule. Intrinsic viscosity, radius of gyration, and filtration data show the graft copolymers to be 1 to 6 times larger molecules than equal molecular weight polyacrylamide. Solution rheology changes slowly with time for two months after solution preparation. Viscosity loss, reduction in pseudoplasticity, and reduction in viscoelasticity are all due to disentangling of polymer chains. All copolymers were prepared by redox initiated, free radical polymerization of acrylamide on starch.
The oxidation of pinacol (2,3-dimethylbutandiol-2,3) by ceric sulfate was studied at 25°. The reaction is first order with respect to ceric ion and pinacol. No evidence of complexing between the sulfatocerate species and the glycol was found. The data show that one molecule of acetone is formed per ceric ion consumed. In the presence of acrylamide one molecule of acetone is formed per two ceric ions consumed. To explain the data a mechanism is proposed whereby the primary radicals are captured by the acrylamide, the efficiency of capture being of the order of 100%, and the polymer radicals are terminated by ceric ion. The data also show that the carbon-to-carbon bond of the 1,2-glycol is split before the free radical is captured. The activation energy for the over-all reaction was found to be 22.5 kcal./mole.
Model graft copolymers were synthesized by grafting acrylamide onto dextran (Mw = 500,000) utilizing an initiation method in which a Ce(IV)/HNO3 solution was added to the dextran solution in order to allow coplexation prior to monomer addition. Three synthetic reaction parameters were optimized on the basis of conversion and solution viscosity: monomer concentration, dextran concentration, and nitric acid concentration. Molar ratios of [Ce(IV)]/[dextran] were changed systematically to affect the number and length of the acrylamide grafts. The number of grafting sites and graft chain lengths, determined by selective hydrolysis of the carbohydrate backbone, were in good agreement with those theortically predicted from knowledge of initiation efficiency and monomer conversion. Rheological studies of the model graft copolymers were conducted in aqueous solutions as a function of temperature, added salt, and copolymer concentration.
The mechanical shear degradation of polydisperse polyisobutene and monodisperse polystrene in oils of different viscosities in the concentration range of 0.1% to 1% was studied using a high-shear concentric cylinder viscometer under laminar and uniform well-defined shear field conditions. Molecular weight distributions (MWDs) were measured by gel permeation chromatography (GPC). Degradation of polydisperse polyisobutene solutions narrows the distributions principally through the breaking down of large molecules. Degradation of monodisperse polystyrene broadens the distributions at lower shear stress. At higher shear stresses, the distributions do not broaden as much but are still broader than those of the original polymer. The final Mw/Mn ratios are considerably different from the value of 2 expected for random degradation. Hence, the degradation is likely a nonrandom process. It was found that the extent of degradation has a negative concentration dependence coefficient at relatively high molecular weight and a positive concentration dependence at lower molecular weight. Competing mechanisms of “stretching” and “entanglements” for degradation were postulated to explain the results. The degradation data indicate that the shear stress is the controlling parameter, not the shear rate. The shear degradation is independent of initial molecular weight and viscosity of the solvent.
Commercial guargum is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum start degrading within 8 hrs. of their preparation and after 65 hrs., they degrade completely. In the present investigation, the graft copolymers of guargum and polyacrylamide have been prepared. It has been shown that the purification and grafting enhance the drag reduction effectiveness and biodegradation resistance considerably in guargum.
Graft copolymers of xanthangum and polyacrylamide have been prepared by grafting acrylamide onto xanthangum using ceric-ion-initiated solution polymerization technique. These graft copolymers have been tested for their drag reduction effectiveness, shear stability, and biodegradability. It has been shown that the grafting enhances the drag reduction effectiveness and biodegradation resistance of xanthangum considerably.
Guargum is a seed galactomannan and is known to be a shear stable drag reducing agent. However, the aqueous solutions of guargum are very susceptible to microbial degradation. In the present investigation, seven graft copolymers of guargum and polyacrylamide have been synthesized and their drag reduction effectiveness, shear stability, and biodegradation resistance have been determined. It has been shown that the drag reduction effectiveness and shear stability of the graft copolymer depend upon the length of the graft and number of grafts in the molecule. None of the graft copolymer solutions show any microbial degradation up to 10 days.
Drag reduction by dilute solutions of linear, random-coiling macromolecules in turbulent pipe flow is reviewed. The experimental evidence is emphasized in three sections concerned with the graphical display of established features of the phenomenon, data correlation and analysis, and the physical mechanism of drag reduction.
The recently developed elongational flow technique is applied to the examination of flow-induced chain rupture of macromolecules in solution. For both closely monodisperse atactic polystyrene (a-PS) and poly(ethylene oxide) (PEO), the critical strain rate for extension () is found to depend upon molecular weight M as , consistent with ideal Zimm dynamics. When the chains are subjected to strain rates beyond the scission products correspond closely to one-half of the initial molecular weight. The critical fracture stress depends upon molecular weight as , enabling the prediction of the ultimate chain length which can be extended without fracture (). For a-PS this corresponds to M = 3 × 107. These findings are well accounted for by Stokes' Law applied to an extended bead–rod model. The calculated flow-induced force in the chain corresponds closely to the rupture force of a covalent backbone bond calculated from a modified Arrhenius rate equation. During the prefracture stage () a-PS shows anomalies in the flow-induced birefringence, which suggest that the Phenyl side groups are becoming reoriented due to the progressive increase in free volume as the chemical backbone bonds stretch and the bond angles open.
A list of conclusions from experimental studies of drag reduction (DR) and mechanucal degradation in flow (MDF) is made. A statistical-mechanical model of chain conformations developed by the author9 is used, and its consequences for DR and MDF established. Experimental findings are explained in terms of the model, including those considered to be puzzling and contrary to expectations. A relation between the extent of mechanical degradation and flow time is derived. The equation obtained for relative drag reduction in function of time reproduces perfectly the experimental data for polystyrene+toluene solutions reported by Hunston and Zakin12. Some predictions from the present model have yet to be tested experimentally.