CA1052302A

CA1052302A - Composite articles

Info

Publication number: CA1052302A
Application number: CA245,001A
Authority: CA
Inventors: Preston D. Liebig; William B. Hurlbut (Sr.)
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1975-05-27
Filing date: 1976-02-04
Publication date: 1979-04-10
Also published as: ZA763073B; IN143043B; DE2623289A1; JPS5235253A

Abstract

Abstract of the Invention Resin bonded composite articles having at least one surface which includes a supplementary liner and/or outer integrally formed therewith and a method of making same are disclosed. A fibrous reinforcing material is partially included in the liner or cover and the structural part of the article forming a mechanical interconnection between the two when the article is cured.

Description

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This inVention rel~tes to reinfoxced plastic articles hav~ng at least one sur~ace ~hich includes a supplQ~entary lining and/or outer coating integrally formed therewith, and a method for producing same. ~ great need exists for pipes, pipe fittings, and other related components which are capable o transporting corrosive or abrasive materials. Past practice ln fabricating such components has included steel or cast pipings and fittings having an abrasion resistant liner bonded to the material wall thereof. Another approach has been the use of resin bonded, fiber reinforced structures, again ~aving an abrasion resistant or corrosion impervious lining bonded to the interior wall. One of the largest problems faced by each of the above mentioned techniques has been in maintaining the integrity of the bond between the inner lining material and the outer structural portion of the pipe. A void or other imperfection in the bond or a tear in the liner almost inevitably would lead to the entry of the material being transported into the space between the liner and the outer shell and eventually partial or sometimes complete separation of the liner from ~he pipe.
According to the present invention, a resin bonded, composite structure comprises a resin bonded structural portion having an inner and an outer ~all; an inner lining contiguous with the inner wall of said structural portionS and a fibrous reinforcing material extending partially into said inner wall of said resin bonded structural portion and partially into said inner lining.

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Pigu~e 1 is ~ cXoss sectional view of a pipe section having an inner lining inte~rall~ interconnected with the pipe wall according to the principle of the invention;
Figure 2 is a vie~ similar to Figure 1 of a pipe having only an outer covering î and Figure 3 is a view similar to Figure 1 of a pipe having both a liner and a cover.
Before proceeding with a detailed description of ~he invention, it should be understood that the ~ords "plastic and "resin" as used in the description of the present inven~ion are considered to be essentially interchangeable. That is, for a particular material the unfabricated or uncured material being the "resin" and the fabricated or cured article a "plastic".
The term plastic i5 meant to include any of the many non-metallic compounds, synthetically produced which can be molded into various forms and hardened for commercial use.
Referring to Figure 1, there is sho~n a section through a cylindrical pipe fabricated according to the principles of the present invention. While a pipe section is used for illustration purposes, it should be understood that other reinforced plastic structures such as pump bodies, valve bodies, etc. may also be fabricated according to the principles which ~ill hereafter be discussed.
Referring to Figure 1, the partial longitudinal cross section of a typical pipe 10 is broken do~n into three generally distinct regions for purposes of explanation; i. e., the inner liner 12, the outer plastic shell 14, and the interface region 16 wherein some form i!
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of fiber reinforcemant material 18 partially included in both the outer plastic shell and the inner liner ~orms a mechanical interlock between the shell and the liner. This mechanical int0rlock results in a unitary structure in which the inner liner and the outer structural shell are not likely to separate from one another. A supplemental reinforcing fiber 20 is provided in the outer plastic shell in this embodiment. This material is typically glass filament or a similar materi~1.
Figure 2 shows another typical pipe section 10' wherein an outer layer 22 of elastomer material or the like has been attached to the base structural shell 14' in a like manner with the fiber reinforcement material 18'.
Figure 3 shows a third pipe section 10" which ha3 been provided with both an inner liner 12' and a protective outer covering 22'. The liner and outer covering are each mechanically interlocked with the structural shell 14" through the fibers 1~" contained in fibrous interface arrangements 16". As in the Figure 1 embodiment, supplementary reinforcing material 20' is provided in the structural 14".
The method of fabricating components according to the present invention may vary depending upon the types of materials used for the liner, the reinforcing material in the interface and the outer plastic shell. The materials selected are dependent, among other considerations, upon the application to which the finished product is to be put. A number of possible materials, their advantages, disadvantages and special characteristics will first be discussed and then representative techniqueæ
for fabricating components according to the invention will be set forth.
The structural shell 1l~ is normally formed from a reinforced plastic material. Typically, a thermosetting resin is used, preferably a polyester, however, epoxies and vinylesters may also be used in piping applications. Typical polyester resins include: Hetron ~o~. 72, 92 and ; 30 197 produced by the Durez Division of Hooker Chemical Company, and ~OS~3~;~
Atlac Nos. 382 and 711 produced by ICI United States, Inc., Specialty Chemicals Division. All of the above resins exhibit good corrosion resistance and ~lso have excellent fire retardant ~ualities. In most applications the plastic outer shell contains some type of reinforcement;
such reinforcement varying depending on the service requirements of the pipe. For piping where internal pressure is to be experienced, fil~nent ~inding with glass filaments is preferably used. For non-pressure applications a hand laid-up shell using glass cloth or woven roving is satisfactory. Also, in some non-pressure applications a thermoplastic non-reinforced outer shell made from, for example, PVC ~Poly Vinyl Chloride) may be used.
The inner liner and/or the outer protective coa-ting, as the case may be, may be made from essentially any material compatable with the interlocXing, attaching feature of the invention. In applications where it is desired to have the inner lining highly abrasion resistant, a soft material of an elastomeric nature i6 preferable. 0~ the many elastomeric materials that have become available to designers and engineers in recent years, the most versatile are those included in a group known as polyurethanes. There are three basic forms in which polyurethanes may be manufactured. The first is a millable gum urethane which may be processed like conventional rubber materials; i.e., it may be milled, calendered, extruded and compression molded. A second form is a thermoplastic material which is handled the same as many other thermoplastics, such as polyethylene and polypropylene. Typical manufacturing processes for the thermoplastic polyurethanes are in~ection molding and transfer molding. The third type is what is known as a liquid cast elastomer. With a liquid material it is possible to produce intricate parts which would be impractical with other materials. The liquid cast polyurethanes are the most versatile of the three types and offer the highest combinations of physical properties.

