Preparation of Novel Polyamide 6 Blends Made by Reactive Extrusion Compounding
The preparation of polymer blends is normally undertaken by mixing polymers in the melt state, typically in a compounding extruder, whereby the applied shear can be varied and hence the blend microstructure controlled. In immisicible blends, which are thermodynamically unstable, phase morphology can be further modified through the use of compatibilising additives, such as block copolymers, which generally leads to improved physical properties. Compatibilisation can also be achieved by reactive modification of one or more of the polymer phases, including chemical changes to the polymer structure. This paper discusses a novel approach to the preparation of polymer blends, through the in-situ polymerisation of monomer in the presence of a secondary polymer phase during passage through a co-rotating twin-screw extruder. When prepared in this manner, not only can the molecular mass of the polymerising monomer be influenced, but there is the potential for improved compatibility in the blend, possibly arising from chemical interaction between the phases or the formation of interpenetrating network structures. Furthermore, the phase microstructure in the blend can be strongly affected by the mixing conditions employed inside the compounder, in particular the levels of shear generated, through adjustment of screw profile and operating conditions. This approach to reactive compounding will be illustrated with reference to the preparation and characterisation of polyamide 6 (PA6) blends, by polymerisation of ∊-caprolactam in the presence of polypropylene (PP) and ethylene-propylene rubber (EPR).
KeywordsFlexural Modulus Formic Acid Solution Reactive Extrusion Industrial Research Institute Reaction Blend
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