Polyarylates heat distortion temperature

Polyarylate It is a form of aromatic polyester (amorphous) exhibiting an excellent balance of properties such as stiffness, UV resistance, combustion resistance, high heat-distortion temperature, low notch sensitivity, and good electrical insulating values. It is used for solar glazing, safety equipment, electrical hardware, transportation components and in the construction industry. 

Figure 19.12 Relationship between the heat distortion temperature (HDT) (at 1.82 MPa) and Tg for the amorphous polyarylates of HBA/Ph-HQ or fBu-HQ/HQ/ BB and the crystalline polyarylate of Ph-HQ/BB [33]...

Table 19.5 Flexural moduli and heat distortion temperature data for substituted-HQs/BB polyarylates [19]. From Inoue, T. and Tabata, N., Mol. Cryst. Liq. Cryst., 254, 417-428 (1994), and reproduced with permission of Gordon and Breach (Taylor and Francis) Publishers...

The miscibility between polyarylate and PET may be further driven by transesterification reaction within the melt phase, which occurs slowly at T 280°C but more rapidly at T > 300°C [Robeson, 1985 Eguiazabal et al., 1991]. In any case, polyarylate can readily form transparent blends when the PET content is 30% and the melt blending done above 300°C. Hence by adjusting the melt blending conditions, PET can be used to lower the cost and improve the chemical resistance of polyarylate while maintaining an adequate level of transparency. The heat distortion temperature is, of course, sacrificed to some extent. Except for some improved chemical resistance, processability and cost the blend does not seem to offer any compelling advantages over polyarylate and hence its applications appear to be quite limited. 

Several companies have marketed polyarylates under the trade names U-polymer (Unitika of Japan), Arylef (Solvay of Belgium), Ardel (Union Carbide), and Arylon (Du Pont). These are noncrystallizing copolymers of mixed phthalic acids with a bisphenol and have repeat units of the type shown above. They are melt processable with Tg and heat distortion temperatures in the range of 150-200°C and have similar mechanical properties to polycarbonate and polyethersulfones (see later). 

Only a handful of polymers seemed viable candidates fluorocarbons such as poly(tetrafluoroethylene) (PTFE), polyesters such as poly(ethylene terephthalate) (PET), aromatic polycarbonates (PC), and polyarylates such as resorcinol polyary-late (RPA). Poly (methyl methacrylate) (PMMA) would be an attractive candidate, but its heat distortion temperature is less than the maximum service temperature. PTFE was already established as a PV front sheet material in flexible amorphous silicon modules. We observed that in flat roof applications, these modules sometimes developed corrosion spots due to cuts and punctures through the thin, soft PTFE. We desired a lower cost and mechanically more robust front film. 

Polyarylate (PAr), which is produced by the condensation polymerization of bisphenol-A and phthalic adds, is an amorphous, high-clarity polymw with high heat-distortion temperature, ultraviolet (UV) stability, inherent flame retardance, and good electrical propnties. Typical outdoor applications for PAr include solar collectors, safety devices, construction, and transportation, whereas indoors it finds application in electronic and electrical hardware. 

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