Enhancement of materials.
Technical principles
Polymers
Polymer Enhancement
ENHANCEMENTS OF MATERIALS
Polymer enhancement
Polymers are enhanced by adding additives to the polymer stock, usually while the polymer is molten during processing. These additives improve processing, performance, durability, safety, and environmental behaviour.
Polymer additives and reasons for adding them
Lubricants
Reduce the viscosity of molten polymer, making it less sticky and easier to mould.
Allow more intricate shapes to be formed and enable lower moulding temperatures, reducing energy use.
Thermal antioxidants
Prevent oxidation of the polymer during high-temperature processing.
Reduce heat-related discolouration and degradation.
Pigments
Fine particles mixed into molten polymer to provide colour in the final product.
Affect appearance rather than mechanical properties.
Antistatic additives
Reduce the build-up of static electrical charge on the polymer surface.
Used where static could cause handling or safety issues.
Flame retardants
Reduce the likelihood of combustion and slow the spread of fire.
Commonly used in electrical products and vehicle components.
Plasticisers
Reduce hardness and brittleness at room temperature, increasing flexibility.
Improve processability by allowing polymers to be formed more easily at higher temperatures.
Example: added to LDPE food wrap to allow stretching over food.
Fillers
Increase bulk so less polymer is required, reducing material cost.
Mineral fillers increase thermal conductivity, allowing faster heating and cooling.
Shorter heating and cooling times result in reduced mould cycle times.
Biodegradable plasticisers
Make polymers softer and more flexible while increasing ease of breakdown.
Result in faster degradation compared to standard plastics.
Bio-batch additives
Include oxy-degradable, photo-degradable, and hydro-degradable additives.
Reduce degradation time from hundreds of years to a few years or months.
Antioxidants
Reduce environmental deterioration caused by oxygen exposure.
Prevent brittleness, surface cracking, and pigment discolouration in outdoor use.
UV light stabilisers
Prevent polymer chains breaking down due to ultraviolet radiation.
Reduce colour fading and embrittlement in outdoor products.
Woods
Wood enhancement
Wood is enhanced to improve durability, stability, strength, appearance, and resistance to environmental damage, particularly for outdoor or structural use.
Wood enhancement methods
Resins and laminations
Used in engineered woods to enhance the usable parts of trees such as chips, fibres, and sawdust.
Chipboard is made by compressing wood chips with resin (e.g. urea formaldehyde).
Produces boards that are stable, uniform in strength, and less affected by humidity and temperature.
Resins with fire retardants
Resin is impregnated with fire-retardant chemicals to reduce flammability.
Used in applications such as indoor flooring and cladding.
Laminations
Thin veneers bonded to the surface of boards to improve appearance.
Allow lower-cost materials to resemble solid hardwood.
Preservatives
Protect wood, especially outdoors, from fungal and insect attack.
Copper-based preservatives penetrate deeply and protect the entire plank.
Pigments
Added to preservatives to change colour and improve appearance.
Can be used to make softwoods resemble hardwoods.
Fire-retardant preservatives
Used to pressure-treat wood for joists, cladding, and exhibition structures.
Reduce flammability and can increase surface hardness for flooring.
Modified natural polysaccharides
Chemicals impregnated into wood that cure within the cell structure.
Increase hardness, toughness, and dimensional stability.
Structural composite lumber (SCL) and laminated veneer lumber (LVL)
Manufactured by layering wood strands or veneers with resin and curing under heat and pressure.
Produce stable sections with fewer defects such as warping or splitting.
Used in beams, joists, and rafters due to high load-bearing capacity.
Metals
Metal Enhancement
METAL ENHANCEMENTS
Metal enhancement uses controlled heating or mechanical working to change the internal structure of a metal. By changing how the metal’s crystals behave, we can make the metal harder, stronger, or easier to shape, depending on the process used.
Work hardening (cold working)
Work hardening happens when a metal is shaped without heating, for example, by bending, rolling, hammering, or pressing.
Cold working forces the metal’s crystal structure out of its original shape, which makes the metal stronger and harder in the worked area.
As the crystals become distorted, they cannot move easily, which reduces ductility and makes the metal more likely to crack if worked further.
This is why metals can become difficult to shape after repeated bending or hammering.
The effects of work hardening can be removed by annealing.
Annealing (undoing work hardening)
Annealing is used to make a work-hardened metal easier to shape again.
The metal is heated and then cooled very slowly.
Slow cooling allows the metal crystals to rearrange into a more regular structure.
This reduces internal stress, lowers hardness, and restores ductility.
As a result, the metal becomes less brittle and easier to work.
Case hardening (hard outside, tough inside)
Case hardening is used when a component needs a hard, wear-resistant surface but a tough inner core.
It is used on steels with less than 0.4% carbon content.
The surface of the steel is hardened to resist wear and indentation.
The core remains softer, allowing the part to absorb shock without breaking.
This makes the process ideal for components such as gears and shafts.
Case hardening process (step by step)
Step 1: Carburising (adding carbon to the surface)
Carburising increases the carbon content only at the surface of low-carbon steel.
The steel is placed in a sealed ceramic box packed with carbon.
The box is heated to about 930–950°C, allowing carbon atoms to diffuse into the steel’s surface.
The longer the steel remains at this temperature, the deeper the carbon-rich layer becomes.
After carburising, the steel is reheated to around 760°C to prepare it for quenching.
Step 2: Quenching (locking in hardness)
Quenching rapidly cools the steel to lock the hard surface in place.
The hot steel is quenched in water to cool the surface quickly.
Rapid cooling hardens the carbon-rich outer layer.
The inner core cools more slowly and remains tough rather than brittle.
Hardening
Used on medium- and high-carbon steels to alter the crystalline structure.
Steel is heated, held at temperature, and rapidly quenched in water, oil, or salt-water baths.
Increases hardness but also increases brittleness.
Tempering
A secondary heat treatment carried out after hardening.
Reduces excess hardness and brittleness while increasing toughness and ductility.
Metal is reheated below the critical temperature, held, then air cooled.
Tempering colour indicates the temperature reached and the amount of brittleness removed.