WO2019113697A1

WO2019113697A1 - Methods of molding expanded polymer beads and molded foam articles

Info

Publication number: WO2019113697A1
Application number: PCT/CA2018/051586
Authority: WO
Inventors: Daniel Eamon Abram; Farid Golnaraghi
Original assignee: Simon Fraser University
Priority date: 2017-12-12
Filing date: 2018-12-12
Publication date: 2019-06-20

Abstract

Methods of molding expanded polymer beads into low-density molded polymer foam articles are described herein. The methods include making macro-scale cavities in the foam through the molding process. In an embodiment, macro-scale 5 cavities are made by molds having protrusions configured to provide, for example, channels in the molded foam article. In an embodiment, an expandable material is included in a mixture that, when molded, creates macro-scale cavities within the molded foam article as it is molded.

Description

METHODS OF MOLDING EXPANDED POLYMER BEADS AND MOLDED

FOAM ARTICLES

BACKGROUND

Foams, such as those made from polystyrene, polypropylene, polyurethane, polyethylene or other polymers, are used for applications including impact mitigation, thermal insulation, acoustic insulation, and floatation. Foam is commonly used for impact mitigation in vehicle collision-protection parts, such as bumpers, head and body protection equipment, and product packaging and protection. Foam used for thermal and acoustic insulation is commonly found in machines, appliances, buildings, and transport vehicles. Foam is also used in boats, buoys, surfboards, and other floating applications. The mechanical properties of foams vary depending on the polymer used and the production process. Some foams, such as those made from polyethylene or polypropylene, are reversible, meaning that the foam can rebound to its initial state after being deformed on impact. Other foams, such as those made from polystyrene, are irreversible, meaning that the foam is single-use only for impact mitigation, as the foam will remain deformed after impact.

Foams are generally made from one of two types of plastic: thermoplastic and thermoset. Thermoplastics, such as polystyrene and polypropylene, can be melted down to a liquid, cooled, and reheated to their melting point again without significant degradation, making them ideal for recycling and injection molding. Thermoset plastics, such as poly(isocyanurate), are usually malleable or liquid before they are molded and cured; afterwards, the plastic remains in a permanent solid state and will combust with heat rather than melt. Some plastics, such as polyurethane, can be either thermoplastic or thermoset, depending on how they are chemically produced.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. In an aspect the present disclosure provides a method of making a molded foam article.

In accordance with aspects of the present disclosure, a method for manufacturing a low-density, polymer-based molded foam article is provided. The method generally includes:

combining an expanding material with an expandable polymer bead to create a blowing component;

blending the blowing component into a foam-molding material to create a mixture;

placing the mixture in a mold;

expanding the blowing component within the foam-molding material to create a plurality of macro-scale cavities in the mixture; and

molding the molded foam article.

In an embodiment, the method includes mixing an expandable material with expanded polymer beads to provide a mixture; and molding the mixture into a molded foam article, thereby expanding the expandable material to provide a plurality of macro-scale cavities disposed in the molded foam article.

In an embodiment, the method includes placing expanded polymer beads into a mold having one or more major surfaces and a plurality of protrusions extending therefrom; and molding the expanded polymer beads in the mold to provide a molded foam article having a plurality of macro-scale cavities disposed therein formed by the plurality of protrusions.

In another aspect, the disclosure provides a molded foam article comprising foam having micro-scale cells, and a plurality of macro-scale cavities disposed in the foam.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects of the present disclosure will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: FIGURE 1 shows a botom view of on representative embodiment of a helmet in accordance with one or more aspects of the present disclosure, showing open cavities disposed in a foam material;

FIGURE 2 shows a macroscopic view of porous foam in accordance with one or more embodiments of the present disclosure, the porous foam including irregularly sized and placed cavities;

FIGURES 3A and 3B show side views of two molds in accordance with one or more embodiments of the present disclosure that contain protrusions configured to form channel-like cavities in the foam;

FIGURE 4A shows an expandable material disposed within a polymeric foam in a mold, in accordance with an embodiment of the present disclosure;

FIGURE 4B illustrates irregularly-sized, -shaped and -placed cavities disposed within a molded foam article, in accordance with an embodiment of the present disclosure, resulting from molding the polymeric foam of FIGURE 4A;

FIGURE 5 shows a cross-sectional view of two molded foam blocks, in accordance with an embodiment of the present disclosure, each of the foam blocks separately having open cavities, the blocks fused together to provide closed cavities; and

FIGURE 6 shows a cross-sectional view of a molded foam article, in accordance with an embodiment of the present disclosure, molded to be low density.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as precluding other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed.

