Patent Description:
<CIT> relates to buffer-tube, core-tube, or slotted-core fiber optic cable components made from an extrudable blend of crystalline polypropylene modified with one or more crosslinked or crosslinkable impact-modifying polymers. <CIT> relates to an anti-fouling, hydrophobic and oleophobic modified PBT composite. <CIT> relates to a composition and a method for preparing a polymer composite article. <CIT> relates to the crosslinking of silane-functionalized polyolefins. <CIT> relates to methods for forming tight buffered cables containing a strippable buffer layer. Materials used in optical fiber buffer tubes need to exhibit a balance of rigidity, flexibility, extrudability and kink resistance. Conventional buffer tubes are primarily composed of extruded polybutylene terephthalate ("PBT") which provides rigidity but is prone to kinking during optical fiber installations. Kinking of the buffer tube is disadvantageous as it may result in damage to optical fibers within the buffer tubes.

A conventional approach to increasing buffer tube flexibility involves blending PBT and polyethylene ("PE"). In such a blend, the PBT provides rigidity and telecommunications grease resistance while the PE imparts flexibility and kink resistance. PBT and PE blends incorporate a compatibilizer to facilitate blending due to the polar nature of polyesters and the non-polar nature of polyolefins. One example of a conventional compatibilizer is maleic anhydride grafted polyethylene ("MAH-g-PE"). <CIT> discloses the use of PBT and PE blends that employ MAH-g-PE as a compatibilizer.

Recently, attempts have been made at replacing extrusion grade PBT (i.e., PBT having a melt flow index of less than <NUM> grams per <NUM> minutes (g/<NUM>. ) at <NUM> and <NUM>) with relatively cheaper injection molding grade PBT (i.e., PBT having a melt flow index of <NUM>/<NUM> minutes (min. ) or greater) in PBT-PE buffer tubes. Use of injection molding grade PBT undesirably decreases the zero-shear viscosity of the PBT-PE blend to less than <NUM> Pascal*seconds (PaS) at <NUM>, thereby reducing extrudability and dimensional stability of the extruded tube. Further, buffer tubes extruded from injection molding grade PBT-PE blends may exhibit kinking and lower crush resistance due to non-uniformity in wall thickness of the tube brought about by reduced dimensional stability.

Accordingly, it would be surprising to discover a PBT-PE blend that exhibits a zero-shear viscosity greater than <NUM> PaS at <NUM> and resists kinking but that utilizes PBT having a melt flow index of greater than <NUM>/<NUM>.

In a first aspect the invention provides the method of claim <NUM>.

The present invention offers a solution to providing a PBT-PE blend that contains PBT having a melt flow index of greater than <NUM>/<NUM>. and yet exhibits a zero-shear viscosity greater than <NUM> PaS at <NUM> and resists kinking.

The present invention is a result of discovering that blending of a crosslinkable silanol-functionalized polyolefin with hydroxy terminated poly(dimethylsiloxane) and a condensation catalyst within injection molding grade PBT creates a polymeric composition with a zero-shear viscosity sufficient to maintain dimensional stability while being extruded. Unexpectedly, crosslinking of the silanol-functionalized polyolefin occurring only as a result of blending and extrusion is sufficient to increase the zero-shear viscosity of the polymeric composition to maintain dimensional stability of the polymeric composition. Also unexpectedly discovered was that polymeric compositions where the crosslinkable silanol-functionalized polyolefin is a minority constituent are still able to attain zero-shear viscosities high enough to enable good extrudability and dimensional stability of the tube. The inventors also discovered that MAH-g-HDPE is able to maintain morphology stability of the mixed phases as the mixture undergoes high shear events such as mixing, remelting and high-speed extrusion despite the cross-linking of the silanol-functionalized polyolefin. Stability of the mixed phase morphology resists phase segregation which otherwise results in kinking and poor mechanical properties of the buffer tube. As such, relatively lower cost injection molding grade PBT can be used to manufacture stable mixtures that can be used in the manufacture of buffer tubes with good mechanical properties that resist kinking.

The present invention is particularly useful for buffer tubes in optical fiber installations.

According to at least one feature of the present disclosure, a method, comprises the steps:.

wherein the blending step further comprises blending <NUM> wt% to <NUM> wt% maleated ethylene-based polymer into the polymeric composition based on a total weight of the polymeric composition.

Reference is made to the accompanying drawing in which:
<FIG> shows a cross-sectional view of a loose buffer tube optical fiber cable.

All ranges include endpoints unless otherwise stated. Subscript values in polymer formulae refer to mole average number of units per molecule for the designated component of the polymer.

Test methods refer to the most recent test method as of the priority date of this document unless a date is indicated with the test method number as a hyphenated two-digit number. References to test methods contain both a reference to the testing society and the test method number. Test method organizations are referenced by one of the following abbreviations: ASTM refers to ASTM International (formerly known as American Society for Testing and Materials); EN refers to European Norm; DIN refers to Deutsches Institut für Normung; and ISO refers to International Organization for Standards.

As used herein, "unimodal" denotes a polymeric material having a molecular weight distribution ("MWD") such that its gel permeation chromatography ("GPC") curve exhibits only a single peak with no discernible second peak, or even a shoulder or hump, relative to such single peak. In contrast, as used herein, "bimodal" means that the MWD in a GPC curve exhibits the presence of two component polymers, such as by having two peaks or where one component may be indicated by a hump, shoulder, or tail relative to the peak of the other component polymer.

