Styrenic resins ester bond

Resins used were two types of epoxy resins (EP) and an unsaturated polyester resin (UP) as shown in Figure 1. EP is the bis-phenol-A type resin cured with methyl-tetrahydrophthalic anhydride (MTHPA) or 1,8-p-menthandiamine (MDA). UP is the iso-phthalic type resin which has ester bonds in the main chain and is crosslinked by styrene (10). 

Poly(vinyl ester) dispersions are quantitatively more important than solid resins. Homopolymer and copolymer dispersions are used for binders in emulsion (dispersion) paints, plastic-bonded plasters, and water-thinnable adhesives. Poly(vinyl acetate) dispersions are less important than vinyl acetate copolymer dispersions. The most important comonomers of vinyl acetate are vinyl laurate, dibutyl maleate, Versatic Acid esters (VeoVa, Shell), ethylene, vinyl chloride, and butyl acrylate. Poly(vinyl propionate) and copolymers of vinyl propionate with butyl acrylate, styrene, or vinyl chloride are also marketed and used as dispersions. 

Unsaturated polyester resins are mainly made by condensing a dibasic acid (1,2-propanediol) with an anhydride (maleic or phthalic anhydrides), by forming ester linkages between the dibasic acid (or their anhydrides) and glycols. Then a reactive monomer (mostly styrene or vinyl toluene, MMA or diallyl phthalate) is used to crosslink the system when needed. Unsaturated denotes the uncompleted chemical activity (double bond) in the original structure, which are used for crosslinking afterwards. In this context, an excess of styrene as the crosslinker (10 to 50 %) is usually added to have it ready in the system, as well as to reduce the viscosity. There are also certain accelerators used (such as, cobalt naphthenate or tertiary amines like dimethyl aniline) to facilitate the cure at ambient temperatures. In addition, there may be pigments, fillers, various inhibitors, accelerators, stabilisers and flame retardants, added to the system. Polymerisation is activated whenever a catalyst (i.e., benzoyl or methyl-ethyl-ketone peroxide) is added. 

Contact resin n. A liquid resin that thickens or cross-links on heating and, when used for bonding laminates, requires little or no pressure. Typical components are an unsaturated monomer such as an allyl ester, or a mixture of styrene or other vinyl monomer with an unsaturated polyester or alkyd. 

An unaccelerated, low viscosity, styrene free, corrosion resistant (to acidic and aikaline environments), flame retardant (<25 ASTM E-84 with 3% antimony trioxide) vinyl ester, offering high strength, excellent impact strength and toughness, designed to bond Hetron FR 992 resin laminates and meet the low odour requirements of the semiconductor and other industries. Since this resin does not contain styrene, the glass reinforcement must exhibit very little binder conventional CSM s do not wet-out well with this resin. 

Other workers have carried out comparisons of Tg determined by DMTA and DSC. Good agreement as obtained for amorphous polyethylene terephthalate (PET) -polyethylene naphthalate bonds [9], aromatic polyimides [10], epoxy-based divinyl ester resin-styrene copolymers [11], bisphenol A-epoxy diacrylate-N-vinyl pyrrolidine networks [12], and polyesters [13]. 

The effects of solvent exposure on the viscoelastic properties of several vinyl ester resins (phenohc-novolac epoxy, propoxylated bisphenol-A fu-marate, urethane and bisphenol-A epoxy based) and various unsaturated polyester resins (terephthalic or isophthaUc acid with a standard glycol based) containing 10wt% glass fiber were studied [130]. The results of dynamic mechanical analysis showed that the influence of exposure time to the solvent as well as the influence of temperature depended on the styrene content and chemical composition of the studied resins, while the amount of cobalt octoate used for the synthesis as the accelerator had no influence on the viscoelastic properties of the prepared materials after solvent exposure. It was also found that not fully cured urethane vinyl ester and the terephthahc acid-based unsaturated polyester resins showed excellent resistance to sulfuric acid exposure. However, interactions between the tested resins and petroleum could possibly occur through intermolecular bonding between the non-polar chains of the cured resins and the solvent. 

These admixtures are used to increase the bond strength in repair applications, to decrease shrinkage, increase tensile strength, etc. The polymers used include latexes, redispersible polymer powders, water-soluble polymers, liquid resins, and monomers. In practieal applications, styrene butadiene rubber, polyacrylic ester and polyvinylidene chloride-vinyl chloride, methylcellulose, etc., have been used. 

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