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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MODELING OF ANISOTROPIC POLYMERS DURING EXTRUSION
It is known that a liquid crystal polymer (LCP) melt aligns in the direction of the shear flow when it passes through an extrusion die. This alignment causes thin films of the anisotropic LCP material to display different properties in different directions. To overcome this problem, many complex die design technologies have been developed that involve moving surfaces. However, there is a clear need to develop a method of predicting crystal orientation (alignment) to aid in die design. This paper investigates different modeling methods, and develops a numerical modeling technique using FLUENT.
THE ROLE OF PLASTICATION IN PURGING EFFICIENCY AND MOLDED PART QUALITY FOR RECIPROCATING SCREW INJECTION MOLDING MACHINES
One third of plastics are processed via injection molding. The process is versatile for making three dimensional parts weighing from fractions of a gram to several hundred pounds. Many types of resins are used commercially. Resins come in different colors and different additives and fillers. Changing from one resin or color to another involves an inordinate amount of money and time which is invested to remove the previous resin or color. Many commercial purging aides are available and many procedures are found in the literature miss the point since the basic principles causing the purging inefficiency are not well understood.
TOPOLOGICAL EFFECTS IN POLYACRYLAMIDE HYDROGELS
Viscoelastic response of polyacrylamide hydrogels prepared by free radical copolymerization of acrylamide and N,N-methylenebisacrylamide in presence of linear polyacrylamide (L-PAA) chains is investigated. The presence of high-MW L-PAA chains contributes very significantly to the intermolecular excluded volume interaction and, hence, decreases the degrees of freedom of chain strands forming the hydrogel network. This sort of trapped entanglement interaction affects significantly the network mechanical behavior. Presented viscoelastic data show that the addition of L-PAA chains into the hydrogel changes not only the linear elastic modulus of the network, but also imposes an unusual relaxation behavior in to the hydrogel.
EXTRUSION FOAMING OF CELLULOSE FIBER REINFORCED POLYLACTIC ACID BIOCOMPOSITES
This paper investigates the effects of matrix type, cellulose and die temperature on the foaming behavior of cellulose fiber reinforced polylactic acid (PLA) biocomposites in extrusion. Two types of PLA (amorphous and crystalline) as a polymer matrix and CO2 as a physical blowing agent were used. The results suggest that pure crystalline PLA resulted in a better foaming behavior than pure amorphous PLA, but the polymer matrix type had little affect on the foaming behavior of the composite materials. Additionally, the cell density and the foam density of pure crystalline PLA and composites decreased with a decrease in die temperature.
COMPOSITE STRUCTURES WITH GOOD CHEMICAL RESISTANCE AND HIGH PERMEABILITY TO MOISTURE VAPOR
Composite structures combining fabric and film are used in applications where barrier protection and moisture permeability are important. For example, protective garments require moisture permeability for the wearer's comfort, and moisture permeable protective covers for equipment to avoid condensed moisture induced corrosion or mold growth. . Recently, new ionomers having novel performance (increased selective gas transmission while maintaining mechanical properties) have been developed. In this paper, we discuss their use in film structures which have both good barrier protection,, mechanical properties and appropriate moisture transmission properties.
EFFECTS OF TIME AND TEMPLATE PORE SIZE ON THE MORPHOLOGY OF POLYMER NANOSTRUCTURES FORMED WITH THE TEMPLATE ASSISTED METHOD
The template assisted method is a simple, cost effective technique that can be used to fabricate polymer nanotubes. In this study, the solution wetting technique was used to form polystyrene elongated nanostructures in anodized aluminum oxide templates. The effects of time and template pore size were studied to determine the role each parameter plays in the final morphology. It was found that for PS solutions with high molecular weight polymer, hollow nanotubes can be formed for time periods <18hr, whereas low molecular weight polymer forms solid nanorods. Additionally, relatively large pore diameters of ~200-300 nm are necessary to form nanotubes.
EFFECT OF PELLET SIZES ON MOISTURE ABSORPTION AND THERMAL DECOMPOSITION KINETIC OF RECYCLED PET/RECYCLED PP BLEND
This study considers the effects of pellet geometry on its moisture absorption and thermal decomposition kinetic of recycled polyethylene-terephthalate (RPET) and recycled polypropylene (RPP) blend. Flynn-Wall-Ozawa (FWO) was used for the kinetic study, which it was suitable for thermal degradation of RPET/RPP blend in N2 while the second order polynomial was fitted for degradation in air. Finer powders were found to have higher moisture absorption rates due to their large surface area although they could also be easily dried. Meanwhile, larger pellets exhibited higher degradation activation energies, which suggest that they are more resistant to thermal degradation than smaller grains.
