A high elongation silicone rubber and its preparation method

Abstract

This application provides a high elongation silicone rubber and its preparation method. The high elongation silicone rubber comprises the following raw materials in parts by weight: 100 parts of terminal vinyldimethylsiloxane, 5-15 parts of modified filler, 2-10 parts of vinyl MQ resin, 3-8 parts of polymethylhydrosiloxane, 0.001-0.03 parts of methylbutyninol, and 0.001-0.003 parts of platinum catalyst. The modified filler includes a silane-modified microfibrillated cellulose-chitosan crosslinked composite and a polyvinyl alcohol-β-cyclodextrin complex supported in the silane-modified microfibrillated cellulose-chitosan crosslinked composite. The silicone rubber prepared by this application exhibits excellent elongation and is suitable for applications requiring high flexibility and tensile properties, such as flexible components and elastic packaging, showing broad application prospects.

Description

Technical Field

[0001] This application relates to the field of silicone rubber technology, specifically to a high elongation silicone rubber and its preparation method. Background Technology

[0002] Silicone rubber, as an elastomer material with excellent chemical stability, has been widely used in many fields such as shock absorption components, electronic packaging, and medical consumables. With the industrial upgrading of high-end manufacturing, the market for sealing components, flexible electronic components, and equipment packaging has put forward higher performance requirements for the elongation at break of silicone rubber.

[0003] Improving the elongation at break of traditional silicone rubber faces significant bottlenecks. Adding conventional inorganic fillers often leads to filler agglomeration and poor compatibility with the silicone rubber matrix, causing stress concentration within the material and limiting elongation. To address these issues, researchers have attempted to modify silicone rubber by introducing functional materials with special structures. Polyrotaxane (PR) offers a new direction for overcoming this bottleneck. Its cyclic slip units (such as cyclodextrin) can slide freely along linear axes, dispersing stress through intramolecular movement under stress, significantly improving the material's tensile toughness and deformation capacity. In existing technologies, researchers have discovered that introducing polyrotaxane-like or polyrotaxane materials with a "wheel-axle" structure, formed by passing polymer linear chains through cyclic units, into silicone rubber systems can trigger reversible slip and reconstruction behavior of cyclic molecules under external forces. This transforms localized stress concentration into dispersion along the molecular chain, effectively alleviating stress accumulation at crack tips. This type of structure can be macroscopically manifested as a significant increase in the elongation at break of the material, which helps to delay the transition of the material from the elastic stage to the fracture stage.

[0004] However, the above strategies typically involve the polyrotaxane structure directly participating in curing as part of the crosslinking network. While this design introduces a slip mechanism, it may result in the slip unit being constrained by the network curing while performing its function, potentially limiting the slip unit's own degree of freedom of movement and having a certain impact on the overall flexibility of the crosslinking network.

[0005] Therefore, how to significantly improve its elongation at break while retaining the advantages of stress dispersion remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] This application provides a high elongation silicone rubber and a method for preparing the same.

[0007] In a first aspect, this application provides a high elongation silicone rubber, characterized in that it comprises the following raw materials in parts by weight: 100 parts of terminal vinyl dimethylsiloxane, 5-15 parts of modified filler, 2-10 parts of vinyl MQ resin, 3-8 parts of polymethylhydrosiloxane, 0.001-0.03 parts of methylbutyninol, and 0.001-0.003 parts of platinum catalyst; wherein the modified filler comprises a silane-modified microfibrillated cellulose-chitosan crosslinked composite and a polyvinyl alcohol-β-cyclodextrin-based composite supported in the silane-modified microfibrillated cellulose-chitosan crosslinked composite.

[0008] According to this application, through the above-mentioned formulation design, while maintaining the original chemical stability and processing adaptability of silicone rubber, the stress buffering effect of the microfibrillated cellulose-chitosan crosslinked complex and the stress dissipation effect brought about by the slippage effect of the polyvinyl alcohol-β-cyclodextrin complex, which may have polyrotaxane-like characteristics, can form a synergistic stress regulation mechanism, which helps to improve the elongation at break of silicone rubber and meet the comprehensive performance requirements of silicone rubber in high-end applications.

