| |
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. |
