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Conference Proceedings
TEXTILE INSERTED SANDWICH STRUCTURE BY INJECTION-PRESS MOLDING
The current study is to research the sandwich molding process of both the plate type reinforced material inserted sandwich structure and the textile inserted sandwich structure. The sandwich molding process in this study consists of injection molding process and injection-press molding process. The sandwich plate type insert glass fiber-reinforced polypropylene (GFPP) instead of textile was studied mainly. Additionally, the relationship between the improvement of strength and the lightening of weight was investigated through controlling the position of the plate type insert of GFPP in the sandwich structure. It is found that this sandwich molding process was effective in controlling position of the insert in the sandwich structure. And through controlling position of the insert, this sandwich process was possible to improve the strength and to lighten the weight by reducing thickness of the sandwich structure.
ENVIRONMENTAL HEALTH AND SAFETY ISSUES AND APPROACHES FOR THE PROCESSING OF POLYMER NANOCOMPOSITES
In 2005 Environmental Defense and DuPont entered into a partnership to develop a framework that seeks to identify and address potential environmental health and safety (EH&S) risks of nano-scale materials. The Nano Risk Framework was published to establish a systematic and disciplined process to identify and reduce potential risks during nanomaterial development and meet continued product stewardship commitments [1]. This paper describes an approach developed for and the application of the Framework to the processing of polymer nanocomposites at laboratory and semi-works scales. Carbon nanotubes were melt-blended into a polymer matrix with a batch mixer to improve mechanical and electrical properties.Nano-TiO2 nanocomposites were made on laboratoryand semi-works extruders. These case studies exemplify DuPontƒ??s approach to handling nanomaterials in the product research and evaluation phase of development.Utilization of the Framework enabled further refinement of internal EH&S management procedures and to identify questions to be answered for such applications before they move to commercialization.
NOVEL SILOXANE BASED CORE-SHELL IMPACT MODIFIERS
Core-shell impact modifiers are special class of elastomers, which can be tailored to possess special functional groups and wide range of desired particle sizes. Such structural modifications can result in achieving miscibility or compatibility enabling desired/enhanced properties in polymeric compositions. A core-shell impact modifier based on siloxane core and polystyrene shell, with tunable particle size was synthesized by emulsion polymerization. The performance of synthesized material was evaluated in polyphenylene ether (PPE) formulations and compared with that of styrene block copolymers.
PROCESSING FINE-CELLED RECYCLABLE CBA-BASED POLYOLEFIN
FOAMS IN COMPRESSION FOAM MOLDING
This paper focuses on understanding the technological
potentials for producing recyclable polyolefin foams by
using a modified technique of the conventional
compression molding process, referred to as compression
foam molding. A two-step compression foam molding
method is being developed. The main processing feature
of this method is that it allows for complete sintering of the
non-foamable resin prior the activation of the CBA. First,
completely sintered intermediate foamable products that
have no pre-decomposed CBA particles and entrapped air
bubbles are manufactured. Second, these intermediate
products are used in the actual foaming process. The
principal advantage of this compression foam molding
method is that it produces high quality recyclable foamed
structures with high volume expansion ratios by avoiding
the need for cross linking.
TRUE 3D NUMERICAL SIMULATION IN INJECTION COMPRESSION MOLDING (ICM)
Generally, injection compression molding (ICM) can provide better product quality than that of conventional injection molding (CIM) in some injection processes and products, such as micro-injection molding, less residual stress parts, and so on. To get a better understanding of ICM, a 3D simulation technology based on finite volume method is proposed. In this study, the influence of various process parameters with ICM is performed by using light guide plate (LGP) models. The cavity pressure distribution with ICM is lower and more uniform than that with CIM which will have more opportunities result in lower volume shrinkage and get better product quality.
