Bio-based and biodegradable resins.
PowerPoint
papers
Index
| Composites Design and Manufacture (Plymouth University teaching support materials) Bio-based and biodegradable resins. |
Lecture PowerPoint |
Review papers |
Subject Index |
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CAUTION: For the purpose of the Sustainable Composites pages, the materials described are those from natural sources, without prejudice to the results of any future Quantitative Life Cycle Analysis (QLCA) which may (or may not) make the case for these materials being more environmentally-friendly than equivalent systems manufactured from man-made fibres and synthetic resins. The inclusion of any specific system here is not an endorsement of that product: potential users will need to fully consider each system in the context of their specific technical requirements.
The value of Eco-System Services
Reddy et al [1] have presented a series of definitions pertinent to "bio-plastics", as follows:
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InnProBio (the Forum for Bio-Based Innovation in Public Procurement) have published a series of factsheets:
The Bio-Based Industries Joint Undertaking has a website with summaries of relevant funded projects. |
Olvera and Turner [3] discussed the measurement of the carbon-14 level in compoosite materials to differentiate between bio-based and fossil-based content.
Hongzhe Chen [4] has reviewed the various potential adverse impacts and hazards of biodegradable plastics (BP) on the marine environment and human society, including the release of microplastics, degradation products, additives, and other pollutants, which could entangle animals or alter the material cycles of conventional plastics before decomposition, alter microbial communities on them, and affect biogeochemical activities in the adjacent environment due to their biodegradability.
THERMOPLASTIC POLYMERS
CPLA (polylactide aliphatic copolymer) [5] is a biodegradable mixture of lactide and aliphatic polyesters. It can be either a hard plastic (similar to PS) or a soft flexible one (similar to PP) depending on the amount of aliphatic polyester present in the mixture. It is easy to process with stability up to 200 °C. Possible applications will include compost bags, cushioning materials, food wrapping materials, fishing nets, etc.
PCL (polycaprolactone) [6, 7] is a biodegradable thermoplastic polymer made by polymerizing ε-caprolactone and hence derived from the chemical synthesis of crude oil. Although not produced from renewable raw materials, it is fully biodegradable. It has good water, oil, solvent and chlorine resistance, a low melting-point (58-60 °C), low viscosity and it is easy to process. It is used mainly in thermoplastic polyurethanes, resins for surface coatings, adhesives and synthetic leather and fabrics. It also serves to make stiffeners for shoes and orthopaedic splints, and fully biodegradable compostable bags, sutures, and fibres. It is used as an additive for other resins to improve their processing characteristics and end use properties, and acts as a polymeric plasticizer with PVC. PCL is compatible with most thermosetting and thermoplastic resins and elastomers. It increases impact resistance and aids mould release of thermosets.
PGA (polyglycolicacid) is a synthetic polymer of glycolic acid (HOCH2COOH). As the monomer is terminated by a hydroxyl group at one end and a carboxyl group at the other, it can be polymerised by a condensation reaction to yield a polyester. The polymer degrades to natural metabolic waste products and finds use in biomedical applications.
PHA (polyhydroxyalkanoate) [8, 9] is a class of linear polyesters produced in nature by bacterial fermentation of sugar or lipids. More than 100 different monomers can be combined within this family to give materials with extremely different properties. They can be either thermoplastic or elastomeric materials, with melting-points ranging from 40 to 180°C. The most common type of PHA is PHB (poly-β-hydroxybutyrate). PHB has properties similar to those of PP, however it is stiffer and more brittle. More detail can be found on the AZoM site [10]. A PHB copolymer called PHBV (polyhydroxybutyrate-valerate) [8] is less stiff and tougher and finds use as packaging material. More detail can be found on the AZoM site [11].
PLA (polylactide) [12, 13] is a biodegradable thermoplastic derived from lactic acid. It resembles clear polystyrene, provides good aesthetics (gloss and clarity), but it is stiff and brittle and needs modifications for most practical applications (i.e. plasticizers increase its flexibility). It can be processed like most thermoplastics into fibres, films, thermoformed or injection moulded. It is most commonly used for compost bags, plant pots, diapers and packaging. Cargill Dow’s NatureWorks PLA [14, 15] is derived from corn. Gupta et al [16] have reviewed the use of PLA as a fibre and identified the following key data: Tg ~60-70ºC, Tm ~150-170ºC, E(fibre) = 1.2-9.3 GPa, σt'(fibre) = 42-870 MPa and εt'(fibre) = 4-440% dependent on the processing route used. Clark and Hardy [17] have compared and contrasted the sustainability implications of the life cycle of PLA with that for conventional polymers. Life Cycle Assessments exist for PLA [18, 19].
L-lactide dimer has been considered as a potential matrix system for in situ polymeriation (ISP) during monomer infusion under flexible tooling (MIFT) [20]. The monomer is hydrophilic and storage under dry nitrogen in recommended. The dry monomer should be processed at low temperatures to minimise corrosion of metal moulds and process ancillaries.
~ In-situ polymerisation for liquid composite moulding (LCM) processes
~ Review papers for Infusible thermoplastic matrix systems
DuPontTM Sorona® [21] is one member of a family of polymers based on Bio-PDO™ corn-derived chemical/1,3-propanediol: poly (trimethylene terephthalate), i.e. bio-based PTT.
There is some interest in the use of starch-based polymers as "sustainable" materials for extrusion or injection moulding. However, processing these materials is more complex than using conventional polymers and involves multiple chemical and physical reactions, including water diffusion, granule expansion, gelatinisation, decomposition, melting and crystallization. The thermal processing of these materials has been reviewed by Hongsheng Liu et al [22]. Starch-based resins can be made from corn, wheat, tapioca and potato (e.g. Cereplast Compostables® [23] and Potatopak [24]).
The UK government has run a series of projects under the LINK collaborative research scheme in Competitive Industrial Materials from Non-Food Crops (CIMNFC). Of particular relevance to natural resins is StarPlast (lead by the IRC in Polymer Science & Technology at the University of Leeds):
References
THERMOSETTING POLYMERS FROM PLANTS
For review papers on bio-based resins, follow this link.
Further reading
Suppliers of bio-based thermosetting resins.
