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preface to fifteenth edition

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10.10 SECTION 10<br />

Key properties of alkyds are dimensional stability, colorability, and arc track resistance. Chemical<br />

resistance is generally poor.<br />

10.3.4 Alloys<br />

Polymer alloys are physical mixtures of structurally different homopolymers or copolymers. The<br />

mixture is held <strong>to</strong>gether by secondary intermolecular forces such as dipole interaction, hydrogen<br />

bonding, or van der Waals’ forces.<br />

Homogeneous alloys have a single glass transition temperature which is determined by the ratio<br />

of the components. The physical properties of these alloys are averages based on the composition<br />

of thealloy.<br />

Heterogeneous alloys can be formed when graft or block copolymers are combined with a compatible<br />

polymer. Alloys of incompatible polymers can be formed if an interfacial agent can be found.<br />

10.3.5 Allyls<br />

10.3.5.1 Diallyl Phthalate (and Diallyl 1,3-Phthalate). These allyl polymers are prepared from<br />

These resulting polymers are solid, linear, internally cyclized, thermoplastic structures containing<br />

unreacted allylic groups spaced at regular intervals along the polymer chain.<br />

Molding compounds with mineral, glass, or synthetic fiber filling exhibit good electrical properties<br />

under high humidity and high temperature conditions, stable low-loss fac<strong>to</strong>rs, high surface<br />

and volume resistivity, and high arc and track resistance.<br />

10.3.6 Cellulosics<br />

10.3.6.1 Cellulose Triacetate. Cellulose triacetate is prepared according <strong>to</strong> the following reaction:<br />

Because cellulose triacetate has a high softening temperature, it must be processed in solution. A<br />

mixture of dichloromethane and methanol is a common solvent.<br />

Cellulose triacetate sheeting and film have good gauge uniformity and good optical clarity. Cellulose<br />

triacetate products have good dimensional stability and resistance <strong>to</strong> water and have good<br />

folding endurance and burst strength. It is highly resistant <strong>to</strong> solvents such as ace<strong>to</strong>ne. Cellulose<br />

triacetate products have good heat resistance and a high dielectric constant.<br />

10.3.6.2 Cellulose Acetate, Propionate, and Butyrate. Cellulose acetate is prepared by hydrolyzing<br />

the triester <strong>to</strong> remove some of the acetyl groups; the plastic-grade resin contains 38 <strong>to</strong> 40%

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