A method for modifying polyvinyl alcohol fibers used in high ductility cement-based composites

Abstract

The invention provides a method for modifying polyvinyl alcohol fiber for a high-ductility cement-based composite material. The surface of the polyvinyl alcohol fiber contains a large amount of hydroxyl groups, the hydroxyl groups on the surface of the polyvinyl alcohol fiber react with a cement matrix to form a relatively strong chemical bonding force, and the strong chemical bonding force causesfiber breakage in the pull-out process, so that the ductility is affected. The method comprises the following steps: with the polyvinyl alcohol fiber as a raw material, firstly coating the surface ofthe polyvinyl alcohol fiber with a layer of epoxy resin, and then coating the surface of epoxy resin coating with a layer of fumed silica powder. Due to surface hydrophobicity of the modified polyvinyl alcohol fiber, the interfacial strength between the polyvinyl alcohol fiber and the cement matrix can be effectively weakened and the chemical bonding force can be reduced, so that the polyvinyl alcohol fiber is pulled out of the cement matrix in the stretching process, without breakage; the hydrophobicity and the wear-resistant slip property of a product are more stable, and the coating is more wear-resistant and the original physical and mechanical properties of the PVA fiber are not affected.

Description

technical field [0001] The invention relates to the technical field of modification of composite materials, in particular to a method for surface modification of polyvinyl alcohol fibers coated with epoxy resin and hydrophobic fumed silica for high ductility cement-based composite materials. Background technique [0002] High-ductility cement-based composites are a new type of fiber-reinforced cement-based composites developed in the past 20 years. High-ductility cement-based composites are prepared through system design and performance optimization based on the basic principles of micromechanics, fracture mechanics, and statistics, taking into account fiber properties, matrix properties, and fiber-matrix interface properties. It has multi-slit cracking characteristics and strain hardening characteristics and excellent crack control ability. When subjected to bending and tensile loads, due to the bridging effect of the fibers at the cracks and the stable expansion of the cr...

AI Technical Summary

Problems solved by technology

[0003] Due to its high strength, high elastic modulus and relatively low price, polyvinyl alcohol fiber is considered to be the most suitable fiber for preparing high-ductility cement-based composite materials, but because the surface of polyvinyl alcohol fiber contains a large number of hydroxyl groups, its affinity with cement is relatively low Strong, under tension, due to the strong bonding force with the cement matrix, the polyvinyl alcohol fiber is pulled out during the pull-out process instead of being pulled out

As a result, the performance of high-ductility cement-based composites will be seriously affected

[0004] At present, in order to adjust the interface performance between polyvinyl alcohol fiber and cement matrix, the surface of polyvinyl alcohol fiber is generally coated with oil agent (such as Chinese patent application number 201210468413.3). On the one hand, the oil agent is easy to enter the cement matrix and affect the performance of the cement matrix. On the one hand, the oil film coating on the surface of the fiber is easy to fall off during the molding and stirring process; another example (Chinese Patent Application No. 201610375068.7) uses a strong oxidant, potassium permanganate, to oxidize the surface of the polyvinyl alcohol fiber to make the polyvinyl alcohol fiber Apply a layer of hydrophobic substance after the surface is rough. On the one hand, it will damage the surface of the polyvinyl alcohol fiber and reduce the performance of the fiber. At the same time, the hydrophobic coating only relies on the physical adsorption force between the coating and the fiber surface, and the stability cannot be guaranteed. a question

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