CN112094471B

CN112094471B - Composite test material for testing whether cable is water-entering or not and preparation method and application thereof

Info

Publication number: CN112094471B
Application number: CN202011001219.5A
Authority: CN
Inventors: 王宏伟; 袁振; 王少华; 王宇川; 张海凤
Original assignee: Cetc Baoli Beijing Technology Co ltd
Current assignee: Cetc Baoli Beijing Technology Co ltd
Priority date: 2020-09-22
Filing date: 2020-09-22
Publication date: 2022-02-08
Anticipated expiration: 2040-09-22
Also published as: CN112094471A

Abstract

The invention provides a composite test material for testing whether a cable is watered, which comprises the following raw materials: water-absorbing resin, polyurethane acrylic resin, inorganic color developing agent, plasticizer, filler and flame retardant. Wherein the water-absorbing resin is a copolymer taking acrylic acid, acrylamide and 3, 3' -diallyl diphenol as monomers; the inorganic color developing agent is anhydrous copper sulfate or anhydrous cobalt chloride; the filler is hydrophobically modified calcium carbonate. The components play a synergistic role, so that the color of the composite material is changed under the humidity of 35-45%, and various mechanical properties reach the standard. The composite material provided by the invention can be conveniently made into linear or cloth-type materials, when in use, the composite test material is only required to be arranged in a cable, a cable joint is opened when required, and the water inlet condition in the cable can be judged by observing whether the composite material is discolored, so that the composite material is convenient, rapid, stable and reliable.

Description

Composite test material for testing whether cable is water-entering or not and preparation method and application thereof

Technical Field

The invention belongs to the field of electrical equipment and polymer composite materials, and particularly relates to a composite test material for testing whether a cable is watered or not, and a preparation method and application thereof.

Background

China is a power country, and a cable is made of one or more mutually insulated conductors, an insulating layer and a protective layer, and is used for transmitting power or information from one place to a lead at another place. Typically an aerial cable or an underground cable. The cable has high requirements on water resistance and moisture resistance, and once the cable is wetted after water enters, water branch discharge is gradually formed under the action of a high-voltage electromagnetic field, so that the main insulation is damaged until breakdown discharge. Therefore, quality assurance of cable construction and laying is very important for the reliable operation of the cable in the future; the water inlet harm of the power cable is very large, and serious loss and potential safety hazard are brought to national economic construction. In the weather of over-temperature and high humidity in the south, or because the underground cable is buried underground, the moisture is heavy, the cable is stored for too long time, and the water vapor can permeate into the end of the cable due to improper storage; particularly, power cables and high-voltage cables for large-scale engineering in modern cities are laid underground mostly and need to pass through roads, bridges, culverts and the like frequently; due to weather or other reasons, a lot of water is often accumulated in the cable trench, and the situation that the cable head is immersed in the water for construction is inevitable in the laying process; the water inflow of the cable end is caused sometimes under natural disaster conditions, such as rainstorm, flood or the damage of the pipe needed by buried construction due to the water and human factors in the pipe; water enters the cable due to improper protection, untight bundling or damage of the cable head; in addition, the outer sheath and even the steel armor are scraped when the pipe is pulled and penetrated, and the phenomenon is particularly remarkable when mechanical pulling is used. The whole section of circuit is detected after the traditional operating mode generally need to cut off the power supply, and can only detect the change of whole cable resistance and judge whether the cable intakes. Meanwhile, the traditional resistance method cannot determine the water inlet position, and great difficulty is caused to cable maintenance construction.

In order to test whether the cable contains water, a color-changing test paper or reagent is generally used, such as a color-changing silica gel test paper, a silica gel desiccant or a cobalt chloride test paper, and the test paper changes color when absorbing water or meeting water.

