The three components shown below were manufactured from plastic materials - Leaving Cert Engineering - Question 5 - 2012

Injection Moulding is a manufacturing process where thermoplastic is heated until it is pliable. The molten plastic is injected into a mould using a plunger. Once in the mould, it cools and hardens rapidly, forming the desired shape.

The key steps are:

1. Heating of the thermoplastic.
2. Injection into the mould.
3. Cooling and solidification of the plastic.
4. Ejection of the final product.

1. Do not hold acrylic sheet by hand when drilling; always use a hand vice or machine vice to secure.
2. Use a slow feed when drilling and use a wooden block to support the acrylic sheet underneath.

(i) Thermosetting plastic

Thermosetting plastics are three-dimensional structures with strong cross-links between molecules, making them rigid and hard. They cannot be remoulded once set.

(ii) Elastic memory

Elastic memory refers to the ability of a thermoplastic to return to its original shape when heated. This property allows for shape-recovery applications.

(iii) Thermoplastic

Thermoplastics are linear chain-type polymers that are flexible and can be repeatedly softened and remoulded upon heating.

1. Plastics can take up to 50-80 years to decompose, leading to long-term waste accumulation in the environment.
2. Burning or incinerating plastics can release toxic substances, contributing to air pollution and harming ecosystems.