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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INFLUENCE OF MECHANICALLY BLENDED INVESTMENT CASTING WAX FORMULATIONS ON QUALITY OF INJECTION MOULDED PARTS
Wax formulations prepared using paraffin wax (PW) and hydrogenated resin (HR) were studied to identify effects of temperature and composition on phase homogeneity. A phase diagram was constructed showing regions of PW/HR miscibility and tracking changes in PW crystallisation as HR is added. Polarised optical microscopy identified changes in nucleation and crystal growth mechanisms of the PW semi-crystalline phase promoted by HR. A simplified wax injection system was used to investigate conditions for defect formation. Results, to be validated using a ProCAST model, showed defects occurred by injecting blend compositions corresponding to regions of PW/HR phase separation as shown by the phase diagram.
THE FOAMING PROCESS OF PMMA IN SPECIALLY COMPOUNDS UNDER HIGH PRESSURE, VELOCITY AND TEMPERATURE CONDITIONS
In the present study, the friction and wear properties of high temperature resistant polymers, Polyetherimide (PEI) and Polyetheretherketone (PEEK), have been investigated at specific combinations of high pressure, velocity and temperature against smooth steel counterparts. The effects of internal lubricant, polytetrafluoroethylene (PTFE) and PTFE with short fiber reinforcements (carbon fiber) are outlined. The tests were performed on a thrustwasher testing machine under dry sliding conditions. Different analytical techniques were employed to study the correlation between the transfer layer and friction properties. Lubricated and lubricated-reinforced compounds showed excellent wear resistance compared to pristine resins.
RESEARCHES ON MECHANICAL PROPERTIES AND MICRO-STRUTURES OF SBS/AS TOUGHENED HIPS
The mechanical properties and misconstrues of high impact polystyrene (HIPS) toughened by styrenebutadiene-styrene (SBS) were studied to find the Brittle-Ductile Transition Point. At the Brittle-Ductile Transition point, HIPS and SBS alloys were prepared using melt intercalation technique by blending HIPS and SBS while used acrylonitrile-styrene (AS) powder, gaining higher impact and tensile strength. Their microstructures near the Transition Point were characterized by scanning electron microscope (SEM) to investigate the toughening mechanism of HIPS/SBS/AS composites. The toughening mechanism is similar to the mechanism of RIF toughening rather than the cold-drawing theory which applied to ductile matrixes toughed by rigid organic filler (ROF).
EFFECTS OF PROCESSING PARAMETERS ON SHRINKAGE UNIFORMITY OF INJECTION-COMPRESSION MOLDED PART
Both polypropylene (PP) and polystyrene (PS) parts were molded by injection-compression molding. The Taguchi method was utilized to investigate the effects of six processing parameters including mold temperature compression speed compression time compression distance delay time and compression force on part shrinkage uniformity. Analyses of means and variance showed that the compression force is the most important parameter for part shrinkage uniformity of both parts. The compression distance is the second most significant parameter on shrinkage uniformity of PS part but not significant parameter on PP part. The optimal processing parameters for improving the shrinkage uniformity of both parts are found and verified experimentally.
THERMAL ANALYSIS AND RHEOLOGICAL STUDIES ON THERMOPLASTIC URETHANES
Thermoplastics urethanes (TPU) offer broad property range, processing flexibility, and biocompatibility for medical applications. We have undertaken a thermal and rheological study on thermal transitions which influence physical characteristics and oxidative degradation. In addition, possible effects from hydrolytic degradation with long term exposure to alcoholic solvents are sought. Techniques used include Thermal analysis and oxidative induction time (OIT) by differential scanning calorimetry (DSC), and melt rheology. It was found, for selected but not the majority of TPUs, OIT onsets were difficult to obtain. However, melt rheology, with proper sample conditioning, was capable in quantifying the hydrolytic molecular weight degradation process.h
ENHANCING THE PERFORMANCE OF POLYMERIC DYES IN POLYPROPYLENE
Clarified polypropylene (PP) continues to find increasing uses as polymer and additive improvements allow for its incorporation into applications where resins such as polystyrene or acrylics have traditionally been used . Second and third generation clarifiers have improved the clarity, processing properties, and the organoleptic properties (residual odor and taste), opening the way for more extensive food contact applications [2,3]. With the expanded use of clarified polypropylene comes the need appropriate colorants which will give high clarity, low haze, deep coloration, and no migration. Polymeric colorants have shown to possess these properties, further expanding the market potential for clarified polypropylene. This paper will explore the use of various modified wax compounds and their effects on the residual haze of clarified PP molded with GemToneTM Polymeric Colorants.
