EP0214173A1

EP0214173A1 - Heat recoverable automotive retaining members

Info

Publication number: EP0214173A1
Application number: EP19860901106
Authority: EP
Inventors: Edward Matthew Ramsey; Ceinwen Delia Rowlands; Brian Edward Schott; Dennis Carl Siden
Original assignee: Raychem Corp
Current assignee: Raychem Corp
Priority date: 1985-02-07
Filing date: 1986-02-06
Publication date: 1987-03-18
Also published as: WO1986004542A1; JPS62501695A

Abstract

Organes de retenue thermodéformables pour véhicules automobiles, préparés à partir de polymères semi-cristallins dont la température de transition de l'état vitreux, Tg, est située au-dessus de 25oC.De manière inattendue, ces organes présentent un effort de déformation élevé dans certaines conditions et peuvent supporter les sollicitations intervenant dans un véhicule automobile, ce qui permet de les utiliser, par exemple, comme conduites de retenue, etc., dans des enceintes de moteurs à haute température.Heat-deformable retaining members for motor vehicles, prepared from semi-crystalline polymers whose glass transition temperature, Tg, is situated above 25 ° C. Unexpectedly, these members exhibit a high deformation force in certain conditions and can withstand the stresses occurring in a motor vehicle, which makes it possible to use them, for example, as restraining lines, etc., in high temperature engine enclosures.

Description

HEAT RECOVERABLE AUTOMOTIVE RETAINING MEMBERS

This invention relates to automotive retaining members capable of replacing known metal "Jubilee" hose clips and the like with considerable advantages in terms of weight and installation costs. The "Jubilee"-type retaining members have hitherto been regarded as virtually unparalleled in their ability to withstand the stresses of automotive service, especially in the high temperatures of the engine enclosures of vehicles.

The invention provides an automotive retaining member comprising a dimensionally heat recoverable semi-crystalline material having a glass transition temperature, Tg, above about 25°C, said member having a recovery stress of above about 1100 × (E-1)^0.5 pounds per square inch, wherein E is the unresolved recovery ratio.

The invention thus provides, contrary to expectation, polymeric retaining members, preferably in the form of rings, and preferably comprising polyester or polyamide material, which have surprisingly high resistance to the conditions encountered in automotive service, even in the relatively higher temprature environments in and around the engine enclosure of a vehicle. The retaining members of this invention may thus replace metal clips (or clamps) for holding resi liently deformable articles, especially hoses or other hollow tubular articles, in contact with substantially non-resilient substrates, part of which, for example, may be gripped by an aperture of the hose or other resilient article. Fibers of the polymeric material may be used instead of continuous polymer to form the retaining member, if desired.

A dimensionally heat recoverable article is an article the dimensional configuration of which may be made substantially to change when subjected to heat treatment. Usually these articles recover towards an original shape from which they have previously been deformed but the term "heat-recoverable", as used herein, also includes an article which, on heating, adopts a new configuration, even if it has not been previously deformed.

In their most common form, such articles comprise a heat-shrinkable sleeve made from a polymeric material exhibiting the property of elastic or plastic memory as described, for example, in U.S. Patents 2,027,962; 3,086,242 and 3,597,372. As is made clear in, for example, U.S. Patent 2,027,962, the original dimensionally heat-stable form may be a transient form in a continuous process in which, for example, an extruded tube is expanded, whilst hot, to a dimensionally heat-unstable form but, in other applications, a preformed dimensionally heat-stable article is deformed to a dimensionally heat-unstable form in a separate stage.

Typically, such articles are prepared from po lymers that are capable of being cross-linked, for example, polyethylene, polybutene-1, poly 4-methyl pentene and fluorinated polyolefins for example, ethylene-trifluorochloroethylene copolymers, ethylenetetrafluoroethylene copolymers, and vinylidene fluoride polymers, especially polyvinylidene fluoride, and blends thereof, for example, the fluorinated olefin blends as described and claimed in British Patent No. 1,120,131, and the like.

In the production of heat recoverable articles, from cross-linkable polymers, the polymer material may be cross-linked at any stage in the production of the article that will enhance the desired dimensional recoverability. One manner of producing a heat-recoverable article comprises shaping the polymeric material into the desired heat-stable form, subsequently cross-linking the polymeric material, heating the article to a temperature above the crystalline melting point or, for amorphous materials the softening point, as the case may be, of the polymer, deforming the article and cooling the article whilst in the deformed state so that the deformed state of the article is heat-unstable, whereafter application of heat will cause the article to assume its original heat-stable shape.

