Additives to help polymer flow into mould

Process aids. Lubricants (eg wax) to reduce viscosity - intricate shapes - and lower mould temp Thermal antioxidants

Attract moisture from surroundings to reduce static charge

Important for car engine components or plug sockets.

Make less hard and brittle at room temp. e.g. LDPE food wrap Also make it easier to form when at high temps

Bulk. Mineral fillers increase thermal conduct - heat and cool fast so short mould cycle times

Oxidation in plastics

Brittleness, surface cracks, pigment discolouration

Biodegradable plasticisers

Flexible, softer, and easier to break down

Oxy-degradable, photo, hydro. Years or months. High volume single use.

Weak wet. Burns. Fungi, insect, rot. Anisotropic - diff properties in diff directions

Copper based - fungicide Impregnated with polysaccharide - hard, tough, stable. Can be pigmented to make softwoods look hard.

Engineered wood Often compressed with a resin - less temp and humidity changing and uniform strength. Impregnated with fire retardant. Veneered. SCL (structural composite lumber) and LVL (laminated veneer). Veneers/strands layered into billet

Cold worked. Crystals distorted. Strong and hard in worked area. Less free metal crystal movement: less ductile, cracking, damage. Can be reversed via annealing.

Less brittle more ductile. Heated then v slowly cooled so crystals grow and slowly move back into place. In industry temp-controlled furnace used. Brazing hearth in school.

Surface of steels less than 0.4 carbon. Outer casing harder and resist indenting while inner core has softer properties. Better wear resistance. Carburised (heated to 900+C in carbon filled box or dipped) then water quenched at 750C - seals case

Medium and high carbon steel. Hold at high temp then quench in water, oil, or salt water. Harder but brittle. Have large internal stresses afterwards. Often much harder than required and too brittle for many practical uses

Heat treatment for medium and high C steels after hardening to reduce excess hardness and toughen. More ductility and less brittle. Heated to below the critical point (when carbon and steel atoms mix freely) for a given time then slowly air cooled.

Tempering temperatures

Exact temps determines hardness removed

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DT 1.3

DT Spring Y12

Question	Answer
Additives to help polymer flow into mould	Process aids. Lubricants (eg wax) to reduce viscosity - intricate shapes - and lower mould temp Thermal antioxidants
Antistatics	Attract moisture from surroundings to reduce static charge
Flame retardants	Important for car engine components or plug sockets.
Plasticisers	Make less hard and brittle at room temp. e.g. LDPE food wrap Also make it easier to form when at high temps
Fillers	Bulk. Mineral fillers increase thermal conduct - heat and cool fast so short mould cycle times
Oxidation in plastics	Brittleness, surface cracks, pigment discolouration
Biodegradable plasticisers	Flexible, softer, and easier to break down
Bio-batch additives	Oxy-degradable, photo, hydro. Years or months. High volume single use.
Why natural wood bad	Weak wet. Burns. Fungi, insect, rot. Anisotropic - diff properties in diff directions
Wood preservatives	Copper based - fungicide Impregnated with polysaccharide - hard, tough, stable. Can be pigmented to make softwoods look hard.
Board size	1220 x 2440
How to improve wood	Engineered wood Often compressed with a resin - less temp and humidity changing and uniform strength. Impregnated with fire retardant. Veneered. SCL (structural composite lumber) and LVL (laminated veneer). Veneers/strands layered into billet
Work hardening	Cold worked. Crystals distorted. Strong and hard in worked area. Less free metal crystal movement: less ductile, cracking, damage. Can be reversed via annealing.
Annealing	Less brittle more ductile. Heated then v slowly cooled so crystals grow and slowly move back into place. In industry temp-controlled furnace used. Brazing hearth in school.
Case hardening	Surface of steels less than 0.4 carbon. Outer casing harder and resist indenting while inner core has softer properties. Better wear resistance. Carburised (heated to 900+C in carbon filled box or dipped) then water quenched at 750C - seals case
Hardening	Medium and high carbon steel. Hold at high temp then quench in water, oil, or salt water. Harder but brittle. Have large internal stresses afterwards. Often much harder than required and too brittle for many practical uses
Tempering	Heat treatment for medium and high C steels after hardening to reduce excess hardness and toughen. More ductility and less brittle. Heated to below the critical point (when carbon and steel atoms mix freely) for a given time then slowly air cooled.
Tempering temperatures	Exact temps determines hardness removed

Created by: Pyrogearos2

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