SPE Library

Ultra high speed injection molding plays a more significant role in molding thin-wall part in recent 3C products. Systematic studies on the proper molding window of Secure Digital (SD) card housing of 0.25 mm thick using ultra high speed injection molding have not yet been reported. In this study, a proper molding window for SD card housing using ABS and HDPE by varying mold temperatures from 30 ƒ?Ÿ to 100 ƒ?Ÿ and injection speeds from 100 mm/sec to 1200 mm/sec was investigated in details. Molded dimension and weight were measured experimentally. It was found that higher mold temperature and faster injection speed are two critical molding parameters that leading to good moldablilty for SD card housing.

Toughening mechanisms in relation with the hierarchical structure of PVC by incorporating a cross-linked PVC based on microscopic was investigated The microscopic observations of the damage zone ahead of the notch showed that many voids initiated from primary PVC particles in the gelation of 61% . As further increase in gelation, an internal craze ahead of the local shear yield zone is observed at the tip of a notch. Brittle fracture occurred within 40wt% content of cross-linked PVC, whereas a stable cracking and/or crazing observed over 50wt% content. Nevertheless, the gelation of this sample showed 79% and the primary particles had already disappeared; the structure of craze was quite deferent form that of pure PVC. The mechanisms of yielding were not affect on hierarchical structure of PVC whereas the mechanisms of crazing was strongly affect on the hierarchical morphology.

Electrical polymer composites for molding of bipolar plate are easily fabricated. In this study PPS filled with 50wt% carbon fiber (CF) and PPS mixed with 50wt% CF + 20wt% Graphite (GP) were used for injection molding of a bipolar plate to study the associated fiber orientation and distribution and their effects on surface conductivity under various molding conditions. The flat plates were both convectional injection molded (CIM) and injection compression molded (ICM). In-plane conductivity (IPC) and through-plane resistance (TPR) of the bipolar plates was measured. Under proper molding conditions TPR and IPC can be improved by 54% and 48% respectively in CIM whereas TPR was improved by 70% and IPC improved by 184% in ICM. IPC can reach 156S/cm when molded by ICM.

Electrical polymer composites for molding of bipolar plate are easily fabricated. In this study, PPS filled with 50wt% carbon fiber (CF) and PPS mixed with 50wt% CF + 20wt% Graphite (GP) were used for injection molding of a bipolar plate to study the associated fiber orientation and distribution and their effects on surface conductivity under various molding conditions. The flat plates were both convectional injection molded (CIM) and injection compression molded (ICM). In-plane conductivity (IPC) and through-plane resistance (TPR) of the bipolar plates was measured. Under proper molding conditions, TPR and IPC can be improved by 54% and 48%, respectively, in CIM, whereas TPR was improved by 70% and IPC improved by 184% in ICM. IPC can reach 156S/cm when molded by ICM.

Efficiency and quality are essential demands in mold design/making and molding industry. This study utilizes the knowledge-based concept and database driven platform combined with 3D drawing software to develop an integrated mold-design/making and molding system. Compared with standard 3D drawing-design process and knowledge management technology reduce the design lead time, possible mistakes in 3D mold building. The platform includes conceptual mold-design, core and cavity design, 3D drawing and the databases of standard building mold process and quick modifying in mold design change, etc.. It leads to the reduction of mold design cycle for cellular phone housing from 7 days to 3 days.

Low cost and quality are essential demands in mold and molding manufacturing. Mold cost calculations can be classified into four parts: material manufacture overhead and profit. This research develops a navigation system that can provide a calculation and analysis of mold prices. The difference between the actual sample price and the calculated price is roughly 6%. Via the mold price navigation system customer and mold vendor engaged in detailed discussions and obtain a good mold price estimate. The system not only greatly helps the inexperienced designer but also provides a feasible mold price calculation conception and a collaborative environment for the design process.

Low cost and quality are essential demands in mold and molding manufacturing. Mold cost calculations can be classified into four parts: material, manufacture, overhead, and profit. This research develops a navigation system that can provide a calculation and analysis of mold prices. The difference between the actual sample price and the calculated price is roughly 6%. Via the mold price navigation system, customer and mold vendor engaged in detailed discussions and obtain a good mold price estimate. The system not only greatly helps the inexperienced designer but also provides a feasible mold price calculation conception and a collaborative environment for the design process.

