POLYPROPYLENE CABLE PROTECTIVE LAYER AND PREPARATION METHOD THEREOF

Abstract

The present invention provides a polypropylene cable protective layer and a preparation method thereof. The polypropylene cable protective layer sequentially includes a dielectric layer, a buffer layer and an insulating layer from the inside to the outside, and the thickness of the dielectric layer accounts for 5%?12% of the thickness of the polypropylene cable protective layer; the thickness of the buffer layer accounts for 17%?25% of the thickness of the polypropylene cable protective layer; the dielectric layer, the buffer layer and the insulating layer are respectively obtained by the wrapping of a polypropylene film A, a polypropylene film B and a polypropylene film C. The polypropylene cable protective layer of the present invention forms a dielectric gradient, and realizes the improvement of the insulation strength and voltage level of the power cable, and the increase of the transmission capability.

Claims

1. A polypropylene cable protection layer, wherein the polypropylene cable protection layer sequentially comprises a dielectric layer, a buffer layer and an insulating layer from the inside to the outside, and the thickness of the dielectric layer accounts for 5%?12% of the thickness of the polypropylene cable protective layer; the thickness of the buffer layer accounts for 17%?25% of the thickness of the polypropylene cable protective layer; the dielectric layer is obtained by the wrapping of a polypropylene film A, and the buffer layer is obtained by the wrapping of a polypropylene film B, and the insulating layer is obtained by the wrapping of a polypropylene film C; the polypropylene film A comprises the following components in parts by weight: 100 parts of polypropylene, 8?10 parts of graphene oxide and 0.5?5 parts of maleic anhydride grafted polypropylene, and the thickness of the polypropylene film A is 0.05?0.2 mm; the polypropylene film B comprises the following components in parts by weight: 100 parts of polypropylene, 4?6 parts of graphene oxide and 0.5?5 parts of maleic anhydride grafted polypropylene, and the thickness of the polypropylene film B is 0.05?0.2 mm; the polypropylene film C comprises the following components in parts by weight: 100 parts of polypropylene and 0.5?5 parts of maleic anhydride grafted polypropylene, and the thickness of the polypropylene film C is 0.05?0.2 mm.

2. The polypropylene cable protective layer according to claim 1, wherein the thickness of the polypropylene film A is 0.08?0.15 mm; the thickness of the polypropylene film B is 0.08?0.15 mm; the thickness of the polypropylene film C is 0.08?0.15 mm.

3. The polypropylene cable protective layer according to claim 1, wherein the thickness of the dielectric layer accounts for 8%?10% of the thickness of the polypropylene cable protective layer; the thickness of the buffer layer accounts for 17%?20% of the thickness of the polypropylene cable protective layer.

4. The polypropylene cable protection layer according to claim 1, wherein the polypropylene cable protection layer is formed by hot pressing at 160? C.?180? C.

5. The polypropylene cable protective layer according to claim 1, wherein the polypropylene film A comprises the following components in parts by weight: 100 parts of polypropylene, 9?10 parts of graphene oxide and 1?5 parts of maleic anhydride grafted polypropylene; the polypropylene film B comprises the following components in parts by weight: 100 parts of polypropylene, 5?6 parts of graphene oxide and 1?5 parts of maleic anhydride grafted polypropylene; the polypropylene film C comprises the following components in parts by weight: 100 parts of polypropylene and 1?5 parts of maleic anhydride grafted polypropylene.

6. The polypropylene cable protective layer according to claim 5, wherein the relative permittivity of the polypropylene film A is 30?35, the electrical conductivity is (0.8?1.2)?10.sup.?8 S/m, and the thermal conductivity is 0.7?0.9 W/m.Math.K; the relative permittivity of the polypropylene film B is 10?12, the electrical conductivity is (0.8?1.2) 10.sup.?12 S/m, and the thermal conductivity is 0.4?0.6 W/m.Math.K; the relative permittivity of the polypropylene film C is 2.2?2.5, the electrical conductivity is (0.8?1.2) 10.sup.?1+S/m, and the thermal conductivity is 0.2?0.3 W/m.Math.K.

7. A cable, wherein the cable sequentially comprises a conductor, the polypropylene cable protective layer according to claim 1 and an outer insulation screen layer from the inside to the outside.

8. A preparation method of the polypropylene cable protective layer according to claim 1, wherein the method comprises the following steps: (1) wrapping the polypropylene film A as a dielectric layer; (2) wrapping the polypropylene film B along the dielectric layer to obtain a buffer layer; (3) wrapping the polypropylene film C along the buffer layer to obtain an insulating layer; (4) hot pressing forming at 160? C.?180? C., wherein the hot pressing direction of the hot pressing forming includes several hot pressing directions that are centrosymmetric and perpendicular to the circumference of the polypropylene cable protective layer, and the pressure deviation of several hot pressing directions does not exceed 2%.

