Carboxylated vinyl acetate-ethylene polymer

Carboxyl functionality increases the adhesion of vinyl acetate-ethylene to several metals (Table 7). A conventional vinyl acetate-ethylene and a carboxylated vinyl acetate-ethylene polymer both may have the same glass transition temperature and the same ratio of vinyl acetate to ethylene, but the carboxylated vinyl... 

Table 7. Peel Strength of Cloth-to-Metal Bonds (lbs./linear In.) —Effect of Carboxyl Functionality on Vinyl Acetate-Ethylene Polymers...

The incorporation of a carboxyl functionality reduces the softening range of vinyl acetate-ethylene resin while enhancing its adhesion. Fig. 12 shows the difference in adhesion between carboxylated vinyl acetate-ethylene and conventional vinyl acetate-ethylene polymer when each is used as a heat-seal adhesive for bonding two pieces of commercial polyvinyl chloride film. For test purposes, these emul-... 

Soon after the first preparation of vinyl acetate by the reaction of acetic acid with acetylene and its polymerization by Klatte [209] in 1912, methods for its industrial-scale synthesis were developed first in Germany, then in Canada [210]. At the same time, the chemistry was extended to the preparation and polymerization of vinyl esters of other aliphatic and aromatic carboxylic acids. The new polymers found immediate uses in paints, lacquers, and adhesives. Steady improvements in the industrial-scale monomer synthesis, particularly in the discovery of new catalysts for the acetic acid-acetylene condensation and development of a low-cost synthesis route based on ethylene have made vinyl acetate a comparatively inexpensive monomer. Besides the original applications, which still dominate the major uses of poly(vinyl acetate), this polymer finds additional utility as thickeners, plasticizers, textile finishes, plastic and cement additives, paper binders and chewing gum bases, among many others. At the same time, the uses and production of polymers of the higher vinyl esters have not kept pace with that of poly(vinyl acetate), primarily due to their higher cost. Consequently, the current worldwide production of these materials remains low. 

Another example of DMA applied to characterize polymer blends is illustrated in Fig. 5.8 for a phase separated blend of PS/VAE(vinyl acetate-ethylene copolymer 70 wt% VAc) compared to SAA copolymer(AA = 8 and 14 wt%)/VAE(70 wt% VAc) blends [25]. The modest addition of AA to PS yields miscibility with VAE, due to specific interactions (presumably hydrogen bonding of carboxylic acid with the carbonyl of vinyl acetate). The miscible blend transition is broader than typical homopolymer systems as often observed in blends exhibiting single Tg values. 

The EVA polymer emulsions contain crystalline segments resulting from ethylene linkages. In addition to ethylene and vinyl acetate, a carboxylic comonomer is used, such as acrylamide or versa tic acid vinyl ester. The polymers have crystalline melting point of 50-90°C. 

A conventional emulsion polymer based on vinyl acetate has been modified by carboxylation (92). The carboxylated ethylene-vinyl acetate adhesive increases the adhesion to metal and polymer surfaces and the resistance to oil, grease, and water. The films are also acid, alkali, and UV resistant. Furthermore, the polymers are cross-linkable through the carboxylic groups. These adhesives can react with aminoplasts, phenolics, and epoxy resins for increased water and creep resistance. 

Three-component polypropylene, 1-99 wt% PP, blends comprised 1. either acidified PP, its mixture with PP, or a mixture of PP with carboxylic acid-modified EPR 2. 99-1 wt% of maleated polymer [e.g., poly(methyl methacrylate-co-styrene-co-MA] and 3. epoxy group-containing copolymer [e.g., 0.1-300 phr of ethylene-methyl methacrylate-glycidyl methacrylate = 65-15-20 or ethylene-vinyl acetate-glycidyl methacrylate = 85-5-10]. The blends were used to mold car bumpers and fenders, with good stiffness and low-temperature impact resistance ... 

Aliphatic dicarboxylic acid dichlorides were applied to the surface-saponified blend of 50 wt% poly(ethylene-co-propene) and 50 wt% poly(ethylene-co-vinyl acetate) (PP/EVA). After coupling without cyclization, the second carboxylic acid group is available for the covalent binding of the protein via the W-terminal amino group [ 140]. The use of anhydrides, e.g. glutaric acid anhydride, is another possibility to introduce free carboxyl groups into the polymer surface. 

Some spectroscopic evidence for the formation of ionic bonds across adhesive interfaces is as follows. Using reflectance IR, Bistac et al. [24] showed that for an ethylene-vinyl acetate polymer grafted with 1% of maleic anhydride, and bonded to iron or zinc, new absorptions were present which were attributed to carboxylate (-COO ), and their presence coincided with strong adhesion. In an IR study of the bonding of maleic anhydride to naturally oxidised aluminium, Schneider et al [25] showed that the anhydride is hydrolysed in the early stages of adhesion, taking about 1 min on exposure to laboratory air. They suggested that the hydrolysed acid is bonded to two aluminium cations as shown in Fig. 5. 

