SPE Library
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.
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Recycling
The Influence of Polypropylene Content on the Properties of Post Consumer Recycled High Density Polyethylene
Edward Kosior, Anna Forrest, Syed Masood, Pio Iovenitti, May 1999
Polypropylene (PP) from bottle caps is present in High Density Polyethylene (HDPE) in post consumer recycled resin, and it acts to reduce the overall toughness. This study is concerned with quantifying the influence of PP on the physical properties of recycled HDPE resins and evaluating toughening recycled HDPE/PP blends by the addition of metallocene catalysed linear low density polyethylene (m-LLDPE). The toughness of HDPE was found to decrease significantly with as little as 5 wt% PP, and at 20 wt% the toughness was reduced to levels comparable to that of PP alone. The addition of m-LLDPE was effective in increasing the toughness of the blends to values comparable or greater than those of recycled HDPE alone. The principal mechanism seems to arise from the suppression of crystallinity of HDPE matrix for levels of up to 20% m-LLDPE, and the introduction of amorphous phase content within the samples.
Thermal Aging Effects on Transport Properties of Polymeric Membranes for Fuel Cell Applications
Julie T. Dvorkin, Ronald G. Kander, May 1999
Although solid polymer electrolyte fuel cells have been considered as environmentally attractive power sources, to date little work has been done on the durability of eletrolyte membranes. It is conceivable that time and prolonged exposure of membranes to elevated temperatures will significantly diminish the effectiveness of electrolyte cells. The goal of this study is to investigate and compare thermal aging and morphology effects on transport properties, such as ion diffusion coefficients and permeability parameters of the membranes for hydrogen ion transfer, of commercially available Nafion® and Dias® membranes and experimental phosphorus containing polyimide membranes. The emphasis of this paper is placed on the design and properties of a diffusion cell necessary for hydrogen ion measurements.
Thermoforming Behavior of Olefinic Instrument Panel Skins
Thomas C. Yu, May 1999
Currently thermoplastic olefins (TPO) are being used for injection molded or extruded automotive exterior parts. Due to lack of melt strength of the polypropylene base resin, the thermoformable TPO are still under development for automotive interior skins. The advantages of TPO skins over the current PVC/ABS skins are long term aging, reduced fogging, and improved recycling. Laboratory evaluation for formability usually involves uncommon and tedious tasks. In this study, dynamic mechanical analysis in tension mode was used to predict the optimum temperature range for thermoforming, extent of network enhancement, as well as other mechanical properties.
Thermoplastic Pultrusion Based on Isoplast Engineering Thermoplastic Polyurethanes
Ed L. d’Hooghe, Chris M. Edwards, May 1999
Fiber reinforced composite materials are finding application in an ever increasing range of markets. The bulk of the composite materials is based on a thermoset resins combined with glass roving and/or glass mat as continuous reinforcement. Glass filled thermoplastic resins are limited mainly to discontinuous reinforcement and therefore used primarily in injection moulding applications. Despite potential performance and environmental benefits linked to continuous reinforced thermoplastic composites, they have not been implemented on a large scale. This is because they have been lacking performance in comparison to thermoset composites. Thermoplastic composite materials are a class of structural materials waiting to happen, the results booked ??with the process and material described in this paper show that a significant step forward has been made in developing them.
TPE Overmolding Compounds for the Next Millenium
Dexi Weng, John Andries, Phil Morin, Keith Saunders, John Politis, May 1999
This paper describes the use of TPE compounds for over-molding on to engineering thermoplastic resins. These TPE compounds have a wide range of hardness and are bondable to a wide spectrum of engineering thermoplastic and engineering thermoplastic elastomer substrates. They exhibit very smooth, tack-free, mar resistant surface for the very soft compounds. The bonding between the TPE and the substrate resists environmental changes such as hot air aging and water immersion. The adhesion data and other physical data, adhesion quantification methods, suggested processing conditions and selected applications of these TPE over-molding compounds will also be presented. Theories in TPE over-molding or co-extrusion are discussed.
