Viscous behavior of PS, PP, and ABS in terms of temperature and pressure-dependent hole fraction

Effect of Free Volume on Curcumin Release from Various Polymer-Based Composite Films Analyzed Using Positron Annihilation Lifetime Spectroscopy

This work reports the effects of free volume on curcumin release in various polymer-based composite films. Curcumin-reinforced biocomposite films were fabricated with natural biopolymers (carrageenan and chitosan) and bioplastics (poly(lactide) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT)) via the solvent casting method. The curcumin release test was performed using an aqueous medium, and it was found that it was released the fastest in the carrageenan film, followed by the chitosan, PLA, and PBAT films, presumably owing to the dissimilarity of the polymer matrix. The free volume of the polymer films was determined using positron annihilation lifetime spectroscopy (PALS) to understand the release phenomena of curcumin. The free volume fraction was varied and reliant on the type of polymer, with the highest in the PBAT-based film followed by the PLA-, chitosan-, and carrageenan-based films. The free volume method helps analyze the release of bioactive compounds in a polymer matrix and may help to achieve a better understanding of the release of bioactive compounds.

Preparation and Properties of Wood Plastic Composites with Desirable Features Using Poplar and Five Recyclable Plastic Wastes

This study evaluated the mechanical and hydrophobic properties of wood plastic composites (WPC) prepared by the hot molding approach incorporating five different recycled plastics and poplar flour. The WPC showed excellent tensile strength (36.9 MPa) and flexural strength (44.7 MPa) associated with good hydrophobicity, and the excellent properties of WPC could be due to the application of hot pressing which improved the amount of hydroxyl groups and reduced the crystallinity of WPC. The WPC also revealed a strong and hydrostable structure and negligible emission of formaldehyde during the preparation process. Overall, the WPC could be used to substitute traditional wood-based panels as potential furniture material, hence achieving sustainable utilization of plastic wastes.

Pressure Equilibrium Time of a Cyclic-Olefin Copolymer

Integrative simulation techniques for predicting component properties, based on the conditions during processing, are becoming increasingly important. The calculation of orientations in injection molding, which, in addition to mechanical and optical properties, also affect the thermal shrinkage behavior, are modeled on the basis of measurements that cannot take into account the pressure driven flow processes, which cause the orientations during the holding pressure phase. Previous investigations with a high-pressure capillary rheometer (HPC) and closed counter pressure chamber (CPC) showed the significant effect of a dynamically applied pressure on the flow behavior, depending on the temperature and the underlying compression rate. At a constant compression rate, an effective pressure difference between the measuring chamber and the CPC was observed, which resulted in a stop of flow through the capillary referred to as dynamic compression induced solidification. In order to extend the material understanding to the moment after dynamic solidification, an equilibrium time, which is needed until the pressure signals equalize, was evaluated and investigated in terms of a pressure, temperature and a possible compression rate dependency in this study. The findings show an exponential increase of the determined equilibrium time as a function of the holding pressure level and a decrease of the equilibrium time with increasing temperature. In case of supercritical compression in the area of a dynamic solidification, a compression rate dependency of the determined equilibrium times is also found. The measurement results show a temperature-invariant behavior, which allows the derivation of a master curve, according to the superposition principle, to calculate the pressure equilibrium time as a function of the holding pressure and the temperature.

Hole Fraction Dependence on Linear Viscosity of PS, PP and ABS

A linear dependency of zero shear, constant shear-rate and constant shear-stress viscosities with temperature and hole fraction (“thermo-occupancy” function) was derived for polyacrylonitrile-butadiene-styrene (ABS), polypropylene (PP) and polystyrene (PS). The relation of viscosity parameters, such as transmission coefficient and a measure of activation energy coefficient, with shear-rate and shear-stress was also investigated and some conclusions on the differences for the studied polymers were discussed. In particular, it was found that, for all materials, the derivative of logarithm of viscosities at zero shear, constant shear-rate and constant shear-stress decreases with decreasing rate with the hole fraction.