Plastics,Rubber and Composites: Macromolecular Engineering

In this study, the effects of resin type and liquid butadiene rubber (LBR) on the rheological, network structure, mechanical, dynamic mechanical, and damping properties of poly(epichlorohydrin) (CO) and poly (epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) (GECO) elastomers were investigated. To study the impact of resin type, C8/C9 and C9/C10 aromatic hydrocarbon resins, phenolic resin, and LBR were used as liquid rubber. Rheological studies have shown that adding resin and LBR in the preparation of both CO and GECO-based elastomers reduces the degree of curing and, as a result, the cross-link density due to the plasticising effect of these agents. While the change in cross-link density reduced the tensile strength, it increased the elongation value at break. A sharp decline in the mechanical properties of systems using LBR has been observed. When using resin, the most significant change observed was in the damping properties of elastomers. The use of resin enhanced the energy dissipation properties. In both CO- and GECO-based elastomers, phenolic resin was identified as the most effective for extending the effective damping range. CO-DP5245 demonstrates effective damping (tanδ > 0.3) at particularly high temperatures (ranging from −2.0 °C to +70 °C), while GECO-T3108 shows effective damping at low temperatures (ranging from −36.1 °C to +10.5 °C). Among all the prepared elastomers, the highest tan delta (tanδ) value was obtained in the CO-PhenRes elastomer, which was formulated using CO-DP5245 and phenolic resin. This makes it suitable for high-temperature applications. Cyclic compression and dynamic mechanical analyses show that the GECO-based elastomer, prepared using C8/C9 hydrocarbon resin, is the most effective elastomer for low-temperature damping applications. These studies demonstrate that all physico-mechanical and dynamic mechanical properties can be modified in a controlled manner by altering the network structure using resin and LBR in both CO and GECO-based elastomers.

This research evaluates the tribological performance of polytetrafluoroethylene (PTFE) filled with graphene nanoplatelets (GNPs) against steel under aqueous conditions to correlate the impact of the GNP percentage in PTFE, the test environment and load. Trials were carried out on a pin-on-disc reciprocating tribometer following Taguchi's L32 design. Analysis of variance revealed that GNP percentage and environment are the dominant factors affecting the average coefficient of friction (COF) and specific wear rate (SWR), respectively. The technique for order of preference by similarity to ideal solution (TOPSIS) was utilised to optimise the response variables (COF and SWR). Field emission scanning electron microscope and energy-dispersive X-ray spectroscopy were used to assess the worn surfaces. The outcomes established that the seawater environment remarkably decreased COF and SWR, and 5 wt. % GNP/PTFE performs best. TOPSIS demonstrates that a 5 N load, GNP percentage 5%, and seawater yield optimum performance.

High-impact polystyrene (HIPS) is widely used in household appliances, electronic equipment casings, packaging materials, and automotive parts due to its excellent dimensional stability, fluidity, electrical insulation, and rigidity. However, its high flammability and significant smoke emission during combustion limit its application in fire-sensitive environments. In this study, a synergistic intumescent flame retardant system composed of hollow cubic zinc hydroxystannate (H-ZHS), piperazine pyrophosphate (PAPP), and melamine polyphosphate (MPP) was developed to improve the fire safety of HIPS composites. Thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 vertical combustion, and cone calorimetry (CCT) were employed to evaluate the thermal stability, flame retardancy, and smoke suppression properties. The optimised composite (30 wt% total flame retardant loading with a PAPP/MPP mass ratio of 7:3 and 2 wt% H-ZHS) achieved a UL94-V0 rating (1.6 mm thickness) and an LOI of 34.3%. Compared to pure HIPS, the peak heat release rate (pHRR), total heat release (THR), and total smoke production (TSP) decreased by 74.1 ± 3.2%, 20.6 ± 1.8%, and 65.3%, respectively. The synergistic mechanism involved condensed-phase char formation catalysed by H-ZHS and gas-phase flame inhibition by non-flammable gases (e.g. NH₃) from PAPP/MPP decomposition. This work provides a practical strategy for developing halogen-free flame-retardant HIPS composites with balanced fire safety and mechanical properties.

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In this work, hardness, wear resistance, modelling of dynamic mechanical properties and activation energy of thermal degradation of poly aryl ether ketone reinforced with tungsten carbide combined with carboxyl-functionalised multi-walled carbon nanotubes are reported. Melt mixing technique followed by injection molding was carried out for the production of poly aryl ether ketone/tungsten carbide/carboxyl-functionalised multi-walled carbon nanotube individual and hybrid nanocomposites. The hardness of the nanocomposites was measured using shore D hardness equipment and it was found out that poly aryl ether ketone reinforced with 0.75 wt.% tungsten carbide and 0.75 wt.% carboxyl-functionalised multi-walled carbon nanotubes (1.5WF) showcased the highest hardness value and an increment of 7.05% compared to base matrix. The hybrid nanocomposite 1.5WF was observed to be minimum specific wear rate at 10 N and 20 N. The storage modulus and damping behaviour of the individual and hybrid nanocomposites were modelled using classical equations. The integrated procedural decomposition temperature and activation energy were calculated, showing that 1.5WF nanocomposites exhibited a 45.63% higher activation energy compared to the base poly aryl ether ketone matrix using the Coats–Redfern method. The results revealed that the carboxyl-functionalised multi-walled carbon nanotube and tungsten carbide nanoparticles significantly influenced the Shore D hardness and sliding wear behaviour of the individual and hybrid nanocomposites.