Modified polyester fiber for cementitious composite and method for surface treatment of the same
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Solution Overview
Problem
Current surface treatments for polyester fibers to make them hydrophilic for use in engineered cementitious composites (ECC) are costly and result in coatings that are not mechanically strong enough to withstand the rigorous mixing processes of concrete materials.
Innovation Solution
A method involving alkali hydrolysis of polyester fibers followed by application of a solution containing an acid cross-linker and polyvinyl alcohol (PVA) to form a robust, cross-linked coating with a thickness of sub-micron or micron scale, which includes the option of incorporating nanoparticles like SiO2, Al2O3, or CaCO3 to enhance interfacial bonding with the cement matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If chemical surface modification with polymeric grafting is used to make polyester fiber hydrophilic, then the fiber becomes hydrophilic, but the resulting coating is too thin and not mechanically strong enough to resist high shear mixing processes
Solution Approach 1:
The patent changes the chemical parameters of the surface modification process by using acid cross-linking agents (such as citric acid, malic acid, or tartaric acid) to create cross-linked polymer structures on the fiber surface. This cross-linking transforms the simple polymeric grafting into a chemically bonded network that provides both hydrophilicity and mechanical strength. The cross-linking degree and coating thickness are controlled by adjusting the concentration of cross-linking agent and processing conditions.
Solution Approach 2:
The patent creates a composite coating structure on the polyester fiber surface by combining the base polyester fiber with grafted polymer chains and cross-linking agents. This composite structure integrates the hydrophilic properties of the grafted polymers with the mechanical strength of the cross-linked network, achieving both desired surface properties and structural integrity.
2Ease of manufacture
If simple polymeric grafting is used for surface treatment, then the process is simple and cost-effective, but the coating is not mechanically strong enough for concrete mixing applications
Solution Approach 1:
The patent introduces acid cross-linking agents as intermediary substances that mediate between the grafted polymer chains and the polyester fiber surface. These cross-linking agents form chemical bridges that strengthen the coating without requiring complex equipment or multi-step processes. The cross-linking agents react with hydroxyl groups on the polymer chains to create ester bonds, providing mechanical strength while maintaining process simplicity.
3Adaptability or versatility
If strong acid or alkali hydrolysis is used to treat PE and PP fibers to make them hydrophilic, then the fibers become hydrophilic, but the treatment is very difficult and costly
Solution Approach 1:
The patent uses inexpensive, readily available acid cross-linking agents (such as citric acid, malic acid, or tartaric acid) that can be easily applied and removed. These cross-linking agents provide the necessary hydrophilic modification without requiring expensive gas-phase plasma or corona treatment equipment. The process uses simple aqueous solutions that can be applied by conventional coating methods.
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 method produces a stable and robust PVA coating that firmly adheres to the fibers, resisting high shear mixing processes and significantly enhances the interfacial bonding between the fibers and the cement matrix, improving the mechanical properties of the composite.
Implementation Method 1
subjecting a polyester fiber to an alkali hydrolysis to obtain a hydrolyzed polyester fiber
Implementation Method 2
applying a solution containing an acid cross-linker and a polyvinyl alcohol to the hydrolyzed polyester fiber, and then curing to form a coating
Data Source
AI summary
The disclosure relates to a method for the surface treatment of a polyester fiber, a modified polyester fiber obtained therefrom, and an engineered cementitious composite containing such modified polyester fibers. The method comprises subjecting the polyester fiber to an alkali hydrolysis to obtain hydrolyzed polyester fiber; applying a solution containing an acid cross-linker and a polyvinyl alcohol to the hydrolyzed polyester fiber, then curing to form a coating having a thickness of sub-micron or micron scale on the polyester fiber, thereby obtaining the modified polyester fiber.