Copolymers polyethylene/vinylacetate

IN-LINE FIBRE-OPTIC NEAR-INFRARED SPECTROSCOPY FEASIBILITY STUDIES FOR THE SIMULTANEOUS MONITORING OF VINYL ACETATE AND ERUCAMIDE ADDITIVE CONCENTRATIONS IN POLYETHYLENE-VINYLACETATE COPOLYMERS Vedula S Hansen M G Deshpande B J Tennessee,University (SPE)... 

The experimental protocol of our studies involved the exposure of fresh healthy platelet-rich plasma (PRP) of young males to 9 pure synthetic polymers, namely polyethylene, ethylene-butylene copolymer, ethylene-propylene copolymer, ethylene-ethylacrylate copolymer, ethylene-vinylacetate copolymer, ethylene-methylmethacrylate sodium ionomer, nylon 12, polyurethane, and tetrafluoroethylene-hexafluoropro-pylene copolymer ( Figure-1). Polymer pellets tested have been especially synthesized under clean conditions and were substances of known composition, free of plasticizers and... 

This technique is capable of determining a wide range of elements, e.g., chlorine in polyolefins, metals in polymethylmethacrylate [64], total oxygen in polyethylene-ethylacrylate and polyethylene-vinylacetate copolymers [65], and total oxygen in polyolefins. 

Polymers with more than one type of repeating unit are referred to as copolymers, and they are important in that they have properties different from either homopolymer. One example of a copolymer is polyethylene-vinylacetate which is widely used as a hot melt adhesive. Another is acrylic fibre where a small amount of comonomer added to acrylonitrile makes it easier to spin and to dye. In both these examples the monomers are mixed together and then polymerised by a free radical process the resulting copolymer has a random arrangement of the two units along the chain. Using more specific methods of polymerisation it is possible to prepare block and graft copolymers. 

In the course of prolonged service life, UV absorbers are losing their absorption behavior, for example, by reaction of their phenolic function with peroxy radicals. Besides chemical reactions, simple depletion of such compounds can be another reason for the loss of their efficiency. For example, benzophenone-type UV absorbers are described to deplete from polyethylene-vinylacetate copolymer (EVA)-based encapsulants used in solar cells.In order to avoid such deficits, attempts have been made to develop UV absorbers incorporated in polymer stmctures. Manifold experimental results indicate that the loss of UV absorbers is initiated by light-induced decomposition reactions rather by migration from polymer substrates. 

Unexpectedly, PVC/rubber blends show under certain circumstances quite a different morphology. This was shown experimentally for chlorinated polyethylene and ethylene-vinylacetate copolymers as rubber phase. 

Some thermoplastics are crosslinkable and are used industrially in their two forms, thermoplastic and thermoset for example, the polyethylenes or the vinylacetate-ethylene copolymers (VAE) (the links created between the chains limit their mobility and possibilities of relative displacement). 

Films. Three films were included in this study. Low density polyethylene (LDPE) was included as a representative polyolefin. It is not considered to be a barrier polymer. It has permeabilities to selected aroma compounds slightly higher than the permeabilities of polypropylene and high density polyethylene (1). A vinylidene chloride copolymer (co-VDC) film was included as an example of a barrier that is useful in both dry and humid conditions. The film was made from a Dow resin which has been designed for rigid packaging applications. A hydrolyzed ethylene-vinylacetate copolymer (EVOH) film was included as an example of a barrier film that is humidity sensitive. The polymer was a blend of resins with total composition of 38 mole% ethylene. 

The theory was found to predict complex behavior near the phase separation conditions. As the rate of shear increases, first, the system undergoes homogenization, then demixing, followed by another homogenization and demixing. At high rates of shear, the system should behave similarly as in a quiescent state. These predictions were found to be in qualitative agreement with experimental data, e.g., for blends of ethylene-vinylacetate copolymer with chlorinated polyethylene, EVAc/CPE, or polystyrene with poly(vinyl methyl ether), PS/PVME [Hindawi et al., 1992 Eernandez ef fl/., 1993, 1995]. 

Chattopadhyay, S., Chaki, T. K., Bhowmick, A. K., Heat shrinkability of electron-beam-modified thermoplastic elastomeric films from blends of ethylene-vinylacetate copolymer and polyethylene. Radiation Physics and Chemistry 2000, 59(5-6), 501-510. 

The major polymers with whieh PVC ean be alloyed are aerylonitrile-butadiene eopolymers, aerylonitrile-butadiene-styrene terpolymer, ethylene-vinylacetate copolymers, chlorinated polyethylene, chlorosulfonated polyethylene, thermoplastic polyurethanes, acrylics and methacrylics, and polycaprolactone. Table 18 lists the property enhancements achieved by blending these polymers with PVC. 

The polymers used were polyvinylchloride (Sicron 230, Montedison, Italy) vinylchloride/vinylacetate copolymer (Sicron 822, Montedison, Italy) polytetrafluoroethylene (Fluon, I C.I, U.K ) polyethylene (Montedison,Italy) acrylic polymer (Paraloid K 120 N, Rohm Haas, Italy) acrylic/methacrylic acid esters copolymer with 10 % of quaternary ammonium groups (Eudragit RL, Rohm Pharma, Germany) and with S % of these groups (Eudragit RS, Rohm Pharma, Germany) ... 

There was very little decrease, however, in the platelet aggregation induced by collagen following exposure to polyethylene, ethylene-vinylacetate copolymer, polyurethane, and ethylene-methylmetacrylate sodiTom ionomer. 

Poly(ethylene-co-vinylacetate) EVA, Polyethylene ionomer EIM, Cycloolefine copolymer COC [Poly(ethylene-co-norbornene)], Poly(ethylene-co-acrylic acid) EAA Polyolefines III... 

The ethylene vinylacetate copolymers are chains with polyethylene sections of varying length depending on the amount of copolymerized vinylacetate (VA) comonomer. This family of materials has found widespread use as a pour point depressant additive for crude oils and petrochemical products, with varying degrees of success in controlling the size and morphology of the wax crystals formed. When successful as a wax crystal additive, EVA produces... 

WAL Walsh, D.J., Higgins, J.S., Rostami, S., and Weerape-Ruma, K., Compatibility of ethylene-vinylacetate copolymers with chlorinated polyethylenes. 2. Investigation of the thermodynamic parameters. Macromolecules, 16, 391, 1983. 

---