Plastics,Rubber and Composites: Macromolecular Engineering

This work addresses the usability of novel and sustainable basalt fibre reinforced composites (BFRP) with special emphasis to their structural integrity and fracture toughness , compared to state-of-the-art ECR glass fibre composites (GFRP). Toughness was determined via Double Cantilever Beam (DCB) tests and evaluated both the Area Method (AM) and Corrected Beam Theory (CBT) yielding equivalent results. The organomineral matrix (3P Resin®) was made from (poly)isocyanate, water glass, and an environmentally unfavourable phosphate emulsifier. Phosphate was substituted by renewable oil (denoted as 2P resin) what reduced composites' toughness, and thus an in situ functionalisation by silane-terminated polyurethane (STP-U) was performed. Consequently, the 2P/STP-U resin proved better adhesion to fibres and strongly enhanced toughness. exceeded the conventional 3P composites by 50% (BFRP) and 88% (GFRP), respectively. If both tough and highly sustainable composites are required at the same time, the BFRP with 2P/STP-U is superior to the GFRP solution.

Response: In this investigation, an experimental study has been carried to determine the effects of post-curing temperature (Tc) on the mechanical and viscoelastic properties of SiO₂/epoxy nanocomposites. The nanocomposites were prepared through ultrasonic mixing with a dispersion of 2, 4, 6, and 8 wt.% SiO₂ nanoparticles and post cured at 75, 100, 125, and 150 °‌‌C. The viscoelastic properties were determined using dynamic mechanical analysis tests. The glass transition temperature (Tg) increased with an increase in Tc for pristine epoxy and nanocomposites; however, the increase in the value of Tg for pristine epoxy is less than nanocomposites. The results show that the Tc below the Tg of pristine epoxy improves the tensile properties; however, for Tc above Tg have a detrimental effect on the properties of nanocomposites. With the increase in Tc above Tg, the fracture toughness and fracture energy decrease for nanocomposites.

The effects of Eggshell (ES) on the properties of plasticised PLA and an intumescent flame retardant (IFR) containing plasticised PLA have been investigated. APP and PERwere added into the matrix as an IFR. The characterisation of samples was performed by DSC, TGA, tensile test, LOI, UL-94 and SEM. While APP loading was decreased, the ES was increased in the IFR to obtain a low-price flame retardant. As the ES loading in the composites was increased, the Young's modulus, the thermal resistance and char residue of the composites increased. It was observed that the ES provides a plasticising effect for the PLAPEGIFR sample. The highest LOI value was determined as 34.4 for 10 wt-% ES including the composites. The ES, including the IFR system for plasticised PLA, showed a V0 rating in the UL-94 test. Therefore, it can be concluded that ES can be used as a low-cost filling material in the IFR system for PLA.

To reduce the lead time and costs for developing short run production injection moulding tools the potential of additive manufactured mould inserts is investigated. These hybrid moulds are compared to conventional steel-based moulds, considering mechanical and thermal differences. For part production and insert material, respectively polypropylene and polyamide12 manufactured by Multi Jet Fusion (MJF) are chosen. Moldex3D simulation results show that lower clamping forces and injection pressures are sufficient upon using MJF inserts due to a 20 times lower thermal diffusivity compared to conventional steel, resulting in thinner skin layers and increased solidification times. Practical injection moulding parameters have been optimized by reducing the cooling time with 75 seconds (60%) using forced convectional cooling at 15 °C. Core and cavity inserts show a deviating cooling behaviour linked to the higher amount of insert material and presence of steel. The wear of the mould inserts is minor after producing 360 parts..

Polytetrafluoroethylene (PTFE) composites filled with glass fibre (GF) and graphite were prepared by internal mixer and moulded using compression mould to produce test samples. A high-speed mixer was selected to simulate uneven mixing and excessive mixing conditions by controlling different mixing time. The work studied the mixing process's influence on the mechanical and tribological properties of PTFE composites and investigated the state of glass fibres on the unworn/ worn composite surface with SEM characterisation. The results revealed that the mechanical and tribological properties of composites were associated with the mixing process. For the non-uniform mixing of composite materials, glass-fibre particles fell off the matrix earlier, hindering glass fibre particles in bearing the matrix load. Moreover, excessive mixing increased mixing temperature, the matrix material softened due to overheating, which caused the adhesive wear between the steel ring and PTFE composites. It increased the volume wear rate of composite materials.