Dario Pervan

The reprocessing of wood–plastic composites (WPCs) significantly affects their structural integrity and thermal behavior. Despite this, the effect of reprocessing on PVC-based WPCs has not been extensively investigated, and the mechanism is not well understood. This study evaluated the effect of reprocessing on the properties of a PVC-based WPC. Small pieces of extruded WPC boards (2–4 mesh) were first milled to a granulation of 50 mesh, and then the material was reprocessed by compression molding, with part of the samples reinforced with glass- and carbon-fiber fabric. The physical and mechanical properties of the reprocessed material were analyzed, and the chemical and thermal characteristics of the reprocessed WPC were compared with the virgin WPC. The results of the mechanical and physical property tests showed that the reprocessed WPC had satisfactory properties compared with the virgin WPC. Samples reinforced with carbon-fiber fabric showed a statistically significant increase in tensile and flexural strength in comparison with unreinforced reprocessed WPC samples. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) showed that partial dehydrochlorination, thermal degradation and a decrease in thermal stability occurred. Overall, the results of this study show that although chemical degradation and a decrease in thermal stability were present in the reprocessed WPC, it retained satisfactory mechanical and physical properties that could be improved by reinforcing it with carbon-fiber fabric.

This study examines the effects of temperature, relative humidity, moisture content, and density on the dielectric constant (ε′) and dielectric loss tangent (tan δ) of oak wood lamellae within a frequency range of 0.079 MHz to 25.1 MHz. The hypothesis tested was that increased temperature and moisture content enhance both dielectric polarization and loss, while density acts as a dominant structural determinant of dielectric behaviour. Oak lamellas were conditioned above saturated salt solutions at 20 °C and measured using an Agilent 4285A LCR meter according to ASTM D150-22. Multiple linear regression was used to demonstrate the statistically significant influence of temperature, relative humidity, moisture content, and density on the tested electrical properties of the lamellas. The results showed that the dielectric properties increase with higher sample density and higher air humidity. Temperature also had an influence, but it was significantly smaller, though still statistically significant (p < 0.05). Changes in dielectric properties were most pronounced at frequencies below 1 MHz, suggesting that dipolar and interfacial polarization are greater at lower frequencies. The findings in this paper provide a basis for optimizing the high frequency/dielectric heating process for heating before bending of oak and other similar hardwoods.

Using the RadSawSim simulator for radial sawing, a simulation of the radial sawing technique was used to saw Pedunculata oak (Quercus robur L.) logs. Simulation was implemented with a view to producing as many radially sawn boards as possible and took into account the influences of increasing volume yield, lumber value yield, and log-value yield. The methods that were analyzed were live sawing and radial sawing of third sections, fourth sections, fifth sections, and sixth sections of the log. Live sawing achieved the best results of volume yield during simulation, which was followed by radial sawing into the third, fourth, fifth, and sixth sections. The difference in volume yield with live sawing compared to the radial-sawing method is very large for logs up to a diameter of 45 cm. It becomes smaller when the log diameter is greater than 45 cm. A comparison of the radial method shows that the share of radially sawn boards and lumber value yield increased when the number of log sections during sawing simulation increased. If log-value yield is assumed to be the main criterion, and given the conditions used in this simulation, there is no justified reason to saw logs using the radial technique when the diameter is less than 45 cm. The live sawing technique is more efficient for these diameters of logs, and, therefore, the radial sawing technique is more efficient for logs with a diameter greater than 45 cm.