CN210053192U discloses a flexible fireproof cable terminal with indication function, which is characterized in that a transparent box body is connected to one side of the terminal fixed near the exposed cable core, and anhydrous copper sulfate powder as a water-absorbing and color-changing desiccant is placed in the box body. CN105575523A discloses a moisture-proof cable, and a test paper for changing color when being dipped in water is arranged on an air extraction valve. CN207165258U discloses a waterproof motor power line, which is internally provided with anhydrous copper sulfate particles that absorb water and change color, and is observed through an external transparent external insulating sleeve layer to judge whether water enters the cable. However, the water-absorbing color-changing material adopting the test paper or the reagent has insufficient mechanical strength, is easy to take out for testing, or is damaged under the installation condition, and is inconvenient to install in the cable. And also. The indicator is greatly affected by the ambient heat and has low resolution. More importantly, inside simply putting into the cable with the test paper that discolours or the reagent that discolours, can take place to discolour promptly under lower humidity environment, the reagent has not reached the super standard value of the inside water content of cable this moment, and the cable detects or changes on the spot this moment, can lead to very big incremental cost. Therefore, simple will absorb water in the color-changing material directly places the cable, troublesome in the technology, to judging whether the cable water content exceeds standard the reliability inadequately moreover, based on this, need to develop a material that can effectively test whether the cable intakes, the comprehensive properties is excellent, and mechanical strength is up to standard, and it is convenient to make, the material of quick reaction.

Disclosure of Invention

In order to overcome the defect that whether water enters the cable or not in the prior art, the invention creatively provides a water-absorbing color-changing composite material prepared from a water-absorbing color-changing material and a high polymer material. The cable is convenient to manufacture into a linear or cloth structure and the like, and provides a method for observing the water-containing condition in the cable from the outside.

Specifically, the invention provides a composite test material for testing whether a cable is in water, which comprises the following raw materials: water-absorbing resin, polyurethane acrylic resin, inorganic color developing agent, plasticizer, filler and flame retardant.

Preferably, the composite test material for testing whether the cable is in water comprises the following raw materials in parts by weight: 30-50 parts of water-absorbing resin, 6-13 parts of polyurethane acrylic resin, 3-5 parts of inorganic color developing agent, 0.5-2 parts of plasticizer, 8-13 parts of filler and 4-10 parts of flame retardant.

The water-absorbing resin is a copolymer taking acrylic acid, acrylamide and 3, 3' -diallyl diphenyl diphenol as monomers.

Wherein the mol ratio of acrylic acid, acrylamide and 3, 3' -diallyl diphenol is 40-60: 8-12:1-2.

The inventors have unexpectedly found that the terpolymer prepared in the above-mentioned ratio as a water absorbent resin has good water absorbency and has a chelating effect on the metal of the inorganic color developer added thereto, and the inorganic portion and the composite portion do not come off after standing for a long time and can be used for a long time. In addition, the weather resistance and the mechanical strength of the resin are improved.

The inorganic color developing agent is selected from anhydrous copper sulfate and anhydrous cobalt chloride.

The inorganic color developing agent can be changed into a colored hydrate form after meeting water. The reaction is sensitive, and the color can be changed under the humidity condition of 50-60% RH in the cable. Whether water enters the cable can be judged by observing the cable with naked eyes by an operator. The method is simple, convenient and quick to operate, and is a method for rapidly and preliminarily judging whether the cable line needs to be overhauled and maintained on site. According to experience, when the humidity inside the cable is close to 60 RH%, the water inlet is hidden and possible. Therefore, the composite material can rapidly judge whether water enters the cable on site without additional equipment.