As used herein, the term weight percent ("wt%") designates the percentage by weight a component is of a total weight of the polymeric composition unless otherwise specified.

The polymeric composition of the present invention includes a silanol-functionalized polyolefin, polybutylene terephthalate, a condensation catalyst, hydroxy terminated poly(dimethylsiloxane), and a maleated ethylene-based polymer. As will be explained in greater detail below, the polymeric composition may also include a high-density polyethylene. Such polymeric compositions can be extruded to form optical fiber cable protective components such as buffer tubes.

The polymeric composition comprises a silanol-functionalized polyolefin. A "silanol-functionalized polyolefin" is a polymer that contains silane and equal to or greater than <NUM> wt %, or a majority amount, of polymerized α-olefin, based on the total weight of the silanol-functionalized polyolefin. "Polymer" means a macromolecular compound prepared by reacting (i.e., polymerizing) monomers of the same or different type. As noted above, the polymeric composition comprises the silanol-functionalized polyolefin. The silanol-functionalized polyolefin crosslinks and in doing so increases the viscosity of the polymeric composition. The increased viscosity of the polymeric composition enables extrusion of the polymeric composition.

The silanol-functionalized polyolefin may include an α-olefin and silane copolymer, a silane-grafted polyolefin, and/or combinations thereof. An "α-olefin and silane copolymer" is formed from the copolymerization of an α-olefin (such as ethylene) and a hydrolyzable silane monomer (such as a vinyl silane monomer) such that the hydrolyzable silane monomer is incorporated into the backbone of the polymer chain prior to the polymer's incorporation into the polymeric composition. A "silane-grafted polyolefin" or "Si-g-PO" may be formed by the Sioplas process in which a hydrolyzable silane monomer is grafted onto the backbone of a base polyolefin by a process such as extrusion, prior to the polymer's incorporation into the polymeric composition.

In examples where the silanol-functionalized polyolefin is an α-olefin/silane copolymer, the silanol-functionalized polyolefin is prepared by the copolymerization of at least one α-olefin and a hydrolyzable silane monomer. In examples where the silanol-functionalized polyolefin is a silanol grafted polyolefin, the silanol-functionalized polyolefin is prepared by grafting one or more hydrolyzable silane monomers on to the α-olefin backbone.

The silanol-functionalized polyolefin comprises <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, while at the same time, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less of α-olefin as measured using Fourier-Transform Infrared (FTIR) Spectroscopy. The α-olefin may include C<NUM>, or C<NUM> to C<NUM>, or C<NUM>, or C<NUM>, or C<NUM>, or C<NUM>, or C<NUM>, or C<NUM>, or C<NUM> α-olefins, such as ethylene, propylene, <NUM>-butene, <NUM>-hexene, <NUM>-methyl-<NUM>-pentene, and <NUM>-octene.

The silanol-functionalized polyolefin may comprise <NUM> wt% or greater, or <NUM> wt%, or <NUM> wt%, or <NUM> wt%, or <NUM> wt % to <NUM> wt %, or <NUM> wt %, or <NUM> wt %, or <NUM> wt %, while at the same time, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt%, or <NUM> wt% or less of silane as measured using FTIR Spectroscopy.

The silanol-functionalized polyolefin has a density from <NUM> grams per cubic centimeter (g/cc), or <NUM>/cc, or <NUM>/cc, or <NUM>/cc, or <NUM>/cc, or <NUM>/cc to <NUM>/cc, or <NUM>/cc, while at the same time, <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less as measured by ASTM D792.

A "hydrolyzable silane monomer" is a silane-containing monomer that will effectively copolymerize with an α-olefin (e.g., ethylene) to form an α-olefin/silane copolymer (such as an ethylene/silane reactor copolymer), or graft to and crosslink an α-olefin polymer (i.e., a polyolefin) to form a reactor Si-g-polyolefin. The hydrolyzable silane monomer has structure (I):
<CHM>
in which R<NUM> is a hydrogen atom or methyl group; x is <NUM> or <NUM>; n is an integer from <NUM> to <NUM>, or <NUM>, or <NUM>, or <NUM>, or <NUM>; and each R<NUM> independently is a hydrolyzable organic group such as an alkoxy group having from <NUM> to <NUM> carbon atoms (e.g., methoxy, ethoxy, butoxy), an aryloxy group (e.g., phenoxy), an araloxy group (e.g., benzyloxy), an aliphatic acyloxy group having from <NUM> to <NUM> carbon atoms (e.g., formyloxy, acetyloxy, propanoyloxy), an amino or substituted amino group (e.g., alkylamino, arylamino), or a lower-alkyl group having <NUM> to <NUM> carbon atoms, with the proviso that not more than one of the three R<NUM> groups is an alkyl. The hydrolyzable silane monomer may be copolymerized with an α-olefin (such as ethylene) in a reactor, such as a high-pressure process to form an α-olefin-silane reactor copolymer. In examples where the α-olefin is ethylene, such a copolymer is referred to herein as an ethylene-silane copolymer. The hydrolyzable silane monomer may also be grafted to a polyolefin (such as a polyethylene) by the use of an organic peroxide, such as <NUM>,<NUM>-bis(tert-butylperoxy)-<NUM>,<NUM>-dimethylhexane, to form a reactor Si-g-PO or an in-situ Si-g-PO.

