An advanced SiO2–lignin hybrid material was obtained and tested as a novel poly(vinyl chloride) (PVC) filler. The processing of compounds of poly(vinyl chloride) in the form of a dry blend with silica–lignin hybrid material and, separately, with the two components from which that material was prepared, was performed in a Brabender mixing chamber. An analysis was made of processing (mass melt flow rate, MFR), thermal (thermogravimetric analysis, Congo red and Vicat softening temperature test) and tensile properties of the final PVC composites with fillers in a range of concentrations between 2.5 wt % and 10 wt %. Additionally, the effects of filler content on the fusion characteristics of PVC composites were investigated. The homogeneity of dispersion of the silica–lignin hybrid material in the PVC matrix was determined by optical microscopy and SEM. Finally, it should be noted that it is possible to obtain a PVC composite containing up to 10 wt % of silica–lignin filler using a melt processing method. The introduction of hybrid filler into the PVC matrix results in a homogeneous structure of the composites and positive processing and functional properties, especially thermal stability and Vicat softening temperature.

Poly(lactic acid) (PLA) was plasticized with maleinized linseed oil (MLO) and further reinforced with sheep wool fibers recovered from the dairy industry. The wool fibers were firstly functionalized with 1 and 2.5 phr of tris(2-methoxyethoxy)(vinyl) (TVS) silane coupling agent and were further used in 1, 5, and 10 phr to reinforce the PLA/MLO matrix. Then, the composite materials were processed by extrusion, followed by injection-molding processes. The mechanical, thermal, microstructural, and surface properties were assessed. While the addition of untreated wool fibers to the plasticized PLA/MLO matrix caused a general decrease in the mechanical properties, the TVS treatment was able to slightly compensate for such mechanical losses. Additionally, a shift in cold crystallization and a decrease in the degree of crystallization were observed due to the fiber silane modification. The microstructural analysis confirmed enhanced interaction between silane-modified fibers and the polymeric matrix. The inclusion of the fiber into the PLA/MLO matrix made the obtained material more hydrophobic, while the yellowish color of the material increased with the fiber content.

A method to modify polymers is that of introducing fibers in a matrix to produce a fiber-reinforced polymer (FRP). Consequently, the aim of this work was to study the compatibility effect of four coupling agents on wool FRP properties, using poly(lactic acid) plasticized with maleinized linseed oil as polymer matrix. The content of wool assessed was 1 phr. The compatibilizers were (3-(2-aminoethylamino)propyl)-trimethoxysilane, trimethoxy (2-(7-oxabicyclo (4.1.0)hept-3-yl) ethyl) silane, tris(2-methoxyethoxy)(vinyl) silane and titanium (IV) (triethanolaminate)isopropoxide. Initially, wool was modified with coupling agents in an acetone/water (50/50) solution. Mechanical properties were evaluated by tensile and flexural properties, hardness by Shore D measurement and impact resistance by Charpy’s energy. Differential scanning calorimetry, dynamic thermo-mechanical analysis, and thermogravimetric analysis were conducted to evaluate the interaction among components and the effect of the coupling agents on the thermal properties of the original material. Color, wettability and scanning electron microscopy were used to describe physical and microstructural properties. Modification of fibers allows achieving improved mechanical properties and changes the thermal properties of the FRPs slightly. Coupling agent treatment helps to formulate PLA–MLO and sheep wool materials and to improve their performance, thereby creating a broader spectrum of applications for PLA maintaining the bio-based character of the material.

Biodegradable materials based on poly (lactic acid) (PLA) and a phenolic free modified rosin resin were obtained and studied to control the biodegradability under composting conditions of the materials. The resin was blended in concentrations of 1, 3, 5, 10, and 15 parts per hundred (phr) of base polymer using industrial plastic processing techniques. Additionally, to study the effect of the resin on the compatibility of the PLA, the physical performance, water absorption, mechanical behavior, thermal stability, and microstructure of the materials were assessed. The resin incorporation decreased the resistance to thermal degradation of the resultant material, and the composting disintegration rate was slowed down with the increasing content of the resin. The water diffusion was delayed, and the diffusion and corrected diffusion coefficients decreased with the rising content of UP. The mechanical properties tend to decrease while a saturation effect was observed for contents higher than 3 phr of resin. The optimal amount of resin that can be added to achieve good interaction with PLA matrix, complete miscibility, and good material cohesion is 3 phr.

In this work, the presence of biodegradable polymers in recycled plastic materials was characterized using readily available techniques. Recycled polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET) were studied. The contamination of these plastics with polylactic acid (PLA), polyhydroxybutyrate (PHB) and thermoplastic starch (TPS) was simulated using 10 wt.% of the contaminant. Fourier transform infrared spectrometry (FTIR) and differential scanning calorimetry (DSC) were used as characterization techniques. In addition, the effect of aging on recycled products from PET blends contaminated with TPS and PHB was studied. The results show changes in the intensity of the FTIR spectra bands of the PS and PP blends contaminated with biodegradable polymers. By DSC, changes in the cold crystallization peak of recycled PET are observed when mixed with TPS and PHB. When the contaminant is PLA, the changes are masked due to the thermal characteristics of both materials. In PS, changes in the calorimetric curves are identified by the presence of PLA and PHB. Contamination with PLA, PHB and TPS hinders the processing of recycled PET after one year of storage due to the aging of the material.

Thermoplastic starch (TPS) and polyvinyl alcohol (PVA) blends were prepared over the full compositional range (0–100 wt% PVA) by solvent-free twin-screw extrusion and injection molding. This enabled a systematic evaluation of structure–performance–disintegration relationships under industrially relevant conditions. The blends exhibited clear composition-dependent trends in thermal and mechanical behavior. Increasing PVA content from 0 to 100 wt% raised the onset degradation temperature (T5%) from 160.5 °C to 290.5 °C and increased crystallinity from near zero to 12.24%. Mechanically, the response evolved from a rigid TPS-rich state to a ductile PVA-rich one. FTIR and SEM analyses indicated partial compatibility, with limited molecular-level interactions leading to morphologically homogeneous but only partially miscible blends. Under simulated composting conditions, all formulations showed substantial physical disintegration. PVA-rich blends (≥60 wt%) disintegrated rapidly (>80% mass loss within two days), primarily by dissolution rather than microbial degradation. Overall, this work provides a comprehensive, scalable assessment of solvent-free TPS/PVA blends, clarifies their limited compatibility under melt processing, and demonstrates how composition can be used to tailor structure, performance, and disintegration behavior across the full compositional range.