Degradation Of Some Polymer Blends

Blends of PVA with PVC, PMMA and PS and PS/PMMA, thatcover the entire compositional range have been subjected tooutdoor weathering, thermal oxidation and ultraviolet irradiation.With the application of infra-red technique it was possible todetect any structural changes taking place. With the aid ofInstron testing instrument it was possible to find out themechanical modifications that have taken place.The present work investigates the effect of a secondpolymer on the weathorability of another. The author hasobserved that in all the cases investigated there was interactionbetween the dissimilar molecular chains, at least atthe phase boundaries, for the two-phase systems. Theseinteractions which may be intermolecular or intramolecularare observed in most cases to have deliterous effects on thestructural stability and mechanical properties of the polymers.In a few cases, the interaction reduced the vulnerability ofeither or both homopolymers to weathering.From the studies it has been observed that PMMAstabilises PVA against outdoor weathering and oven aging,while PVA stabilizes PMMA against ultraviolet degradation.For the PVA/PVC blends general deterioration of property wasobserved on blending with PVA destabilizing PVC and viceversa, with the effect of PVC on PVA being more pronounced.For the PVA/PS blends, although rigidity was observed toincrease with increase in PS in the blends, the presence ofPVA was observed to cause general deterioration of mechanicalproperties, with a minimum in tensile strength, modulus andpercentage elongation at 30% PVA in the blends. Vulnerabilityto thermal degradation was also observed to increase withincrease in PVA in the blend. PMMA was observed to destabilizePS to outdoor weathering and on thermal aging all the blendshad lower induction periods than the homopolymers.From morphological studies, PVA/PMMA and PS/PMMA werefound to be compatible while PVA/PVC and PVA/PS were incompatible

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