Development of electro-conductive polyamide 4.6 (PA4.6) and polyamide 4.6/poly(phenylene sulfide) blend (PA4.6/PPS) incorporating multiwall carbon nanotube (CNT) were first reported in this work. PPS/CNT was also investigated. The CNT composites exhibited electrical conductivity at remarkably low CNT content, displayed a volume electrical percolation threshold at < 0.9 wt% CNT. At only 1 wt%, all the three composites would already register
103 Ohm?úcm volume resistivity. The required surface electrical percolation to reach 107 Ohm ?ú sq-1 for the PA4.6, PPS and PA4.6/PPS blend was 1.4, 2.0 and 0.9 wt% respectively. A co-continuous morphology observed for the PA4.6/PPS blend would explain for its extremely low percolation. The melt crystallisation behavior of the polymers altered appreciably in the presence of CNT. PA4.6 crystallised at some 12 ?øC higher, from 257.5 ?øC to 269.5 ?øC. The full crystallisation half-time of PPS was reduced by nearly 2/3 from 110s to 38s, while its peak crystallising temperature was raised by some 46 ?øC from 188.5 ?øC to 235 ?øC. The small doublet melting peak of the virgin PA 4.6/PPS blend would merge into single peak in its composite that could indicate the blend compatibility was more improved in the presence of CNT. Furthermore, the PA4.6/PPS/CNT blend showed least mould shrinkage and smoothest injection moulded surface among all the composites investigated.

Three dimensional (3D) Nanoimprint Lithography (NIL) was carried out using photo-curable resin. NIL process was as follows: first, a fabricated NIL mold was coated with an anti-sticking layer. Then, a ultraviolet (UV) photo-curable resin was dispensed onto cleaned glass slides or polyethylene terephthalate (PET) films. Next, the mold was pressed against the resin on the substrate. The photo-curable resin was then exposed of UV light. The mold was then retracted, leaving behind a replica of its pattern. Using 3D mold with markedly uneven, evaluation of photo-curable resin was possible and it was found that weaker intermolecular force monomers improved transfer and release properties.

External gas-assisted injection molding (EGAIM) has been receiving attention for its improvement of surface quality. However, compared with gas-assisted injection with gas penetration into the melt core, the packing effects of EGAIM on the pressure variation within the mold cavity and the part shrinkage have not been investigated. In this study, the pressure differential between core and cavity is about 3.04 bar. In addition, the required gas packing pressure (90 bar) is much lower than that of conventional packing pressure (1000 bar) in achieving identical shrinkage. With increased gas packing pressure and gas packing time, the shrinkage can be further reduced. However, the gas delay time for shrinkage is related to the pressure inside the mold.

The potential superiority of ATSP (aromatic thermosetting copolyester) matrices compared to conventional epoxies for aerospace composites is discussed. Preparation and characterization of carbon fiber/ATSP composites are described. In this paper we demonstrate that ATSP oligomers display liquid crystalline behavior which was identified using optical microscopy with cross-polarizers. We also describe how ATSP tailored to have a liquid crystalline structure has reduced stresses at the fiber/matrix interface and better thermal fatigue resistance compared to epoxy.

The potential superiority of ATSP (aromatic thermosetting copolyester) matrices compared to conventional epoxies for aerospace composites is discussed. Preparation and characterization of carbon fiber/ATSP composites are described. In this paper, we demonstrate that ATSP oligomers display liquid crystalline behavior which was identified using optical microscopy with cross-polarizers.We also describe how ATSP tailored to have a liquid crystalline structure has reduced stresses at the fiber/matrix interface and better thermal fatigue resistance compared to epoxy.

The aim of this work was to investigate the various effects of compatibilizers on different aspects. The polypropylene based WPC, containing different compatibilizers, were produced via compounding and injection molding. Testing for tensile and impact strengths as well as for MFR and shrinkage was carried out subsequently. We found, that the presence of a compatibilizer not only enhances tensile strength (up to 80%, depending on wood and compatibilizer concentration), but also influence other properties, e.g. shrinkage and MVR are increasing with increasing compatibilizer concentration. Furthermore, with the help of a saturation model, the effects of different compatibilizer grades, exhibiting different maleic anhydride content as well as different viscosity, were evaluated to get deeper insight in the mechanisms.

