Introduction to SMC Molding & BMC Molding Materials

Applications of SMC Molding & BMC Molding in Various Industries:

• Electrical: Insulators, switch boxes, electrical equipment enclosures, insulated tools, terminal boards, etc.
• Automotive: Headlamp covers, front and rear bumpers, battery trays, engine soundproofing panels, etc.
• Railway: Vehicle window frames, bathroom components, seats, coffee table tops, carriage sidewalls, and ceilings, etc.
• Construction: Water tanks, bath products, door panels, purification tanks, construction templates, etc.
• Bathroom: Bathtubs, integrated bathroom fixtures, integral molded sinks, etc.
• And various other industrial and agricultural fields.

SMC Molding Raw Materials:

SMC materials are composed of GF (special yarn), UP (unsaturated resin), low shrinkage additives, MD (fillers), and various additives.

1. Unsaturated Polyester Resin

   • Reacts easily with thickening agents to meet thickening requirements (mainly for SMC).
   • Cures rapidly, improving production efficiency.
   • Has high heat strength, ensuring that the molded products are not damaged during demolding.
   • Provides sufficient toughness to prevent cracking when the component undergoes certain deformations.

2. SMC Tooling

   • Safe for storage and operation.
   • Does not decompose at room temperature.
   • SMC produced with initiators has a long storage life and rapidly decomposes and cross-links at elevated temperatures.
   • Cost-effective.

3. Anti-agglomerants

   Prevent unsaturated polyester resin from crosslinking polymerization at room temperature, extending the storage life.

4. Thickening Agents

   SMC requires high viscosity during compression molding, storage, and transportation. Thickening agents are used to achieve this.

   Selection Criteria:

   1. Low viscosity is required during preparation to ensure thorough impregnation of resin into glass fibers and fillers.
   2. After impregnation, viscosity should increase rapidly to adapt to storage, transportation, and molding operations.
   3. Thickened blanks should quickly fill the mold cavity at molding temperatures and prevent resin-fiber separation.
   4. Viscosity after thickening should remain stable within the moldable range during the storage period.
   5. Thickening effect should be reproducible consistently during production.

5. Low Shrinkage Additives

   General polyester resins have a curing shrinkage rate of 7% to 10%. Adding low shrinkage additives can significantly reduce the shrinkage rate, making it close to zero. It also ensures smooth, ripple-free surfaces of SMC products.