Polyvinyl acetate crystallinity

Although they do not crystallize, polyvinyl acetates prepared at low temperatures apparently arc more syndiotactic since they yield more than usually crystalline polyvinyl alcohols by saponification. Monomers of high polarity such as vinyl trilluoraeetate by radical polymerization can form... 

Most thermoplastic foams can be solvent cemented. However, some solvent cements will collapse thermoplastic foams. The best way to determine if such a problem exists is to try it. In cases where the foam collapses due to softening of the foam cell walls it is desirable to use water-based adhesives based on SBR or polyvinyl acetate, or 100%-solids adhesives. In general, the relatively amorphous thermoplastics, such as the cellulosics, polycarbonate, and polystyrene are easier to solvent cement than the crystalline materials, but there are exceptions. 

In the polymer industry, packing material, laminates including multilayer films, pellets or molded products can be analyzed by NIR. Even polymer latex particles with up to 99 % water content may be analyzed. NIR provides information about reaction mechanisms, polymerization, crystallinity, orientation, water content and hydrogen bonding, even during the process of polymer manufacture. For example the disappearance of the double bonds in polyethylene and polypropylene can be monitored. In the NIR spectrum C=C bonds lead to a combination band at about 4740 cm and a first overtone at about 6170 cm NIR spectroscopy is applied to characterize ester-, nitrile-, or amide-based acrylic and methacrylic polymers. Other examples are the identification of polyvinylchloride, polyvinyl alcohol and polyvinyl acetates or the analysis of polymerization in epoxy and phenolic resins. 

Polyvinyl alcohol [PVA] is a semi-crystalline water-soluble synthetic polymer made from hydrolysis of polyvinyl acetate. This material is also found to be biodegradable and mineralized in various environments. The degree of solubility and biodegradability as well as other physical attributes can be controlled by varying the MW and the degree of hydrolysis of the polymer [Chauhan, 2012]. 

Although polyvinyl acetate is amorphous, PVA derived from the former in most cases gives a crystalline x-ray diffraction pattern. When PVA fiber is drawn, an x-ray fiber diagram is... 

Other polymers that can provide delayed-tack adhesives include styrene-butadiene copolymers, polyvinyl acetate, polystyrene, and polyamides. Solid (crystalline) plasticizers for these adhesives include dicyclohexyl phthalate, diphenyl phthalate, A-cyclohexyl-p-toluene sulfonamide, and o/p-toluene sulfonamide. Adhesives with different heat-activation temperatures could be obtained because of the range of melting points available. Delayed-tack adhesives have a large number of uses, such as coating paper for labels on bread packages, cans, etc. 

The spectrum of the first chemical component, the concentration profile ci resolved by MCR, and the 3D map of the generated matrix Xi =c x are shown in Fig. 12 the 3D map shows the decline of absorbance. The smallest peak at 1713 cm is due to the C=0 stretching vibration it is clear that PVA itself does not contain a C=0 group. Because the production of a 100 mol% degree of saponification is technically difiicult [13], usually the small C=0 residual in polyvinyl acetate (PVAc, Fig. 6b) from the saponification reaction includes the C=0 band. However, it is not clear whether the small amoimt of residual PVAc groups show absorbance values close to 0.1 or not. Since the measurement of IR spectra began at 140 °C (at which point crystalline material starts to melt), there exists a possibility that some part of the PVA formed C=0 moieties via the... 

EVA (ethylene vinyl acetate) is a copolymer which is available in various compositions of ethylene and vinyl acetate. At a content of 50 vinyl acetate or more the crystallinity has been vanished completely. Give qualitatively the nitrogen permeability at room temperature for a copolymer with 10%, 50% and 90% vinyl acetate respectively and indicate the character of the polymer in terms of rubbery and glassy, crystalline and amorphous (The glass transition temperatures of the pure polymers polyethylene and polyvinyl acetate are given in table II - 5). 

Soft, waxy Low molecular weight (< 10,000) Low crystallinity Example polyvinyl acetate chewing gum... 

As already mentioned, ethylene vinyl acetate copolymers can be synthesized in every ratio of the comonomers. The resulting polymers exhibit the complete scale of properties from thermoplastic material to elastomers. Polyethylene is a well-known thermoplastic with a very low glass transition temperature at about — 120°C and very high crystallinity of 40%-60%. Polyvinyl acetate is also a thermoplastic, but with a glass transition temperature of 28°C and completely amorphous stmcture. 

Polychloroethene (polyvinyl chloride), as usually prepared, is atactic and not very crystalline. It is relatively brittle and glassy. The properties of polyvinyl chloride can be improved by copolymerization, as with ethenyl ethanoate (vinyl acetate), which produces a softer polymer ( Vinylite ) with better molding properties. Polyvinyl chloride also can be plasticized by blending it with substances of low volatility such as tris-(2-methylphenyl) phosphate (tricresyl phosphate) and dibutyl benzene-1,2-dicarboxylate (dibutyl phthalate) which, when dissolved in the polymer, tend to break down its glasslike structure. Plasticized polyvinyl chloride is reasonably flexible and is widely used as electrical insulation, plastic sheeting, and so on. 

