This review provides an extensive overview of the developments in the field of polymer science, focusing on the solid-state modification (SSM) of thermoplastic materials. The background of the study places thermoplastics within the context of their increased use over the past century, highlighting their versatility in various applications and the associated environmental and health concerns due to certain additives. The methods section delves into the specifics of SSM, a technique that involves the incorporation of monomers or oligomers into the amorphous phase of polymers through multiple exchange reactions, distinguishing it from traditional melt polymer modification methods. The results section outlines the unique aspects of SSM and its increasing recognition for its potential to enhance material performance in areas such as catalysts and composites. It also discusses the application of SSM in modifying different thermoplastic polymers, highlighting various studies demonstrating the method's effectiveness in altering polymer properties. Finally, this work emphasizes SSM's importance in environmental sustainability and its potential in the recycling and upcycling of plastic materials. It acknowledges the challenges and future perspectives in the field, particularly regarding the scalability of SSM techniques for industrial applications and their role in advancing a circular economy in the polymer industry.

Due to its size, wood dust often plays the role of a raw material used as a source of energy. However, it is nevertheless an unavoidable byproduct generated during the milling of wood or wood-based composites. The research presented here is focused on the selected properties of 3-layer plywood, produced with the utilization of dust from the milling of three-layer particleboard as a filler in the bonding mass. Four types of filler were used in the study: commercial rye flour, wood dust naturally occurring in the composition of particles used industrially for particleboard production, wood dust from the first batch of shredded particleboard, and dust from the second round of milled particleboard. In the context of this investigation, the highest modulus of elasticity (MOE) values were observed in reference samples. Conversely, for samples featuring filler material from the initial milling process, there were no substantial differences in filler content. Notably, in samples where the filler was sourced from the secondary milling of particleboard, the modulus of elasticity exhibited an upward trend in conjunction with increasing filler content. A similar trend was observed in samples utilizing the naturally occurring dust. Meanwhile, the modulus of rupture (MOR) decreased with an elevated degree of milling, though it displayed a slight increase as the filler content increased. With regard to shear strength testing, the most favorable outcomes were achieved in samples incorporating filler material from the initial milling of particleboard. The thickness swelling of the plywood reached its peak in variants utilizing filler material from both the initial and secondary milling of particleboards. In contrast, water absorption testing exhibited a more pronounced response in the newly introduced variants, although samples incorporating filler from the initial and secondary milling processes eventually yielded results akin to the reference sample, with the naturally occurring dust displaying higher water absorption values. In terms of density profiles, the highest density values were observed in samples utilizing rye flour as the filler material. A similar density profile was observed in samples with 5 parts of wood flour as filler, although the density of the adhesive was slightly lower in these cases. An increase in the quantity of wooden filler material resulted in a commensurate increase in plywood thickness. The research confirms the possibility of using the aforementioned dust as an alternative to conventional fillers in plywood technology. It also raises the question of how to effectively remove glue residues from wood-based composite dust, which would enhance their absorption properties.

Finishing coatings used in the wood-based composites industry play a key role in the final appearance of the finished product. However, the use of such coatings is not only for aesthetic purposes but also to protect the product against surface damage and moisture or minimize the emission of harmful substances. The latter is an extremely important factor in terms of safety for both the manufacturer and the user, which is why the emissivity test is one of the most important tests in the case of finishing coatings. Such a role can be played by carbon-rich materials, such as those remaining from the extraction of birch bark. In this article, an attempt was made to create coatings in the form of a film by combining a biopolymer with suberinic acid residues (SAR). There were two types of biopolymers used – polylactide (PLA) and polycaprolactone (PCL), in various polymer-SAR ratios. SAR as a residue, is a material that bounds CO2 from the atmosphere and creates a possibility of further use. As part of this study, the obtained coatings were tested in terms of resistance to scratch, relative hardness, cold liquids, total volatile organic compounds (TVOC) and formaldehyde emission, surface absorption etc. Differences in the polymers used and the effect of the SAR additive on selected surface properties were demonstrated. The addition of carbon-rich SAR significantly improves the gas barrier properties of the surface finishing materials based on PLA and PCL. The relative hardness and scratch resistance has also increased with raising SAR content. However, the increasing content of SAR filler act as a limiter in the depth of penetration of deposited surface finishing materials onto the wood surface.

The growing concern about climate change and the recognition of the planet’s limits led society to look for alternatives that promote the balance between the natural and the built environment. The circular economy emerges as an alternative to the linear economic model, inspired by natural metabolisms, by circulating resources in continuous loops, where their intrinsic value is maintained and improved. This research proposes a closed-loop strategy in the built environment by studying innovative constructive solutions that aim to find use, value, and inspiration in what is considered waste. A literature review is conducted on the circular design strategies, re-use and recycle typologies, and waste transformation processes. Then, the development of a methodology for qualitative evaluation and selection of re-used and upcycled construction materials from post-consumer waste and by-products is presented and then applied to thirty-five cases of constructive solutions from plastic, wood, paper, steel, aluminium, and agricultural waste. The research reports that the developed framework is adequate. The analysed alternative materials have good environmental performance and can be used as building materials despite their functional limitations, reflecting the enormous potential of waste as a resource for the construction industry.

Plastics have become an important environmental concern due to their durability and resistance to degradation. Out of all plastic materials, polyesters such as polyethylene terephthalate (PET) are amenable to biological degradation due to the action of microbial polyester hydrolases. The hydrolysis products obtained from PET can thereby be used for the synthesis of novel PET as well as becoming a potential carbon source for microorganisms. In addition, microorganisms and biomass can be used for the synthesis of the constituent monomers of PET from renewable sources. The combination of both biodegradation and biosynthesis would enable a completely circular bio-PET economy beyond the conventional recycling processes. Circular strategies like this could contribute to significantly decrease the environmental impact of our dependence on this polymer. Here we review the efforts made towards turning PET into a viable feedstock for microbial transformations. We highlight current bottlenecks in the degradation of the polymer and the metabolism of the monomers and we showcase fully biological or semisynthetic processes leading to the synthesis of PET from sustainable substrates.

In this work, a simple and environmentally friendly process combining low pressure (vacuum) and mechanical compression is proposed to convert recycled polypropylene (PP) foams (28 kg/m3) into low density foams (90-131 kg/m3) having negative tensile and compressive Poisson's ratios (NPR). The effect of processing conditions (vacuum time, temperature, and mechanical pressure) was studied. Based on the optimized conditions, the tensile Poisson’s ratio of the resulting auxetic foams reached −1.50, while the minimum compressive Poisson's ratios was −0.32 for the same sample. The foam structure was characterized via morphological analysis (SEM) to determine any changes related to the treatment applied. Finally, tensile and compressive properties (Young's modulus, strain energy, energy dissipation and damping capacity) are also presented and discussed. It was observed that the mechanical properties of the resulting auxetic foams were improved compared to the original PP foam (PP-O) for all tensile properties in terms of modulus (19.9 to 59.8 kPa), strength (0.298 to 1.43 kPa) elongation at break (28 to 77%), energy dissipation (14.4 to 56.3 mJ/cm3) and damping capacity (12 to 19%). Nevertheless, improvements were also observed under compression in terms of energy dissipation (1.6 to 3.6 mJ/cm3) and damping capacity (13 to 19%). These auxetic foams can find applications in sport and military protective equipment, as well as any energy mitigation system.