Description
Polymer products are driving innovation and research around the world and are predicted to expand further to replace traditional engineering materials in a wide variety of applications. Students will be made aware of the wide range of polymer materials at their disposal and the opportunity for using the new grades that are being developed on a daily basis.
This unit will provide students with an understanding of the relationship between a polymer’s structure and properties and between processing technique and product performance. The ability to determine a polymer’s properties is crucial and this unit will include a review and practical application of the main testing techniques. One of the most important skills for a manufacturing engineer is the ability to distinguish between different types of polymers. This will be developed during practical sessions that will provide students with the opportunity to carry out preliminary investigations and simple identification tests. This will be supported by an overview of the main types of polymer materials.
Inadequate consideration of a specific behavioural requirement can lead to product failure and reduced service life. This will be addressed by providing techniques for material modification and learning how to use data sources for material selection. In addition this unit will consider environmental concerns and offer solutions to reduce waste and improve sustainability.
Learning Outcomes
By the end of this unit students will be able to:
1. Examine how the fundamental aspects of the molecular structure and morphology of polymers affect their processing and performance properties
Introduction
polymer concept
definition of the main terms, e.g. monomer, repeating units
classification of polymers (natural, synthetic, organic, inorganic)
Molecular Structure
structure of polyethylene chain
chain length and molar mass;
molar mass distribution;
calculations of number (average molar mass and weight-average molar mass)
significance of molar mass to processing and performance properties of
polymers
configuration of the chain molecule
confirmation of the chain molecule
secondary bonds between chain molecules
cohesion
adhesion
solubility
compatibility of polymer blends
Polymer morphology
aggregational states of matter
amorphous solid state
amorphous polymers
glass transition temperature and its significance to processing and service life crystalline polymers
melting temperature, conditions for crystallinity, effect of processing on crystallinity, morphological features (lamellae and spherulites)
2. Distinguish between the main types of polymer materials to inform the selection of a polymer material for a given application
Commodity and engineering thermoplastics
e.g. polyethylenes
modified polyethylenes; polypropylene
polyamides and aramids (overview of structure, properties and processability)
Thermosets
e.g. epoxies
phenolics; polyesthers
material storage
concept of gel-point
quantitative analysis i of cross-linking (overview of structure, properties and processability)
Rubber and elastomers
e.g. natural rubber (NR)
acrylonitlile butadiene rubber (NBR); styrene butadiene rubber (SBR), butyl rubber (BR), polychloroprene rubber (CR), ethylene propylene rubber (EPR)
introduction to vulcanisation and compounding
overview of structure, properties and processability
Introduction to simple identification tests and techniques
e.g. density, solubility
3. Determine how to select, modify, compound or adapt polymer material systems for a specific engineering application
Criteria for material selection
definitions of material properties and characteristics
material selection flow chart
overview of selection methods e.g. structured and unstructured data; material selection charts
Material testing to determine the properties of polymers
mechanical e.g. tensile, flexural, impact
optical (colour)
electrical (conductivity/resistivity)
thermal (melting temperature, glass transition temperature)
rheological
Data sources
published data e.g. British standards, ISO, material’s data sheet, IT sources,
standard published data sources, manufacturers’ literature
assessment of data reliability
Polymer modification
review of polymer additives and their functions
consideration of their cost and quantity in a compound formulation e.g. fillers, plasticisers, stabilisers, flame retardants, blowing agents, colourants, cross-linking and vulcanising agents
4. Recognise the limitations of polymer behaviour and potential solutions to environmental concerns associated with polymers
Premature failure of polymer products
causes of failure in polymer products e.g. visco-elastic and time-dependent behaviour of polymers, brittle and ductile failure, impact failure, creep rupture and fatigue failure, environmental effects
contributory effects of service conditions to failure e.g. faults in design and manufacture, inappropriate use, changes to service conditions such as load, time, temperature and environment
Solutions to environmental concerns
overview of relevant Government policies and Directives
acceptable waste management and disposal techniques e.g. re-use, mechanical recycling of single and mixed polymers
feedstock recycling to produce monomers, oligomers and chemical raw materials energy recovery
re-processing of polymers and its effect on processing and mechanical properties stabilisation of polymers to prevent weathering, chemical and thermal degradation