阅读说明：本技术 具有低弹性模量的光纤电缆护套 (Optical fiber cable jacket with low modulus of elasticity ) 是由 安·杰曼·布兰吉耶 程晓乐 李延飞 于 2020-02-05 设计创作，主要内容包括：本公开的实施方式涉及一种聚合物组合物。所述聚合物组合物包括0重量％至80重量％的聚烯烃组分和20重量％至100重量％的热塑性弹性体组分。所述聚合物组合物具有根据ASTM D4065使用动态力学分析在-40℃下测量的小于1500MPa的弹性模量；此外,当根据ASTM E831测量时,所述聚合物组合物具有在-40℃至25℃的温度范围内平均超过120×10～(-6)/K的热膨胀系数,并且所述聚合物组合物具有如使用动态力学分析在-40℃下测量的不超过4.0MPa的热收缩应力。另外,本文公开了一种具有由所述聚合物组合物制成的光纤电缆护套的光纤电缆的实施方式。(Embodiments of the present disclosure relate to a polymer composition. The polymer composition includes from 0 wt% to 80 wt% of a polyolefin component and from 20 wt% to 100 wt% of a thermoplastic elastomer component. The polymer composition has an elastic modulus of less than 1500MPa measured at-40 ℃ using dynamic mechanical analysis according to ASTM D4065; further, the polymer composition has an average of more than 1 over a temperature range of-40 ℃ to 25 ℃ when measured according to ASTM E83120×10 ‑6 A coefficient of thermal expansion,/K, and the polymer composition has a thermal shrinkage stress of no more than 4.0MPa as measured at-40 ℃ using dynamic mechanical analysis. Additionally, disclosed herein are embodiments of an optical fiber cable having an optical fiber cable jacket made from the polymer composition.)

1. A polymer composition comprising:

0 to 80 weight percent of a polyolefin component; and

20 to 100 wt% of a thermoplastic elastomer component;

wherein the polymer composition has an elastic modulus of at most 1500MPa measured at-40 ℃ using dynamic mechanical analysis according to ASTM D4065;

wherein the polymer composition has a temperature range of-40 ℃ to 25 ℃ as measured according to ASTM E831, average of at least 120 x 10^-6A coefficient of thermal expansion,/K; and is

Wherein the polymer composition has a thermal shrinkage stress of at most 4.0MPa as measured using dynamic mechanical analysis at-40 ℃.

2. The polymer composition of claim 1, wherein the polyolefin component comprises at least one of: medium density polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene or polypropylene.

3. The polymer composition of claim 1, wherein the thermoplastic elastomer component comprises at least one of: olefin block copolymers, olefin random copolymers, ethylene-propylene rubbers, ethylene-propylene-diene rubbers, ethylene-octene, ethylene-hexene, ethylene-butene, ethylene-vinyl acetate or styrene-ethylene-butadiene-styrene.

4. The polymer composition of claim 1, wherein the coefficient of thermal expansion is at least 160 x 10^-6/K。

5. The polymer composition of claim 1, wherein the coefficient of thermal expansion is at most 300 x 10^-6/K。

6. The polymer composition according to any one of claims 1 to 5, wherein the thermal shrinkage stress is at most 2.0 MPa.

7. The polymer composition of claim 1, comprising up to 40 wt% of a filler component.

8. The polymer composition of claim 7, wherein the filler component comprises at least 2.5 weight percent carbon black for UV protection.

9. The polymer composition of claim 7, wherein the filler component comprises a flame retardant additive.

10. The polymer composition of claim 9, wherein the flame retardant additive comprises alumina trihydrate, magnesium hydroxide, boehmite, CaCO₃Or an intumescent material.

11. An optical fiber cable comprising:

at least one optical fiber;

a polymer jacket surrounding the at least one optical fiber;

wherein the polymer jacket is formed at least in part from a polymer composition comprising:

0 to 80 weight percent of a polyolefin component;

20 to 100 wt% of a thermoplastic elastomer component;

wherein the polymer composition has an elastic modulus of at most 1500MPa measured at-40 ℃ using dynamic mechanical analysis according to ASTM D4065;

wherein the polymer composition has a temperature range of-40 ℃ to 25 ℃ as measured according to ASTM E831, average of at least 120 x 10^-6A coefficient of thermal expansion,/K; and is

Wherein the polymer composition has a thermal shrinkage stress of at most 4.0MPa as measured using dynamic mechanical analysis at-40 ℃.

