Understanding Plastics, Textiles, and Ceramics
Plastics
Plastics are made of materials formed by long chains containing carbon atoms.
Their Properties
They are very good electrical insulators, resistant to many chemical agents. The process of obtaining them is economical. Pieces of plastic can be manufactured cheaply. Plastics are not biodegradable.
Classification of Plastics
- Thermoplastics are those that soften when heated and can be shaped many times.
- PVC: Impermeable, flexible.
- High-density polyethylene: Rigid, resistant, and transparent.
- Low-density polyethylene: White, light, and transparent.
- Expanded polyethylene: Used as packaging, is transparent.
- Methacrylate: Bright.
- Cellophane: Used for packaging.
- Thermosets: Can only be heated once.
- Melamine: A binder used for furniture.
- Resin: Mixed with fiberglass to make bodywork.
- Elastomers: Plastics that are obtained by mixing sulfur with rubber. Rubber tires utilize this.
Forming Technology
- Extrusion: Thermosetting material in granular form is introduced into a hopper and plunged into a heated cylinder.
- Calendering: Consists of passing the thermoplastic material, previously heated, between rollers rotating in order to obtain prints and plates.
- Blow Molding: The material is introduced into a mold whose upper hole corresponds to the shape of the object. It is closed, and once closed, compressed air is injected. After cooling, the material is removed.
- Vacuum Forming: The thermoplastic material is introduced into a mold. Air is sucked out, causing the material to suit the mold’s walls and take the desired shape. Once open and after cooling, it is removed.
- Injection Molding: Thermoplastic is injected into a mold. When the material is set, the mold is opened, and the formed piece is removed.
Textile Materials
Textiles are materials formed by fibers that can be spun. The fibers can be:
Natural Fibers
- Cotton: Good thermal insulator, resistant, lightweight, and permeable.
- Flax: Obtained from the stalk of the flax plant. It is elastic and a good electrical conductor.
- Esparto: Extracted from the leaf of the esparto grass. It is hard and tenacious, and much used in the footwear industry.
- Animal Fibers:
- Wool: Comes from sheep hair. It is very elastic.
- Silk: Segregated by caterpillars. The fiber is very soft, bright, elastic, and tenacious.
Synthetic Fibers
Nylon, polyester, viscose, Lycra, and acrylic.
Stone Materials and Ceramics
Stone materials are obtained from rocks, which are found in nature in large blocks. They are materials of high density, cold to the touch, and hard.
- Plaster: Made from gypsum stone that is ground and heated to dehydrate it. It is mixed with water to obtain a hardened paste.
- Mortar, Concrete, Cement.
Ceramic Materials
Obtained from clay as the primary material. It is molded and submitted to a cooking process in an oven. Ceramics are divided into two groups:
- Coarse Ware: Made from ordinary clay.
- Fine Ware: Obtained from soft clay.
Glass: A transparent, impermeable material, soft to the touch but very fragile. It is obtained from quartz.