polymer, wood and metal enhancements

Polymer Enhancements

• Lubricants

• Thermal antioxidants

• Pigments

• Antistatics

• Flame retardants

• Plasticisers

• Fillers

• Antioxidants

• Bio-batch materials

  • Biodegradable plascicisers

  • Bio-batch additives

• UV stabilisers

Lubricants

Polymer Enhancement - adding wax or calcium stearate reduced the viscosity of the molten polymer, making it less sticky and allowing more intricate shapes to be formed

Thermal antioxidants

Polymer Enhancement - prevent the polymer oxidising or discolouring due to excessive heat during processing

Anti-statics

Polymer Enhancement - reduce the likelihood of the polymer building up static charge

Flame / fire retardants

Polymer Enhancement - reduces the likelihood of combustion, spread of fire or potential electrical fires

Wood Enhancement - resin can be impregnated with fire retardant cladding (e.g. for indoor flooring) or the fire retardants can be used to pressure treat the wood, making it more resistant to wear

Plasticisers

Polymer Enhancement - allows plastics to become less hard and brittle at normal temp use (e.g. LDPE food wrap), they also help in processing as they allow polymers to be easily formed at higher temperatures

Fillers

Polymer Enhancement - sawdust and wood flour provide bulk to the product, meaning less polymer is required, and mineral fillers (chalk & clay) help increase the thermal conductivity ∴ the material heats up and cools down quicker

Biodegradable plascicisers

Polymer Enhancement - these make the polymer more flexible, softer and easier to break down → faster degradation time

Bio-batch additives

Polymer Enhancement - oxy-degradable, photodegradable and hydro-degradable additives help reduce the degradation time from hundreds of years to a few months

UV stabilisers

Polymer Enhancement - prolongs the life by preventing the polymer chains being broken down by sunlight, used for outdoor products like patio furniture, vehicle parts, roofing materials

Advantages

• Prolong the lifespan of polymers by preventing degradation from UV light exposure

• Maintain strength, colour, and integrity, especially for outdoor applications

Disadvantages

• Can be expensive, affecting the overall cost of polymer products

• Effectiveness may degrade over time with prolonged exposure to UV light

Bio-batch materials

Polymer Enhancement - encourage biodegradability, used for food packaging, carrier bags, biodegradable plastics

Advantages

• Encourage biodegradability of plastics, reducing their environmental impact

• Can be used in products like food packaging and carrier bags for more sustainable disposal

• Contribute to the development of compostable plastics that break down in natural environments

Disadvantages

• May require specific conditions for complete biodegradation (e.g. industrial composting facilities)

• Potentially more expensive than traditional polymers without additives

• Can affect mechanical properties of the polymer (e.g. flexibility or strength)

Antioxidants

Polymer Enhancement - help reduce the environmental deterioration of the polymer from exposure to oxygen

Wood Enhancements

• Resins and laminations

• Resins w/ fire retards

• Laminations

• Preservatives

• Pigments / paints

• Fire retardant preservatives

• Modified natural polysaccharide

• Structural composite lumber (SCL) and lamination veneer lumber (LVL)

• Varnishes

The combination of natural timber with resins and lamination can enhance properties, e.g. increased strength and stability

Enhancing timber products with preservatives, finishes and coatings

Resins and laminations

Wood Enhancement - used in engineered woods to enhance the properties of the useable parts of trees, such as sawdust, wood chips and fibres e.g. chipboard

Modified natural polysaccharide

Wood Enhancement - wood is impregnated to cure within the wood cell structure, increasing hardness, toughness and stability

Structural composite lumber (SCL) and lamination veneer lumber (LVL)

Wood Enhancement - made by layering SCL strands or veneers (LVL) of wood with resins, pressing and heat curing them to produces a stable wood billet → they’re less prone to warping, splitting and shrinking, while also having greater load bearing properties

Lamination

Wood Enhancement - bonding layers of wood together for complex shapes or added strength, used for bridges and kitchen tables

