Rotational molding processing performance and structure of high-density polyethylene (HDPE) composites with basalt powder (BP) and talc (T): The influence of mold wall thickness and filler type

The production of thin-walled products from thermoplastics by rotational molding (RM) has increasingly turned into polymer composites. Rotational molding (RM) is a technology that enables the manufacturing of ready-to-use products using a single-step processing method. The development of measurement technology leads to a deeper understanding of the process control-to-structure relationship. This study aims to correlate the process analysis based on the internal mold air temperature (IAT) with the structural, thermal, and mechanical properties of high-density polyethylene (HDPE) composites reinforced with two inorganic particle-shaped fillers, basalt powder (BP) and talc (T). Differential scanning calorimetry (DSC) confirmed the nucleating effect of the fillers, especially T, on the HDPE matrix, which correlates with the changes in the course of the IAT curves. Despite introducing fillers with small particle size (<100 μm), the obtained porosity of the products determined by 3D computed tomography (3D CT) was maximally 0.33%. The low porosity of RM products allowed the suppression of excessive, unfavorable effects of limiting mechanical performance (minimum tensile strength of 19.4 MPa). The composites showed up to 1450 MPa (BP) and 1300 (T) MPa young modulus compared to 1150 MPa (HDPE), respectively. The obtained research results confirm the validity of introducing particle-shaped inorganic fillers not only as modifiers of physical and mechanical properties, but also of processing properties. The study supplements the current state of knowledge with information on the manufacturing of composites using specific technology RM, which utilizes low-cost inorganic fillers with high potential for industrial implementation.