The hydrolyzable silane monomer may include silane monomers that comprise an ethylenically unsaturated hydrocarbyl group, such as a vinyl, allyl, isopropenyl, butenyl, cyclohexenyl or gamma (meth)acryloxy allyl group, and a hydrolyzable group, such as, for example, a hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino group. Hydrolyzable groups may include methoxy, ethoxy, formyloxy, acetoxy, proprionyloxy, and alkyl or arylamino groups. In a specific example, the hydrolyzable silane monomer is an unsaturated alkoxy silane, which can be grafted onto the polyolefin or copolymerized in-reactor with an α-olefin (such as ethylene). Examples of hydrolyzable silane monomers include vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), vinyltriacetoxysilane, and gamma-(meth)acryloxy propyl trimethoxy silane.

Examples of suitable ethylene-silane copolymers are commercially available as SI-LINK™ DFDA-<NUM> NT and SI-LINK™ AC DFDB-<NUM> NT, each available from The Dow Chemical Company, Midland, Mich.

The PBT can have a density in the range of from <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, while at the same time, <NUM>/cc or less, <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less as measured by ASTM D792.

The PBT can be an extrusion-grade PBT or an injection-molding-grade PBT. Injection-molding-grade PBTs are typically characterized by having lower molecular weight, as evidenced by relatively higher melt indices. The PBT can have a melt index (I<NUM>) of <NUM>/<NUM>. or greater, or <NUM>/<NUM>. or greater, while at the same time, <NUM>/<NUM>. or less, or <NUM>/<NUM>. or less, or <NUM>/<NUM>. or less, as measured according to ASTM method D1238. Melt indices for PBT are determined at <NUM> and <NUM> (i.e., I<NUM>).

Examples of suitable commercially available extrusion-grade PBTs include, but are not limited to, PBT-<NUM> from Suzhou Yingmao Plastics Company, Jiangsu, China; ULTRADUR™ BN6550 from BASF, Ludwigshafen, Germany; CRASTIN™ <NUM> NC010 from DuPont, Wilmington, Delaware, USA; and PBT VALOX™ <NUM> from Sabic Innovative Plastics, Pittsfield, Massachusetts, USA. An example of a suitable commercially available injection-molding-grade PBT includes, but is not limited to, CRASTIN™ <NUM> from DuPont, Wilmington, Delaware, USA.

The polymeric composition comprises from <NUM> wt% to <NUM> wt% PBT. The polymeric composition may comprise <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, while at the same time, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less,or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less of PBT.

The polymeric composition comprises a condensation catalyst. The condensation catalyst catalyzes the crosslinking of the silanol-functionalized polyolefin. The condensation catalyst can be any compound that catalyzes a moisture crosslinking reaction with hydrolysable silane groups. Condensation catalysts can include carboxylates of metals, such as tin, zinc, iron, lead, and cobalt; organic bases, inorganic acids, and organic acids. Examples of such catalysts include, but are not limited to, dibutyltin dilaurate ("DBTDL"), dibutyltin diacetate, dioctyltin dilaurate, stannous acetate, stannous caprylate, lead naphthenate, zinc caprylate, cobalt naphthenate, ethyl amines, dibutyl amine, hexylamines, pyridine, inorganic acids, such as sulphuric acid and hydrochloric acid, as well as organic acids, such as sulfonic acids (e.g., toluene sulfonic acid), acetic acid, stearic acid and maleic acid. In various embodiments, the catalyst is selected from a tin-based catalyst and a sulfonic acid. In still other embodiments, the catalyst can be a tin carboxylate. Furthermore, in certain embodiments, the catalyst is DBTDL. The catalyst can be employed neat or as part of a masterbatch. Such a masterbatch may additionally include, for example, a polyolefin carrier (e.g., polyethylene), an antioxidant, and/or a metal deactivator.

The polymeric composition may comprise <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, while at the same time, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less of condensation catalyst.

The condensation catalyst may be added to the polymeric mixture as part of a catalyst masterbatch blend. Examples of suitable catalyst masterbatches are commercially available under the trade name SI-LINK™ from The Dow Chemical Company, including SI-LINK™ DFDA-<NUM> Natural and SI-LINK™ AC DFDA-<NUM> NT. SI-LINK™ AC DFDA-<NUM> NT is a catalyst masterbatch containing a blend of a thermoplastic polymer, a phenolic compound antioxidant, and a hydrophobic acid catalyst (a silanol condensation catalyst). The polymeric composition may comprise from <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt % or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, while at the same time, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less of catalyst masterbatch based on total weight of the polymeric composition.

The polymeric composition comprises hydroxyl-terminated poly(dimethylsiloxane) (PDMS). PDMS comprises units of the formula R<NUM>SiO in which each radical R is methyl. PDMS may have structure (II):
<CHM>
in which Me is methyl and n is a number sufficient to impart a number average molecular weight (Mn) to the PDMS of greater than or equal to (>) <NUM>,<NUM>. The upper value of n may be <NUM>,<NUM> or less, or <NUM>,<NUM> or less, or <NUM>,<NUM> or less, or <NUM> or less as measured by gel permeation chromatography (GPC). Such polydimethylsiloxanes are commercially available as XIAMETER™ PMX-<NUM> silanol fluid available from The Dow Chemical Company, Midland, MI, USA.