Process

1. Thin layers of wood are cut out and stuck together using adhesive inbetween each layer (usually PVA)

2. A former is used to achieve the desired shape

3. Clamps/vaccuum bag apply pressure whilst the adhesive sets

4. Once formed the laminated  timber can be trimmed and sized

Advantages

• Economic to use (uses whole tree)

• Can be shaped into a curve/complex shapes

• Comes in large sheets

• Strong material

• Lighter than solid wood

Disadvantages

• Poor surface finish

• Layers of material are visable and not very aesthetically pleasing

• Can be damaged by water/moisture which leads to delamination

• Difficult to be recycled

• Can release formaldehyde which is toxic

Preservatives

Wood Enhancement - used for wood products exposed to water and corrosion

Advantages

• Improves lifespan of timber

• Reduce biological corrosion

• Improves aesthetics of wood

Disadvantages

• Toxic

• More effective if used to pressure treat wood

Paints

Wood Enhancement - used for bridges, wooden decking

Advantages

• Stops rusting/corrosion

• Aesthetically pleasing

• Range of colours

• Saves time/money

Disadvantages

• Chips/flakes away

• Not environmentally friendly

Varnishes

Wood Enhancement - used to enhance and protect the woods

Advantages

• Protects from dirt/sunlight/water

• Enhances look of wood

• Easy to apply

• Can't see brush strokes

Disadvantages

• Can be dull colour

• Bubbles can ruin finished look

• Some varnishes are bad for the environment (brushes cleaned result in varnish into water system)

Metal enhancements

Heat treatment can enhance metal properties

• Work hardening

• Annealing

• Case hardening

• Hardening

• Tempering

Work hardening

Metal enhancement - when the metal is ‘cold worked’ by bending, rolling or hammering

• the crystals within the metal are distorted and changed, leading to improved tensile strength and hardness in the worked area

• when the metal crystals are distorted, they cannot more freely within the metal structure ∴ less ductility, more cracking and more damage in worked area

• undesirable affects can be removed by annealing

Annealing

Metal enhancement - make the work-hardened metal easier to work by making it less brittle and more ductile

• the metal is heated and then cooled very slowly

• this allows the metal crystals to grow and slowly move into place

Case hardening

Metal enhancement - used to harden the surface of steels with less than 0.4% carbon content, producing an outer casing of greater hardness with the inner core of the metal retaining the original ‘softer’ properties

Process (two stages)

1. Carburising: this changes the chemical composition of the surface of the steel so that is can absorb more carbon to increase hardness

   • the metal is placed in a ceramic box packed with powdered carbon and heated to 930C for a period of time

   • carbon is then absorbed by the metal, the depth of absorption is determined by the length of time if carbursing (the longer the time, the thicker the carbon layer)

   • the product is then heated to about 760C and quenched

2. Quenching: the hot metal is quenched in water to fast-cool it and seal the hard surface while not affecting the properties of the inner core

   • This stops the carbon escaping the surface of the metal

Advantages

• Greater hardness for outside surface

• Improved wear resistance

• Resistance to surface indentations

• Low coefficient of friction

• Internal properties of metal remain unchanged

Disadvantages

• Depth of hardness is not fully known

• Difficult to machine metal after process

Hardening and tempering

Metal enhancement - used for screwdrivers, wrenches, hardened steel

• Hardening: steels are heated to alter their crystalline structure, increasing hardness and brittleness (step 1, 2 and 3)

• Tempering: reduces some of the excess hardness and brittleness of a hardened metal, while also increasing the toughness and ductility (step 4)

Process

1. Medium/High carbon steel is heated to a given temperature (below critical temperature) and held there for a period of time

2. It is then quenched in water/oil

3. The metal has now been hardened which improves certain properties but makes the metal very brittle

4. As a result the metal is reheated to a given temperature (below critical temperature) and allowed to cool slowly

Advantages

• Improved tensile strength

• Very hard

• Reversible process (via annealing)

Disadvantages

• Metal becomes less ductile

• Metal is more likely to crack/damage in worked area

• Metal becomes more brittle