Vinyl ester resin reactivity

Of particular importance in describing the difference between these two families of resins are the locations of die reactive unsaturation. In the polyester resin, these groups are located along the backbone of die polymer with terminal hydroxyl or carboxylic acid groups. The vinyl ester resins contain no significant acidity but terminate in reactive vinyl ester groups. Because of the location of these reactive sites, the vinyl ester resins will homopolymerize as well as coreact with various vinyl monomers. 

In spite of the fact that the rheological behavior during c ire of the Ashlemd polyester resin looks very similar to that of the Dow vinyl ester resin, the Ashlcuid polyester resin is found to be more reactive them the Dow vinyl ester resin, with the same formulation emd initiator system used in this study. Some iii Kjrtemt differences in the rheological responses are reflected on (1) the values of (2) the time at which shrinkage begins to occur when the fluid is at rest emd (3) the slope of the -( ii- 22 versus cure time curve. 

In spite of the fact that the ccirbon-to-carbon double bonds in the Dow vinyl ester prepolymer chains are structoterminal emd those in the Ashland polyester resin are structopendcmt, the Dow vinyl ester resin is less reactive them the Ashlcuid polyester resin with the same formulation and initiator system. This difference in reactivity or rate of reaction cem be discussed with the aid of the DSC measurements presented above. 

First, it is seen in Figure 3 that the meiximum value of dQ/dt (i.e., (dQ/dt)p) increases, and the time (tp) at which the mcucimum of dQ/dt occurs decreases, as the cure temperature (hence the rate of cure) increases. Over the range of temperatures investigated, the Ashlemd polyester resin exhibits higher values of (dQ/dt)p emd lower values of tp than the Dow vinyl ester resin, indicating that the former is more reactive than the latter. Second, although... 

Dion VER. [Reichhold/Reactive Polymers] Vinyl ester resin. 

Unsaturated polyester resins and vinyl ester resins are styrene-based matrices cured by free radical copolymerization of the reactive diluent (solvent) styrene and the unsaturated groups in the dissolved polymeric ester. In the case of the polyester resins the unsaturated groups are within the molecular backbone of the polyester (Structure (V)). 

The chemical reactivities of the unsaturated groups at the ends of vinyl ester resin and vinyl urethane resin chains are different in several respects from those of the same groups when situated in mid-chain positions, as they are in polyester resins. As a consequence of the different reactivity ratios, the two kinds of cured resin behave differently from moisture and chemical resistance points of view. The structural differences are also reflected in the mechanical properties, such as fracture toughness. 

These same rules apply to other resins such as the family of unsaturated polyesters. In these, the reactive diluents dilute the ester groups. A reduction in ester group concentration can be achieved by using more rigid skeletal structures and employing only terminal ester groups (vinyl ester resins) or urethane links (vinyl urethanes, urethane methacrylates). The chemical resistance of these resins is summarized in Table 3.6. 

Unsaturated polyesters contain a relatively high number of double bonds per polymer molecule as well as reactive end groups which remain unreacted after the cross-linking reaction. These unreacted groups have a negative effect on the network properties. These unfavorable structural defects are largely eliminated in what is known as vinyl ester resins ... 

Vinyl esters are thermosetting resins that consist of a polymer backbone with an acrylate or methacrylate termination. The backbone component of vinyl ester resins can be derived from epoxide, polyester or urethane but those based on epoxide resins have most commercial significance. Bisphenol A epoxy formed vinyl esters were designed for chemical resistance and commonly formulated for viscosity for use in filament winding of chemical containers. Typically styrene is used as a reactive dilutent to modify viscosity. Phenolic novolac epoxies are used to produce vinyl esters with higher temperature capability and good solvent resistance, particularly in corrosive environments, and their FRP composites have demonstrated initial economy and better life cycle costs compared with metals. 

Vinyl ester resins are made from the esterification of epoxy resins via their terminal epoxy group with an unsaturated acid such as methacrylic acid derived from epoxy resin. The resultant polymer is typically dissolved in a reactive monomer such as styrene. 

