Thermoplastic Starch Biodegradable Packaging via Nitrocellulose Coating
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Solution Overview
Problem
Thermoplastic starch (TPS) suffers from poor mechanical properties, high hydrophilicity, and rapid aging due to retrogradation, making it unsuitable for food packaging applications, and existing waterproofing methods do not adequately address safety and regulatory compliance for food contact materials.
Innovation Solution
Chemical modification of TPS with organic acids and the addition of sodium alginate, carboxymethyl cellulose, and microcrystalline cellulose to reduce retrogradation, combined with a nitrocellulose coating to enhance water resistance and biodegradability, ensuring compliance with food contact regulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermoplastic starch is used for food packaging, then biodegradability and low cost are achieved, but mechanical properties and water resistance are poor
Solution Approach 1:
The patent combines thermoplastic starch with poly(lactic acid) (PLA) and applies a nitrocellulose coating to create a composite material system. The PLA matrix provides structural strength while the nitrocellulose coating layer provides water resistance, allowing the biodegradable starch component to maintain its eco-friendly properties without compromising mechanical performance
2Reliability
If thermoplastic starch is used for food packaging, then biodegradability is achieved, but water resistance is poor
Solution Approach 1:
The patent applies a thin nitrocellulose coating film on the surface of the thermoplastic starch product. This coating layer acts as a flexible barrier that provides water resistance while maintaining the underlying biodegradable starch structure intact, allowing the product to resist water penetration without sacrificing its biodegradable core
3Ease of manufacture
If starch is gelatinized and cooled, then processing is enabled, but retrogradation occurs causing aging
Solution Approach 1:
The patent uses poly(lactic acid) (PLA) as an intermediary material that interacts with the gelatinized starch during processing. The PLA acts as a barrier that prevents starch chains from re-aligning and forming crystalline structures during storage, thereby inhibiting retrogradation while allowing the starch to be processed through gelatinization
4Object-affected harmful factors
If hydrophilic character of TPS is reduced, then water resistance improves, but compatibility with food contact safety may be affected
Solution Approach 1:
The patent changes the surface properties of the thermoplastic starch by applying a nitrocellulose coating, which alters the hydrophilicity parameter of the surface. The nitrocellulose coating provides water resistance through its hydrophobic character while the coating system is designed to meet food contact safety regulations, thus improving water resistance without compromising food safety
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified TPS exhibits improved stability, mechanical properties, and reduced retrogradation, with nitrocellulose coating providing superior water resistance and compliance with food contact regulations, ensuring safety and eco-friendliness.
Implementation Method 1
Chemical modification of TPS with organic acids
Implementation Method 2
additives like some polysaccharides e.g. agar, guar gum, sodium alginate and carboxymethyl cellulose... to prevent the retrogradation of TPS
Implementation Method 3
nitrocellulose coating to enhance water resistance
Implementation Method 4
destroying the hydrogen bonding network between the starch granules when it is processed in the presence of plasticizers at elevated temperatures
Implementation Method 5
When starch granules are heated in the presence of water above a certain temperature, they undergo an order-disorder phase transition called gelatinization
Data Source
AI summary
The invention relates to a method for producing a biodegradable thermoplastic starch-based article intended to come into contact with foodstuffs. In this method, the semi-crystalline starch granules are transformed into a homogeneous and almost amorphous material, called thermoplastic starch, by the addition of plasticizers at high temperatures and under shear. Thermoplastic starch is modified with organic acid during melt processing to prevent the retrogradation of starch. Moreover, cellulose derivatives are used as the reinforcement filler of thermoplastic starch. The article is produced using hot-pressing and then coating by immersion in a waterproofing solution.