MECHANICAL PROPERTIES OF RECYCLED PET/PP INJECTION MOLDINGS
Compatibilization effects on the phase morphology and mechanical properties of post-consumer recycled poly(ethylene terephathalate) (RPET)/ polypropylene (PP) blends were investigated. The blending of RPET and PP (RPET/PP:95/5) was carried out by a singlescrew extrusion process in the presence of various amounts of compatibilizer ranging from 0-35 phr based on the PP content. The compounded materials were injection molded into dumbbell test pieces which were subsequently used for mechanical and morphological characterizations. The addition of compatibilizer of up to 15 phr resulted in a size reduction of the dispersed phase while an apparent increase in density of the blends suggests an improvement in interfacial interaction following the depletion of hollow ligaments between the PP and RPET phases. The changes in morphological structure significantly affect the tensile and impact resistance of the moldings. An elongation at break (EB) of more than 350% could be achieved with the incorporation of just 15 phr of compatibilizer (as compared to <90% EB for un-compatibilized specimens) while significantly better impact performance was observed in all compatibilized specimens.
MICRO-FEATURE REPLICATION OF CYCLIC OLEFIN COPOLYMER AT ELEVATED MOLD TEMPERATURE
The focus of this study is on the ability of Cyclic Olefin Copolymer (COC) to replicate micron and sub-micron features when molded at an elevated mold temperature without externally applied pressure. Molding was performed on a treated silicon mold containing surface features as small as 700nm in depth with aspect ratios ranging from 5 to 0.02. In this study temperature was selected in order to overcome the viscosity resistance of polymer based on contact angle (wettability) measurements. Since increasing mold temperature can cause sticking to the mold surface an anti-adhesive layer made by TCS has deposited on the surface to facilitate mold release. Feature replication was assessed using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) to compare the molded feature depth ratio and surface roughness. It was observed that for the features with an aspect ratio (depth/width) bigger than 0.8 the quality of the feature replication declines. Without the anti-adhesive layer COC has shown rough surface finish especially in low aspect ratio features because of sticking to the silicon oxide layer. Using anti-adhesive improved surface finish of molded part and reduced the defects such as flashing and tear-off during demolding.
MICRO-FEATURE REPLICATION OF CYCLIC OLEFIN COPOLYMER AT
ELEVATED MOLD TEMPERATURE
The focus of this study is on the ability of Cyclic
Olefin Copolymer (COC) to replicate micron and
sub-micron features when molded at an elevated mold
temperature without externally applied pressure. Molding
was performed on a treated silicon mold containing
surface features as small as 700nm in depth with aspect
ratios ranging from 5 to 0.02. In this study, temperature
was selected in order to overcome the viscosity resistance
of polymer based on contact angle (wettability)
measurements. Since increasing mold temperature can
cause sticking to the mold surface, an anti-adhesive layer
made by TCS has deposited on the surface to facilitate
mold release. Feature replication was assessed using
Scanning Electron Microscopy (SEM) and Atomic Force
Microscopy (AFM) to compare the molded feature depth
ratio and surface roughness. It was observed that for the
features with an aspect ratio (depth/width) bigger than 0.8
the quality of the feature replication declines. Without the
anti-adhesive layer, COC has shown rough surface finish
especially in low aspect ratio features because of sticking
to the silicon oxide layer. Using anti-adhesive improved
surface finish of molded part and reduced the defects such
as flashing and tear-off during demolding.
NANOLAYERING AS AN ENABLING TECHNOLOGY FOR STUDYING FRACTIONATED CRYSTALLIZATION OF POLYPROPYLENE
Layer-multiplying coextrusion was used to fabricate assemblies of 257 layers in which PP nanolayers alternated with thicker polystyrene (PS) layers. When the assembly was heated into the melt interfacial driven breakup of the 12 nm PP layers produced a dispersion of submicron PP particles in a PS matrix. In the absence of a nucleating agent the submicron particles obtained from breakup of 12 nm PP layers crystallize almost exclusively by homogeneous nucleation at about 40 ºC. Addition of a nucleating agent to the PP layers offers a unique opportunity to study the nature of heterogeneous nucleation.
