Unit 7 Working With Polymers Flashcards
What are the scales of production associated with plastic products?
Polymers are used at all scales of production.
What production methods are commonly associated with plastic products?
Mass and continuous production methods.
What is one-off production?
One-off production involves crafts people and artists creating handmade, bespoke products such as sculptures and furniture.
What are the characteristics of one-off production?
One-off production is usually time-consuming, requires a high level of skill, and is typically expensive to produce.
What materials are commonly used in one-off production?
Resins are commonly used for their decorative qualities.
What is batch production?
Batch production is a broad term for production runs of anything from ten to tens of thousands of products.
What is vital for consistency in batch production?
jigs, templates, and patterns
How does the mechanisation of batch production compare to one-off production?
Processes are more highly mechanised than in one-off production.
What are some examples of products that are often batch produced?
Moulded furniture and toys are often batch produced.
Why is batch production ideally suited to the production of some packaging products?
the efficiency and consistency benefits
What are jigs used for in manufacturing?
aid manufacture and speed up repeat processes, increased accuracy
How do jigs assist in line bending?
help make accurate angles
What is one use of a jig with polymer sheets?
help fold a polymer sheet and ensure that folds run perpendicular to the edges of the sheet.
How do jigs assist with drilling?
help with positioning and dimensioning
How does the use of jigs increase efficiency in batch production?
providing consistent and accurate setups for repetitive tasks.
What are patterns in resin casting?
positive forms used in resin casting to produce negative moulds.
What is the purpose of moulds in resin casting?
enable identical copies
What materials can patterns be made from?
clay, wood, and silicone rubber.
What are patterns usually sprayed with before they are cast?
a release agent
What factors influence the materials used for moulds?
how many times the mould will be used and what is being cast or moulded.
What materials can be used to make moulds?
Plaster of Paris, silicon rubber, latex, and GRP.
What materials are commonly used for moulds in school vacuum forming?
from wood, MDF, and Styrofoam.
What is the common material for industrial moulds?
tool steel.
What advantage does tool steel provide for moulds?
durability and longevity
What is mass production?
production line to produce high numbers of identical products quickly.
How does mass production compare to batch production?
It is more highly automated than batch production and requires less skilled labour.
What are common products that are mass produced?
food packaging, plastic bags, and cups
How are materials for mass production typically purchased?
generally purchased in bulk.
What is a drawback of mass production?
Set-up costs are high
What is continuous production?
Continuous production is similar to mass production using a production line to manufacture quantity.
What is a characteristic of continuous production?
Only one product is made with very few, if any alterations.
What is a key feature of continuous production?
there is no downtime
What types of products are ideal for continuous production?
HDPE milk bottles, PET drinks bottles, and film used for refuse sacks and other plastic bags.
Why is continuous production suitable for certain products?
products with high demand and the efficiency of the production process.
What is calendaring?
Calendaring is a production process using a series of rollers to produce a thin polymer sheet or film.
What happens to polymer pellets during calendaring?
Polymer pellets are heated and softened.
What is done with the softened polymer feedstock in the calendaring process?
The softened polymer feedstock is extruded through a series of heated rollers.
What effect do the heated rollers have on the polymer?
The rollers flatten and stretch the polymer.
What happens to the polymer sheet after it is processed by the final rollers?
The final rollers cool the sheet, and it is either rolled or cut to length.
What is calendared plastic sheet or film used to manufacture?
Calendared plastic sheet or film
What is extrusion?
used to create a continuous flow of plastic that is pushed through a die to create a specific profile.
What products are created using extrusion?
cables, pipes, mouldings, tubes, seals, and window and door frames.
What types of plastic products are made using extrusion?
plastic film used for bags and packaging, as well as the plastic filament used for 3D printing.
Is much waste produced during the extrusion process?
Yes, much waste is produced during the extrusion process.
What is the starting point of the extrusion process?
using a die instead of a mould.
What does the die do in the extrusion process?
The die sets the profile of the extruded plastic and must be made to a very precise tolerance.
What is required for the flow of softened plastic during extrusion?
flow rate to hold
What is the form of polymers before processing?
powder or granule form are processed to produce usable stock forms for manufacture.
What factors influence the formation of polymers?
manufacturing location, product type, production scale, and polymer material used.
Where can polymers be manufactured?
in a school workshop or in an industrial facility.
What aspects determine the method of forming polymers?
the product or part being formed, the scale of production, and the type of polymer material.