In the following description, specific details are set forth to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

The present application may include references to directions, such as “forward,” “rearward,” “front,” “rear,” “upward,” “downward,” “top,” “bottom,” “right hand,” “left hand,” “lateral,” “medial,” “distal,” “proximal,” “in,” “out,” “extended,” etc. These references, and other similar references in the present application, are only to assist in helping describe and to understand the particular embodiment and are not intended to limit the present disclosure to these directions or locations.

The present application may also reference quantities and numbers. Unless specifically stated, such quantities and numbers are not to be considered restrictive, but exemplary of the possible quantities or numbers associated with the present application. Also in this regard, the present application may use the term“plurality” to reference a quantity or number. In this regard, the term“plurality” is meant to be any number that is more than one, for example, two, three, four, five, etc. The terms “about,”“approximately,”“near,” etc., mean plus or minus 5% of the stated value. For the purposes of the present disclosure, the phrase“at least one of A, B, and C,” for example, means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C), including all further possible permutations when greater than three elements are listed.

Expanded polymer foam used for impact mitigation, insulation, and floatation has been shown to perform better with lower density. In the particular case of impact mitigation, cavities in the foam allow it to compress more when impacted forcefully to slow the deceleration of the colliding object. Increased porosity in foam also improves its insulation capability. Likewise, for floatation, an object with lower weight is more buoyant than a heavier object of the same shape and size.

However, the methods for creating conventional molded foam products, such as EPS, does not take advantage of the fact that the compressibility of the foam is directly related to how effectively the foam can mitigate an impact. In general, the more compressible the foam, the better the impact mitigating performance. Rather, conventional EPS foam consists of tightly-packed expanded beads with no macro scale spaces between them. On impact, the micro-porous beads collapse and are compressed. Although the foam is already 95-98% air because of the micro-scale porosity of the expanded polymer beads, such micro-scale porosity is frequently insufficient for certain applications, as will be further described below.

In an aspect, the present disclosure provides a method of molding foam to provide a molded foam article that has lower density due to macro-scale pores disposed in the molded foam article. In an embodiment, the method includes adding an expandable agent, such as solid or liquid carbon dioxide, liquid nitrogen, or other expandable agent, to expanded polymer beads before or during the molding process. As the expandable agent releases gas, macro-scale cavities form within the foam, creating a molded foam article resembling spongy bone. In an embodiment, the methods described herein include molding expanded polymer beads into a mold including one or more major surfaces, and protrusions extending therefrom, to provide one or more macro-scale cavities which extend partway into or all the way through the molded foam article.

As described further herein, molded foam articles have a wide variety of uses. Such low-density foam can be used in protective headgear, vehicle safety features and devices, airplanes, construction, thermal insulation, acoustic insulation, floatation devices, and other applications. Additionally, such applications benefit in may regards through the addition of macro-scale cavities provided by the methods of the present disclosure.

The following description provides several illustrations of the molded low-density foam and the methods for making the same.

METHODS OF MOLDING FOAM ARTICLES

In an aspect, the present disclosure provides methods of molding foam to provide molded foam articles including relatively-large cavities, or macro-porosity, which make the foam more compressible than molded foam articles having, for example, only micro-scale porosity. In this regard, as an impact is applied to the molded foam articles described herein, the macro-scale cavities, as well as micro scale cavities, collapse and compress, reducing impact. Such macro-scale porosity, resembling spongy bone structure, provides not only greater impact-mitigation properties, but greater properties in thermal insulation, acoustic insulation, and floatation. Further, molding the foam in a way that provides macro-scale cavities disposed in the foam also allows manufacturers to use less material, which would reduce manufacturing costs, and ultimately cause less material to end up in landfills.

In an embodiment, the method includes entrapping an expandable material throughout expanded beads. In these embodiments, the method includes mixing an expandable material with expanded polymer beads to provide a mixture, and molding the mixture into a molded foam article, thereby expanding the expandable material to provide a plurality of macro-scale cavities disposed in the molded foam article.

