Polybutylene terephthalate behavior

Cheng, S. Z. D., Pan, R. and Wunderlich, B Thermal analysis of polybutylene terephthalate for heat capacity, rigid-amorphous content, and transition behavior, Makromol. Chem., 189, 2443-2458 (1988). 

Polybutylene terephthalate PBT Rigid, heat resistant, good electrical insulating behavior, dimensional accuracy... 

Solubility tests permit at least a tentative identification of the components also in polymer blends. Blends of ABS and polycarbonate are soluble in most polar solvents. Solubility in tetrahydrofuran and methyl ethyl ketone demonstrates the absence of polyolefins in such blends and the presence of aromatic polyesters or of polyamides can also be excluded. On the other hand, generally they may contain such highly soluble polymers as polystyrene, PVC, ABS, or polymethacrylates. However, blends that contain polybutylene terephthalate or polyethylene terephthalate do not dissolve in the usual solvents, but require m-cresol, which can he a clear indication that aromatic polyesters are present. Polyolefins dissolve at high temperatures, at least 110 °C, in toluene and p-xylene, and this behavior is characteristic of blends that contain polyethylene or polypropylene. 

Electron radiation at a radiation dose of 365 kGy causes a shift in glass transition temperature of crosslinkable polybutylene terephthalate from 53 (without irradiation) to 70 °C. The crosslinked polybutylene terephthalate becomes stiffer and slightly brittle. Its long-term behavior is not impaired by irradiation at 365 kGy, Figure 5.146 [739]. With increasing irradiation and/or crosslinking, its melt temperature decreases. 

Figure 5.146 Long-term behavior of irradiated and non-irradiated crosslinkable, glass fiber-reinforced polybutylene terephthalate [739]...

The example of glass fiber-reinforced PA 6 shows that the thermal-mechanical behavior of polyamide 6 and polybutylene terephthalate can be improved by electron irradiation so that the material can withstand an industrial soldering process at a temperature of 255 °C (such as used in lead-free soldering) [807], [720]. Figures 5.250 and 5.251 illustrate this by two examples. 

Copolymers of the polybutylene adipate-co-terephthalate type with a molar fraction of terephthalate of 42 mol-%, biodegrade completely to form compost in twelve weeks, whereas products with 51 mol-% of molar fraction of terephthalate show a percentage of biodegradation of less than 40% (42). This different behavior was attributed to the formation of a higher number of butylene terephthalate sequences with a length greater than or equal to 3, which are less easily biodegradable. 

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