As noted above, the polymeric composition comprises a maleated ethylene-based polymer. As used herein, the term "maleated" indicates a polymer (e.g., an ethylene-based polymer) that has been modified to incorporate a maleic anhydride monomer. Maleated ethylene-based polymer can be formed by copolymerization of maleic anhydride monomer with ethylene and other monomers (if present) to prepare an interpolymer having maleic anhydride incorporated into the polymer backbone. Additionally, or alternatively, the maleic anhydride can be graft-polymerized to the ethylene-based polymer. The above-noted description of ethylene-based polymer is equally applicable to the maleated ethylene-based polymer.

The maleated ethylene-based polymer can have a density of <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, or <NUM>/cc or greater, <NUM>/cc or greater, while at the same time, <NUM>/cc or less, or <NUM>/cc or less, or <NUM>/cc or less as measured by ASTM D792.

The maleated ethylene-based polymer can have a melt index (I<NUM>) ranging from <NUM> to <NUM>/<NUM>. , from <NUM> to <NUM>/<NUM>. , or from <NUM> to <NUM>/<NUM> at <NUM> and <NUM>.

The maleated ethylene-based polymer can have a maleic anhydride content, based on the total weight of the maleated ethylene-based polymer, of <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, while at the same time, <NUM> wt% or less, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less. Maleic anhydride concentrations are determined by Titration Analysis. Titration Analysis is performed by utilizing dried resin and titrates with <NUM>. 02N KOH to determine the amount of maleic anhydride. The dried polymers are titrated by dissolving <NUM> to <NUM> grams of maleated polymer in about <NUM> of refluxing xylene. Upon complete dissolution, deionized water (four drops) is added to the solution and the solution is refluxed for <NUM> hour. Next, <NUM> % thymol blue (a few drops) is added to the solution and the solution is over titrated with <NUM>. 02N KOH in ethanol as indicated by the formation of a purple color. The solution is then back-titrated to a yellow endpoint with <NUM>. 05N HCl in isopropanol.

The polymeric composition may comprise from <NUM> wt% to <NUM> wt% maleated ethylene-based polymer. For example, the polymeric composition may comprise <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, while at the same time, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less.

Examples of suitable commercially available maleated ethylene-based polymer include, but are not limited to, AMPLIFY™ TY1053H, AMPLIFY™ GR204, and AMPLIFY™ GR205 available from The Dow Chemical Company, Midland, MI, USA; BYNEL™ <NUM> series and FUSABOND™ P series products, available from DuPont, Wilmington, DE, USA; OREVAC™ grafted polyethylenes, available from Arkema, Colombes, France; and POLYBOND™ <NUM> series, available from Addivant, Danbury, CT, USA.

The polymeric composition may comprise high-density polyethylene ("HDPE"). HDPE is an ethylene-based polymer having a density of at least <NUM>/cc, or from at least <NUM>/cc to <NUM>/cc as measured by ASTM D792. HDPE has a melt index from <NUM>/<NUM> to <NUM>/<NUM>. HDPE can include ethylene and one or more C <NUM>-C <NUM> α-olefin comonomers. The comonomer(s) can be linear or branched. Nonlimiting examples of suitable comonomers include propylene, <NUM>-butene, <NUM> pentene, <NUM>-methyl-<NUM>-pentene, <NUM>-hexene, and <NUM>-octene. HDPE can be prepared with either Ziegler-Natta, chromium-based, constrained geometry or metallocene catalysts in slurry reactors, gas phase reactors or solution reactors. The ethylene/C <NUM>-C <NUM> α-olefin comonomer includes at least <NUM> wt% ethylene polymerized therein, or at least <NUM> wt%, or at least <NUM> wt%, or at least <NUM> wt%, or at least <NUM> wt%, or at least <NUM> wt% ethylene in polymerized form. In an embodiment, the HDPE is an ethylene/α-olefin copolymer with a density from <NUM>/cc to <NUM>/cc, and a melt index (I<NUM>) from <NUM>/<NUM> to <NUM>/<NUM>. In an embodiment, the HDPE has a density from <NUM>/cc to <NUM>/cc, and a melt index from <NUM>/<NUM> to <NUM>/<NUM>. Nonlimiting examples of suitable HDPE are commercially available ELITE™ <NUM>, HDPE KT <NUM> UE™, HDPE KS <NUM> UE™, HDPE 35057E™, and AXELERON™ CX-A-<NUM> NT, each available from The Dow Chemical Company Midland, Michigan, USA.

The HDPE may be unimodal or bimodal. In other embodiments, the HDPE is bimodal. Exemplary preparation methods for making unimodal HDPE can be found, for example, in <CIT> or <NUM>,<NUM>,<NUM>. An example of a commercially available unimodal HDPE includes, but is not limited to, DGDL-3364NT™, available from The Dow Chemical Company, Midland, MI, USA.