[0009] Specifically, the molecular chains of microfibrillated cellulose (MFC) and chitosan (CS) are rich in polar groups such as hydroxyl and amino groups, which can cross-link through hydrogen bonds to form a three-dimensional network. This network has relatively continuous mesoporous channels, combining high elasticity and flexibility. Furthermore, the network formed by hydrogen bonding can undergo reversible elastic deformation under stress, and the mesoporous structure can provide sufficient space for deformation, reducing local stress concentration. In addition, MFC can serve as a "rigid support skeleton" for the cross-linked network, inhibiting irreversible collapse of the network during stretching, while the molecular chains of chitosan have good flexibility and can regulate the toughness of the network, so that the cross-linked complex can maintain structural integrity under large deformation, playing a "deformation buffer" role, and laying the structural foundation for stress dispersion of the subsequent polyvinyl alcohol-β-cyclodextrin complex. Furthermore, the polyvinyl alcohol-β-cyclodextrin complex is formed by the inclusion interaction of linear polyvinyl alcohol segments and cyclic β-cyclodextrin molecules. β-cyclodextrin possesses hydrophobic cavities, which can include acetate residues in the polyvinyl alcohol segments through hydrophobic interactions. This may allow the polyvinyl alcohol segments to penetrate into the cyclic cavities of the β-cyclodextrin, exhibiting a quasi-rotaxane structure with a "shaft-wheel" configuration. Polyvinyl alcohol can act as the linear axial chain, and β-cyclodextrin as the cyclic unit, with relative movement space between them. When the material is subjected to tensile stress, the cyclic unit may undergo moderate slippage along the linear axial chain, dispersing localized stress concentration through intramolecular movement and alleviating chain breakage caused by stress concentration. In addition, the microfibrillated cellulose-chitosan crosslinking network can serve as a component in the polyvinyl alcohol-β-cyclodextrin complex. The carrier of the polyvinyl alcohol-β-cyclodextrin complex confines it within the mesoporous channels of the cross-linked network, which can inhibit the intermolecular aggregation of the polyvinyl alcohol-β-cyclodextrin complex and promote its full contact with the carrier network and subsequent silicone rubber matrix, thus exerting a greater dynamic stress dispersion function. When the silicone rubber is stretched, the stress may first be transmitted to the microfibrillated cellulose-chitosan cross-linked complex, causing the cross-linked network to undergo elastic tensile deformation, which can initially buffer the stress. As the deformation increases, the polyvinyl alcohol-β-cyclodextrin complex may improve the transmission and dispersion of stress along the chain segments to a certain extent through relative slip, thereby helping to improve the deformation capacity of the material. The two work together to form a dual stress regulation mechanism of "buffering-dispersion", delaying the reaching of the critical chain segment extension state, thereby improving the elongation at break.

[0010] Furthermore, the high flexibility of the vinyl dimethylsiloxane (vinyl PDMS) matrix provides a basic elongation for the material. The mesoporous structure of the microfibrillated cellulose-chitosan crosslinked composite may facilitate the penetration of PDMS molecular chains into the mesopores, forming an interpenetrating structure between the matrix segments and the filler mesopores, enhancing interfacial bonding. Under stress, stress can be transferred more quickly from the matrix to the modified filler through the interface, improving the stress dispersion efficiency of the filler and reducing the possibility of early fracture due to interfacial peeling. In addition, the crosslinking points formed between vinyl MQ resin and vinyl PDMS may restrict the movement of PDMS chain segments. However, the possible slip characteristics of the polyvinyl alcohol-β-cyclodextrin complex in the modified filler and the elastic deformation of the microfibrillated cellulose-chitosan crosslinked composite can alleviate the constraint caused by the crosslinking points, allowing the PDMS chain segments to maintain a certain space for movement after reinforcement. On the other hand, the modified filler can also act as a flexible phase to compensate for the local modulus increase brought by MQ resin, thereby achieving a synergistic effect of reinforcement and elongation improvement, and optimizing the overall performance of silicone rubber.