Heat recoverable articles from cross-linkable crystalline polymers can be prepared by deforming the uncrosslinked polymer below the crystalline melting point and without cross-linking, cooling the deformed article. Subsequent heating of the article to the deformation temperature causes the article to recover toward the undeformed configuration but it does so with a relatively low recovery stress. As a result such recoverable articles are generally unsuitable for use as mechanical devices, such as couplings, where a high recovery stress is required. Further, the use of such devices requires not only a high recovery stress but that the high stress be maintained after the device has been recovered against the substrate and subsequently cooled to ambient temperature. Heat recoverable devices disclosed in the art do not meet this requirement.

It has been unexpectedly discovered that dimensionally heat-recoverable retaining members of semi-crystalline polymers having a glass transition temperature above about 25ºC, preferably above 120°C, exhibit exceptionally high recovery stress under certain conditions, which recovery stress is subsequently retained and in some instances increased, and the members can withstand conditions encountered in automotive use, as aforementioned.

Another aspect of this invention comprises a method of producing the dimensionally heat-recoverable automotive retaining members comprising

a) heating a shaped article of a semi- crystalline polymer having a glass transition temperature (Tg) above 25 °C to a temperature above the Tg of the polymer;

b) deforming the article; and

c) cooling the article while maintaining the article in the deformed state, thereby producing an article which, when heated to a temperature between Tg and the crystalline melting temperature, Tm, of the polymer, recovers with a recovery stress above about 1100 X (E-1)^0.5 pounds per square inch, wherein E is the unresolved recovery ratio and substantially retains such stress on cooling of the article to a temperature below Tg.

These and other features, aspects and advantages of the present invention will become better understood with reference to the appended claims, the following description and accompanying drawings, where:

FIG. 1 is a graph of the peak values of unresolved recovery stress divided by the expansion stress vs. the difference between the recovery and expansion temperatures for 4 materials useful for preparing articles of the invention and for one material (lowest curve) incapable of providing articles of the present invention;

FIG. 2 is a graph of the unresolved recovery stress after 1 minute at the recovery temperature divided by the expansion stress vs. the difference between the recovery and expansion temperatures for 4 materials useful for preparing articles of the invention and for one material (lowest curve) incapable of providing articles of the present invention; FIG. 3 is a graph of the unresolved recovery stress vs. the unresolved recovery ratio for 4 materials useful for preparing articles of the present invention and for 2 materials (lowest 2 curves) incapable of providing articles of the present invention; and

FIG. 4 is a graph of the unresolved recovery stress vs. percentage recovery for 4 materials useful for preparing articles of the present invention and for 1 material (PE) incapable of providing articles of the present invention.

Detailed Description of the Invention

The heat-recoverable articles of this invention are prepared using a semi-crystalline polymer having a glass transition temperature, Tg, above about 25°C. Preferably the polymer used to make the article has a Tg above about 100 °C , more preferably above 120 °C , and most preferably above about 150°C. The polymer used should be a polymer having crystalline melting temperature of above about 150°C, preferably above about 180°C and most preferably above about 290ºC. Such polymers include for example, polyamides, such as polycaprolactam, nylon 6, and poly(ll-iminoundecanoyl), nylon 11, crystalline polyesters, such as crystalline polyethylene terephthalate, polybutylene terephthalate and the like, other crystalline or crystallizable aromatic polymers, such as polyphenylene sulfide and polyaryl ethers, in particular polyaryl ether ketones. Blends of these polymers with each other and/or with other polymers can also be utilized. Semi-crystalline polyaryl ether ketones are particular ly preferred polymers for the preparation of heat recoverable articles of this invention. Such polymers typically have a glass transition temperature in the range of between about 140°C to about 250°C and a crystalline melting temperature between about 270°C and 450°C.

Polyaryl ether ketones comprise repeat units of the formula:

-O-E-O-E¹-

wherein E and E¹ are aromatic radicals at least one of which is a polynuclear aromatic moiety having two aromatic nuclei joined by a ketone group, the other of E and E¹ is an aromatic moiety containing at least one aromatic ring. The polymer can contain other polynuclear moieties joined by other functional groups such as sulfone, sulfide, alkylene, etc.