The polymeric composition can comprise a bimodal HDPE. A bimodal HDPE comprises a first polymeric component and a second polymeric component. The first component can be an ethylene-based polymer; for example, the first component can be a high-molecular-weight ethylene homopolymer or ethylene/alpha-olefin copolymer. The first component may comprise any amount of one or more alpha-olefin copolymers. For example, the first component can comprise less than <NUM> wt% of one or more alpha-olefin comonomers, based on the total first component weight. The first component may comprise any amount of ethylene; for example, the first component can comprise at least <NUM> wt% of ethylene, or at least <NUM> wt% of ethylene, based on the total first component weight. The alpha-olefin comonomers present in the first component of the bimodal HDPE typically have no more than <NUM> carbon atoms. For example, the alpha-olefin comonomers may have from <NUM> to <NUM> carbon atoms, or from <NUM> to <NUM> carbon atoms. Exemplary alpha-olefin comonomers include, but are not limited to, propylene, <NUM>-butene, <NUM>-pentene, <NUM>-hexene, <NUM>-heptene, <NUM>-octene, <NUM>-nonene, <NUM>-decene, and <NUM>-methyl-<NUM>-pentene. In an embodiment, the alpha-olefin comonomers can be selected from the group consisting of propylene, <NUM>-butene, <NUM>-hexene, and <NUM>-octene. In other embodiments, the alpha-olefin comonomers can be selected from the group consisting of <NUM>-hexene and <NUM>-octene.

The first component of the bimodal HDPE can have a density in the range of from <NUM>/cc to <NUM>/cc, from <NUM>/cc to <NUM>/cc, or from <NUM>/cc to <NUM>/cc. The first component can have a melt index (I<NUM>) (<NUM>/<NUM>), in the range of from <NUM><NUM>/<NUM>. to <NUM>/<NUM>. , from <NUM><NUM>/<NUM>. to <NUM>/<NUM>. , or from <NUM><NUM>/<NUM>. to <NUM>/<NUM>. The first component can have a molecular weight in the range of from <NUM>,<NUM> grams per mol (g/mol) to <NUM>,<NUM>/mol, from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, or from <NUM>,<NUM>/mol to <NUM>,<NUM>/mol.

The second polymeric component of the bimodal HDPE can be an ethylene-based polymer. For example, the second component can be a low-molecular-weight ethylene homopolymer. The ethylene homopolymer may contain trace amounts of contaminate comonomers, for example alpha-olefin comonomers. In various embodiments, the second component can comprise less than <NUM> wt% of one or more alpha-olefin comonomers, based on the weight of the second component. For example, the second component may comprise from <NUM> to <NUM> wt% of one or more alpha-olefin comonomers, or from <NUM> to <NUM> wt% of one or more alpha-olefin comonomers. The second component can comprise at least <NUM> wt% of ethylene, or in the range of from <NUM> wt% to <NUM> wt% of ethylene, based on the weight of the second component.

The second component of the bimodal HDPE can have a density in the range of from <NUM>/cc to <NUM>/cc, or from <NUM>/cc to <NUM>/cc. The second component can have a melt index (I<NUM>) in the range of from <NUM>/<NUM> to <NUM>,<NUM>/<NUM>. , from <NUM>/<NUM> to <NUM>,<NUM>/<NUM>. , or from <NUM>/<NUM> to <NUM>,<NUM>/<NUM>. The second component can have a molecular weight in the range of <NUM>,<NUM> to <NUM>,<NUM>/mol, from <NUM>,<NUM> to <NUM>,<NUM>/mol, or from <NUM>,<NUM> to <NUM>,<NUM>/mol.

A suitable preparation method for making bimodal HDPE can be found, for example, in <CIT>, paragraphs [<NUM>] to [<NUM>].

Examples of a commercially available bimodal HDPE include, but are not limited to, DMDA-1250NT™ and DMDC <NUM>™, both available from The Dow Chemical Company, Midland, MI, USA.

The polymeric composition may comprise <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, or <NUM> wt% or greater, while at the same time, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less, or <NUM> wt% or less or less of HDPE.

The polymeric composition can include one or more particulate fillers, such as glass fibers or various mineral fillers including nano-composites. Fillers, especially those with elongated or platelet-shaped particles providing a higher aspect ratio (length/thickness), may improve modulus and post-extrusion shrinkage characteristics. The filler(s) can have a median size or d<NUM>% of less than <NUM>, less than <NUM>, or less than <NUM>. The fillers may be surface treated to facilitate wetting or dispersion in the polymeric composition. Specific examples of suitable fillers include, but are not limited to, calcium carbonate, silica, quartz, fused quartz, talc, mica, clay, kaolin, wollastonite, feldspar, aluminum hydroxide, carbon black, and graphite. Fillers may be included in the polymeric composition in an amount ranging from <NUM> wt% to <NUM> wt%, or from <NUM> wt% to <NUM> wt% based on the total weight of the polymeric composition.

The polymeric composition may comprise a nucleating agent. Examples of suitable nucleating agents include ADK NA-<NUM> nucleating agent, available commercially from Asahi Denim Kokai, and HYPERFORM HPN-20E™ nucleating agent, available from Milliken Chemical. The nucleating agents can be included in the polymeric composition in amounts ranging from <NUM> wt% to <NUM> wt%, from <NUM> wt% to <NUM> wt%, or from <NUM> to <NUM> wt% based on the total polymeric composition weight.

The polymeric composition may comprise additional additives in the form of antioxidants, cross-linking co-agents, cure boosters and scorch retardants, processing aids, coupling agents, ultraviolet stabilizers (including UV absorbers), antistatic agents, additional nucleating agents, slip agents, lubricants, viscosity control agents, tackifiers, anti-blocking agents, surfactants, extender oils, acid scavengers, flame retardants and metal deactivators. The polymeric composition may comprise from <NUM> wt% to <NUM> wt% of one or more of the additional additives.

