Linked Vinyl Foams

Discussions on cross-linked vinyl foams, which are rigid, can be found below under Vinyl Foams, and rigid cellular cellulose acetate (CCA) foams and polysulfone foams are discussed in the section under Miscellaneous Foams. 

RigidPoly(vinylchloride) Foam. The techniques that have been used to produce rigid vinyl foams are similar to those for the manufacture of flexible PVC foams. The two processes that have reached commercial importance for the manufacture of rigid vinyl foams (246) are the Dynamit-Nobel extmsion process and the Kleber-Colombes Polyplastique process for producing cross-linked grafted PVC foams from isocyanate-modified PVC in a two-stage mol ding process. 

Polymer. There is a natural tendency for polymer scientists to assume that the relationships between polymer structure and properties carry over from the solid polymer to its foams as well. To some extent this is true. For example, the effects of plasticizers in vinyls and the effects of cross-linking in urethanes are well understood in the solid polymers, and they have parallel effects in the foamed plastics. In general, the properties of polymers in the solid phase can be reflected in their foams in the following ways. 

Evazote. [BXL Plastics Ltd.] Foam cross-linked ethylene vinyl acetate. 

The previous two sections reviewed characteristics of polymers that, in general, are not soluble in water and, therefore, are typically used as solid materials fibers, matrices, microspheres, or foams. Water-soluble polymers are also useful as biomaterials. Water-soluble polymers can be used in their molecular, water-soluble form as agents to modify other materials or as solid, dissolvable matrices (see the example of copolymers of methyl vinyl ether and maleic anhydride in Section A.2.2). Alternatively, water-soluble polymers may be cross-linked, by chemical or physical means, into solid materials (gels) that swell in water but do not dissolve. 

Real-World Reading Link Think how different your life would be without plastic sandwich bags, plastic foam cups, nylon and polyester fabrics, vinyl siding on buildings, foam cushions, and a variety of other synthetic materials. These products all have at least one thing in common—they are made of polymers. 

Adhesives are used in tufted carpets to anchor and stabilize the yarns they can also be used to attach a foam backing or a laminated secondary backing. Latices predominate with SBR (cross-linked) being the most widely used EVA latex (see Ethylene-vinyl acetate copolymers) is cheaper but has lower bond strength and is water sensitive. Other adhesives used are PVC plastisols in carpet tiles and hot melts and two-component polyurethanes in top-quality products (because hot melts and polyurethanes are relatively expensive). 

Flexible plastic foams may be found in the form of very soft cushioning materials used in upholstery, clothing interlayers, automobile seats, vibration absorbers, etc. The most common flexible foam resins are polyurethanes, foamed vinyls, cellular polyethylene, cross-linked polyethylene, and silicone foam. Semirigid foams are used for floatation devices, marine bumpers, special electrical insulation on television cables, packaging, and a host of other applications. Rigid foams are used in the production of airplane parts, boats, electronic encapsulation, and many furniture applications where wood was formerly used. 

Polyethylene (PE) high-density (HOPE), low density (LDPE), hnear low density (LLDPE), ultra high molecular weight (UHMWPE), cross linked (XLPE), and polyethylene foam Ethylene copolymers ethylene-vinyl acetate (EVA), ionomers Polypropylene (PP)... 

PET in fibers and bottles and polycarbonates in compact discs represent large-volume markets. As with most polymer families, there is a wide diversity of applications, many of which involve combinations with other materials. Aliphatic polyesters have been used as lubricants and vinyl plasticizers. Hydrolytic stability is a factor to be considered in many applications. As a rule, aryl acids and branched-chain diols resist hydrolysis. Fibers and films of terephthalic acid esters and polycarbonates are not particularly sensitive to moisture. Alkyd resins are so highly cross-linked in the final coating that water is not a major problem, although alkaline solutions of soaps and detergents can cause film failure. It is in the urethane foams that hydrolytic stability... 

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