D.W. Van Krevelen's research while affiliated with Central Food Technological Research Institute and other places
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Publications (63)
A dimensionless equation has been derived for the mass transfer coefficient in the liquid phase (k 1 ) both for physical and chemical absorption.
The equation can be written:
where the dimensionless groups ² ) have the following significance:
When the absorption is purely physical the group Ha has the value of 1. The equation is checked with the...
Various methods of polymerising ethylene are described in the literature. Ethylene as such or in a liquid medium is polymerised with an aluminum chloride catalyst; the yield of lubricating oil fractions obtained by these known methods is relatively low, further they have a low viscosity index (Dean and Davis). The high molecular fractions are rathe...
A modified Sherwood‐Gilliland equation for mass transfer in the gas phase is applied to gas absorption in scrubbers. The equation can be written in the following dimensionless form:
where the dimensionless groups have the following significance
The equation is checked on the available data in the literature and on experiments by the authors.
The...
Gas absorption with simultaneous chemical reaction can be divided into three characteristic groups.
For the very slow reactions the rate‐determining step is the diffusion of the solute gas through the liquid film.
Chemical reaction velocity is determinative for moderately rapid and slow reactions.
For the very fast reactions gas film resistance to...
Rate of mass transfer in granular beds has been studied by determining the rate of dissolution of benzoic acid in water and aqueous glycerol solutions and of sulphur in benzene. For liquid-continuous flow and film-like flow, mass transfer coefficients could be correlated by dimensionless equations
The results of the theoretical considerations described in Part I are applied to experiments on chemical absorption of carbon dioxide in alkali hydroxide solutions and in ammoniacal solutions.
The calculated values for the rate of absorption prove to be in good agreement with the experimental data.
When a gaseous component is absorbed by a liquid under simultaneous reaction with a component of the liquid, the overall rate of reaction proves to be a dimensionless function of four limiting rates:
the maximum rate of diffusion of the gaseous component through the liquid film
the maximum rate of diffusion of the liquid‐component through the liqui...
The general equation for liquid film resistance to gas absorption in scrubbers, derived by us in a previous paper 1), was applied to experiments of Cryder and Maloney2), treating the absorption of carbon dioxide in diethanolamine solutions. Our equation proved to be valid also in this case, when it is assumed that the reaction is a pseudo-third ord...
The stablest intermediate product formed in the oxidation of cyclohexanol and cyclohexanone is 6-hydroxyimino-6-nitro hexanoic acid (nitrolic acid). In the temperature range investigated it yields over 90% of adipic acid and N2O. In addition, a small amount of a still unidentified by-product is formed at low temperatures; upon heating, the latter g...
Measurements of mass transfer coefficients in film reactors are reported.
Turbulence due to entrance effects is shown to explain why mass transfer coefficients in the gas film may be proportional to the 0.8th power of mass velocity even, within the region where streamline flow is normal. It is shown that the velocity profile of gas flow is complete...
Vapour pressures of aqueous solutions containing ammonia and carbon dioxide, ammonia and hydrogen sulphide or ammonia, carbon dioxide and hydrogen sulphide, have been determined at temperatures from 20‐60° C. Dissolved hydrogen sulphide is present almost completely in the form of ammonium hydrosulphide. Dissolved carbon dioxide is present in the fo...
The solubilities of some aromatic hydrocarbons in pyridine have been measured. The entropies of fusion derived from these measurements agree qualitatively with the values which can be calculated, if it is assumed that their molecules obtain one rotational and three translational degrees of freedom when melting occurs.
The rate of dissolution of benzoic acid granules in alcaline aqueous solutions has been studied. A formula of the kinetics of this chemical dissolution process has been derived. Mass transfer coefficients for film-like flow of the dissolving agent can be correlated by the same dimensionless equation as in the physical dissolution process.
The oxidation of cyclohexanol with nitric acid to adipic acid proceeds via two stable intermediates known from the literature1 viz. 6-hydroxyimino-6-nitro hexanoic acid and the hemihydrate of 1,2-cyclohexanedione, two substances forming beside each other in a given ratio. This ratio can be calculated as a function, of the temperature and of the nit...
Equations for the absorption rate coefficient and the efficiency of absorption are derived.
A graph is given by which the application of these relationships is considerably simplified.