An example manufacturing process for forming molded thermoplastics, such as expanded polystyrene (EPS), according to the present disclosure will now be described. A blowing agent (also referred to as a "foaming agent"), often pentane gas or carbon dioxide, is contained inside pre-expanded polymer beads (sometimes referred to as "pellets" or "resin"). Next, the expanded polymer beads are heated, e.g., with steam, to allow the blowing agent escape, ingesting air, causing the beads to expand substantially compared to their original size. In an embodiment, the beads are aged for at least 24 hours to allow air ingestion, to cool, and increase hardness.

The expanded polymer beads are mixed with an expandable material to provide a mixture and then molded. In an embodiment, molding includes placing the mixture in a mold and exposing the mixture to heat, thereby fusing two or more of the expanded polymer beads. For example, in an embodiment, the expanded beads are placed into a steam molding machine along with an expandable element. The density of the block produced is in direct relation to how many beads were added; the resulting density is normally 95-98% air and 2-5% expanded beads. Low-pressure steam is injected into and between the beads to expand them further, as well as fuse them together. Additionally, as described further herein with respect to FIGURES 4A and 4B, through molding, the expandable element is expanded to provide cavities disposed within the molded foam article.

Turning to FIGURE 4A, a diagram of an expandable material 19 entrapped within a plurality of expanded foam beads 21 in a mold 22 is illustrated. During the molding process, the expandable material 19 expands and creates irregularly sized, shaped, and positioned cavities 20 in between the expanded foam particles 21, as illustrated in FIGURE 4B. In some embodiments, the foam is EPS foam.

In some embodiments, the mold 22 contains gaps or holes, which allow foam 21 to escape as the expandable material 19 expands, pushing the foam 21 out towards the inner edges of the mold 22. The expandable material 19 may also be placed along the edges between the foam 21 and mold 22 so that open cavities are created in the foam 21.

The expandable material 19 expands and becomes pressurized against the foam 21 and the pressure of the mold 22. Expansion stops when the pressure of the expandable material 19 is equal to the pressure placed on it by the mold. In some embodiments, two or more sections of expandable material 19 are close enough together that when they expand, they create a single cavity 20 in the foam 21. The cavities 20 may be any shape and size.

The mold may be configured to mold foam 21 to provide any shape, such as blocks, sheets, head-protection, body armor, or vehicle parts, for the purpose of impact mitigation, floatation, or thermal or acoustic insulation, as described further herein with respect to, for example, the helmet FIGURE 1.

In an embodiment, the methods described herein use an expandable material configured to expand during molding to provide macro-scale cavities. The expandable material can be any expandable material configured to expand during molding. In an embodiment, the expandable material is selected from the group consisting of an expandable gas, an expandable liquid, and an expandable solid. In some embodiments, the expandable material is a single expandable material. In other embodiments, the expandable material includes two or more materials or compounds.

In an embodiment, the expandable material is a liquid or a solid material that provides an inert gas when expanded. In an embodiment, the expandable material includes a material that expands when heated to or above a phase-transition temperature. As the expandable material is heated to or above a phase-transition temperature, such as a temperature of phase-transition between a solid and a gas, the expandable material expands significantly, thereby providing macro-scale cavities in the molded foam. In an embodiment, the expandable material begins in solid form. For example, carbon dioxide has an expansion ratio of 845, meaning that solid carbon dioxide can expand up to 845 times its original volume when it sublimates and changes to gas form. As described further herein, the expandable material, such as solid or liquid carbon dioxide, nitrogen, or other inert gas, is mixed with expanded polymer beads before the molding process that molds expanded beads into a foam article. The mixture is then molded to provide a molded foam article including macro-scale cavities resulting from expansion of the expandable material.

In an embodiment, the expandable material expands as a result of a chemical reaction. In an embodiment, the expandable material includes two or more elements or compounds that expand due to a chemical reaction, such as a chemical reaction that provides a gas as a reaction product. In an embodiment, the chemical reaction does not include isocyanate or polyol reactants.

In other embodiments, cavities 20 may be created in the foam 21 by mixing thin-shelled, hollow objects of a lightweight material that can withstand the heat and pressure of the molding process into the beads before the molding process so that cavities 20 are created in the foam 21 during the molding process.

