Radiation-resistant modified polypropylene insulated cable material and preparation method thereof

Abstract

A formula of the radiation-resistant modified polypropylene insulated cable material comprises the following components in parts by mass: 100 parts of co-polypropylene, 0.5-0.8 part of an antioxidant, 0.2-0.5 part of an anti-copper agent and 3-6 parts of organically coated modified lanthanum oxide. The machine-coated modified lanthanum oxide is powder which is coated with polystyrene on the surface and has a core-shell structure. The preparation method of the cable material comprises the following steps: firstly, weighing the raw materials according to a formula; then, after the raw materials are fully stirred, the temperature of the materials is kept and controlled to be 40-50 DEG C; and finally, mixing and granulating to obtain the insulated cable material. According to the invention, the defect that the dispersivity of the doped lanthanum oxide powder in the composite material is influenced by the irregular morphology of the doped lanthanum oxide powder is overcome, and the problem of insufficient interaction between rays and the rare earth filler caused by non-uniform distribution of the rare earth filler in the composite material is solved; and degradation of related properties such as mechanical properties and electrical properties caused by compatibility problems is also avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and specifically relates to a radiation-resistant modified polypropylene insulating cable material and a preparation method thereof. Background Art

[0002] With the development of fields such as aerospace and nuclear technology and the extensive utilization of nuclear energy, higher requirements are also put forward for the performance of nuclear radiation shielding materials. Gamma rays generated in nuclear reactions have strong penetration ability and great harm. Especially for polymer materials, after being irradiated by high-energy rays, the macromolecular chains of polymers break and decompose, resulting in significant decline in the mechanical properties, electrical insulation properties and other properties of the materials, leading to cable insulation failure and the loss of relevant functions and protection effects of products. Therefore, it is crucial to develop a material that can withstand gamma radiation.

[0003] As a general-purpose plastic, polypropylene has excellent mechanical properties, and its dielectric constant and dielectric loss factor are both good at room temperature and high temperature. At present, it has been widely studied and used as a cable insulation material. However, the presence of side methyl groups in polypropylene causes tertiary carbon atoms to appear alternately on the molecular chain, and tertiary carbon atoms are extremely prone to oxidation reactions, resulting in poor oxidation resistance and radiation resistance of polypropylene. After polypropylene is irradiated, the oxidation of tertiary carbon atoms forms free radicals, which will accelerate the degradation of the material, cause performance deterioration, and ultimately lead to failure.

[0004] Rare earth elements have a high neutron absorption cross-section and high atomic number, and have gradually been taken seriously by researchers and applied to the research and development of neutron and gamma radiation shielding materials. The doping of rare earth elements can significantly improve the structural stability, optical properties and radiation shielding performance of composite materials. Most of the rare earth fillers reported in the literature for doping are fragments with irregular morphologies, which affect the dispersion of fillers in composite materials. When incident gamma rays react with matter, there may be problems of insufficient reaction, and the problem of insufficient interaction between gamma rays and rare earth fillers due to uneven distribution of rare earth fillers in the composite material.

[0005] In addition, the problems of interfacial compatibility and phase separation between inorganic rare earth fillers and polymers increase the difficulty of their uniform dispersion in the polymer matrix. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a radiation-resistant modified polypropylene insulating cable material and a preparation method thereof.

[0007] The radiation-resistant modified polypropylene insulating cable material of the present invention has the following formula according to mass parts:

[0008] 100 parts of copolymerized polypropylene,

[0009] 0.5 - 0.8 parts of antioxidant,

[0010] 0.2 - 0.5 parts of copper-resistant agent,

[0011] 3 - 6 parts of organically coated and modified lanthanum oxide;

[0012] The organically coated and modified lanthanum oxide is a powder with a core-shell structure having polystyrene coated on its surface.

[0013] The preparation steps of the organically coated and modified lanthanum oxide include:

[0014] (I) Preparation of silane-modified powder:

[0015] 1.1) Place the nano lanthanum oxide powder in a stirring device and preheat it to 80 °C;

[0016] 1.2) Under the condition of constant temperature of 80 °C, spray a silane coupling agent (such as silane coupling agent 172, i.e., vinyltris-(2-methoxyethoxy)-silane) onto the nano lanthanum oxide powder, stir while spraying until the stirring is sufficient;

[0017] 1.3) Obtain the silane-modified powder after cooling;

[0018] (II) Preparation of organically coated and modified lanthanum oxide powder:

[0019] 2.1) Add the silane-modified powder obtained in step (I) to the ethanol / water mixed solution and stir evenly;

[0020] 2.2) Then add styrene monomer and initiator (such as azobisisobutyronitrile), continue to stir, and gradually heat to 70 °C, and react fully under the condition of constant temperature of 70 °C;

[0021] 2.3) Filter and wash the reactants, and then evacuate to obtain the organically coated powder;

[0022] 2.4) Place the powder obtained in step 2.3) in an oven for drying and pulverization to obtain the organically coated and modified lanthanum oxide powder.