[0011] In summary, silicone rubber can achieve good elongation at break by modifying the filler's own properties and synergistically interacting with multiple components in the raw material.

[0012] In some embodiments, the terminal vinyldimethylsiloxane comprises a first terminal vinyldimethylsiloxane and a second terminal vinyldimethylsiloxane, wherein the viscosity of the first terminal vinyldimethylsiloxane at 25°C is 10,000~30,000 mPa·s, and the viscosity of the second terminal vinyldimethylsiloxane at 25°C is 100~500 mPa·s, wherein the mass ratio of the first terminal vinyldimethylsiloxane to the second terminal vinyldimethylsiloxane is 1:0.4~0.5.

[0013] In some of the above embodiments, the first-terminated vinyl PDMS has a higher viscosity, typically with longer molecular chains and a higher degree of entanglement, which helps to form a more continuous interfacial phase, serving as the elastic skeleton of silicone rubber and preventing the molecular chains from easily slipping off during stretching. The second-terminated vinyl PDMS has a lower viscosity, typically with shorter molecular chains and better flowability, which can reduce the overall system viscosity, inhibit raw material agglomeration or uneven mixing, and the shorter molecular chains have a lower degree of entanglement, allowing them to fill the gaps between the long chains of the first PDMS. When the material is stretched, the short chains may slip, providing a certain buffer space for the extension or orientation of the long chains and enhancing the mobility of the molecular chains. When the mass ratio of the first-terminated vinyl dimethylsiloxane to the second-terminated vinyl dimethylsiloxane is 1:0.4~0.5, the first-terminated vinyl PDMS can provide sufficient support, while the second-terminated vinyl PDMS can optimize processing and stretchability, achieving a performance balance between high elongation and high tensile strength. In addition, both have the same terminal vinyl chemical structure, and the crosslinked network formed has high uniformity, which can alleviate phase separation or weak interface problems.

[0014] In some embodiments, the polyvinyl alcohol-β-cyclodextrin-based complex is obtained by modifying polyvinyl alcohol-β-cyclodextrin with isocyanate, wherein the isocyanate includes isophorone diisocyanate.

[0015] In some of the above embodiments, the modification of polyvinyl alcohol-β-cyclodextrin with isocyanate can improve the overall structural integrity and processing stability of the composite by introducing chemical bonds. Isophorone diisocyanate (IPDI) is an alicyclic diisocyanate with mild reactivity and moderate steric hindrance. Covalent bonding may inhibit the slippage of β-cyclodextrin from the polyvinyl alcohol segments, reducing the possibility of inclusion structure disintegration. Due to the alicyclic steric hindrance effect of IPDI, it may stabilize the structure of the polyvinyl alcohol segments while inhibiting excessive crosslinking, allowing the polyvinyl alcohol-β-cyclodextrin-based composite to maintain a certain degree of slip mobility. Furthermore, the formed carbamate bonds have both good flexibility and hydrolysis resistance, which is beneficial to improving the dispersibility and compatibility of the modified filler. The modified polyvinyl alcohol-β-cyclodextrin-based composite exhibits better structural retention during subsequent high-temperature mixing and vulcanization with the silicone rubber matrix. The functional units are less prone to failure due to heat or shear. The dispersion and interfacial bonding in the silicone rubber and the loaded crosslinked network are improved, which is beneficial for more effective stress transfer between the filler and the matrix.

[0016] In some embodiments, the polyvinyl alcohol-β-cyclodextrin complex is prepared by the following steps:

[0017] S1: Polyvinyl alcohol and β-cyclodextrin with a degree of alcoholysis of 75%~85% are dispersed in water, and β-cyclodextrin is incorporated into the un-hydrolyzed acetate units of polyvinyl alcohol through intermolecular hydrogen bonds and hydrophobic cavities to obtain polyvinyl alcohol-β-cyclodextrin.