12. The fiber optic cable of claim 11, wherein the polyolefin component comprises at least one of: medium density polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene or polypropylene.

13. The fiber optic cable of claim 11, wherein the thermoplastic elastomer component comprises at least one of: olefin block copolymers, olefin random copolymers, ethylene-propylene rubbers, ethylene-propylene-diene rubbers, ethylene-octene, ethylene-hexene, ethylene-butene, ethylene-vinyl acetate, or styrene-ethylene-butadiene-styrene.

14. The fiber optic cable of claim 11, wherein the coefficient of thermal expansion is at least 160 x 10^-6/K。

15. The fiber optic cable of claim 14, wherein the coefficient of thermal expansion is at most 300 x 10^-6/K。

16. The fiber optic cable of claim 14, wherein the polymer composition has a thermal shrinkage stress of at most 2.0 MPa.

17. The fiber optic cable of claim 11, wherein the polymer composition comprises up to 40 weight percent of a filler component.

18. The fiber optic cable of claim 17, wherein the filler component includes a flame retardant additive.

19. The fiber optic cable of claim 18, wherein the flame retardant additive comprises alumina trihydrate, magnesium hydroxide, boehmite, CaCO₃Or an intumescent material.

20. The fiber optic cable of claim 17, wherein the filler component includes at least 2.5 weight percent carbon black for UV protection.

21. The fiber optic cable of claim 11, wherein the polymer jacket is coextruded with an outer layer of at least one of linear low density polyethylene, medium density polyethylene, or high density polyethylene, and wherein the outer layer is thinner than the polymer jacket.

22. The fiber optic cable of claim 11, further comprising a buffer tube and a plurality of aramid yarns, wherein the at least one optical fiber is disposed in the buffer tube, and wherein the plurality of aramid yarns are disposed around the buffer tube.

23. The fiber optic cable of claim 22, wherein the fiber optic cable does not include any glass yarns that act as tensile elements.

24. A fiber optic drop cable comprising:

at least one optical fiber;

a buffer tube disposed around the at least one optical fiber;

a plurality of tensile yarns disposed about the buffer tube;

a polymer jacket disposed about the plurality of tensile yarns;

wherein the polymer jacket is formed at least in part from a polymer composition consisting essentially of:

0 to 80 weight percent of a polyolefin component;

20 to 100 wt% of a thermoplastic elastomer component; and

0 to 40 weight percent of a filler component;

wherein the polymer composition has an elastic modulus of 200MPa to 1500MPa measured at-40 ℃ using dynamic mechanical analysis according to ASTM D4065; and is

Wherein the polymer composition has an average of 120 x 10 over a temperature range of-40 ℃ to 25 ℃ when measured according to ASTM E831^-6from/K to 300X 10^-6Coefficient of thermal expansion,/K.

25. The fiber optic drop cable of claim 24, wherein the polymer composition has a thermal shrinkage stress of at most 4.0MPa as measured at-40 ℃ using dynamic mechanical analysis.

Technical Field

The present invention relates to a polymer composition having a low modulus of elasticity, and more particularly to a polymer composition particularly suitable for use as a jacket for an optical fiber cable.

Background

Some polyolefins have advantageous properties for use as cable jacket materials for a variety of cable types. In particular, certain polyolefins have good flexibility and are capable of maintaining certain relevant mechanical properties over an operating temperature range. A polyolefin may be extruded around the cable to help protect the internal components of the cable from the environment in which the cable is deployed.