The UV light stabilizers may comprise hindered amine light stabilizers ("HALS") and UV light absorber ("UVA") additives. Representative UVA additives include benzotriazole types such as TINUVIN <NUM>™ light stabilizer and TINUVIN <NUM>™ light stabilizer commercially available from Ciba, Inc. Blends of HAL's and UVA additives are also effective.

The antioxidants may comprise hindered phenols such as tetrakis[methylene(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxyhydro-cinnamate)]methane; bis[(beta-(<NUM>,<NUM>-ditert-butyl-<NUM>-hydroxybenzyl) methylcarboxyethyl)]-sulphide, <NUM>,<NUM>'-thiobis(<NUM>-methyl-<NUM>-tert-butylphenol), <NUM>,<NUM>'-thiobis(<NUM>-tert-butyl-<NUM>-methylphenol), <NUM>,<NUM>'-thiobis(<NUM>-methyl-<NUM>-tert-butylphenol), and thiodiethylene bis(<NUM>,<NUM>-di-tert-butyl-<NUM>-hydroxy)-hydrocinnamate; phosphites and phosphonites such as tris(<NUM>,<NUM>-di-tert-butylphenyl)phosphite and di-tert-butylphenyl-phosphonite; thio compounds such as dilaurylthiodipropionate, dimyristylthiodipropionate, and distearylthiodipropionate; various siloxanes; polymerized <NUM>,<NUM>,<NUM>-trimethyl-<NUM>,<NUM>-dihydroquinoline, n,n'-bis(<NUM>,<NUM>-dimethylpentyl-p-phenylenediamine), alkylated diphenylamines, <NUM>,<NUM>'-bis(alpha, alphadimethylbenzyl)diphenylamine, diphenyl-p-phenylenediamine, mixed di-aryl-p-phenylenediamines, and other hindered amine anti-degradants or stabilizers.

The processing aids may comprise metal salts of carboxylic acids such as zinc stearate or calcium stearate; fatty acids such as stearic acid, oleic acid, or erucic acid; fatty amides such as stearamide, oleamide, erucamide, or N,N'-ethylene bis-stearamide; polyethylene wax; oxidized polyethylene wax; polymers of ethylene oxide; copolymers of ethylene oxide and propylene oxide; vegetable waxes; petroleum waxes; non-ionic surfactants; silicone fluids and polysiloxanes.

The components of the polymeric composition except the PBT and condensation catalyst can be added to a batch or continuous mixer for melt blending to form a melt-blended composition. The components can be added in any order or first preparing one or more masterbatches for blending with the other components. The melt blending may be conducted at a temperature above the highest melting polymer but lower than the maximum compounding temperature of <NUM>. The melt-blended composition is then delivered to an extruder or an injection-molding machine or passed through a die for shaping into the desired article, or converted to pellets, tape, strip or film or some other form for storage or to prepare the material for feeding to a next shaping or processing step. Optionally, if shaped into pellets or some similar configuration, then the pellets, etc. can be coated with an anti-block agent to facilitate handling while in storage.

Examples of compounding equipment used include internal batch mixers, such as a BANBURY or BOLLING internal mixer. Alternatively, continuous single, or twin screw, mixers can be used, such as FARRELL continuous mixer, a WERNER and PFLEIDERER twin screw mixer, or a BUSS kneading continuous extruder. The type of mixer utilized, and the operating conditions of the mixer, will affect properties of the composition such as viscosity, volume resistivity, and extruded surface smoothness.

The melt blended composition is then mixed with the PBT and the condensation catalyst in an extruder to blend the polymeric composition. With the blended polymeric composition now including the condensation catalyst and the silanol-functionalized polyolefin, the silanol-functionalized polyolefin begins to crosslink and increase the viscosity of the blended polymeric composition. The extrusion of the polymeric composition may begin immediately or may be delayed for <NUM> minute, or <NUM> minutes, or <NUM> minutes, or <NUM> minutes or <NUM> hours from the initiation of blending. The polymeric composition is then extruded to form one or more components.

The polymeric composition may exhibit a flexural modulus of <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, or <NUM>,<NUM> MPa or greater, while at the same time, <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPA or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPa or less, or <NUM>,<NUM> MPA or less. The flexural modulus is determined according to the procedure described in the Test Methods section, below.

In various embodiments, particularly in embodiments where the polymeric composition is intended for use in buffer tubes containing a hydrocarbon filling compound, the polymeric composition can exhibit a weight increase of less than <NUM> wt%, less than <NUM> wt%, less than <NUM> wt%, or less than <NUM> wt% when immersed in INFOGEL™ LA <NUM> filling compound (a fiber-optic-cable buffer-tube filling compound). INFOGEL™ LA <NUM> filling compound is composed of at least about <NUM> wt% mineral oil and up to about <NUM> wt% styrene-butadiene-styrene block copolymer, and is commercially available from Honghui Corp.

