Protein‐based thermoplastics resemble semi‐crystalline polymers, suggesting the occurrence of a glass transition (Tg) and melting point. Denaturing a protein's native structure is often called melting, but this does not necessarily imply complete unfolding into a fully amorphous structure as true melting would. Protein secondary structures, such as α‐helices and β‐sheets, can remain after denaturing, stay intact above the Tg and do not necessarily melt at typical processing temperatures. This implies that consolidation of aggregated protein particles into a macroscopically monolithic material depends on inter‐chain interactions in the amorphous phase and on newly formed secondary structures. Structural relaxations and transition temperatures of the amorphous phase are influenced and constrained by the presence of these secondary structures as well as heavily influenced by plasticizers.
Blood meal is a high protein, low value by‐product of the meat processing industry that can be converted into a thermoplastic material by extrusion with a combination of a surfactant, urea, a reducing agent, water, and plasticiser. Changes in protein structure after each processing step (mixing with additives, extrusion, injection molding, and conditioning) were explored using synchrotron FTIR microspectroscopy. Blood meal particles were found to have higher β‐sheet content around the perimeter with a randomly structured core. α‐Helices were either located near the core or were evenly distributed throughout the particle. Structural rearrangement consistent with consolidation into a thermoplastic was seen after extrusion with processing additives, resulting in reduced α‐helices and increased β‐sheets. Including triethylene glycol as a plasticiser reduced α‐helices and β‐sheets in all processing steps. At all processing stages, regions with increased β‐sheets could be identified suggesting blood meal‐based thermoplastics should be considered as a semicrystalline polymer where clusters of crystalline regions are distributed throughout the disordered material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Purpose The purpose of this research was to develop a nonrenewable energy and greenhouse gas emissions ecoprofile of thermoplastic protein derived from blood meal (Novatein thermoplastic protein; NTP). This was intended for comparison with other bioplastics as well as identification of hot spots in its cradle-to-gate production. In Part 1 of this study, the effect of allocation on the blood meal used as a raw material was discussed. The objective of Part 2 was to assess the ecoprofile of the thermoplastic conversion process and to compare the cradle-to-gate portion of the polymer's life cycle to other bioplastics. Methods Inventory was collected to aggregate nonrenewable primary energy use and greenhouse gas emissions. Data were collected from a variety of sources including published papers, reports to government agencies, engineering models and information from a single blood meal production facility. Several assumptions regarding the thermoplastic conversion process were evaluated by way of a sensitivity analysis. Results The allocation procedure chosen for the impacts of farming and meat processing had the greatest effect on results. Excluding farming and meat processing, blood drying had the greatest contribution to nonrenewable energy use and GHGs, followed by the petrochemical plasticizer used. Other assumptions, such as scarcity of water or inclusion of pigments, although significant when considered for blood meal conversion to NTP alone, were found not to be significant when production of blood meal was included in the analysis. Qualitative differences were observed between NTP and other bioplastics. For example, the profiles of some other bio-based polymers were dominated by fermentation and polymer recovery processes. In the case of NTP, it is the production of the raw material used that is most significant, and thermoplastic modification has a relatively low contribution to GHGs and nonrenewable energy use. Conclusions For a truly attributional scenario, production of any ruminant animal products does have an associated GHG. Deriving this for blood meal on a mass-based allocation seems to indicate that NTP is less favorable than other cradle-to-gate bioplastic production systems from a global warming perspective.On the other hand, the motivation for developing the material in the first place was to make use of an existing waste product. If it is assumed that the magnitude of blood meal production is independent of fertilizer or plastics demand and, instead, reflects demand for major products such as meat, further development of NTP is justified.
Synchrotron-based Fourier-transform infrared (FTIR) spectroscopy was used to assess the effect of peracetic acid decolouring on the spatial distribution of secondary structures within particles of bloodmeal.
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