Biodegradable Polymer Composition Retarding Post-Crystallization
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Solution Overview
Problem
Current biodegradable polymer compositions, particularly those based on starch and polyhydroxyalkanoates, face challenges in maintaining mechanical properties due to uncontrolled post-crystallization, leading to embrittlement and reduced biobased carbon content, which is undesirable for environmental and economic reasons.
Innovation Solution
A polymer composition combining 5-50 wt% destructured starch or starch derivatives, 20-70 wt% aliphatic-aromatic copolyester, 10-50 wt% polyhydroxyalkanoate, and 3-25 wt% polylactic acid, which retards post-crystallization and maintains excellent mechanical properties even after storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the starch content is increased to raise biobased carbon content, then the ecological and economic benefits improve, but the mechanical properties deteriorate considerably
Solution Approach 1:
The patent creates a composite polymer system combining four distinct biobased polymers (starch, PHA, PLA, and aliphatic-aromatic copolyester) in specific ratios. This composite approach allows each component to contribute its strengths: starch provides biobased content, PHA provides biodegradability, PLA provides structural integrity, and the copolyester provides flexibility. The synergistic interaction between these materials enables high biobased carbon content (≥50%) while maintaining acceptable mechanical properties, resolving the contradiction between quantity of biobased material and mechanical strength.
Solution Approach 2:
The patent systematically varies the compositional parameters of the polymer blend, specifically optimizing the ratios of starch (5-50 wt%), PHA (10-50 wt%), PLA (3-25 wt%), and aliphatic-aromatic copolyester (20-70 wt%). By adjusting these parameters within defined ranges, the invention achieves a balance point where the biobased carbon content reaches at least 50% while mechanical properties remain sufficient for practical applications. This parameter optimization resolves the contradiction by finding the optimal composition window.
2Reliability
If PHA content is increased to improve biodegradability, then the biodegradation capability improves, but post-crystallization causes embrittlement and mechanical property loss
Solution Approach 1:
The patent introduces PLA and aliphatic-aromatic copolyester as intermediary materials that mediate between PHA and starch. These intermediaries serve multiple functions: they act as nucleating agents that control PHA crystallization kinetics, preventing rapid uncontrolled post-crystallization; they provide a matrix that accommodates PHA crystallites without creating excessive stress concentration points; and they maintain flexibility in the blend. This intermediary approach allows high PHA content (10-50 wt%) for biodegradability while the intermediaries suppress the harmful embrittlement effect during storage.
Solution Approach 2:
The patent optimizes the PHA content parameter within the range of 10-50 wt% and combines it with specific amounts of PLA (3-25 wt%) and aliphatic-aromatic copolyester (20-70 wt%). This parameter control ensures that PHA provides sufficient biodegradability while the other components limit post-crystallization embrittlement. The balanced composition prevents the mechanical property deterioration that occurs with higher PHA contents in conventional formulations.
3Quantity of substance
If starch and PHA content are increased to achieve high biobased content, then the renewable material content improves, but uncontrolled post-crystallization occurs leading to mechanical property deterioration
Solution Approach 1:
The aliphatic-aromatic copolyester acts as a stabilizing intermediary in the polymer blend. It provides a flexible matrix that accommodates the starch and PHA components, preventing excessive phase separation and uncontrolled crystallization. The copolyester's amorphous nature and flexibility allow it to absorb volume changes during storage without creating stress cracks or facilitating uncontrolled post-crystallization. This intermediary stabilization enables the blend to maintain its compositional integrity and mechanical properties over time, even with high renewable content.
Solution Approach 2:
The patent defines specific parameter ranges for each component to ensure compositional stability: starch (5-50 wt%), PHA (10-50 wt%), PLA (3-25 wt%), and aliphatic-aromatic copolyester (20-70 wt%). Within these ranges, the blend achieves a stable morphology where crystallization is controlled and phase separation is minimized. The parameter optimization ensures that the renewable material content reaches at least 50% while maintaining compositional stability during storage, preventing the deterioration that occurs in conventional high-starch blends.
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 polymer composition exhibits stable tensile strength, elongation at break, and impact resistance over 24 hours, allowing for higher biobased carbon content without significant mechanical property deterioration, thus addressing the limitations of existing biodegradable materials.
Implementation Method 1
the uncontrolled, slow post-crystallization of the PHA polymers following their processing into films. The spherulites forming due to the post-crystallization presumably act as defect sites in the film
Data Source
AI summary
The invention relates to a polymer compound which, based on the total weight of the polymer compound, comprises at least the following components: (a) 5 to 50 wgt.-% destructed starch and/or starch derivative, (b) 20 to 70 wgt.-% aliphatic-aromatic copolymer, (c) 10 to 50 wgt.-% polyhydroxyalkanoate and (d) 3 to 25 wgt.-% polyactic acid. Such polymer compounds are characterized by a high ratio of bio-based carbon and exhibit no significant embrittlement or worsening of the mechanical properties profile, despite the presence of increased volumes of polyhydroxyalkanoate, even after storage. The invention further relates to production methods for the polymer compound according to the invention, and use thereof in the production of films, molded parts or fibers.