Trends in Automotive Plastics
Norm Kakarala, May 1999
This briefing on trends in automotive plastics will delineate the differences in plastics application areas between North American and overseas markets. The key themes addressed include: • Although mass savings are widely thought to be a key driver in metal replacement by plastics, increasingly automakers are more interested in the contribution of plastics to styling, occupant safety and comfort, and functionality. • Plastics are increasingly specified for their design freedom. They make possible the consolidation of parts and consolidation of functions, minimizing manufacturing costs while maximizing function and value. • Competition among automotive plastics is relentless and intensifying, resulting in improved forecasted growth for some plastics at the expense of others. • Plastics application trends will be compared between North America and overseas in four sectors: Interiors, Exteriors, Under the Hood, and Chassis and Powertrain. • Greater attention is being given to polymer composites in the U. S. for exterior body panels and some structural applications, with minimal interest in other countries. • Finally, more progress is being made in the recycling of plastic manufacturing scrap than in the recycling of plastic parts/materials from scrap vehicles. This is so because manufacturers have control over process scrap, which improves recyclability and the value of recycled materials. The use of plastics in vehicles is steadily increasing. This trend is expected to continue. On average, current vehicles use about 113 Kg (250 Lbs) of plastics and that amount is estimated to grow to 137 kg (300 Lbs) per vehicle in the next ten years. Historically, vehicle weight savings has been a primary driver in replacing metals with plastics on vehicles. However, today styling, end-use functionality, and better manufacturing economics through parts consolidation are the key factors in choosing plastics to replace other materials in vehicle applications. In addition, fut
Vibrated Gas Assist Molding: Its Benefits in Injection Molding
J.P. Ibar, May 1999
This paper shows how air or nitrogen can be used to impart vibration and/or pressure pulses to a melt. Air is already used to blow preforms and parisons [1] inside of molds, and to core out hollow articles in the process of Gas Assist Injection Molding [2]. The methods of gas assist molding have demonstrated their great usefulness in injection molding not only to hollow parts out but also to induce an excellent surface finish. Melt vibration techniques have also been reviewed [3,4] and show great potential to reduce viscosity during filling and impart optical and mechanical benefits, i.e. stiffness, strength and clarity, without resorting to processing aids such as thinning or nucleating agents. The present paper explores the processing of injection molded plastics under gas vibration. Vibrated gas can be used for several purposes. 1. Gas can be inserted and vibrated in the mold prior to melt injection to modify the filling process mechanism, fuse knit lines, heal sink lines and other defects due to flow imperfections. 2. Compressed Vibrated Gas can act like a pressurized vibrated gas spring, which helps induce orientation benefits in the short shot during filling completion. 3. Vibrated air pressure, localized in specifically designed air-runners distributed around the runners and inside the mold, helps fill and pack the mold, core out hollow parts and balance flow in multi-cavity molds. 4. Vibrated Gas can also be used to tag parts for recognition during recycling or later inspection. The paper reviews hardware and controls requirements to apply this novel technique to injection molding.
Recycling: Giving a Second Life to Plastic Scrap
Prithu Mukhopadhyay, April 1999
Recycling is not as easy as it sounds. Scrap plastics are usually mixed. Before giving them a second chance - they need to be sorted by resin type and/or colour. Otherwise, if 1 wt % PP gets into HDPE stream through bottle caps or by mistake, the toughness of regenerated HDPE bottle decreases. Similarly, as little as 1 ppm PVC in PET can discolour the PET item. Now, sorting can be done manually which is labour intensive and not infallible. When done in an automated system (infrared or X-ray), it becomes expensive. Researchers at SpectraCode of West Lafayette, Ind., have recently invented a point-and-shoot device that can distinguish majority of plastics in 10 microseconds. This translates into 500 tons of plastics/day in a typical recycling operation. Can't we eliminate sorting step and yet produce value added recycled plastics?
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