Acrylic and Heat bending Flashcards
What is acrylic also known as?
Poly(methyl methacrylate) (PMMA)
What are the advantages of using acrylic?
Advantages:
- Transmittance is the ratio of the light energy falling on a body to that transmitted through the material – PMMA (Acrylic) polymer has a Refractive Index of 1.49 and hence offers high light transmittance. PMMA grades allow 92% of light to pass through it, which is more than glass or other plastics.
- These plastic materials can easily be thermoformed (heated and bent) without any loss in optical clarity.
- As compared to polystyrene and polyethylene, PMMA is recommended for most outdoor application thanks to its environmental stability.
- Surface Hardness – PMMA is a tough, durable and lightweight thermoplastic. The density of acrylic ranges between 1.17-1.20 g/cm3 which is half less than that of glass. It has excellent scratch resistance when compared to other transparent polymers like Polycarbonate, however less than glass. It exhibits low moisture and water absorbing capacity, due to which products made have good dimensional stability.
- UV Stability – PMMA has resistance to UV light and weathering. Most commercial acrylic polymers are UV stabilized for good resistance to prolonged exposure to sunlight as its mechanical and optical properties fairly vary under these conditions, Hence, PMMA is suitable for outdoor applications intended for long-term open-air exposure.
What are the limitations of PMMA?
Limitations of PMMA:
- Poor impact resistance
- Limited heat resistance (80°C)
- Limited chemical resistance, prone to attack by organic solvents
- Poor wear and abrasion resistance
- Cracking under load possible
- Environmental Impact
What is heat bending?
Heat bending is a manufacturing method used to bend a flat thermoplastic with the use of machines and heating to make the material temporarily more malleable than it is in its cool state.
How does heat bending work?
Since thermoplastics soften when heated and harden when cooled, they can be modified with heat and once cool, the plastic holds its basic form with the new shape. With focused heat, thick rigid plastic materials can be folded in half (180 degrees) or bent to other angles using special cooling fixtures. Thermoplastics like acrylic, polystyrene, expanded PVC, PETG, and polycarbonate are just some of the materials we hot-wire heat bend. With so many different types of plastic and thicknesses, the heat bending process will vary. What ties all these materials together is that all plastics can be shaped with heat and hold that shape once cooled.
How does heat bending work?
The process of line bending starts with holding a hot wire or heating element near the surface to be bent. When taut, the hot wire radiates focused heat in a straight line across the material. The wire creates a very focused heat making only that straight line malleable. Once the plastic has met the appropriate temperature, it is quickly removed and placed into a former or jig to cool.