The polymeric composition may exhibit a melt index (I<NUM>) of <NUM> to <NUM>/<NUM>. at <NUM> and <NUM>. For example, the melt flow index can be <NUM>/<NUM>. or greater, or <NUM> /<NUM>. or greater, or <NUM>/<NUM>. or greater, or <NUM> /<NUM>. or greater, or <NUM>/<NUM>. or greater, or <NUM> /<NUM>. or greater, or <NUM>/<NUM>. or greater, or <NUM> /<NUM>. or greater, or <NUM>/<NUM>. or greater, or <NUM> /<NUM>. or greater, or <NUM>/<NUM>. or greater, or <NUM> /<NUM>. or greater, or <NUM>/<NUM>. or greater, or <NUM> /<NUM>. or greater, while at the same time, <NUM>/<NUM>. or less, or <NUM>/<NUM>. or less, or <NUM>/<NUM>. or less, or <NUM>/lOmin. or less, or <NUM>/lOmin. or less, or <NUM>/lOmin. or less, or <NUM>/lOmin. or less, or <NUM>/<NUM>. or less, or <NUM>/lOmin. or less, or <NUM>/<NUM>. or less, or <NUM>/<NUM>. or less, or <NUM>/lOmin. or less, or <NUM>/<NUM>. or less, or <NUM>/lOmin.

The polymeric composition may exhibit a zero-shear viscosity at <NUM> of <NUM> PaS or greater, or <NUM> PaS or greater, or <NUM>,<NUM> PaS or greater, or <NUM>,<NUM> PaS or greater, or <NUM>,000PaS or greater, or <NUM>,<NUM> PaS or greater, or <NUM>,<NUM> PaS or greater, or <NUM>,<NUM> PaS or greater, while at the same time, <NUM>,<NUM> PaS or less, or <NUM>,<NUM> PaS or less, or <NUM>,<NUM> PaS or less, or <NUM>,<NUM> PaS or less, or <NUM>,<NUM> PaS or less, or <NUM>,<NUM> PaS or less, or <NUM>,<NUM> PaS or less, or <NUM> PaS or less. The test method for zero-shear viscosity is detailed below.

The polymeric composition may exhibit a break stress of <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, while at the same time, <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPA or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPA or less, or <NUM> MPa or less, or <NUM> MPa or less. The test method for break stress is detailed below.

The polymeric composition may exhibit a tube crush strength of <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, or <NUM> MPa or greater, while at the same time, <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPA or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPa or less, or <NUM> MPA or less. The test method for tube crush strength is detailed below.

Referring now to <FIG>, depicted is a cross-sectional view of an exemplary optical fiber cable <NUM>. In the depicted example, the optical fiber cable <NUM> is a "loose buffer tube" design. In such a cable design, buffer tubes <NUM> are positioned radially around a central strength member <NUM>, with a helical rotation to the buffer tubes <NUM> along an axial length of the optical fiber <NUM>. The helical rotation of the buffer tubes <NUM> allow bending of the cable without significantly stretching the tube or the optical fibers <NUM>. If a reduced number of buffer tubes <NUM> is required, then foamed filler rods can be used as spacers to occupy one or more buffer tube positions <NUM> to maintain geometry of the cable <NUM>. A cable jacket <NUM> is generally fabricated from a polyethylene-based material. The buffer tubes <NUM> may comprise, consist or consist essentially of the polymeric composition. The buffer tubes <NUM> are optionally filled with an optic cable grease or gel <NUM>. Gel and grease compounds may include hydrocarbon-based greases incorporating hydrocarbon oils and/or polymer-based greases that use a low viscosity polymer formulated with hydrocarbon oils. These greases and gels provide the suspension and protection needed in the immediate environment surrounding the optical fibers <NUM>, including eliminating air space. The gel and grease also provide a barrier against water penetration, which is detrimental to performance of the optical fibers <NUM>.

The following materials are employed in the Examples, below.

Prepare Inventive Examples ("IE") and Comparative Examples ("CE") according to the following criteria. Form a masterblend IE4-<NUM> and CE3-<NUM> including all indicated sample constituents except PBT, M1 and M2. Produce the masterblend using the LDPE, HDPE, silane copolymer, MAH-g-HDPE, OH-PDMS and antioxidant components to ensure proper oil incorporation. Produce the masterblends in a BRABENDER™ mixing bowl setup with cam mixing blades set to <NUM> rotations per minute and a temperature of <NUM> to <NUM>. Place the masterblends of IE4-<NUM> and CE3-<NUM> in a BRABENDER™ model D6/<NUM> twin screw extruder according to the conditions provided in Table <NUM> using <NUM> screws along with the PBT and M1 and M2.

Place the constituents of IE1-<NUM> and CE2 in a ZSK <NUM> COPERION™ twin screw extruder set to the compounding conditions provided in Table <NUM>.

Form samples by performing coated wire extrusion. Coated wire extrusion models both the dimensions of a buffer tube and tests extrusion performance of the polymeric composition. Perform the coated wire extrusion using a BRABENDER Mini-wire line on <NUM>-gauge copper wire. The BRABENDER Mini-wire line settings are provided in Table <NUM>.

The Inventive and Comparative Examples have a final diameter of approximately <NUM> (<NUM>") and a wall thickness of approximately <NUM> (<NUM> mil) on <NUM> American Wire Gauge solid copper conductor of <NUM> (<NUM>") diameter. Remove the conductor from the wire to leave tubes of the Inventive and Comparative Examples. Perform mechanical testing on the tubes according to the following test methods.

Extrude the Inventive and Comparative Examples into single stands having a diameter of <NUM>. Feed the strands into a BERLYN™ pelletizer. Compression mold the pellets to form plaques for flex modulus testing.

