Transparent Thermoplastic Starch Films With High TPS Content
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Solution Overview
Problem
Existing thermoplastic starch (TPS) compositions are inherently brittle, hydrophilic, and exhibit poor compatibility with hydrophobic polymers, leading to mechanical weaknesses, opacity, and reduced transparency in films, limiting their use to less than 30-40 wt.% in compounds and films, which is undesirable for sustainable packaging applications.
Innovation Solution
A process involving the addition of alpha-hydroxycarboxylic acid, such as lactic acid, and an additional heating step to 100-140 °C for 15-60 minutes, combined with a thermoplastic polymer, enhances the compatibility and transparency of TPS-based films by improving intermolecular interactions and reducing opacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thermoplastic starch content is increased in polymer formulations, then bio-based content and biodegradability are improved, but mechanical strength and compatibility with hydrophobic polymers deteriorate
Solution Approach 1:
The patent introduces silane-modified starch as an intermediary substance that bridges the hydrophilic starch and hydrophobic polymer phases. The silane modification creates amphiphilic characteristics, allowing the starch to interact with both polar and non-polar components, thereby improving interfacial adhesion and overall mechanical strength while maintaining high starch content
Solution Approach 2:
The patent modifies the chemical parameters of starch through silane grafting, transforming native starch into silane-modified starch with altered surface properties. This parameter change enables better compatibility with hydrophobic polymers and improves mechanical properties even at high starch loadings of 65-80 wt%
2Illumination intensity
If thermoplastic starch content is increased in films, then transparency is improved, but mechanical weaknesses and opacity increase
Solution Approach 1:
Silane-modified starch acts as an intermediary that improves interfacial bonding between starch granules and polymer matrix, preventing mechanical weaknesses that typically arise at high starch concentrations. The modification maintains optical clarity while providing mechanical reinforcement through improved interfacial adhesion
Solution Approach 2:
The patent creates a composite material system where silane-modified starch and hydrophobic polymer work synergistically. The composite structure leverages the transparency and biodegradability of starch with the mechanical strength and processability of the polymer, achieving both optical and mechanical performance
3Reliability
If thermoplastic starch is used in hydrophobic polymer matrices, then biodegradability is improved, but compatibility and dispersion quality deteriorate
Solution Approach 1:
Silane modification creates an intermediary substance with amphiphilic properties that mediates between hydrophilic starch and hydrophobic polymer. The modified starch maintains its biodegradability while gaining improved compatibility and uniform dispersion in the polymer matrix through enhanced interfacial interactions
Solution Approach 2:
The silane modification locally alters the surface properties of starch granules without changing their bulk biodegradable nature. This local quality change enables better interfacial compatibility while preserving the overall biodegradability of the composite material
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
This method allows for the production of transparent films with up to 65 wt.% TPS content, improving mechanical properties and moisture resistance, while maintaining transparency comparable to starch-free polymers.
Implementation Method 1
The use of plasticizers such as glycerin, sorbitol, erythritol, polyethylene glycol, various mono- and disaccharides, or sugar alcohols reduces intermolecular interactions by breaking the hydrogen bonds between the starch molecules
Implementation Method 2
an additional heating step to 100-140 °C for 15-60 minutes
Implementation Method 3
A process involving the addition of alpha-hydroxycarboxylic acid, such as lactic acid, and an additional heating step to 100-140 °C for 15-60 minutes, combined with a thermoplastic polymer, enhances the compatibility and transparency of TPS-based films
Implementation Method 4
The use of finely dispersed TPS (dispersed phase) in a polymer matrix (continuous phase), on the other hand, offers the possibility of a) significantly increasing the bio-based content in plastic formulations and b) integrating a biodegradable component
Data Source
Figure 1
AI summary
The invention relates to a method for producing a compound or a film containing thermoplastic starch, an alpha-hydroxycarboxylic acid ROHCOOH, in which R is CH2 or CH3CH2, in an amount of from 0.1 to 5, preferably 0.1 to 3, particularly preferably 0.1 to 1 wt.% in relation to the thermoplastic starch, and a thermoplastic polymer, in which method the compound or the film is exposed during or after its extrusion to an additional heating step to 100-140°C. A thermoplastic starch usable for the production of the compound, a compound produced by the method, and a transparent film produced from such a compound are also described.