CN-121976394-A - Method for preparing hyperbranched polyamide surface modified polyvinyl alcohol fiber by one-step method and application

Abstract

The invention relates to the technical field of surface modification of polyvinyl alcohol fibers, and particularly provides a method for preparing hyperbranched polyamide surface modified polyvinyl alcohol fibers by a one-step method and application of the hyperbranched polyamide surface modified polyvinyl alcohol fibers in cement-based materials. The surface modification method comprises the following raw materials of 1 part of polyvinyl alcohol fiber, 1-3 parts of 3, 5-diaminobenzoic acid, 0.1-0.3 part of 4-dimethylaminopyridine and 100 parts of N, N-dimethylformamide, wherein the surface modification method is to obtain the surface modified polyvinyl alcohol fiber by mixing the raw materials and then keeping the raw materials at a constant temperature of 50-80 ℃ for 2-5 hours. The application comprises the steps of verifying the change of the interfacial strength between the fiber before and after modification and the cement-based material through a single fiber pulling sample, and obtaining the change of the mechanical property parameters of the fiber before and after modification through a single fiber stretching test. Compared with unmodified polyvinyl alcohol fibers, the tensile strength and the elongation at break of the surface-modified polyvinyl alcohol fibers are respectively improved by 1.1-1.6 times and 1.4-2.2 times, the surface-modified polyvinyl alcohol fibers can enhance the interface strength with cement and reach 3.7-6.3 times of the unmodified polyvinyl alcohol fibers, and the method can be widely applied to the field of fiber reinforced cement-based composite materials and has wide application prospects.

Inventors

• GUO BIN
• CHEN GONG
• LI SHUO

Assignees

• 南京林业大学

Dates

Publication Date

20260505

Application Date

20260119

Claims (1)

1. 1. A method for preparing hyperbranched polyamide surface modified polyvinyl alcohol fiber by a one-step method and application thereof. The preparation method of the hyperbranched polyamide surface modified polyvinyl alcohol fiber is characterized by weighing 1 part of the polyvinyl alcohol fiber, 1-3 parts of 3, 5-diaminobenzoic acid, 0.1-0.3 part of 4-dimethylaminopyridine and 100 parts of N, N-dimethylformamide, placing the polyvinyl alcohol fiber into a flat-bottom three-neck flask, placing the device into a water bath kettle to react for 2-5 h at a constant temperature of 50-80 ℃, then soaking and flushing the obtained fiber with 95% ethanol and ultrapure water successively, removing residual solvent and reaction reagent on the surface to obtain the hyperbranched polyamide surface modified polyvinyl alcohol fiber, further, obtaining a single fiber pulling-out sample in a cement matrix through a self-made die, and then placing the single fiber pulling-out sample into a self-made clamping groove for pulling-out test, so as to prove that the interface strength between the fiber and the cement matrix is obviously improved before and after modification.

Description

Method for preparing hyperbranched polyamide surface modified polyvinyl alcohol fiber by one-step method and application Technical Field The invention relates to the technical field of polyvinyl alcohol fiber modification, in particular to a method for preparing hyperbranched polyamide surface modified polyvinyl alcohol fiber by a one-step method and application of the hyperbranched polyamide surface modified polyvinyl alcohol fiber in cement-based materials. Background The polyvinyl alcohol fiber has wide application prospect in the fields of textile, biomedicine, composite materials, building reinforcing materials and the like due to excellent hydrophilicity, biocompatibility, degradability and high strength and modulus. However, the surface of the polyvinyl alcohol fiber is rich in hydroxyl groups, the hydrophilicity is strong, the water absorption is easy to be caused in a humid environment, the mechanical property is reduced, and the surface lacks enough active reaction sites or functional groups, so that the requirement of multi-scene application is difficult to meet. To overcome these drawbacks, surface modification of polyvinyl alcohol fibers to impart new physicochemical properties thereto has become key to improving their performance and application. The surface modification method commonly used at present mainly comprises physical coating, plasma treatment, surface graft polymerization, chemical crosslinking and the like. However, the methods have the common defects of weak binding force and easy falling of a physical coating layer, difficult lasting plasma treatment effect and high equipment cost, and the traditional surface grafting polymerization has the common steps of complex steps, needs to use a catalyst or an initiator, possibly introduces impurities, has complex reaction control and is difficult to realize a uniform and compact modified layer. Hyperbranched polymers are a special class of polymers with highly branched three-dimensional structures, a large number of terminal functional groups and good solubility. Compared with the dendritic polymer with perfect structure, the hyperbranched polymer has simple synthesis process, lower cost and easy scale. The hyperbranched polymer (such as hyperbranched polyamide, polyester and polyamine) is introduced to the surface of the fiber, so that the density of surface functional groups can be greatly increased, the wettability and the adhesiveness of the fiber are effectively improved, and a rich reaction platform is provided for further functionalization. The prior method, such as a two-step method for preparing the polyamide surface modified polyvinyl alcohol fiber in the patent CN120158927A, can effectively improve the interfacial shear strength between the fiber and the thermoplastic starch film, and the surface modification of the carbon fiber in the patent CN119663625A is carried out by plasma treatment and surface grafting of polyamide-amine dendritic macromolecules, so that the interfacial bonding strength of the modified carbon fiber and the epoxy resin matrix composite material is improved, and the tensile property of the carbon fiber is also improved. However, these modification methods are complicated in process and high in cost, and are not favorable for practical application. Cement-based materials are the most widely used building materials worldwide, and the problems of high brittleness, low tensile strength, easiness in cracking and the like limit the durability and safety of engineering structures for a long time. With the development of modern constructional engineering to high-rise, large-span and special structures, higher requirements are put on toughness, crack resistance and durability of cement-based materials. Fiber reinforcement is considered as one of the effective ways to improve brittleness of cement-based materials, and polyvinyl alcohol fibers have been the key points of research and application because of their high strength, high modulus, good alkali resistance, strong adhesion to cement substrates, and the like. However, the interface between the traditional polyvinyl alcohol fiber and the cement matrix is too strong, so that the fiber is more easily broken rather than pulled out when being stressed, and the full play of the toughening effect is limited. The traditional polyvinyl alcohol fiber surface modification method (such as plasma treatment, chemical coating and the like) is mostly a multi-step process, has complex process and high cost, has insufficient binding force between a modified layer and a fiber matrix, and is easy to generate interface degradation in cement alkaline environment and long-term use. Hyperbranched polymers have a highly branched three-dimensional structure, a large number of terminal functional groups and good solubility, exhibiting unique advantages in the modification of composite interfaces. The hyperbranched polyamide has rich amine/carboxyl functional groups at the tail end, can