Push-in earplug and method of making the same using a mandrel
A push-in earplug is provided. The push-in earplug comprises an elongate core comprising a core material. The push-in earplug also comprises an outer layer comprising a foam material, the outer layer covering at least a portion of an outer surface of the elongate core. The push-in earplug also comprises a channel extending through the elongate core from a first end of the elongate core to the second end of the elongate core.
1. A method of manufacturing an earplug, the method comprising:
forming an earplug preform with a first end and a second end opposite the first end portion, the earplug preform comprising a substrate covered by a core layer and an outer layer, wherein the substrate is chemically inert with respect to a core material, and wherein the core material comprises a polyamide mixture comprising a polyamide and an impact modifier;
positioning the earplug preform at least partially within a mold cavity; and
applying heat to at least a portion of the mold cavity such that at least a portion of the outer layer expands and conforms to a shape of the mold cavity and the outer layer thermally bonds to the core layer; and
removing the substrate, wherein, after the substrate is removed, the core layer has a channel extending from the first end to the second end.
2. The method of claim 1 , wherein the mold cavity comprises a stem portion and a sound attenuating portion, and wherein applying heat causes the earplug preform to form a stem and a sound-attenuating portion in the stem and sound attenuating portions, respectively.
3. The method of claim 1 , wherein the substrate has a higher melting point than an activation temperature of a material forming the outer layer.
4. The method of claim 1 , wherein the substrate comprises a fluoropolymer.
5. The method of claim 1 , wherein the outer layer of the earplug has a first length, the core layer has a second length, and wherein the first length is longer than the second length.
6. The method of claim 1 , wherein an axial length of the core layer and an axial length of the substrate are about the same.
7. The method of claim 1 , wherein the core material also comprises polypropylene.
8. A method of making an article, the method comprising:
covering a substrate with a core layer, wherein the substrate comprises a first end and a second end, and the core layer substantially covers an outer surface of the substrate, and wherein the core layer comprises a mixture of a polyamide and an impact modifier;
covering the core layer with an outer layer to prepare a preform having a first end portion and a second end portion, the outer layer comprises an expandable material having an activation temperature, and wherein the substrate comprises a material with a melting point above the activation temperature;
positioning the first end portion of the preform in a first cavity of a mold and the second end portion in a second cavity of the mold, the first mold cavity having a diameter that is smaller than a diameter of the second mold cavity at its widest point; and
increasing the temperature of the mold to at least the activation temperature of the expandable material to activate the expandable material within the second end portion to form the second end portion into a sound-attenuating portion.
9. The method of claim 8 , and further comprising: removing the substrate to create a channel extending through the core layer from the first end to the second end.
10. The method of claim 8 , wherein the substrate has a constant cross-section from the first end to the second end.
11. The method of claim 10 , wherein the cross-section is selected from a group consisting of: a circle, an oval, a square and a rectangle.
12. The method of claim 8 , wherein the substrate has a melting point higher than 190° C.
13. The method of claim 8 , wherein covering the substrate comprises extruding the core layer over the substrate.
14. The method of claim 8 , wherein the activation temperature is between 100° C. and 205° C.
15. A method of forming an earplug, the method comprising:
forming a core layer with a first end and a second end, wherein the core layer has a hollow interior extending from the first end to the second end, and wherein the core layer is formed around a mandrel, and wherein forming comprises: extruding the core layer over the mandrel; laminating the core layer over the mandrel; dipping the mandrel into a core layer material; spraying a core layer material over the mandrel; or molding the core layer over the mandrel;
covering the core layer with an expandable outer layer; activating the expandable outer layer, wherein activating the expandable outer layer comprises causing the expandable outer layer to expand and form a sound attenuating portion and a stem portion, and wherein a density of the earplug is greater at the first end than the second end; and wherein the hollow interior of the core layer is maintained during activation of the outer layer such that the earplug has a channel extending from the first end to the second end; and
wherein the core layer comprises a mixture of a polyamide and an impact modifier.
16. The method of claim 15 , wherein the mandrel is chemically inert with respect to the core layer.
17. The method of claim 15 , wherein activation comprises heating the expandable outer layer to an activation temperature, and wherein a melting point of the mandrel is higher than the activation temperature.
18. The method of claim 15 , wherein the core layer is extruded.
19. The method of claim 15 , wherein the core layer has a melting point that is higher than an activation temperature of the expandable outer layer.
20. The method of claim 15 , wherein the core layer maintains the hollow interior extending from the first end to the second end throughout the activation of the expandable outer layer.