Chapter 2.1 Processing of Plastics (193649)

Get Started. It's Free
or sign up with your email address
Rocket clouds
Chapter 2.1 Processing of Plastics (193649) by Mind Map: Chapter 2.1 Processing of Plastics (193649)

1. Polymer processing

1.1. Mixing

1.2. Melting

1.3. Melt flow

1.4. Cross-linking

1.5. Cooling and solidification

2. Pre-processes

2.1. Compounding

2.1.1. Preparing the preform by mixing: Basic polymer Plasticizers Fillers Colourants Others

2.1.2. Machines Banbury mixer Screw compounder Single-screw Twin-screw

2.2. Calandering

2.2.1. Process Materials are squeezed to final thickness Using heated rollers Chill roller Calendar roller

2.2.2. Advantages Wide range of surface finishes Used to laminate fabric Will produce any practical length Versatility; high rate Easier to clean than extrusion

2.2.3. Disadvantages Large and costly machines Limited product width and thickness Roller deflection must be compensated for

3. Methods of processing plastic (See Chapter 2.2)

3.1. Molding

3.1.1. Compression

3.1.2. Injection

3.1.3. Transfer

3.1.4. Rotational

3.2. Extrusion

3.2.1. Filament

3.2.2. Blow film

3.2.3. Coating & wire covering

3.3. Blow molding

3.3.1. Injection Extrusion

3.3.2. Stretch

4. Reinforcing process

4.1. Reinforcing agents added to polymers

4.2. To improve properties of composite

4.3. Ingredients

4.3.1. Resin

4.3.2. Catalyst

4.3.3. Filler

4.3.4. Short fiber reinforcement

4.4. Matched die process

4.4.1. Bulk-molding compounds Putty-like mixture Log or rope shape For compression and injection molding

4.4.2. Sheet-molding compounds Leather-like mixture Formed into sheets Process Continuous strand fiberglass is chopped Strands are deposited onto bottom layer of paste The mixture travels through machine Covered by top and bottom carrier film Made into continuous sheet

5. Testing of plastics

5.1. Mechanical properties

5.1.1. Tensile strength Stress-strain relationship Ability to withstand forces pulling it apart Specimen: dumbbell Measurement Maximum force Cross sectional area of the narrow section

5.1.2. Compressive strength Force needed to crush the material Distinguish between grades of plastics Specimen Block Cylinder Process Specimen loaded between two plates Compressed at uniform rate Load is applied to center of specimen Measurement of force per unit cross sectional area

5.1.3. Impact strength Resistance of the material against impact Tests Falling mass test Pendulum test

5.1.4. Flexural strength Load can be applied before it breaks Involves tensile and compressive stress Three point bending

5.1.5. Shear strength Maximum load need to to produce fracture Separating the movable part from the stationary

5.2. Thermal properties

5.2.1. Thermal conductivity Rate of what energy transferred among molecules Expressed as a coefficient 'k' factor

5.2.2. Specific heat Amount of heat required To raise the temperature of a unit mass by 1°C

5.2.3. Thermal expansion Expansion in: Length Area Volume Per unit temperature rise High thermal expansion unsuitable for low tolerance part

5.2.4. Deflection temperature Highest continuous operating temperature Process Specimen is placed in supports Force is placed on sample Measurement of the temperature at which the sample deflects

5.2.5. Flammability Ability to support combustion Process Plastic strip is ignited Heat source is removed Measurement Time of combustion Amount of material consumed

5.2.6. Glass transition Temperature at which plastics turn rubbery Factors affecting Tg Backbone flexibility Plasticizer Structure

5.3. Environmental properties

5.3.1. Chemical resistance Ability to resist attack from chemicals Due to types of bond in the plastic Additives affecting chemical resistance Fillers Plasticizers Stabilizers Colourants Catalysts

5.3.2. Weathering Plastics for outdoor applications Factors influencing weathering Solar radiation Temperature Humidity Pollutants Tests Exposure to Rated on Colour change Gloss change Cracks and crazing Loss of physical properties

5.3.3. Permeability Volume of gas penetrating an area of film

5.3.4. Water absorption Some plastics are hygroscopic Must be dried before heating and melting processes Tests Thermogravimetric principle Moisture specific apparatus