SEALANT RESINS BASED ON ETHYLENE COPOLYMERS CONTAINING BIOSOURCED MODIFIERS
Ethylene ionomers, such as Surlyn from DuPont, have long been used as packaging sealants because of their good mechanical properties and formability combined with excellent seal strength over a wide sealing temperature range, seal integrity in the presence of contamination, and hot tack. Ionomers can be modified with biosourced additives, such as fatty acids to modify their mechanical and barrier properties. In this paper we discuss blending these recently developed ionomers with commercially available ethylene copolymers to achieve films containing 20% -40% renewable content having a good balance of sealant and mechanical properties.
3D MODELLING OF FILTRATION PROCESS THROUGH POLYMERIC NANOFIBER BASED NONWOVENS
Full 3D particle filtration modeling at low pressures considering slip/transition/free molecular flow regime, particle-fiber interactions, air/particle slip, sieve and homogenous flow field has been performed for the polyurethane nanofiber filter prepared by electrospinning process. The obtained theoretical predictions for the filtration efficiency have been compared with the corresponding experimental data and good agreement between both data sets has been obtained. In order to take all real structure features of the nanofiber filter into account (such as varying fiber diameter, curvature, inhomogeneity, defects), a new approach for 3D nanofiber mat model construction from corresponding SEM images has been proposed and utilized.
THE DEPENDENCY OF POLYLACTIDE CRYSTALLIZATION BEHAVIOR ON THE CHAIN BRANCHING AND NANO-CLAY CONTENTS
The crystallization behavior of Polylactide with different chain extenders and nano-clay contents were investigated using a differential scanning calorimeter (DSC). The results of As Received PLAs show that the branched structure plays the role of crystal nucleating agent. Also, the compounding process on the branched PLAs improves the crystallinity significantly due to the completion of branching reactions. The results of PLA-nanoclay show that the addition of nanoclay in different loadings does not have a significant effect on melt crystallization of half and fully branched PLAs compared with processed branched PLAs, but improve the crystallinity of linear PLA during isothermal crystallization.
NATURAL WEATHERING VS. ACCELERATED UV IRRADIATION ON MECHANICAL PROPERTIES IN POLY(1-BUTENE)
The work directs attention towards the influence of natural weathering and accelerated UV degradation on resulting macroscopic properties in isotactic poly(1-butene). For this purpose, commercial-available poly(1-butene) was extruded as tape. Two sets of prepared specimens were UV irradiated up to 300 hours and naturally weathered up to 103 days. Significant changes were consequently observed in evolution of mechanical properties where was observed a drop of tensile strength and elongation at break, while tensile modulus shows different trend caused by phenomenon of chemicrystallization. Evolution of chemical species in specimens was observed using infrared spectroscopy and surface changes were observed by stereomicroscopy.
MISCIBILITY OF POLYOXYMETHYLENE AND POLY(LACTIC ACID)
Polymer blend or alloy provides the good mechanical performances and thermal properties. However, the different kinds of polymers are immiscible, which indicated by phase separation structure and declination of mechanical properties. In this study, we investigated the miscibility of various ratio of POM/PLA blends and their effect on thermal and mechanical properties of POM/PLA blends. The miscibility of POM/PLA blends could confirm by single melting temperature and no phase separation. The incorporation of PLA into POM significantly affected both thermal and mechanical properties, which could be attributed to the embedding of submicron PLA domains amongst the amorphous regions of POM.
MODELING OF NON-ISOTHERMAL FILM BLOWING PROCESS FOR NON-NEWTONIAN FLUIDS BY USING VARIATIONAL PRINCIPLES
In this work, non-isothermal film blowing process analysis for non-Newtonian polymer melts has been performed theoretically by using a minimum energy approach and the obtained predictions were compared with both, theoretical and experimental data (internal bubble pressure, take-up force, bubble shape, velocity and temperature profiles) taken from the open literature. For this purpose, recently proposed generalized Newtonian fluid depending on three principal invariants of the deformation rate tensor, D, and its absolute defined as square root of D*D has been used. It has been found that film blowing model predictions are in very good agreement with the corresponding experimental data.