Disclosure of Invention

In one aspect, embodiments of the present disclosure relate to a polymer composition. The polymer composition includes from 0 wt% to 80 wt% of a polyolefin component and from 20 wt% to 100 wt% of a thermoplastic elastomer component. The polymer composition has an elastic modulus of at most 1500MPa as measured according to ASTM D4065 using dynamic mechanical analysis at-40 ℃. Further the polymer composition has an average of at least 120 x 10 over a temperature range of-40 ℃ to 25 ℃ when measured according to ASTM E831^-6A coefficient of thermal expansion,/K, and the polymer composition has a thermal shrinkage stress of at most 4.0MPa as measured at-40 ℃ using dynamic mechanical analysis.

In another aspect, embodiments of the present disclosure relate to a fiber optic cable. The fiber optic cable includes at least one optical fiber and a polymer jacket surrounding the at least one optical fiber. The polymer jacket is formed at least in part from a polymer composition comprising from 0 wt% to 80 wt% of a polyolefin component and from 20 wt% to 100 wt% of a thermoplastic elastomer component. The polymer composition has an elastic modulus of at most 1500MPa as measured according to ASTM D4065 using dynamic mechanical analysis at-40 ℃. Further the polymer composition has an average of at least 120 x 10 over a temperature range of-40 ℃ to 25 ℃ when measured according to ASTM E831^-6A coefficient of thermal expansion,/K, and the polymer composition has a thermal shrinkage stress of at most 4.0MPa as measured at-40 ℃ using dynamic mechanical analysis.

In yet another aspect, embodiments of the present disclosure relate to a fiber optic drop cable. The fiber optic drop cable includes at least one optical fiber and a buffer tube disposed about the at least one optical fiber. In addition, the fiber optic drop cable includes a plurality of tensile yarns disposed about the buffer tube and a polymer jacket disposed about the plurality of tensile yarns. The polymeric jacket is at least partially formed from a polymer composition consisting essentially of 0 to 80 weight percent of a polyolefin component, 20 to 100 weight percent of a thermoplastic elastomer component, and 0 to 40 weight percent of a filler component. The polymer composition has an elastic modulus of 200 to 1500MPa as measured according to ASTM D4065 using dynamic mechanical analysis at-40 ℃ and the polymer composition has an average of 120 x 10 over a temperature range of-40 ℃ to 25 ℃ when measured according to ASTM E831^-6from/K to 300X 10^-6Coefficient of thermal expansion,/K.

Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are merely exemplary and are intended to provide an overview or framework for understanding the nature and character of the claims.

The accompanying drawings are included to provide a further understanding and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments and, together with the description, serve to explain the principles and operations of the various embodiments.

Drawings

The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a graphical representation of the elastic modulus over a temperature range for a polymer composition made according to an exemplary embodiment and a comparative example;

FIG. 2 is a graphical representation of the coefficient of thermal expansion over a range of temperatures for a polymer composition made according to an exemplary embodiment and a comparative example;

FIG. 3 depicts dimensional changes as a function of temperature used to calculate the coefficient of thermal expansion of a polymer composition made according to an exemplary embodiment;

FIG. 4 is an illustration of a fiber optic cable wherein components of the cable include a polymer composition made according to an exemplary embodiment; and is

Fig. 5 is an illustration of a round drop cable having a cable jacket including a polymer composition according to an exemplary embodiment.

While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the invention is intended to cover all alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.

Detailed Description

Referring generally to the drawings, various embodiments of polymer compositions having low elastic moduli, particularly at temperatures as low as-40 ℃, are provided. The low elastic modulus of the polymer composition results in a reduction of the shrinkage force at-40 ℃. In embodiments, the polymer composition is used as a component of an optical fiber cable, particularly as a cable jacket. As a cable jacket material, the polymer composition improves the temperature cycling performance of the fiber optic cable. Advantageously, by using a cable jacket made of the disclosed polymer composition, hard or stiff glass yarns can be replaced with, for example, soft aramid yarns as tensile elements, which allows for improved bending properties. Furthermore, such fiber optic cables can be made more cost effectively because smaller strength members (e.g., glass reinforced plastic strength bars) can be used, and because more fibers can be included in the fiber optic cable without sacrificing low temperature performance. Alternatively, the cable jacket of the disclosed polymer composition allows for the use of smaller tubes, and therefore, smaller cable outer diameters due to lower shrinkage of the overall cable at low temperatures. In embodiments, the polymer composition can be used to reduce thermal strain on a fiber optic cable component (e.g., outer cable jacket, inner cable jacket, adhesive layer, etc.) of the cable. Although embodiments of the polymer composition are discussed in the context of fiber optic cables, such discussion is not intended to limit the possible contexts and applications in which the polymer composition may be utilized.