The acid-epoxide reaction is straightforward and is catalysed by tertiary amines, phosphines or ammonium salts. Vinyl ester resins are diluted with a reactive monomer such as styrene, vinyl toluene or dicyclopentadiene acrylate. Similar to other unsaturated polyesters, the production of vinyl esters is carried out in batch reactors. The basic steps of the process are ... 

There are certain differences between the cure of vinyl ester resins and that of unsaturated polyesters. MEKP with a high dimer content is more reactive with vinyl esters than the standard varieties, but less reactive with polyesters. 

A430 (Palatal 430) is a medium viscous, highly reactive vinyl ester resin based on bisphenol A dissolved in styrene. It is characterized by high chemical resistance. 

Cured vinyl ester resins are fragile after curing like standard UPRs and thus need flexibilization. The flexibilization of vinyl ester resins is made using the known reactive rubber vinyl-terminated liquid elastomeric butadiene-acrylonitrile copolymer (VTBN) [76]. The macrostructure of the VTBN flex-... 

Glycidyl and Vinyl Esters. Glycidyl neodecanoate [26761-45-5] sold commercially as GLYDEXXN-10 (Exxon) or as CarduraElO (Shell), is prepared by the reaction of neodecanoic acid and epichl orohydrin under alkaline conditions, followed by purification. Physical properties of the commercially available material are given in Table 3. The material is a mobile Hquid monomer with a mild odor and is used primarily in coatings. Eor example, it is used as an intermediate for the production of a range of alkyd resins (qv) and acryHcs, and as a reactive diluent for epoxy resins (qv). 

Although polyurethanes or other reactive resins can be used in RTM, the most common resins are polyesters and epoxies. The two pumping reservoirs in Figure 7.90, then, contain polyester resin and initiator, or epoxy resin and hardener, respectively. Epoxies require relatively long cycle times. When cycle time is critical, low viscosity vinyl ester, acrylamate, or urethanes can be injected very rapidly into the mold. Even the use of thermoplastics is possible. 

Dianol . [Akzo] Ethoxylaled bisphenol A diol reactive modifiers for saturatol and unsaturated polyesters, vinyl esters, and polyurethane resin formulations. 

Epoxy di(meth)acrylates (also caUed vinyl esters) are another name for the p-hydroxyester acrylates, because they are usuaUy obtained by reacting epoxy resins of glycidyl derivatives with (meth)acrylic acid. They can also be manufactured from bisphenol A and glycidyl (meth)acrylates. Although prepared from compounds containing reactive epoxy groups, completed epoxy di(meth)acrylate molecules do not contain these groups. Both aromatic and aliphatic epoxy di(meth)acrylates are available, as weU as acrylated epoxydised oUs (Jolanki 1991 Jolanki et al. 1995). 

Another class of coatings, formulated in a similar manner, are the vinyl esters. The vinyl esters derive from a resin based on a reactive end vinyl group that can open and polymerize. The chemical structure is shown in Figure 12.5. 

Tetrahydrofurfuryl alcohol (THFA) is used to prepare tetrahydrofurfuryl acrylate and methacrylate in transesterification reactions with lower acrylate esters. These reactive monomers are used in the formulation of ultraviolet light-curable adhesives, coating, paints, and printing inks. THFA is an effective coalescing solvent for latex paints and is used in epoxy resin formulations. The oleic acid ester of THFA is used as a plasticizer for vinyl resin products. The high solvency of tetrahydrofurfuryl alcohol for dyes permits higher dye... 

Vinylesters are unsaturated, hence thermosetting, resins, prepared by the reaction of a monofunctional unsaturated acid, e.g. methacrylic, acrylic, crotonic or cynnamic acid, with a bisphenol diepoxide. This type of structure is referred to as bisphenol-A epoxy vinyl ester (Fig. 4.3(a)). The structural difference, which at least partially justihes the improved chemical and mechanical properties of vinylester, is the presence in vinylesters of reactive double bonds at the ends of the chains only, while unsaturated polyester resins have the reactive double bonds distributed throughout the chains. 

A high strength, thickenable, highly reactive vinyl ester base resin for use in SMC or BMC moulding for automotive application. Offers excellent physical properties, high heat resistance and high tensile elongation. 

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