Material enhancement means making a material stronger or better for its purpose. We often do this with plastics, wood, and metals. For example, some metals break easily when bent. But by heating them up, we can change their structure to make them tougher and less likely to break.
In this unit, we'll focus on making materials stronger or better for what they need to do, instead of just making them look nicer.
POLYMER ENCHANCEMENT.
Additives to make polymer easier and less expensive to process.
Polymers are usually resistant to chemicals and mold, but we can make them even better with additives.
Some additives help make polymers easier and cheaper to work with. For example:
- Lubricants like wax make the polymer less sticky, so it's easier to shape.
- Thermal antioxidants stop the polymer from changing color when it gets hot.
- Pigments give the polymer different colors.
These additives help improve how polymers are made and what they look like in the end.
Additives to improve product function.
Some additives make polymers work better for what we need them to do. Here are a few examples:
- Antistatic: These help reduce static electricity in polymers, making them less likely to give you a shock.
- Flame retardants: They help stop fires from spreading, especially in things like engines and electrical sockets.
- Plasticisers: These make polymers softer and less likely to break. They're often used in food packaging.
- Fillers: Fillers bulk up the product or make the polymer better. Things like sawdust or chalk are common fillers.
- Mineral fillers: These can make the polymer heat up and cool down faster, which helps speed up the manufacturing process.
Additives to prolong life (prevent degradation).
Antioxidants keep the polymer from getting bad when it's exposed to air. When polymers degrade, they become brittle, change color, and get surface cracks.
UV light stabilizers stop the polymer from breaking down when it's in sunlight. Otherwise, it can change color, become brittle, and lose its strength. These stabilizers are often used in things like outdoor furniture and plastic windows.
Additives to encourage degradation.
Some additives help the polymer break down faster. Here are a few examples:
- Biodegradable plasticizers: These make the polymer softer and easier to break down, so it doesn't last as long.
- Oxy-degradable polymers: They break down over time when they're exposed to oxygen. They're often used in things like plastic bags.
- Photodegradable polymers: These break down when they're exposed to sunlight.
- Hydro-degradable polymers: They break down when they're in water.
These polymers can be made to last for different amounts of time, so they won't stay in landfills for too long.
WOOD ENHANCEMENT.
Natural wood can sometimes have problems like splits or knots, which can make it less stable. That's why we have manufactured boards like MDF and plywood. Natural wood has some drawbacks:
- It gets weaker when it gets wet.
- It can easily catch fire.
- It can rot or get attacked by insects and mold.
- It's anisotropic, meaning it has different properties in different directions.
Enhancement using preservatives.
People love using wood in buildings because it's strong, looks nice, and keeps buildings warm. It's also renewable. But, it can get damaged by insects, rot, and weather. To make it last longer, we use preservatives. You can learn more about this in section 1.5 about finishes.
Wood can also be made tougher for places with lots of foot traffic, like floors. We do this by adding something like cellulose, which makes the wood stronger and more stable.
Resins and laminations.
Industries use engineered wood a lot to make tree parts better for use.
Structural composite lumber (SCL) and Laminated veneer lumber (LVL) are two types of engineered wood. They're made by sticking together thin pieces of wood with resins and heating them up. This makes them strong and useful.
Even though they're not natural, we use these engineered woods for building things like beams, joists, and rafters.
METAL ENHANCEMENT.
There are lots of different metals, and each one has its own strengths and weaknesses, like how tough or hard it is. So, not all metals need the same kind of enhancements. For example, metals with iron need a finish to stop them from rusting, but other metals don't.
One way to make metal stronger is by "cold working" it, which changes its structure and makes it tougher. But this can also make it brittle. So, we use something called annealing to make it less brittle and easier to work with. We heat it up and then cool it slowly.
Another process, called case hardening, is used to make the surface of low-carbon steels harder. First, we change the surface by adding more carbon. Then, we quickly cool it in water to seal in the hardness.
Hardening and tempering.
Hardening is when we heat up medium and high carbon steels, keep them hot for a while, then cool them quickly in water, oil, or salt baths. This makes them much harder, but also more brittle.
Tempering is a heat treatment we do after hardening to make the metal less hard and more flexible. We heat it up again, but not as much as before, and then let it cool in the air. This makes it less brittle and tougher.
SUMMARY.
Materials have different properties, like how they look and how strong they are. But we can make them even better using different methods.
Even though wood is natural, we can still make it better by mixing it with other things like resin to make engineered wood.
Polymers, which are man-made, can be improved by adding things to them.
Metals have their own properties, but we can change them by heating them up, cooling them down, or making them harder on the outside.