Poly(aryl ether ketones) suitable for use in this invention have the repeat units of the formula:

-CO-Ar-CO-Ar'-

wherein Ar and Ar' are aromatic moieties at least one of which contains a diaryl ether linkage forming part of the polymer backbone and wherein both Ar and Ar' are covalently linked to the carbonyl groups through aromatic carbon atoms. Preferably, Ar and Ar' are independently selected from substituted and unsubstituted phenylene and substituted and unsubstituted polynuclear aromatic moieties. The term polynuclear aromatic moieties is used to mean aromatic moieties containing at least two aromatic rings. The rings can be fused, joined by a direct bond or by a linking group. Such linking groups include for example, carbonyl, ether sulfone, sulfide, amide, imide, azo, alkylene, perfluoroalkylene and the like. As mentioned above, at least one of Ar and Ar' contains a diaryl ether linkage.

The phenylene and polynuclear aromatic moieties can contain substituents on the aromatic rings. These substituents should not inhibit or otherwise interfere with the polymerization reaction to any significant extent. Such substitutents include, for example, phenyl, halogen, nitro, cyano, alkyl, 2-alkynyl and the like.

Poly(aryl ether ketones) having the following repeat units (the simplest repeat unit being designated for a given polymer) are preferred:

H

Poly(aryl ether ketones) can be prepared by known methods of synthesis. Preferred poly(aryl ether ketones) can be prepared by Friedel-Crafts polymerization of a monomer system comprising:

I) (i) phosgene or an aromatic diacid dihalide together with

(ii) a polynuclear aromatic comonomer comprising:

(a) H-Ar-O-Ar-H

(b) H-(Ar-O)_n-Ar-H wherein n is 2 or 3

(c) H-Ar-O-Ar-(CO-Ar-O-Ar)_m-H wherein m is 1, 2 or 3

or II) an acid halide of the formula:

H-Ar"-O-[(Ar"-CO)_p-(Ar"-O)_q(Ar"-CO)_r]_k-Ar„_-CO-z wherein Z is halogen, k is 0, 1 or 2, p is 1 or 2, q is 0, 1 or 2 and r is 0, 1 or 2;

or

III) an acid halide of the formula:

H-(Ar"-O)_n-Ar"-Y wherein n is 2 or 3 and Y is CO-Z or CO-Ar"-CO-Z where Z is halogen;

wherein each Ar" is independently selected from substituted or unsubstituted phenylene, and substituted or unsubstituted polynuclear aromatic moieties free of ketone carbonyl or ether oxygen groups, in the presence of a reaction medium comprising:

A) A Lewis acid in an amount of one equivalent per equivalent of carbonyl groups present, plus one equivalent per equivalent of Lewis base, plus an amount effective to act as a catalyst for the polymerization;

B) a Lewis base in an amount from 0 to about 4 equivalents per equivalent of acid halide groups present in the monomer system;

C) a non-protic diluent in an amount from 0 to about 98% by weight, based on the weight of the total reaction mixture.

The aromatic diacid dihalide employed is preferably a dichloride or dibromide. Illustrative diacid dihalides which can be used include, for example

wherein a is 0-4 . Illustrated polynuclear aromatic comonomers which can be used with such diacid dihalides are:

(a) H-Ar"-O-Ar"-H, which includes for example:

(b) H-(Ar"-O)_n-Ar"-H, which include, for example:

and

CH-©

(c) H-Ar"-O-Ar"-(CO-Ar"-O-Ar")_m-H, which includes, for example

and

(d) H-(Ar"-O)_n-Ar"-CO-Ar"-(O-Ar")_m-H which includes, for example:

Monomer systems II and III comprise an acid halide.

(The term acid halide is used herein to refer to a monoacid monohalide.) In monomer system II, the acid halide is of the formula:

H-Ar"-O-[(Ar"-CO)_p-(Ar"-O)_q-(Ar"-CO)_r]k.-Ar"-CO-Z

Such monomers include for example, where k = 0

and where k = 1

In monomer system III, the acid halide is of the formula

H-(Ar"-O)_n-Ar"-Y

Examples of such acid halides include

It is to be understood that combinations of monomers can be employed. For example, one or more diacid dihalides can be used with one or more polynuclear aromatic comonomers as long as the correct stoichiometry is maintained. Further, one or more acid halides can be included. In addition monomers which contain other linkages such as those specified above, can be employed as long as one or more of the comonomers used contains at least one ether oxygen linkage. Such comonomers include for example: which can be used as the sole comonomer with an ether containing diacid dihalide or with phosgene or any diacid dihalide when used in addition to a polynuclear aromatic comonomer as defined in I(ii)(a), I(ii)(b), I(ii)(c) or I(ii)(d). Similarly

can be used as a comonomer together with an ether-containing polynuclear aromatic acid halide or as an additional comonomer together with a monomer system as defined in I.

