POM: Materials from Biomass Flashcards
Why is it important to seek alternative sources of compounds presently obtained from the petrochemical industry?
- Petrochemicals are non renewable resources. Alternative sources are needed to meet future energy and material needs.
- Non biodegradable, and thus build up and lead to major disposal problems and mass strain on landfills
- Burn uncleanly, releasing harmful pollutants into the atmosphere such as carbon dioxide and sulfur dioxide. –> Contributes to the greenhouse effect and acid rain.
What is a condensation polymer?
One that forms by the elimination of a small molecule (often water) when pairs of monomers join together
Why is cellulose important?
Cellulose contains of 6C glucose units so it contains the basic carbon-chain structures needed to build petrochemicals.
It is renewable, readily available amounts and can be converted to petrochemicals, reducing our reliance on petroleum
Cellulose can be an alternative source of ethene instead of petroleum:
- Catalytic hydrolysis of cellulose to glucose
- Glucose to ethanol by fermentation
- Separation of ethanol from water by distillation
- Ethanol dehydrated to produce ethene
Describe the structure of cellulose
- Cellulose is a major component of biomass, which is a renewable resource.
- Cellulose is a bioolymer formed by the monomer glucose
- Cellulose is a long condensation polymer containing thousands of glucose units
- Cellulose is flat, straight and rigid due to the bulky CH2OH groups on either side.
- It is insoluble in water due to the reduced availability of OH groups due to their involvement in hydrogen bonding between chains.
Describe the reaction involved when a condensation polymer is formed
The functional groups of the two monomers react, forming a new bond and releasing water.
WHat is Polyhydroxybutyrate (PHB) monomer?
3-hydroxybutanoic acid.
How is PHB synthesised and identify the organism required for synthesis.
Organism Used: Alcaligenes eutrophus
- Bacteria grown in tanks with a carbon-based food source, high in valeric acid.
- Environment is changed because unnatural environment induces the production of the polymer by the bacterium. This is as the polymer is a natural fat storage material, created by the A Eutrophus in adverse conditions
- Large amounts of a chlorinated hydrocarbon, are added to the bacteria/polymer mix. This dissolves the polymer
- The mixture is then filtered to remove the bacteria
- The polymer is extracted from the hydrocarbon solvent as a powder, which is then melted or treated further to create a usable polymer
What are PHB’s uses in relation to it’s properties?
Naturally occurring – Non toxic and renewable, offering an eco friendly alternative to most plastics
Biodegradable – decomposes into CO2 and H2O and is used in disposable nappies and packing (bags, bottles, wrapping film), particularly for medical supplies (decomposes naturally and no surgery is needed to remove them).
Physically similar to polypropylene – Used as a substitute in many of its applications. It is stiff, has high tensile strength, highly crystalline, high melting point, low molecular weight, water insoluble, oxygen permeable and UV resistant.
Biocompatible –Compatible with biological systems (not rejected by the body’s immune system) and is therefore used in medical applications (e.g. surgical stitches and tissue scaffolding)
Evaluation of PHB?
Although the development of genetic engineering techniques has been remarkable, the costs of production of biopolymers such as PHB are still too high to make the process economically viable. This was most noticeable by the initiation and subsequent termination of the production of PHB shampoo bottles and razor handles.
It is also very brittle without additives, which makes it even more expensive to produce.
Despite this, applications within the medical industry have been comparatively successful, as the non- toxic and biodegradable nature of PHB removes the need for follow-up surgeries to remove medical sutures, as they decompose over time.
