附录附录1An experimental study of the water-assisted injection molding ofglass fiber filled poly-butylene-terephthalate (PBT) compositesAbstract：The purpose 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 used. 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 these parts. X-ray diffraction (XRD) was also used 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 were 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 those 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.Keywords: Water assisted injection molding; Glass fiber reinforced poly-butylene-terephthalate (PBT) composites; Processing parameters; B. Mechanical properties; Crystallinity; A. Polymer matrix composites;1. IntroductionWater-assisted injection molding technology 1 has proved itself 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 sections 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 24. 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, because 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 ease of recycling the water makes it an ideal medium for the process. Since water does not dissolve and diffuse 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. These plastics include thermoplastic and thermoset polymers. In general, thermoplastic polymers have an advantage over thermoset polymers in popular materials in structural applications.Poly-butylene-terephthalate (PBT) is one of the most frequently used 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 u