As mentioned above, the disclosed polymer compositions are particularly useful for reducing heat shrinkage strain in loose-tube fiber optic cables. One way to express the thermal strain of a loose tube cable is provided in the following equation:

where E is the modulus of elasticity of the material, A is the cross-sectional area of the material, and α is the Coefficient of Thermal Expansion (CTE) of the material. In the presently disclosed polymer compositions, the components of the polymer composition are selected so as to reduce thermal shrinkage of the cable jacket or inner jacket material, which occurs at low temperatures and results in increased optical attenuation. By reducing the thermal strain, the thermal contraction stress is reduced. In previous attempts to reduce thermal strain, emphasis was placed on reducing the CTE of the cable jacket material. However, while such compositions are successful in reducing thermal strain, for certain applications the cost of low CTE materials is prohibitive, and low CTE jacket materials have higher surface friction than other conventional materials, which is detrimental to certain cable installation methods, such as "jetting" or "blow molding" the cable through a duct. In addition, low CTE materials tend to be incompatible with certain cable access technologies because low CTE materials are too compatible with the access features (e.g., polypropylene strips extending along the longitudinal axis of the cable jacket), resulting in enhanced adhesion between the low CTE material and the access features.

Thus, embodiments of the presently disclosed polymer compositions seek to reduce the elastic modulus over the cable operating temperature range of-40 ℃ to 80 ℃ compared to low CTE compositions. In this regard, the presently disclosed polymer compositions include a mixture of a polyolefin component and a thermoplastic elastomer component. Embodiments of the disclosed polymer compositions have an elastic modulus of less than 1500MPa over the entire temperature range of-40 ℃ to 80 ℃. Further, in an embodiment, the polymer composition exhibits a thermal shrinkage stress at-40 ℃ of not more than 4.0 MPa. In embodiments, the polymer composition is used as a cable jacket around one or more buffer tubes containing optical fibers or optical fiber ribbons, and in other embodiments, the polymer composition is used as an inner layer jacket of a two-layer jacket structure having an outer layer of standard cable jacket material.

In an embodiment, the polymer composition includes a polyolefin component, a thermoplastic elastomer component, and an optional filler component. In exemplary embodiments, the polyolefin component may include at least one of Medium Density Polyethylene (MDPE), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), or polypropylene (PP) copolymer, among other polyolefins. In embodiments, the polyolefin component is 0 to 80 weight percent of the polymer composition. In other embodiments, the polyolefin component is 20 to 70 weight percent of the polymer composition, and in other embodiments, the polyolefin component is 40 to 60 weight percent of the polymer composition.

In exemplary embodiments, the thermoplastic elastomer component of the polymer composition may include at least one of: olefin block copolymers, olefin random copolymers, ethylene-propylene rubbers (EPR), ethylene-propylene-diene rubbers (EPDM), ethylene-octene (EO), ethylene-hexene (EH), ethylene-butene (EB), ethylene-vinyl acetate (EVA), ethylene-butyl acetate (EBA), and styrene-ethylene-butadiene-styrene (SEBS), and the like. In an embodiment, the polymer composition comprises 20 to 100 weight percent of the thermoplastic elastomer. In further embodiments, the polymer composition comprises 30 to 80 weight percent of the thermoplastic elastomer, and in other embodiments, the polymer composition comprises 40 to 60 weight percent of the thermoplastic elastomer.