[0018] S2: Polyvinyl alcohol-β-cyclodextrin and isophorone diisocyanate are dispersed in N,N-dimethylformamide, and the isocyanate groups of isophorone diisocyanate undergo a carbamate reaction with the hydroxyl groups to obtain a polyvinyl alcohol-β-cyclodextrin complex.

[0019] In some of the above embodiments, the degree of hydrolysis of the polyvinyl alcohol is 75-85%. An appropriate degree of hydrolysis can reduce intramolecular or intermolecular hydrogen bond entanglement of PVA molecules, allowing the axial chains to stretch and facilitating the penetration of β-cyclodextrin. β-cyclodextrin may form a partially "embedded" structure with the PVA chain through the hydrophobic matching effect between the hydrophobic cavity and the hydrophobic segment of polyvinyl alcohol; subsequently, the alicyclic structure of IPDI is introduced through a urethane ester reaction, further enhancing the inclusion stability of β-cyclodextrin.

[0020] In some embodiments, the polyvinyl alcohol-β-cyclodextrin complex is prepared by the following steps:

[0021] S1: Disperse 10 parts of polyvinyl alcohol with a degree of alcoholysis of 75%~85% and 7~10 parts of β-cyclodextrin in 50~100 parts of water, and react at 10~50℃ for 5~15h to obtain polyvinyl alcohol-β-cyclodextrin.

[0022] S2: 10 parts of polyvinyl alcohol-β-cyclodextrin, 14-20 parts of isophorone diisocyanate, and 0.001-0.02 parts of dibutyltin dilaurate are dispersed in 10-100 parts of N,N-dimethylformamide and reacted at 10-50℃ for 6-12 h to obtain polyvinyl alcohol-β-cyclodextrin complex.

[0023] In some of the above embodiments, a method for preparing polyvinyl alcohol-β-cyclodextrin complex is specifically described. By using appropriate solvents and reaction conditions, the polyvinyl alcohol-β-cyclodextrin complex can have a relatively stable inclusion structure, laying a structural foundation for its stress regulation function in silicone rubber matrix.

[0024] In some embodiments, the modified filler is prepared by the following steps:

[0025] N1: Microfibrillated cellulose, chitosan, lithium bromide, and polyvinyl alcohol-β-cyclodextrin complex are dispersed in water to form a cross-linked network of microfibrillated cellulose and chitosan and load the polyvinyl alcohol-β-cyclodextrin complex, thus obtaining a microfibrillated cellulose-chitosan cross-linked complex loaded with the polyvinyl alcohol-β-cyclodextrin complex.

[0026] N2: The microfibrillated cellulose-chitosan crosslinked complex loaded with polyvinyl alcohol-β-cyclodextrin group complex and methyltrimethoxysilane are dispersed in ethanol to introduce hydrophobic groups on the surface of the microfibrillated cellulose-chitosan crosslinked complex, thus obtaining the modified filler.

[0027] In some of the above embodiments, MFC is rich in hydroxyl groups, and CS molecular chains contain hydroxyl and amino groups. In aqueous solution, the two are fully dispersed by the hydrogen bond breaking and solubilizing effect of lithium bromide. Intermolecular hydrogen bonds can be formed between the exposed polar groups of MFC and CS to construct a three-dimensional cross-linked network. As water evaporates, the probability of hydrogen bond binding between polar groups increases, and the hydrogen bond cross-linking density is further improved. The network gradually solidifies and forms a structurally stable cross-linked network matrix. The mesoporous channels formed during the solidification process can provide confined loading space for the polyvinyl alcohol-β-cyclodextrin complex. The hydroxyl groups in the polyvinyl alcohol-β-cyclodextrin complex molecules can form weak hydrogen bonds with the hydroxyl and amino groups in the cross-linked network. At the same time, due to the physical confinement effect of the mesoporous structure, the complex can be stably loaded in the mesopores, ultimately forming a modified filler composite structure.