The monomer system can also contain up to about 30 mole % of a comonomer such as a su lfony l chloride which polymerizes under Friedel-Crafts conditions to provide ketone/sulfone copolymers.

Further details of this process for producing poly(aryl ether ketones) can be found in commonly assigned co-pending U.S. application Serial No. 594,503, filed 31 March 1984, the disclosure of which is incorporated herein by reference. Other processes for preparing these polymers can be found in U.S. Patent Nos. 3,953,400, 3,956,240, 3,928,295, 4,176,222 and 4,320,224.

The extent to which other functional groups can be present depend on the nature of the particular group. For example, if sulfone groups are present the ratio of sulfone to ketone groups generally should be below about 30:70 as polymers containing a higher sulfone content are generally amorphous and non-crystallizable.

Other semi-crystalline aromatic polymers or polymers which can be rendered semi-crystalline include polyphenylene sulfide, polyphenylene ethers, and the like. Blends of these polymers with each other and with other polymers can be used.

As mentioned above, the polymer used in making the heat recoverable articles of this invention is semi-crystalline polymers or polymers capable of being rendered crystalline, that is are crystallizable. To exhibit the except ional recovery stress the polymer should have a crystallinity of above about 5%. The degree of crystallinity varies depending on the particular polymer. It is generally desirable that the crystallinity of the polymer used is at a maximum. However, high recovery stresses can be obtained using semi-crystalline polymers with lower crystallinity. The polymer can be treated, for example by annealing, solvent swelling or the like to increase the crystallinity. The dimensionally heat-recoverable articles of this invention are produced by deforming the polymeric material at a temperature above the glass transition temperature of the polymer but below the melting temperature of the polymer. By the glass transition temperature is meant the temperature which is the approximate midpoint of the temperature range over which a reversible change in the amorphous region of the polymer from (or to) a viscous or rubbery condition to (or from) a hard and relatively brittle one (see ASTM D883). The crystalline melting temperature of the polymer is the temperature at which the last trace of crystallinity disappears as the temperature of the polymer is raised. The glass transition temperature is designated in the specification and claims of this patent application as Tg and the crystalline melting temperature as Tm.

The dimensionally heat-recoverable article is preferably in the form of a ring (not necessarily round) of the polymeric material. Such articles can be produced by conventional techniques such as injection molding, extruding, rotation molding and the like. The article is then rendered dimensionally heat-recoverable by heating the article to a temperature T₁ between Tg and Tm of the polymer then deforming the article, for example, expanding it by passing it over a tapered mandrel or the like resulting in a heat shrinkable article, or compressing it by swaging or the like resulting in a heat expandable article. It is to be noted that when a rod shaped or filamentary article is rendered heat-shrinkable along its long axis, it is also rendered radially heat expandable. The temperature at which the deformation step takes place is preferably about 5°C above Tg of the polymer. Following the deformation step the article is cooled, for example, to a temperature, T₂, below the glass transition temperature of the polymer. Generally the article is cooled to ambient temperature.

Another method of producing the article is to take a film of the polymer, the film being produced by extrusion, casting, or the like. The film is then heated to a temperature between Tg and Tm of the polymer and stretched. While maintained in the stretched configuration the film is cooled, generally to a temperature below the Tg of the polymer. The film can then converted to the dimensionallyrecoverable ring or tubular article, for example, by wrapping it over a mandrel or by otherwise forming it and securing the ends. The article is then removed. Alternatively, the film can be wrapped around the substrate to be covered. On application of heat to a temperature above Tg but below Tm the article recovers with high recovery stress.