ABA ABS ABS-PC ABS-PVC ACM ACS AES AMMA AN APET APP ASA BR BS CA CAB CAP CN CP CPE CPET CPP CPVC CR CTA DAM DAP DMT ECTFE EEA EMA EMAA EMAC EMPP EnBA EP EPM ESI EVA(C) EVOH FEP HDI HDPE HIPS HMDI IPI LDPE LLDPE MBS Acrylonitrile-butadiene-acrylate Acrylonitrile-butadiene-styrene copolymer Acrylonitrile-butadiene-styrene-polycarbonate alloy Acrylonitrile-butadiene-styrene-poly(vinyl chloride) alloy Acrylic acid ester rubber Acrylonitrile-chlorinated pe-styrene Acrylonitrile-ethylene-propylene-styrene Acrylonitrile-methyl methacrylate Acrylonitrile Amorphous polyethylene terephthalate Atactic polypropylene Acrylic-styrene-acrylonitrile Butadiene rubber Butadiene styrene rubber Cellulose acetate Cellulose acetate-butyrate Cellulose acetate-propionate Cellulose nitrate Cellulose propionate Chlorinated polyethylene Crystalline polyethylene terephthalate Cast polypropylene Chlorinated polyvinyl chloride Chloroprene rubber Cellulose triacetate Diallyl maleate Diallyl phthalate Terephthalic acid, dimethyl ester Ethylene-chlorotrifluoroethylene copolymer Ethylene-ethyl acrylate Ethylene-methyl acrylate Ethylene methacrylic acid Ethylene-methyl acrylate copolymer Elastomer modified polypropylene Ethylene normal butyl acrylate Epoxy resin, also ethylene-propylene Ethylene-propylene rubber Ethylene-styrene copolymers Polyethylene-vinyl acetate Polyethylene-vinyl alcohol copolymers Fluorinated ethylene-propylene copolymers Hexamethylene diisocyanate High-density polyethylene High-impact polystyrene Diisocyanato dicyclohexylmethane Isophorone diisocyanate Low-density polyethylene Linear low-density polyethylene Methacrylate-butadiene-styrene... 

The ultimate breaking stresses were compared in the process of compression of foam concretes modified with copper/carbon nanocomposites obtained in different nanoreactors of polyvinyl alcohol [21, 22]. The sizes of nanoreactors change depending on the crystallinity and correlation of acetate and hydroxyl groups in PVA which results in the change of sizes and activity of nanocomposites obtained in nanoreactors. It is observed that the sizes of nanoeomposites obtained in nanoreactors of PVA matrixes 16/1 (ros) (NC2), PVA 16/1 (imp) (NCI), PVA 98/10 (NC3), correlate as NC3 > NC2 > NCI. The smaller the nanoparticle size the greater its activity, and the less amount of NS is required for self-organization effect. 

In the comparison of BC and the BC-PVA composite, the crystallinity of BC in the composite was decreased by 50%. By immersing wet BC pellicles in polyvinyl alcohol [PVA] solution, PVA could penetrate the BC network structure and filled the pores. Acetal linkages were formed in the BC-PVA composites by a cross-linking reaction, which made PVA insoluble in water. However, the crystal destruction was observed after the cross-linking [84]. 

EVA copolymers have low crystallinity because the acetate branches interfere with crystallization. These resins are characterized by increased flexibility and resilience over a wide temperature range and by improved clarity. EVA copolymers are widely used as a nonplasticizer alternative for polyvinyl chloride (PVC) applications. These copolymers also have higher moduli than standard elastomers and are preferable in that they are more easily processed without the need to vulcanize. 

Electrical properties have been reported on numerous carbon fiber-reinforced polymers, including carbon nanoflber-modified thermotropic liquid crystalline polymers [53], low-density polyethylene [54], ethylene vinyl acetate [55], wire coating varnishes [56], polydimethyl siloxane polypyrrole composites [50], polyacrylonitrile [59], polycarbonate [58], polyacrylonitrile-polycarbonate composites [58], modified chrome polymers [59], lithium trifluoromethane sulfonamide-doped polystyrene-block copolymer [60], boron-containing polyvinyl alcohols [71], lanthanum tetrafluoride complexed ethylene oxide [151, 72, 73], polycarbonate-acrylonitrile diene [44], polyethylene deoxythiophe-nel, blends of polystyrene sulfonate, polyvinyl chloride and polyethylene oxide [43], poly-pyrrole [61], polypyrrole-polypropylene-montmorillonite composites [62], polydimethyl siloxane-polypyrrole composites [63], polyaniline [46], epoxy resin-polyaniline dodecyl benzene sulfonic acid blends [64], and polyaniline-polyamide 6 composites [49]. 

The ultimate breaking stresses were compared in the process of compression of foam concretes modified with copper/carbon nanocomposites obtained in different nanoreactors of polyvinyl alcohol [13, 14]. The sizes of nanoreactors change depending on the crystallinity and correlation of acetate and hydroxyl groups in PVA, which results in the change of sizes... 

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