In an embodiment, the method for method of making low-density polymer bead-based molded foam articles includes placing expanded polymer beads into a mold having one or more major surfaces and a plurality of protrusions extending therefrom, and molding the expanded polymer beads in the mold to provide a molded foam article having a plurality of cavities disposed therein. As discussed further herein, the macro-scale cavities are formed by the plurality of protrusions (see FIGURES 3A and 3B). In FIGURES 3A and 3B, the molds are shown to include a major surface and protrusions l7a and l7b extending therefrom. In the illustrated embodiments, molds 16 are in contact with expanded polymer beads 18. During molding of the expanded polymer beads 18, the protrusions l7a and l7b form macro scale cavities in the expanded foam article. The protrusions l7a and l7b may be of any suitable shape, diameter, and length to form cavities in the expanded polymer beads 18. Further, the protrusions l7a and l7b may have a shape configured to extend through a portion of the expanded polymer beads 18. Alternatively, the protrusions l7a and l7b may be configured to extend all the way through the expanded polymer beads 18.

Like cavities formed by expandable materials, cavities formed by molds having protrusions are configured to increase compressibility. Spacing between and arrangement of the protrusions l7a and l7b may be of any suitable distance.

In an embodiment, the mold is configured to provide a plurality of cavities that are irregularly distributed within the molded foam article. In an embodiment, the mold is configured to provide a plurality of cavities that are distributed within the molded foam article in a pattern. In an embodiment, the mold is configured to provide one or more open cavities.

In an embodiment, the mold is configured to provide one or more cavities that extend through a portion of the molded foam article, as illustrated in FIGURES 3A, 3B and 6. Alternatively or additionally, in an embodiment, the mold is configured to provide one or more cavities that extend through the entire molded foam article to provide one or more tunnels.

In an embodiment, one or more cavities of the plurality of cavities have a shape selected from the group consisting of a channel, a sphere, and a free shape.

The molded foam article may be molded into any shape suitable for impact mitigation, such as blocks, sheets, vehicle parts, head-protecting devices, body armor; into any shape for insulation, such as blocks or sheets; or for floatation, such as a boat, boat parts, any board to be used in water, or buoy. The molded foam article may also be cut or further shaped into any shape after it has been molded.

A surface of the molded foam article containing open cavities may be coupled with another material to provide a cover for the open cavities. In an embodiment, the cover comprises a material selected from the group consisting of plastic, leather, fabric, metal, foam, and combinations thereof. In this regard, otherwise open cavities may be covered to provide closed cavities.

In an embodiment, the molded foam article is a first molded foam article, the method further comprising coupling a second molded foam article to a surface of the first molded foam article to provide a coupled molded foam article, thereby providing one or more closed cavities disposed within the coupled molded foam article, as discussed further below with respect to FIGURE 5. In an embodiment, the surface of the molded foam article is coupled to the cover with a coupler. In an embodiment, the coupler is selected from the group consisting of a chemical fastener, an adhesive, a hook and loop closure, a button, a pin, a bolt, and combinations thereof. In an embodiment, coupling includes a coupling method selected from the group consisting of fusion, thermoforming, sewing techniques, radio-frequency sealing, ultrasonic welding, thermal impulse sealing, and combinations thereof.

In an embodiment, the mold includes a release coating. In an embodiment, the release coating is selected from the group consisting of Nicklon Plus (Nickel Teflon Plus), Tungsten Disulfide, and Teflon.

The methods described herein include molding expanded polymer beads. The expanded polymer beads can be any expanded polymer beads suitable for molding.

In an embodiment, the expanded polymer beads include a thermoset. In an embodiment, the expanded polymer beads include a thermoplastic.

In an embodiment, the expanded polymer beads include an irreversible foam. In an embodiment, the irreversible foam comprises a material selected from the group consisting of expanded polystyrene, expanded polyurethane, expanded polylactic acid, and combinations thereof.

In an embodiment, the expanded polymer beads include a reversible foam. In an embodiment, the reversible foam includes a material selected from the group consisting of expanded polypropylene, polyurethane, silicone, latex foam rubber, and combinations thereof.

In an embodiment, the expanded polymer beads include two or more different polymers.

MOLDED FOAM ARTICLES

In another aspect, the present disclosure provides a molded foam article including a foam having micro-scale cells; and a plurality of macro-scale cavities disposed in the foam.

The molded foam articles include a foam having micro-scale cells. Such micro-scale cells include cells having a smallest dimension smaller than about 1 micrometer. In an embodiment, the micro-scale cells are open cells. In an embodiment, the micro-scale cells are closed cells.

