Compatibilization of Polymer Blends

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Macosko - Abstract - 9527940 Immiscible polymer-polymer blends are a growing part of the polymer industry. They can offer synergistic properties, the best features of both components. They also provide a means for the recycling of mixed polymer waste. Because the component polymers are immiscible, their blends must by stabilized against coalescence. To obtain the desired properties, the minor component must by well dispersed and its size and shape controlled, typically at the submicron scale. To achieve this dispersion level, blends are usually prepared in a twin screw extruder and block or graft copolymers are added to compatibilize the blend, i.e. to aid in dispersion and prevent coalescence. These copolymers are expected to reside in the interface between the two components also aiding mechanical adhesion. There are two ways to add copolymers to a blend: (1) Synthesize the block copolymers in a separate step and then add it with the other components during blending; and (2) Create the block or graft copolymer in situ, ruing the blending process by coupling reactions across the interface between the components. In this project, several strategies for making pre-made copolymers more effective are explored. The objectives of the research program are: 1. Develop a model for morphology generation during polymer melt blending that accounts for interfacial stabilization via reactive coupling. 2. Establish the competitive advantage to reactive blending versus addition of pre-made block copolymer. 3. Apply results of 1 and 2 to isotactic polypropylene. 4. Evaluate the effects of optimized two-phase morphology on mechanical properties. 5. Establish viable means of producing functional polymers in usable quantities. 6. Quantify the role of interfacial thickness and reaction kinetics on the efficiency of reactive blending.