[0028] In step N2, the silanol generated by the hydrolysis of methyltrimethoxysilane (MTMS) can undergo a condensation reaction with the hydroxyl groups on the surface of the modified filler to form a methyl-containing siloxane interface on its surface. This can reduce the polarity of the modified filler surface, improve the compatibility and interfacial bonding force between the filler and the matrix, and inhibit the shear failure of the modified filler during the mixing process.

[0029] In some embodiments, the modified filler is prepared by the following steps:

[0030] N1: Disperse 2-4 parts of microfibrillated cellulose, 0.5-2 parts of chitosan, 10-50 parts of lithium bromide, and 1 part of polyvinyl alcohol-β-cyclodextrin complex in 10-100 parts of water at 20-60°C, and react at 10-50°C for 24-96 h to obtain a microfibrillated cellulose-chitosan crosslinked complex loaded with polyvinyl alcohol-β-cyclodextrin complex;

[0031] N2: 10 parts of microfibrillated cellulose-chitosan crosslinked complex loaded with polyvinyl alcohol-β-cyclodextrin complex, 1-10 parts of methyltrimethoxysilane, and 0.01-0.1 parts of formic acid are dispersed in 10-50 parts of ethanol and reacted at 40-80℃ for 2-8 hours to obtain the modified filler.

[0032] In some of the above embodiments, a method for preparing modified fillers is specifically described. By using appropriate solvents and reaction conditions, stable cross-linking of microfibrillated cellulose-chitosan and loading of polyvinyl alcohol-β-cyclodextrin complex can be achieved to perform surface hydrophobic modification, which can ensure the dispersibility and shear stability of the filler in the silicone rubber system and help to promote the efficient stress buffering effect.

[0033] In some embodiments, the vinyl content of the first-terminated vinyldimethylsiloxane is 0.05wt% to 0.5wt%. Based on the above embodiments, an appropriate vinyl content can form an appropriate number of crosslinking points, suppressing material embrittlement caused by excessive crosslinking.

[0034] In some embodiments, the vinyl content of the second-terminated vinyldimethylsiloxane is 1 wt% to 2 wt%. Based on the above embodiments, a slightly higher vinyl content can form more crosslinking points, thereby compensating for the potential local network looseness or strength loss due to its shorter molecular chain and lower viscosity, and ensuring that the overall crosslinking density of the system is within a reasonable range.

[0035] In some embodiments, the vinyl MQ resin has a viscosity of 5000~15000 mPa·s at 25°C, an M / Q value of 0.7~0.9, and a vinyl content of 0.5wt%~2wt%. Based on the above embodiments, this viscosity range ensures good dispersibility and moderate reinforcement of the vinyl MQ resin without significantly increasing the system modulus. An M / Q value in the range of 0.7~0.9 balances rigid support and flexible segments. An appropriate vinyl content can form a relatively uniform network and suppress interfacial delamination during stretching.

[0036] In some embodiments, the polymethylhydrosiloxane has a viscosity of 0.01~0.1 Pa·s at 25°C and a hydrogen content of 0.1wt%~1wt%. Based on the above embodiments, polymethylhydrosiloxane within this range of conditions can be well dispersed in the matrix, which helps to form a crosslinked network of suitable density and balance high elongation and mechanical stability.

[0037] In some embodiments, the platinum catalyst includes a Karstedt catalyst. Based on the above embodiments, the Karstedt catalyst can achieve the addition crosslinking reaction between terminal vinyldimethylsiloxane and polymethylhydrosiloxane at a lower temperature, enabling the silicone rubber system to form a uniform and controllable crosslinking network, reducing the probability of side reactions, and thus improving the elongation at break and overall mechanical properties of the material.

[0038] In some embodiments, methylbutyninol in the raw materials can act as an inhibitor of hydrosilylation reaction, which can inhibit the activity of platinum catalyst at low temperatures, reduce premature crosslinking of rubber compounds, and fail at high temperatures without affecting the reaction, thus ensuring the process stability of silicone rubber vulcanization.

[0039] Secondly, this application provides a method for preparing high elongation silicone rubber, comprising:

[0040] Provide raw materials for the silicone rubber according to any embodiment of the first aspect;

[0041] The raw materials are mixed and cured to obtain high elongation silicone rubber.