POLYOLEFIN/CLAY NANOCOMPOSITES: COMPARISON OF DIFFERENT TYPES OF FILLERS AND USING OF MATHEMATIC MODEL
This work reported the comparative study on polypropylene/clay nanocomposites. Commercial filler Dellite and modified micronized calcium were used as a nanocomposite filler for the PP-based composite. All nanocomposites were prepared by using Brabender kneader at different speeds of rotation; however, the compounding time was the same. X-ray diffraction and scanning electron microscopy (SEM) were used for evaluation of morphology. The mechanical properties were evaluated by results of tensile strength and the results were presented in graph. The model was used to predict of tensile strength.
PRODUCTION OF POLYSTYRENE MICROCELLULAR FOAM: EFFECT OF MOLECULAR WEIGHT
Polymer foams prepared with supercritical carbon dioxide as a blowing agent have attracted much interest in recent years. Yet, a thorough understanding of the foaming process, especially nucleation, is absent. In this article, the influence of one characteristic property of polymer, molecular weight, on the nucleation rate and cell growth rate is investigated by an in-situ observation introduced by high speed camera. Moreover, the influence of these two properties on the solubility of carbon dioxide in the polymer is investigated by using a magnetic suspension balance while simultaneously measuring the swelling coefficient during adsorption.
THE ADAPTION OF MICROWAVE HEATING TO THE ROTATIONAL MOULDING PROCESS
This paper details the results from a large European Union rotomoulding research project on the adaptation and development of industrial microwave oven technology to the rotational moulding process. Following computer modelling, an industrial scale microwave oven was specifically designed, manufactured and attached to the drop-arm of a convention rotational moulding machine where extensive moulding trials were carried out. The design and development of the microwave oven and test mould, together with the savings in terms of energy efficiency and mould heating rate that were achieved are discussed.
THE ADAPTION OF MICROWAVE HEATING TO THE ROTATIONAL MOULDING PROCESS
Durability and performance of membranes under alternating relative humidity conditions are very important for fuel cells in automobile applications. This work proposed a wet/dry (W/D) cycle test and studied the effect of W/D cycles on the dimension and properties of polymer membranes. It was found that solution cast films shrunk stepwise in both machine and transverse directions when they underwent wet/dry cycles. The water swelling and water take-up of membranes are also a function of W/D cycles. Based on these results, one might use W/D cycling as a post-processing scheme to reduce the shrinking stress and water uptake of the membranes and thus extend the life of membranes.
MECHANICAL PROPERTIES OF POLYCAPROLACTONE/THERMOPLASTIC STARCH BLOWN FILMS
The processing and mechanical properties of blown films prepared from thermoplastic corn starch (TPS) and polycaprolactone (PCL) has been studied. The aim was to determinate the influence of processing parameters on mechanical properties in order to establish the relationship between mechanical properties of the films, PCL concentration and processing. In addition, the influence of moisture content on mechanical properties during the first days of storage was also studied. The results showed that the effect of moisture absorbed during storage over the mechanical properties was not significant for blends that contained up to 60% PCL.
POST-CONSUMER HDPE/AGAVE FIBRE COMPOSITES COATED WITH CHITOSAN USED FOR REMOVAL OF HEAVY METALS
Composites of post-consumer high density polyethylene (HDPE) with agave fibre were prepared by extrusion and coated with chitosan. A chemical pretreatment was applied to the composite to enhance chitosan gel compatibility. The adsorption capacity of the composite coated with chitosan was evaluated for Cd(II) and Cu(II). The coated composites were characterized by SEM, ATR-IR and XPS. Atomic Absorption Spectroscopy (AA) was used to measure metal uptake in batch studies. Adsorption Isotherms were obtained at three different pH values. The results of this study demonstrate the composite's ability to immobilize chitosan on its surface and its capacity to adsorb metal ions.
A STUDY OF DEMOULDING FORCE PREDICTION APPLIED TO PERIODIC MOULD SURFACE PROFILES
Demoulding components without damage to either the components or tool is critical to successful replication processes. Accurate demoulding force prediction prior to tool fabrication helps designers optimize replication tools to minimize the demoulding force and resultant stress on replicated parts. Various models have been proposed to predict demoulding forces. One such model, the stair-step model, was developed by Colton et al for stereolithographic moulding tools. This paper investigates applying the model to other periodic surfaces with validation using published experimental data. In addition validity of the model for application to micro mould surfaces produced by micro milling is discussed.
MECHANICAL PROPERTIES OF INJECTED MOLDED PCL/TPS NANOCOMPOSITE BLENDS
Injected molded nanocomposite blends based on PCL/TPS and Cloisite 15A (C15A) were prepared and its mechanical properties were studied. The injected samples were exposed to the environment in order to analyze the influence of exposure time and moisture uptake over mechanical properties. The results showed that samples tested right after molding exhibit low mechanical resistance to impact and high Young modulus, while increasing the environmental exposure time reduced the Young modulus and substantially increased the medium failure energy. On the other hand, using C15A increases the medium failure energy, and an important interaction between TPS, moisture and clay was observed.