The inventor just can observe color change by naked eyes when the water content of the composite test material obtained by the invention is slightly lower than the water content of the cable and exceeds the standard by the selection and the dosage of the inorganic color development and the water-absorbent resin, namely the critical humidity for just enabling the material to change color in the cable. This critical humidity should be slightly lower than the excessive value of the water content inside the cable, but not too low, otherwise, discoloration occurs under the condition of relatively low humidity, which may cause operators to misjudge the condition of the water content inside the cable, resulting in meaningless replacement and cable repair. Therefore, the invention provides a composite test material which can change color within the range of 50-60% RH for the first time, the composite test material can be conveniently prepared into a linear or cloth type material and put into a cable, when an operator suspects that the water content in the cable exceeds the standard (such as after raining) or the detection is carried out regularly, the composite test material in the cable joint only needs to be drawn out, whether the color is changed or not is observed, and the preliminary screening can be simply and quickly carried out. The phenomenon that whether the cable is water or not can be judged by only detecting the resistance change of the whole cable is avoided, and the misjudgment phenomenon that the actual water content is not over standard and the color is changed when the color-changing agent or the test paper is put into the cable is avoided.

The plasticizer is selected from phthalate plasticizers, specifically at least one of diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, dibutyl phthalate, diisobutyl phthalate and diisooctyl phthalate.

The filler is hydrophobically modified calcium carbonate, and the hydrophobically modified calcium carbonate is prepared from calcium carbonate and a hydrophobic modifier. The hydrophobic modifier is selected from stearic acid, dimethyl silicone oil and a silane coupling agent; the silane coupling agent is selected from KH560 and KH 570.

The hydrophobic modified carbonic acid is prepared according to the following preparation method: preparing calcium carbonate into slurry, adding a modifier, heating and reacting for 1-3h under the condition of stirring, filtering, washing and drying to obtain the calcium carbonate is added into modifier. The mass ratio of the calcium carbonate to the modifier is 3-6: 1.

After the calcium carbonate is subjected to hydrophobic modification, the contact angle with water is increased, the hydrophobicity is enhanced, the water absorption capacity of the water-absorbent resin is not influenced, and meanwhile, the calcium carbonate is better in compatibility with the resin and is beneficial to increasing the strength of the material.

The flame retardant is selected from phosphine flame retardants and inorganic flame retardants according to the mass ratio of 1-3: 1-3; the phosphine flame retardant is selected from at least one of phosphate, phosphite ester, phosphorus oxide, ammonium polyphosphate, melamine phosphate, melamine pyrophosphate and melamine polyphosphate; the inorganic flame retardant is at least one of magnesium hydroxide, aluminum hydroxide, antimony trioxide and antimony pentoxide.

In one embodiment of the present invention, the water absorbent resin is obtained according to a preparation method comprising the steps of:

(1) feeding aqueous solution of monomer acrylic acid and acrylamide according to a molar ratio, heating and refluxing in an inert atmosphere, and adding an initiator to initiate polymerization for 0.5-1 h;

(2) adding 3, 3' -diallyl diphenyl diphenol, continuously reacting for 4-8h, dehydrating, cooling, washing and drying to obtain the water-absorbent resin.

Further, the initiator is selected from BPO, azobisisobutyronitrile, persulfate-sodium bicarbonate complex; the heating reflux is to 70-90 ℃.

The invention also provides a preparation method of the composite test material, which is one of the following methods:

method a, comprising the steps of: uniformly mixing water-absorbent resin, polyurethane acrylic resin, a plasticizer, a filler and a flame retardant according to a ratio, heating, dehydrating under a vacuum condition, adding an inorganic color developing agent after cooling, uniformly stirring, extruding by an extruder, and air-cooling to obtain the water-absorbent resin;

method B, comprising the steps of: uniformly mixing water-absorbing resin, polyurethane acrylic resin, a plasticizer, a filler and a flame retardant according to a ratio; preparing an inorganic color developing agent into an aqueous solution for later use; adding the mixed material into an extruder for extrusion, cooling by taking a water solution of a chromogenic inorganic salt as a water cooling liquid, and heating and dehydrating in vacuum to obtain the pigment;

method C, comprising the steps of: uniformly mixing water-absorbent resin, polyurethane acrylic resin, a plasticizer, a filler and a flame retardant according to a ratio, adding mixed powder into an extruder for extrusion, spraying an aqueous solution of an inorganic color developing agent on an extrusion-molded material, and heating and dehydrating in vacuum.

