1.3 Enhancement of materials

Material enhancement

A way of improving a material's properties to better suit the requirements of the final product

Polymer enhancement

Enhancing a polymer's properties by using additives (added to polymer stock form for variety of reasons)

Additives

a substance added to something in small quantities, typically to improve or preserve it.

Lubricants

The addition of wax or calcium stearate reduces the viscosity of the molten polymer, allowing more intricate shapes to be formed.

Thermal antioxidants

Prevent the polymer oxidising or discolouring due to excessive heat during processing.

Pigments

Tiny particles mixed into a polymer on the molten state to add colour to the final product.

Antistatics

improves surface conductivity, reducing the static charge or a polymer surrounding a wire.

flame retardants

Br, Cl, P and metal, when added to polymers reduce the liklihood of combustion

Plasticisers

Added to polymers to make them more flexible

Fillers

Provide bulk to a product so less polymer is used and improves polymer properties,

Antioxidants

Reduces the environmental deterioration of the polymer from exposure to oxygen in the air.

UV light stabilisers

Prevents polymer chains from being broken down in sunlight

Biodegradable plasticisers

Make the polymer more flexible, softer and easier to break down

Bio batch additives

oxy, hydro, and photodegradable additives that can be added for the polymer to break down more easily under the right conditions

Wood enhancement

Natural wood can have defects so they can be enhanced to improve quality.

Preservatives

Protects wood from fungal and insect attack, often copper based and pigments can also be added.

Polysaccharides

modified to improve wood hardness, toughness and stability, cures within the wood cell structure. This allows for softwoods to be used which grow much quicker than hardwoods.

Resins

Resins like urea formaldehyde are added to wood chips to create chipboard. The resin can have fire retardant additives giving more uses to the boards.

Laminations

a process in which a layer of material is pressed or glued onto other layers, this creates a stronger material

Metal enhancements

Metals have a range of properties that can be enhanced through the controlled application of heating and cooling.

Work hardening

Also known as strain hardening or cold working, this is the process of toughening a metal through deformation.

Annealing

Makes a work hardened metal less brittle and more ductile. The metal is heated and slowly cooled.

Case hardening

hardens the surface of steels with les than 0.4% carbon content, is a two stage process.

Carburising

first stage of case hardening, changes the chemical composition of the surface so it can absorb more carbon .

Steel placed in sealed box packed with carbon, heated to 930 to 950 degrees, so the carbon atoms diffuse into the materials structure.

Quenching

second stage of case hardening, the metal is quenched in water, this cools the material quickly which seals the surface case.

Hardening

process of heating medium and high carbon steels to alter the crystalline structure and quenching them This increases the hardness but also increases the brittleness.

Tempering

Carried out after hardening to reduce the excess hardness and increase toughness, this decreases the brittleness.

The metal is heated to below the critical point for s time then slowly air cool.

Critical point

the temperature at which the atoms of carbon and steel mix freely before bonding together to become solid.