Search

In this study, the Time-Temperature-Crystallinity Superposition Principle (TTCSP) was applied to determine the viscoelastic behavior of Thermo-rheological Complex Materials (TCM), specifically Carbon fibre/Poly-Ether-Ketone-Ketone (CF/PEKK) composites. The study investigated the effects of various parameters on the viscoelastic behavior of the composites, such as the degree of crystallinity after different melting temperatures, relaxation, and crystallization times. The TTCSP was utilized on the relaxation data to generate great-grand master curves for the degree of crystallinity for different laminate lay-ups. Hot press forming was employed to manufacture samples under different processing conditions, including various melting and cold crystallization temperatures. Differential Scanning Calorimetry (DSC) was employed to calculate the degree of crystallinity of CF/PEKK composites, while the Dynamic Mechanical Analyzer (DMA) was used to obtain the relaxation data. The generated great-grand master curves proved effective in predicting the relaxation behavior of the composites consolidated using single and double hold cycles at different melting temperatures and crystallization times, respectively. The great-grand master curves presented in this study can serve as valuable tool to calibrate key viscoelastic and/or thermo-viscoelastic material models for aerospace-grade CF/PEKK composites. These models are crucial for simulations aimed at predicting residual stresses and process-induced deformations during the thermoforming process. [ABSTRACT FROM AUTHOR]

Limiting the generation of polymers waste and maximizing their recyclability and recovery have been the main focus of the research and industry in recent years. Recycling of polyamides leads to the loss in mechanical and thermal properties, therefore, in order to reuse recycled nylons, an enhancement in their properties is desired. Enhancing the properties of recycled polyamides by the addition of functionalised graphene nanoparticles (GNPs) was the goal of this study. Recycled PA6/PA6,6 blends and functionalised graphene nanocomposites were prepared using hot-melt extrusion process. Two types of functionalised graphene were used: O2-GNPs and Amine-GNPs. The nanofillers didn't affect the crystallinity of the recycled nylon, while the presence of functionalised graphene increased the thermal conductivity by enabling better heat transfer routes within the polymer. The microstructure of the materials was characterised confirming the successful dispersion but with a slight variation in GNPs/Polymer bonding depending on the functionalisation type. The strong nylon-to-graphene interfacial hydrogen bonding increased the mechanical properties of the recycled nylon nanocomposites. The functionalised nanoparticles slowed down the segmental motion of the polymer chain and decreased the ductility with increasing GNPs contents up to 10 wt%. The overall behaviour of recycled nylon nanocomposites showed dependency on the type of functionalisation and concentration of GNPs with better improvement in the overall properties using 2 wt% Amine-GNPs. These enhanced properties make functionalised graphene/recycled nylon nanocomposites a promising new class of advanced materials. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) has high aspect ratios than many nanosize fillers such as carbon nanotubes and clay, besides its better mechanical properties than many polymers; so they are preferred as a filler material in polymer matrix composites. In this study, the effect of GO on the mechanical properties of linear low-density polyethylene (LLDPE) were experimentally investigated. LLDPE-GO nanocomposites were prepared by melt compounding method, and the extruded nanocomposite was shaped by injection molding machine for the mechanical tests. The mechanical properties investigated included tensile properties, fatigue properties, as well as hardness properties. Differential scanning calorimeter (DSC) was employed to study the thermal characterization of the composites. The results revealed that the addition of GO nanosheets indeed had a positive effect on the tensile, fatigue, and hardness properties. The tensile strength, Young's modulus, and Shore D hardness value were increased by 27.4%, 31.3%, and 9%, respectively, with a GO loading ranging from 0 wt.% to 2 wt.%. The addition of GO had a significant effect on the fatigue properties of the composites such as nearly exponential increment in the cyclic numbers. The samples with 2 wt.% of GO could endure up to 106 cycles during the tests, which is 100 times that of pure LLDPE. The morphological analysis via X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that GO nanosheets were well exfoliated in the LLDPE matrix. However, there is no significant effect on the melting temperature, crystallization temperature and crystallinity of LLDPE based on DSC result. [ABSTRACT FROM AUTHOR]