Renewable Polyester Fibers with Voided Structure
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Solution Overview
Problem
Renewable polyesters, such as polylactic acid, have high glass transition temperatures and low ductility, making them unsuitable for fibers that require a balance between strength and flexibility due to their high density and stiffness, which limits their market penetration.
Innovation Solution
A thermoplastic composition is developed with a rigid renewable polyester blended with a polymeric toughening additive and an interphase modifier, creating a voided structure through cold drawing below the glass transition temperature to reduce density and enhance mechanical properties, resulting in fibers with a density of 1.4 g/cm3 or less and improved tensile elongation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If gaseous blowing agents are employed to create a cellular foamed structure, then the density of renewable polyester is reduced, but the processability and tensile properties are compromised due to uncontrolled pore size and distribution
Solution Approach 1:
The patent employs a porous foamed structure created through controlled phase separation rather than gaseous blowing agents. The voids are formed by the separation of immiscible polymer phases during fiber formation, creating a controlled porous network that reduces density while maintaining structural integrity and mechanical properties.
Solution Approach 2:
The patent uses a composite system of immiscible polymer phases (e.g., polylactic acid and polyethylene glycol) that separate during processing to form a dual-phase structure. This composite approach allows the formation of controlled voids through phase separation, achieving density reduction without compromising tensile properties.
2Adaptability or versatility
If renewable polyester is used in fibers, then environmental sustainability is improved, but the high glass transition temperature and low ductility limit market penetration
Solution Approach 1:
The patent creates a composite fiber system combining renewable polyester with compatible polymers or plasticizers. This composite structure modifies the glass transition behavior and enhances ductility while maintaining the renewable and sustainable characteristics of the base polyester material.
Solution Approach 2:
The patent modifies the glass transition temperature and ductility parameters of renewable polyester through the addition of plasticizers or copolymerization. These parameter changes allow the material to achieve the flexibility and elongation required for fiber applications while preserving its renewable nature.
3Adaptability or versatility
If renewable polyester is used in fibers, then environmental sustainability is improved, but the high density makes them significantly more expensive than conventional polyolefins
Solution Approach 1:
The patent creates a porous foamed structure in renewable polyester fibers through controlled phase separation. This porous network reduces the overall density of the fiber, bringing it closer to that of conventional polyolefins and thereby reducing material costs and improving economic competitiveness.
Data Source
AI summary
Fibers that are formed from a thermoplastic composition that contains a rigid renewable polyester and has a voided structure and low density are provided. To achieve such a structure, the renewable polyester is blended with a polymeric toughening additive in which the toughening additive can be dispersed as discrete physical domains within a continuous matrix of the renewable polyester. Fibers are thereafter formed and then stretched or drawn at a temperature below the glass transition temperature of the polyester (i.e., “cold drawn”).