In the method A, heating is carried out, and dehydration is carried out under the vacuum condition, specifically heating is carried out to 120-170, and dehydration is carried out for 0.5-2h under the vacuum environment of 0.01-0.1 MPa. The extrusion molding process is well known to those skilled in the art, and specifically, the mixed powder is added into a double-screw extruder, and the length-diameter ratio of screws of the double-screw extruder is controlled to be 30-40: 1, the rotation speed is 300-.

In the method B, the concentration of the aqueous solution of the inorganic color developing agent is prepared to be 10-40 wt%; the extrusion molding condition is that the mixed powder is added into a double-screw extruder, and the length-diameter ratio of screws of the double-screw extruder is controlled to be 30-40: 1, extruding at the rotating speed of 300-; the vacuum drying dehydration is to be heated to 120-170 ℃ for dehydration for 0.5-2h under the vacuum condition of 0.01-0.1 MPa.

In the method C, the concentration of the aqueous solution of the inorganic color developing agent is prepared to be 10-40 wt%; the extrusion molding condition is that the mixed powder is added into a double-screw extruder, and the length-diameter ratio of screws of the double-screw extruder is controlled to be 30-40: 1, extruding at the rotating speed of 300-; the vacuum drying dehydration is to be heated to 120-170 ℃ for dehydration for 0.5-2h under the vacuum condition of 0.01-0.1 MPa.

In the method B and the method C, the inorganic color developing agent is prepared into a water solution with a certain concentration, and the total dosage of the inorganic color developing agent is required to meet the requirement of the composite test material in parts by weight.

The invention also provides the application of the composite test material in testing whether water enters the cable or not, the composite test material is arranged in the cable, the cable joint is opened during detection, and the test material is taken out to observe whether color is changed or not.

The invention has the beneficial effects that:

the composite test material provided by the invention is prepared by extruding the water-absorbent resin, the polyurethane acrylic resin, the inorganic color-developing agent and the filler, has standard mechanical strength, excellent water absorption, obvious color change after washing water, high resolution and strong identification, and can be used for judging the water content and water inlet condition in a cable by naked eyes of an operator according to the color change. The cable water inlet detection method is convenient to maintain and is rapid and convenient.

The composite testing material provided by the invention can be made into a linear type and a cloth type, is simple to construct, and can be coated or wound with other materials to be placed in a cable.

The composite test material provided by the invention can absorb a small amount of moisture and is not released, the inorganic color developing agent and the high polymer material have strong binding force, and the composite test material can be stably used for a long time without precipitation and deterioration after being placed for a long time.

And fourthly, the compound flame retardant is optimized, so that excellent flame retardant effect can be achieved by a small amount of the flame retardant.

And fifthly, the composite test material provided by the invention can be formed by simple processes of extrusion, soaking, spraying, weaving and the like. Simple process, low cost, convenient industrial mass production and good market prospect.

Drawings

FIG. 1 is a schematic view of a test cloth layer wrapped around the outer layer of a cable joint.

Detailed Description

In order that the invention may be further understood, the invention will now be described in detail with reference to specific examples. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated. In the examples of the present invention, the terms "part" and "part", unless otherwise specified, refer to parts by weight and the terms "%" refer to mass%.

The polyurethane acrylic resin is purchased from Pingshan chemical company Limited, Fushan City, with a specific gravity of 1.13 + -0.02/25 deg.C, a functionality of 4, and a viscosity of 25000cps/25 deg.C.