What methods of forming are commonly used in school workshops?
The text does not specify the methods, but it implies that there are common methods used in school workshops.
What is vacuum forming?
process used to create products by shaping plastic sheets over a mold eg plastic yoghurt pots and bath tubs.
What is the most commonly used plastic for vacuum forming in schools?
HIPS (high impact polystyrene)
What other materials are used for vacuum forming in industry?
, polyester, ABS, and acrylic.
Why is vacuum forming suited for use in the school workshop?
its simplicity and the availability of materials like HIPS.
What is the first stage of the vacuum forming process?
A sheet of thermoplastic is heated and pressed onto the former (mould) by atmospheric pressure as a vacuum reduces the pressure below the softened thermoplastic.
What happens to the plastic during the vacuum forming process?
takes on the shape of the mould, then cools and sets in position before the mould is removed.
What is the role of the electric heater in the vacuum forming process?
The electric heater is turned on to warm the plastic sheet.
What occurs to the air during the vacuum forming process?
The air is pumped out below the plastic and mould.
What features must a mould have to ensure a good product is formed?
A mould must have rounded corners and edges with a small radius.
What is the required positive draft angle for a mould?
A mould must have a positive draft angle greater than 3° to ensure easy removal.
What should be avoided regarding the profile depth of a mould?
A mould must not have too deep a profile.
Deep profiles can complicate the moulding process and lead to defects.
What finish should a mould have?
A mould must have a smooth finish.
A smooth finish reduces friction and improves the quality of the final product.
What feature should a mould avoid to ensure product quality?
A mould must avoid undercuts.
Undercuts can make it difficult to remove the product from the mould.
What is line bending?
creating a permanent fold in a piece of thermoplastic such as acrylic.
What equipment is used for line bending?
Strip heaters.
What types of products are often created using line bending?
small products in the school workshop.
What are some examples of products made using line bending?
display stands, menu holders, and photo frames.
What should be done before placing the polymer sheet on the strip heater?
Marking out should be done carefully and accurately.
How is the line marked on the polymer sheet?
using a chinagraph pencil or non-permanent marker.
What is the first step in the line bending process?
The strip heater is heated to temperature.
What is done with the marked line on the workpiece?
placed across the heating strip.
What should be considered when using a strip heater in the workshop?
Health and safety considerations.
What factors influence the heating time of a polymer sheet in the line bending process?
The type and thickness of the polymer sheet.
How is the flexibility of the line tested in the line bending process?
The line is tested for flexibility and when ready, bent to the required angle.
What is done to the workpiece after it has set in the line bending process?
It can be cooled in a water tray.
What can be made to help ensure the polymer sheet is bent accurately?
A jig or template
What factors influence the heating time of a polymer sheet in the line bending process?
The type and thickness of the polymer sheet.
None
What is done to the polymer sheet during the line bending process?
The polymer sheet is allowed to heat through.
None
How is the flexibility of the line tested in the line bending process?
The line is tested for flexibility and when ready, bent to the required angle.
None
What is done to the workpiece after it has set in the line bending process?
It can be cooled in a water tray.
None
What can be made to help ensure the polymer sheet is bent accurately?
A jig or template can be used to ensure accuracy.
None
What can thermosetting polymer resins be combined with?
Thermosetting polymer resins can be combined with fibres to produce a variety of products.
What types of products can be created using laminating or layup?
This process is used to create rigid three-dimensional products like speed boats, rowing boats, canoes, caravan panels, and even bumper cars.
What is the advantage of a fibre-based composite over a moulded thermoplastic?
The advantage of a fibre-based composite over a moulded thermoplastic is not specified in the text.
What materials are used to create composites in the layup process?
Fibre strands or matting, such as glass fibre, carbon fibre, or Kevlar.
What materials can be used to make the mould in the layup process?
Timber, board, or metal.
What is applied to the mould before the layup process?
A release agent.
What is applied and cured on the mould in the layup process?
Polyester resin gel coat.
What is done after matting is laid into the mould?
The resin is mixed with a catalyst and brushed onto the matting.
How may chopped strands be applied in the industry?
They may be mixed with resin and sprayed onto the mould.
What is done to remove air bubbles after applying the resin?
The mixture is rolled to remove air bubbles and then allowed to set.
What is thermoforming?
Thermoforming is the process of forming a heated, softened polymer sheet.