In embodiments that include a filler component, the filler component may be added to reduce cost or provide additional functionality. For example, the filler component may be configured to provide flame retardancy. Exemplary flame retardant fillers include Alumina Trihydrate (ATH), magnesium hydroxide (MDH), boehmite (aluminum hydroxide), calcium carbonate (CaCO)₃) And intumescent additives (e.g., melamine, ammonium polyphosphate, pentaerythritol, polyphosphonates, and other phosphorus-containing compounds), and the like. The filler component may comprise one or more flame retardant additives and/or one or more other fillers, such as talc, carbon black, TiO₂And the like. In a particular embodiment, the filler comprises at least 2.5 wt% carbon black for UV protection in outdoor applications. In an embodiment, the polymer composition includes up to 40 weight percent of a filler component.

In an embodiment, the polymer composition consists essentially of only the polyolefin component, the thermoplastic elastomer component, and the optional filler component. That is, the polymer composition may not contain additional components. However, in certain embodiments, the polymer compositions may include other minor processing and/or performance additives that do not substantially affect the basic and novel characteristics of the disclosed polymer compositions. For example, a dispersant may be added to aid in the dispersion of the filler component. Still further, the polymer composition may include up to 1 weight percent of a low friction additive, such as a fatty acid or fatty acid amide. For example, the fatty acid may have a C between₆To C₂₅Carbon of (2) CA backbone, and is saturated or unsaturated. Specific examples include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, and the like. Similarly, the fatty acid amide may have, for example, between C₆And C₂₅And is saturated or unsaturated.

In an embodiment, the polymer composition is prepared by extrusion. In a specific embodiment, the polymer composition is prepared by twin screw extrusion. In the particular context of a fiber optic cable, the polymer composition can be extruded into a jacket of the fiber optic cable and/or another component of the fiber optic cable.

In an embodiment, the elastic modulus (alternatively, the storage modulus) measured by Dynamic Mechanical Analysis (DMA) at-40 ℃ according to ASTM D4065 is at most 1500 MPa. In a further embodiment, the modulus of elasticity measured by DMA at-40 ℃ is at most 1000MPa, and in yet another embodiment, the modulus of elasticity measured by DMA at-40 ℃ is at most 500 MPa. In an embodiment, the modulus of elasticity as measured by DMA at-40 ℃ is in the range of 200MPa to 1500 MPa. Further, in embodiments, the CTE measured from-40 ℃ to 25 ℃ is at least 120 x 10^-6and/K. In other embodiments, the CTE is at least 140 × 10^-6K, and in other embodiments, CTE is at least 160 x 10^-6and/K. In an embodiment, the CTE is at most 300X 10^-6and/K. Still further, in an embodiment, the thermal shrinkage stress measured at-40 ℃ using a dynamic mechanical analyzer is at most 4.0 MPa. In other embodiments, the thermal shrinkage stress at-40 ℃ is at most 3.0MPa, and in other embodiments, the thermal shrinkage stress at-40 ℃ is at most 2.0 MPa.

Examples

Several exemplary polymer compositions were prepared according to the compositions provided in table 1 below. C1 and C2 are comparative examples, E1-E5 are examples according to the disclosure. In Table 1, LLDPE corresponds toLE8707 (available from Borealis AG, Vienna, Aust)ria), OBC1 corresponds to the olefin block copolymer INFUSE^TM9100 LDPE corresponds to AGILITY^TM1021 OBC2 corresponds to INFUSE^TM9500 OBC3 corresponds to INFUSE^TM 9807(INFUSE^TMAnd AGILITY^TMPolymers available from The Dow Chemical Company, Midland, Michigan, USA). OBC1 and OBC2 have the same density of 0.877g/cm³However, the OBC2 has a higher melt index (5g/10min vs. 1g/10min (2.16 kg at 190 ℃). The OBC3 has a density of 0.866g/cm lower than OBC1 and OBC2³But the OBC3 has the highest melt index (15g/10 min).