The mechanical properties of polymers are of interest in all applications where polymers are used as structural materials. Mechanical behavior involves the deformation of a material under the influence of applied forces. The simplest mechanical properties are those of homogeneous isotropic and purely elastic materials; their mechanical response can...
This chapter discusses the densimetric and volumetric properties of polymers, especially density and its variations as a function of temperature and pressure. Density is defined as the ratio of mass to volume. This chapter begins with a description of fundamental quantities of mass and volume. Under this, it considers the molar mass of polymeric st...
This chapter deals with the thermochemical properties of polymers. It demonstrates that the free enthalpy of reactions can be calculated by means of additive group contributions. It begins with a description of thermodynamics and kinetics, explaining that thermodynamic potentials constitute the driving forces causing every natural process to procee...
The crystallization of polymers depends on the possibilities of nucleation and growth. The structural regularity of the polymer has a profound influence on both. Interesting correlations have been found for estimating the rate of spherulitic crystallization. Besides this normal mode of bulk crystallization, other modes are frequently observed such...
A polymer may be degraded by chemical changes due to reaction with components in the environment. The most important of these degrading reagents is oxygen. Oxidation may be induced and accelerated by radiation (photo-oxidation) or by thermal energy (thermal oxidation). Besides the oxidative degradation, also other forms of chemical degradation play...
This chapter deals with the calorimetric properties of polymers. The following properties belong to the calorimetric category: specific and molar heat capacities, latent heats of crystallization, or fusion. The specific heat capacity is the heat that must be added per kg of a substance to raise the temperature by one Kelvin or one degree Celsius. T...
Textile articles are more or less unique by the wide and varied range of product properties which prove to be important. This chapter describes the properties of textile articles. It begins with a description of aesthetic properties of articles, which includes properties that determine the reactions (perceptions) of the senses: the eye (color, lust...
This chapter deals with the electrical properties of polymers. The common polymers are all dielectrics. The properties of such polymers are usually assessed from the behavior of the polymer at low electric field strengths (first group of properties). To this group belong the dielectric constant, the dissipation factor, the static electrification, a...
This chapter discusses the diffusive mass transfer, as observed in practical applications of polymeric systems, which is divided into three categories. The first category considers the permeation of simple gases through thin layers of polymers, such as occurs in protective coatings and in packaging films. This category is the most widely studied; f...
This chapter deals with the acoustic properties of solid polymers, which are important, both from a theoretical and from a practical point of view. Acoustic measurements can be used as structural probes, since the acoustic properties, especially sound absorption, are related to many structural factors, such as transition temperatures, morphology, c...
Surface energy is a direct manifestation of intermolecular forces. The molecules at the surface of a liquid or a solid are influenced by unbalanced molecular forces and therefore possess additional energy, in contrast with the molecules inside the liquid or solid. The specific free surface energy of a material is the excess energy per unit area due...
Polymers consist of identical constitutional repeating units, which are structural units also called monomers. This chapter considers the main aspects of polymer typology, viz., the chemical structure, the molecular weight distribution (MWD), the phase transition temperatures, the morphology, and the relaxation phenomena. Furthermore, the chapter p...
This chapter deals with the cohesive energy and the solubility parameter, and explains the correlation of these quantities with chemical structure. The cohesive properties of a polymer find direct expression in its solubility in organic liquids. The cohesive properties of a substance are expressed quantitatively in the cohesive energy. This quantit...
This chapter deals with the environmental behavior and failure of product properties with respect to polymers. The properties that determine the environmental behavior of polymers after processing into final products may be divided into three categories—the thermal end use properties, the flammability, and the properties determining the resistance...
This chapter deals with the optical properties of polymers. It discusses light refraction, light reflection, birefringence, light scattering, and differential light absorption. The interaction of electromagnetic radiation (light) with matter is controlled by three properties—the specific conductivity, the electric inductive capacity or electric per...
The rheology of polymer solutions is important in several stages of the manufacturing and processing of polymers, such as in the spinning of fibers and the casting of films from solutions, and especially in the paints and coatings industry. The rheology of a polymer solution increases with the polymer concentration. A transition exists at the so-ca...
This chapter demonstrates that the two main transition temperatures, viz. the glass–rubber transition temperature and the crystalline melting temperature, can be correlated with the chemical structure by means of a method based on group contributions. It begins with a description of the additive molar function for the calculation of the glass trans...