[0023] Furthermore, the formulation by mass parts further includes 1 - 2 parts of chain transfer agent.

[0024] Preferably, the copolymerized polypropylene is block copolymerized polypropylene PPB.

[0025] Preferably, the antioxidant is a phosphite antioxidant (such as antioxidant 168), a phenolic antioxidant (such as antioxidant 1010), or a mixture of the two.

[0026] Preferably, the chain transfer agent is 2,4-diphenyl-4-methyl-1-pentene.

[0027] Specifically, in step (I),

[0028] 1.2) Spray the silane coupling agent using an atomizing spray device for 5 - 8 minutes; the rotational speed of the stirring equipment is 500 - 800 rpm, and the stirring time is 20 - 30 minutes;

[0029] 1.3) Cool to room temperature to obtain the silane - modified powder;

[0030] In step (two),

[0031] 2.1) For every 10 g of the silane - modified powder, there is a corresponding 200 ml of ethanol / water mixed solution; in the ethanol / water mixed solution, the volume ratio of ethanol to water is 3:2;

[0032] 2.2) For every 10 g of the silane - modified powder, there is a corresponding 10 ml of styrene monomer and 1.5 g of azobisisobutyronitrile; the reaction time is 4 hours;

[0033] 2.4) The drying temperature is 100 °C and the drying time is 24 hours.

[0034] The preparation method of the radiation - resistant modified polypropylene insulating cable material of the present invention includes the following steps:

[0035] First, weigh the raw materials according to the formula;

[0036] Then, after fully stirring the raw materials, keep the material temperature controlled at 40 - 50 °C;

[0037] Finally, mix and pelletize to obtain the insulating cable material.

[0038] Preferably, the raw material stirring is carried out using a high - speed mixer for 10 - 15 minutes;

[0039] The mixing and pelletizing is carried out using a twin - screw extruder; the temperature settings of each zone of the twin - screw extruder are as follows: Zone 1 of the barrel: 150 ± 5 °C, Zone 2 of the barrel: 160 ± 5 °C, Zone 3 of the barrel: 170 ± 5 °C, Zone 4 of the barrel: 180 ± 5 °C, Zone 5 of the barrel: 190 ± 5 °C, Zone 6 of the barrel: 195 ± 5 °C, Zone 7 of the barrel: 200 ± 5 °C, Zone 8 of the barrel: 205 ± 5 °C, Zone 9 of the barrel: 210 ± 5 °C, and the head: 210 ± 5 °C.

[0040] As a preferred formula, by mass: 100 parts of copolymerized polypropylene, 0.6 part of antioxidant, 0.3 part of copper - resistant agent, 3 parts of organically - coated modified lanthanum oxide powder, and 1 - 2 parts of chain transfer agent. Among them, the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 with a mass ratio of 1:1 - 1:2.

[0041] The principle of the present invention is explained as follows:

[0042] Preferably, nanoscale lanthanum oxide (such as the corresponding products of Beijing Decodaojin Technology) is used as the inorganic rare earth powder. The powder is surface-treated with 172 silane coupling agent to reduce the surface energy of the nano powder, creating conditions for improving the dispersibility. A certain amount of modified nano powder is dispersed in an ethanol / water mixed solvent and stirred at high speed to form a suspension. Styrene monomer and initiator are added, and the reaction is carried out under heating and stirring conditions to prepare a powder with a core-shell structure coated with polystyrene on the surface. After drying the powder, it is ground and sieved to obtain a powder with a controllable particle size. The powder prepared by the above modification method greatly reduces the surface energy and significantly improves its dispersibility in the resin matrix. At the same time, the low-molecular polystyrene coated on the surface of the powder has better tolerance to electromagnetic radiation due to the presence of benzene rings than ordinary polymers.

[0043] In addition to the absorption and shielding effect of nano lanthanum oxide on nuclear radiation, in order to further slow down the accelerated degradation reaction caused by the free radicals formed by the oxidation of tertiary carbon atoms due to radiation, a chain transfer agent is introduced into the resin. Under the normal use range of the material, it can effectively and quickly terminate the free radical reaction, form a stable structure, and delay and prevent the degradation of polypropylene.