How does thermoforming differ from vacuum forming?
Thermoforming uses both male and female moulds, while vacuum forming typically uses only one mould.
What is the role of the male mould in thermoforming?
The male mould is lowered into the heated sheet, pressing it into the female mould.
What assists in pulling the polymer into the mould during thermoforming?
A vacuum assists in pulling the polymer into the mould.
What types of products can be manufactured using thermoforming?
Various packaging products can be manufactured using thermoforming.
What is injection moulding?
Injection moulding is commonly used in industrial production to produce complex shapes.
What are moulds generally constructed from in injection moulding?
Moulds are generally constructed from steel and are in two parts.
Which polymers are suitable for injection moulding?
A number of different polymers are suitable for injection moulding and include ABS, acrylic, and PVC.
Why is it important that moulds are very accurate?
It is important that moulds are very accurate and any blemishes are removed to ensure quality in the final product.
What starts the injection moulding process?
The injection moulding process starts with the thermoplastic granules being fed into a hopper.
What does the hopper do in the injection moulding process?
The hopper feeds an Archimedes screw that drags the granules past a heater where they are plasticised.
What happens when the plastic reaches the end of the screw?
A hydraulic piston forces it into the mould.
What is the role of the Archimedes screw in the injection moulding process?
The Archimedes screw drags the granules past a heater for plasticisation.
What is used to cool and set the plastic quickly in the ejection and finishing process?
Water is used to cool and set the plastic quickly.
What happens after the mould is separated in the ejection process?
Ejector pins release the moulding; the process is then repeated.
What is done with any excess polymer flashing?
Any excess polymer flashing is trimmed and usually recycled.
How does injection moulding lend itself to mass production?
Injection moulding is efficient and allows for rapid production of identical items.
What are the tell-tale signs that a product has been injection moulded?
Signs include visible seams, uniformity in shape, and the presence of ejector pin marks.
What is blow moulding?
Blow moulding uses a two-part mould and compressed air to make hollow shapes.
What types of polymers are used in blow moulding?
Polymers like HDPE, PET, PP, and LDPE are used.
What products are made using blow moulding?
Hollow plastic products including garden water butts, bins, and some hollow plastic toys.
What packaging is created through blow moulding?
It is used to create packaging such as bottles and containers.
Why is a two-part mould used in blow moulding?
A two-part mould is essential for shaping the hollow structures.
What is the first step in the blow moulding process?
Polymer granules are heated and extruded to create a plastic tube known as a parison.
What happens after the parison is created?
The parison is fed into the mould and is pinched at the bottom as the mould closes tightly.
How is the parison inflated to fill the mould?
It is filled with heated compressed air until the parison inflates to fill the mould.
What occurs after the parison fills the mould?
The plastic cools and takes on the shape of the mould.
What happens to the cooled moulding in blow moulding?
The cooled moulding is then released and finished.
What is done with excess or flashing created during blow moulding?
Any excess or flashing created is automatically trimmed.
What happens to the waste material from blow moulding?
This waste material is recycled and reused.
How are products tested after blow moulding?
Products are tested to ensure they are air and water tight.
What happens to rejected products in blow moulding?
Any rejects are sent for recycling.
What is a common feature of high production moulds?
High production moulds are often water cooled.
How does water cooling contribute to blow moulding?
Water cooling contributes to the efficiency of the process.
What is rotational moulding used for?
Rotational moulding is used to create hollow plastic forms.
What types of polymers are commonly used in rotational moulding?
Polymers like HDPE and PP are commonly used.
What is a key characteristic of products made by rotational moulding?
The process produces a seamless product.
What are some examples of heavy duty items made using rotational moulding?
Examples include water tanks, communal recycling bins, kayaks, and plastic slides.
Why isn’t blow moulding used to create heavy duty items?
Blow moulding is not suitable for these products due to their design and structural requirements.
What is the first step in the rotational moulding process?
Polymer granules or powder is weighed, depending on the desired wall thickness and put into the mould.
What happens to the mould after the polymer is added?
The mould is then placed on a rig in a huge oven and heated.
How is the polymer distributed inside the mould?
As it is heated, the mould is rotated slowly in two axes, allowing the polymer to coat the inside of the mould evenly.
What occurs once the desired thickness is reached?
The mould is cooled.
What is a consequence of cooling the polymer?
There is slight shrinkage as the polymer cools.
What is the advantage of the slight shrinkage of the polymer?
