阅读说明：本技术 一种极性翻转工况下聚丙烯电缆材料及其制备方法、用途 (Polypropylene cable material under polarity reversal working condition, and preparation method and application thereof ) 是由 杜伯学 刘畅 李忠磊 于 2020-04-10 设计创作，主要内容包括：本发明公开了一种极性翻转工况下聚丙烯电缆材料及其制备方法、用途。所述聚丙烯复合绝缘材料的质量分数100％计,包括99.5-99.7％的聚丙烯基体和0.3-0.5％的硫代双酚类化合物填料。其中所述的硫代双酚类化合物一方面其中的受阻酚单元通过质子转移捕获基体中产生的自由基,抑制聚丙烯材料内部低密度区的形成,进而抑制局部放电的发生；另一方面为聚丙烯基体提供多尺度的陷阱分布,减小碰撞电离以及高能电荷运动对分子链的破坏,从而增大击穿强度。本发明所制备的聚丙烯热塑性电缆绝缘材料的击穿强度在极性翻转后下降幅度较小,相比于纯等规聚丙烯依然保持了良好的绝缘性能,适用于高压直流电缆中。(The invention discloses a polypropylene cable material under a polarity reversal working condition, and a preparation method and application thereof. The polypropylene composite insulating material comprises 99.5-99.7% of polypropylene matrix and 0.3-0.5% of thiobisphenol compound filler by mass fraction of 100%. On one hand, the hindered phenol unit of the thiobisphenol compound traps free radicals generated in a matrix through proton transfer to inhibit the formation of a low-density area in a polypropylene material, so that the occurrence of partial discharge is inhibited; on the other hand, multi-scale trap distribution is provided for the polypropylene matrix, so that damage of impact ionization and high-energy charge movement to molecular chains is reduced, and the breakdown strength is increased. The breakdown strength of the polypropylene thermoplastic cable insulation material prepared by the invention is reduced to a smaller extent after polarity inversion, and the polypropylene thermoplastic cable insulation material still maintains good insulation performance compared with pure isotactic polypropylene, and is suitable for high-voltage direct-current cables.)

1. The polypropylene cable material under the working condition of polarity inversion is characterized in that the polypropylene composite insulating material comprises 99.5-99.7% of a polypropylene matrix and 0.3-0.5% of thiobisphenol compound filler by mass fraction of 100%.

2. The polypropylene cable material according to claim 1, wherein the polypropylene matrix is isotactic polypropylene.

3. The polypropylene cable material according to claim 1, wherein the additive is one or both of thiobis phenolic compounds 4,4 '-thiobis (6-tert-butyl-3-methylphenol) and 4,4' -thiobis- (2-methyl-6-tert-butylphenol).

4. The method for preparing polypropylene cable material according to claim 1, comprising the steps of:

A. mixing isotactic polypropylene particles on a double-roller mill for 10 minutes to fully melt the isotactic polypropylene particles, wherein the temperature is set to be 200 ℃;

B. mixing is suspended, and additive powder is mixed with polypropylene to ensure that the additive is fully melted in the isotactic polypropylene;

C. the mixture is continuously and fully mixed on a double-roller machine for 15 minutes, the temperature is set to be 200 ℃, and then the mixture is cut into a plurality of parts, wherein each part is 1-2 g;

D. degassing the mixed material, cooling, and performing hot press molding on a tablet press.

5. The method for preparing polypropylene cable material according to claim 4, wherein the hot pressing comprises the steps of:

A. placing a part of the mixed material in a mold, wherein the diameter of the mold is 70mm, and the depth of the mold is 70/250 μm;

B. hot pressing the mixed material in a tablet press for 15 minutes, wherein the temperature is set to 200 ℃, and the pressure is set to 20 MPa;

C. the circulating water tank was opened, the tablet press temperature was quenched from 200 ℃ to 80 ℃ in 1 minute and removed.

6. Use of a polypropylene cable material according to any one of claims 1 to 3 wherein the dielectric properties under a polarity reversal condition are improved.

Technical Field

The invention belongs to the technical field of electric and electronic material preparation, and particularly relates to a polypropylene cable material under a polarity reversal working condition, and a preparation method and application thereof.

Background

The polypropylene is an environment-friendly high-voltage direct-current cable insulating material, and compared with the traditional crosslinked polyethylene insulating material, the polypropylene has the advantages of high working temperature, low conductivity, high breakdown strength, difficulty in accumulating space charge and the like. However, in conventional high-voltage direct-current transmission, there is a working condition of voltage polarity reversal, which is disadvantageous to long-term stable operation of the high-voltage direct-current cable.

After the polarity is reversed, the external electric field and space charges accumulated in the material before the polarity is reversed distort the local electric field, so that the breakdown strength of the insulation material after the polarity is reversed is reduced. The breakdown performance of the high-voltage direct-current cable after polarity inversion is improved, on one hand, the breakdown strength of the high-voltage direct-current cable can be improved through modification when the polarity inversion does not occur, on the other hand, the space charge accumulation of the high-voltage direct-current cable under an externally applied electric field needs to be reduced, and the distortion degree of the electric field after the polarity inversion is weakened.

