Structural changes as a result of processing in thermoplastic bloodmeal

Abstract

Bloodmeal (BM) can be thermoplastically processed resulting in a material with good mechanical properties by using a correct combination of additives. In this article, combinations of water, sodium sulfite (SS), sodium dodecyl sulfate (SDS), and urea were compounded with BM, and water absorption, solubility, thermal stability, and protein secondary structure were assessed. Thermal stability of processed plastics was reduced when using 2 or 3 pphbm (parts per hundred parts BM) SS and 20 pphbm urea, mostly indicative of a reduction in covalent crosslinking. SS was required for chain mobility during processing, however, without sufficient plasticization degradation will occur instead of melt formation. SDS further improved processability and consolidation leading to increased water absorption and solubility, indicative of a reduction in chain interactions. It was found that BM proteins are highly denatured and thermoplastic processing reduced ordered structures further. Additional minor structural changes occurred as a result of reduced covalent and noncovalent interactions after processing. It was concluded that the increase in water absorption and solubility was due to changes in intermolecular and intramolecular interactions, rather than substantial structural changes. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Treatments of protein for biopolymer production in view of processability and physical properties: A review

“…Sodium sulfite assisted in forming a flowable melt with plasticizer (water) and other chemical additives. Sodium sulfite was further observed to cause significant changes in blood meal–based biopolymer water absorption, mechanical properties, thermal stability, and injection‐molding performance . Sodium sulfite was also used as a thermal processing aid for blending soy protein with other synthetic polymers, for example, poly(butylene adipate‐co‐terephthalate) and PLA …”

“…Increasing urea content resulted in decreased tensile strength and Young's modulus and increased elongation of the biopolymer. However, the amount of urea should be carefully controlled because increasing the level of urea reduced the onset of thermal degradation like sodium sulfite, causing a reduction in thermal stability …”

“…The blood meal could even be processed by injection molding with the addition of SDS and urea. 21 SDS had drawbacks too, such as increased water absorption and solubility after processing 20 and a permanent reduction in transition temperatures, 37 as compared with the unmodified blood meal, whose glass-transition temperature was restored upon drying.…”

“…However, the amount of urea should be carefully controlled because increasing the level of urea reduced the onset of thermal degradation like sodium sulfite, causing a reduction in thermal stability. 20 The effects of the addition of salts from the Hofmeister series on hydrophobic interactions between zein and salts were evaluated. 40 The addition of NaI and NaSCN altered the properties of viscoelastic materials made from zein, rendering them softer and more extensible, as did urea and ethanol.…”

Short‐Term Viscoelastic Properties of Bloodmeal‐Based Thermoplastics

“…2 With these additives, bloodmeal can be converted into a thermoplastic material that can be extruded and injection molded. 6 While the combined effect of these additives reduces crosslinking (either physical or chemical), increasing chain mobility, 7 high processing temperatures, and specific mechanical energy input can cause excessive degradation and cross-linking in proteins. 5 For example, degradation at injection molding temperatures above 130 • C negatively impacts on the mechanical properties of soy protein/starch blends.…”