Preparation example 1

(1) Feeding aqueous solution of monomer acrylic acid and acrylamide according to a certain molar ratio, heating the aqueous solution at 90 ℃ under an inert atmosphere for reflux, adding an initiator potassium persulfate-sodium bicarbonate (1:1, w/w) accounting for 0.3 wt% of the total mass of the monomer for initiating polymerization for 0.5 to 1 hour;

(2) adding 3,3 '-diallyl biphenyl diphenol (the molar ratio of acrylic acid to acrylamide to 3, 3' -diallyl biphenyl diphenol is 5:1:0.1), continuously reacting at 80-90 ℃ for 6h, dehydrating, cooling, washing, and drying to obtain the water-absorbent resin, which is hereinafter referred to as water-absorbent resin 1. The weight average molecular weight of the resulting water-absorbent resin was 957200g/mol and PDI was 1.92 as measured by GPC.

Preparation example 2

The other conditions and procedure were the same as in preparation example 1 except that the molar ratio of acrylic acid, acrylamide, and 3, 3' -diallylbiphenyl diol was 5:1: 0.2. The weight average molecular weight of the resulting water-absorbent resin was 1268400g/mol and PDI was 2.13 by GPC measurement. Hereinafter referred to as water absorbent resin 2.

Preparation example 3

The other conditions and procedure were the same as in preparation example 1 except that the molar ratio of acrylic acid, acrylamide, and 3, 3' -diallylbiphenyl diol was 5:1: 0.3. The weight average molecular weight of the resulting water-absorbent resin was 1457100g/mol and PDI was 2.28 by GPC measurement. Hereinafter referred to as water absorbent resin 3.

Preparation example 4

The other conditions and procedure were the same as in preparation example 1 except that no acrylamide was added and 3, 3' -diallylbiphenyl diol was added. The weight average molecular weight of the resulting water-absorbent resin was 483500g/mol and PDI was 1.69 by GPC measurement. Hereinafter referred to as a water absorbent resin 4.

Preparation example 5

Pulping 10 parts of nano calcium carbonate and water together to prepare 15% slurry, adding 25 parts of 10 wt% KH570 ethanol solution, heating to 70 ℃, keeping the temperature, stirring for 2 hours, filtering, washing with distilled water, drying in vacuum, grinding and sieving with a 200-mesh sieve to obtain the modified superfine calcium carbonate.

Example 1

Uniformly mixing 40 parts of water-absorbent resin 1, 10 parts of polyurethane acrylic resin, 1 part of dibutyl phthalate, 8 parts of modified superfine calcium carbonate obtained in preparation example 5, 4 parts of triphenyl phosphate, 2 parts of magnesium hydroxide and 2 parts of aluminum hydroxide according to a ratio, heating to 150 ℃ in a vacuum oven, dehydrating for 2 hours under 0.1MPa, cooling to 40 ℃, adding 5 parts of anhydrous copper sulfate, uniformly stirring, adding into a double-screw extruder, and controlling the length-diameter ratio of a screw of the double-screw extruder to be 30: 1, rotating at 400r/min, setting the temperature of each section at 210 ℃, 220 ℃, 205 ℃ and 210 ℃, extruding, and cooling by air cooling to obtain the linear composite material.

Example 2

50 parts of water-absorbing resin 1, 12 parts of polyurethane acrylic resin, 1.3 parts of diisononyl phthalate, 13 parts of modified superfine calcium carbonate obtained in preparation example 5, 4 parts of triphenyl phosphate and 4 parts of aluminum hydroxide are uniformly mixed according to a ratio and added into a double-screw extruder, and the length-diameter ratio of a screw of the double-screw extruder is controlled to be 30: 1, rotating at 400r/min, setting the temperature of each section at 210 ℃, 220 ℃, 205 ℃ and 210 ℃, extruding the material into a cloth material, cooling the material for 2 hours by using 50 parts of 10 wt% copper sulfate aqueous solution as water cooling liquid, heating the material to 150 ℃ in a vacuum oven, and dehydrating the material for 2 hours under 0.1MPa to obtain the linear composite material.

