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The rheological properties of PAN/DMSO solution and the size and distribution of PAN coils were studied by rheology and dynamic light scattering (DLS) measurements. It was found that water could be used as a gel accelerator and increase the gel transition temperature T
gel and the storage modulus G′ as well as decrease the damping factor tan δ thro...
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A new highly fluorescent zinc-organic framework [Zn2(btca)(DMSO)2]n (Zn-MOF) was prepared via in situ ligand formation by the solvothermal reaction of Zn(NO3)2·6H2O and pyromellitic dianhydride (PMDA) in DMSO solvent. During the solvothermal reaction, PMDA was gradually hydrolyzed to a pyromellitic acid, 1,2,4,5-benzene tetracarboxylic acid (H4btca...
Citations
Starch-based bio-foam material, as an alternative to styrofoam, has shortcomings in mechanical properties and water resistance, so it needs a filler in the form of cellulose fibre, which is insoluble in water and has strong properties. It has been studied that nanoscale fibres have an excellent mechanical property. This study aims to determine the effect of adding cellulose fibre and cellulose nanofiber (CNF) from bagasse on the characteristics of biofoam made of avocado seed starch. The manufacture of biofoam is conducted over the thermopressing method. The added cellulose fibres varied from 0%, 1%, 3%, and 5% w/w, and cellulose nanofibers ranged from 3%, 5%, 10%, 15%, and 20% w/w by weight of starch The results of testing biofoam from two different types of fillers showed that adding 5% of both fillers produced biofoam with the most excellent properties. Biofoam with 5% cellulose fibres from bagasse has a tensile strength value of 382.32 KPa, a water absorption capacity of 11.08%, and can degrade 10.94% in a specified time of 8 days. Adding 5% CNF from bagasse produced biofoam with a tensile strength of 385.02 Kpa, water absorption of 5.96%, and biodegradability value of 17.74% within eight days. It can be summarised that nanoscale fibres can increase the water resistance, mechanical properties, and biodegradability value of biofoam made with avocado seed starch.
The effects of non-solvent on the sol-gel transition of polyacrylonitrile (PAN) solution were investigated in thermodynamics and kinetics by the means of rheology method. The facilitating effects of non-solvent in thermodynamics was illustrated by the variety of viscoelasticity and gel transition temperature (Tgel). With the addition of non-solvent, the mobility of PAN molecular chains are limited due to its increased entanglement. As a result, the PAN solution with higher non-solvent content has lower conformation entropy to satisfy the occurrence of sol-gel transition at higher temperature. It means that less thermodynamic driving is demanded. The kinetical characteristics of PAN solution with different non-solvent content in sol-gel transition process were also discussed. The kinetic hindrance of non-solvent was proved by the gradually stronger time-dependence of loss tangent with the addition of non-solvent during sol-gel transition. This apparent extending of relaxation time is resulted from the more restriction of the mobility of PAN molecules. The gelation activation energy (Egel) was calculated according to Ozawa method. The results also indicated that the activity of PAN molecules in this transition became weaken with the addition of non-solvent since a relative tight connection between PAN molecules was there. Therefore, the formation of physical junction points for sol-gel transition was hindered due to the decreasing of the mobility of self-adjustment for PAN molecules. This is the fundamental reason for the kinetic hindrance role of non-solvent.