Additionally, the molded foam articles described herein include macro-scale cavities, such as those provided by the methods of the present disclosure. See, e.g., FIGURE 2, showing a macroscopic view of molded foam article. The molded foam article includes a porous foam 15, with irregularly sized and placed cavities 14. Such macro-scale cavities have a smallest dimension greater than 1 micrometer. As described further herein, such macro-scale cavities may be configured to provide improved impact mitigation, buoyancy, sound dampening, etc., by providing a molded foam article having greater compressibility than a molded foam article without such macro-scale cavities.

The molded foam article may be made according to any of the methods described herein. In one embodiment, the molded foam article is made by molding foam with an expandable material, mixed within expanded polymer beads that make up the foam 15, as discussed further herein with respect to FIGURES 4A and 4B. As such, the expandable material expands during molding, thereby providing at least some of the macro-scale cavities 14. Using the methods described herein, the molded foam article has a lower density than if molded without the expandable material.

In an embodiment, the molded foam article includes two or more molded foam articles coupled together. See, e.g., FIGURE 5, showing a molded foam article including two coupled molded foam articles. As illustrated, the molded foam article blocks 23a and 23b, each separately having open cavities, are coupled together to provide closed cavities 24, 25, 26a, and 26b. In some embodiments, two open cavities disposed on separate foam blocks 23a and 23b align, providing a closed cavity 24 in which edges of the respective open cavities meet. In certain other embodiments, the edges of two open cavities disposed on separate foam blocks do not align, creating a skewed cavity 25. In certain other embodiments, one foam block 23a may be coupled with another foam block 23b in such a way that the cavities do not align, providing two flat-edged closed cavities 26a and 26b. The foam blocks 23a and 23b may be any shape and thickness and may be coupled together using any mechanical or chemical means, such as mechanical fastening, fusion, or adhesion. Turning to FIGURE 6, a cross-sectional view of a molded foam article in accordance with an embodiment of the disclosure is illustrated. The molded foam article 27 includes two pluralities of cavities 28 and 29 and, in this regard, is molded to have a low density and have, for example, superior impact-mitigation properties. Molded foam article 27 includes a first plurality of cavities 28 disposed on a first major surface. In the illustrated embodiment, the plurality of cavities 28 are open cavities. In an embodiment, open cavities, such as the cavities of the second plurality of cavities 29, are coupled to a cover 30. In this regard, the second plurality of cavities 29 can be covered with another material 30 to provide a plurality of closed cavities 29. The material 30 may be a material such as polycarbonate, carbon fiber, plastic, leather, fabric, metal or more foam, and may be attached via mechanical or chemical means such as adhesive, fasteners, or steam molding.

The plurality of open cavities 28 may be created using any of the methods described herein, including the molding method described further herein with respect to FIGURES 3A and 3B. In the illustrated embodiment, open cavities 28 extend a portion of the way through the molded foam article 27. Likewise, open cavities may extend through the entire thickness of the molded foam article 27 depending at least in part on the length of the protrusions and the spacing of the one or more major surfaces of the mold. The molded foam article 27 may have any shape for configured for impact mitigation or packaging, such as blocks, sheets, vehicle parts, head-protection, or body armor; or into any shape for thermal or acoustic insulation, such as blocks or sheets; or for floatation, such as a boat, boat parts, any board to be used in water, or buoy.

In an embodiment, such as shown in FIGURE 1, the molded foam article is a head protecting-device, such as a helmet. Head-protecting device 10 includes a molded foam 11, such as molded EPS foam, having micro-scale cells (not shown). The head-protecting device 10 further includes, a plurality of open cavities 13 disposed in the foam 11. In the illustrated embodiment, the head-protecting device 10 includes ventilation holes 12. The cavities 13 can be produced by a mold having a plurality of protrusions, as discussed further herein with respect to FIGURES 3A and 3B. In the illustrated embodiment, the open plurality cavities 13 are disposed on a surface of the head-protecting device 10 configured to contact a head of a wearer. Altematively or additionally, the plurality of cavities 13 can be disposed on an outer surface opposite the head of a wearer.

In some embodiments, a polycarbonate shell (not shown) may be coupled to a surface of head-protection device 10, such as an outer surface of the head-protection device 10. For purposes of illustration, the plurality of cavities 13 are depicted only in one area of the head-protecting device 10. However, in an embodiment, cavities 13 are disposed, for example, over an entire surface of the head-protecting device 10. The cavities 13 also may extend all the way through the foam 11, or only partway, through a thickness of the head-protecting device 10.

