Vinyl ester-based composites

Phenolic resins exhibit excellent dimensional stability with a constant use temperature range of 180-200 °C, excellent resistance to chemicals, moisture, and heat and favorable behaviour against fire and smoke. The predominant consideration in the use of phenolic resins as a matrix resin in fibre-reinforced composites is fire behaviour. Phenolic-based composites perform better under fire conditions compared with epoxy- or vinyl ester-based composites. This is due to their delayed ignitability coupled with low heat release, low smoke evolution with little or no toxic gas emission, and capability to provide significant strength retention (70%)... 

The wheelbase is still considered a challenge for plastics, although plastics can make a significant improvement to the rotational mass in the car. No major OEM has introduced wheels made entirely of plastics yet. Vinyl ester-based composites had been attempted but with no commercial success. 

Chigwada, G., Jash, P, Jiang D.D., and Wilkie, C.A. Fire retardancy of vinyl ester nano composites Synergy with phosphorus-based fire retardants, Polym. Degrad. Stab., 2005, 89, 85-100. 

Mazzola et al used polyesters for foamed composites (6). Narkis et al (27) described foamed polyester composites made using random glass mat. Saidla et al (28) reported making foamed polyester composites using -inch glass fibers. Vinyl ester/styrene copolymer foams were developed by Olstowski and Perrish (10, 11). Vinyl ester-based hybrid-foam composites were developed by Frisch and Ashida (19). 

While epoxy resins are known for excellent chemical resistance properties, the development and commercialization of epoxy vinyl ester resins in the 1970s by Shell and Dow offered enhanced resistance properties for hard-to-hold, corrosive chemicals such as acids, bases, and organic solvents. In conjimction with the development of the structural composites industry, epoxy vinyl ester resin composites found applications in demanding environments snch as tanks, pipes and ancillary equipment for petrochemical plants and oil refineries, automotive valve covers, and oil pans. More recently, epoxy and vinyl esters are used in the construction of windmill blades for wind energy farms. Increasing requirements in the composite industries for aerospace and defense applications in the 1980s led to the development of new, high performance multifunctional epoxy resins based on complex amine and phenolic structures. Examples of those products are the trisphenol epoxy novolacs developed by Dow Chemical and now marketed by Huntsman (formerly Ciba). 

Materials. The epoxy resin was provided by Advanced Composites Group Ltd UK (ACG), with a brand name of EF6305. The low cost epoxy resin was in a film form with a thickness of about 0.1 mm. It was an amine-cured Bisphol-A type epoxy resin. The vinyl ester was provided by Reichhold with a brand name of DION 9400-800, which was a 75 25 mix of DION 9400 (an epoxy novalac based vinyl ester base polymer) and low profile additive (Scott Bader 30% PVAc in styrene). The vinyl ester was cured using 1.0 wt% Akzo Nobel Trigonox C (TBPB). 

A foamable composition nsefnl for rotational moulding is described, which advantageonsly inclndes an ethylene vinyl ester copolymer as an additive. The additive beneficially has a higher melt index than the base resin of the composition. 

Epoxy resin adhesives for aluminum, glass, and steel have been prepared by converting octaallyl or octacrotyl-sucrose to the corresponding epoxides which were cured with diethylenetriamine.157 Several plastics, resins, and adhesives have been based on soybean oil.158 Vinyl esters of the fatty acids can be used as monomers. The oil can be epoxidized, then hydrolyzed to glycols, which can be converted to acrylates or maleates for polymerization. Natural fibers, such as hemp, can be used with such materials to form inexpensive composites. 

Other variables investigated with respect to fracture toughness include processing parameters, e.g.. production schedules and postcure cycles [166.171] for thermosets, and cooling rates for thermoplastics [171] matrix composites, and moisture content. A study [171] on composites based on epoxy and vinyl ester matrices has shown that whilst matrix plasticization improves mode I fracture toughness, mode II fracture toughnc.ss deteriorates due to interface degradation. The sensitivity of (Jut to water absorption has been demonstrated even for matrices that absorb very small amounts of water such as pol propy lene [168]. 