Employ the following test methods to determine the properties of the materials and the Inventive and Comparative Examples, below.

Determine polymeric densities according to ASTM D792 at <NUM>.

Cut the tubes to a length of <NUM>. Clamp the tube into an INSTRON™ <NUM> tensile testing unit with a jaw separation of <NUM>, with a <NUM> lbs. Set crosshead speed to <NUM>/minute and measure the stress at the pulling break point of the tubes. Repeat five times and take the average.

Die cut rectangular samples of <NUM> wide by <NUM> by <NUM> from compression molded plaques. Place samples in a flex fixture of an INSTRON™ <NUM> tester for <NUM>-point deflection using a <NUM> span and crosshead speed of <NUM>/min. Determine the flex modulus at the maximum flexural stress sustained during the test.

Wrap the Inventive and Comparative example samples <NUM> complete wrap around a <NUM> mandrel and hold in position for <NUM> seconds. Observe any kinking that forms.

Place tube in an INSTRON™ <NUM> tester between an upper moveable plate (dimensions <NUM> x <NUM>) attached to a crosshead and a lower stationary plate (dimensions <NUM> x <NUM>). Align the tube to the longer dimension of the plate and move the top plate to just touch the top of the tube. Set crosshead speed to <NUM>/min and record the compressive force at the yield point of the tube.

Apply <NUM> Pa of stress at <NUM> for <NUM> minutes using a RHEOMETRICS™ SR-<NUM> controlled stress rheometer equipped with <NUM> parallel plates. Calculate zero shear viscosity over a range in the data in which the time rate of change of the measured strain is constant. Allow for <NUM>-minute recovery times.

Table <NUM> provides composition and mechanical property data for CE1-CE7.

Table <NUM> provides composition and mechanical property data for IE1-IE9, E10, and IE11-IE15.

As can be seen from Table <NUM>, CE1-CE7 each exhibit kinking or breaking. The kinking and breaking are believed to be a result of dimensional and morphology instability during extrusion. Further, the dimensional and morphology instability generally led to lower break stress values in the Comparative Examples CE2-CE7 (examples comprising polyolefin) as compared to IE1-IE9, E10, IE11-IE15. Accordingly, IE1-IE9, E10, IE11-IE15 demonstrate improved kink resistance compared to the pure PBT (CE1) and sample without the silanol-functionalized polyolefin component (CE2).

IE1 replaces about an equivalent amount of LDPE used in CE2 with Silane Copolymer while keeping the same amount of MAH-g-HDPE. IE1 shows improved kink resistance and higher tube break stress compared to CE2. The HDPE component was removed in IE2 and the amount of MAH-g-HDPE roughly doubled versus IE1. IE2 shows similar improved tube break stress and higher flex modulus compared to IE1 and no kinking. It is believed that the increased concentration of MAH-g-HDPE increased morphology stability resulting tin the improved flex modulus. IE3 is similar to IE2 except the level of Silane Copolymer was increased by about <NUM> wt%. The results of IE3 did not change significantly compared to IE2. IE4 is similar in composition to IE1 except IE4 has <NUM> wt% of OH-PDMS instead of <NUM> wt%. IE4 had only a slightly higher tube break stress and flex modulus versus IE1, IE2, and IE3. This result suggests that <NUM> wt% OH-PDMS is sufficient to enable crosslinking of the Silane Copolymer IE samples. CE3 is similar in composition to IE4 except it does not include MAH-g-HDPE. CE3 failed the kink test and also had lower break stress and flex modulus values compared to IE1-IE4. This result is believed to occur due to morphology instability from the lack of the compatibilizing effect of MAH-g-HDPE between the PBT and the HDPE. IE9 has no HDPE and a greater wt% of Silane Copolymer as compared to IE6, IE7, and IE8. The level of OH-PDMS is also increased as compared to IE8 to accommodate the higher level of the Silane Copolymer. Results for IE9 indicate acceptable mechanical properties can be achieved without the HDPE component compared to IE6, IE7, and IE8. E10 (not within scope of currently claimed invention) is similar in composition to IE9 except that no MAH-g-HDPE and HDPE are included. The amount of Silane Copolymer is increased to <NUM> wt% in E10. E10 shows a significant drop in tube break stress and flex modulus compared to IE5-IE9 however the zero-shear viscosity increased and exhibited no kinking indicating that the Silane Copolymer at sufficiently high levels is able to maintain morphology stability and provide sufficient viscosity to maintain dimensional stability during extrusion.

Claim 1:
A method, comprising the steps:
blending a polymeric composition, comprising:
(a) <NUM> wt% to <NUM> wt% of a silanol-functionalized polyolefin based on a total weight of the polymeric composition;
(b) <NUM> wt% to <NUM> wt% of a polybutylene terephthalate based on a total weight of the polymeric composition having a melt flow index from <NUM>/<NUM>. to <NUM>/<NUM>. at <NUM> and <NUM>, as measured according to ASTM method D1238;
(c) a condensation catalyst; and
(d) <NUM> wt% to <NUM> wt% of hydroxy terminated poly(dimethylsiloxane) based on a total weight of the polymeric composition; and
extruding the polymeric composition;
wherein the blending step further comprises blending <NUM> wt% to <NUM> wt% maleated ethylene-based polymer into the polymeric composition based on a total weight of the polymeric composition.