The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
Using a factorial design approach, this study examined the effect of the component materials on the viscoelastic properties of PVC/wood-flour composites. Statistical analysis was performed to determine the effects of wood flour content, acrylic modifier content and plasticizer content on the die swell ratio and viscosity of the composites measured on a conical twin screw extrusion capillary rheometer. The experimental results indicated that both the wood flour content and acrylic modifier content have significant effects on the die swell ratio and viscosity of PVC/wood-flour composites.
This study focuses on the ability of U-PVC to be processed a number of times. Three different types of U-PVC were investigated: virgin lead stabilised and virgin calcium/zinc stabilised material and reground, 20 year old, post-consumer windows. Each material was extruded four times and samples taken at each stage for rheological and mechanical analysis.
Using a fracture mechanics approach, a dynamic fatigue methodology was developed to accurately predict creep fracture in both poly(ethylene) and poly(vinyl chloride). The predictive methodology applied to cases in which the crack propagated in either a stepwise or continuous manner. The effects of material variables such as molecular weight and impact modifier were also elucidated.
Developers of thermoplastic materials for pressure pipe applications must design them to resist rapid crack propagation. However, they are usually able only to test them for resistance to impact. The hypothesis that both failure modes are dominated by adiabatic heating leads to good quantitative predictions for each property - and hence to an account of the relationship between them. Here, the model based on this hypothesis is extended to explore the influences on fracture resistance of molecular weight and of thermal property non-linearity.
Residual strains in an epoxy specimen are investigated using embedded Fibre Bragg Grating sensors. A novel OLCR technique allows the direct reconstruction of the optical period and provides the strain distribution due to epoxy consolidation along the fibre. The experimental data show an excellent agreement with finite element simulations.
Polypropylene is increasingly being used as a structural load-bearing polymer in durable applications. Elastomer is usually added for impact toughness improvement but few studies address the selection of elastomer morphologies for resistance to failure due to load conditions over long time. This paper discusses the results of screening some polypropylene-elastomer blends for durability using a recently developed notch sensitivity methodology.
This paper presents a systematic approach to predict damage in a sheet metal forming die fabricated from a composite (aluminum trihydrate-filled polyurethane). The dominant die failure mode is determined based on the mechanics governing the forming process, and the fatigue life is predicted. Both numerical simulations and experiments are performed to verify the method.
This paper probes a hypothesis for initiation of environmental stress cracking (ESCR) based on a thermodynamic criterion for localized swelling induced by stress on the polymer. The system chosen for study is polycarbonate with oleic acid. An experimental technique involving contact angle measurements of a sessile drop as a function of stress is presented. A novel technique for contact angle measurements using refraction is also introduced.
Injection molded bars have been made from blends containing recycled photodegraded polymers, then subjected to further ultraviolet (UV) exposure. Crystallinity measurements have been made at different depths from the exposed surface using X-ray diffraction and differential scanning calorimetry. Complementary information in the form of molecular mass distributions has been obtained using gel permeation chromatography, and the crystallinity results are interpreted in terms of molecular scission and photo-initiated molecular defects.
Laminated and dark coloured uPVC profiles, when exposed to sunlight during normal use, may occasionally suffer deformation. To gain a greater understanding of this phenomenon, a number of test rigs were developed to recreate the temperature increase, through the use of infrared heating elements, to simulate varying intensities of solar radiation.
This paper reviews considerations for linking laboratory and outdoor reference exposure weathering durability data. Laboratory considerations include designing experiments and developing predictive functions using xenon arc devices. Reference exposure considerations include monitoring meteorological and irradiance exposure variables in Florida and Arizona. Exposure data is compared for polycarbonate.
Failures of plastic components are being seen more often in industrial, household and commercial settings. Many of these failures involve the transport of water and cause significant damage when they occur. These failures can be caused by improper material specification, bad design, over loading or incorrect molding conditions. Issues such as chemical resistance, environmental deterioration, geometric sensitivity, temperature dependence and aging are at times overlooked.
Critical items in designs of plastic products are joints. The paper will deal with a number of design aspects about designing reliable plastic products. It will combine the results from our research in the field of stress concentrations, orientation and weld lines around holes, embrittlement of polymers, adhesion and environmental stress corrosion. A number of failures in practice will be presented.
A completely saturated styrene-isobutylene based thermoplastics elastomer has been produced at the industrial scale for the first time. Triblock (SIBS) of Mw range 65,000 to 100,000 have been produced. Due to the saturated main chain of polyisobutylene, these products are superior in heat rersistance, gas barrier properties and damping properties.
Masterbatches of crosslinked solution-polymerized styrene-butadiene random elastomers (XL-SBR) and polypropylene (PP) were prepared and used for enhancing the oil resistance, compression stress relaxation performance, lowering gloss, and compression set of styrene-ethylene/butylene-styrene (SEBS)-based thermoplastic elastomer (TPE) compounds. Enhanced performance was achieved when SBR partly or substantially replaced the SEBS component. Modification of SEBS compounds in the Shore A range of 45-85 with the crosslinked SBR is discussed.
New soft EPDM rubber concentrate can be used to produce thermoplastic vulcanizates (TPVs) with improved flow properties by toll compounding processes for injection molding applications. By adding various amounts of polyolefin plastics such as polypropylene homo polymer or copolymers, TPVs with different durometers and properties can be made easily using compounding equipment such as twin screw extruders or other mixing equipment with sufficient mixing capability.
A new line of thermoplastic vulcanizates (TPVs) has been introduced by DSM Thermoplastic Elastomers for injection molding applications where UV resistance is critical. This new line of products, consisting of several grades with hardness ranging from 50 to 85 shore A in black color, shows superior flow characteristics and balanced properties meeting existing automotive material specifications. In this paper, we will discuss some of the features associated with this new line of products.
A novel, physical foaming agent, ‘water filled polymer,’ has been proven successful in producing low density foamed TPV profiles on standard single screw extruders. Extrusion processing parameters and physical properties (cell size, cell shape, tensile properties, specific gravity, compression load deflection, compression set, surface smoothness and water absorption) of TPV foamed profiles are reviewed. These results are compared to results from other types and forms of foaming agents used to produce foamed TPV profiles.
Wire coating, based on the drag flow is a well-known process in the cable, wire or fibre-optic industry. It has been studied extensively in experimental and computational form over recent years. During the coating a polymer melt flows through an annular converging die and then meets a wire or cable that is usually traveling at high speed. This study is concerned with the numerical simulation of the complex flows that arise in the coating system with a thermoplastic polymer. The simulation study was performed in order to better understand the influence of the rheology parameters, the chosen processing conditions and the coating die geometry dimensions.
This paper presents the results of some coextrusion flow studies for flat film on feed-block and multi-manifold flat dies for well characterised LDPE resins. The aim is to gain a better understanding of interfacial instability phenomena. The LDPE resins included materials of high and low viscosity as well as broad and narrow molecular weight distribution. The experiments involve the coextrusion of either the same materials in both layers or various combinations of materials with different viscosities. The focus of the work was to evaluate the effects of flow rate, viscosity and other material characteristics on the interfacial instabilities. The results from these experiments showed a possibility to locate areas where low or high frequency instabilities were created.
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Brown, H. L. and Jones, D. H. 2016, May.
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ANTEC 2016 - Indianapolis, Indiana, USA May 23-25, 2016. [On-line].
Society of Plastics Engineers
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