Preparation and properties of heat-curable silicone rubber through chloropropyl/amine crosslinking reactions

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Multiamino‐terminated telechelic polydimethylsiloxane (MATTPS) was synthesized via aza‐Micheal reaction and amidation reaction and subsequently employed as cross‐linkers of polysiloxane containing γ‐chloropropyl groups (CPPS) for preparing a series of high‐temperature vulcanized silicone rubber (MCSR/MATTPS). The curing, mechanical, and thermal properties of MCSR/MATTPS were studied through rheometry, mechanical testing, and thermogravimetric analysis (TGA). MCSR/MATTPS exhibits optimal mechanical properties with a tensile strength of 9.52 MPa and tear strength of 45.4 kN/m when the molar ratio of [N–H]/[CH2CH2CH2Cl] is of 1, which is attributed to the formation of concentrative cross‐linking in the three‐dimensional polymer networks. The thermal behaviors of MCSR/MATTPS display a two‐step weight loss process by heating in nitrogen whereas more than two weight loss process in air. TGA results indicate that the introduction of aliphatic long chain and carbonyl groups in the structure of MATTPS has little negative effect on the thermal stability of MCSR/MATTPS.

Section: Resultssupporting

confidence: 90%

Section: Cross-linking Mechanism Of Mcsr/mattpssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Applications of α, ω‐telechelic polydimethylsiloxane as cross‐linkers for preparing high‐temperature vulcanized silicone rubber

Dong

Wang

et al. 2019

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“…Organotin catalysts in the functional group condensation vulcanization system have higher toxicity and are limited in some fields. Therefore, novel cross‐linking methods have been proposed over the years, such as the reaction of amino group with epoxide/chlorinated hydrocarbon, the click chemistry, the UV‐curing, and the oxa‐Michael reaction . It is worth noting that the thermocyclization of TFVE has the advantages of simple reaction conditions, no catalyst and no by‐products.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of polysiloxanes containing trifluoroethylene aryl ether groups: The effect of promoters

Yuan

Diao

Zhao

et al. 2020

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Polysiloxanes with high molecular weight (M n > 100 000, M w /M n < 2.2) containing various quantity of trifluoroethylene aryl ether groups were prepared by anion ring opening polymerization (AROP) in the presence of promoters including N,Ndimethylformamide (DMF) and N-methyl pyrrolidone (NMP). The structures of monomers and polymers were characterized by FTIR and NMR. It was found that the addition of promoter could significantly increase the polymerization rate, decrease the polymerization temperature, and increase the molecular weight of the polymer.When DMF as the promoter, the optimal conditions for polymerization were as follows: The polymerization temperature is 100 C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 160:1. The optimal conditions for polymerization using NMP as the promoter were as follows: The polymerization temperature is 75 C, the amount of catalyst is 2.0%, and the molar ratio of promoter to catalyst is 70:1, which indicated that NMP is more effective on AROP than DMF. Thermogravimetric analysis (TGA) showed that the polymer has good heat temperature resistance. Differential scanning calorimetry (DSC) showed that the introduction of NMP in bulk polymerization could improve the randomness of polymer structure, which leads to the disappearance of crystal peak and improve the low temperature resistance of polymer. K E Y W O R D S alkali catalytic system, anion ring opening polymerization, polysiloxane, promoter, trifluorovinyl aryl ether group 1 | INTRODUCTION Perfluorocyclobutyl (PFCB) polymer is a novel class of semifluorinated polymers first reported by Babb et al 1 in 1993. PFCB polymers are mainly prepared by the [2π + 2π] thermocyclization of trifluoroethylene aryl ether (TFVE) monomer. 2 Recently, PFCB polymers have attracted extensive attention of researchers in various fields including electronics industry, 3-7 aerospace, 8 fuel cells, 9-13 optical waveguide materials, 14-16 and coatings 17 because of the unique properties such as low dielectric property, low hygroscopicity, high thermal stability, chemical solvent resistance, and low birefringence. However, most of the research interests are focused on the functionality of PFCB group. There are few researches about the thermocyclization of TFVE monomer.Silicone rubber is one of the largest and most widely used organosilicon products. The traditional vulcanization methods of silicone rubber mainly include the following three categories: peroxide vulcanization, hydrosiloxane vulcanization, and functional group condensation vulcanization. Peroxide vulcanization is described that vinyl polysiloxane is cured by radical reaction using peroxides as the initiators to form a cross-linked network. However, the residues of peroxide decomposition have negative effects on the properties of silicone

Preparation and characterization of silicone rubber through the reaction between γ‐chloropropyl and amino groups with siloxane polyamidoamine dendrimers as cross‐linkers

Dong

Feng

et al. 2017

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A novel heat-curable silicone rubber (MCSR/Si-PAMAM) was prepared by using siloxane polyamidoamine (Si-PAMAM) dendrimers as cross-linkers and polysiloxane containing γchloropropyl groups as gums. The chemical cross-linking occurs through the reaction between Si-PAMAM dendrimers and polysiloxane containing γ-chloropropyl groups. The effect of various amounts of cross-linkers on mechanical properties of MCSR/Si-PAMAM was discussed in this paper. MCSR/Si-PAMAM exhibits favorable mechanical properties with a tensile strength of 10.06 MPa and a tear strength of 47.9 kN/m when the molar ratio r of [N-H]/[CH 2 CH 2 CH 2 Cl] is 1:1. These excellent mechanical properties can be attributed to the formation of concentrative cross-linking from Si-PAMAM dendrimers in the cross-linking networks, along with the introduction of Si-O-Si units in the internal structure of dendrimers. The introduction of Si-O-Si unitsreduces the steric hindrance of molecular structure, which facilitates the N-H bonds in the interior layers of dendrimers to react with γ-chloropropyl groups. In addition, thermogravimetric analysis results indicate that MCSR/Si-PAMAM is thermally stable even at high temperatures in a nitrogen atmosphere. Differential scanning calorimetry analysis reveals that the glass transition peak of MCSR/Si-PAMAM is not identified in the temperature range −150 to −30°C, only a melting endothermic peak at −40°C.