复合材料注塑成型中英文对照外文翻译文献(文档含英文原文和中文翻译)
An experimental study of the water-assisted injection molding ofglass fiber filled poly-butylene-terephthalate
(PBT) composites
Abstract：The purpo of this report was to experimentally study the water-assisted injection molding process of poly-butylene-terephthalate(PBT) composites. Experiments were carried out on an 80-ton injection-molding machine equipped with a lab scale water injection system,which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator,and a control circuit. The materials included virgin PBT and a 15% glass fiber filled PBT composite, and a plate cavity with a rib across center was ud. Various processing variables were examined in terms of their influence on the length of water penetration in molded parts, and mechanical property tests were performed on the parts. X-ray diffraction (XRD) was also ud to identify the material and
structural parameters. Finally, a comparison was made between water-assisted and gas-assisted injection molded parts. It was found that the melt fill pressure, melt temperature, and short shot size we
re the dominant parameters affecting water penetration behavior.Material at the mold-side exhibited a higher degree of crystallinity than that at the water-side. Parts molded by gas also showed a higher degree of crystallinity than tho molded by water. Furthermore, the glass fibers near the surface of molded parts were found to be oriented mostly in the flow direction, but oriented substantially more perpendicular to the flow direction with increasing distance from the skin surface.
菜花炒鸡蛋Keywords: Water assisted injection molding; Glass fiber reinforced poly-butylene-terephthalate (PBT) composites; Processing parameters; B. Mechanical properties; Crystallinity; A. Polymer matrix composites;
水之美1. Introduction
Water-assisted injection molding technology [1] has proved itlf a breakthrough in the manufacture of plastic parts due to its light weight, faster cycle time, and relatively lower resin cost per part. In the water-assisted injection molding process, the mold cavity is partially filled with the polymer melt followed by the injection of water into the core of the polymer melt. A schematic diagram of the water-assisted injection molding process is illustrated in Fig. 1.Water-assisted injection molding can produce parts incorporating both thick and thin ctions with less shrink-age and warpage and with a
better surface finish, but with a shorter cycle time. The water-assisted injection molding process can also enable greater freedom of design, material savings, weight reduction, and cost savings in terms of tooling and press capacity requirements [2–4]. Typical applications include rods and tubes, and large sheet-like structural parts with a built-in water channel network. On the other hand, despite the advantages associated with the process,the molding window and process control are more critical and difficult since additional processing parameters are involved. Water may also corrode the steel mold, and some materials including thermoplastic composites are difficult to mold successfully. The removal of water after molding is also a challenge for this novel technology. Table 1 lists the advantages and limitations of water-assisted injection molding technology.
Fig. 1. Schematic diagram of water-assisted injection molding process.
Water assisted injection molding has advantages over its better known competitor process, gas assisted injection molding [5], becau it incorporates a shorter cycle time to successfully mold a part due to the higher cooling capacity of water during the molding process. The incompressibility,
low cost, and ea of recycling the water makes it an ideal medium for the process. Since water does not dissolve and diffu into the polymer melts during the molding process, the internal foaming phenomenon [6] that usually occurs in gas-assisted injection molded parts can be eliminated.In addition, water assisted injection molding provides a better capability of molding larger parts with a small residual wall thickness. Table 2 lists a comparison of water and gas assisted injection molding.With increasing demands for materials with improved performance, which may be characterized by the criteria of lower weight, higher strength, and a faster and cheaper production cycle time, the engineering of plastics is a process that cannot be ignored. The plastics include thermoplastic and thermot polymers. In general, thermoplastic polymers have an advantage over thermot polymers in popular materials in structural applications.Poly-butylene-terephthalate (PBT) is one of the most frequently ud engineering thermoplastic materials, whichis formed by polymerizing 1.4 butylene glycol and DMT together. Fiber-reinforced composite materials have been
adapted to improve the mechanical properties of neat plastic materials. Today, short glass fiber reinforced PBT is widely ud in electronic, communication and automobile applications. Therefore, the investigation of the processing of fiber-reinforced PBT is becoming increasingly important[7–10].This report was made to experimentally study the waterassisted injection molding process of poly-butylene-terephthalate (PBT) materials. Experiments were carried out on an 80-ton injection-molding machine equipped with a lab scale water injection system, which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit. The materials included a virgin PBT and a 15% glass fiber filled PBT composite, and a plate cavity with a rib across center was ud. Various processing variables were examined in terms of their influence on the length of water penetration in molded parts, which included melt temperature, mold temperature, melt filling speed, short-shot size, water pressure, water temperature,water hold and water injection delay time. Mechanical property tests were also performed on the molded parts,and XRD was ud to identify the material and structural parameters. Finally, a comparison was made betweenwater-assisted and gas-assisted injection molded parts.