[0042] According to this application, the silicone rubber of the first aspect can be prepared by using the raw material of the silicone rubber described in any embodiment of the first aspect, and thus has the beneficial effects of the first aspect, and the obtained silicone rubber has excellent elongation at break.

[0043] In some embodiments, the method includes:

[0044] The terminal vinyl dimethylsiloxane, modified filler, and vinyl MQ resin are mixed at 30~90℃ for 10~20 min, and then dried at 80~100℃ for 1~2 h to obtain the masterbatch.

[0045] After the masterbatch is cooled, polymethylhydrosiloxane, methylbutynol and platinum catalyst are added. After mixing, the mixture is molded and vulcanized at 80~110℃ for 15~30min. After vulcanization, it is post-cured at 110~130℃ for 2~4h to obtain high elongation silicone rubber.

[0046] In some of the above embodiments, mixing the terminal vinyl dimethylsiloxane, modified filler, and vinyl MQ resin at 30-90°C can improve the uniformity of filler dispersion in the system. The vinyl MQ resin is distributed between PDMS segments, laying the foundation for the formation of a more uniform reinforcing network during subsequent curing. Drying the compound at 80-100°C can remove residual low-boiling substances in the system and inhibit the activity of platinum catalysts during the crosslinking reaction, reducing problems such as early reaction runaway or uneven crosslinking. Polymethylhydrosiloxane is added after the masterbatch cools. Alkane, methylbutyninol, and platinum catalyst are used for compression molding and vulcanization at 80-110°C. Under the catalysis of the platinum catalyst, polymethylhydrosiloxane provides Si-H groups, which act as crosslinking agents and undergo addition reactions with terminal vinyl PDMS to construct a main three-dimensional crosslinked network. At the same time, vinyl MQ resin participates in local reinforcement around the crosslinking points. Finally, post-curing is carried out at 110-130°C to further promote the reaction of the remaining Si-H groups in the system with vinyl groups, improve the integrity and thermal stability of the crosslinked network, and form a silicone rubber material with high elongation at break.

[0047] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0048] The modified filler designed in this application, through the synergistic effect of a mesoporous cross-linked network constructed from microfibrillated cellulose and chitosan and a polyvinyl alcohol-β-cyclodextrin complex with certain slip characteristics, can provide energy buffering and dispersion during stretching, effectively delaying stress concentration and thus improving the elongation at break of silicone rubber. Simultaneously, the silane-modified filler maintains good compatibility in the vinyl-terminated PDMS and vinyl MQ resin matrix, making stress transmission more uniform and further enhancing the overall deformation capacity. Therefore, this application achieves silicone rubber with a higher elongation than existing technologies while maintaining the processing performance of silicone rubber. Detailed Implementation

[0049] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0050] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0052] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0053] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0054] First-terminal vinyl dimethylsiloxane: viscosity at 25°C is 10000 mPa·s, vinyl content is 0.36 wt%;

[0055] Second-terminated vinyl dimethylsiloxane: viscosity at 25°C is 500 mPa·s, vinyl content is 1.1 wt%;

[0056] First polyvinyl alcohol: CAS number 9002-89-5, viscosity at 25℃ is 45 mPa·s, degree of alcoholysis is 78.5%;

[0057] Second polyvinyl alcohol: CAS number 9002-89-5, viscosity at 25℃ is 54 mPa·s, degree of alcoholysis is 99%;

[0058] β-Cyclodextrin: CAS number 7585-39-9;

[0059] Isophorone diisocyanate: CAS number 4098-71-9;

[0060] Dibutyltin dilaurate: CAS number 77-58-7;

[0061] Methyltrimethoxysilane: CAS No. 1185-55-3;

[0062] Microfibrillated cellulose: The average fiber diameter is approximately 500 nm, and the average length is approximately 50 μm;

[0063] Chitosan: CAS number 9012-76-4, weight average molecular weight approximately 500,000;

[0064] Vinyl MQ resin: viscosity at 25°C is 9000 mPa·s, M / Q ratio is 0.8, vinyl content is 1.5 wt%;

[0065] Polymethylhydrosiloxane: viscosity at 25°C is 0.05 Pa·s, hydrogen content is 0.5 wt%;

[0066] Methylbutynol: CAS number 115-19-5.

