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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MORPHOLOGY, MECHANICAL, AND RHEOLOGICAL BEHAVIOR OF MICROCELLULAR INJECTION MOLDED EVA-CLAY NANOCOMPOSITES
Ethylene Vinylacetate (EVA)/montmorillonite (MMT) nanocomposites diluted from master batch (50 wt%) with EVA and EVAgMA was used in this study. The organoclay EVA nanocomposites were then injection molded by conventional and microcellular methods. Nitrogen was used as the blowing agent. The effect of organoclay content and high/low MA grafted EVA on the mechanical, rheological properties of the EVA-clay nanocomposites was investigated. The results showed that the mechanical properties (tensile and impact) increased as the clay content increased. The high MA grafted EVA nanocomposites had better mechanical properties than that of low MA grafted EVA nanocomposites.
GATE LOCATION OPTIMIZATION IN INJECTION MOLDING BASED ON FEASIBLE SPACE
A methodology is presented in this paper to find the optimum gate location to achieve balanced flow so that a good quality part can be produced. The objective function is expressed in terms of injection pressure from the point of view of energy consumption. The coordinates of the gate location are chosen as design variables. A method is also proposed to determine the possible feasible space for gate location. The resulting optimization is solved by iterative search in the constrained space based on sequential linear programming algorithm. Examples are given to demonstrate the effect of the proposed method.
UV CURABLE COATINGS FOR CONTAINERS AND CLOSURES
The containers and closures market utilizes numerous decorating techniques on a variety of plastic and glass substrates. These decorating methods need to be functional as well as aesthetically pleasing. UV curable coatings can offer value to this market by providing high performance decorative coatings that are cost effective, easy to process and environmentally friendly. This paper will discuss the benefits of using UV curable coatings as an alternative to other ways of decorating containers, some challenges encountered in formulating coatings to meet all specifications of the containers and closures market, and typical performance and processing requirements.
THE ENVIRONMENTAL STRESS CRACKING RESISTANCE OF POLY-CARBONATE AS AN RESULT OF PROCESSING CONDITIONS AND INNER PROPERTIES
Environmental stress cracking is the most common failure reason of plastic parts. The influence of the processing conditions e.g. of the injection molding process on the environmental stress cracking resistance has not been investigated yet. Therefore several tests are carried out at the IKV. Test specimens are injection molded with different parameters for melt temperature, mold temperature and injection rate. These parameter variations cause variable inner properties of the molded parts. The environmental stress cracking resistance of specimens with different inner properties differs in a wide range. The results are discussed in detail.
BONDING POLYOLEFINS: WHAT ARE MY OPTIONS?
Since the first industrial production of polyethylene in the 1930's, polyolefin based plastics have become inescapable in our daily lives and indispensable to the production of modern industrial products. Although polyolefin based plastics such as Polyethylene and Polypropylene have proven useful in innumerable applications they have also proven difficult to bond to with adhesives. Advances in the field of bonding to polyolefin plastics have been made by the introduction of various surface pre-treatment methods and adhesives based on polyolefins themselves. Today we have new developments in the field of polyolefin bonding without the need for these cumbersome pre-treatment procedures.
DIFFERENTIAL INJECTION MOLDING METHOD FOR MULTI MICROPLASTIC PRODUCTS
In order to control metering accuracy and homogeneity of the very small quantities of melt in micro-injection molding process, and combine the advantages of micro-injection molding with conventional injection molding, differential injection molding method that uses conventional injection molding systems with a separate differential unit have been developed. The novel method can realize production of multi microplastic products. By using conventional injection molding with reciprocating screw injection systems, better plastication effect and mixing performance can be achieved. A planetary gear pump was employed as the differential unit, high metering accuracy could be achieved.
THE MECHANISM OF SKIN LAYER FORMATION WITHIN EPP PRODUCT PREPARED BY STEAM CHEST MOLDING AND ITS EFFECT ON INTER-BEAD BONDING ACROSS EPP PRODUCTS
Bead boundaries are potential fracture paths when a polymeric bead foam product is broken into pieces by force; the inter-bead bonding between beads tends to determine the mechanical properties of bead product. In our previous study, the formation mechanism of the inter-bead bonding in expanded polypropylene (EPP) bead foam processing with the steam chest molding process was proposed based on DSC simulation as well as tensile strength tests of products. In this study, the effect of skin layer on the density and tensile strength variations are assessed, and the mechanism of skin layer formation is proposed.