Table 1
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2. Experimental procedure
2.1. Materials
The materials ud included a virgin PBT (Grade 1111FB, Nan-Ya Plastic, Taiwan) and a 15% glass fiber filled PBT composite (Grade 1210G3, Nan-Ya Plastic, Taiwan).Table 3 lists the characteristics of the composite materials.
2.2. Water injection unit
A lab scale water injection unit, which included a water pump, a pressure accumulator, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit, was ud for all experiments [3]. An orifice-type water injection pin with two orifices (0.3 mm in diameter) on the sides was ud to mold the parts. During the experiments, the control circuit of the water injection unit received a signal from the molding machine and controlled the time and pressure of the injected water. Before injection into the mold cavity, the water was stored in a tank with a temperature regulator for 30 min to sustain an isothermal water temperature.
2.3. Molding machine and molds
Water-assisted injection molding experiments were conducted on an 80-ton conventional injection-molding machine with a highest injection rate of 109 cm3/s. A plate cavity with a trapezoidal water channel across the center was ud in this study. Fig. 2 shows the dimensions of
the cavity. The temperature of the mold was regulated by a water-circulating mold temperature control unit. Various processing variables were examined in terms of their influence on the length of water penetration in water channels of molded parts: melt temperature, mold temperature, melt
fill pressure, water temperature and pressure, water injection delay time and hold time, and short sh
ot size of the polymer melt. Table 4 lists the processing variables as well as the values ud in the experiments.
2.4. Gas injection unit
In order to make a comparison of water and gas-assisted injection molded parts, a commercially available gas injection unit (Gas Injection PPC-1000) was ud for the gas assisted injection molding experiments. Details of the gas injection unit tup can be found in the Refs. [11–15].The processing conditions ud for gas-assisted injection molding were the same as that of water-assisted injection molding (terms in bold in Table 4), with the exception of gas temperature which was t at 25 C.
2.5. XRD
什么而立In order to analyze the crystal structure within the water-assisted injection-molded parts, wide-angle X-ray diffraction (XRD) with 2D detector analys in transmission mode were performed with Cu Ka radiation at 40 kV and 40 mA. More specifically, the measurements were performed on the mold-side and
water-side layers of the water-assisted injection-molded parts, with the 2h angle ranging from 7 to 4
0 . The samples required for the analys were taken from the center portion of the molded parts. To obtain the desired thickness for the XRD samples, the excess was removed by polishing the
Table 3
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samples on a rotating wheel on a rotating wheel, first with wet silicon carbide papers, then with 300-grade silicon carbide paper, followed by 600- and 1200-grade paper for
唱念
a better surface smoothness.
春节期间适合去哪旅游2.6. Mechanical properties
Tensile strength and bending strength were measured on a tensile tester. Tensile tests were performed on specimens obtained from the water-assisted injection molded parts (e Fig. 3) to evaluate the effect of water temperature on the tensile properties. The dimensions of specimens for
the experiments were 30 mm · 10 mm · 1 mm. Tensile tests were performed in a LLOYD tensiometer according to the ASTM D638M test. A 2.5 kN load cell was ud and the crosshead speed was 50 mm/min.
Bending tests were also performed at room temperature on water-assisted injection molded parts. The bending specimens were obtained with a die cutter from parts (Fig. 3) subjected to various water temperatures.The dimensions of the specimens were 20 mm · 10 mm · 1 mm. Bending tests were performed in a micro tensile tester according to the ASTM D256 test. A 200 N load cell was ud and the crosshead speed was 50 mm/min.
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2.7. Microscopic obrvation
The fiber orientation in molded specimens was obrved under a scanning electron microscope (Jeo
l Model 5410).Specimens for obrvation were cut from parts molded by water-assisted injection molding across the thickness (Fig. 3). They were obrved on the cross-ction perpendicular to the flow direction. All specimen surfaces were gold sputtered before obrvation.
3. Results and discussion
All experiments were conducted on an 80-ton conventional injection-molding
