It’s lightweight, doesn’t corrode, comes in a limitless range of colors, and can be formed into an infinite variety of shapes. By “it” we are of course referring to plastic. Though it’s not yet a century since polyethylene was first created, it, and the many other plastics invented since, are used in just about every industry.
Plastics and Polymers
“Plastic” refers to the ability of a material to deform. Materials scientists and engineers prefer to talk about polymers rather than plastics. Polymers are long chains of molecules that consist mostly of carbon and hydrogen atoms. They’re made from liquids, sometimes gases, and the manufacturing process turns them into liquids and solids. Solid polymers are usually sold as granules and melted for molding shapes.
Polymers can be either thermoplastics and thermosets. Thermoplastics can be remelted and formed into other shapes while thermosets are formed once and can’t be melted. Thermosets tend to be stronger and more rigid than thermoplastics.
Today there are many types of polymer besides polyethylene. ABS, PVC, Nylon and PEEK are just a few. These were developed with specific properties, like strength at elevated temperatures and chemical and UV resistance.
Reasons for Preferring Polymer Materials
Polymers can often substitute for metal, glass, ceramics and to an extent, wood. As a general class of products their useful properties include:
- Low density
- Don’t corrode
- Don’t conduct electricity
- Good chemical resistance
- Flexible and impact-resistant
- Poor thermal conductivity
- Machinable
- Formable and moldable
- Can be colored (eliminating any need for surface coating)
- Can be transparent
Of course, there are exceptions. Some polymers are dense. Others are brittle rather than flexible. Many break down when exposed to UV light.
Although polymers are not as strong as metals, clever design and manufacturing process selection can create rigid polymer shapes. And not every application needs high strength anyway.
Forming Methods for Polymer Products
Polymer materials are turned into useful products by first producing them in sheet form or as extrusions, or molding them directly into the final shape.
Sheet material can be vacuum and/or thermoformed. These closely-related processes involve cutting the required shape from sheet, then pushing or pulling it onto a former that reproduces the geometry needed. In thermoforming the polymer is softened by heating so it deforms with less load and conforms better to the shape underneath.
After forming, the part is trimmed, holes or slots drilled and milled, and components added as needed.
The extrusion process creates long lengths with a uniform cross-section or profile. Extruded lengths of polymer are called extrusions and are sawed to length, drilled and milled as needed before being assembled.
Molding processes come in many types. Injection molding is the best-known, but needs mold tools that are complicated and therefore very expensive. This is why it’s only appropriate for very high volume production. Other molding techniques include Reaction Injection Molding (RIM), blow molding and rotational molding.
Applications for Polymers
Unless the application needs load bearing strength, thermal or electrical conductivity, or extremely high temperature resistance there’s almost certainly a polymer that’s up to the task.
Common applications include:
- Housings and enclosures – often thermo or vacuum formed
- Fascia panels – thermo or vacuum formed
- Trays and shelves – thermo or vacuum formed, can be customized to hold specific shapes
- Storage containers – thermo or vacuum formed
- Pulleys – could be produced from extrusion or machined from solid
- Brackets – could be produced from extrusion or machined from solid
- Doors and windows – usually extruded
- Door panels – thermo or vacuum formed
Industries using polymer products in applications like these include:
- Aerospace – for strength and weight-saving
- Automotive – for strength and weight-saving
- Other transportation (rail, marine …) – strength, weight-saving, corrosion resistance
- Appliance manufacturing – polymers result in attractive finishes and save weight
- Healthcare – lightweight and easy to clean
- Retail – for attractive finishes, easy clean surfaces
- Agriculture – want corrosion resistance, ease of cleaning
- Pharmaceutical and medical device manufacturing – want corrosion resistance, ease of cleaning
Most of these industries use polymer materials in their manufacturing processes as well as in what they make. Polymers like nylon make excellent guides for conveyors and chutes, they absorb impacts, provide damping and generally help reduce product damage while extending equipment life.
Meeting the Need for Quality Plastic Products
Compared to wood, ceramics, glass and most metal alloys, polymers are still a relatively new class of materials. Despite that, they have become essential in both the products we buy and use and the processes that make them. Without polymers everything would be heavier, bulkier and more expensive.
At C-Plex we can work with almost every polymer to produce a wide variety of plastic products for customers in a diverse set of industries. With vacuum, thermoforming, RIM, and machining and assembly, we give demanding customers the quality, precision and service they need. Contact us to learn more.
Sources
https://www.sciencemuseum.org.uk/objects-and-stories/chemistry/age-plastic-parkesine-pollution#
