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Low Temperature Radical Initiated Crosslinking Mechanism of Polyarylenes

IP.com Disclosure Number: IPCOM000236127D
Publication Date: 2014-Apr-07
Document File: 2 page(s) / 203K

Publishing Venue

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Abstract

A new method of curing polyarylenes initiated by free radical reaction of quinhydrone is conceived. This curing mechanism initiated at lower temperature can minimize the degradation of polymer backbone structure. It is an established fact that polyarylenes, such as, polyphenylene sulfides, polyphenylene sulfones, polyphenylene sulfoxides, polyether sulfones, substituted paraphenylenes, or other polyphenylene derivatives can be cured by heat treatment. The purpose is to attain an elastomeric stable rubbery modulus above corresponding glass or melt transition temperatures so as to attain structural stability and prevent melting. Several papers and patents have reported curing mechanisms via degradation of the main polymer-backbone chain or cleavage of the substituent groups resulting in generation of free radicals for crosslinking. However, the chemistry involved in high temperature treatment of polymers can lead to oligomers that often lose the inherent chemical property of the starting polymeric material. The idea generated is to create free-radicals from a radical initiator at the phenyl ring of the polymer chain that can initiate cross-links between the two chains. To further accelerate the process a crosslinking agent can be used that can bridge radical linkages between the two polymer chains. Thus, similar level of crosslinking can be achieved at a lower temperature where the polymer curing is achieved without degrading the backbone. Hydrogen abstractors such as quinones can be used to generate radicals at the phenyl ring(s) at a lower temperature, and sulfur (S) can be used as a curative agent to accelerate this process. Since the main chain cleavage of the polyarylenes compounds can be inhibited at lower temperature, the chemical property of the resultant material is envisioned to be enhanced over that cured at higher temperatures. Cure kinetics was studied in a dynamic mechanical analysis (DMA) instrument at isothermal conditions and the storage modulus (G’) was found to be similar at a lower temperature with addition of quinhydrone (QH) in polyphenylene sulfide (PPS) along with the crosslinking agent (S). A combination of sulfur (S) and magnesium peroxide (MgO2) was found beneficial as MgO2 can serve additional crosslinking by generating the oxygen radical in the system. The resultant thermal derivative of MgO2 is MgO that may also acts as an activator for sulfur curing. Quinhydrone, by itself, was not found to be sufficient to achieve crosslinking at lower temperature.

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Low Temperature Radical Initiated Crosslinking Mechanism of Polyarylenes

A new method of curing polyarylenes initiated by free radical reaction of quinhydrone is conceived.  This curing mechanism initiated at lower temperature can minimize the degradation of polymer backbone structure.

It is an established fact that polyarylenes, such as, polyphenylene sulfides, polyphenylene sulfones, polyphenylene sulfoxides, polyether sulfones, substituted paraphenylenes, or other polyphenylene derivatives can be cured by heat treatment.  The purpose is to attain an elastomeric stable rubbery modulus above corresponding glass or melt transition temperatures so as to attain structural stability and prevent melting.  Several papers and patents have reported curing mechanisms via degradation of the main polymer-backbone chain or cleavage of the substituent groups resulting in generation of free radicals for crosslinking.  However, the chemistry involved in high temperature treatment of polymers can lead to oligomers that often lose the inherent chemical property of the starting polymeric material.  The idea generated is to create free-radicals from a radical initiator at the phenyl ring of the polymer chain that can initiate cross-links between the two chains.  To further accelerate the process a crosslinking agent can be used that can bridge radical linkages between the two polymer chains.  Thus, similar level of crosslinking can be achieved at a lower temperature where the polymer c...