[0044] Through surface modification and organic coating treatment, the present invention overcomes the defect that the irregular morphology of the doped rare earth powder affects its dispersion in the composite material, and solves the problem that the interaction between the rays and the rare earth filler is insufficient due to the uneven distribution of the rare earth filler in the composite material.

[0045] In addition, the problems of interface compatibility and phase separation between the organically coated inorganic powder (rare earth powder) and the polymer are solved, avoiding the deterioration of related properties such as mechanical properties and electrical properties caused by compatibility problems. At the same time, the organically coated resin contains a benzene ring structure, which can further improve the radiation resistance of the material.

[0046] The present invention also innovatively introduces a chain transfer agent into the thermoplastic polypropylene material, and stabilizes its chemical structure by terminating the free radical reaction, making the polypropylene material have more excellent radiation resistance. Specific embodiments

[0047] The present invention will be further described below in conjunction with specific embodiments.

[0048] In this experiment, the preparation steps of the sample are as follows:

[0049] Step 1: Prepare silane-modified powder A:

[0050] Nanoscale lanthanum oxide is placed in a stirring device and preheated to 80 °C;

[0051] After the preheating temperature reaches the required value, place the silane in the spraying device. While stirring the powder, turn on the atomizing spraying device. The spraying time is 5 - 8 min, the rotation speed of the mixer is 500 - 800 rpm, and the stirring time is 20 - 30 min;

[0052] After cooling, obtain the silane - modified powder A.

[0053] Step Two: Prepare the organically - coated modified lanthanum oxide powder B:

[0054] Add 10 g of powder A to 200 ml of ethanol / water mixed solution (ethanol / water volume ratio 3:2), and stir evenly;

[0055] Then add 10 ml of styrene monomer and 1.5 g of azobisisobutyronitrile and continue stirring; during the stirring process, gradually heat to 70 °C and carry out a constant - temperature reaction for 4 h;

[0056] Filter and wash the reactants, and then evacuate to obtain the organically - coated powder;

[0057] Place the powder in an oven at 100 °C and bake for 24 h. Use a jet mill to crush the powder to obtain the organically - coated modified lanthanum oxide (powder B).

[0058] Step Three: Make the insulating material:

[0059] Weigh the prepared powder B, polypropylene resin, antioxidant, copper - resistant agent, and chain - transfer agent according to the formula weight in sequence, place them in a high - speed mixer and stir for 10 - 15 min. After stirring, control the material temperature at 40 - 50 °C;

[0060] Finally, use a twin - screw extruder to mix and pelletize the materials to obtain the radiation - resistant polypropylene insulating material. The temperature settings for each zone of the twin - screw extruder are as follows: Zone 1 of the barrel: 150 ± 5 °C, Zone 2 of the barrel: 160 ± 5 °C, Zone 3 of the barrel: 170 ± 5 °C, Zone 4 of the barrel: 180 ± 5 °C, Zone 5 of the barrel: 190 ± 5 °C, Zone 6 of the barrel: 195 ± 5 °C, Zone 7 of the barrel: 200 ± 5 °C, Zone 8 of the barrel: 205 ± 5 °C, Zone 9 of the barrel: 210 ± 5 °C, and the head: 210 ± 5 °C.

[0061] In this experiment, the basic formula (by mass) is: 100 parts of copolymerized polypropylene, 0.5 - 0.8 parts of antioxidant, 0.2 - 0.5 parts of copper - resistant agent, 1 - 2 parts of chain - transfer agent, and 3 - 6 parts of powder B (organically - coated modified lanthanum oxide powder).

[0062] In this experiment, the copolymerized polypropylene used was block copolymerized polypropylene PPB; the phosphite antioxidant used was antioxidant 168, the phenolic antioxidant used was antioxidant 1010, and antioxidant 1010 and antioxidant 168 were in a ratio of 1:1 to 1:2; the copper inhibitor (metal inhibitor) used was antioxidant MD1024; the chain transfer agent used was the N0FMER MSD product (2,4-diphenyl-4-methyl-1-pentene, CAS registration number 6362-80-7) of NOF Corporation; the nano lanthanum oxide used was the product with the model DK-La203-500 of Beijing Decode Gold Technology Co., Ltd.