Solvent adhesives and reactive adhesives are made from homo- and copolymers of methacrylates, generally methyl and ethyl methacrylate and, occasionally, butyl methacrylate. Monomeric (meth)acrylates are also used in reactive adhesive systems (polymerization adhesives). Poly(ethyIene glycol) dimethacrylates are the basis of anaerobically curing liquid resins (reactive adhesives). They also are added as adhesion promoters to plastisol adhesives. Acrylate-ethylene copolymers, in some cases with a small content of carboxyl groups, are used instead of ethylene-vinyl acetate copolymers as fusible polymers for special hot-melt adhesives. Salts of polyacrylate and acrylate - acrylic acid copolymers are used as thickeners for aqueous adhesive solutions and emulsion-based adhesives. 

Various ethylene copolymers are available in which the second comonomer is a carboxylic acid or ester such as vinyl acetate, acrylic acid, meth-acrylic acid, methyl acrylate or ethyl acrylate. These copolymers are produced by free radical high pressure polymerization using processes similar to those described in section 2.3.2(a). The random introduction of rather bulky side chains into the polymer leads to a progressive reduction in crystallinity and stiffness which is directly proportional to the molar content of the comonomer, until at about 20 mole % the copolymer is completely amorphous. At the same time, the presence of polar pendant groups leads to chain interaction and increased toughness. 

Typically, a solid epoxy of 3000 to 4000 EEW (Epikote 1007 or 1009 types or an analogue material manufactured by the chain extension of a lower M liquid epoxy resin) is modified to provide an acid functional epoxy. In general, the acid functionality ctm be conferred by two methods, acid capping (see resin 1 and resin 2) of the oxirane groups or by the graft polymerisation of an epoxy with a carbonyl functional co-polymer (see resin 3). The co-polymer can consist of Ae reaction product of a free radical polymerisation of any approved ethylenic unsaturated monomers containing carbon-carbon unsaturadon, e.g. carboxyl functional acrylic monomers, (acrylic add, methacrylic acid, etc.), the lower alkyl esters, vinyl monomers (acrylamides), vinyl esters (vinyl acetate, vinyl butyrate), vinyl aromatic monomers (styrene, a methylstyrene) etc. The acrylic caj ing resin is add fimctional, being based upon either methacrylic or acrylic acid. The former is normally preferred. An acid value of 50-100 mg KOH/g would be typical. 

Interactions between a steel surface and an ethylene-vinyl acetate copolymer grafted with maleic anhydride were investigated by FTIR diffuse reflectance spectroscopy. The failed surfaces obtained after a mechanical separation of the polymer/steel assemblies were analysed. A two-step mechanism was proposed the opening of the anhydride cycle by a hydrolysis reaction, leading to the formation of a carboxylic diacid, followed by the reaction of the acid with some oxidised metallic elements present at the metal surface. This study underlines the contribution of FTIR reflectance techniques to the understanding of adhesion mechanisms. 7 refs. 

Over the years, it is fair to say that virtually every type of polymer available in dispersion form has been tried for use in the backing compound for tufted carpet. However, because of its versatility and cost-effectiveness, it is the carboxylated styrene-butadiene (XSB) polymer dispersions that hold the major share of this business today with an estimated 95 % of the volume sold in 1999, the remaining volume being shared by ethylene-vinyl acetate, polyvinyl chloride and polyurethane dispersions. During 1999, the U S carpet industry consumed approximately 490 kt wet dispersion, of which 463 kt were XSB [4]. The majority of the XSB is supplied direct to the carpet mills by the three major dispersion producers BASF, Dow Chemical, Omnova, with a minor proportion being supplied by so-called re-sellers or compounders such as General Latex, Polymer Products, Southeastern Latex and Textile Rubber. 

One of the first examples of the grafting to approach was published by Sun et al. in 2001 [32]. In this work carboxylic acid groups on the nanotube surface were converted into acyl chlorides by refluxing the samples in thionyl chloride. Then the acid chloride functionalized carbon nanotubes were reacted with hydroxyl groups of dendritic PEG polymers via esterification reactions. Similarly, many polymers terminated with amino or hydroxyl moieties have been used in amidation and esterification reactions with acid chloride modified NTs poly(propionylethylenimine-co-ethylenimine) (PPEI-EI) [33], poly(styrene-co-aminomethylstyrene) (PSN) [34], poly-(amic acid) containing bithiazole rings [35], monoamine-terminated poly(ethylene oxide) (PEO) [36], poly(styrene-co-hydroxymethylstyrene) (PSA) [37], poly(styrene-co-p-[4-(4 -vinylphenyl)-3-oxabutanol]) (PSV) [38], poly(vinyl alcohol) (PVA) [39], poly(vinyl acetate-co-vinyl alcohol) (PVA-VA) [40] or poly[3-(2-hydroxyethyl)-2,5-thienylene] (PHET) [41]. 

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