Jawaharlal Nehru Technological University Hyderabad B.Tech III NON-METALLIC MATERIALS Previous Question Paper (February - 2023 - R18)

Polymethylmethacrylate (PMMA), commonly known as acrylic, is a transparent thermoplastic characterized by its exceptional optical clarity, high light transmission (up to 92%), and excellent resistance to ultraviolet radiation and weathering. It possesses good mechanical strength, high surface hardness, and rigidity, though it is relatively brittle compared to other engineering plastics. Additionally, PMMA is chemically resistant to many aqueous solutions and is easily fabricated through machining, thermoforming, or solvent welding.

Non-metallic materials are primarily classified based on their chemical composition, origin, and physical properties. The main categories include:

• Polymers: These are large molecules composed of repeating structural units. They are further divided into thermoplastics (which soften upon heating) and thermosetting plastics (which undergo irreversible chemical curing).
• Ceramics: Inorganic, non-metallic solids typically prepared by the action of heat and subsequent cooling. They include traditional ceramics (clay-based products like porcelain and bricks) and advanced ceramics (engineered materials like alumina and silicon carbide).
• Composites: Materials formed by combining two or more distinct constituents to achieve properties superior to the individual components, such as fiber-reinforced plastics.
• Natural Materials: Materials derived directly from biological or geological sources, such as wood, rubber, and leather.