BMC Parts Stability Has Little Impact

BMC Parts material is the abbreviation of Bulkmolding compounds, that is, group molding compound. Domestic often known as unsaturated polyester molding compound. The main raw material from the GF (chopped glass fiber), UP (unsaturated resin), MD (filler) and a variety of additives by the full mixing of the mass-like prepreg. BMC Parts pellet molding compound has excellent electrical properties, mechanical properties, heat resistance, chemical resistance. It is suitable for molding by molding, transfer molding, injection molding and so on. The obtained products have good mechanical properties, high dimensional stability, good surface finish, water resistance, oil resistance, excellent corrosion resistance and good heat resistance and electrical properties. Arc resistance can reach about 190s. Mainly used in electrical appliances, motors, radio, instrumentation, machinery manufacturing, chemical equipment, construction, transportation, defense and other departments.

1, the general performance: BMC Parts larger proportion, between 1.3 to 2.1; product appearance bright, feel good, there is a hard and heavy feeling; with the fire will produce a lot of fumes, and styrene smell; some varieties of BMC Parts flame retardant, but some varieties and easy to burn, burning after leaving inorganic substances.

⒉ dimensional stability: BMC Parts linear expansion coefficient is (1.3 ~ 3.5) × 10-5K-1, smaller than the average thermoplastic, which makes the BMC Parts has a high dimensional stability and dimensional accuracy. The effect of temperature on the dimensional stability of BMC Parts is very small, but the effect of humidity is more serious, BMC Parts will expand after moisture absorption. BMC Parts linear expansion coefficient and steel, aluminum is very close, so it can be combined with.

⒊ mechanical strength: BMC Parts tensile, bending, impact strength and other properties higher than the thermoplastic, creep resistance than thermoplastic.

⒋ water and solvent: BMC Parts on water, ethanol, aliphatic hydrocarbons, grease, oil has good corrosion resistance, but not resistant to ketones, chlorinated hydrocarbons, aromatic hydrocarbons, acid and so on. BMC Parts (DMC) water absorption is low, soaking insulation after a day is still very good.

⒌ heat resistance: BMC Parts heat resistance than the general engineering plastics are good, heat distortion temperature HDT 200 ~ 280 ℃, long-term use at 130 ℃ temperature.

⒍ Aging resistance: BMC Parts anti-aging performance is very good, available in the room 15 to 20 years, outdoor exposure 10 years after its strength retention rate of 60% or more.

⒎ electrical performance: BMC Parts arc resistance of the most prominent, can reach about 190 seconds.

BMC Parts features and applications

BMC Parts has good physical properties, electrical properties and mechanical properties, so it is widely used, such as the production of such as transmission components, intake pipe, valve cover, bumper and other mechanical parts; in the requirements of seismic, Durable air, construction, furniture and other aspects have also been widely used; in its traditional areas of electrical appliances, its use is also more and more widely.

1) feeding system

In the case of screw or plunger, a squeeze-type charging device must be added to force the material into the cartridge, which uses a plunger-type feed.

2) Injection molding system

As the plunger injection molding machine injection volume is accurate and constant, so that the glass fiber less damage dispersed in the melt, so the plunger injection molding machine use more, but the exhaust inconvenience.

3) heating system

In the BMC Parts injection molding, the control cylinder temperature is very important, there must be a set of control system to control the temperature, to ensure that the feeding section to the nozzle temperature is the best. At present, more use of constant temperature water or constant temperature oil for heating. Electric heating can also be used.

4) clamping device

More use of mechanical, hydraulic and full hydraulic type of several mold clamping device.

5) mold

BMC Parts injection mold and the usual thermoplastic, thermosetting injection is somewhat different, mainly BMC Parts shrinkage is low, so the design of the mold cavity size should be changed.

BMC Parts injection molding process

1) cylinder temperature and mold temperature

Injection molding process, requires BMC Parts at the cylinder temperature, a long time to maintain a low viscosity flow; general cylinder temperature should be able to meet the BMC Parts low limit. Cylinder temperature is generally divided into two or three control, near the hopper end is low, near the nozzle temperature is higher. Generally difference between 20-60C, mold temperature is generally controlled at 135 ~ 185C ;.

2) injection pressure

As the BMC Parts's poor mobility, fast curing, mold structure is complex, so the injection pressure should choose a higher pressure, generally 80 ~ 16OMPao

3) Injection speed

The increase of injection speed will help to improve the surface quality of plastic parts, shorten the curing time, but not conducive to exhaust, and increase the degree of glass fiber orientation. - should be in the quality of plastic parts to ensure the premise of the use of lower injection speed, usually 1.8-3.5m / min.

4) screw speed and back pressure

If the use of screw-type injection molding machine, injection of BMC Parts, the screw on the glass fiber damage, in order to minimize the damage of glass, screw speed should choose low value, usually 20 ~ 5Or / min. According to the BMC Parts viscosity, to use low back pressure is appropriate, generally 1.4-2.0MPa.