~o5z3~2 TypicAl of the many commercially available materials which could successfully be used as the inner lining material are the ~llowing elastomers: Solathane 291 available from the Thiokol Chemical Corporation, Cyanoprene D-7 available from the American Cyanamid Corporation, Nordel ~420 and Hytrel available from Dupont Corporation. All of these materials possess good abrasion resistance. Of particular application to the present invention ~re a series of cast polyurethane products manufactured by the McCreary Indu~trial Products Company identified by the trademark Scothane.
Several Plternate embodiments for fabricating components according to the principles of the invention will now be described. One method of fabricating straieht piping sections is to first preform the hollow elastomer inner liner by extruding the elastomeric material through an extrusion die according to conventional techniques. The inter~ace or interlocking material, preferably, a glass mat is then placed about the preformed elastomer tube and thereafter passed through a squeeze die which acts to imbed the reinforcing fiber mat partially into the outer surface of the elastomer material. The outer structural plastic shell is then formed about the elastomer liner/reinforcement material assembly so as to impregnate the outer portion of the reinforcing fiber mat thereby forming the mechanical interlock between the liner and outer structure. Using an uncured plastic resin, the resin would be applied in any accepted fashion to the portion of the fiber interface material not embedded in ; the elastomeric liner and built up until the outer shell was the desired thickness for proper structural integrity. If no additional reinforcing material were desired in the outer shell, the entire structure would then be allowed to cure.
If, however, it was desired to further reinforce the structural portion of the pipe section, the reinforcing material, such as a filament wound gla5s (see Figure 1 numeral 20) or hand laid up glass cloth, would be applied to the outer reinforcing resin prior to curing of the structure.

~:)S'~302 Another technique for forming a pipe structure according to the principles of the invention, is to form the elas-tomer inner liner by centri~ugal casting techniques using a liquid cast elastomer, Scothane 97O5, Por example, would be a material having high abrasion resistance which would be used ~or lining pipes used for transporting fly ash flurry.
Before introducing the liquid elastomer in the centrifugal casting mold, the interface material, such as a glass mat, is placed ~ithin the centrifugal casting appsrstus about the inner surface of the mold ca~ity. The viscosity of the liquid elastomer~ the rotational speed of the centri~gal casting apparatus and other variables in the centrifugal casting process are then controlled so as to assure that the cast elastomer penetrates only partially, to the desired depth in the interface reinforce~ent material thereby leaving a portion o~ the rein~orcing material on its outer surface unimpre~nated with the liquid elastomer so that it may be ~ubsequently impregnated with the plastic resin used in fo~ming the outer structural ~ shell. Forming of the outer structural shell with the plastic resin is ; then carried out in the same manner as described above.
In order to form components having unusual shapes, such as ~oints, fittings, pump bodies, etc. the elastomer inner lining would normally be formed in a static molding or casting operation. Again, the interface reinforcement material, glass mat or the like, would be placed within the molding or casting equipment prior to introduction of the fluid elastomer and the variables of the molding process would be controlled such that the elastomer material would penetrate only partially into the reinforcement material. ~he outer plastic structural shell would then again be ~ormed ~ according to the technique described above.
; In all of the above examples, i~ it is desired to also have an outer protective layer of an elastomer or similar material, a second layer of interface rein~orcing material such as a glass mat may be partially imbedded in the outer surface of the structural plastic layer prior to 10523~2 the curing thereof. ~he outer protective la~er of elastomer or the like is then applied as a liquid, by spray or dipping. The entire structure is then cured and results in an inner elastomer liner and an outer elastomer protective coating bath mechanically interlocked through the interface reinforcement material such that separation of the lining and coating from the structural body would not be likely.
~ hile these preferred embodiments of the invention ha~e been shown and described, it Nill be unaerstood that they are merely illustrative and that changes may be made without departing from the scope of the invention as claimed.
What is claimed is:

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A lined, hollow, resin bonded composite structure comprising: a resin bonded structural portion having an inner and an outer wall; an inner lining contiguous with the inner wall of said structural portion; and a fibrous reinforcing material extending partially into said inner wall of said resin bonded structural portion and partially into said inner lining.

2. A lined resin bonded hollow composite structure accord-ing to claim 1 wherein said structural portion is filament reinforced.

3. A lined resin bonded hollow composite structure according to claim 1 wherein said inner lining is made from an elastomeric material.

4. A lined resin bonded hollow composite structure accord-ing to claim 3 wherein said elastomeric material is a polyester based urethane.

5. A lined resin bonded hollow composite structure according to claim 1 wherein said fibrous reinforcing material comprises a fiber mat.

6. A lined resin bonded hollow composite structure accord-ing to claim 5 wherein said fiber mat is a glass fiber mat.

7. A lined, resin bonded, hollow composite structure according to claim 1 further comprising an outer covering contiguous with the outer wall of said structural portion; and a fibrous reinforcing material extending partially into said outer wall of said resin bonded structural portion and partially into said outer covering.