SMC formulation

Nowadays, many SMC suppliers are trying to make low-density material. This SMC formulation will be allowed you to get the ability to design with a low specific gravity material without mechanical properties, surface qualities, etc.

Traditional SMC materials used in Class A applications have a density of 1.8 g/cm2 to 1.9 g/cm2 — around 30% less than aluminum and 75% less than steel, but relatively high for plastic material. Because SMC parts must be thicker than steel or aluminum, actual weight savings are smaller than these figures would indicate. The classic method for reducing density in SMC is to add hollow glass microspheres, and formulations are in production for unexposed, lightly loaded components with densities as low as 1.3 g/cm2.

What are the common types of SMC formulations?

1. Basic formulations.
2. Formulation according to production process and product performance.
3. Formulation specially for a particular product.

Depending on the range of products, requirements and the specific conditions of each unit, the components and dosage ratios in the table can be changed in different ways.

SMC Formulation

Recipe	General/Serving	Corrosion Resistant/Part	Low shrinkage portion
Polyester resin	Phthalate 100	Isophthalic Acid 100	Phthalate 100
Initiator	Tt-Butyl Benzoyl Peroxide 1	/	/
Low shrinkage additives	Thermoplastic Polymers 0 – 10	Thermoplastic Polymer 25 – 40	/
filler	Calcium Carbonate 70 – 120	Barium Sulfate 60 – 80	Calcium Carbonate 120 – 180
Internal release agent	Zinc stearate 1~2	Zinc stearate 1~2	Zinc stearate 3~4
Thickeners	MgO or Mg(OH)2, Ca(OH)2, 1-2	MgO or Mg(OH)2,Ca(OH)2,0.5-1	MgO or Mg(OH)2, Ca(OH)2, 1-2
Stabilizer	Appropriate amount	Appropriate amount	Appropriate amount
Fiberglass	25% ~ 35%	/	/

How to choose unsaturated polyester resin for smc?

The selection of unsaturated polyester should meet the following requirements:

1. Low viscosity or solid powder, convenient for glass fiber impregnation or mixing.
2. Easy to react with thickener to meet thickening requirements.
3. It can cure quickly and improve production efficiency.
4. It has high thermal rigidity to ensure that the part will not be damaged when it is demolded.
5. It has sufficient toughness and does not crack when the workpiece is deformed.

MDC Mould, as a leading SMC mold maker in china, has developed such compression mold using low density SMC material, and finally testing was successful. Due to this, MDC Mould has been officially qualified by OEMS such as Daimler and Audi.