Rheology and processing of bloodmeal-based thermoplastics

Abstract

The objective of this research was to determine the rheological properties and processing behaviour of NTP using capillary rheometry and batch mixing. These were evaluated at constant plasticiser content, but using three different ratios of water to plasticiser (triethylene glycol, TEG). Each of these was evaluated at 115, 120 and 125 ℃. It was shown that NTP is a non-Newtonian, shear thinning fluid. It was found that viscosity is highly dependent on water content; decreasing with increasing water content. At a shear rate of 15 s-1, the apparent viscosity for the reference formulation (60 parts water per hundred parts bloodmeal) was 2000 Pa.s compared to 7000 Pa.s for the formulation containing 30 parts water and 30 parts TEG (at 115 ℃). Viscosity decreased slightly with increasing temperature and the degree of non-Newtonian behaviour was mostly unaffected by temperature. The flow behaviour index, n, was found to be in the range 0.11 to 0.17, with no discernable temperature dependence. In the reference formulation, the total amount of plasticiser and ratio water to TEG was higher, which resulted in slightly different flow behaviour with respect to temperature. Batch mixing revealed that NTP crosslinks rapidly after about three minutes and was strongly dependent on temperature and mixing speed.