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.

The present invention relates to a bundled yarn, comprising plural fibers integrated by a sizing agent, wherein the sizing agent is a modified polyvinyl alcohol comprising a structural unit (X) derived from an unsaturated carboxylic acid or derivative thereof in an amount of 0.1 to 10% by mole, taking the amount of all monomer units as 100% by mole, which modified polyvinyl alcohol has a saponification degree of 85% by mole or higher.

The present invention relates to a bundled yarn, comprising plural fibers integrated by a sizing agent, wherein the sizing agent is a modified polyvinyl alcohol comprising a structural unit (X) derived from an unsaturated carboxylic acid or derivative thereof in an amount of 0.1 to 10% by mole, taking the amount of all monomer units as 100% by mole, which modified polyvinyl alcohol has a saponification degree of 85% by mole or higher.

The invention relates to composite reinforcing fibers infused or compounded with pulp fibers and/or nano-fibers. The composite reinforcing fibers are composed of polymer, e.g., polymer resin. The pulp fibers and/or nano-fibers impart improved tensile strength to the composite reinforcing fibers, as well as a resulting product formed by the fibers. The composite reinforcing fibers may be used in a variety of cementitious applications, wherein traditional reinforcing fibers are typically used.

The invention relates to composite reinforcing fibers infused or compounded with pulp fibers and/or nano-fibers. The composite reinforcing fibers are composed of polymer, e.g., polymer resin. The pulp fibers and/or nano-fibers impart improved tensile strength to the composite reinforcing fibers, as well as a resulting product formed by the fibers. The composite reinforcing fibers may be used in a variety of cementitious applications, wherein traditional reinforcing fibers are typically used.

A system (15) for manufacturing a reinforcing element (1) for reinforced concrete comprises a feeder (16) of a reinforcing fiber bundle (2) along a pultrusion path (4), an impregnating device (17) which impregnates the reinforcing fiber bundle (2) with a liquid thermoplastic polymeric resin (6) to obtain an impregnated fiber bundle (2), a forming channel (8) through which the impregnated fiber bundle (2) is conducted, a solidification device (19) of the composite thread (9) forming a solidified thermoplastic fiber-reinforced bar (11), a pulling device (20) which holds the reinforcing fiber bundle (2) taut along the pultrusion path (4), a winder (21) which winds the solidified bar (11) to form a coil (14), a provisional bending device (22) which bends the composite thread (9) not yet solidified or heats the solidified bar (11) to soften it, bends the heated bar (11) and then cools the bar (11) to solidify it again, so as to confer a continuous provisional curvature to the solidified bar (11) in the direction of the subsequent winding in the coil (14).

A prepreg suitable for use in order to reinforce a concrete or a load bearing material is provided, and the prepreg includes a polymer matrix comprising at least two components, and at least one fiber. The polymer matrix is in a ratio of 50-70% by weight relative to a total weight of the prepreg and the at least one fiber is in a ratio of 30-50% by weight relative to the total weight of the prepreg. Furthermore, the prepreg is used for damaged structures, structures with a modified structural function, or reinforcement in concretes.

Improved composite fibers, and structural materials mixed with the improved composite fibers, are produced by an improved process that vertically texturizes and impregnates resin into the fibers without introducing any substantial amount of microbubbles in the resin. By using vertical impregnation and twisting of fiber strands with specific viscosity control, stronger composite fibers, in which substantially no microbubbles are trapped, are produced with improved tensile strength and lower variance in tensile strength, for use in strengthening structural concrete and other structural materials.

Improved composite fibers, and structural materials mixed with the improved composite fibers, are produced by an improved process that vertically texturizes and impregnates resin into the fibers without introducing any substantial amount of microbubbles in the resin. By using vertical impregnation and twisting of fiber strands with specific viscosity control, stronger composite fibers, in which substantially no microbubbles are trapped, are produced with improved tensile strength and lower variance in tensile strength, for use in strengthening structural concrete and other structural materials.

Improved composite fibers, and structural materials mixed with the improved composite fibers, are produced by an improved process that vertically texturizes and impregnates resin into the fibers without introducing any substantial amount of microbubbles in the resin. By using vertical impregnation and twisting of fiber strands with specific viscosity control, stronger composite fibers, in which substantially no microbubbles are trapped, are produced with improved tensile strength and lower variance in tensile strength, for use in strengthening structural concrete and other structural materials.