Characteristics of Thermosetting BMC Plastics

Introduction to BMC Plastics

Bulk Molding Compound (BMC) plastics are bulk molding materials that possess excellent electrical, mechanical, heat resistance, and chemical corrosion resistance properties. They are also suitable for various molding processes, allowing them to meet a wide range of performance requirements for various products. As a result, they are increasingly favored by a large number of users.

Bulk Molding Compound (BMC) is a type of thermosetting plastic that combines various inert fillers, fiber-reinforced materials, catalysts, stabilizers, and pigments to form a putty-like composite material used for compression or injection molding.

BMC is highly filled and reinforced with short fibers, with glass fiber reinforcement materials ranging from 10% to 30%, typically with lengths between 1/32 inch and 1/2 inch (12.5mm).

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Based on different end-use applications, composite materials can be precisely controlled in terms of dimensions. They exhibit excellent flame resistance, resistance to electrical tracking, high dielectric strength, corrosion resistance, stain resistance, outstanding mechanical properties, low shrinkage, and color stability.

Bulk Molding Compound (BMC) plastics have excellent flow characteristics and provide excellent insulation and flame resistance, making them highly suitable for various applications with stringent requirements for details and dimensions.

The materials are available in 75 different colors and can withstand powder coating or water-based paint.

Properties of BMC Plastics

Bulky prepreg composed of short-cut glass fibers mixed with unsaturated polyester paste. Suitable for various molding processes such as compression molding, transfer molding, and injection molding.

Products made from it exhibit excellent mechanical properties, high dimensional stability, good surface finish, resistance to water, oil, and corrosion. They are heat-resistant and have excellent electrical properties, particularly achieving an arc resistance of approximately 190 seconds.

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(1) General Properties

BMC plastics (DMC) have a relatively high specific gravity, ranging from 1.3 to 2.1. They have a glossy appearance, a pleasant tactile feel with a sense of hardness and weight. Heating them produces a significant amount of smoke and a styrene odor.

Some varieties of BMC plastics (DMC) are flame-resistant, while others are highly flammable, leaving behind inorganic residues after combustion.

(2) Dimensional Stability

The linear expansion coefficient of BMC plastics (DMC) is (1.3-3.5)×10-5K-1, which is smaller than that of most thermoplastic materials. This gives BMC plastics (DMC) very high dimensional stability and accuracy.

Temperature has minimal impact on the dimensional stability of BMC plastics (DMC), but humidity has a more significant effect. BMC plastics tend to expand when they absorb moisture.

The linear expansion coefficient of BMC plastics (DMC) is close to that of steel and aluminum, making it suitable for composite applications with these materials.

(3) Mechanical Strength

BMC plastics (DMC) exhibit higher tensile, bending, and impact strength compared to thermoplastic plastics. They also have better resistance to creep compared to thermoplastic materials.

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(4) Water and Solvent Resistance

BMC plastics (DMC) demonstrate excellent resistance to corrosion from water, ethanol, aliphatic hydrocarbons, oils, and fats.

But they are not resistant to ketones, chlorinated hydrocarbons, aromatic hydrocarbons, acids, and bases.

BMC plastics (DMC) have low water absorption, and their insulation properties remain excellent even after being immersed for a day.

(5) Heat Resistance

BMC plastics (DMC) exhibit better heat resistance than typical engineering plastics, with a heat deflection temperature (HDT) of 200-280°C. They can be used for extended periods at temperatures up to 130°C.

(6) Aging Resistance

BMC plastics (DMC) have excellent aging resistance. They can be used indoors for 15-20 years, and even after 10 years of outdoor exposure, their strength retention remains above 60%.

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(7) Electrical Properties

BMC plastics (DMC) exhibit outstanding resistance to electrical arcing, with capabilities of reaching approximately 190 seconds.

(8) Low Odor Emission

BMC plastics (DMC) utilize a styrene cross-linking agent, which leaves a residual amount of 0.1% even after curing, emitting an odor when heated.

Therefore, for food-related applications such as microwave cookware, BMC plastics (DMC) should use UP resin without residual styrene monomers.

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