The slight shrinkage helps in the easy removal of the finished product from the mould.
What is the compression process in polymer forming?
The compression process uses two separate moulds, a male and female, which when pressed together create a void.
What is placed between the moulds during the compression process?
A charge or preform of polymer is placed between the moulds.
What happens to the moulds during the compression process?
The moulds are heated, and pressure is exerted on them, forcing the charge into the void.
What occurs after the polymer part is formed in the mould?
The part is left to cool before being removed using an ejector pin.
Why is the amount of polymer used slightly greater than needed?
The amount of polymer used is slightly greater than that needed to fill the void to ensure complete filling.
What does it mean for most plastics to be self-finishing?
It means they do not require any further finishing and are ready to go straight from production.
How is the texture of polymers determined?
The texture comes from the surface finish of the moulds used to form them or the die profiles used when extruding.
Why are polymers often considered to be self-colouring?
This is related to their ability to maintain color without additional finishing processes.
What are thermochromic pigments?
Thermochromic pigments can be added to polymers to create a colourful reaction to thermal changes.
How do temperature sensitive thermochromic pigments react?
They can change from one colour to another or from colour to clear as temperature rises and falls.
What are some applications of thermochromic pigments?
Applications include plastic cutlery, bowls, and cups for babies and young children, and plastic films used in thermometers.
Where might non-reversible thermochromic pigments be used?
Non-reversible thermochromic pigments can be used in various applications where a permanent colour change is desired.
What are phosphorescent pigments?
Phosphorescent pigments are charged by exposure to natural light.
How do phosphorescent pigments work?
The phosphors in the pigment release the energy they have stored while exposed, producing a visible glow in the dark.
What are some applications of phosphorescent pigments?
Applications include watches, toys, and recreational items like frisbees, balls, wall decals, and ceiling stars.
How can phosphorescent pigments improve product function or safety?
Suggest products where phosphorescent pigments are used to improve the function or even increase the safety of the product.
What is hydrographic printing?
Hydrographic printing is a process where colour images are printed onto water soluble film that floats in a tank.
How does hydrographic printing work?
The product is submerged in the tank, and the image wraps around it, giving a colourful and potentially dramatic finish.
What is the main benefit of hydrographic printing?
It provides a colourful and potentially dramatic finish to products.
What is electroplating?
Electroplating is the process of covering plastics in a conductive layer or etching them before plating with a metal.
In which industries is electroplating predominantly used?
Electroplating is predominantly used in the automotive industry for car trims, as well as in electronics, bathroom fixtures, and various household goods.
What benefits does electroplating have?
Electroplating provides enhanced durability, corrosion resistance, and improved aesthetic appearance.
What is electroplating?
Electroplating is the process of covering plastics in a conductive layer or etching them before plating with a metal.
In which industries is electroplating predominantly used?
Electroplating is predominantly used in the automotive industry for car trims, as well as in electronics, bathroom fixtures, and various household goods.
What benefits does electroplating have?
Electroplating provides enhanced durability, corrosion resistance, and improved aesthetic appearance.
What is rubberising spray?
A slightly textured coating with a matt finish that can be sprayed onto various materials to provide grip.
Where might rubberising sprays be used?
Rubberising sprays can be used on various materials to enhance grip.
What happens to plastic when processed?
Plastic can become rough or scratched when processed and can become weathered or faded if left outside.
What are polishing techniques used for?
Polishing techniques are used to restore a high quality finish.
What product is commonly used to polish plastics?
Brasso® is often used to give a lustrous shine to plastics and is commonly used in a school workshop.
What happens to plastic when processed?
Plastic can become rough or scratched when processed and can become weathered or faded if left outside.
What are polishing techniques used for?
Polishing techniques are used to restore a high quality finish.
What product is commonly used to polish plastics?
Brasso® is often used to give a lustrous shine to plastics and is commonly used in a school workshop.
What is a common method for joining polymers?
Solvent cements are more commonly used to form a chemical weld than heat welding.
In which industry are solvent cements commonly used?
Solvent cements are used in the plumbing industry.
What types of pipes are joined using solvent cements?
Solvent cements are used to join PVC and ABS pipes.
What happens when solvent cement is brushed on the surfaces?
The surfaces soften and permanently fuse together.
What is the process used to create rigid three-dimensional products from thermosetting polymer resins and fibres?
Laminating or layup
This process is used in various applications, including speed boats and caravan panels.
