Flexible polymer-based material for hot isostatic pressing or warm isostatic pressing molds

Abstract

There is disclosed a sealable, flexible membrane for encapsulating a part to be isostatically pressed at an elevated temperature. The membrane includes at least one first layer of polymeric film having a melting point above the elevated temperature, and at least one second layer disposed on the first layer. The second layer comprising a metal. In one embodiment, the metal comes into contact with the part to be isostatically pressed. The membrane, which typically has a thickness ranging from 10 to about 500 m, and is impermeable to the flow of liquids and gases when sealed, can be used to warm press parts up to about 350 C. and pressures ranging from 5,000 psi to 100,000 psi. Methods to isostatically press parts using this sealable, flexible membrane are also disclosed. Bags made from the sealable, flexible membrane that are used in isostatic presses are also disclosed.

Claims

1. A sealable membrane for encapsulating a part to be isostatically pressed at a temperature up to 350 C., said membrane comprising: at least one first layer of polymeric film having a melting point above 350 C.; at least one second layer disposed on said first layer, said second layer comprising a metal, wherein said membrane has a thickness ranging from 10 to about 500 m, is impermeable to the flow of liquids and gases when sealed and can withstand a temperature of 350 C. without thermal degradation.

2. The membrane of claim 1, wherein said at least one first layer of polymeric film comprises polyethylene, polyester, polyethylene terephthalate (PET), polyamide, or combinations thereof.

3. The membrane of claim 2, wherein said at least one first layer of polymeric film comprises one or more of the following: polyethylene comprising ultrahigh molecular weight polyethylene; polyamide chosen from copolyamides 6/12, copolyamides of polyamide 6 and a partially aromatic polyamide and ternary copolyamides based on polyamide 6, polyamide 11, and polyamide 66, or combinations thereof; and PET that is biaxially oriented.

4. The membrane of claim 1, wherein said metal comprises aluminum, copper, or nickel.

5. The membrane of claim 1, wherein the second layer comes into contact with said part to be isostatically pressed, and comprises a multilayer, metallized material.

6. The membrane of claim 5, wherein the multilayer, metallized material comprises a polyester film layer coated with an aluminum layer.

7. The membrane of claim 5, wherein the multilayer, metallized material has a coefficient of friction below 0.5 s.

8. The membrane of claim 1, further comprising a layer of thermoplastic polymeric adhesive in between the at least one first layer and at least one second layer.

9. The membrane of claim 1, wherein said membrane has a thickness ranging from 20 to 100 m.

10. The membrane of claim 1, wherein said membrane comprises a multilayer structure of at least four layers, said four layers comprising repeating layers of polymer film and metal or metallized film.

11. The membrane of claim 10, wherein the multilayer structure is impervious to aqueous solutions, both acidic and basic.

12. A bag comprising the membrane of claim 1, wherein said bag has at least one opening for placing a part to be pressed therein, said at least one opening having at least one seal that hermetically seals the bag, and optionally a port to allow the bag to be evacuated.

13. The membrane of claim 1, wherein said at least one first layer comprises a laminate of additional thermoplastic films, said additional thermoplastic films chosen from a heat-sealable layer, a gas barrier layer, an anti-stick layer, or a strengthening layer.

14. The membrane of claim 13, wherein said gas barrier layer has an oxygen transmission rate there-through ranging from 0 to 5 cm.sup.3/100 in.sup.2/24 hours.

15. The membrane of claim 13, wherein the anti-stick layer comprises a polytetrafluoroethylene containing material.

16. A bag for encapsulating a part to be isostatically pressed at a temperature up to 350 C., said bag comprising: at least one first layer of polymeric film having a melting point above 350 C.; at least one second layer disposed on said first layer, said second layer comprising a metal, wherein said bag can withstand a temperature of 350 C. without thermal degradation and comprises at least one sealable, open end for receiving the part to be pressed, wherein said at least one sealable, open end forms a hermetic seal that is impermeable to the flow of liquids and gases when sealed.

Description

(1) Exemplary objects and advantages will be set forth in part in the description which follows, or may be learned by practice of the exemplary embodiments. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

(2) The features and advantages of the present invention maybe more fully shown by the following examples, which are provided for purposes of illustration, and are not to be construed as limiting the invention in any way.

(3) The part to be HIPed or WIPed is sized, and two sheets of the disclosed polymer film are cut to be larger than the component. One layer is placed on top of the other, which is followed by a heat sealing step of three (3) sides of the stacked film to create a pocket or envelope that will allow the part to easily slide into it. Alternatively a pre-made bag or tube of lay-flat tube can be used to create bag.

(4) The part can then be inspected to determine if there are any sharp edges that may puncture the bag during processing. If there are sharp edges, they are preferentially rounded off or alternatively covered with a soft tape or rubber over the edges to prevent bag damage.

(5) In an embodiment, fixtures or pads can be custom made to prevent puncturing of the polymer film.

(6) Bag sealer temperature and time are then set to ensure the film is sealed and the layers of polymer fuse together creating a good seal. This is typically predetermined depending bag material and thickness.

(7) Additionally, aluminum foil can be used to prevent sticking of the part to the film and will also provide some barrier to sharp edges of the component. This aluminum foil, which can be used as an interlayer between the part that is being pressed and the heat sealable polymer film, is meant to eliminate or mitigate sticking of the part/powder to the polyester film, such as DuPont's Mylar film. However, low tear strength or ductility associated with some Al foils may require the use of a multiple-layer metalized film.

(8) In one embodiment, the metallized material may comprise metallized polyester films, such as the metallized films sold by Toray, Including Lumlife MS26 Lumirror Polyester Films. These films have a mirror surface finish with a very low coefficient of friction, such as one below 0.5 .sub.s, below 0.4 .sub.s, below 0.3 .sub.s, such as a coefficient of friction ranging from 0.3 .sub.s to 0.5 .sub.s, (as measured by ASTM 1894). In one embodiment, the metallized material comes into contact with said part to be isostatically pressed. As a result, this layer should not stick to the pressed part. In one embodiment, the metallized materials are multilayer structures, such as one comprising a layer of metal, such as Al, Cu or Ni, that is deposited, such as vacuum deposited, on a PET layer, with one or more optional layers there-between. For example, these optional layers may comprise an adhesion assistant layer or an adhesion primer layer.

(9) In one embodiment, a vacuum bag sealer is used to evacuate the bag according to desired conditions. For example, larger components will need more time or in humid conditions more time is needed to degas the space in the bag. Vacuum bag sealers can be used that ensure the latter is capable of effective sealing of higher temperature film, such as Mylar.

(10) After sealing, the bag is again inspected to ensure it can hold a vacuum, as evident by the bag remaining tightly contoured to the part rather than in a relax condition. The later suggest that a bag has leaked or failed to seal properly.

(11) Once satisfied that the bag is hermetically sealed, an oversized bag is made in which the first hermetically sealed bag can be inserted. Again the oversized second bag is vacuumed seal over the first bag. This is a recommended redundancy in the event the primary bag falls. This step can be repeated 2, 3, 4 or more times if further insurance of sealing is required to insure a proper seal, and reduce permeability of gas during processing. The sealed part or component can be then processed in the HIP or WIP system as described herein.

(12) Unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term about. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present disclosure.

(13) Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the invention being indicated by the following claims.