Carbohydrate polymers with a pinch of salt
The use of salt-modified starch as a binder could assist the production of compostable carbohydrate-based polymers with varied properties, say researchers at Leicester University in the UK.
According to the team, ‘standard enzyme tests’ have shown the material to be fully compostable industrially and at home in one to two months.
To achieve a desired ‘low carbon footprint’ polymer material, the team combined sodium chloride with a polar molecule to ‘unzip’ the starch and turn it into an amorphous, rather than a crystalline material. Hydrogen bond donors and quaternary ammonium salts are then used to modify the polymer.
Lead Researcher Professor Andy Abbott explains, ‘Salts are ideal for the purpose of modifying carbohydrates because they interact strongly with the hydroxyl groups on the glucose sub-units to decrease inter-chain interactions and better plasticise the polymer. They can also act to wet the surface of the individual grains and bind them together.’
Abbott also says the biodegradability of the polymer is assisted by biodegradable binders such as glycerol and urea, in addition to salts that occur naturally.
The material can be easily compression moulded due to its starch formulation, say researchers.
However, although at demonstrator stage, water sensitivity is an area that needs to be addressed, and spray coatings made of paraffin lanolin and beeswax are among those being tested to increase the shelf life of the polymer. Comparison tests with existing polymer materials are also still to be completed.
Polymer specialist Stuart Patrick says, ‘This approach appears to have generated some promising results. However, there are still further investigations to be carried out, which should include processability range, and stability and lifecycle analysis.
The lifecycle of the polymer and material performance comparisons to PLA are currently being assessed.
The next phase will test the composition of the material to achieve a more rigid plate, and the University aims to correlate composition and processing parameters with mechanical properties and seek reinforcing agents.
Packaging Professional Magazine, 14 Jul 2010
According to the team, ‘standard enzyme tests’ have shown the material to be fully compostable industrially and at home in one to two months.
To achieve a desired ‘low carbon footprint’ polymer material, the team combined sodium chloride with a polar molecule to ‘unzip’ the starch and turn it into an amorphous, rather than a crystalline material. Hydrogen bond donors and quaternary ammonium salts are then used to modify the polymer.
Lead Researcher Professor Andy Abbott explains, ‘Salts are ideal for the purpose of modifying carbohydrates because they interact strongly with the hydroxyl groups on the glucose sub-units to decrease inter-chain interactions and better plasticise the polymer. They can also act to wet the surface of the individual grains and bind them together.’
Abbott also says the biodegradability of the polymer is assisted by biodegradable binders such as glycerol and urea, in addition to salts that occur naturally.
The material can be easily compression moulded due to its starch formulation, say researchers.
However, although at demonstrator stage, water sensitivity is an area that needs to be addressed, and spray coatings made of paraffin lanolin and beeswax are among those being tested to increase the shelf life of the polymer. Comparison tests with existing polymer materials are also still to be completed.
Polymer specialist Stuart Patrick says, ‘This approach appears to have generated some promising results. However, there are still further investigations to be carried out, which should include processability range, and stability and lifecycle analysis.
The lifecycle of the polymer and material performance comparisons to PLA are currently being assessed.
The next phase will test the composition of the material to achieve a more rigid plate, and the University aims to correlate composition and processing parameters with mechanical properties and seek reinforcing agents.
Packaging Professional Magazine, 14 Jul 2010
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