Page 169 - Engineering Plastics Handbook

142 Engineering Plastics

TABLE 7.6 Chemical Resistance of PBT
Chemical Concentration (%) 23°C 60°C 80°C
Acetic acid 5 O P X
Acetic acid — O P X
Brake fluid — O O —
Cresol — X X X
Diesel oil — O O O
Ethanol — O P X
Ethyl acetate — O X —
Freon 11 — O — —
Glycerol — O O P
Heptane — O O O
Hexane — O O O
Hydraulic oil — O O —
Lubricant — O O O
Methanol — O P —
Mineral oils — O O O
Motor oils — O O P
NaOH 10 X X X
Octane — O O O
Olive oil — O O O
Paraffin oil — O O O
Petroleum — O O O
Petrol, regular — O O O
Phenol — X X X
Seawater — O O X
Silicone oils — O O O
NaCl 10 O O X
5 O O X
H 2 SO 4
25 O P X
H 2 SO 4
Toluene — O P X
Vegetable oils — O O O
Xylene — O X X
O: resistant, no or slight weight change; P: partially resistant, extended use of the
chemical may cause crack or craze; X: unstable, remarkable decrease in mechanical
properties.
SOURCE: Lupox PBT brochure and data sheets [20].

the polyester chain, thus lowering the molecular weight of the PBT. Above
the melting point of the PBT, the hydrolysis reaction proceeds very rapidly,
even within a few seconds. If undried PBT with enough moisture content
is exposed to melt processing conditions, molecular weight or viscosity will
drop and properties will be lost to some degree. However, there is not
enough water present at this high temperature to give catastrophic degra-
dation, but by losing PBT molecular weight in processing wet resin, one is
sacrificing some of the ultimate part performance. This shows the needs to
melt-process PBT at very low moisture levels. Moisture content below
0.03% prior to melt processing is generally recommended for PBT.