Mechanical properties rigidity

Transparency high UV and weathering resistance gloss and colour stability fair mechanical properties, rigidity and creep behaviour at ambient temperature insulating properties notably arc resistance food contact for suitable grades. 

Chemical, electrical, and thermal properties The chemical building blocks of the polyester, the molar ratio of maleic anhydride to saturated dicarboxylic acid, and the choice and content of the monomer dictate to a large extent the mechanical properties (rigid or flexible), the glass transition temperature (Tg) or HOT (heat deflection temperature), and the thermal and chemical resistance of the cured products. Additives are available for use with many resin systems to provide properties such as color, high surface finish, UV resistance, and low shrinkage. 

Below Tg the material is hard and rigid with a coefficient of thermal expansion equal to roughly half that of the liquid. With respect to mechanical properties, the glass is closer in behavior to a crystalline solid than to a... 

The mechanical properties of rigid foams vary considerably from those of flexible foams. The tests used to characterize these two classes of foams are, therefore, quite different, and the properties of interest from an application standpoint are also quite different. In this discussion the ASTM definition of rigid and flexible foams given earlier is used. 

The insulating value and mechanical properties of rigid plastic foams have led to the development of several novel methods of buUding constmction. Polyurethane foam panels may be used as unit stmctural components (220) and expanded polystyrene is employed as a concrete base in thin-sheU constmction (221). 

Packaging. Because of the extremely broad demands on the mechanical properties of packaging materials, the entire range of ceUular polymers from rigid to flexible is used in this appHcation. The most important considerations are mechanical properties, cost, ease of appHcation or fabrication, moisture susceptibUity, thermal conductivity, and aesthetic appeal. 

The mechanical properties of LDPE fall somewhere between rigid polymers such as polystyrene and limp or soft polymers such as polyvinyls. LDPE exhibits good toughness and pHabiUty over a moderately wide temperature range. It is a viscoelastic material that displays non-Newtonian flow behavior, and the polymer is ductile at temperatures well below 0°C. Table 1 fists typical properties. 

Surfa.cta.nt-TypeAntista.ts, Inherently conductive antistats have the advantage of not being dependent on atmospheric moisture to function. Thek drawbacks include expense, coloration of the plastic, and alteration of the mechanical properties of the plastic. The added stiffness caused by conductive fillers may not be a problem with a rigid container, but it can be a problem for a flexible bag. 

The classification given in Table 1 is based on the process, ie, thermosetting or thermoplastic, by which polymers in general are formed into usehil articles and on the mechanical properties, ie, rigid, flexible, or mbbery, of the final product. AH commercial polymers used for molding, extmsion, etc, fit into one of these six classifications the thermoplastic elastomers are the newest. 

Many mechanical properties are dependent on the density of cross-links and on the rigidity of the molecules between cross-links. It has already been shown that cross-link intensity may be controlled by varying the ratio of unsaturated to saturated acids whereas rigidity is to a large extent determined by the structure of the saturated acid employed. 

Mechanical properties are typical of a rigid plastics material and numerical values (Table 30.2) are similar to those for poly(methyl methacrylate). Although thermosetting, it has a low heat distortion temperature ( 80°C) and is not particularly useful at elevated temperatures. 

Mechanical properties. Properties commonly of importance here are rigidity, creep resistance, strength and toughness. For some applications resistance to repeated flexing or abrasion may be critical. 

The cast irons usually have a ferrite-pearlite structure, which determines its mechanical properties. The ferrite content determines the cast iron s viscosity, while the pearlite content determines its rigidity and strength. 

ABS has a specific gravity of 1.03 to 1.06 and a tensile strength in the range of 6 to 7.5 X 10 psi. These polymers are tough plastics with outstanding mechanical properties. A wide variety of ABS modifications are available with heat resistance comparable to or better than polysulfones and polycarbonates (noted later in this section). Another outstanding property of ABS is its ability to be alloyed with other thermoplastics for improved properties. For example, ABS is alloyed with rigid PVC for a product with better flame resistance. 

A large number of SAHs described in the literature combine synthetic and natural macromolecules in the network structure. The natural components are usually starch, cellulose, and their derivatives. It is assumed that introduction of rigid chains can improve mechanical properties (strength, elasticity) of SAH in the swollen state. Radical graft polymerization is one of the ways to obtain such SAH. 

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