In the past three decades there has been great advancement in preparing microcellular thermoplastic polymer foam. However little attention is paid to thermoplastic elastomer. In this study microcellular poly(ethylene-co-octene) (PEOc) rubber foams with a cell density of 2.9×1010 cells/cm3 and cell size of 1.9 ?m are successfully prepared by using CO2 as the physical blowing agent with a batch foaming process. Microcellular PEOc foams exhibit a well defined closed cell structure uniform cell size distribution and formation of unfoamed skin at low foaming temperatures. Their difference from thermoplastic foam is the foam shrinkage in the atmosphere due to the elasticity of polymer matrix. The effect of melt flow rates on the cell growth process is investigated by changing the foaming conditions.

In the past three decades, there has been great advancement in preparing microcellular thermoplastic polymer foam. However, little attention is paid to thermoplastic elastomer. In this study, microcellular poly(ethylene-co-octene) (PEOc) rubber foams with a cell density of 2.9??1010 cells/cm3 and cell size of 1.9 ?¬m are successfully prepared by using CO2 as the physical blowing agent with a batch foaming process. Microcellular PEOc foams exhibit a well defined closed cell structure, uniform cell size distribution, and formation of unfoamed skin at low foaming temperatures. Their difference from thermoplastic foam is the foam shrinkage in the atmosphere due to the elasticity of polymer matrix. The effect of melt flow rates on the cell growth process is investigated by changing the foaming conditions.

Nanocomposites comprising a high percentage of inorganic layers and a low percentage of organic binder have been reported to exhibit remarkable physical properties due to high levels of organization, connectivity and phase morphology. We report the preparation and characterization of a system of this type consisting of montmorillonite layers and thermoplastic polyurethane (TPU) binder. Transparent sheets were prepared and characterized via SEM for structure, TGA and DSC for thermal properties, and DMA for mechanical response. These materials are stable, robust, and exhibit interesting combinations of stiffness and damping capacity.

Delivery of a melt which is homogenous in composition and temperature is paramount for achieving high quality extruded products. However, melting stability can be difficult to determine via typical melt pressure and thermocouple instrumentation. This can result in inefficient operation through non-optimized operating conditions or extruder screw geometry. In this work, melt temperature homogeneity in a single screw extruder is investigated experimentally using a thermocouple mesh technique. The effect of barrel temperature settings and screw speed on die melt temperature homogeneity is investigated. Inferential methods of determining melting stability in-process are investigated with the aim of developing modeling and control techniques to improve process quality and efficiency.

Manufacturing of extruded polystyrene (XPS) foam insulation boards is currently based on weak ozone depleting gases. Mixtures of blowing agents are actually seen as one of the most promising solutions to ozonedepleting substances phase-out. This paper investigates various blowing agent formulations based on mixtures of hydrofluorocarbons HFC-134a (1,1,1,2-tetrafluoroethane) and HFC-32 (difluoromethane). The study focuses on the rheological (plasticization) and degassing (solubility) behaviors of the formulations, as measured on-line during foam extrusion. Rules of mixing for such blends of HFCs are proposed based on the relative contribution of each component to the overall processing behavior.

Massively invasive surgery is often the only cure for the worst cases of cartilage-related diseases. In an effort to physiologically mimic human joints, 4 biomedical thermoplastic polyurethanes (TPU) differing in glass transition temperature, modulus and wettability were foamed using a CO2-based solid-state process. Human cartilage mechanical behavior was closely matched by low density foams of the softest TPU investigated. In vitro osteoblastic studies showed improved cell differentiation, activity and proliferation; all suggestive of TPU foans potential osteointegration. The superior bioactivity and cartilage-matching mechanics make the TPU foam a promising cartilage replacement.

The mechanical properties and crystallization behaviors of PP/acrylonitrile-butadiene-styrene/organic montmorillonite nanocomposites (PP/ABS/OMMT) were studied. It was shown that compatilizer PP-g-MAH not only improved the compatibility of PP/ABS but also promoted the dispersity of OMMT particles in continuous phase PP and dispersed phase ABS. In addition PP was reinforced and toughened by both layered silicate OMMT nanoparticles and ABS. The blend weight ratio of PP/ABS/OMMT which was 85/15/2 wt % had a concerted effect on toughening. OMMT nanoparticles also increased crystallization temperature and crystallinity.