OBSERVATION OF BANDED SPHERULITES IN WATER-ASSISTED AND CONVENTIONAL INJECTION MOLDED LLDPE/HDPE BLENDS
Crystal morphologies of LLDPE and its miscible blends with HDPE obtained by water-assisted injection molding (WAIM) and conventional injection molding (CIM) were examined. Banded spherulites formed in both WAIM and CIM pure LLDPE parts. In CIM parts, a clear banding to non-banding morphological transition occurred for LLDPE upon blending with HDPE. However, for WAIM parts, banded spherulites of LLDPE still formed in outer and inner zones upon blending with HDPE, but the bands became irregular. In core zone of WAIM parts, a clear banding to non-banding morphological transition for LLDPE was observed when HDPE content was increased to 30 wt%.
DEVELOPING PHB/WOOD FOUR/CELL DEBRIS COMPOSITES THROUGH EXTRUSION
Polyhydroxybutyrate (PHB)-based wood plastic composites (WPCs) are superior to ordinary petroleum-based WPCs in terms of environmental protection. However, PHB is more expensive than many of the commodity petrochemical polymers because of the costly separation and purification processes, which could be avoided by directly using PHB-laden bacteria to produce PHB-based WPC. This study investigated the processing parameters, mechanical properties, and water resistance of the extruded composites with varying component ratios. The results indicate that some of the composites had outstanding properties compared with a commercial WPC. Therefore, this renewable WPC can replace petroleum-based WPCs on current markets without sacrificing product performance.
DEVELOPMENT OF THERMALLY CONDUCTIVE AND ELECTRICALLY INSULATING POLYMER COMPOSITES FOR ELECTRONIC PACKAGING APPLICATIONS
This paper discusses the development and modeling of novel polymer composites that possess multifunctional properties demanded by electronic packaging applications. In this work, a thermal conductivity analyzer was designed and implemented to measure composites effective thermal conductivity (keff). An analytical model was established to predict keff of composites filled with spherical fillers. Using this model, together with experimentally-measured keff, a semi-empirical approach was developed to study the effects of polymer-filler interfacial properties on keff.
THE EFFECT OF MELT ROTATION TECHNOLOGY ON PARTICLE DISTRIBUTION DURING INJECTION MOLDING
The melt rotation technology has been proposed to reduce the distribution variations of filler particles due to shear-induced migration in injection molded parts. The technique had been successfully employed to address the filling imbalances due to shear gradients formed during the polymer flow through runners. An experimental analysis has been carried out this time for a filled polymer. Glass-filled polypropylene has been injection molded using a multi-cavity mold system both with and without melt rotation implementations and parts have been analyzed by microscopic imaging. The preliminary results suggest that application of melt rotation results in more balanced filler concentration levels.
THE EFFECT OF CHAIN BRANCHING ON THE CRYSTALLINITY BEHAVIOR OF POLYLACTIDE WITH THE PRESENCE OF DISSOLVED CO2
This paper investigates the effect of chain extender on the crystallinity behavior of Polylactide with/without the presence of dissolved CO2 by a high-pressure differential scanning calorimeter (HPDSC). It is shown that without CO2, the crystallinity increases by decreasing the branched structure due to better chain regularity. With the presence of low-pressure (15bar) CO2, the crystallinity of PLAs significantly increased due to CO2ƒ??s great plasticization effect. However, with the increase of pressure (from 15bar to 45bar), crystallinity dramatically decreases, even though more CO2 is dissolved. However, as the pressure increases from 45bar to 60bar, the crystallinity of all PLAs dramatically increases.
ENGINEERING UP POLYPROPYLENE COMPOSITES WITH ORGANOSILANES
Modification of polypropylene resins with ñ,ý-unsaturated carboxylic functional-silanes by melt extrusion processing in presence of free radical initiator was demonstrated while preventing significantly undesired ý-scission phenomenon in comparison to prior work on vinyl- and methacryloxy-silanes. Modified PP was then used for enabling crosslinking into injected parts, showing enhanced high temperature resistance for both neat PP resin or glass-fibers-PP composites. Another improvement was water uptake in wood-fibers PP composites, which resulted in significant improvement of impact and tensile properties and stability under heat and water aging. Relevance of this work will be discussed in applications such as Automotive, Appliance, and Building.
MANIPULATION OF POLYMERIC BIODEGRADATION CHARACTERISTICS BY VIBRATION ASSISTED INJECTION MOLDING
The wide variety of biomedical applications employing biodegradable polymers requires a similarly wide range of biodegradation properties. In this study, a dynamic melt manipulation technique in injection molding has been investigated as a low cost, high volume manufacturing alternative to respond these requirements. The technique utilizes an additional oscillatory motion during injection molding to induce molecular alignment of polymer molecules in the final product. Preliminary experimental results have indicated that biodegradation process is dependent on these orientation levels and therefore polymeric medical devices with different degradation characteristics can be obtained simply by changing the manufacturing parameters.
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