Plastics,Rubber and Composites: Macromolecular Engineering

The effect of nanoclay on the compressive response of an aerospace grade epoxy polymer was studied. The resin was modified with montmorillonite clay type nanomer I.30, and compressive tests were performed on the optimised specimen geometry. A series of nanocomposite with 1–5 wt-% nanoclay content was fabricated using mechanical stirring and three-roll mill methods. The degree of dispersion of the clay nanoplatelets was examined using TEM. Static uniaxial compression tests were conducted. The compressive stress–strain curves showed that the presence of nanoclay improved the compressive strength and stiffness, promoted higher plastic hardening behaviour after yielding and enhanced the fracture toughness (area under σ–ϵ curve) of the epoxy polymer. The fracture surfaces of the broken specimens were observed using SEM with the aim to identify critical failure mechanisms that contributed to the polymer toughening. Rule of mixtures, Halpin–Tsai and modified Halpin–Tsai models were employed to estimate the compressive modulus of the clay–epoxy nanocomposite system.

The most common description of the mechanical behaviour of viscoelastic materials is presented using complex dynamic properties. These properties depend on many external factors (temperature, excitation frequency, etc.) and determine the evolution of derivative effects in the structure. The purpose of the conducted investigations is the determination of the influence of heating rate on the dynamic mechanical behaviour of a polymer based composite material under different excitation frequencies and temperatures. The glass transition temperatures and the activation energies of the phase transition were calculated, which allow extending the Arrhenius equation by the heating rate factor. The obtained dependencies could be useful for the estimation of the mechanical and thermal degradations of polymeric composites and, among others, for the determination of the self-heating temperature distributions and their evolution during cyclic loading. The presented results could also be applied for the determination of fatigue, crack growth and residual life of composite structures.

The results presented in this paper explore the extent to which indentation in the interfacial region of polymer composites can be used to identify, unambiguously, an interphase of distinct elastic properties. Supporting evidence is presented in the form of atomic force microscopy indentation in the interfacial region of two polymer composites, a glass fibre reinforced vinylester and a glass flake reinforced polypropylene, where a transition region of measurement artefact is revealed as opposed to a physically distinct interphase. The conclusions from these tests are augmented by further work on a glass fibre reinforced phenolic using a new in situ method of identifying measurement artefacts.

A simple method for locating optimal positions for UV lamps used in the curing of curvilinear composite components manufactured with the resin infusion between double flexible tooling process is proposed. A multivariate optimisation model, consisting of continuously differentiable and two-dimensional integral domain parts, was developed. This model has UV lamp positions, dimensions of the manufactured composite component and UV power source as input parameters. The optimum positions of the UV lamps are the output. The two-dimensional integration yields the difference between the required and actual intensities that the composite component receives. A Gauss quadrature numerical integration method was used to numerically evaluate the surface integral, and the Davidon–Fletcher–Powell algorithm was used for predicting optimum positions for the lamps. The mechanical and rheological properties of the UV cured laminates were compared with catalytically cured laminates. Ultraviolet cured components compared well with the catalytic cured composites.

Recycling represents a valid alternative to the disposal of post-consumer plastics in common landfills only when it is possible to obtain new materials with good final properties through practical applications and above all using inexpensive methods. Considering the problem of the great amount of rubber tyre waste produced worldwide, the objectives of this study are to incorporate particles of tyre rubber (TR) waste scrap into a thermoplastic matrix, post-consumer polypropylene (PP) and high impact polystyrene (HIPS) and to evaluate the rheological, physical and mechanical properties. The thermoplastic materials used were ground, washed, dried and ground again into flake form. The particle sizes of the TR used were <500 and 500–1000 μm, separated using a system of sieves of the Tyler mesh series. The PP/TR and HIPS/TR composites, both with weight ratios of 90∶10 and 70∶30, were processed by injection moulding. Results for the rheological behaviour showed that the incorporation of TR particles into the recycled HIPS and PP matrix led to opposite behaviours and that the extent of the effect was dependent on the nature of the polymer and the filler type and particle size. In addition, the presence and concentration of TR led to a reduction in the mechanical properties when compared with the unfilled matrix (post-consumer PP and HIPS), as confirmed by SEM images and the physical properties.

For industrial applications of engineering polymers such as polyurethane, polyamides and polyesters, the addition of suitable reinforcing inorganic fillers is a practical and convenient method to achieve the desirable mechanical and chemical properties. In this study, the mechanical, chemical and morphological properties of cast polyurethane samples containing barium sulphate, calcium carbonate, kaolin and quartz fillers were investigated. In the formulation of these samples, the ranges of inorganic filler were 0–40 phr. The results of mechanical property tests, such as tear resistance, tensile strength, elongation at break, Young's modulus, hardness and abrasion resistance, were evaluated. The chemical resistance of the samples was determined against xylene and methyl ethyl ketone. The chemical resistance of the filled cast polyurethane was determined by the solubility parameters of polymer/solvent. Finally, the experimental results and SEM images showed that samples containing 30 phr calcium carbonate produced the best results.