Another method of producing a heat-shrinkable article of this invention is to produce a heat-shrinkable fiber of a semi-crystalline aromatic polymer. The fiber can be prepared by conventional spinning techniques, slit film processes and the like. The fiber is heated to a temperature between Tg and Tm of the polymer and stretched by conventional fiber stretching techniques. The fiber is cooled, for example to a temperature below Tg of the polymer. It is to be understood that the fiber (or film or tape as described above) is in itself a heat-recoverable article within the scope of this invention. To form a ring or tubular article the fiber can be wound around a mandrel and the ends thereof secured. The resulting article is removed from the mandrel. Alternatively, the film can be wrapped around the substrate to be covered. Upon application of heat to a temperature between Tg and Tm of the polymer, the article will shrink with a high recovery stress.

The term recovery stress is used herein to mean the recovery stress per unit area exhibited by a heat-recoverable article during constrained or unconstrained recovery. It is generally estimated by measuring the stress necessary to just prevent recovery at the given recovery temperature. Measurement of the recovery stress retention of recovery stress on cooling to room temperature is set forth in more detail hereinafter in the examples.

The term high recovery stress is used herein to mean a recovery stress of at least about 1100 × (E-1)^0.5 pounds per square inch (psi), preferably at least about 1500 × (E-1)^0.5 psi and most preferably 2000 × (E-1), wherein E is the unresolved recovery ratio. The unresolved recovery ratio, E, is equal to R_r/R_o wherein R_r is the size of the heat recoverable article in a direction of recovery andR_o is the size of the article in that direction before the article is rendered heat-recoverable. For the present automotive uses, wherein the item to be retained (e.g. a hose) is usually thicker (e.g. at least twice as thick, often more than three or four times as thick) than the retaining member wall thickness, the ratio E before commencement of any heat recovery is at least 1.5, preferably at least 2, more preferably at least 2-5, and most preferably at least 3.

Orientation of the polymer molecules in the hoop direction of the retaining member (re. "around the ring") is preferable to maximise hoop strength during expansion and gripping force on recovery. In this respect, members made by wrapping and securing suitably oriented fibres or films may be advantageous.

For a heat-shrinkable elongate article, this ratio is the ratio of the length after expansion or during recovery to the original length before expansion. For a thin walled tubular article this ratio is approximately the ratio of the corresponding diameters. For the thick walled tubu lar article this ratio is given by

where x is the ratio of the internal diameter of the heat-recoverable article to the diameter (r_i) of the original article before being rendered heat-recoverable and r_o is the external diameter of the heat recoverable article.

The high recovery stress is exhibited by articles of this invention when the article is constrained from complete recovery, that is, is prevented from recovering to its original dimensions. Generally, the high recovery stress is exhibited when the article is recovered less than 25%, based on the dimension of the deformed article. Preferably the article is prevented by the substrate against which it is recovered from recovery of more than about 20% and particularly more than about 15%, based on the dimension of the deformed article.

The articles of this invention are typically used by recovering the article against a substrate. The article, for example can be used to grip a hose around a pipe over which the end of the hose is fitted. It can also be used to grip a flexible, preferably corrugated, protective housing around moving parts such as steering gear to be protected from dust and/or to retain lubricants.

The following Examples illustrate the recovery stress characteristics obtainable in materials suitable for making the automotive retaining members of this invention.

Example 1

Poly(oxy-p-phenylenecarbonyl-p-phenylene) (Stilan), poly(oxy-p-phenyleneoxy-p-phenylenecarbonyl-p-phenylene) (PEEK), polyethylene terephthalate (PET), poly(lliminoundecanoyl) (nylon 11) and polyethylene (PE) were extruded as tape of about the same thickness (0.03 in.), width (1.5 in.) and melt draw ratio under the conditions described in Table 1. Tapes of the first four polymers, which have glass transition temperatures above 25 °C, were cut into 5 in. × 1/4 in. strips with the long dimension in the extrusion direction and then annealed for the times stated in Table 1 to ensure each polymer was at a significant level of crystallinity. Strips of each polymer were mounted in the jaws of an Instron Tensile Tester and equilibrated for 3 minutes at a temperature 100°C above the Tg of the polymer in a preheated oven before being stretched at a jaw separation speed of 5 in. per minute to give a predetermined expansion. For the polyarylene ether ketones this expansion was 100%. Nylon 11 and crystalline PET undergo necking and drawing at the expansion temperatures selected so these polymers were drawn to their natural draw ratios (that is, to the extent that the entire strip between the jaws had necked). As soon as the desired elongation had been attained, the drawing was stopped and the drawn strip was quenched by placing two pieces of damp sponge in contact with either side of the strip and then removed from the Instron Tensile Tester.