NANOLAYERING AS AN ENABLING TECHNOLOGY FOR STUDYING FRACTIONATED CRYSTALLIZATION OF POLYPROPYLENE
Layer-multiplying coextrusion was used to fabricate assemblies of 257 layers, in which PP nanolayers alternated with thicker polystyrene (PS) layers. When the assembly was heated into the melt, interfacial driven breakup of the 12 nm PP layers produced a dispersion of submicron PP particles in a PS matrix. In the absence of a nucleating agent, the submicron particles obtained from breakup of 12 nm PP layers crystallize almost exclusively by homogeneous nucleation at about 40 ?§C. Addition of a nucleating agent to the PP layers offers a unique opportunity to study the nature of heterogeneous nucleation.
THREE-DIMENSIONAL MODELING OF GAS PENETRATIONS DURING GAS-ASSISTED INJECTION MOLDING
Although Gas-Assisted Injection Molding (GAIM) has gained acceptance in eliminating sink marks and preventing warpage in the plastic industry, many problems are still encountered for the complicated gas-melt flow interactions. In this study, a full 3D numerical approach is proposed to model GAIM process. The behavior of gas penetration are investigated numerically. Simulation results are in the form of fully featured 3-D animations, giving highly realistic images of flow fields. The predicted melt front location and gas penetration behavior show good agreement with the experimental results, and several complex applications are shown as well.
MECHANICAL PROPERTIES OF HEAT-SEALED PART IN THERMAL LAMINATED FILM
Plastic packaging has been a very important application that significantly improved our way of living. One of the most common forms of plastic packaging is the plastic bag which is often heat sealed at several ends. In order to increase the heat-seal performance of plastic bags laminated films e.g. oriented PP/cast PP have been used.However much solvent is used during the laminating process and the effects of volatile compounds on health and environment were the main concerns when introducing these solvents. Hence in this study a new lamination process i.e. thermal lamination was developed to avoid the usage of solvents. The characteristics of the thermal laminated films as well as their mechanical properties upon heat-sealing are discussed.
MECHANICAL PROPERTIES OF HEAT-SEALED PART IN THERMAL
LAMINATED FILM
Plastic packaging has been a very important application
that significantly improved our way of living. One of the
most common forms of plastic packaging is the plastic
bag, which is often heat sealed at several ends. In order
to increase the heat-seal performance of plastic bags,
laminated films e.g. oriented PP/cast PP have been used.
However, much solvent is used during the laminating
process and the effects of volatile compounds on health
and environment were the main concerns when
introducing these solvents. Hence, in this study, a new
lamination process, i.e. thermal lamination, was
developed to avoid the usage of solvents. The
characteristics of the thermal laminated films as well as
their mechanical properties upon heat-sealing are
discussed.
MECHANICAL PROPERTIES OF INJECTION-MOLDED JUTE/GLASS REINFORCED HYBRID COMPOSITES
Bio-composites are generally made from natural fibers as reinforcement and a biodegradable polymer matrix such as poly(lactic acid) or poly(caprolactone).However the mechanical properties of these composites are relatively low. For practical applications glass fibers were added to create hybrid composites. The concept of ƒ??degree of greenƒ? is introduced to identify the true content of biodegradable material in the composite. Three different fiber hybridization methods are proposed i.e.dry blending mixing of pellets and sandwich injection molding. The mechanical properties of these hybrid composites are evaluated and the relation between the properties and degree of green is discussed.
DEVELOPMENT OF MOISTURE RESISTANT RECYCLED POLY(ETHYLENE TEREPHTHALATE)
The recycling activities related to poly(ethylene terephthalate) PET has been slow since the material is always thought to possess inferior properties when compared to virgin PET. This study involves the development of novel processing methods to significantly enhance the properties of recycled PET (RPET) especially in terms of moisture resistance.This is particularly important especially when RPET is used for further processing that involves heating such as injection molding since the presence of moisture would severely degrade the material. The drying process of RPET pellets would also require at least a few hours which could significantly affect production cycles. The improvement in moisture resistance can be realized through the control of crystallinity and morphological structure of the RPET pellets during compounding and extrusion processes.