TABLE 1 formulation and Properties Polymer compositions

	Composition comprising a metal oxide and a metal oxide	Weight ratio of	Thermal shrinkage stress (MPa)
				C1	LLDPE	100/0	4.85
C2	LLDPE/SEBS/clay	50/40/10	1.78
				E1	LLDPE/OBC1	70/30	2.95
E2	LLDPE/OBC1	50/50	1.44
				E3	LLDPE/OBC1/CaCO3 masterbatch	40/40/20	1.56
E4	LDPE/OBC2	30/70	0.97
				E5	LDPE/OBC3	50/50	1.79

As shown in table 1, the thermal shrinkage stress of each composition C1 and C2 and E1 to E5 was measured. In particular, the thermal shrinkage stress was measured on a pressed sample sandwiched between two jaws using a Dynamic Mechanical Analyzer (DMA) by reducing the temperature from 35 ℃ to-40 ℃ and measuring the shrinkage stress at-40 ℃. As can be seen from table 1, C1 containing LLDPE alone exhibited a shrinkage stress of 4.85MPa, which is significantly higher than C2 and E1 to E5. C2 is a low CTE formulation with a shrinkage stress below 2MPa, but as discussed below, the modulus of elasticity of C2 is well above 1500MPa at-40 ℃. The CTE of C2 is also lower than E1-E5 in the temperature range of-40 ℃ to 40 ℃. Comparing E1 and E2, it can be seen that as the amount of thermoplastic elastomer (OBC1) increases, the shrinkage stress decreases; however, both E1 and E2 are below a shrinkage stress of 4.0 MPa. Further, as shown in E3, the polyolefin and thermoplastic elastomer were maintained at a 1:1 ratio, but 20 wt% filler was added to the masterbatch. It can be seen that the shrinkage stress increases only slightly from E2. E4 and E5 show the shrinkage stress of compositions containing another polyolefin LDPE. As with E1 and E2, the shrinkage stress decreases as the amount of thermoplastic elastomer increases.

The elastic moduli of C1, C2, E2 and E3 were obtained using DMA and are shown in fig. 1 for a temperature range of-40 ℃ to 80 ℃. As can be seen in fig. 1, the modulus of elasticity of E2 and E3 is much flatter than C1 and C2 over the entire temperature range. In particular, the elastic modulus of C1 increases rapidly with decreasing temperature. C2 has a somewhat flat modulus of elasticity, which increases dramatically until below about-20 ℃. In fact, C2 has an elastic modulus at-40 ℃ of about 2000 MPa. In contrast, E2 (without filler) and E3 (with filler) have elastic moduli below 1000MPa throughout the depicted temperature ranges.

Figure 2 depicts CTE measured for E3, C1, and C2 over the temperature range of-40 ℃ to 40 ℃. It is clear that C2 has a CTE much lower than E3 and C1 over the entire temperature range, which is the way to achieve the low thermal contraction stress shown in table 1. However, E3 is able to achieve lower thermal contraction stresses than C2, despite having a CTE about the same as C1. Thus, fig. 1 and 2 demonstrate the opposite properties of CTE and elastic modulus to achieve low (e.g., less than 4.0MPa) thermal contraction stress, as demonstrated by samples E3 and C2. Figure 3 depicts CTE measurements performed between-40 ℃ and 70 ℃ for E1-E3. The average CTE of these three samples from-40 ℃ to 23 ℃ was about 200X 10 as calculated based on the measurements shown on the graph of FIG. 3^-6from/K to 250X 10^-6In the range of/K. The thermal expansion behaviour of the polymer composition was measured by thermomechanical analysis (TMA) according to ASTM E831.

The polymer compositions disclosed herein can be applied in a variety of contexts. In the particular embodiment shown in fig. 4, the polymer composition is used as a sheath for a cable or cable component. The cable shown in fig. 4 is a fiber optic cable 20. The cable 20 includes a cable body, shown as a cable jacket 22, having an inner surface 24 defining a channel, shown as a central bore 26. A plurality of communication elements, shown as optical fibers 28, are located within the holes 26. The cable 20 includes a plurality of core elements positioned within the central bore 26. The first type of core elements are optical transmission core elements and these core elements include optical fiber bundles 28 located within tubes, shown as buffer tubes 30. Buffer tubes 30 are arranged around a central strut member, shown as central strength member 34. The central reinforcing member 34 includes an outer coating 36. A barrier material, such as a water-resistant barrier 38, is positioned around the wrapped buffer tube 30. An easy access feature, shown as ripcord (rip cord)39, may be located inside cable jacket 22 to facilitate access to buffer tubes 30.