The flow behavior of polymer melts is of great practical importance in polymer manufacturing and polymer processing. Therefore, the development of a quantitative description of flow phenomena based on a number of material properties and process parameters is highly desirable. In the same way as the mechanical behavior of solid polymers is described...
Product or article properties (also called end-use properties) are very complex. They depend not only on the material of which the product or article is made, but also, and mainly, on the system of which the article forms a part. As far as the article itself is concerned, the product or article properties are in principle determined by combinations...
The properties of polymers can be divided into three interdependent categories—intrinsic properties, processing properties, and product or article properties. Whereas intrinsic properties always refer to a substance, product properties refer to an entity; they also depend on size and shape. Processing properties occupy an intermediate position. A p...
This authoritative, widely cited book has been used all over the world. The fourth edition incorporates the latest developments in the field while maintaining the core objectives of previous editions: to correlate properties with chemical structure and to describe methods that permit the estimation and prediction of numerical properties from chemic...
A new relationship has been found for the Newtonian viscosity of polymeric melts as a function of temperature and of chemical structure of the polymer unit. The viscosity-temperature correlation is expressed graphically. The activation energy of viscous flow at high temperatures can be derived from a newly found additive property, viz. the molar vi...
The rheology of concentrated polymer solutions shows a remarkable correspondence with that of polymer melts, but is more complicated due to a new parameter: the concentration of the polymer. The literature shows evidence that the viscosity of concentrated solutions is roughly proportional to the 5th power of the polymer concentration. The effects o...
Most pure substances have a definite melting temperature below which the change from a random liquid structure to a well ordered, periodic crystalline structure can occur; this transformation is called crystallization; the reverse process is called melting. The crystallization of polymers depends on the possibilities of nucleation and growth. This...
The properties of materials can always be divided into three distinct, though inseparable, categories: intrinsic properties, processing properties, and product or article properties. It should be emphasized that these three categories of properties are strongly interrelated. Whereas intrinsic properties always refer to a substance, product properti...
Product (article) properties are in principle determined by the combinations of intrinsic and added properties. However, the correlations between these basic properties and the (more or less subjectively denned) product properties are often complex and only partly understood. They are system-related. None of the mechanical product properties can be...
This chapter discusses diffusive mass transfer as observed in the practical applications of polymeric systems. It describes the permeation of simple gases through thin layers of polymers, as occurs in protective coatings and in packaging films. This category is the most widely studied; for simple gases, (such as hydrogen, air, oxygen, carbon dioxid...
A method is proposed for predicting the density of a linear, amorphous polymer. The method is based on the additivity of group increments for the molar volume of a polymer unit. It is analogous to the published methods for predicting the molar volume of organic liquids. The method may be improved as additional experimental values on polymer densiti...
A method is proposed for predicting the exponent a of the Mark-Houwink equation, [η] = KMa. This method makes use of the solubility parameters of polymer and solvent.
A method is proposed for the prediction of the intrinsic viscosity of θ solutions, based upon the constitution of the dissolved polymer. The method makes use of additive values for constitutional groups to calculate a quantity that represents the specific chain stiffness per main chain atom.
The Mark-Houwink equation for the relationship between the intrinsic viscosity of a polymer Solution and the molecular weight can be expressed in the more general form: [η] = 32Kθ(M/1000)a, where the constant Kθ has a theoretical meaning and the constant a is approximately equal to 0.7.
It is shown that the flow instability of polymer melts occurring above a certain critical shear stress is a direct result of the degree of non-Newtonian behavior of the flowing liquid. Melt fracture, elastic turbulence, and slip-stick effects are a consequence of this instability, which frequently leads to periodic phenomena. The condition for the...
The reaction kinetics of the oxidation previously measured in batch experiments are completely confirmed by experiments carried out in a continuous stirred tank reactor, both during steady and unsteady operation (starting-up). The measurements have furnished some supplementary data about the rate of by-product formation and about the influence of t...
The oxidation of cyclohexanol with nitric acid to adipic acid proceeds via two stable intermediates known from the literature¹ viz. 6‐hydroxyimino‐6‐nitro hexanoic acid and the hemihydrate of 1,2‐cyclohexanedione, two substances forming beside each other in a given ratio. This ratio can be calculated as a function, of the temperature and of the nit...
