SMC | Sheet Moulding Compound
SMC (Sheet Moulding Compound) is used in hot press compression moulding for the production of large parts with high mechanical properties and excellent surface finish.
SMC is a polymeric composite material, which consists primarily of a thermosetting resin, mineral fillers and glass fibre reinforcement. The resin used is generally unsaturated polyester (UP) or vinyl-ester (VE). Additional ingredients such as thermoplastic components, catalysts, inhibitors, mould release agents, thickeners and colour pigments are used to enhance the performance and moulding process of the final product.
Our Verkid® SMC products come as a sheet 1500 mm wide supplied either on ≈450 kg rolls, on ≈1400 kg MegaRolls, or folded like computer paper in ≈1150 kg boxes.
The transformation or moulding process is carried out in a hot mould at temperatures between 130 – 160ºC and under pressure (typically 30 – 120 bar), in vertical presses specially designed for this process.
SMC applications are wide-ranging in the Automotive & Transportation, Electrical & Energy, Building & Construction, Industrial, Service, Sanitary, Domestic and Medical markets.
What is SMC?
SMC (Sheet Moulding Compound) is a glass fibre reinforced compound, in a thermoset resin matrix, with mineral fillers and different additives. Generally thermoset unsaturated polyester or vynil-ester resins are used as organic matrix.
With the aim of enhancing its characteristics and improve its transformation, other components are added: catalysts, inhibitors, thermoplastic additives, demoulding agents, thickeners and pigments.
SMC MANUFACTURING PROCESS
Resins, fillers and additives are automatically weighted and mixed together. The colour pigments and thickeners are measured and mixed continuously with the mother paste in a computer-controlled process forming the impregnation paste. The impregnation paste is immediately transferred to the glass fibre impregnation line.
The impregnation paste is transferred to a doctor box where it is deposited onto a moving carrier film. Simultaneously the glass fibre is chopped to a pre-determined length and dropped onto the layer of paste. A second film is coated with a layer of paste and then used to cover the fibre cuttings creating a “sandwich”.
The resulting sheet is then sent through a series of compaction rollers to ensure a perfect impregnation or wet out of the chopped fibre. At the end of the impregnation line, the sheet can be rolled up using rolls, MegaRolls or folded into boxes.
MATURATION AND CONSERVATION
SMC must mature before it reaches optimal conditions for moulding. The resin paste changes from a liquid state during manufacturing to a semi-solid state at its optimal condition period. This change in viscosity is achieved through the introduction of the thickening agent during manufacturing. Typically the required maturation time is between 2 and 4 days, depending on the specific formulation.
Even after the material has matured, it continues to thicken at a speed dependant on the storage temperature. Therefore there is an optimal utilisation period of typically, between 1 and 6 months, dependant mainly on the specific formulation and storage temperature, which is recommended to be between 5ºC and 25ºC. Higher storage temperatures can significantly reduce the usability time of SMC.
SMC is mainly used in hot press compression moulding for the production of large and relatively flat parts. Although moulding activities are carried out by our customers, Astar assists during moulding trials and offers complete technical assistance everytime is required.
SMC Product Overview
Our Verkid® SMC products are adaptable to your needs. All our formulations are designed according to your specific requirements.
|Abrasion||✓||✓||Formulations with enhanced abrasion resistance|
|Acoustic||✓||✓||✓||Applications requiring better acoustic damping properties|
|Antibacterial||✓||Formulations that prevent the growth of new bacteria and eliminate existing bacteria|
|Antistatic||✓||Conductive materials with antistatic properties for explosion proof parts|
|Arc Resistance||✓||Applications requiring arc resistance|
|Carbon Fiber||✓||Materials with chopped carbon fibers for light weight structural parts with high mechanical properties|
|Chemical||✓||✓||✓||✓||Formulations with an increased resistance to most chemical agents|
|Class A||✓||Excellent surface quality for painted body panels|
|Dielectric||✓||Materials with specific dielectrical properties|
|Finish||✓||✓||Special appearance effects: granite, marble, stone, etc.|
|Flame Resistant||✓||✓||Formulations designed to meet your required flame retardancy. UL “Yellow Cards” available.|
|Flow||✓||✓||✓||✓||Better flow properties during the moulding process to fill intricate parts|
|Food Contact||✓||✓||Food contact applications|
|High Temperature||✓||✓||✓||✓||High temperature stability for applications requiring high service temperature|
|Hydrophobe||✓||✓||Applications requiring an increased resistance to water absorption|
|Low Density||✓||Low density formulations to reduce weight of parts|
|Low Emission||✓||Formulations with low emission of volatile organic components|
|Low Shrink||✓||✓||✓||✓||Parts requiring precise tolerances for mounting of various components|
|Low Profile||✓||Parts requiring very precise tolerances for mounting of various components|
|Low Pressure||✓||✓||✓||Applications requiring moulding at low press tonnage|
|Low Smoke Emission||✓||✓||✓||Formulations designed to meet low smoke emission requirements|
|Paintable||✓||✓||✓||✓||Materials adapted to all painting processes|
|PIMC||✓||✓||Materials adapted to Powder In-Mould Coating process|
|Reactive||✓||✓||✓||✓||High reactivity formulations to reduce curing time|
|Scratch Resistance||✓||✓||Formulations with an enhanced scratch resistance|
|Strength||✓||✓||✓||✓||Applications requiring high mechanical performance|
|Surface||✓||✓||✓||✓||Applications requiring excellent surface quality|
|Unidirectional||✓||✓||✓||✓||High strength materials with unidirectional reinforcement to strengthen especially the fibre direction|
|UV stable||✓||✓||✓||✓||Formulations with an enhanced UV resistance|
|Other||✓||✓||✓||✓||Tell us your required key properties and we will design the specific formulation to meet them|