Specimens about 3 in. long were cut from the center of the stretched samples and their cross-sectional areas measured. The specimens were placed in thermally insulated clips of such dimensions that only the ends of the samples projected out, which ends were clamped in an Instron Tensile tester jaws mounted inside the oven which was maintained at the appropriate recovery temperature. The insulating clip was then removed allowing the specimen to rapidly warm up to the oven temperature. The recovery stress exerted by the specimen was measured at its peak value and also after one, two and five minutes after removal of the insulating clip. The values of the true expansion stress at the selected expansion ratio and of the recovery stress at various tempera-tures above the Tg but below the Tm and at the above mentioned times after the specimens were placed in the oven are shown in Table 2.

In figures 1 and 2 the ratio of the recovery stress to the original expansion stress has been plotted as a function of the difference between the temperature of expansion and of recovery. Figure 1 shows the peak values of this ratio and figure 2 the values obtained one minute after the specimens were positioned in the oven. This ratio represents the fraction of the expansion stress that is available at these recovery temperatures and at that expansion ratio. These figures also show the fraction of the expansion stress that is expressed on exposure to the recovery temperature for polyethylene rendered heat recoverable according to the teachings of the prior art as described in Example 2.

Example 2

This example illustrates the teachings of the prior art regarding heat recoverable articles and is outside the scope of the instant invention. The polyethylene tape described in Table 1 was rendered heat recoverable at a temperature of 85°C by the natural draw technique described above (we have found that drawing at 85°C yields heat recoverable articles with the highest recovery stresses). The recovery stress exerted by the polyethylene when maintained at temperatures between 40 and 100°C was at a maximum value of 850 psi at 85°C. A polyethylene strip expanded at 85°C which after cooling to room temperature had an expansion of 100% was heated to 85°C whilst clamped in the jaws of the Instron tester. On cooling down to room temperature the stress was found to increase 9% that is to 930 psi. In another embodiment taught by the prior art, polyethylene terephthalate amorphous tape extruded as described in example 1 was stretched at 100°C this being the maximum temperature that we found could be used without crystallization of the amorphous tape during the drawing. The heat recoverable polyethylene terephthalate when tested as desribed in example 1 achieved a maximum recovery stress of 677 psi at 100 °C recovery temperature after having previously been expanded 555%. In another embodiment outside the scope of this invention a strip of crystalline Stilan was placed in the jaws of an Instron Tensile Tester and elongated at room temperature. We found that the strip necked non-uniformly and broke at a low elongation well before the strip had completely drawn.

Example 3

Strips of crystalline tapes prepared and annealed as described in example 1 were expanded 100% at a temperature 50°C above the Tg of each polymer, cooled to room temperature and specimens cut from the expanded strips were heated to a temperature 50 °C above their Tg while clamped in the jaws of an Instron Tensile tester. Table 3 shows the values of the recovery stress obtained after 1 minute of exposure to the hot oven.

Example 4

Strips of crystalline tapes prepared and annealed as described in example 1 were expanded to various degrees at a temperature 100 °C above the Tg of each polymer and cooled to room temperature. Specimens cut from the expanded strips were then heated to the temperature of expansion while clamped in the jaws of an Instron Tensile tester. Table 4 shows the peak recovery stresss generated within the first five minutes of exposure to the hot oven. Figure 3 shows the peak recovery stress for these specimens plotted as a function of unresolved recovery. The lowest two curves in Figure 3 show the peak recovery stresses observed with materials incapable of use in the present invention (see Table 4, amorphous PET and PE).

Example 5

The expanded specimens of Example 3 were heated to Tg + 50 °C and allowed to shrink to varying degrees, the recovery stress being measured as a function of the degree of recovery. Table 5 shows the values obtained; the variation of shrinkage stress with percent recovery is plotted in figure 4. The recoverable articles of the instant invention exhibit significant recovery stresss after shrinkages of as much as 16% based on the expanded dimensions.

Example 6

The expanded specimens of Example 1 were reheated to their expansion temperature while clamped in the jaws of an Instron Tensile tester then cooled to room temperature in the way described in Example 1, the percentage change in stress on cooling to room temperature being recorded. The results obtained are given in Table 6 and show that heat recoverable articles of the instant invention retain a substantial proportion of or even increase the force which they exert on any substrate they are recovered onto on cooling.