Disclosure of Invention

The invention aims to improve the breakdown strength of a polypropylene thermoplastic cable under a polarity reversal working condition, and provides a polypropylene cable material for improving the dielectric property under the polarity reversal working condition, and a preparation method and application thereof. The thiobisphenol compound is added into the isotactic polypropylene, on one hand, the hindered phenol unit in the isotactic polypropylene captures free radicals generated in a matrix through proton transfer, so that the formation of a low-density area in the polypropylene material is inhibited, and the occurrence of partial discharge is further inhibited; on the other hand, multi-scale trap distribution is provided for the polypropylene matrix, so that damage of impact ionization and high-energy charge movement to molecular chains is reduced, and the breakdown strength is increased.

The invention is realized by the following technical scheme: the polypropylene cable material under the working condition of polarity inversion comprises 99.5-99.7% of a polypropylene matrix and 0.3-0.5% of thiobisphenol compound filler, wherein the mass fraction of the polypropylene composite insulating material is 100%.

The polypropylene matrix is isotactic polypropylene.

The additive is one or two of thiobisphenol compounds 4,4 '-thiobis (6-tert-butyl-3-methylphenol) and 4,4' -thiobis- (2-methyl-6-tert-butylphenol).

The invention also provides a preparation method of the polypropylene cable material under the working condition of polarity inversion, which comprises the following steps:

A. mixing isotactic polypropylene particles on a double-roller mill for 10 minutes to fully melt the isotactic polypropylene particles, wherein the temperature is set to be 200 ℃;

B. mixing is suspended, and additive powder is mixed with polypropylene to ensure that the additive is fully melted in the isotactic polypropylene;

C. the mixture is continuously and fully mixed on a double-roller machine for 15 minutes, the temperature is set to be 200 ℃, and then the mixture is cut into a plurality of parts, wherein each part is 1-2 g;

D. degassing the mixed material, cooling, and performing hot press molding on a tablet press.

The hot pressing comprises the following steps:

A. placing a part of the mixed material in a mold, wherein the diameter of the mold is 70mm, and the depth of the mold is 70/250 μm;

B. hot pressing the mixed material in a tablet press for 15 minutes, wherein the temperature is set to 200 ℃, and the pressure is set to 20 MPa;

C. the circulating water tank was opened, the tablet press temperature was quenched from 200 ℃ to 80 ℃ in 1 minute and removed.

The third technical scheme of the invention is to provide the application of the polypropylene cable material, and improve the dielectric property under the working condition of polarity inversion.

The invention adopts thiobisphenol compounds with dual functions of providing multi-scale traps and capturing free radicals as fillers, adopts isotactic polypropylene with excellent electrical property as a matrix, and prepares the polypropylene cable material with improved dielectric property under the working condition of polarity inversion by a melt blending method.

Compared with the prior art, the invention has the following beneficial effects:

1. on one hand, the hindered phenol unit captures free radicals generated in a matrix through proton transfer to inhibit the formation of a low-density area in the polypropylene material, and further inhibit the occurrence of partial discharge; on the other hand, multi-scale trap distribution is provided for the polypropylene matrix, so that damage of impact ionization and high-energy charge movement to molecular chains is reduced, and the breakdown strength is increased.

2. The thiobisphenol compound is selected as the filler, the melting point of the thiobisphenol compound is close to that of isotactic polypropylene, and the compatibility of the filler and a matrix is improved.

3. After the direct current breakdown strength test before and after polarity inversion at 30 ℃, the polypropylene insulating material for the high-voltage direct current cable prepared by the invention still has higher direct current breakdown strength after polarity inversion.

4. Through space charge and electric field tests at 30 ℃, the polypropylene insulating material for the high-voltage direct-current cable prepared by the invention has less space charge accumulation and no serious distortion of an electric field.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 shows isotactic polypropylene (a) according to the present invention, two thiobisphenols: the molecular formulae (c) of 4,4 '-thiobis (6-tert-butyl-3-methylphenol) (b) and 4,4' -thiobis- (2-methyl-6-tert-butylphenol);

FIG. 2 is a diagram of a device for measuring the DC breakdown field strength of a material under voltage polarity reversal according to the present invention;

FIG. 3 is a graph of the DC breakdown strength of the polymer composite prepared in example 1 after pre-application of an electric field of-50 kV/mm at 30 ℃ for 0-60 minutes with reversal of polarity;

FIG. 4 is a graph showing the space charge distribution and the electric field distribution at 30 ℃ of the polymer composite prepared in example 1:

(a) polypropylene;

(b) polypropylene-filler 1;

(c) polypropylene-filler 2.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

The experimental test samples of the present invention use an electroacoustic pulse method to measure space charge.