Method of making an earplug
A method of making personal protective equipment, such as a push-in earplug, is disclosed. The method includes the steps of covering a substrate with an outer layer that includes an unactivated foaming agent, positioning at least a portion of the outer layer in a mold, and activating the foaming agent such that a portion of the outer layer expands.
1. A method of making an earplug comprising the steps of:
covering an elongate core with an outer layer, wherein the elongate core comprises a first material and the outer layer comprises a second material, the second material comprising an unactivated foaming agent;
positioning at least a portion of the outer layer and the elongate core in a mold; and
activating the foaming agent of at least a portion of the outer layer such that the outer layer at least partially expands to conform to a shape of the mold and the outer layer includes an expanded sound attenuating portion and a stem portion bonded to the elongate core;
wherein the stem portion serves as a handle which may be gripped by a user, and the shape of the sound attenuating portion differs from the shape of the stem portion.
2. The method of claim 1 , wherein the sound attenuating portion has a first average density ρ1 and the stem portion has a second average density ρ2 and |ρ2>1.2 ρ1|.
3. The method of claim 1 , wherein the sound attenuating portion has a first average density ρ1 and the stem portion has a second average density ρ2 and |ρ2>1.5 ρ1|.
4. The method of claim 1 , wherein the mold comprises a first cavity that limits expansion of the outer layer.
5. The method of claim 4 , wherein the first cavity is in the form of a sound attenuating portion.
6. The method of claim 4 , wherein the mold comprises a second cavity in the form of a stem portion.
7. The method of claim 6 , wherein at least a portion of the step of activating the foaming agent occurs while the first cavity is oriented below the second cavity.
8. The method of claim 1 , wherein the step of activating the foaming agent comprises applying heat to at least a portion of the outer layer.
9. The method of claim 1 , further comprising the step of extruding the first material to form the elongate core.
10. The method of claim 1 , wherein the step of covering the elongate core comprises a step selected from the group consisting of extruding, laminating, molding, spraying and dipping.
11. The method of claim 1 , wherein the second material comprises an unactivated expandable sphere foaming agent.
12. The method of claim 1 , wherein the second material comprises an unactivated chemical foaming agent.
13. The method of claim 1 , wherein the second material comprises between 0.5% weight and 3% weight of an unactivated chemical foaming agent.
14. The method of claim 1 , wherein the second material comprises between 0.5% weight and 9.5% weight of an unactivated expandable sphere foaming agent.
15. The method of claim 1 , wherein the second material comprises a thermoplastic.
16. The method of claim 1 , wherein the second material comprises styrene-ethylene-butylene-styrene (SEBS).
17. The method of claim 1 , wherein the second material comprises a thermoset polymer.
18. The method of claim 1 , wherein the second material comprises an EPDM rubber.
19. The method of claim 1 , wherein the first material is selected from the group consisting of polypropylene and styrene-ethylene-butylene-styrene (SEBS).
20. The method of claim 1 , wherein the outer layer comprises a contiguous layer.
21. The method of claim 1 , wherein the outer layer is thermally bonded to the elongate core.
22. A method of making an earplug comprising the steps of:
extruding an elongate core comprising a first material;
covering the elongate core with an outer layer comprising a second material, the second material comprising an unactivated expandable sphere foaming agent, an unactivated chemical foaming agent, and styrene-ethylene-butylene-styrene (SEBS);
positioning at least a portion of the outer layer and the elongate core in a mold; and
applying heat to at least a portion of the outer layer such that at least a portion of the outer layer expands to at least partially conform to a shape of the mold such that the outer layer comprises an expanded sound attenuating portion and a stem portion bonded to the elongate core;
wherein the stem portion serves as a handle which may be gripped by a user, and the shape of the sound attenuating portion differs from the shape of the stem portion.
23. The method of claim 22 , wherein the sound attenuating portion has a first average density ρ1 and the stem portion has a second average density ρ2 and |ρ2>1.2 ρ1|.
24. The method of claim 22 , wherein the outer layer is thermally bonded to the elongate core.