Example 7

Tubular rings of engineering thermoplastics useful in this invention were injection molded using the conditions stated in Table 7, annealed as necessary to develop substantial crystallinity and preheated in an oven for ten minutes at Tg + 50 °C. The preheated rings were removed from the oven and expanded over a mandrel (similarly preheated) as rapidly as possible and quenched in water, then removed from the mandrel. The mandrel size was chosen so that each expanded ring had a diameter twice that of the unexpanded rings after removal from the mandrel. The expanded rings were recovered over tinned copper braid placed on mandrels of varying size so that the braid extended beyond the end of each mandrel. The braid used is typical of that used to electrically shield signal cables used in electronic equipment. The temperature of recovery was the same as that used to expand each ring. Each assembly was allowed to cool to room temperature. The free end of the braid was clamped in one jaw of the Instron Tensile tester and the mandrel in the other. The jaws were separated at a rate of 0.2 in. per minute. The peak force required to pull off the braid is given in table 8. Table 8 also shows the force required to pull of a polyethylene (Marlex 6003) ring expanded at 85°C as taught by the prior art. Table 8 shows that considerably greater force was required to pull of the heat recoverable rings of the instant invention than that required to remove the rings made following a teaching of the prior art.

Example 8

Annealed crystalline rings of Stilan were expanded onto a mandrel at room temperature. In every instance the rings expanded non-uniformly and broke at an elongation of about 30%.

Table 1

Polymer Stilan PEEK PST Nylon-11 Nylon-6 PE

Tradename Marlex 6003

Extruder

Size

Temperature Profile:

Zone 1 360 338 220 230 150°C

Zone 2 360 350 240 250 175 ºC

Zone 3 372 382 260 270 175°C

Zone 4 382 382 260 290 200°C

Die 1 382 388 ºC

Die 2 400 388°C

Clamp 382 388°C

Screw type 1 1 2 2 2

RPM 25 10 45 75 100

Head 3000 1800 N/A N/A N/A N/A

Pressure

Throat On On N/A N/A N/A N/A water

Roller 177 177 38 65 93 °C

Te mperature

Roller Speed N/A 4 FPM N/A N/A N/A N/A

Annealing CO 250 250 125 100 0 N/A

Conditions (hrs ) 4 4 0.5 1 hours N/A

Expansion Tg+100 Tg+100 Tg+100 Tg+100 Tg+100

Teπperature 265 245 175 155 150 85°C

Expansion 2:1 2:1 2.95:1 2.95:1 2: 1 2: 1

(1) Die dimensions were 2 in. × 0,065 in.

(2) Screw type 1 was a linear low density polyethylene screw. Screw type 2 was a low density polyethylene screw.

(3) Nylon 6 was in the form of injection-molded duπtells, ASTM D638 Type TV. For injection molding conditions see Table 7. TABLE 2 Recovery Stress Versus Recovery Temperature

Recovery Temp. Time Stilan PEEK PET Nylon 11 Nylon 6

TE-80 M 6,853 1,211 882

2m 6,906 1,288 882

5m 7,022 1,355 882

TE-50 1m 4,537 8,400 3,012 1,491

2m 4,578 8,476 3,019 1,469

5m 4,603 8,535 3,019 1,413 801

TE-40 1m 2m 5m

TE-20 1m 4,741 9,278 3,303 2,175

2m 4,741 9,351 3,303 2,126

5m 4,741 9,207 3,303 2,056

TE* Peak 4,628 9,349 3,383 2,475

1m 4,476 9,301 2,975 2,406

2m 4,349 9,233 2,924 2,207

5m 4,214 9,099 2,848 2,121 1,981

TE+20 Peak 4,674 9,358 3,328 2,646

1m 3,710 8,559 1,788 1,212

2m 3,621 8,369 1,749 1,057

5m 3,451 8,094 1,696 1,003

TE+50 Peak 4,406 8,875 2,817

1m 2,514 6,496 370

2m 2,408 6,279 358

5m 2,236 5,920 332 198

Expansion Stress 6,104 15,188 5,254 3,266

* TE = Expansion temperature

TABLE 3 Recovery Stress After Expansion at Tg + 50 °C

Expansion Recovery Recovery

Temp.(ºC) Ratio Tamp.(ºC) Stress (psi)

Stilan 215 100% 215 5,653

PEEK 195 100% 195 10,332

PET 125 100% 125 1,933

Nylon 11 105 100% 105 2,039

TABLE 4 Recovery Stress And Expansion

Expansion Recovery Recovery

Polymer Teπo. CC) Elonqation Temp. (°C) Stress (psi)

