Tuning compatibility and water uptake by protein charge modification in melt-polymerizable protein-based thermosets

The effects of charge state on water uptake and mechanical properties of thermoset protein-based copolymers were investigated. Superneutralization was shown to reduce the material's mechanical property variation with humidity.</jats:p

Development of a Rubber Recycling Process Based on a Single-Component Interfacial Adhesive

A simple and cost-effective adhesive-based rubber recycling process was designed as an alternative to devulcanization. Interfacial bonding between vulcanized and virgin rubbers is improved by incorporating adhesives and coating processes during rubber reblending and reducing interfacial defects that cause premature failure. In flat laminates, the bond strength between vulcanized and virgin materials doubles when a vulcanizing fluid and thin adhesive layer are introduced. These components are combined into single-component adhesives (SCAs), which improve bond strength sixfold over no treatment, using half the raw material as the multilayer adhesive. When SCAs are coated onto vulcanized rubber particles prior to reblending, the best rubbers exhibit nearly 50% increases in mechanical strength and toughness vs the untreated control and statistically identical extensibility; all treatments improved mechanical strength. This simple, inexpensive, and scalable process can be implemented with one step beyond standard reblending and curing, providing a promising alternative to devulcanization for polymer recycling

Preparation and Characterization of Whey Protein-Based Polymers Produced from Residual Dairy Streams

The wide use of non-biodegradable, petroleum-based plastics raises important environmental concerns, which urges finding alternatives. In this study, an alternative way to produce polymers from a renewable source&#8212;milk proteins&#8212;was investigated with the aim of replacing polyethylene. Whey protein can be obtained from whey residual, which is a by-product in the cheese-making process. Two different sources of whey protein were tested: Whey protein isolate (WPI) containing 91% protein concentration and whey protein concentrate (WPC) containing 77% protein concentration. These were methacrylated, followed by free radical polymerization with co-polymer poly(ethylene glycol) methyl ether methacrylate (PEGMA) to obtain polymer sheets. Different protein concentrations in water (11&#8211;14 w/v%), at two protein/PEGMA mass-ratios, 20:80 and 30:70, were tested. The polymers made from WPI and WPC at a higher protein/PEGMA ratio of 30:70 had significantly better tensile strength than the one with lower protein content, by about 1&#8211;2 MPa (the best 30:70 sample exhibited 3.8 &#177; 0.2 MPa and the best 20:80 sample exhibited 1.9 &#177; 0.4 MPa). This indicates that the ratio between the hard (protein) and soft (copolymer PEGMA) domains induce significant changes to the tensile strengths of the polymer sheets. Thermally, the WPI-based polymer samples are stable up to 277.8 &#177; 6.2 &#176;C and the WPC-based samples are stable up to 273.0 &#177; 3.4 &#176;C