In one embodiment, the polymer composition is incorporated into the fiber optic cable jacket 22 of the fiber optic cable 20. In another embodiment, the polymer composition is used to coat the central reinforcing member 34 upward to form the outer coating layer 36. For example, the selection of the number of buffer tubes 30 may define an internal open geometry that is filled/supported by the central strength member 34 and the outer coating 36. To reduce the cost of the fiber optic cable 20, the central strength member 34 may be made as thin as possible while still providing the necessary support for the fiber optic cable 20. By coating the polymer composition upwardly on the central reinforcing member 34, the remainder of the interior open geometry may be filled with an outer coating 36. In this manner, the cost of providing the central reinforcing member 34 and the outer coating layer 36 is reduced because the presently disclosed polymer compositions used to form the outer coating layer 36 are generally less expensive in terms of material cost than the central reinforcing member 34.

Fig. 5 depicts a cross-section of another embodiment of a fiber optic cable 20', which is a round drop cable (i.e., an aerial, buried or raceway cable leading to a premise). The fiber optic cable 20' includes optical fibers 28 housed within a buffer tube 30. In the depicted embodiment, only a single optical fiber 28 is contained within the buffer tube 30, but in other embodiments, more than one optical fiber 28 may be contained within the buffer tube 30. Buffer tube 30 is surrounded by a plurality of tensile yarns 40, such as aramid, carbon fiber, Ultra High Molecular Weight Polyethylene (UHMWPE), Ethylene Chlorotrifluoroethylene (ECTFE), Polybenzimidazole (PBI), Perfluoroalkoxy (PFA), Polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), Liquid Crystal Polymer (LCP), or Polyphenylene Benzobisoxazole (PBO). Advantageously, these relatively soft tensile yarns 40 may replace the harder glass yarns conventionally used to enhance bending performance. Disposed around tensile yarn 40 is cable jacket 22. The cable jacket 22 is made from the polymer composition disclosed herein. As shown in fig. 5, the access feature 39 is embedded in the cable jacket 22. Fig. 5 also depicts an optional outer coating 42 extruded around the cable jacket 22. In such embodiments, the optional outer coating 42 of the fiber optic cable 20' is a layer of LLDPE, MDPE, HDPE, or the like, which can be used to reduce the coefficient of friction of the resulting cable when the cable is blown inside a tube. In such embodiments, the outer coating 42 may be thinner than the cable jacket 22.

Moreover, the use of the polymer compositions disclosed herein provides several advantages. In particular, the polymer composition can be used to produce fiber optic cables having enhanced thermal properties and reduced manufacturing costs. Finally, the incorporation of the disclosed polymer compositions into various components of an optical fiber cable can help achieve the goals of reducing buffer tube size, shortening lay length, and driving cable design to concurrent performance limits under load and low temperatures.

In addition, the polymer compositions made according to embodiments disclosed herein provide several additional advantages when used as components of fiber optic cables. For example, the polymer composition can help extend the operating temperature range of the fiber optic cable to-40 ℃ or lower. Also, a lower thermal shrinkage stress of less than 4.0MPa may reduce the attenuation of the optical fiber in contact with the polymer composition, which is caused by the shrinkage of the polymer composition in a cold environment. In addition, the polymer composition may allow for the use of smaller buffer tubes, resulting in lower material costs and lower overall product costs. As discussed above, the polymer composition may help reduce the diameter (and thus the cost) of the central reinforcing member. Furthermore, due to the potential for producing smaller cable sizes by using the disclosed polymer compositions, the resulting cables are expected to have better blowing properties during installation.

Unless explicitly stated otherwise, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a particular order. Thus, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred. Further, as used herein, the articles "a" and "an" are intended to include one or more than one component or element, and are not intended to be construed as meaning only one.

It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed embodiments without departing from the spirit or scope of the embodiments. Since modifications, combinations, sub-combinations and variations of the embodiments incorporating the spirit and substance of the disclosed embodiments may occur to persons skilled in the art, the disclosed embodiments are to be considered as including all changes which come within the scope of the appended claims and their equivalents.