摘要:

AbstractGas‐assisted injection molding is an innovative process that can provide tremendous flexibility in design and manufacturing of plastics parts once it is fully understood and matured. The research effort presented in this article is aimed at development of Computer‐Aided Engineering (CAE) technology for gas‐assisted injection molding. To achieve the goal, efforts have been made in developing a numerical analysis for predicting the filling and post‐filling behavior and verifying the predictions through collaboration with the industry and universities. This article firstly describes the physics of this process, which leads to the various advantages and the inherent difficulties associated with the design and processing. Secondly, it discusses the methodology of numerically modeling and simulating gas‐assisted injection molding filling dynamics together with experimental comparison. At the end of this article, it presents the various advantages of applying the CAE technology for the gas‐assisted injection molding process, such as evaluating the various gas‐assisted injection molding processes and establishing preliminary design guidelines. © 1995 John W

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe quality of thermoplastic injection molded parts is mainly determined during the post‐filling process. To enhance the control capacity over the post‐filling process, adding compression to the conventional injection molding process opens a flexible channel for pressure control. This study experimentally investigated the effects of adding compression on the thermal‐mechanical history and on the quality of molded parts. An instrumented molding machine with a compression mechanism was used. Molds for rectangular plate and circular disk were equipped with a movable cavity wall and shut‐off mechanism. The thermomechanical history during the injection compression molding was identified with the aid of a PC‐based data acquisition system. The quality of parts was evaluated by flatness, deviation from mold dimensions, and birefringence. It has been found that the thermomechanical history of the melt under injection compression molding follows a quadrilateral‐shaped path over the p‐v‐T diagram. The control capacity over post‐filling is enhanced. It thus can produce parts with better dimensional control with less frozen‐in orientation than those from conventional injection molding. © 1995

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractFiber reinforced thermoplastics (FRTP) injection molded articles have many advantages. However, moldings with a complex geometry often encounter weldline problems. Mechanical properties of the injection moldings are often reduced by weldlines, because the fibers at weldline regions orient perpendicularly to the flow directions. We have reported that weldline strength is improved by “back‐flow” during the holding stage. In this article, we have attempted to adapt the SCI (Simultaneous Composite Injection) molding method to improve weld strength of FRTP injection moldings. The back‐flow is expected to occur when there is a difference of holding pressure between two cylinders of the SCI molding machine. The effect of pressure difference between two injection cylinders on the back‐flow phenomena is discussed for fiber reinforced polycarbonate. It is clear that the strength reduction by the weldline can be suppressed down to negligibly small levels in SCI molding. © 1995 John Wiley

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects of compatibilizing agents on the morphology and properties of high density polyethylene (HDPE) and polyamide‐6 blends were investigated. The ternary blends were studied with the objective of understanding and optimizing the compatibilization of HDPE and polyamide‐6. The blends were prepared by melt mixing the individual components in a twin‐screw extruder. Mechanical property, rheological property, differential scanning calorimetry, and scanning electron microscopy results are discussed. The addition of compatibilizing agents results in a greatly reduced dispersed phase particle size. The properties of the blends level out after a compatibilizer level of 3 wt% has been reached. The rheological, mechanical, and thermal property results indicate the presence of the compatibilizing agent along the interfacial boundary regions between the other two phases. © 1995 John Wiley&Son

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractPolymer blends containing nylon‐6 of different molecular weights (MW) and polypropylene (PP) were prepared by using a twin screw extruder in order to examine the effects of molecular weights of nylon and the influences of different types of compatibilizing agents on the phase morphology and the properties. The morphology of the resulting blends was characterized by using both scanning electron microscope (SEM) and optical microscope and the properties measured included Izod impact strength, melt flow index (MI), flexural modulus, and heat distortion temperature (HDT). It was found that the molecular weights of the nylon matrix had a significant effect on the phase morphology. The fracture surface of the low MW nylon blend demonstrated a uniformed phase morphology with the dispersed PP particles of dimensions in the range of 1 μm in diameter embedded in the nylon matrix, suggesting an improved compatibility as compared with the high MW nylon system, even though these two constituents were incompatible in nature. Three different types of compatibilizers, including maleic anhydride modified PP (MA‐g‐PP), acrylic acid modified PP (AA‐g‐PP), and ethylene glycidyl methacrylate copolymer (EGMA), were used to examine their effects. It seemed that blends compatibilized with MA‐g‐PP exhibited the most homogeneous phase morphology and superior mechanical properties among the three. In the blends containing low MW nylon as the matrix phase, the Izod impact strength was shown to have increased by about 40% as compared with the noncompatibilized blend, while a 20% increase of the impact strength was measured in the high MW nylon system. The effects of nylon's molecular weights and the compatibilizers were also studied in systems of PP/nylon blends reinforced with silane‐treated glass fibers. It was shown that the properties of the composites relied on the phase morphology which, in turn, was affected by both the molecular weight of nylon and the compatibilizing agents. © 1995 Joh

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of Ethylene Methyl Acrylate (EMA) copolymer as a reactive polymeric compatibilizer in a blend of 50:50 Thermoplastic Polyurethane (TPU)‐Polydimethylsiloxane (PDMS) rubber has been studied. The compatibility was proved by mechanical property measurements and phase morphology studies. EMA reacted with PDMS rubber at 180°C at 100 rpm rotor speed during melt mixing to produce EMA‐g‐PDMS rubber in situ, which acted as the compatibilizer for the binary system of TPU and PDMS rubber. EMA‐g‐PDMS rubber is believed to undergo specific interaction via hydrogen bonding with the TPU matrix through the CO group of EMA and the unassociated NH group of TPU, whereas the PDMS rubber in the EMA‐g‐PDMS disperses well with the bulk PDMS matrix. The phase morphology studies showed a drastic reduction in the size of the dispersed phase at the optimum concentration of EMA. © 1995

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTypes and amounts of volatiles emitted during thermoplastics processing depend upon the chemical structure of the material and the choice of processing conditions. The identification of volatiles and the development of analytical techniques for measuring their concentration in the workplace are of paramount importance to establish or revise threshold limit values that would minimize exposure to hazardous chemical substances and lead to corrective action. In this review, information related to the types of volatiles emanating from injection molding machines and extruders as well as analytical methods for their measurement was collected, analyzed, and tabulated. Emphasis was placed on the four major commodity plastics, viz., polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), and polystyrene (PS). Although the main emphasis is on emissions during processing, related literature under simulated conditions is also mentioned. © 1995 John Wiley&Sons, Inc

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0730-6679    

DOI:10.1002/adv.1995.060140108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY