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24) Styrene-methyl-methacrylate (SMMA):
is a transparent copolymer consisting of styrene units (monomer of PS) and methyl-
methacrylate units (monomer of PMMA). Acrylate is a rubber component
dispersed in the SMMA matrix to make material more ductile. A dispersed rubber
phase usually creates a non-transparent material (as in ABS), but a smart choice of
the ratio between S and MMA has created a matrix, so light can pass undisturbed.
Impact modified SMMA can be used as an alternative for PC and other transparent
polymers, although the temperature resistance is lower than PC.
Density 1.05 - 1.13 g/cm 3
Max continuous Service temperature 94 - 100 °C
Melting point 190 - 220°C
Injection Moulded at temperature : 190 - 220°C and mould temperature of 35 to 55°C
Strengths: Very high transparency and clarity, excellent surface finish, good
processablity, reduce processing costs compared to clear ABS and PC, FDA
compliant, Highly resistant to gamma, e-beam and ethylene oxide sterilization,
Biocompatible, easily be colourised and printed
Limitations: Low UV resistance, not suitable for outdoor applications, Attacked by
aromatic hydrocarbons, halogenated compounds, oxygenated materials
unsaturated oils and concentrated acid.
Applications: Point-of-Purchase displays, Cosmetic rigid packaging , Water
Pitchers, Medical products like Blood Filter, Medical brush handles, Urine meters,
clothes hangers, toys, games, impact resistant CD and DVD boxes, computer
equipment, kitchen equipment, office equipment, bathroom articles.
25) Polymethyl Methacrylate (PMMA):
PMMA is a transparent amorphous polymer produced by polymerizing methyl
methacrylate (MMA) monomer. Acrylic is a hard, rigid material (it has hardness
comparable to aluminium) which maintains its clarity even with thick sections and
after long exposures to outside atmospheres.
Density 1.17 - 1.2 g/ cm 3
Glass transition temperature 90 - 110 °C
Max continuous Service temperature 70 - 80 °C
Pre-drying the granules for up to 8 hours at 70-100°C recommended unless
processed with vented cylinder to avoid surface defects and blisters.
Injection Moulding: Melt temperature: 200-250°C and Mould temperature: 40-80°C.
Extrusion: Melt temperature: 180-250°C. A degassing screw with an L/D ratio of
20-30 is recommended.
Casting from a liquid precursor (liquid MMA), large objects and thick sheets can be
made without shrinkage and stress problems.
PMMA stands out from other plastics due to its excellent transparent, glossy finish
with high light transmission (> 92%) combined with outstanding strength and
stiffness. Exhibit extremely long service life having high resistance to UV light (do
not yellow when exposed to sunlight) and weathering. They have high resistance to
breakage (17 times that of double-strength glass) and will not warp, crack, craze, or
corrode when subjected to prolonged outdoor environments with unlimited
colouring options. Service temperatures range from -4 °C to + 115 °C.

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