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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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.
AN IN SITU STRUCTURING RHEOMETER BASED ON CHAOTIC ADVECTION
An in situ structuring rheometer (ISSR) has been developed that allows simultaneous controlled formation of structure in polymer blends and composites and measurements of rheological properties. Multi-layer, interpenetrating, and platelet polymer blend morphologies are examples of structure types producible. Networks among solid particles and dispersions can also be formed.The ISSR is modular for installation into existing rheometer platforms. In situ structuring in the melt occurs by chaotic advection which recursively stretches and folds melt domains. Characteristic structure sizes in the melt can reduce to nano-scales so the ISSR also has application to nanocomposites.
PHYSICAL AND MECHANICAL PROPERTIES OF NEW HIGH-FLOW POLYCARBONATE COPOLYMERS
A new range of polycarbonate copolymers derived from bisphenol-A (BPA) and specific bio-sourced monomer derived from castor bean oil is presented. These copolymers, designated LEXAN* HFD resins, offer an improved melt flow and ductility balance compared to standard polycarbonate yet offer similar high optical clarity and light transmission properties. Lower temperature processing capability, longer injection molding flow lengths, improved low temperature ductility, and superior mold release performance are all advantages for these new copolymers versus a standard polycarbonate material. Glass fiber-filled formulations of the HFD copolymer show comparable mechanical and impact properties compared to glass-filled polycarbonate materials but show nearly 50% higher surface gloss in injection molded plaques.
ADHESION OF ELASTOMERIC COPOLYMERS TO POLYOLEFINS
The effectiveness of elastomeric copolymers as adhesives for polypropylene and polyethylene was studied using coextruded microlayered tapes. The olefinic and styrenic block copolymers were the most effective adhesives of all the elastomeric copolymers used in this study and they delaminated adhesively from the polypropylene-tie-layer interface during T-peel experiments. The effect of tie-layer thickness peel temperature and peel rate on the adhesive properties were probed. Relationships between tie-layer deformation damage zone structure interfacial morphology and delamination toughness were established and a structural mechanism is provided.
APPLICATIONS OF HYPHENATED DSC-RAMAN SPECTROSCOPY TO POLYMERS
DSC is widely used to investigate phase changes of materials as their temperature is changed, or isothermally.However the information obtained is essentially quantitative as this is a univariate technique that simply measures heat flows. Vibrational spectroscopy can provide complementary information, giving insight at molecular level.into the changes accompanying thermal events or reactions. In addition the multivariate nature of Raman spectra means that it is possible to monitor simultaneous events with different spectral signatures that cannot be distinguished by DSC. A hyphenated system is described, evaluated and applied to some polymer systems
THE EFFECT OF MOLD TEMPERATURE ON THE SURFACE PHASE MORPHOLOGY OF INJECTION MOLDED THERMOPLASTIC ELASTOMERS
The surface phase morphology of thermoplastic elastomers can be affected by injection molding parameters. In this paper the influence of mold temperature on the phase morphology of SEBS triblock copolymer was studied through tapping mode atomic force microscope (AFM) and 2D-Fast Fourier Transformation (2D-FFT) analysis. It was found that more orientation was present in the materials prepared using high mold temperatures.The orientation direction of the morphologies could be predicted by computer simulation.2D-FFT analysis can be used to study the domain orientation and structure.
REINFORCING POLYPROPYLENE WITH LOW MOLECULAR WEIGHT COMPOUNDS
This study presents a new approach which involves melt-blending a low molecular weight additive and a polymer at a process temperature where the additive reduces the process viscosity. Upon cooling, the additive forms crystalline reinforcing domains. Emphasis is given to reinforce isotactic-polypropylene (iPP) with calcium stearate (CaSt). The changes in yield strength and modulus suggest a synergy between the CaSt and iPP. Addition of 10% CaSt increases the fracture energy by 5 fold without a loss in modulus and with an apparent reduction in shear viscosity. CaSt is the only additive commencing simultaneous improvements.
