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CN-121975332-A - High-temperature-resistant liquid silicone rubber and preparation method thereof

CN121975332ACN 121975332 ACN121975332 ACN 121975332ACN-121975332-A

Abstract

The invention discloses high-temperature-resistant liquid silicone rubber and a preparation method thereof, belongs to the technical field of organic silicon high polymer materials, and aims to solve the problems that the main chain of the traditional liquid silicone rubber is easy to be bitten and degraded in a high-temperature environment, and the side chain is easy to oxidize, so that the material is fragile and disabled. The core of the invention is to synthesize a special raw rubber main body, wherein a phenylene block is introduced into a main chain of a polymer to block continuous degradation of a silicon-oxygen bond, and a silafluorene group is introduced into a side chain through hydrosilylation to shield thermal oxygen attack. By matching the nano cerium dioxide free radical capturing agent with a specific phenyl crosslinking system, the obtained liquid silicone rubber remarkably improves the heat-resistant air aging resistance on the premise of keeping good fluidity and optical transparency, and can resist high temperature without obvious hardening or cracking.

Inventors

  • LU HAO
  • LU GUOJIAN
  • BI LIQUN

Assignees

  • 浙江聚鼎新材料科技有限公司

Dates

Publication Date
20260505
Application Date
20260203

Claims (10)

  1. 1. The high-temperature-resistant liquid silicone rubber is characterized by comprising, by weight, 100 parts of a silafluorene-phenylene modified raw rubber, 20-50 parts of a reinforcing filler, 1-5 parts of a heat resistant agent, 1-10 parts of a cross-linking agent, 0.05-0.3 part of a catalyst and 0.02-0.1 part of an inhibitor, wherein a phenylene block is introduced into a main chain of the silafluorene-phenylene modified raw rubber polymer, and a silafluorene group is introduced into a side chain through hydrosilylation.
  2. 2. The high temperature resistant liquid silicone rubber of claim 1 wherein said phenylene block is The silafluorene group is 。
  3. 3. The high-temperature-resistant liquid silicone rubber according to claim 1, wherein the reinforcing filler is gas-phase white carbon black subjected to surface hydrophobic treatment by hexamethyldisilazane, octamethylcyclotetrasiloxane or dimethyldichlorosilane treatment agent, the heat-resistant agent is a dispersion system taking nano cerium dioxide solid particles as an effective component, the particle size is 10-50nm, the crosslinking agent is hydrogen-containing polymethylphenylhydrosiloxane, the hydrogen content is 0.5-1.2wt%, the catalyst is Karstedt catalyst, the platinum content is 2wt%, and the inhibitor is an alkynol inhibitor, and specifically comprises 1-ethynyl-cyclohexanol, 2-methyl-3-butynyl-2-ol or 3, 5-dimethyl-1-ethynyl-3-ol.
  4. 4. A method for preparing a high temperature resistant liquid silicone rubber according to any one of claims 1 to 3, comprising the steps of: S1, respectively preparing a hard segment prepolymer containing phenylene and a side chain functionalized base polymer, and then carrying out addition chain extension reaction on the hard segment prepolymer containing phenylene and the side chain functionalized base polymer to obtain the silicon-containing fluorene-phenylene modified raw rubber; S2, mixing the silicon-containing fluorene-phenylene modified raw rubber with the reinforcing filler and the heat-resistant agent, performing heat treatment, cooling, adding the cross-linking agent, the catalyst and the inhibitor, and defoaming and filtering to obtain a finished product.
  5. 5. The method for preparing the high-temperature-resistant liquid silicone rubber according to claim 4, wherein the preparation of the phenylene hard segment-containing prepolymer in the step S1 is specifically carried out by carrying out an addition reaction on 1, 4-bis (dimethylvinylsilyl) benzene and a dihydro-terminated polysiloxane oligomer under the action of a Karstedt catalyst, controlling the molar ratio of Si-H to Si-Vi in the system to be 1.3:1, controlling the reaction temperature to be 90 ℃, and pumping out low-boiling residues after the reaction is finished, wherein the dihydro-terminated polysiloxane oligomer has a number average molecular weight of 200-300g/mol.
  6. 6. The method for preparing high temperature resistant liquid silicone rubber according to claim 5, wherein the conditions for pumping out low boiling point substances are-0.09 MPa and 120 ℃.
  7. 7. The method for preparing high temperature resistant liquid silicone rubber according to claim 4, wherein the preparation of the side chain functionalized base polymer in step S1 comprises ring-opening polymerization of octamethyl cyclotetrasiloxane, tetramethyl tetravinyl cyclotetrasiloxane and methylphenyl cyclosiloxane under the action of tetramethyl ammonium hydroxide silicon alkoxide catalyst, and then dropwise adding methyl hydrosilyl fluorene, and grafting reaction of Si-H of the methyl hydrosilyl fluorene and 10-15% of vinyl groups on polymer side chains under the action of Karstedt catalyst.
  8. 8. The method for preparing high temperature resistant liquid silicone rubber according to claim 7, wherein the molar ratio of octamethyltetrasiloxane, tetramethyl tetravinyl cyclotetrasiloxane and methylphenyl cyclosiloxane is 8:0.44:1.
  9. 9. The method for preparing high temperature resistant liquid silicone rubber according to claim 4, wherein the addition chain extension reaction in step S1 is specifically that the phenylene hard segment-containing prepolymer and the side chain functionalized base polymer are mixed, the molar ratio of Si-H to Si-Vi in the system is controlled to be 1:1.3, the reaction is carried out at 100 ℃ until the viscosity of the system reaches 20000-80000 mPa.s, after the reaction is finished, the temperature is reduced to 70 ℃, and nitrogen is used for blowing for 60 minutes.
  10. 10. The method for preparing a high temperature resistant liquid silicone rubber according to claim 4, wherein the heat treatment in step S2 is carried out by kneading for 2 hours at a temperature of 150-160 ℃ and-0.09 MPa.

