Low density fiber-reinforced plastic composites

• US 4,643,940 A
• Filed: 08/06/1984
• Issued: 02/17/1987
• Est. Priority Date: 08/06/1984
• Status: Expired due to Term

• Current Assignee: Unitika Limited
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Shaw, Ken M., Yalvac, Selim, Wessling, Ritchie A., Yats, Larry D.
• Primary Examiner(s): Thibodeau, Paul J.
• Application Number:
  US06/638,163
• Time in Patent Office: 925 Days
• Field of Search: 428/325, 428/308.4, 428/314.4, 428/315.5, 428/315.7, 428/315.9, 428/910, 428/323, 428/336
• US Class Current: 428/308.4
• CPC Class Codes: B29C 44/10 Applying counter-pressure during expanding
• CPC Class Codes: B29K 2105/14 oriented
• CPC Class Codes: C08J 2323/06 Polyethene
• CPC Class Codes: C08J 9/0085 Use of fibrous compounding ingredients C08J9/0076 takes precedence
• CPC Class Codes: C08J 9/103 Azodicarbonamide
• CPC Class Codes: D21H 25/06 of impregnated or coated paper D21H25/08 takes precedence
• CPC Class Codes: Y10S 428/91 Product with molecular orientation
• CPC Class Codes: Y10T 428/249958 Void-containing component is synthetic resin or natural rubbers
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

This invention is a novel high void volume fiber-reinforced resin composite having a continuous matrix of a thermoplastic resin and from about 10 to 50 percent by weight of randomly oriented short reinforcing fibers. A process for making such low density composites is also disclosed.

Claims

1. A fiber-reinforced composite prepared by an aqueous slurry process and heat expanded in thickness to a void volume of from about 20 to about 90 percent by volume, said composite comprising a continuous matrix comprising a solid thermoplastic resin and, distributed throughout said matrix, from about 10 to 50 percent by weight of the composite of randomly oriented reinforcing fibers wherein said fibers have an average length from about 0.125 to 1.00 inch and an aspect ratio of at least about 40.

2. The composite of claim 1 wherein the fibers comprise glass.

3. The composite of claim 1 wherein said thermoplastic resin comprises polyethylene or polypropylene.

4. The composite of claim 1 wherein said thermoplastic resin comprises a polyvinyl aromatic resin.

5. The composite of claim 1 wherein said continuous matrix further comprises the solids of a polymeric binder.

6. The composite of claim 5 wherein said continuous matrix further comprises the solids of a flocculating agent.

7. The composite of claim 1 wherein said reinforcing fibers comprise from about 20 to 40 percent by weight of the composite.

8. The composite of claim 1 having a void volume from about 30 to 70 percent.

9. The composite of claim 1 wherein said continous fiber reinforced matrix contains at least one shaped low void volume section.

10. The composite of claim 1 or 9 having on each major surface thereof a smooth resin layer from about 0.05 to 1 mil thick.

11. The composite of claim 1 wherein the major portion of voids are open-celled.

12. A fiber-reinforced composite comprising a continuous matrix which comprises a solid the thermoplastic resin and, distributed throughout said matrix, from about 10 to 50 percent by weight of the composite of randomly oriented reinforcing fibers, said fibers having an average length of from about 0.125 to 1.0 inch and an aspect ratio of at least about 40, said matrix having a void volume of from about 20 to about 90 percent by volume and being prepared by heating a densified fiber-reinforced resin sheet to a temperature above the resin'"'"'s softening temperature, whereby the sheet is expanded in a direction perpendicular to that of a plane defined by said sheet.

13. The composite of claim 12 wherein the temperature to which the densified sheet is heated is less than that at which the resin degrades.

14. The composite of claim 12 wherein the temperature to which the densified sheet is heated is less than that at which viscosity of the resin becomes so low that the densified sheet loses its physical shape or integrity.

15. The composite of claim 12 wherein the expanded sheet is cooled below the softening temperature of the resin.