This article presents the effect of twin-screw extrusion processing parameters, including temperature and rotational speed of screws, on the structure and properties of four grades of polylactide (PLA). To evaluate the critical processing parameters for PLA and the possibilities for oxidative and thermomechanical degradation, Fourier-transform infrared spectroscopy (FT-IR), oscillatory rheological analysis, and differential scanning calorimetry (DSC) measurements were used. The influence of degradation induced by processing temperature and high shearing conditions on the quality of the biodegradable polyesters with different melt flow indexes (MFIs)was investigated by color analysis within the CIELab scale. The presented results indicate that considering the high-temperature processing of PLA, the high mass flow index and low viscosity of the polymer reduce its time of residence in the plastifying unit and therefore limit discoloration and reduction of molecular weight due to the degradation process during melt mixing, whereas the initial molecular weight of the polymer is not an essential factor.

The aim of this study was to develop a polyethylene/polyamide (R-PE/R-PA) regranulated product made from post-consumer wastes grafted with polyethylene-graft-maleic anhydride (PE-g-MAH) by reactive extrusion in a twin-screw extruder equipped with an external mixing zone. The compatibility effect of PE-g-MAH used as a modifier in R-PE/R-PA blends was evaluated by means of differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA), while the analysis of the chemical structure of this blend was carried out by Fourier transform infrared spectroscopy (FT-IR). The thermal properties, complex viscosity, and selected usage properties of R-PE/R-PA blends compatibilized with PE-g-MAH, i.e., density and water absorption, were evaluated. The morphology of the blends with and without the compatibilizer was observed by scanning electron microscopy. The R-PE/R-PA/MAH blend shows heterogenic structure, which is a result of the chemical reaction in reactive extrusion between functional groups of PE-g-MAH used as modifier and the end groups of R-PA6. The results show that the R-PE/R-PA blend with increased PE-g-MAH content showed increased hardness, stiffness, and ultimate tensile strength due to the increased degree of crystallinity. The increase in crystallinity is proportional to the improvement of the mechanical properties. Moreover, it is shown that 1 wt.% PE-g-MAH added to the R-PE/R-PA waste blend increases the interfacial interactions and compatibility between R-PE and R-PA, resulting in decreased polyamide particle size. Finally, the results show that it is possible to produce good quality regranulated products with advantageous properties and structure from immiscible polymer waste for industrial applications.

This work aims to describe the coffee silverskin effect as a lignocellulosic waste filler for high-density polyethylene (HDPE) composites development. The main task was to determine various modification effects resulting from the complex chemical composition of coffee silverskin containing compounds with potential antioxidative properties, including caffeine, polyphenols, tannins, or melanoidins. The processing, thermal, physicochemical, and thermomechanical properties of the HDPE-based composites with different filler content (1–20 wt%) were evaluated. Comprehensively realized thermomechanical analysis revealed the filler’s reinforcing effects on the HDPE matrix while defining problems with obtaining adequate adhesion in the interfacial area. At the same time, studies have shown a very beneficial effect of the silverskin addition on the thermal properties of composites, that even the smallest addition allows for a significant increase in the thermooxidative resistance of HDPE composites assessed using the oxidation induction time from 20 min for HDPE up to 140 min for the composites with 20 wt% of the filler. The obtained research results allow classifying the coffee silverskin waste filler, not only as a filler intended for the production of composites with a high degree of filling but also as an additive that significantly changes the properties of polyethylene in the case of using low concentrations. This can have a very beneficial impact on the development of novel wood polymer (WPC) and natural fiber composites (NFC).

Polylactide is a highly demanded biopolymer, whose industrial application constantly increases. Its disadvantages such as brittleness and slow crystallization rate can be overcome by application of different additives. Because of environmental issues, using natural waste fillers as modifying agents for polylactide is especially interesting. In this study linseed cake, a byproduct of oil extraction from linseed, characterized by oil content of 0.9–39.8 wt.%, was added to polylactide to influence its crystallization behavior. The formation of the crystalline phase was studied by differential scanning calorimetry in isothermal and non-isothermal conditions and analyzed according to methods by Jeziorny, Ozawa, Mo and Avrami. The samples’ microstructures were observed using polarized light microscopy. The crystallization rate and Avrami exponent of samples crystallized in different conditions were evaluated. It was found that addition of 10 wt.% of linseed cake containing at least 17.7 wt.% oil notably changes the crystallization of polylactide, increasing its crystallinity and promoting the growth of crystallites.

Investigations related to polymer/metal composites are often limited to the analysis of the electrical and thermal conductivity of the materials. The presented study aims to analyze the impact of aluminum (Al) filler content (from 1 to 20 wt%) on the rarely investigated properties of composites based on the high-density polyethylene (HDPE) matrix. The crystalline structure, rheological (melt flow index and oscillatory rheometry), thermal (differential scanning calorimetry), as well as static (tensile tests, hardness, rebound resilience) and dynamic (dynamical mechanical analysis) mechanical properties of composites were investigated. The incorporation of 1 and 2 wt% of aluminum filler resulted in small enhancements of mechanical properties, while loadings of 5 and 10 wt% provided materials with a similar performance to neat HDPE. Such results were supported by the lack of disturbances in the rheological behavior of composites. The presented results indicate that a significant content of aluminum filler may be introduced into the HDPE matrix without additional pre-treatment and does not cause the deterioration of composites’ performance, which should be considered beneficial when engineering PE/metal composites.