In other embodiments, the foam 11 is molded into shapes other than head- protecting devices, including but not limited to sheets or blocks for packaging, transportation, insulation, or other purposes; vehicle bumpers; plane parts; boat parts; or body armor. The foam 11 may also be cut into any shape after it has been molded. The cavities 13 may be placed anywhere on or in the foam, and be any shape, size, depth, and density, depending on the application.

The principles, representative embodiments, and modes of operation of the present disclosure have been described in the foregoing description. However, aspects of the present disclosure, which are intended to be protected, are not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. It will be appreciated that variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present disclosure. Accordingly, it is expressly intended that all such variations, changes, and equivalents fall within the spirit and scope of the present disclosure as claimed.

Claims

CLAIMS The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for manufacturing a low-density, polymer-based molded foam article, comprising:

placing the mixture in a mold;

molding the molded foam article.

2. The method of Claim 1, wherein the expanding material is selected from the group consisting of a gas, a liquid, and a solid.

3. The method of Claims 1 and 2, wherein the expanding material includes a material that expands when heated to or above a phase-transition temperature, and wherein the method further comprises heating the mixture to create the plurality of macro-scale cavities disposed in the molded foam article.

4. The method of Claim 3, wherein the expanding material is a liquid or a solid material that provides an inert gas when expanded.

5. The method of Claim 3, wherein the expanding material is selected from the group consisting of solid carbon dioxide, liquid carbon dioxide, liquid nitrogen, and solid nitrogen.

6. The method of Claims 1 and 2, wherein the expandable material expands as a result of a chemical reaction, and wherein the method further comprises the step of inducing the chemical reaction of the mixture to create the plurality of macro-scale cavities disposed in the molded foam article.

7. The method of Claim 1, wherein one or more cavities of the plurality of cavities are irregularly dispersed within the molded foam article.

8. The method of Claim 1, wherein one or more cavities of the plurality of cavities are irregularly shaped.

9. The method of Claim 1, wherein the plurality of cavities are disposed in the molded foam article in an organized pattern.

10. The method of Claim 1, wherein one or more cavities of the plurality of cavities are open.

11. The method of Claim 1, wherein one or more cavities of the plurality of cavities are closed.

12. The method of Claim 1, wherein one or more cavities of the plurality of cavities extend through at least a portion of the molded foam article.

13. The method of Claim 1, wherein one or more cavities of the plurality of cavities extend through the entire molded foam article to define a tunnel.

14. The method of Claim 1, wherein the step of molding comprises placing the mixture in a mold and exposing the mixture to heat, thereby fusing one or more of the expandable polymer beads.

15. A method of manufacturing a low-density, polymer-based molded foam article, comprising:

placing expandable polymer beads into a mold, the mold having one or more major surfaces and a plurality of protrusions extending therefrom; and

molding the expandable polymer beads in the mold to provide a molded foam article having a plurality of macro-scale cavities formed by the plurality of protrusions.

16. The method of Claim 15, wherein the mold is configured to provide a plurality of cavities that are uniformly distributed within the molded foam article

17. The method of Claim 15, wherein the mold is configured to provide a plurality of cavities that are irregularly distributed within the molded foam article.

18. The method of Claim 15, wherein the mold is configured to provide one or more open cavities.

19. The method of Claim 15, wherein the mold is configured to provide one or more cavities that extend through a portion of the molded foam article.

20. The method of Claim 15, wherein the mold is configured to provide one or more cavities that extend through the entire molded foam article to provide one or more tunnels.

21. The method of Claim 15, wherein molding comprises placing the expandable polymer beads in a mold and exposing the expandable polymer beads to heat, thereby fusing one or more of the expandable polymer beads.

22. The method according to any of the preceding claims, wherein the molded foam article is a first molded foam article, the method further comprising coupling a second molded foam article to the first molded foam article to provide a coupled molded foam article, thereby providing one or more closed cavities disposed within the coupled molded foam article.

23. The method according to any of the preceding claims, further comprising coupling a cover to a surface of the molded foam article.

24. The method of Claim 23, wherein the surface of the molded foam article includes one or more open cavities.

25. The method of Claim 23, wherein the cover includes a material selected from the group consisting of plastic, fiberglass, leather, fabric, metal, foam, carbon fiber, and combinations thereof.

26. The method of according to any of Claims 22-25, wherein coupling includes coupling with a coupler selected from the group consisting of a chemical fastener, a mechanical fastener, an adhesive, a hook and loop closure, a button, a pin, a bolt, and combinations thereof.