ACCELERATED CYCLIC FRACTURE MECHANICS TESTS TO ANALYSE MOLECULAR AND MORPHOLOGICAL EFFECTS ON SLOW CRACK GROWTH IN MODERN PE PIPE GRADES
Three different polyethylene pipe grades and three different lots of one PE pipe material were investigated with fracture mechanics procedures under cyclic and impact loads. The cyclic tests with Cracked Round Bars allowed a ranking of the different PE pipe grades and lots concerning crack resistance as a function of failure time as well as of crack initiation time. The ranking corresponded to the expectations based on the molecular and morphological properties of the materials. Concerning lot-to-lot variations, in particular, a correlation to crystallization kinetics, melt flow rate and density measurements could be established.
NANOCOMPOSITES OF THERMOTROPIC LIQUID CRYSTAL POLYMER WITH CARBOXYLATED MULTI-WALL CARBON NANOTUBE
Incorporation of multi wall carbon nanotube (CNT) into the thermotropic liquid crystal polymer matrix (TLCP) obtained high performance polymer nanocomposites. For fabrication of high performance polymer nanocomposites, major challenge is to improve the dispersion of CNT in the TLCP matrix and the interfacial adhesion between CNT and the TLCP matrix. In this study, Multi-wall carbon nanotube (MWCNT) reinforced TLCP nanocomposites were prepared by a melt compounding using twin-screw extruder. The CNT was functionalized with chemical surface modification to introduce carboxyl groups onto the surfaces of CNT for uniform dispersion and induce excellent interfacial adhesion. The rheological, mechanical, morphological, and thermal properties of TLCP/CNT nanocomposites were investigated.
INVESTIGATION INTO A HIGH OUTPUT POLYPROPYLENE SCREW AND ITS MIXING MECHANISM
It is known industry wide that polypropylene (PP) resins plasticate at reduced rates compared to other olefins. While many causes have been suggested for this problem a solution was not. A simple spiral fluted extensional mixer (SFEM) was first introduced for the single screw extruder (SSE) for its superior compounding. [1 2 3 4 5]. A variation the Elongator II hereafter SFEM II was tested against a control screw for output. A 100% increase in output was found over a conventional screw— more than making up for PP’s historically low rate. Because the SFEM series is noted for its ability to compound like a twin we investigated mixing on the SFEM II. The investigation compares the flow to a simple computer model. A color concentrate of just 0.5% was used with frozen pullouts or carcasses showing the mixing during operation. The extrudate is examined and even when magnified to 100X does not show striation lines.
INVESTIGATION INTO A HIGH OUTPUT POLYPROPYLENE SCREW AND ITS MIXING MECHANISM
It is known, industry wide, that polypropylene (PP) resins plasticate at reduced rates compared to other olefins. While many causes have been suggested for this problem, a solution was not. A simple, spiral fluted extensional mixer (SFEM) was first introduced for the single screw extruder (SSE) for its superior compounding. A variation, the Elongator II, hereafter SFEM II, was tested against a control screw for output. A 100% increase in output was found over a conventional screwƒ?? more than making up for PPƒ??s historically low rate.Because the SFEM series is noted for its ability to compound like a twin, we investigated mixing on the SFEM II. The investigation compares the flow to a simple computer model. A color concentrate of just 0.5% was used with frozen pullouts or carcasses showing the mixing during operation. The extrudate is examined and, even when magnified to 100X, does not show striation lines.
A DISCUSSION ON PREVENTION OF PLASTIC PRODUCT FAILURES
This paper attempts to show through case studies how plastic product failures could be prevented. Failures of plastic products manufactured from HDPE, PBT, and glass-filled nylon material are discussed. In each case study, the root-cause of the plastic product failure has been identified through a failure analysis investigation. The corrective action during the material selection process, the part design process, or the manufacturing process that would have prevented the failure has been suggested. The discussion of these case studies will enhance the understanding of the common errors occurring during the plastic product cycle. This paper should foster further discussion and reporting with focus on prevention of plastic product failures.
CHARACTERIZATION OF THE MICROSTRUCTURE OF POLY (HYDROXY BUTANOIC ACID) COPOLYMERS DURING THEIR POST-FABRICATION ANNEALING AT ROOM TEMPERATURE
The mechanical properties of bio-based, biodegradable poly (hydroxy butanoic acid) or PHB copolymers are known to change considerably over a period of time after their parts are fabricated. This study will focus on the changes in semi-crystalline morphology during this aging process. The semi-crystalline morphology is characterized using the three-phase model (crystalline, mobile amorphous and rigid amorphous phases) and through a variety of experimental probes including thermal analysis, refractometry, x-ray diffraction and solid-state NMR.
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