EFFECT OF COMPRESSED CO2 ON THE NON-ISOTHERMAL AND ISOTHERMAL CRYSTALLIZATION BEHAVIORS OF PLA AND PLA/TALC COMPOSITES
In this study, a regular and high pressure DSC were used to quantificationally assess the crystallinity development of PLA resin during the non-isothermal and isothermal crystallization processes. It is found that the plasticization effect of compressed CO2 could decrease linearly the Tg, and the increased chain mobility enhanced the crystallization dynamic of PLA at lower temperatures, while suppressed it at higher temperatures. Talc is one kind of nucleating agent and is often used in the polymeric foaming process. Its effect on the crystallization dynamic of PLA resin at various gas pressures was also investigated.
NANO-SILICA ADDITION IMPROVING CELL MORPHOLOGY AND EXPANSION RATIO OF PP COPOLYMER FOAMS BLOWN IN CONTINUOUS EXTRUSION
In this study, a block PP (BPP) copolymer with linear structure was selected and the nano-silica was used to challenge the fabrication of PP foam with uniform cell structure, high cell density and high expansion ratio . BPP foam exhibited poor cell morphology and low cell density at different die temperatures. An introduction of small amount of nanosilica dramatically improved the foaming behavior of BPP. Furthermore, the presence of nanosilica broadened the foaming window of BPP obviously. The effect of foaming on the dispersion of nanosilica in BPP matrix was also investigated in this study.
IMPROVING FLOW UNIFORMITY FROM A FILM DIE BY GEOMETRY MODIFICATION USING A THREE DIMENSIONAL FINITE ELEMENT OPTIMIZATION TECHNIQUE
This study shows how the flow uniformity from a film die can be improved by modifying the geometry of the die using a 3-D FEM optimization technique. A DOE is constructed based on the number of adjustable geometric parameters, and FEM simulations are run for the DOE cases. A response surface model is then created based on the DOE results, and is used to optimize the geometry to meet the desired objectives of uniform flow and minimal pressure drop. FEM simulations using the optimized geometry predict a more uniform flow at the die exit than simulations using the baseline geometry.
PERFORMANCE IMPROVEMENT ON ARAMID/POLYPROPYLENE COMPOSITE FOR HIGH VELOCITY IMPACTS
The aim of this work is to analyze the effect of adding a polymeric matrix to a weaved aramid textile for general applications in a bullet proof shield. Resistance to frontal impact with high speed projectiles was compared in two arrangements; woven aramid fibers and another composite made of the same fibers with a polypropylene matrix. The methodology for this comparison consisted in establishing a fixed impact energy (93 Joules) using an arrangement of Kevlar?? 129 with and without thermoplastic matrix, in order to find the corresponding configuration to its ballistic limit at that energy.
CRYSTALLIZATION OF HIGH-DENSITY POLYETHYLENE: THE EFFECT OF SHEAR & UNIAXIAL EXTENSION FLOWS
In this paper, the effects of shearing, uniaxial extension and temperature on the flow induced crystallization of a high-density polyethylene (HDPE) are examined using rheometry. Extensional flow found to be a stronger stimulus for polymer crystallization compared with that of simple shear. Generally, strain and strain rate found to enhance crystallization in both simple shear and elongation at temperatures around the meting point. At temperatures well above the melting point, polymer crystallized under elongational flow while there was no crystallization under simple shear flows.
MORPHOLOGY AND PROPERTIES OF POLYLACTIDE AND POLYCARBONATE BLENDS
PLA was melt-blended with polycarbonate (PC) modified with high molecular weight bisphenol A type modifier. Both the mechanical properties and the thermal properties were investigated. The blends showed two distinct glass transition behaviors. Glass transition temperatures of the PLA phase were literally not changed. On the other hand, the glass transition temperature of the PC phase moved toward Tg of PLA with the addition of the modifiers, suggesting some degree of interactions. Microscopic observations revealed non-uniformly dispersed PC inclusions in the PLA matrix, confirming that phase separation has occurred.
THE INTERDIFFUSION OF POLYMERIC GRADIENT REFRACTIVE INDEX (GRIN) LENS MATERIALS
The interdiffusion of two miscible polymers used to fabricate GRIN lenses, polymethylmethacrylate (PMMA) and poly(styrene-co-acrylonitrile) (SAN17) with 17% AN content, was studied as a function of contact time during a multilayer coextrusion process. Oxygen permeability increased from following the series model to following a miscible blend model as the number of layers increased from 17 to 1025. A model relating permeability and the interdiffusion state within the layers successfully predicted the observed permeability trends, and was used to determine the mutual diffusion coefficient of PMMA and SAN17.