Granules of wet marl, suspended from the beam of a torsion balance, were dried in a current of dry air. Two rate periods were observed; during the first the rate of drying remains constant, during the second it decreases. With the aid of the conception of Ceaglske and Hougen on moisture distribution in granular materials equations for the rate of d...
Citations
... Dielectric constants were obtain from literature and were reported between 20 and 25 C. 31 HSPs were obtained from literature 26 or were calculated from group contribution methods (GCMs), which is a widely accepted technique for approximating HSPs. [32][33][34][35] It is assumed that the functional groups' contribution to the cohesive energy density are additive which is true when one polar or hydrogen-bonding functional group is present. 26 Hoftyzer and van Krevelen's method to calculate HSPs were estimated using the following equations: 36 ...
... 32,34 Hanse solubility parameter values for diethyl carbonate, styrene carbonate, glycerol 1,2-carbonate CTA and chitosan, were calculated with the help of Table S1 (Supporting Information). 40,41,36,35 Hansen solubility parameters (HSPs) values for each substance (polymer or solvent) were calculated using the following eqs (eqs 2−4); ...
... where ρ represents the membrane density, and V and V w represent the specific volume and van der Waals volume, respectively. V w was obtained through a group contribution method (see Table S2) [35,36]. Fig. 2g reveals that the FFV decreased in the order of 6-AL, 4-AL, and 2-AL membranes, in agreement with the XRD, DSC and density results. ...
... It was found that D O2 obeys an Arrhenius law for PA 6-6 in glassy state. As an indication, its corresponding Arrhenius parameters are reported in Table 3. Table 2 Physico-chemical characteristics of some aliphatic PAs and PE [36,37]: molar mass of monomer unit (m UCR ), density of amorphous phase (r a ), concentration of oxidizable groups in the amorphous phase [PH], average values of density (r) and crystallinity ratio (X C ). On the contrary, S O2 varies erratically with temperature confirming that, in PA 6-6 as in almost all other polymers [50], it is practically temperature independent. ...
... The gas permeation coefficients (P) for N 2 , O 2 and CO 2 were recorded in Table 6. The values followed the usual order P N2 < P O2 < P CO2 for polymers [41]. PDePD26 showed the lowest gas permeability (P N2 = 0.03 barrer, P O2 = 0.07 barrer and P CO2 = 0.3 barrer), which was contrary to the water vapor permeability. ...
... This brittle failure mode was also observed by means of the SEM analysis, starting the cavitation process with the formation of the craze that spreads and ends up breaking, giving rise to the crack. Crazing is favoured by several conditions such as high strain rates, cyclic loadings, exposure to external agents, among others [36]. The following section (section 3.3) further discusses the effect of temperature that increased as a consequence of a higher spindle speed, which may have led to the occurrence of crazing. ...
... In this period, the nitrous acid (HNO 2 ) was generated and played an important role in the whole oxidation process. 37 The induction period became longer with decreasing the temperature. ...
... In contrast, the experimentally determined S values decreased with increasing temperature. The S value for ORM was ∼20-fold higher than that of PET, reflecting the higher hydrohilicity of ORM [26,57]. The ORM structure has silanol groups that bind water molecules via hydrogen bonds [51,58]. ...
... For example, Marco et al. [24] suggested that the production of char from PET was induced by the existence of the =O bonds of the ester groups in the polymer, as well as the presence of the doubly substituted aromatic nucleus in the PET structure. Krevelen and Nijenhuis [25], introduced the concept of the char-forming tendency of different plastic polymers during the pyrolysis process based on their chemical structure and reported that the tendency of char formation relevant to the plastic investigated here was polyalkenes <PS<PET. Table 5 also shows the volumetric gas composition of the gases generated in the three-stage process from the single plastics investigated. ...
... Leather by nature has a very good FR property. As per literature reports, the limiting oxygen index (LOI) of leather is between 27 and 29%, which is well above the recommended minimum LOI value (26%) for non-flammability of materials (Van Krevelen and Te Nijenhuis, 2009). On the other hand, synthetic polymeric fabrics, natural textile materials, wood, etc. used in upholstery and furniture have LOI value much below the recommended minimum LOI limit (26%) (Van Krevelen and Te Nijenhuis, 2009). ...