[0063] Example 1 (parts by mass)

[0064]

[0065] Example 2 (parts by mass)

[0066]

[0067]

[0068] Example 3 (parts by mass)

[0069]

[0070] Example 4 (parts by mass)

[0071]

[0072] Comparative Example 1 (parts by mass)

[0073] PPB (M02, Sinopec) 100 Antioxidant (1010 / 168, Stepan) 0.6

[0074] Copper inhibitor (1024, BASF) 0.3 Comparative Example 2 (parts by mass)

[0075]

[0076] Comparative Example 3 (parts by mass)

[0077]

[0078] The test results of the specimens of each example and comparative example are shown in Table 1.

[0079]

Claims

1. A radiation-resistant modified polypropylene insulated cable material, characterized in that The formula is based on mass parts: 100 parts of copolymerized polypropylene, 0.5-0.8 parts of antioxidant, 0.2-0.5 parts of anti-copper agent, 3 to 6 parts of organically coated modified lanthanum oxide.

2. The radiation-resistant modified polypropylene insulated cable material according to claim 1, characterized in that Organically coated modified lanthanum oxide is a powder with a core-shell structure and polystyrene coated on the surface.

3. The radiation-resistant modified polypropylene insulated cable material according to claim 1, characterized in that The preparation steps of the organically coated modified lanthanum oxide include: (I) Preparation of silane-modified powder: 1.1) Preheat the nano-lanthanum oxide powder to 80°C in a stirring device; 1.2) At a constant temperature of 80°C, spray the silane coupling agent onto the surface of the nano-lanthanum oxide powder while stirring thoroughly; 1.3) After cooling, a silane-modified powder is obtained; (II) Preparation of organically coated modified lanthanum oxide powder: 2.1) Add the silane-modified powder obtained in step (i) to the ethanol / water mixed solution and stir evenly; 2.2) Add styrene monomer and initiator, continue stirring, and gradually heat to 70°C to fully react at a constant temperature of 70°C; 2.3) Filter and wash the reactants and then evacuate them; 2.4) drying and crushing the product obtained in step 2.3) to obtain organic-coated modified lanthanum oxide powder.

4. The radiation-resistant modified polypropylene insulated cable material according to claim 1, characterized in that The formula also includes 1 to 2 parts of chain transfer agent by weight.

5. The radiation-resistant modified polypropylene insulated cable material according to claim 1 or 4, characterized in that The copolymerized polypropylene is block copolymerized polypropylene PPB; and the antioxidant is a mixture of a phosphite antioxidant and a phenolic antioxidant.

6. The radiation-resistant modified polypropylene insulated cable material according to claim 4, characterized in that The antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1 to 1:2; and the chain transfer agent is 2,4-diphenyl-4-methyl-1-pentene.

7. The radiation-resistant modified polypropylene insulated cable material according to claim 3, characterized in that In step (a), 1.2) Use an atomizing spray device to spray the silane coupling agent for 5 to 8 minutes; the stirring equipment speed is 500 to 800 rpm, and the stirring time is 20 to 30 minutes; 1.3) Cooling to room temperature to obtain silane-modified powder; In step (ii), 2.1) Every 10g of silane-modified powder corresponds to 200ml of ethanol / water mixed solution; the volume ratio of ethanol / water in the ethanol / water mixed solution is 3:2; 2.2) Every 10g of silane-modified powder corresponds to 10ml of styrene monomer and initiator; the reaction time is 4h; 2.4) The drying temperature is 100°C and the drying time is 24h.

8. The radiation-resistant modified polypropylene insulated cable material according to claim 3 or 7, characterized in that In step 1.2), the silane coupling agent is 172 silane coupling agent; in step 2.2), the initiator is azobisisobutyronitrile; and every 10g of silane-modified powder corresponds to 1.5g of azobisisobutyronitrile.

9. A method for preparing the radiation-resistant modified polypropylene insulated cable material according to any one of claims 1 to 8, characterized in that the steps include: First, weigh the raw materials according to the recipe; Then, after fully stirring the raw materials, keep the material temperature at 40-50°C; Finally, the insulating cable material is obtained by mixing and granulating.

10. The method for preparing the radiation-resistant modified polypropylene insulated cable material according to claim 9, characterized in that The raw materials are stirred using a high-speed mixer for 10 to 15 minutes; A twin-screw extruder is used for mixing and granulation; the temperature of each zone of the twin-screw extruder is set as follows: barrel zone 1: 150±5℃, barrel zone 2: 160±5℃, barrel zone 3: 170±5℃, barrel zone 4: 180±5℃, barrel zone 5: 190±5℃, barrel zone 6: 195±5℃, barrel zone 7: 200±5℃, barrel zone 8: 205±5℃, barrel zone 9: 210±5℃, and die head: 210±5℃.

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