STRUCTURE AND PROPERTIES OF PENTABLOCK AND TRIBLOCK COPOLYMER BLENDS
Styrene-ethylene/butylene styrene (SEBS) block copolymers are used in a wide range of film and molded applications, particularly where good weatherability (i.e. UV resistance) is needed. These block copolymers also have poor moisture transport characteristics. NexarTM is a family of pentablock copolymers recently developed by Kraton Polymers LLC, whose properties include (a) high water vapor transport, (b) good mechanical integrity, both dry and wet, (c) thermal and chemical resistance, and (d) ion selectivity. The purpose of this work was to create elastomeric films that have moisture transport properties and, to investigate the structure and properties of SEBS / Nexar's blends
ULTRASONICALLY ASSISTED EXTRUSION OF CARBON BLACK, CARBON NANOFIBER AND CARBON NANOTUBE FILLED STYRENE-BUTADIENE RUBBER COMPOUNDS AND PROPERTIES OF THEIR VULCANIZATES
Ultrasonically assisted extrusion of styrene-butadiene rubber (SBR) compounds filled with carbon black (CB), carbon nanotube (CNT) and carbon nanofiber (CNF) was carried out. The effects of ultrasonic amplitude on extractable amount, swelling behavior, mechanical properties, abrasion, electrical resistivity and morphology were investigated. Ultrasonic treatment at certain amplitudes led to an increase of the crosslink density, modulus and tensile strength. Also, it caused a reduction in the electrical percolation threshold. A better dispersion of ZnO and creation of unique nanofiller agglomerates were observed by means of scanning electron microscopy (SEM), atomic force microscopy (AFM) and optical microscopy.
NEW DEVOLATILIZATION PROCESS FOR THERMOSENSITIVE AND HIGHLY VISCOUS POLYMERS IN HIGH VOLUME KNEADER REACTORS
The achievable final volatile content within kneader devolatilization processes is highly dependent on the final melt temperature. For thermosensitive polymers the state of the art process performs poorly. The amount of dissipated energy leads to a heat up of the polymer, limiting the maximal kneader shaft speed and therefore volatile removal rate. This new process uses a suitable additional volatile compound to cool off the dissipated energy by evaporation using the off gas to strip and boost the mass transfer coefficient. A complex multi-parameter study is presented, to predict performance of industrial equipment from pilot scale data.
EFFECTS OF GLASS FIBERS ON THE PROPERTIES OF MICRO MOLDED PLASTIC PARTS
Glass fibers are used to reinforce plastics and to improve their mechanical properties. But plastics filled with glass fibers are concern for molding of micro parts. The aim of this paper is to investigate the effects of glass fiber on the replication quality and mechanical properties of polymeric thin ribs. It investigates the effect of feature size and gate location on distribution of glass fibers inside the molded parts. The results from this work indicate that glass filled plastic materials have poor replication quality and non-homogeneous mechanical properties due to the non-uniform distribution and orientation of glass fibers.
VISCOELASTICITY OF POLYMERS; FUNDAMENTALS, APPLICATIONS, AND CASE STUDIES
In this review paper the fundamentals of polymer viscoelasticity will be explained and its applications to different polymers will be discussed. Firstly, the viscous-state properties like viscosity, shear thinning, Newtonian flow, and molecular structure will be explained. Secondly, the solid-state properties like the storage modulus, loss modulus, thermal stability, and molecular mobility will be clarified. The relation of these properties to the thermo-mechanical properties of different polymers and nano-composites will be reviewed as well. Finally, a successful story of using viscoelasticity as a failure analysis tool will be summarized.
STRUCTURAL RELAXATION AND PHYSICAL AGING OF POLYSTYRENE IN NANOLAYER CONFINEMENT
Layer-multiplying coextrusion technology was used to produce multilayered films of polystyrene (PS) and polycarbonate (PC). The multilayered films with PS layer thickness down to 20nm were extruded. The structural relaxation of polystyrene under PC confinement was investigated using two approaches. In the first method, the PS layers were cooled from the melt at different rates. The subsequent heating thermograms revealed that the relaxation of the PS was similar to the bulk sample. Another experiment included physical aging of PS layers below the Tg at 80?øC. The subsequent heating thermograms showed that the aging rate of PS remained unchanged under confinement.
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