Stilan 265 100% 265 5,214

265 166% 265 9,531

PEEK 245 100% 245 8,465

245 135% 245 10 ,000

PET 175 225% 175 2,019

175 285% 175 4, 426

175 350% 175 5,063

Nylon 11 155 195% 175 2, 696

155 220% 175 3, 967

155 280% 175 5,417

155 350% 175 7,854

PE 85 100% 85 846

85 370% 85 956

85 880% 85 2,191

Amorphous 100 100% 100 27

PET 100 260% 100 211

100 380% 100 385

100 555% 100 677 TABLE 5 Recovery Stress Versus Percent Shrinkage

Recovery Stress (psi)

Percent Shrink Stilan PEEK PET Nylon 11 PE

0 5,506 10,174 1,794 2,074 887

5 3,472 6,108 1,285 1,220 710

10 2,166 3,062 733 725 556

15 1,209 1,212 307 55

20 433 128 0 0 208

TABLE 6 Change in Recovery Stress on Cboling to Room Teπperature

Expansion Recovery Changes in

Stress on Te mperature Elongation Temperature Cooling

Stilan 265°C 100% 265°C +13%

PEEK 245ºC 100% 245°C +16%

PET 175 °C 200% 175 °C +27%

Nylon 11 155°C 195% 155°C -75%

Nylon 6 150 °C 150% 150°C -20%

Table 7

Molding Conditions

Stilan PEEK PET Nylon 11 PE Nylon 6

Barrel Temperatures (°C)

Rear 380°C 370°C 250°C 190°C 140"C 240°C

Front 395°C 380ºC 260°C 200°C 145°C 260°C

Mold Temperatures (°C)

Sprue Side 200 °C 165°C *cold *cold *cold 45°C

Ejector Side 200ºC 165°C *cold *cold *cold 45°C

Cycle Times (seconds)

Injection 21 21 22 22 22 10 Mold Close 51 51 52 52 52 30_,

Mold Close 04 04 04 04 04 03

Injection Pressure (psi) 1200 1200 1200 1200 1200 800

*Cold-No mold heating used

TABLE 8 Pull-Off Force - Pound/Inch Width

Mandrel Size 0.375 0.395 0.415 0.435 0.455 0.475

Stilan 289 382 484 623 725+

PEEK 277 369 469 642 738+

Pet 115 198 265 399 525 691

Nylon 11 57 86 112 164 233 346

PE (Mar lex 6003 ) 11 21 66 83 108 148

Results are an average of three samples.

* Braid tore before pulling off for all three sam ples .

+ Braid tore before pulling off for 1 sample for PEEK and 2 samples for Stilan.

Claims

We Claim:

1. An automotive retaining member comprising dimensionally heat-recoverable semi-crystalline polymer material having a glass transition temperature, Tg, above about 25°C, said member having a recovery stress of above about 1100 × (E-1)^0.5 pounds per square inch, wherein E is the unresolved recovery ratio.

2. A member in accordance with Claim 1 wherein the said polymer is poly(oxy-p-phenylenecarbonyl-p-phenylene).

3. A member according to Claim 1 wherein the said polymer is a polyester or a polyamide.

4. A member in accordance with Claim 1 in the form of a retaining ring.

5. A member in accordance with Claim 1 or 4 comprising fibers of the said polymeric material.

6. A member according to Claim 1 or 4 dimensionally recovered about a resiliently deformable article so as to retain the article in contact with a substantially non-resilient article in a vehicle.

7. A member according to Claim 6 wherein the deformable article is a hose or other hollow tubular article, an aperture of which is gripped by the retaining member about part of the non-resilient article.

8. An article according to Claim 6 in use inside the engine enclosure of a vehicle.

9. A method of producing a member according to Claim 1 comprising

a) heating a shaped article of a semi-crystalline polymer having a .glass transition temperature, Tg, above 25 °C to a temperature above the Tg of the polymer;

b) deforming the article; and

c) cooling the article while maintaining the article in the deformed state, thereby producing an article which, when heated to a temperature between Tg and the crystalline melting temperature, Tm, of the polymer, recovers with a recovery stress above about 1100 × (E-1)^0.5 pounds per square inch, wherein E is the unresolved recovery ratio, and substantially retains such stress on cooling of the article to ambient temperature.