Page 178 - Engineering Plastics Handbook

Polybutylene Terephthalate (PBT) 151

Electrical and electronics
Electrical and electronics parts, which are becoming smaller and more com-
plex and have increasing functionality, require high-performance molding
materials. PBT is rigid, flame-resistant, and high-heat-resistant, and it has
dimensional stability and outstanding long-term electrical performance.
In some cases, PBT replaces thermosetting resins where good electrical
properties are required together with better impact strength and easy
processing in shorter cycle times with scrap reuse. Because of its high
flow property, which enables PBT to fill thin sections readily, and its ease
of processing, PBT is readily used in thin-wall connectors, bobbins, and
ignition parts, all requiring electric endurance, flammability, and a good
balance of strength and electric track resistance. Therefore it can also be
used in switches, relays, terminal boards, TV focus blocks, TV trans-
formers, DY, lamp sockets, and housings for electric parts. Parts molded
in PBT thermoplastics are not sensitive to moisture and retain their elec-
trical properties over a wide temperature range; their performance is main-
tained in almost all working conditions. Unfilled high-viscosity extrusion
grades are also used in optical fiber protective tubes, monofilaments, and
some sheath parts of cable wires.

Automotive
PBT resins are widely used for both exterior and under-the-hood parts of
automobiles. Automotive electrical and electronic components especially
are expanding at a high rate, which is driven by advanced technology
related to convenience, improved fuel efficiency, and safety improvement.
Automotive electrical components must function over a broad range of
temperatures while withstanding impact, vibration, and corrosive chem-
ical environments. In automotive electrical applications such as electrical
control units, antilock braking systems, ignition systems, plug connec-
tors, and air bag and engine control systems, PBT thermoplastics are
widely used for their high stability. PBT is outstanding for its high heat
resistance, good dimensional stability, low water absorption, and high
resistance to many chemicals, such as fuels and lubricants. These prop-
erties have made PBT an indispensable material in many applications in
automotive electronic engineering.
In other important automotive applications, increased requirements in
terms of surface appearance, low-temperature toughness, flowability, and
warpage properties have been met by PBT blends. Automotive exterior
parts such as door handles, mirror housings, window delta molding, and
sunroof frames must have an excellent surface finish, especially if they
are unpainted. For large exterior body parts such as bumpers, elastomer-
modified PBT/PC blends are used because of their surface appearance and