Description

High-temperature-resistant liquid silicone rubber and preparation method thereof Technical Field The invention belongs to the technical field of organic silicon high polymer materials, and particularly relates to high-temperature-resistant liquid silicone rubber and a preparation method thereof. Background Liquid Silicone Rubber (LSR) is widely applied to the fields of electronic appliances, automobiles, medical health and the like due to the characteristics of excellent fluidity, high molding speed, good biocompatibility and the like. However, conventional liquid silicone rubber is mainly composed of Polydimethylsiloxane (PDMS) segments, and although the siloxane bond of the main chain has higher bond energy, the main chain is easy to undergo a "back biting" reaction in a high-temperature airtight or semi-airtight environment at a temperature exceeding 250 ℃, so that the main chain is depolymerized to form cyclic siloxane small molecules, and the material is rapidly softened and degraded. Meanwhile, the methyl of the side chain is easy to be attacked by free radicals at high temperature to generate oxidation crosslinking, so that the material is hard and brittle. The prior patent CN113045901B discloses a preparation method of a secondary vulcanization-free addition type liquid silicone rubber, which is technically characterized in that the secondary vulcanization process is avoided by carrying out two-stage vacuum heat treatment on a base rubber and matching vinyl silicone oil with low volatile matters so as to reduce the volatile matters of the liquid silicone rubber. However, the core of the scheme is still aimed at the purification treatment of a conventional polydimethylsiloxane system, the main chain of the polymer molecule is still of a continuous silica bond structure, a rigid blocking unit is lacked, a side chain is not subjected to steric hindrance modification, the material hardening and brittleness caused by the back biting degradation of the main chain and the oxidation of the side chain still cannot be avoided in a high-temperature environment, and the use requirement under a high-temperature working condition is difficult to meet. Therefore, development of ultra-high temperature resistant silicone rubber which can block main chain degradation from the molecular structure, effectively shield side chain oxidation and maintain good liquid fluidity is a current problem to be solved. Disclosure of Invention The invention aims to solve the problems that the main chain of the existing liquid silicone rubber is easy to be bitten back and degraded and the side chain is easy to oxidize in a high-temperature environment, so that the material is embrittled and disabled. The specific technical scheme is as follows: The high temperature resistant liquid silicone rubber consists of 100 parts by weight of silafluorene-phenylene modified raw rubber, 20-50 parts by weight of reinforcing filler, 1-5 parts by weight of heat resistant agent, 1-10 parts by weight of cross-linking agent, 0.05-0.3 part by weight of catalyst and 0.02-0.1 part by weight of inhibitor, wherein a phenylene block is introduced into a main chain of the silafluorene-phenylene modified raw rubber polymer, and a silafluorene group is introduced into a side chain through hydrosilylation. Further, the phenylene block isThe silafluorene group is。 The reinforcing filler is gas-phase white carbon black subjected to surface hydrophobic treatment by using hexamethyldisilazane, octamethyl cyclotetrasiloxane or dimethyl dichlorosilane treatment agent, the heat-resistant agent is a dispersion system taking nano cerium dioxide solid particles as an effective component, the particle size is 10-50nm, the cross-linking agent is hydrogen-containing polymethylphenylhydrosiloxane, the hydrogen content is 0.5-1.2wt%, the catalyst is Karstedt catalyst, the platinum content is 2wt%, and the inhibitor is alkynol inhibitor, and specifically comprises 1-ethynyl-cyclohexanol, 2-methyl-3-butynyl-2-ol or 3, 5-dimethyl-1-ethynyl-3-ol. Further, the preparation method of the high-temperature-resistant liquid silicone rubber comprises the following steps: S1, respectively preparing a hard segment prepolymer containing phenylene and a side chain functionalized base polymer, and then carrying out addition chain extension reaction on the hard segment prepolymer containing phenylene and the side chain functionalized base polymer to obtain the silicon-containing fluorene-phenylene modified raw rubber; S2, mixing the silicon-containing fluorene-phenylene modified raw rubber with the reinforcing filler and the heat-resistant agent, performing heat treatment, cooling, adding the cross-linking agent, the catalyst and the inhibitor, and defoaming and filtering to obtain a finished product. The preparation method of the hard segment prepolymer containing the phenylene comprises the following steps of carrying out addition reaction on 1, 4-bis (dimethylvinylsilyl) benzene and a dihyd