Kj. Ryan et al., Ultra-high-molecular-weight functional siloxane additives in polymers. Effects on processing and properties, J VINYL A T, 6(1), 2000, pp. 7-19
Two new types of solid siloxane additives for plastics are described which
give improved benefits compared to previous silicone additives. Ultra-high-
molecular-weight (UHMW) siloxanes are used in the new additives; traditiona
l silicone plastic additives have used much lower molecular-weight silicone
s. The siloxane is converted into solid forms, either masterbatch pellets o
r powders, that are easy to feed, or mix, into plastics during compounding,
extrusion, or injection molding.
Ultra-high-molecular-weight siloxanes can be compounded into masterbatch pe
llets at higher siloxane concentrations than previously possible, e. g., up
to 50%. They impart improved processing and release, lower coefficient of
friction, and broader performance latitude compared to conventional lower-m
olecular-weight silicones. These benefits can be delivered at reduced silox
ane levels with increased concentration at the surface interface with a new
functionalized UHMW siloxane which provides unique surface segregation cha
racteristics.
Ultra-high-molecular-weight siloxanes have been formulated into powders tha
t can also act as processing aids and mechanical property modifiers for hig
hly filled polymers such as fire-retardant systems.
This paper uses polyolefins as a model. However, many of the effects shown
in polyolefins have also been seen in other resin systems.