BMC is a glass fiber reinforced unsaturated polyester thermosetting plastics for short, is a kind of reinforced thermosetting plastics currently use the maximum amount.
  1.The characteristics and application of BMC. Properties and mechanical properties of BMC has excellent physical properties, electrical, so its application is very extensive, such as can produce such as gearbox component, an air inlet pipe, valve cover, bumpers and other mechanical parts; also obtains the widespread application in the requirements for earthquake resistance, flame retardant, beautiful, durable aviation, building, furniture and so on; in the traditional electric field, its use has become increasingly widespread.
  2.in the BMC due to the addition of glass fiber, so the used some different equipment and usually thermosetting plastic injection molding equipment, injection molding machine, piston and screw type can be. Feeding system, whether the screw or plunger type, must be attached to an extrusion type feeding device, in order to force the material into the barrel, plunger type pressure feed by the feeding device; injection system, the injection plunger type injection molding machine accuracy and constant, so that the glass fiber and less damage to disperse in the melt, therefore, plunger type injection molding machine is widely used, but the exhaust inconvenience. The heating system in injection molding, BMC, control of barrel temperature is very important, must have a set of control system to control the temperature, to ensure that the feeding section to the nozzle temperature is the best. At present the water of constant temperature or constant temperature oil heating. Also can use electric heating. Mold clamping device. To use multiple mechanical, hydraulic and hydraulic clamping device etc.. Die. BMC injection mold and usually thermoplastic, thermosetting plastic is somewhat different, mainly BMC shrinkage rate is low, therefore should be in the cavity size design changes.
  3.Injection molding process of BMC. Barrel temperature and die temperature. When processing, the requirement for BMC in barrel temperature, keep the flow dynamic low viscosity for longer time, generally the barrel temperature should be able to meet the low limit of BMC. Barrel temperature is generally divided into two or three sections of the control, in the end the lower hopper, high temperature near the nozzle end. The general difference 20-60, mold temperature control in general 135-185 degree. Injection pressure. Because of the mobility of BMC, fast curing, mould structure is complex, the injection pressure is easy to choose a high pressure, typically 80-160MPa. Injection speed. Injection speed, help to improve the surface quality of plastic parts, shorten curing time, but is not conducive to the exhaust, and increase the degree of orientation of glass fiber. It should be the premise and surface quality of plastic parts in the guarantee under the injection speed is lower, usually 1.8-3.5m/min. Screw speed and back pressure. If the screw injection molding machine, the injection of BMC, screw on the glass fiber damage is larger, in order to minimize fiber damage, screw speed and easily selected low value, usually 20-50r/min. According to the BMC viscosity, with low back pressure is appropriate, generally 1.4-2.0MPa. The molding cycle. Because the plastic parts of the size and complexity of each different, the process time is different, the general injection time is 2-20s, the holding time is 10-20s/mm.