In small vessels, for example, yachts, polymer–glass composites are mainly used for their construction. However, the disposal and/or recycling of composite units is very difficult. It is advisable to solve the problem of disposing of post-consumer items as soon as possible. Therefore, alternative, environmentally friendly, but also durable and safe construction materials are being sought. Such materials can be polymer–natural composites, which can be used as a potential material (alternative to polymer–glass composites) for the construction of small vessels. However, its performance properties should be investigated as new construction materials. The possibility of using polymer–hemp composites was assessed in terms of safety, i.e., the fire resistance of these materials. This paper compares selected characteristics that the reaction of composite materials has to fire with glass fiber and hemp fiber reinforcements. During the study, a natural composite reinforced with hemp fabric was investigated. Based on the laboratory test, it was found that this composite showed better susceptibility to energy recycling, with a relatively small deterioration in fire resistance compared to the composite reinforced with glass fiber. This material could therefore be a potential construction material for small vessels if we consider fire resistance in terms of the safety of the vessel’s operation.

This study characterises materials that belong to the group of refuse-derived fuels (RDF). This group of materials regarded as an alternative fuel is derived from industrial, municipal solid and commercial wastes. The aim of this study is to evaluate the quality of waste composition, demonstrate statistically different values and the energy efficiency of the fuel derived from waste. Data on incinerated waste were collected from two different sources. The basic physical and chemical parameters of waste include density and water content. The lower heating value (LHV) of waste, chlorine concentration and ash content of two groups of incinerated waste were also evaluated and compared for a given period of time (one year, with monthly breakdown). Statistical analysis indicated the differences in the combustion of waste groups, visualized by box plots and other diagrams to show the distribution of the results. An analysis of exhaust gas parameters was carried out, both in terms of chemical composition and energy parameters. The RDF combustion process was presented through simulations for the adopted conditions of heat recovery. It was found that for each kilogram of RDF, about 3.85 kWh (13,860 kJ) of heat can be obtained. The combustion process was simulated using Aspen Plus software.

Analysis of the impact of aging processes induced by environmental conditions, particularly aggressive ones, on the properties of polymeric materials and products made from them has been the subject of intensive research for many years. Developing materials characterized by high resistance to the specific external factors in which these materials are used is a key issue in the context of developing a sustainable economy aimed at minimizing waste and extending the service life of polymeric components. The main objective of this research was to assess and quantify the degradation mechanisms of polymeric materials manufactured using additive Fused Deposition Modeling (FDM) technology when exposed to aggressive marine environments. To achieve this, the study analyzed the influence of seawater corrosion conditions on the changes in mechanical and rheological properties of two polymeric materials: recycled polylactide (rPLA) and a wood–polymer composite (WPC) based on PLA reinforced with wood flour (MD). The results revealed that rPLA exhibited an approximately 16% decrease in average molecular weight after 9 months of seawater exposure, accompanied by a 37% reduction in tensile strength and a 24% decrease in elastic modulus. In the case of the WPC, the molecular weight decreased by about 20%, while tensile strength and elastic modulus dropped by 30% and 51%, respectively. The findings provide quantitative evidence of the susceptibility of additively manufactured biodegradable polymers to marine-induced degradation, highlighting the necessity of further optimization for maritime and coastal applications.

The dilution of lubricating oil with diesel oil (DO) is a significant operational problem in piston combustion engines, as it degrades lubrication conditions and may accelerate the wear of interacting components. This study aimed to evaluate the usefulness of selected thermophysical and electrical properties of lubricating oil for determining the degree of its dilution with diesel oil. The tests were conducted on mixtures of SAE 30 or SAE 40 lubricating oil with diesel oil over a concentration range of 0–100% m/m of the latter material. Changes in thermal conductivity, thermal effusivity, and breakdown voltage were examined as a function of the mixture’s fuel content. The thermal conductivity and effusivity of the tested oils were measured using the MTPS (Modified Transient Plane Source) transient method, while the breakdown voltage of the tested oils was measured at mains frequency using an apparatus in which the oil sample was exposed to an increasing electric field by gradually increasing the alternating voltage at a constant frequency until electrical breakdown occurred. An increase in the proportion of diesel oil caused a systematic linear decrease in thermal conductivity and thermal effusivity. A decreasing trend was also observed for breakdown voltage; however, this parameter exhibited significantly greater variation in results. The results indicate that thermal conductivity and thermal effusivity are more useful for assessing the degree of dilution of lubricating oil with DO than breakdown voltage.

The increasing accumulation of plastic waste and the need for circular economy strategies have motivated the development of alternative applications for recycled polymers. This preliminary study investigates the feasibility of using reprocessed high-density polyethylene (HDPE) with a 5 wt.% addition of post-consumer rubber waste in the manufacturing of components for river navigation buoys. Test samples were produced via thermal casting and subjected to density and tensile strength testing in accordance with PN-92/C-89035 and EN ISO 527:1998 standards. Results indicate that the addition of rubber increases the tensile strength from 20 MPa (regranulate) to 23 MPa, while the density rises slightly by 1.84%, remaining comparable to virgin HDPE. These findings demonstrate the potential for reusing polymer and rubber waste in low-load structural applications, supporting material circularity and sustainability goals in river infrastructure.