Polystyrene thermal properties

Polystyrene can be exceptionally crosslinked, leading to a tough and transparent material with improved electrical and thermal properties used as a dielectric material. Table 4.34 displays examples of crosslinked polystyrene properties. The data cannot be used for designing. 

On mechanical rather than thermal properties, plastics which were harder were also more difficult to cut and to fabricate satisfactorily. Chemically, plastics which resisted organic solvents were also more difficult to print safely and with good results, and so forth. Often, in practice, intractable properties were modified to the required degree by the inclusion of small amounts of other monomers (vinyl acetate in vinyl chloride a-olefins in polypropylene, etc.)—just as an unwanted property like brittleness in polystyrene was ameliorated by adding to it styrene-butadiene. 

Table 10.1 Physical properties of commercial extruded polystyrene foams ASTM C578 - Standard for Rigid, Cellular Polystyrene Thermal Insulation... 

Before BASF investigated this product, Quirk and Hsieh [1], Yuki and coworkers [2,3] and Fischer [4] carried out investigations with this monomer. The first two used the anionic polymerization mechanism and Fischer tried to copolymerize this monomer using free radical polymerization. In the latter case the yields were very low. The use of S/DPE blocks in thermoplastic elastomers [5] has also been briefly described. Some of the work carried out at BASF has been published in a recent review article [6], Owing to the enhanced thermal properties of this copolymer in comparison with atactic polystyrene - the glass transition temperature increases up to 180 °C, depending... 

Atactic polystyrene (aPS) is clear, transparent and easily fabricated, and has reasonable mechanical and thermal properties but is slightly brittle and softens near 100 °C. It is readily attacked by a large variety of solvents, including dry-cleaning agents. Its stability to outdoor weathering is poor it turns yellow and... 

Polymerization of styrene in microemulsions has produced porous solid materials with interesting morphology and thermal properties. The morphology, porosity and thermal properties are affected by the type and concentration of surfactant and cosurfactant. The polymers obtained from anionic microemulsions exhibit Tg higher than normal polystyrene, whereas the polymers from nonionic microemulsions exhibit a lower Tg. This is due to the role of electrostatic interactions between the SDS ions and polystyrene. Transport properties of the polymers obtained from microemulsions were also determine. Gas phase permeability and diffusion coefficients of different gases in the polymers are reported. The polymers exhibit some ionic conductivity. 

Table 1 Molecular weights, polydispersity indices, compositions and thermal properties of homo-and block copolymers. The molecular weights were determined via SEC using polystyrene calibrations, the compositions via H-NMR and the thermal properties from DSC measurements. The melting enthalpies are normalized to their weight fractions...

In the composite, the magnesium hydroxide is selectively dispersed in the PPE domains with an average domain size of about 1.5 p,m. The surface treatment of magnesium hydroxide by dodecanoic acid with polystyrene-fetoci -poly(ethylene-co-butylene)-i /ocA -polystyrene as a compafibilizer significantly improves the macroscopic mechanical and thermal properties of the composites in a synergetic manner. 

The mutual repulsion between substituents may cause some displacement. As a result, the plane of symmetry is bent in the form of a helix. This occurs also in biopolymers (double-helix of deoxyribonucleic acid (DNA)). Different stereoisomers have different mechanical and thermal properties. For example, atactic polystyrene is an amorphous polymer whereas syndiotactic polystyrene is a crystalline substance. The chemical design of macromolecules determines their properties as extent of crystallization, melting point, softening (glass transition temperature), and chain flexibility which in turn strongly influence mechanical properties of the materials. 

The only effects on the thermal properties seen from the incorporation of a fire retardant additive occurs in the case of high-impact polystyrene (HIPS) where, as shown in Table 8.4, the incorporation of a fire retardant leads to a decease in expansion coefficient and, in the case of the polyesters, where the incorporation of a fire retardant produces a small improvement in heat distortion temperature. 

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