Page 306 - Engineering Plastics Handbook

266 Engineering Plastics

Figure 12.11 Polyamide-imide compounds are used in rotating indus-
trial equipment.

from a polyamide-imide compounded with patent-pending additives [18]
are able to withstand the high frictional heat which occurs in sewing
machines that run at high speeds, 4000 to 9000 switches per minute,
e.g., without bobbin lubrication. Hooks made from polyamide-imide
don’t stick or slip, and they need minimal adjustment. Unlike stainless-
steel components, which have no flexibility, parts made from polyamide-
imide have enough give to allow slight variances between upper and
lower thread tensions, allowing the machines to be set at the lightest
possible tension without losing stitch integrity.

Compressor vanes. Polyamide-imide compounds are being used in a
number of rotating industrial equipment applications. One particular
area of interest is in rotary vane compressors. Previously the vane mate-
rials were made from a phenolic composite construction. Although more
expensive from a material of construction perspective, a polyamide-imide
compound was chosen due to a dramatic extension in life and a lower
lubrication requirement, both of which reduce maintenance and the over-
all operating cost of the compressor. In addition the compressors can
operate at a higher discharge pressure due to polyamide-imide’s higher-
temperature capability.

Automotive transmission components: seal rings, thrust washers, check balls.
Many automatic transmissions on the road these days contain multiple
components manufactured from injection-moldable polyamide-imide