Reactively compatibilized starch-based renewable polymer blends

Starch-based polymeric materials offer a renewable, economical alternative to existing petroleum based, non-renewable or costly biodegradable polymeric materials. We present the development and characterization of two phase blends of plasticized starch (PLS) and polypropylene (PP) compatibilized via an interfacial chemical reaction.;Starch is an abundant, naturally occurring polysaccharide that is obtained from various plant sources. Having three hydroxyl groups per glucose monomer unit, starch is an inherently multifunctional polymer. When starch is blended with another polymer, such functionally can be used to reactively compatibilize the two phase system. We first examine the effects of multifunctional reactive compatibilization in model immiscible polymer blends and compare them to compatibilization using diblock copolymers. We study the rheological and morphological effects of the crosslinked interface and investigate the effects of varying the reactive compatibilizer concentration and the homopolymer loading.;We next develop a processing methodology and conduct a systematic characterization study of PLS and PP blends. Based on the result of our model blend study, multifunctional reactive blending was employed using maleated polypropylene (MAPP). The maleic anhydride functional groups are able to react with hydroxyl functional starch, creating a compatibilized system. The addition of layered silicate to the PLS/PP blends was employed to mitigate the decline in mechanical properties as starch content increased.;At sufficiently high plasticized starch loadings, the maleated polypropylene domains acted as physical crosslinking sites. The processing, blending, compatibilization and characterization of plasticized starch resulted in a material with properties apt for several elastomeric applications, such as rubber feet for electronic devices. The challenges of using plasticized starch as an elastomer are also discussed.;Lastly, we present a comparative life cycle assessment of plasticized starch and polypropylene. The system boundary of this assessment is defined to be "cradle to gate" in which we analyze the system from raw material extraction to the final production of a polymer pellet.