Example 3

Uniformly mixing 30 parts of water-absorbent resin 1, 6 parts of polyurethane acrylic resin, 1 part of diisononyl phthalate, 10 parts of modified superfine calcium carbonate obtained in preparation example 5, 3 parts of triphenyl phosphate and 3 parts of aluminum hydroxide according to a ratio, adding the mixture into a double-screw extruder, and controlling the length-diameter ratio of a screw of the double-screw extruder to be 30: 1, rotating at 400r/min, setting the temperature of each section to 210 ℃, 220 ℃, 205 ℃ and 210 ℃, extruding the linear material to prepare the linear material into a cloth-shaped material, spraying 50 parts of 10 wt% copper sulfate aqueous solution on the cloth-shaped material, heating the cloth-shaped material to 150 ℃ in a vacuum oven, and dehydrating the cloth-shaped material for 2 hours under 0.1MPa to obtain the linear composite material.

Example 4

The other conditions and procedure were the same as in example 1 except that the water absorbent resin 1 was replaced with the water absorbent resin 2 of equal mass.

Example 5

The other conditions and procedure were the same as in example 1 except that the water absorbent resin 1 was replaced with the water absorbent resin 3 of equal mass.

Example 6

The other conditions and procedure were the same as in example 1 except that the water absorbent resin 1 was replaced with the water absorbent resin 4 of equal mass.

Example 7

The other conditions and procedure were the same as in example 1 except that the modified calcium carbonate obtained in production example 4 was replaced with ultrafine calcium carbonate.

Example 8

The other conditions and procedure were the same as in example 1 except that the flame retardant was 8 parts of triphenyl phosphate, i.e., no inorganic flame retardant was added.

Example 9

The other conditions and procedure were the same as in example 1 except that the flame retardant was 4 parts of magnesium hydroxide and 4 parts of aluminum hydroxide, that is, no organophosphorus flame retardant was added.

Example 10

The other conditions and procedure were the same as in example 1 except that anhydrous copper sulfate was replaced with anhydrous cobalt chloride of equal mass.

Example 11

The other conditions and procedure were the same as in example 1 except that 10 wt% copper sulfate aqueous solution was replaced with 10 wt% cobalt chloride aqueous solution.

Application example 1

The composite materials prepared in the above examples were tested for the following properties. The results are shown in table 1 below:

tensile strength and elongation at break were performed according to GB/T528-2009 standard.

The water absorption capacity is a mass (m)₁) The composite material is placed in an environment with the humidity of RH 70% for overnight standing, and weighed (m)₂) Calculated according to the following formula, which indicates the maximum water adsorption per unit mass:

the water absorption and color change performance is measured by placing the composite material in different humidity environments, and according to the standard that the color change is observed by naked eyes, (the composite material taking copper sulfate as an inorganic color developing agent changes from white to blue, and the composite material taking cobalt chloride as an inorganic color developing agent changes from light blue to pink), and the humidity when the color change which can be observed by the naked eyes of people occurs in the composite material is measured to be used as the sensitivity for measuring the water content of the composite material.

TABLE 1

As can be seen from the data in Table 1, the composite test material obtained by the invention can be conveniently prepared into linear or cloth type materials, and certain mechanical properties are ensured. The visually observable discoloration occurs under humidity conditions of 50-60 RH%. Under the same conditions, the humidity at which discoloration occurs was slightly lower in the composite test material using anhydrous copper sulfate as a color developer than in the composite test material using anhydrous cobalt chloride as a color developer. One skilled in the art can obtain various types of test materials with color change in the humidity range of 50-60 RH% by adjusting the proportion of the monomers and/or the type of the inorganic color developing agent in the preparation of the water absorbent resin. And the selection is flexible according to actual needs.

Application example 2

The obtained linear test composite material is prepared into eyelet fabric with mesh size of 3-5mm and width of 30-170 cm by using YTR11 multi-arm double-layer rapier loom.