27. The method according to any of Claims 22-26, wherein coupling includes a coupling method selected from the group consisting of fusion, thermoforming, sewing techniques, radio-frequency sealing, ultrasonic welding, thermal impulse sealing, and combinations thereof.

28. The method according to any of the preceding claims, wherein one or more cavities of the plurality of cavities have a shape selected from the group consisting of a channel, a sphere, a hexagon, a cube, and a free shape.

29. The method according to any of the preceding claims, wherein one or more of the expanded foam beads comprise a thermoset.

30. The method according to any of the preceding claims, wherein one or more of the expanded polymer beads comprise a thermoplastic.

31. The method according to any of the preceding claims, wherein one or more of the expanded polymer beads comprise an irreversible foam.

32. The method of Claim 31, wherein the irreversible foam comprises a material selected from the group consisting of expanded polystyrene, expanded polyurethane, expanded polylactic acid, and combinations thereof.

33. The method according to any of the preceding claims, wherein one or more of the expanded polymer beads comprise a reversible foam.

34. The method of Claim 33, wherein the reversible foam comprises a material selected from the group consisting of expanded polypropylene, polyurethane, silicone, latex foam rubber, and combinations thereof.

35. The method according to any of the preceding claims, wherein the molded foam article comprises two or more different polymers.

36. The method of Claim 6, wherein the chemical reaction does not include isocyanate or polyol reactants.

37. A molded foam article manufactured using the method of any of Claims 1 to 36, comprising:

a foam having micro-scale cells; and

a plurality of macro-scale cavities disposed in the foam.

38. The molded foam article of Claim 37, wherein the molded foam article is for applications selected from the group consisting of impact-mitigation, product packaging, head-protection, thermal insulation, sound-absorption, sound-proofing, floatation, and buoyancy.

39. The molded foam article of Claim 37, wherein the molded foam article is a head-protection device.

40. The molded foam article of Claim 39, wherein one or more of the cavities of the plurality of cavities are open on a surface of the head-protection device configured to contact a head of a wearer.

41. The molded foam article of Claim 39, wherein one or more of the cavities of the plurality of cavities are open on a surface of the head-protection device opposite a head of a wearer.

42. The molded foam article according to any of Claims 37 to 41, further comprising a rigid shell coupled to a surface of the molded foam article and covering one or more of the cavities of the plurality of cavities.

43. The molded foam article of Claims 42, wherein the rigid shell includes a material selected from the group consisting of plastic, leather, fabric, metal, foam, and combinations thereof.

44. The molded foam article of Claim 43, wherein the rigid shell includes a plastic material selected from the group consisting of polycarbonate, acrylonitrile butadiene styrene (ABS), carbon fiber, Kevlar, fibreglass, and combinations thereof.

45. The molded foam article of Claim 42, wherein the rigid shell is coupled to the surface of the molded foam article by a coupler selected from the group consisting of a chemical fastener, a mechanical fastener, an adhesive, a hook and loop closure, a button, a pin, a bolt, a screw, and combinations thereof.

46. The molded foam article of Claim 42, wherein the rigid shell is coupled to the surface of the molded foam article by a coupling method selected from the group consisting of fusion, thermoforming, sewing techniques, radio-frequency sealing, ultrasonic welding, thermal impulse sealing, and combinations thereof.

47. The molded foam article of Claim 37, wherein one or more of the expanded foam beads comprise a thermoset.

48. The molded foam article of Claim 37, wherein one or more of the expanded polymer beads comprise a thermoplastic.

49. The molded foam article of Claim 37, wherein one or more of the expanded polymer beads comprise an irreversible foam.

50. The molded foam article of Claim 37, wherein the irreversible foam comprises a material selected from the group consisting of expanded polystyrene, expanded polyurethane, expanded polylactic acid, and combinations thereof.

51. The molded foam article of Claim 37, wherein one or more of the expanded polymer beads comprise a reversible foam.

52. The molded foam article of Claim 37, wherein the reversible foam comprises a material selected from the group consisting of expanded polypropylene, polyurethane, silicone, latex foam rubber, and combinations thereof.

53. The molded foam article of Claim 37, wherein the molded foam article is a first molded foam article, the method further comprising coupling a second molded foam article to the first molded foam article to provide a coupled molded foam article, thereby providing one or more closed cavities disposed within the coupled molded foam article.