INVESTIGATION ON VARIOUS VARIOTHERM PROCESSES IN INJECTION MOLDING
In recent years, to eliminate defects and improve the product quality, many variotherm processes have been proposed and commercialized in injection molding. However, what the true function is for each technology and how the efficiency is from one technology to the other, are still not clear. In this study, we have systematically conducted various technologies, including Conventional Injection Molding (CIM), Rapid Heat Cycle Molding (RHCM), Induction Heating Molding (IHM), and Electricity Heating Mold (E-mold) by using 3D Transient Cool technology. The functions and the heating-cooling efficiency for each technology can be visualized. The comparison for all technologies is also performed.
DEGRADATION BEHAVIOR OF HEMP FIBER REINFORCED THERMOSETTING POLYMER
Natural fiber-reinforced composites are very attractive due to environmental considerations. There are currently many types of natural fibers that are suitable to be used as reinforcement in polymer composites. In this paper hemp fiber mat was selected to be the reinforcement for unsaturated polyester resin. In order to determine the long-term water resistance of this composite specimens were immersed into hot water.Weight changes of the specimens were recorded with time and their respective mechanical properties were determined through bending tests. A correlation was established between moisture absorption and mechanical performance of the composites.
STUDY OF POLY(1-BUTENE) SURFACE MODIFIED BY AIR PLASMA TREATMENT
A low-temperature pulsed direct current discharge air plasma treatment has been used to improve the surface properties of poly(1-butene) films. The changes in the surface hydrophilicity and roughness of modified poly(1-butene) films were investigated by contact angle measurements, scanning electron microscopy and atomic force microscopy. These experiments revealed that the plasma treatment can greatly change the surface chemistry as well as morphology of poly(1-butene). The polar functional groups generated due to plasma treatment on the surface of poly(1-butene) sheets causes decrease in contact angle. However, the aging process of the plasma treated samples showed that the effect was not permanent. Scanning electron microscope and atomic force microscope observations revealed that the surface topography was changed by air plasma etching, and the surface roughness increases.
POLYLACTIDE TOUGHENING USING IMPACT MODIFIERS
The major objective of this research was poly(lactide) (PLA) toughening using two impact modifiers (IMs). IM1 was derived from biodegradable resource and IM2 was non-degradable ethylene-acrylate copolymer. Blend films were prepared using a single screw extruder, and their mechanical properties were measured using tensile testing. Results showed that the Young's modulus did not change significantly with increasing concentration of IM1, but decreased with IM2 concentration. The maximum elongation at break was 240% for IM1 at 8 wt% loading and 255% for IM2 at 12 wt% loading. Clarity of the films decreased with higher additive concentrations for both IMs, but IM1 gave clearer film than IM2 for given composition. AFM images showed IM1 dispersed in PLA as isolated islands at lower compositions and transitioned to short threads at higher compositions; IM2 existed mostly as islands. Annealing of the films at 100 ?§C for 1 h increased the percent crystallinity, but did not affect the mechanical properties significantly.
THE WARPAGE AND OPTICAL PROPERTY INFLUENCED BY THE PROCESS-INDUCED PROPERTY VARIATION IN MULTI-COMPONENT MOLDING
Sequential multi-component molding is one of great methods to fabricate the modern injection products. Previous literatures have shown that various parameters, including the product geometries and materials selection, will affect the warpage of final products significantly. However, the interaction between the first shot and the second shot is not clear. In this study, various process-induced properties of the first shot are taken into consideration for the further processing. Results, not only show that the process-induced properties can affect the warpage and optical property crucially but also further help discover the inside mechanism more comprehensively.
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