Plastic and Stone Materials: Properties, Classification, and Uses

Plastic Materials and Polymerization

Plastic materials are formed through polymerization, a chemical reaction where low-molecular-weight molecules (monomers) bind together to create high-molecular-weight polymers. These substances can be manipulated and combined with other materials to create synthetic compounds with specific properties.

Physical and Optical Properties

• Physical: Low density, elastic, non-conductive to heat and electricity, impermeable, low melting point, malleable, ductile, tenacious, and non-biodegradable.
• Optical: Opaque, transparent, or translucent; most are colorless.
• Chemical: Generally resistant to atmospheric attacks, though some are sensitive to sunlight and water.

Additive substances are often added to improve characteristics, such as adding pigments or preventing oxidation.

Classification of Plastics

• Thermoplastics: Can be softened by heating, shaped, and cooled repeatedly. Examples include PVC, Polystyrene (PS), Polyethylene (high and low density), Polypropylene (PP), Methacrylate, Teflon, Cellophane, and Nylon.
• Thermostable (Thermosets): Once set, they cannot be reshaped and will degrade if reheated. Examples include polyester resin, epoxy resin, Bakelite, melamine, and rubbers like neoprene and silicone.

Manufacturing processes include injection, extrusion, and blowing for thermoplastics, and compression for thermosets. Plastics are identified by the recycling symbol (a triangle with arrows).

Stone Materials

Natural stone materials are extracted from rocks and classified by their formation:

• Sedimentary: Formed from deposits (e.g., limestone, conglomerate, sandstone).
• Igneous: Formed from the Earth's interior (e.g., granite, slate).
• Metamorphic: Formed under high pressure and temperature (e.g., marble).

Artificial Petreous Materials

These include ceramics (clay-based materials like bricks, tiles, and roof tiles) and glass (made by mixing soda, lime, and quartz).

Binders and Concrete

Binders are materials used to adhere components, such as gypsum, lime, and cement. Concrete is a vital construction material available in several forms:

• Mass concrete: Standard mixture.
• Reinforced concrete: Contains steel rods for added strength.
• Prestressed concrete: Steel beams subjected to tension.

Properties of concrete include docility, cohesion, consistency, density, and grip. Key construction terms include forging (hardening), formwork (molding), stripping (removing formwork), and structure (the framework of beams and pillars).