| |
SMC
(Sheet Moulding Compound)
|
BMC
(Bulk Moulding Compound)
|
| Form |
SMC paste, typically made from Polyester or vinylester
resins and combined with 1 inch chopped glass and is compounded
into a plastic sheet between two protective nylon films. |
BMC, also known as dough moulding compound is
typically made from polyester or vinylester resins and Phenolic
is formed into a moist mass or extruded and wrapped in nylon
film. |
| Reinforcement |
Chopped-strand glass fibres, average length 13mm
to 50mm (1/2” to 2"). Reinforcing normally represents
10 to 65 percent by weight. |
Chopped-strand glass fibres, length 6mm to 12mm
(1/4” to 1/2"). Reinforcing normally represents 5
to 25 percent by weight. |
| Moulding (view
our Troubleshooting SMC Molding Problems guide) |
Preferably compression moulding, but also transfer
and injection, with mould temperature as low as 93°C (200°F)
and pressure as low as 200 psi. |
Compression, transfer or injection moulding with
mould temperature of 150°C (300°F) and pressure between
25 and 100 kg/cm2 (300 and 1420 psi). Extremely fast moulding
cycles are possible with injection moulding sometimes up to 10
seconds per millimetre of thickness in the moulded piece. |
| Shrinkage, appearance, size, stability |
Shrinkage varies from 0.2 percent down to zero
or negative expansion values. Lower shrinkage types produce better
surfaces. Class A automotive components can be moulded with the
SMCs of the 30 and 31 series, with shrinkage close to zero. Low
shrinkage ensures size stability and close tolerances on dimensions.
During compression moulding, the SMC parts can be coated with
primer material (in mould coating. Available in 24” (61cm)
and 40” (101cm) widths. 12 to 32 oz per sf (3660 g/m2 to
9760 g/m2 |
Shrinkage varies from 0.2 percent down to zero
or negative expansion values. Lower shrinkage types produce better
surfaces. Class A automotive components can be moulded with BMC
of the 3000 series, with shrinkage close to zero. Low shrinkage
ensures dimensional stability and close tolerances. |
| Mechanical properties |
SMC can be used to produce parts with excellent mechanical
properties. For further information, see our Product
Datasheets. |
BMC can be used to produce parts with good mechanical
properties. For further information see our Product
Datasheets. |
| Dielectric properties |
SMC of the 70 and 72 series are used in the electrical
sector for parts with track resistance greater than 600 minutes
and arc resistance greater than 180 seconds. |
BMC of the 7100 series are used in the electrical
sector for parts with track resistance greater than 600 minutes
and arc resistance greater than 180 seconds. |
| Flame resistance |
Parts with high flame resistance can be obtained
particularly with SMC of the 70 and 72 (halogenated) series.
UL 94 method value V 0. |
BMC of the 7100 series can be used to obtain parts
with high flame resistance without halogen emission. UL 94 method
V O. |
| Testing approval |
SMC of the 70 and 72 series are UL Recognized
Components Underwriter Laboratories (USA and Canada). |
BMC of the 7100 series are UL Recognized Components
Underwriter Laboratories (USA and Canada). |
| Pigmentation and Paintability |
Most SMC can be in-mould coated or painted. High
shrink materials can be pigmented to deep or pastel colours and
low to zero shrink and low density materials can be pigmented
to a pastel or mottled colour. Flecks, specs or marbling can
be done. |
Most BMC can be in-mould coated or painted. High
shrink materials can be pigmented to deep or pastel colours and
low to zero shrink and low density materials can be pigmented
to a pastel or mottled colour. Flecks, specs or marbling can
be done. |
