Page 179 - Engineering Plastics Handbook

152 Engineering Plastics

high impact properties. Automotive applications of PBT include door
mirror systems, brake unit components, housings and components for
ECU blocks and ABS units, door lock components, distributor caps and
rotors, ignition coils, sensor encapsulations, bumper back beam and fascia,
window garnish, and headlamp structures.

General engineering and replacement of
other materials
Its resistance to heat and chemicals, plus the wide range of coloring pos-
sibilities and good friction properties, enables PBT to be used in many
industrial components and consumer applications. In industry, PBT
resins are used for pump housings, impellers, functional parts of print-
ers and copying machines, tool housings, casings, and replacements for
metals in many types of load-bearing parts. PBT resins are noted for
their excellent flow characteristics in thin-wall moldings, close mold
tolerances, and high productivity with fast mold cycles.
The properties, processing characteristics, and competitive price of
PBT engineering plastics lead to high performance, lower cost, and
lower weight compared to die-cast metals and/or thermosetting resins.
The main advantages of PBT resins compared to thermosetting resins
are material reuse, design integrity, and productivities. Thermoplastic
molding components require less material, because scrap such as sprues,
runners, and failure parts can be reground and reused. With themo-
plastics, less processing time is needed due to faster cycle times and elim-
ination of the secondary operation of thermosetting resins. The high
rigidity with light weight, integrated design, and resistance to corrosion
and chemicals make PBT an ideal replacement material for a wide
range of industrial applications in place of die-cast metals. Among the
many successful replacements of other materials are housings and
covers, pump parts, motor parts, parts for electric drives, lamp parts,
and automotive parts. Table 7.10 illustrates the reasons for using PBT,
including replacement of other materials. The PBT thermoplastics have
characteristics of processing ease and good economics.

Conclusions
PBT is a very versatile and cost-effective resin that can be combined with a
wide range of additives to give a range of products for electrical, auto-
motive, and other applications. Annual growth rate of 6 to 8% is predicted,
and this is driven by many factors such as weight reduction, parts design
consolidation, and metal replacement. Among the other polyesters, the ben-
efit of PBT is an inherent fast-crystallizing kinetics, allowing for fast cycling
and easy processing properties in injection molding. PBT is outstanding for