Understanding Plastics: Monomers, Polymers, and Molding

What are Monomers and Polymers?

Plastics are formed by the combination of low molecular weight molecules called monomers. Polymers are formed by joining monomers.

• The union of monomers results in large molecules called polymers.

What is Polymerization?

Polymerization is a chemical reaction that joins monomers into large chains to build macromolecules called polymers.

Artificial vs. Synthetic Plastics

Artificial plastics are created by transforming natural materials. Synthetic plastics are created from materials such as oil and gas.

Thermoplastics vs. Thermosetting Plastics

Thermoplastics can be heated and molded multiple times. Thermosets can only be heated and molded once.

Plastic Applications

Thermoset Applications

• Phenol formaldehyde (PF) combined with acrylic
• Unsaturated polyester resins (UP)

Thermoplastic Applications

• Polyvinyl chloride (PVC)
• Polyethylene (PE)

General Applications

• Tubes
• Profiles
• Cable insulation
• Roofing
• Pools
• Electrical accessories
• Water containers

Plastic Molding Techniques

Injection Molding

In injection molding, the plastic material is pushed by a plunger and injected into a mold, where it takes shape.

Blow Molding

In blow molding, the plastic material is pushed by a piston and inserted into a hollow cylinder. Air is then forced into the cylinder under pressure until the material conforms to the walls of the mold.

Plastic Joining Methods

Three common methods for joining plastics are:

• Drilling
• Plastic joints
• Bonding/adhesion

What are RSU?

RSU stands for Residuos Sólidos Urbanos, which translates to Solid Urban Waste.

Uses of Plastic Containers

Different colored containers are used for different types of waste:

• Blue: Paper
• Green: Glass
• Yellow: Plastic packaging
• Gray: Rubbish and debris

Binders and Conglomerates

Binders

Binders are materials that, once mixed with water, have the ability to harden. Example: Cement

Conglomerates

A conglomerate is a body made up of various elements held together cohesively. Example: Concrete

Examples of Ceramic Materials

• Tiles
• Stoneware
• Refractories

Tools and Their Uses

• Shovel: Used for digging
• Pickaxe: Used for digging or breaking up stone materials
• Chisel: Used for chopping