9. The preparation method of the polypropylene cable protective layer according to claim 8, wherein in the step (4), a step-by-step pressurization method is adopted in the hot pressing forming.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 is a front cross-sectional view of a cable according to an embodiment of the present invention.

[0042] FIG. 2 is a side cross-sectional view of a cable according to an embodiment of the present invention.

[0043] FIG. 3 is a graph showing the test result of the maximum electric field of cable according to an embodiment of the present invention.

[0044] 1. Center conductor; 2. Dielectric layer; 3. Buffer layer; 4. Insulating layer; 5. Outer insulation screen layer.

DETAILED DESCRIPTION OF EMBODIMENTS

[0045] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments.

Example 1

[0046] As a polypropylene cable protective layer of an example of the present invention, the polypropylene cable protective layer was sequentially composed of a dielectric layer, a buffer layer and an insulating layer from the inside to the outside, and the thickness of the dielectric layer accounted for 10% of the thickness of the polypropylene cable protective layer; the thickness of the buffer layer accounted for 20% of the thickness of the polypropylene cable protective layer; the dielectric layer was obtained by the wrapping of a polypropylene film A, and the buffer layer was obtained by the wrapping of a polypropylene film B, and the insulating layer was obtained by the wrapping of a polypropylene film C; [0047] the polypropylene film A comprised the following components in parts by weight: 100 parts of polypropylene, 10 parts of graphene oxide and 1 part of maleic anhydride grafted polypropylene, and the thickness of the polypropylene film A was 0.1 mm; [0048] the polypropylene film B comprised the following components in parts by weight: 100 parts of polypropylene, 5 parts of graphene oxide and 1 part of maleic anhydride grafted polypropylene, and the thickness of the polypropylene film B was 0.1 mm; [0049] the polypropylene film C comprised the following components in parts by weight: 100 parts of polypropylene and 1 part of maleic anhydride grafted polypropylene, and the thickness of the polypropylene film C was 0.1 mm.

[0050] The preparation method of the polypropylene cable protective layer of the present embodiment comprised the following steps: [0051] (1) the polypropylene film A was wrapped on the metal conductor cable to obtain a dielectric layer; [0052] (2) the polypropylene film B was wrapped along the dielectric layer to obtain a buffer layer; [0053] (3) the polypropylene film C was wrapped along the buffer layer to obtain an insulating layer; [0054] (4) hot pressing forming was performed at 170? C., the hot pressing direction of hot pressing forming included several hot pressing directions that were centrosymmetric and perpendicular to the circumference of the polypropylene cable protective layer, and the pressure of several hot pressing directions was equal; a step-by-step pressurization method was adopted in the hot pressing forming; the step-by-step pressurization method in the hot pressing forming comprised the following steps: the temperature of the polypropylene cable protective layer was maintained at 160?180? C.; [0055] (a) it was applied pressure at 5 MPa for 2 min; [0056] (b) it was removed pressure and stood for 20 s; [0057] (c) it was applied pressure at 10 MPa for 2 min; [0058] (d) it was removed pressure and stood for 20 s; [0059] (e) it was applied pressure at 15 MPa for 20 min; [0060] (f) after removing the pressure, it was cooled to a temperature of 120? C. and stabilized for 60 minutes; [0061] (g) it was slowly cooled to room temperature at a rate of 10? C./min to obtain the polypropylene cable protective layer.

[0062] The preparation method of the polypropylene film A comprised the following steps: [0063] (1) polypropylene pellets (PP) with a melt index of 2.2 g/10 min at 200? C. (the test conditions refer to GB/T 3682-2018), graphene oxide (GO), and maleic anhydride grafted polypropylene (PP-g-MAH) were sequentially put into a roller ball mill for ball milling and mixing according to the weight ratio to obtain a polypropylene film mixture; [0064] (2) the polypropylene film mixture was made into a film by a two-roll calender, and the thickness of the prepared film was in the numerical range of 0.1 mm.

[0065] The weight content of graphene oxide was adjusted, and the polypropylene film B and the polypropylene film C were prepared with reference to the preparation method of the polypropylene film A.

[0066] The relative permittivity of the prepared polypropylene film A was 32.5, the electrical conductivity was 10.sup.?8 S/m, the thermal conductivity was 0.8 W/m.Math.K, the elastic modulus was 0.75 GPa, and the elongation at break was 126%.

