Liquid thermoplastic resin and pultrusion method
A liquid acrylic resin used in reactive thermoplastic pultrusion that produces a nanocomposite/fiber-reinforced hybrid composite structure with relatively high tensile strength and high flexural strength compared to thermoplastic fiber-reinforced composites made using resin transfer molding processes. The resin is made of 70-90% methyl methacrylate, 10-30% polymeric viscosity-promoting agent, a 0.1-10% nano clay, a nitro compound retarder and an internal lubricant. The pultrusion process is carried out in a pultrusion machine that uses a relatively high percentage of fibers. The fibers are submerged in a resin bath and delivered to a curing die. Before manufacturing the resin, the inhibitor for the monomer is removed using an Alumina column and replaced with the nitro retarder. The nano clay is added to promote the reaction rate. Any resin and pultruded wastes produced during the manufacturing process can be processed and reused. Also disclosed is a method for manufacturing a composite made of the liquid acrylic resin and pultrusion dies systems.
1 . A method for making composite structures made of thermoplastic nanocomposite/fiber-reinforced composite, comprising the following steps:
a. forming a liquid resin mixture comprising: 70-90 wt. % methyl methacrylate monomer containing a polymerization inhibitor, 10-30 wt. % polymeric viscosity-promoting agent, 0.1-10 wt. % nano clay, and an internal lubricant;
b. removing said polymerization inhibitor from said methyl methacrylate monomer;
c. mixing a nitro compound retarder into said liquid resin mixture after removing said polymerization inhibitor to stabilize said liquid resin against premature polymerization and thereby to form a thermoplastic liquid resin;
d. selecting a pultrusion injection die system including a pultrusion injection die defining a mold cavity, a braid fiber delivery system, a liquid resin impregnation system, a puller configured to pull impregnated fibers through said pultrusion injection die, and a cutter configured to cut a cured composite to a desired length;
e. impregnating a plurality of braided fibers with said thermoplastic liquid resin using said liquid resin impregnation system to form wetted braided fibers;
f. delivering said wetted braided fibers into said mold cavity of said pultrusion injection die;
g. applying pressure and heat to said wetted braided fibers within said mold cavity to polymerize said thermoplastic liquid resin and form a fiber-reinforced composite;
h. cooling said fiber-reinforced composite and thereafter pulling said cooled fiber-reinforced composite from said pultrusion injection die using said puller; and
i. cutting said fiber-reinforced composite into desired lengths using said cutter.
2 . The method for making composite structures made of thermoplastic nanocomposite/fiber-reinforced composite, as recited in claim 1 , wherein said liquid resin impregnation system includes passing said braided fibers through a bath containing said thermoplastic liquid resin with said nitro compound retarder to form said wetted braided fibers.
3 . The method for making composite structures made of thermoplastic nanocomposite/fiber-reinforced composite, as recited in claim 1 , wherein said liquid resin impregnation system includes a resin tank containing said thermoplastic liquid resin with said nitro-compound retarder to create said wetted braided fibers.
4 . The method of claim 1 , further comprising recycling at least a portion of the fiber-reinforced composite or resin waste to produce a recycled material, and using the recycled material to prepare fresh liquid resin for use in forming additional fiber-reinforced composite structures.
5 . The method of claim 4 , wherein the recycling includes recovering fibers and polymer material from the fiber-reinforced composite for reuse in subsequent composite formation.