Referring to fig. 1, the test cloth layer is wound on the outer layer of the cable joint after the insulating tape layer is wound, 1-2 circles are preferably used, the joint is preferably reserved at one end of the cable joint, then the armor belt layer is wound, the test cloth layer is laid, the cable joint is opened when needed, lines on the test cloth are drawn out for detection, and whether the water content inside the cable exceeds the standard or not can be judged according to whether the color of the cloth type composite material changes or not.

In the section B of the commercial power engineering A, the composite test material obtained in the embodiment 1 is made into mesh cloth according to the method, and the mesh cloth is wound on the outer layer of the cable joint after the insulating tape layer is wound, and then an armor tape layer is wound. And opening the cable joint for detection after 2 months, finding that the composite test material is not discolored, preliminarily judging that no water enters the cable, and finding that the actual humidity in the cable is 30 RH% through detection.

In the section C of the commercial power engineering A, the composite test material obtained in the embodiment 10 is made into mesh cloth according to the method, and the mesh cloth is wound on the outer layer of the cable joint after the insulating tape layer is wound, and then an armor tape layer is wound. Opening cable joint after pipeline well intake several days, detecting, finding that composite test material becomes blue, preliminarily judge that the inside humidity of cable is near 60 RH%, through detecting, find that the inside actual humidity of cable is 62 RH%, and the table 1 condition accords with.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims

1. A composite test material for testing whether a cable is subjected to water inflow comprises the following raw materials in parts by weight: 30-50 parts of water-absorbing resin, 6-13 parts of polyurethane acrylic resin, 3-5 parts of inorganic color developing agent, 0.5-2 parts of plasticizer, 8-13 parts of filler and 4-10 parts of flame retardant; the water-absorbing resin is a copolymer taking acrylic acid, acrylamide and 3, 3' -diallyl diphenol as monomers; the mol ratio of acrylic acid, acrylamide and 3, 3' -diallyl diphenyl diphenol is 40-60: 8-12: 1-2;

the inorganic color developing agent is selected from anhydrous copper sulfate and anhydrous cobalt chloride;

the filler is hydrophobically modified calcium carbonate, and the hydrophobically modified calcium carbonate is prepared from calcium carbonate and a hydrophobic modifier;

the preparation method of the composite test material is one of the following methods A, B or C:

2. The composite test material of claim 1, wherein the plasticizer is selected from at least one of diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, dibutyl phthalate, diisobutyl phthalate, and diisooctyl phthalate.

3. The composite test material of claim 1, wherein the hydrophobic modifier is selected from the group consisting of stearic acid, dimethicone, silane coupling agents; the silane coupling agent is selected from KH560 and KH 570; the mass ratio of the calcium carbonate to the hydrophobic modifier is 3-6: 1.

4. The composite test material of claim 1, wherein the flame retardant is selected from the group consisting of phosphine based flame retardants and inorganic flame retardants in a mass ratio of 1-3: 1-3; the phosphine flame retardant is selected from at least one of phosphate, phosphite ester, phosphorus oxide, ammonium polyphosphate, melamine phosphate, melamine pyrophosphate and melamine polyphosphate; the inorganic flame retardant is at least one of magnesium hydroxide, aluminum hydroxide, antimony trioxide and antimony pentoxide.

5. The composite test material as described in claim 1, wherein in the method A, the heating is performed under vacuum to dehydrate at a temperature of 120 ℃ to 170 ℃ for 0.5 to 2 hours under a vacuum environment of 0.01 to 0.1 MPa; the extrusion molding is to add the mixed powder into a double-screw extruder, and control the length-diameter ratio of screws of the double-screw extruder to be 30-40: 1, the rotating speed is 300-;

6. Use of a composite test material according to any one of claims 1 to 5 for testing the interior of a cable for water ingress by loading the composite test material into the interior of the cable, opening the cable joint when testing, and removing the test material to see if discoloration has occurred.