[0067] The relative permittivity of the prepared polypropylene film B was 11, the electrical conductivity was 10.sup.?12 S/m, the thermal conductivity was 0.5 W/m.Math.K, the elastic modulus was 0.65 GPa, and the elongation at break was 155%.

[0068] The relative permittivity of the prepared polypropylene film C was 2.25, the electrical conductivity was 10.sup.?14 S/m, the thermal conductivity was 0.25 W/m.Math.K, the elastic modulus was 0.65 GPa, and the elongation at break was 145%.

Example 2

[0069] As a polypropylene cable protective layer of an example of the present invention, this example only differs from Example 1 in that: the thickness of the dielectric layer accounted for 5% of the thickness of the polypropylene cable protective layer; the thickness of the buffer layer accounted for 17% of the thickness of the polypropylene cable protective layer.

Example 3

[0070] As a polypropylene cable protective layer of an example of the present invention, this example only differs from Example 1 in that: the thickness of the dielectric layer accounted for 8% of the thickness of the polypropylene cable protective layer; the thickness of the buffer layer accounted for 20% of the thickness of the polypropylene cable protective layer.

Example 4

[0071] As a polypropylene cable protective layer of an example of the present invention, this example only differs from Example 1 in that: the thickness of the dielectric layer accounted for 12% of the thickness of the polypropylene cable protective layer; the thickness of the buffer layer accounted for 25% of the thickness of the polypropylene cable protective layer;

Example 5

[0072] As a polypropylene cable protective layer of an example of the present invention, this example only differs from Example 1 in that: the thickness of the polypropylene film A was 0.05 mm; the thickness of the polypropylene film B was 0.05 mm; the thickness of the polypropylene film C was 0.05 mm.

Example 6

[0073] As a polypropylene cable protective layer of an example of the present invention, this example only differs from Example 1 in that: the thickness of the polypropylene film A was 0.15 mm; the thickness of the polypropylene film B was 0.15 mm; the thickness of the polypropylene film C was 0.15 mm.

Example 7

[0074] As a polypropylene cable of an example of the present invention, the cable sequentially included a conductor 1, the polypropylene cable protective layer described in any one of the above examples and an outer insulation screen layer 5 from the inside to the outside. The polypropylene cable protective layer was sequentially composed of a dielectric layer, a buffer layer and an insulating layer from the inside to the outside.

Comparative Example 1

[0075] As a polypropylene cable protective layer of an example of the present invention, this comparative example only differs from Example 1 in that: this comparative example did not include the buffer layer, and the polypropylene cable protective layer of this comparative example was obtained by replacing the polypropylene film B in Example 1 with the polypropylene film C.

Comparative Example 2

[0076] As a polypropylene cable protective layer of an example of the present invention, this comparative example only differs from Example 1 in that: this comparative example did not include the buffer layer and the dielectric layer, and the polypropylene cable protective layer of this comparative example was obtained by replacing the polypropylene film B and the polypropylene film A in Example 1 with the polypropylene film C.

Performance Test.

[0077] 1-2 were combined with conductors to form cable samples. The electrical, thermal and mechanical properties of the cable samples were tested. The results are shown in Table 1. The diameter of the center conductor of the cable samples to be tested is, and the thickness of the polypropylene cable protective layer of the cable samples is.

[0078] The polypropylene cable protective layers of examples 1-6 and comparative examples

TABLE-US-00001 TABLE 1 Properties of the polypropylene cable protective layer Temperature Maximum difference between Thickness of electric inside and outside protective Sample field (kV/mm) (? C.) layer (mm) Example 1 1.4 33? C. 31 Example 2 1.2 31? C. 30 Example 3 1.4 30? C. 32 Example 4 1.1 32? C. 31 Example 5 1.5 32? C. 33 Example 6 1.4 34? C. 32 Comparative 1.8 37? C. 38 example 1 Comparative 2.0 39? C. 41 example 2

[0079] The electric field distribution of Example 1, Comparative example 1, and Comparative example 2 is shown in FIG. 3 below. Under the same insulation thickness, when the same voltage is applied to the central conductor, the maximum electric field of Comparative example 2 (FIG. 3a) can reach 2 kV/mm, and the maximum electric field of Comparative example 1 (FIG. 3b) can still reach 1.8 kV/mm. The uniformity of the electric field in Example 1 (FIG. 3c) has been significantly improved, and the maximum electric field is 1.4 kV/mm. The lower insulation internal electric field means that the outer applied voltage level can be higher, indicating that the polypropylene cable protective layer of the examples is beneficial to improving the voltage level of the cable, and it is beneficial to improving the heat dissipation efficiency. Furthermore, the thickness of the protective layer is smaller, and the bending ability of the cable is better.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention may be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.