Due to the massive plastic pollution, development of sustainable and biodegradable polymer materials is crucial to reduce environmental burdens and support climate neutrality. Application of lignocellulosic wastes as fillers for polymer composites was broadly reported, but analysis of biodegradation behavior of resulting biocomposites was rarely examined. Herein, sustainable Mater-Bi-based biocomposites filled with thermomechanically- and chemically-modified brewers' spent grain (BSG) were prepared and subjected to 12-week soil burial test simulating their biodegradation in natural environment. BSG stabilizing effect on polymer matrix affected by the content of melanoidins and antioxidant phytochemicals, along with the impact of diisocyanate applied to strengthen the interfacial adhesion. Biocomposites showed 25-35 wt% mass loss over 12 weeks resulting from swelling of BSG filler and sample microcracking, which increased surface roughness by 247-448 %. The degree of decomposition was partially reduced by BSG modifications pointing to the stabilizing effect of melanoidins and phytochemicals, and enhanced interfacial adhesion. Soil burial-induced structural changes enhanced biocomposites' thermal stability determined by thermogravimetric analysis shifting decomposition onset by 14.4-32.0 °C due to the biodegradation of lower molecular weight starch macromolecules confirmed by differential scanning calorimetry. For unfilled Mater-Bi, it caused an average 32 % reduction in complex viscosity and storage modulus captured by oscillatory rheological measurements. Nonetheless, the inverse effect was noted for biocomposites where modulus increased even by one order of magnitude due to the swelling of BSG particles and amorphous phase decomposition. Presented results indicate that BSG promotes soil degradation of Mater-Bi and its rate can be engineered by biofiller treatment elaboration.

The development of new polymer compositions characterized by a reduced environmental impact while lowering the price for applications in large-scale production requires the search for solutions based on the reduction in the polymer content in composites’ structure, as well as the use of fillers from sustainable sources. The study aimed to comprehensively evaluate introducing low-cost inorganic fillers, such as copper slag (CS), basalt powder (BP), and expanded vermiculite (VM), into the flame-retarded ammonium polyphosphate polyethylene composition (PE/APP). The addition of fillers (5–20 wt%) increased the stiffness and hardness of PE/APP, both at room and at elevated temperatures, which may increase the applicability range of the flame retardant polyethylene. The deterioration of composites’ tensile strength and impact strength induced by the presence of inorganic fillers compared to the unmodified polymer is described in detail. The addition of BP, CS, and VM with the simultaneous participation of APP with a total share of 40 wt% caused only a 3.1, 4.6, and 3 MPa decrease in the tensile strength compared to the reference value of 23 MPa found for PE. In turn, the cone calorimeter measurements allowed for the observation of a synergistic effect between APP and VM, reducing the peak heat rate release (pHRR) by 60% compared to unmodified PE. Incorporating fillers with a similar thermal stability but differing particle size distribution and shape led to additional information on their effectiveness in changing the properties of polyethylene. Critical examinations of changes in the mechanical and thermomechanical properties related to the structure analysis enabled the definition of the potential application perspectives analyzed in terms of burning behavior in a cone calorimetry test. Adding inorganic fillers derived from waste significantly reduces the flammability of composites with a matrix of thermoplastic polymers while increasing their sustainability and lowering their price without considerably reducing their mechanical properties, which allows for assigning developed materials as a replacement for flame-retarded polyethylene in large-scale non-loaded parts.

In this paper, the possibility of obtaining uniaxially rotomolded composite parts was discussed. The used matrix was bio-based low-density polyethylene (bioLDPE) filled with black tea waste (BTW) to prevent the thermooxidation of samples during processing. In rotational molding technology, the material is held at an elevated temperature in a molten state for a relatively long time, which can result in polymer oxidation. The Fourier transform infrared spectroscopy (FTIR) shows that adding 10 wt% of black tea waste has not led to the formation of carbonyl compounds in polyethylene, and adding 5 wt% and above prevents the appearance of the C–O stretching band connected with degradation of LDPE. The rheological analysis proved the stabilizing effect of black tea waste on the polyethylene matrix. The same temperature conditions of rotational molding did not change the chemical composition of black tea but slightly influenced the antioxidant activity of methanolic extracts; the detected changes suggest degradation is a color change, and the total color change parameter (ΔE) is 25. The oxidation level of unstabilized polyethylene measured using the carbonyl index exceeds 1.5 and gradually decreases with the addition of BTW. The BTW filler did not influence the melting properties of bioLDPE; the melting and crystallization temperature remained stable. The addition of BTW deteriorates the composite mechanical performance, including Young modulus and tensile strength, compared to the neat bioLDPE.

The presented research was focused on the development of a new method of sandwich structure manufacturing involving FDM-printing (fused deposition modeling) techniques and compression molding. The presented concept allows for the preparation of thermoplastic-based composites with enhanced mechanical properties. The sample preparation process consists of 3D printing the sandwich’s core structure using the FDM method. For comparison purposes, we used two types of GPET (copolymer of polyethylene terephthalate)-based filaments, pure resin, and carbon fiber (CF)-reinforced filaments. The outer reinforcing layer “skins” of the sandwich structure were prepared from the compression molded prepregs made from the LCP (liquid-crystal polymer)-fiber fabric with the GPET-based matrix. The final product consisting of an FDM-printed core and LCP-based prepreg was prepared using the compression molding method. The prepared samples were subjected to detailed materials analyses, including thermal analyses (thermogravimetry-TGA, differencial scanning calorimetry-DSC, and dynamic thermal-mechanical analysis-DMTA) and mechanical tests (tensile, flexural, and impact). As indicated by the static test results, the modulus and strength of the prepared composites were slightly improved; however, the stiffness of the prepared materials was more related to the presence of the CF-reinforced filament than the presence of the composite prepreg. The main advantage of using the developed method is revealed during impact tests. Due to the presence of long LCP fibers, the prepared sandwich samples are characterized by very high impact resistance. The impact strength increased from 1.7 kJ/m² for pure GPET samples to 50.4 kJ/m² for sandwich composites. For GPET/CF samples, the increase is even greater. The advantages of the developed solution were illustrated during puncture tests in which none of the sandwich samples were pierced.

The development of new sustainable material solutions in the processing of thermoplastic polymers concerns both the application of biopolymers and the use of valorized plant derivatives as fillers and modifiers of petrochemical polymers. Herein, the possibility of using unprocessed raw parts of two commonly used in the food industry leaves, i.e., lemon (LL) and stevia (ST), as active and functional fillers for high-density polyethylene (HDPE) has been verified. The series of composites containing 1, 2, and 5 wt% of ground leaves produced in the melt-mixing process were analyzed for thermal properties (DSC and TGA), and the antioxidant potential of the fillers was evaluated. Verifying the active effect of the ground leaves on the resistance to oxidation in the molten state was carried out by oxygen induction time (OIT by DSC) analysis and oscillatory rheology under steady-state shear conditions combined with spectroscopic (FTIR) carbonyl index (CI) analysis. Studies have shown that the introduction of 5 wt% of both types of leaves allows for a significant increase in the melt oxidation resistance (above 2 times longer OIT concerning HDPE, ~ 35 min) of composites without substantial changes in their crystalline structure and thermal stability. Determined after the long-term rheological measurements in an oxidative atmosphere CI showed 70 and 82% lower values for 5 wt% LL and ST composites compared to unmodified polyethylene. Graphical abstract

The article reports ways and trends in polylactide (PLA) modification methods concerning literature data. The paper consists of two parts and presents the process of polylactide production, and the connection of changes in its properties with the polymer structure obtained thanks to appropriate...