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US 4,536,520 AGranted
Polyphosphazene foam process
AssigneeEthyl Corporation
InventorWarren B. Mueller
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Abstract
Foamed polyphosphazene articles having consistent appearance and physical properties are made by masticating a mixture of high molecular weight linear polyphosphazene, a curing agent (e.g., sulfur), an accelerator, a blowing agent and optionally fillers, processing aids and the like until the temperature of the composition rises to a pre-determined level. Mixing is stopped and the composition is shaped, heated to pre-cure and then heated to activate the blowing agent and complete the cure.
Claims23
A process for making a polyphosphazene foam having consistent appearance and physical properties, said process comprising:
- (A) forming a composition comprising a substantially linear high molecular weight polyphosphazene gum, a curing agent, a blowing agent and optionally a plasticizer, an inorganic filler, an accelerator and processing aids,
- (B) masticating said composition to form a substantially homogenous blend while measuring the temperature of said composition undergoing mastication and continuing said masticating until said temperature rises to a pre-determined level up to about 71.degree. C. and then stopping said masticating,
- (C) forming the resultant masticated composition into a shaped composition and
- (D) heating said shaped composition in an unconfined environment to a temperature which activates said blowing agent causing said shaped composition to expand into a foamed composition and completes curing of said foamed composition.
1 more element
Dependencies are inferred from the claim text.