Production of PLA matrix basalt-wood fiber reinforced biocomposites and investigation of performance features including insulation properties

Because of the unsustainability and/or biodurability of the composites produced with polymers such as petroleum/natural gas derived polyethylene/polypropylene and the increase of environmental awareness and the ecological risks, in recent years researches have increasing interest on biocomposites (biomaterials-containing composites) which have the potential to be bio-based alternatives. However, especially in packaging and insulation sectors and concerns about waste problems after use, it become necessary to reduce the use of synthetic polymeric materials. On the other hand, being lightweight, having excellent mechanical properties, ease of process, and good acoustic properties of biocomposites makes them to be an alternative to glass fiber-reinforced plastics in a wide range of fields from aerospace to automotive industry and home appliances. In addition, bio-based polylactic acid with its good mechanical properties, is an important alternative to petroleum-derived polymers and it is known that biocomposites produced with PLA matrix and various supports have the capacity to be an alternative to many conventional engineering materials. Basalt fiber is a filler obtained from basalt stones. Basalt is one of the volcanic rock masses, which is a mineral found in our country. Basalt fiber is used for thermal insulation, sound insulation, acoustic regulation and can show better mechanical properties than glass fiber. In this study, we produced basalt fiber and beech wood flour reinforced biocomposites with PLA matrix, and investigated performance characteristics including insulation properties. These double-reinforced composites were developed to produce biodegradable materials with better insulation properties. Basalt and wood flour reinforced composites were produced separately in different proportions and compared with double-reinforced composites. Biocomposites were produced by 40 L/D twin screw extruder, tensile and bending tests were performed to determine the mechanical properties. FTIR analysis was made to determine the chemical bonds. TGA analysis was carried out for thermal properties and thermal deflection temperature test (HDT) was performed for thermomechanical properties. In order to determine the physical properties of biocomposites, density, water absorption rate and thickness increase tests were performed. Thermal conductivity coefficient and sound transmission loss measurement were carried out to investigate isolation properties of biocomposites. In order to examine the morphology of biocomposites, scanning electron microscope (SEM) was used. As a result, it was found that both basalt and wood flour supported biocomposites up to 20% had increased bending strengths, but it falls beyond this ratio, and their tensile strengths decreased compared to PLA in all ratios since no crosslinkers was used. It was determined that the tensile and flexural modulus increase with the increasing rate of basalt fiber in the composition. In the thermal conductivity coefficient measurement, it was found that the samples containing wood had a lower conductivity coefficient compared to PLA, whereas the samples containing basalt fiber transmit less of the sound in the sound transmission loss test. However, due to the hygroscopic chemical structure of the samples containing wood flour, water uptake and swelling rates were found to be higher. As a result of the study, environmentally friendly biocomposites with improved insulation properties have been produced with cheaper reinforcement materials.