List three products that can be formed using laminating or layup with thermosetting polymer resins.
- Speed boats
- Rowing boats
- Canoes
- Caravan panels
- Bumper cars
These products benefit from the strength and rigidity provided by the composite materials.
True or False: Thermosetting polymer resins can be combined with fibres to produce flexible products.
False
Thermosetting polymer resins are used to create rigid products.
What are the two main categories for applying finishes to polymers?
The two main categories are protection and aesthetics, with some finishes offering both.
How can polymer finishes be applied?
Polymer finishes may be brushed on, sprayed on, or applied.
What is a concern with some spray-on polymer products?
Some spray-on products are solvent based and contain high levels of volatile organic compounds (VOCs), making them not very environmentally friendly.
What precautions should be taken when using solvent based products?
Precautions should be taken to ensure safety and minimize environmental impact.
What are UV hardening resins used for?
UV hardening resins have been used in dentistry for many years and have also been developed for use in 3D printers and as a separate adhesive.
How does UV hardening adhesive work?
The liquid adhesive is applied to the surfaces that require bonding and UV light is shone on it, which cures it.
What is the result of using UV hardening adhesive?
The resulting bond can be very strong and is permanent.
What is the purpose of gel coating in the layup process?
A gel coat creates a coloured finish for a rigid GRP shell.
What is added to the polyester resin during the gel coating process?
Pigment is added to the polyester resin.
Where is the gel coat applied in the moulding process?
The gel coat is applied to the inside of the mould.
What happens to the gel coat after it is applied?
It is allowed to cure hard before layup continues.
What is the result of using a gel coat?
The result is a pre-coloured high shine surface finish.
Is any additional finish required after gel coating?
Is any additional finish then required?
What are acrylic spray paints used for?
Acrylic spray paints are sometimes used to protect and colour moulded plastic parts and products.
Where are acrylic spray paints commonly used?
They are used on body coloured bumpers where ABS parts are mass produced and sprayed after production to match the vehicle.
What are the characteristics of acrylic spray paint?
Acrylic spray paint is water based and fast drying.
What benefits does acrylic spray paint provide?
It adds additional UV protection and improved weather resistance.
When does acrylic spray painting make better financial sense than adding pigments?
This question prompts consideration of the financial implications of using acrylic spray painting versus adding pigments.
What is required to achieve a good painted finish on polymers?
Preparation is required as most polymers are self finishing, smooth, and therefore not an ideal substrate for paint.
What is the first step in preparing an ABS moulding for painting?
The surface first needs to be thoroughly washed and dried.
What should be done after washing and drying the ABS moulding?
It should then be abraded to provide a key.
What must be done after abrading the ABS moulding?
It must then be cleaned again and any residual dust removed.
What is applied after cleaning the ABS moulding?
A primer is then applied and allowed to dry before applying several even coats of acrylic paint.
What is overmoulding?
Overmoulding is a process that enhances both the look and feel of a polymer-based product.
What materials are often used in overmoulding?
Thermoplastic elastomers (TPEs) are often used to create an additional grip or texture.
How does overmoulding improve ergonomics?
Overmoulding can indicate where to grasp a product, improving ergonomic design.
In which products is overmoulding commonly used?
Overmoulding is commonly used in tool handles, sports equipment, toothbrushes, torches, sports bottles, and power cables.
Why use TPEs rather than other thermoplastics?
TPEs provide enhanced grip and texture, making them preferable for certain applications.
What is required to achieve a good painted finish on polymers?
Preparation is required as most polymers are self finishing, smooth, and therefore not an ideal substrate for paint.
What is the first step in preparing an ABS moulding for painting?
The surface first needs to be thoroughly washed and dried.
What should be done after washing and drying the ABS moulding?
It should then be abraded to provide a key.
What must be done after abrading the ABS moulding?
It must then be cleaned again and any residual dust removed.
What is applied after cleaning the ABS moulding?
A primer is then applied and allowed to dry before applying several even coats of acrylic paint.
What are overmoulded products usually made through?
Overmoulded products are usually injection moulded.
What is one method for creating overmoulded products?
Two separate moulds can be used, one for the substrate and a second with a cavity for the overmoulding.
What is another method for creating overmoulded products?
A single, dual cavity mould with two separate injection heads can be used in a continuous production line.
What is the term for the method using a dual cavity mould?
This method is called twin shot injection moulding.
