2012 Annual Report
1a.Objectives (from AD-416):
To develop sugar beet pulp-based composite bioplastics. Engineering materials with high performance properties from poly(lactic acid) (PLA) containing a large volume of sugar beet pulp or other biomass residues (60 w% or more) will be scaled up. The proposal fits well into the Project Plan, Objective 4 entitled "Develop novel, value-added biodegradable engineering materials by extrusion processing". The ERRC and WSU scientists have demonstrated that polymeric diphenylmethane diisocyanate (pMDI), a chemical crosslinker, can be used as an effective interfacial modifier for SBP and PLA composites. The composites, even at SBP contents up to 40-50 wt%, still largely retain the high tensile strength of PLA. The proposed collaboration will allow the WSU team and ERRC to work together to optimize compounding and product manufacturing conditions for scale-up. The market for the end products are those requiring light weight-bearing materials, and materials with adjustable thermoconductivities and thermodiffusive properties.
1b.Approach (from AD-416):
In general, the compounding of PLA/SBP composites will be performed in two steps. At the first step, SBP will be modified with pMDI under anhydrous conditions. This process will be monitored by FI-ATR-IR and SEM. At the second step, the modified SBP will be co-extruded with PLA and pMDI. The ERRC team will conduct the bench-top study, screening a set of reaction parameters, such as temperature, reaction time, and the ratios of SBP to pMDI. The WSU team will scale up the experiments, using a large volume reactor (50L or more) and a twin-screw extruder. The WSU team will also conduct the structure examination and mechanical analysis.
Alternatively, the ERRC and WSU teams will work together to explore a new approach to combine the two steps of “surface modification” and “composite compounding” in one by the use of reactive extruder.
The collaboration has resulted in a series of composite materials from sugar beet pulp and poly(lactic acid) (PLA) or poly(butylene adiphate-co-terepthalate). These composites are totally biodegradable and possess tensile strength matching traditional petroleum-derived thermoplastics. Since sugar beet pulp content in the composites is up to 50%, the cost is competitive with thermoplastics currently in the marketplace. The mechanism by which pectin plays the key role in adhering PLA to SBP was evaluated using commercial pectin-extracted sugar beet pulp and then adding commercial sugar beet pectin to it. Two research papers were published, one student received a Ph.D. degree and was immediately hired by a company right after graduation and is now the key investigator of the company.