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

1
Department of Chemical Engineering, Masdar City Campus, Khalifa University, Abu Dhabi 54224, UAE
2
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
3
Department of Chemical Engineering, Biotechnology and Environmental Technology, University of Southern Denmark, 5230 Odense, Denmark
*
Authors to whom correspondence should be addressed.
Polymers 2019, 11(4), 722; https://doi.org/10.3390/polym11040722
Received: 19 February 2019 / Revised: 22 March 2019 / Accepted: 27 March 2019 / Published: 19 April 2019
(This article belongs to the Special Issue Natural Compounds for Natural Polymers)
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Abstract

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—milk proteins—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 (11–14 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 1–2 MPa (the best 30:70 sample exhibited 3.8 ± 0.2 MPa and the best 20:80 sample exhibited 1.9 ± 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 ± 6.2 °C and the WPC-based samples are stable up to 273.0 ± 3.4 °C. View Full-Text
Keywords: protein-based polymer; copolymerization; whey protein; mechanical properties; PEGMA protein-based polymer; copolymerization; whey protein; mechanical properties; PEGMA
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Chalermthai, B.; Chan, W.Y.; Bastidas-Oyanedel, J.-R.; Taher, H.; Olsen, B.D.; Schmidt, J.E. Preparation and Characterization of Whey Protein-Based Polymers Produced from Residual Dairy Streams. Polymers 2019, 11, 722.

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