EFFECT OF MOLECULAR STRUCTURE ON HEAT SEAL PROPERTIES FOR HIGH DENSITY POLYETHYLENE FILM
Effect of molecular structure on heat seal properties for high density polyethylene (HDPE) film was investigated in this study. Polyolefin is usually adopted as a sealant material for general packaging system. Melting temperature of the HDPE film used in this study was 126 oC. The heat seal temperature was controlled and varied at around melting temperature of HDPE precisely. The mechanical property of the sealed films was measured by a T-shape peeling test. Development molecular structure at film interface for sealing was evaluated in a wide angle x-ray diffraction pattern and changing of molecular orientation relaxation corresponding with the mechanical peeling property. Thermal property was also analyzed by a differential scanning calorimetry (DSC). The weight fraction of melting region in heat seal process was estimated from the DSC thermograms. We discussed that the amount of melting region is related to the major factor to decide peeling properties of heat sealed HDPE film.
EFFECT OF MOLECULAR STRUCTURE ON HEAT SEAL PROPERTIES FOR HIGH DENSITY POLYETHYLENE FILM
Effect of molecular structure on heat seal properties for high density polyethylene (HDPE) film was investigated in this study. Polyolefin is usually adopted as a sealant material for general packaging system. Melting temperature of the HDPE film used in this study was 126oC. The heat seal temperature was controlled and varied at around melting temperature of HDPE precisely. The mechanical property of the sealed films was measured by a T-shape peeling test. Development molecular structure at film interface for sealing was evaluated in a wide angle x-ray diffraction pattern and changing of molecular orientation relaxation corresponding with the mechanical peeling property. Thermal property was also analyzed by a differential scanning calorimetry (DSC). The weight fraction of melting region in heat seal process was estimated from the DSC thermograms. We discussed that the amount of melting region is related to the major factor to decide peeling properties of heat sealed HDPE film.
THE SCIENCE OF MARRYING TECHNOLOGIES TO PRODUCE CROSSLINKED NANOCOMPOSITES-WHY?
An attempt was made to combine two existing technologies ƒ??nanocompositesƒ? and ƒ??crosslinkingƒ?. The goal of this work was to study the combined effects of nanoclay and crosslinking on the physical properties of polyamides. Tensile and flexural properties have been studied and reported. The effect of radiation dosage level on these properties has been looked at as well.The approach was to melt blend polyamide based polymers used in the medical industry with nanoclay and a crosslinking agent. The different polyamide based polymers used were nylon 12 and a polyether-block amide copolymer. The nanoclay used was Closite from Southern clay.
NOVEL POLYPHENYLENE ETHER-POLYSILOXANE BLOCK COPOLYMER
Polyphenylene ether is an engineering thermoplastic known for its excellent water resistance, dimensional stability and inherent flame retardancy. A triblock copolymer of polyphenylene ether-polysiloxane is produced by the oxidative coupling polymerization of 2,6-xylenol and eugenol-capped polysiloxane. This method of producing the copolymer is simpler than prior methods of preparing related copolymers by linking preformed polyphenylene ether and polysiloxane blocks. This paper describes the copolymer structure and the significant improvements in key properties such as impact resistance, flame retardancy and smoke generation obtained with the copolymer as compared to the polyphenylene ether homopolymer.
RELATIONSHIP BETWEEN FILM STRUCTURE DEVELOPMENT AND EXTRUDED FILM WIDTH IN T-DIE EXTRUDING OF HIGH DENSITY POLYETHYLENE
Molecular structure development and the deformation width and thickness behavior in T-die extruding of high density polyethylene (HDPE) was studied. The extruding through-put rate polymer material feeding rate and winding roll temperature were fixed. The velocity of winding roll was controlled and varied independently. The effect of processing condition was analyzed from molecular orientation distribution in machine direction (MD) to transverse direction (TD) by measuring optical retardation. To analyze crystalline structure development behavior of HDPE film wide angle x-ray diffraction (WAXD) pattern was also measured in TD of extruded film. The diffraction intensity distribution on the equator the meridian and azimuthal direction for (110) and (200) were evaluated. We discussed major factor to control film width and thickness. Relationship between molecular structure development and the external form of extruded film was studied.
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