Plastic is a synthetic material made from polymers,
which are large molecules composed of repeating subunits. These forms can be
liquid or paste like resins for embedding, coating, and adhesive bonding, or
they can be moulded, laminated, or formed shapes, including sheet, film, or
larger-mass bulk shapes. It can be
moulded into various shapes and forms, making it a versatile material widely
used in electrical insulation, packaging, construction, and many other industries.
Powermat uses two type of polymer, thermoplastic and thermoset plastics.
Thermoplastic: Plastics that can
be deformed easily upon heating and can be bent easily. Linear polymers and a combination
of linear and cross-linked polymers come under thermoplastics. Example: PVC,
nylon, polythene, etc.
Thermosetting: Plastics that
cannot be softened again by heating once they are moulded. Heavily cross-linked
polymers come under the category of thermosetting
plastics. Example: Bakelite, melamine, Sheet Moulding Compound &
Dough Moulding Compound.
Thermoset Composite
Material & its Moulding Technique
Composites are defined as “a combination of plastic
resin and fibre reinforcement.” Another term for composites is used in the past
is reinforced plastics.
Sheet
Moulding Compound:
Sheet moulding compound (SMC)
or sheet moulding composite is a ready to mould glass-fibre reinforced polyester material primarily used
in compression
moulding.[1] The sheet is provided in
rolls weighing up to 100 kg. Alternatively, the resin and related
materials may be mixed on site when a producer wants greater control over the
chemistry and filler.
Process:
Sheet Moulding
Compound (SMC) is a compression moulding compound often used for larger parts
where higher mechanical strength is needed. SMC is a fibre reinforced thermoset
material. Glass reinforcement is between 10% and 50%, and glass length is
slightly longer than Dough Moulding Compound (DMC) - between 1/2-inch and
1-inch (25mm).
Thermoset Sheet Moulding Compound
(SMC) is a mixture of polymer resin, inert fillers, fiber reinforcement,
catalysts, pigments and stabilizers, release agents, and thickeners and
possesses strong dielectric properties. Manufacture of sheet moulding compounds
is a continuous in-line process. The material is sheathed both top and bottom
with a polyethylene or nylon plastic film to prevent auto-adhesion. The paste
is spread uniformly onto the bottom film. Chopped glass fibers are randomly
deposited onto the paste. The top film is introduced and the sandwich is rolled
into a pre-determined thickness. The sheet is allowed to mature for 48 hours.
Sheet moulding compounds can be moulded into complex shapes. Superior
mechanical properties and surface appearance, plus excellent electrical
insulation make this thermoset material ideal for automotive Class A body
panels, high-strength electrical parts, business equipment cabinets, personal
watercraft, and various structural components.
Dough
Moulding Compound:
Dough Moulding Compound (DMC) is a thermoset plastic resin blend of
various inert fillers, fiber reinforcement, catalysts, stabilizers, and
pigments that form a viscous, `puttylike` moulding compound. DMC is highly
filled and reinforced with short fibers. Glass reinforcement represents between
10% and 30%, with glass length typically between 6mm to 12mm. Depending on the end-use application, dough moulding
compounds are formulated to achieve close dimensional control, flame and track
resistance, electrical insulation, corrosion and stain resistance, superior
mechanical properties, low shrink, and colour stability. Its excellent flow
characteristics, dielectric properties, and flame resistance make this
thermoset material well-suited to a wide variety of applications requiring
precision in detail and dimensions as well as high performance.
Process
Basic raw materials are resins, additives, catalysts, mould release
agents and fillers. For coloured compounds, a pigment is added to the paste.The
paste is then mixed with fibres, usually glass fibres. Bulk Moulding Compound
(BMC) is prepared in a mixer. After preparing a base paste it will be loaded
into the mixing device. Then all other ingredients are added and homogenized.
The compound is packed into bags until moulding. To avoid any material changes
during storage and transport it is packaged in a styrene tight packaging.
