Page 159 - Engineering Plastics Handbook

132 Engineering Plastics

O O
C CO (CH ) O
2 4
n
Figure 7.1 The chemical structure of polybutylene
terephthalate.

commercially available. PBT can be tailored to various applications by
blending it with other components (PBT/PC, PBT/PET, PBT/ABS).
Table 7.1 shows a list of suppliers of PBT compounds with their trade
names. The thermoplastic resins cover a range, such as PBT, PC,
polyamide, polyacetal, and modified PPO. They can be classified in accor-
dance with their crystalline state: semicrystalline (PBT, polyamide, and
polyacetal) and amorphous (PC and modified PPO). Semicrystalline ther-
moplastic shows balanced physical properties as well as heat and chemi-
cal resistance. Among the semicrystalline engineering polymers,
polyacetals exhibit the highest crystallinity, and this structure shows high
stiffness, good creep resistance, and a low friction coefficient. While poly-
acetal has balanced mechanical properties, it shows lower melting point
and flammable moiety compared to PBT and polyamides. The main dif-
ference between polyamide and PBT is the moisture absorption rate. The
higher moisture absorption rate of polyamide is unfavorable to some appli-
cations that require high dimensional stability. For low moisture absorp-
tion, PBT resin has a more consistent property that shows little change
in dimensional, physical, and electrical properties as a function of envi-
ronmental factors. In Table 7.2, some important properties for various
semicrystalline engineering plastics are summarized.

Chemistry of PBT
PBT polymer is commercially produced by polycondensation reaction
between 1,4-butanediol and terephthalic acid (TPA) or 1,4-butanediol and

TABLE 7.1 Manufacturers and Trade
Names of PBT Resins
Manufacturer Trade name

BASF Ultradur
Bayer Pocan
DSM Arnite
DuPont Crastin
GE Advanced Materials Valox
LG Chem, Ltd. Lupox
Mitsubishi EP Novadur
Ticona Celanex
Toray Toray PBT
WinTech Polymer Duranex