Effects of Heating and Cooling of Injection Mold Cavity Surface and Melt Flow Control on Properties of Carbon Fiber Reinforced Semi-Aromatic Polyamide Molded Products

Abstract

Fiber reinforced thermoplastics (FRTP), reinforced with glass or carbon fibers, are used to improve the mechanical strength of injection-molded products. However, FRTP has problems such as the formation of weld lines, the deterioration of appearance due to the exposure of fibers on the molded product surface, and the deterioration of the strength of molded products due to the fiber orientation in the molded products. We have designed and fabricated an injection mold capable of melt flow control and induction heating and cooling. This mold can both heat and cool the injection mold. It can also control the melt flow direction using a movable core pin. In this study, the above-mentioned mold was used for the molding of carbon fiber reinforced semi-aromatic polyamide. As a result, we found that increasing the heating temperature of the mold and increasing melt flow control volume contribute to the prevention of the generation of a weld line and the exposure of fibers on the molded product surface, as well as to the formation of a flat surface and increased bending strength. The relationships of these results with the carbon fiber orientation in the molded products and the crystallization of semi-aromatic polyamide were also examined in this study.

Fabrication of continuous carbon fiber reinforced polypropylene composites by injection compression molding with self‐resistance electric heating

“…[9,10] In order to fabricate short fiber reinforced thermoplastics (SFRT), injection molding process has usually been utilized, with the advantage of low cost and rapid fabrication of complex structural parts. [11][12][13][14] However, the mechanical properties of SFRT are inferior. Continuous carbon fiber reinforced thermoplastics (cCFRTs) possess the good mechanical properties and are often prepared by hot pressing process, while the designability of this molding method is poor.…”

The Feasibility of an Internal Gas-Assisted Heating Method for Improving the Melt Filling Ability of Polyamide 6 Thermoplastic Composites in a Thin Wall Injection Molding Process

“…Most applications of thin wall injection molding are in the field of optical products (such as CDs and DVDs) and micro channel devices. In the field of optics production, the injection molding method also has advantages in the production of waveguides, optical gratings, and optical switches [8][9][10], as well as many products involving micro channel devices, such as capillary analysis systems, micro pumps, and lab-on-a-chip applications [11,12].…”

“…To achieve a molding process with a high cavity surface and reduce the frozen layer, many methods of mold temperature control have been investigated in recent years [8]. The initial method used to obtain a high mold temperature was to increase the temperature of cooling water as high as 90 or 100 • C [12][13][14]. When targeting temperatures are higher than 100 • C, heaters are inserted into the mold plate.…”

Improving the Melt Flow Length of Acrylonitrile Butadiene Styrene in Thin-Wall Injection Molding by External Induction Heating with the Assistance of a Rotation Device

“…However, to increase the melt flow length by this method, a higher material cost is incurred; on the other hand, in some cases, the molding material is fitted by the customer. In order to reduce the frozen layer, the use of a high mold temperature has yielded good results in reducing the filling pressure and clearly improving the melt flow length [ 11 , 12 , 13 ]. According to research on mold temperature control [ 14 , 15 , 16 , 17 , 18 ], this is a crucial aspect of plastic manufacturing in the field of injection molding.…”