Plastics,Rubber and Composites: Macromolecular Engineering

Excellence in design is too often unrecognised by manufacturers who believe price is all, and under-appreciated by the general public. Yet iconic products and brands are invariably characterised by innovative and effective design. Various factors contribute to consumers' perception of ‘value' – design, quality, brand, price, for example. How these factors interact and are fed by knowledge and innovation is considered in the light of case studies of the use of polymers in market-leading products.

The digital speckle correlation method is used to study the deformation and fracture behaviour of glass-fibre-reinforced plastics (GFRP) composites with V-notch under tensile loading. The deformation images surrounding the notch tip at varying load levels were captured; both the horizontal and vertical displacement fields are acquired. At the same time, the strain evolution information at the notch tip during the whole damage and fracture process of the notched sample is recorded by a three-element strain gauge. The effects of notch angle and notch depth on deformation and fracture of notched GFRP are analyzed. Some microscopic fracture characteristics such as interfacial debonding, fibre fracture and matrix damage are shown.

The thermal degradation behaviour of rubber from six new Hevea brasiliensis clones (IAC 40, 56, 300, 301, 302 and 303) from São Paulo State, Brazil was studied by thermogravimetry using the Flynn–Wall–Ozawa approach to assess the kinetic parameters (reaction order, activation energy and pre-exponential factor) of the decomposition process. This study indicated that the thermal behaviour is a complex multiple step process, which depends on the type of rubber Hevea clones studied. The rubber from these clones can be classified, following the order of decreasing thermal stability, as IAC 303 > 302 > 56 > 40 > 300 > 301.

The present work deals with the net structures, which are produced by replacing the static die (spinneret) with two concentric dies rotating in opposite directions in a melt extrusion process. These dies consist of defined number of slots with non-circular geometries on their peripheries and the filaments are produced when the slots in disk and annulus are offset from each other. The effect of die rotation on the shape of filament is investigated by analysing the polymer flow inside the complex die slots including square and trapezoidal shapes, using computational fluid dynamics (CFD). The die slot shapes have also been predicted using CFD to achieve the desired filament shape.

The present study is devoted to investigating the gloss difference phenomenon occurring on the surface of water assisted injection moulded parts. Experiments were carried out on an 80-ton injection moulding machine equipped with a laboratory scale water injection system, which included a water pump, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit. The material used was pigmented polypropylene. A plate cavity with a rib across the centre was used. Various processing variables were studied in terms of their influence on the surface gloss difference of moulded parts: melt temperature, mould temperature, melt filling speed, short-shot size, water pressure, water temperature, water hold and water injection delay time. After moulding, a glossmeter was used to measure the surface gloss profiles of the parts. A roughness meter and differential scanning calorimeter were also employed to characterise the surface quality of moulded parts. It was found that the surface gloss difference mainly occurs at the rib/plate transition area of moulded parts and results from the roughness gradient of the surface of the parts. Crystallinity as well as the molecular chain orientation induced by the shear stress in moulded materials may also be factors leading to the gloss difference of moulded products.

Rubber toughened polypropylene (PP) nanocomposites (RTPPNC) containing organophilic layered silicates were prepared by means of melt extrusion at 230°C using a co-rotating twin-screw extruder in order to examine the influence of the organoclay and polyethylene octene (POE) as filler and impact modifier, respectively, on mechanical and fracture properties. The mechanical properties of RTPPNC were studied through tensile, flexural and impact tests. The strength and stiffness of RTPPNC were improved significantly with an increase in the clay content, in the presence of maleic anhydride modified PP (PPgMAH). From the tensile and flexural tests, the optimum loading of organoclay in impact modified PP was found to be 6 wt-%. Conversely, the stiffness and strength of the blends decreased with respect to pure PP as the concentration of POE in the blends was increased. The essential work of fracture (EWF) method was also used to evaluate the fracture toughness of the RTPPNC. EWF measurements indicated that the specific essential work of fracture (w_e) decreased with an increase in the organoclay content. However, additions of POE elastomer are beneficial in enhancing the w_e of the PP blends. w_e appeared to increase with increasing POE content up to 20 wt-%.