As for the, hazards associated with skin contact, usually, dermatitis (allergic contact dermatitis) is the common occupational health complaint that has been reported for thermoset plastics materials. It is known that plastic composites based on polyester, epoxy and vinyl ester (epoxy diacrylate) resins can cause contact dermatitis . 

Uniaxial tensile tests have been performed for four-ply and one-ply composites based on glass plain-weave reinforcement — Table 2.3. The composites are produced by resin infusion moulding using Dow Derakane 8084 Epoxy-Vinyl Ester resin. The weave architecmre is slightiy unbalanced exhibiting different crimp in warp and weft directions. The lay-up of four-ply composite has been balanced. 

Epoxy-based thermosets are the most widely used and versatile thermosets. They dominated the reinforcing piping field until the introduction of the vinyl esters, and they are still widely used. They find usage in many applications, including adhesives, coatings, encapsulants, tooling compounds, composites, and molding compounds. Their versatility is due to the wide latitude in properties that can be achieved by formulation. 

A need therefore existed for a material with good resistance to a broad spectrum of corrosive chemicals. Dow s development laboratories identified composite materials based on the use of a corrosion-resistant matrix such as epoxy vinyl esters. We believe that such composite materials have filled that gap admirably for us. 

Las La Scala, J. J., Logan, M. S., Sands, J. M., Palmese, G. R. Composites based on bimodal vinyl ester resins with low hazardous air pollutant contents. Compos. Sci. Technol. 68 (2008) 1869-1876. 

In the TsC the filler is also inserted in a resin matrix, typically phenolic although epoxy and vinyl ester are also used. However, there is not a carbonization step like in the CCC. Due to the similarity in composition, CCC is sometimes confused with TsC. Chaimel manufacturing in TsC is done by compression molding. Entegris Inc. commercializes TsC BPs based on vinyl ester and phenolic resin. 

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. 

Plastics, particularly polymer-based composites (both thermoplastic and thermoset composites), have been exploited in transportation appUcations for decades. The use of common composites such as glass or carbon fiber reinforced unsaturated polyesters, epoxy, and poly(vinyl ester) matrices is well known. The unique advantage of composites is their strength (tensile strength 4-6 times that of steel) and stiffness, despite their lightweight. 

Alpha Owens-Coming offers a flame retardant vinyl ester resin that meets ASTM 84 Class 1 flame spread and smoke rating. The resin is a highly brominated bisphenol-A epoxy based vinyl ester. It provides a unique combination of good flame and smoke resistance and inherently good mechanical properties. The flexural strength of 34% glass composite is 5100 psi (35 MPa) and flexural modulus is 450 ksi (3.1 GPa). 

Pultrusion is a simple technique which is employed mostly for fabrication of products based on unsaturated polyester resins (or other resins like epoxy, vinyl ester) and continuous strand mats (fibre or fabric). A pultrusion machine consists of creel for supplying fibre, a resin tank, forming dies, machined dies with a temperature control facility, a puller and a saw for cutting the product from a continuous composite product. The continuous strand mats are passed through a bath containing a mixture of resin and curatives. In the resin bath, the fibre is passed through a series of rods to remove entrapped air and excess resin to ensure complete wetting of the fibre. 

Krigbaum [12] has reported on the use of glass fibre reinforced composites, both from Cytec Industries, based on Cyglas 685 unsaturated polyester [bulk moulding compound (BMC)] and Cyglas 695 vinyl ester resin (BMC) in automotive valve covers and other engine cover applications. The recycling of these valve covers is also discussed. 

Product 41 (composite resin based on vinyl ester) ... 

Stewart RD, Dodd HC, Baretta ED, Schaffer AW (1968) Human exposure to styrene vapor. Arch Environ Health 16 656-662 Tarvainen K (1996) Occupational dermatoses from plastic composites based on polyester resins, epoxy resins and vinyl ester resins. People and Work 11 1-66 Tarvainen K, Jolanki R, Estlander T (1993a) Occupational contact allergy to unsaturated polyester resin cements. Contact Dermatitis 28 220-224... 

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