Methods for recovering expanded polymer tooling
Methods of recovering and/or recycling expanded polymer tooling, the methods including collecting expanded polymer tooling, reducing the collected expanded polymer tooling into smaller particles, treating the reduced expanded polymer tooling in order to yield an at least partially purified recovered polymer composition, and then collecting the at least partially purified recovered polymer composition. The at least partially purified recovered polymer composition can then be used to form new expandable polymer tooling.
1 . A method for recycling expandable tooling, wherein the tooling includes foamable pellets, the method comprising:
expanding the foamable pellets within a constraining container in order to apply pressure to an uncured composite workpiece;
curing the composite workpiece while the pressure is applied to the composite workpiece;
collecting the expanded foamable pellets from the constraining container;
reducing the collected expanded foamable pellets into smaller particles;
treating the reduced foamable pellets to yield an at least partially purified polymer composition, wherein the step of treating the reduced foamable pellets to yield an at least partially purified polymer composition includes: softening or dissolving the reduced foamable pellets with a nonpolar solvent, and subsequently treating the reduced foamable pellets with a polar solvent in order to remove one or more foaming agents from the reduced foamable pellets;
collecting the at least partially purified polymer composition; and
forming recovered-polymer pellets using the at least partially purified polymer composition.
2 . The method of claim 1 , wherein the reduced foamable pellets are treated with the polar solvent also in order to remove one or both of (a) an unreacted chemical blowing agent, (b) reaction products of a reaction of a chemical blowing agent.
3 . The method of claim 1 , wherein the foamable pellets comprise a thermoplastic polymer including selected from group consisting at least one of ABS, nylon, PLA, PES, PEI, polyethylene, PPO, PPS, PVC, PVDF, and PTFE.
4 . The method of claim 1 , wherein the foamable pellets comprise acrylonitrile butadiene styrene (ABS).
5 . The method of claim 1 , wherein the foamable pellets include a physical blowing agent such as selected from group consisting of carbon dioxide, nitrogen, a hydrocarbon, a chlorofluorocarbon, a hydrochlorofluorocarbon, and a supercritical fluid.
6 . The method of claim 1 , wherein the foamable pellets include a chemical blowing agent such as selected from group consisting of azodicarbonamide, a hydrazine-based compound, and sodium bicarbonate.
7 . The method of claim 1 , wherein the foamable pellets include expandable gas-filled microspheres.
8 . The method of claim 1 , wherein the foamable pellets include a foaming agent such as selected from group consisting of sodium lauryl ether sulfate, sodium lauryl sulfate, and ammonium lauryl sulfate.
9 . The method of claim 1 , wherein at least some of the foamable pellets are coated with a lubricating agent including selected from group consisting of PTFE powder, PTFE nano-powder, silicone, and a fluorinated oil.
10 . The method of claim 1 , wherein at least some of the foamable pellets have surface regions of increased crystallinity that reduce adhesion between the pellets.
11 . The method of claim 1 , wherein the expanded foamable pellets are transported to a reducing apparatus using a directed flow of a fluid.
12 . The method of claim 11 , wherein the directed flow of fluid includes a compressed gas stream or a vacuum-assisted stream.
13 . The method of claim 1 , wherein the reducing of the collected expanded foamable pellets includes is performed using a reducing apparatus equipped with a sizing filter, wherein the reducing apparatus is one of a grinder, a mill, or a chopper, or a combination thereof equipped with a sizing filter.
14 . The method of claim 1 , wherein treating the reduced foamable pellets includes heating the pellets above a glass transition temperature of the polymer composition.
15 . The method of claim 1 , wherein treating the reduced foamable pellets includes applying a vacuum to degas the polymer composition.
16 . The method of claim 1 , wherein the step of treating the reduced foamable pellets with the nonpolar solvent and the polar solvent comprises subjecting the polymer composition to a phase separation process in which the nonpolar solvent and the polar solvent are immiscible with each other.
17 . The method of claim 1 , wherein the at least partially purified polymer composition is tested to determine elongation at break of the polymer composition.
18 . The method of claim 17 , wherein the at least partially purified polymer composition is modified with a chain extender and/or virgin polymer composition when the elongation at break fails to meet a predetermined threshold.
19 . The method of claim 1 , wherein forming the recovered-polymer pellets includes extruding the at least partially purified polymer composition.
20 . The method of claim 1 , wherein the recovered-polymer pellets are injection molded into a test specimen prior to reuse in manufacturing.