[0067] Preparation Example 1

[0068] Preparation of polyvinyl alcohol-β-cyclodextrin complex:

[0069] S1: 10 parts of first polyvinyl alcohol and 8.5 parts of β-cyclodextrin were dispersed in 80 parts of deionized water and reacted at 25°C for 10 h. After centrifugation, washing and vacuum drying, polyvinyl alcohol-β-cyclodextrin was obtained.

[0070] S2: 10 parts of polyvinyl alcohol-β-cyclodextrin and 16.5 parts of isophorone diisocyanate were dispersed in 50 parts of anhydrous N,N-dimethylformamide, and 0.008 parts of dibutyltin dilaurate were added. The mixture was reacted at 25°C for 8 hours, and then centrifuged, washed, and vacuum dried to obtain polyvinyl alcohol-β-cyclodextrin complex A.

[0071] Preparation Example 2

[0072] Preparation of polyvinyl alcohol-β-cyclodextrin complex:

[0073] The preparation method is largely the same as in Example 1, except that the first polyvinyl alcohol in step S1 is replaced with the second polyvinyl alcohol. Step S2 is the same, resulting in polyvinyl alcohol-β-cyclodextrin complex B.

[0074] Preparation Example 3

[0075] Preparation of polyvinyl alcohol-β-cyclodextrin:

[0076] S1: Disperse 10 parts of first polyvinyl alcohol and 8.5 parts of β-cyclodextrin in 60 parts of deionized water, stir at 25°C for 10 h, centrifuge, wash, and vacuum dry to obtain polyvinyl alcohol-β-cyclodextrin C.

[0077] Preparation Example 4

[0078] Preparation of modified fillers:

[0079] N1: Disperse 1 part of polyvinyl alcohol-β-cyclodextrin complex A in 10 parts of deionized water and stir for 10 min to form a polyvinyl alcohol-β-cyclodextrin complex dispersion for later use.

[0080] N2: Disperse 15 parts of lithium bromide in 10 parts of deionized water, stir for 20 min, add 3 parts of microfibrillated cellulose and 1 part of chitosan, stir at 50℃ for 30 min, then add the polyvinyl alcohol-β-cyclodextrin complex dispersion prepared in N1, stir at 30℃ for 20 min to obtain the precursor solution.

[0081] N3: Pour the precursor solution into a petri dish, add 50 parts of 50℃ deionized water, let stand for 48h, wash and freeze dry to obtain the modified filler without hydrophobic treatment;

[0082] N4: 10 parts of unhydrophobic modified filler and 0.05 parts of formic acid were dispersed in 30 parts of anhydrous ethanol, and 3.5 parts of methyltrimethoxysilane were added. The mixture was reacted at 60°C for 5 hours, centrifuged, washed, and freeze-dried to obtain modified filler A.

[0083] Preparation Example 5

[0084] Preparation of modified fillers:

[0085] The preparation method is largely the same as in Example 4, except that the polyvinyl alcohol-β-cyclodextrin complex A in step N1 is replaced with polyvinyl alcohol-β-cyclodextrin complex B. Steps N1 to N3 are the same, resulting in modified filler B.

[0086] Preparation Example 6

[0087] Preparation of modified fillers:

[0088] The preparation method is largely the same as in Example 4, except that the polyvinyl alcohol-β-cyclodextrin complex A in step N1 is replaced with polyvinyl alcohol-β-cyclodextrin C. Steps N1 to N3 are the same, and the modified filler C is obtained.

[0089] Preparation Example 7

[0090] Preparation of modified fillers:

[0091] The preparation method is largely the same as in Example 4, except that the silane modification in step N4 was not performed. Steps N1 to N3 are the same, resulting in modified filler D.

[0092] Comparative Preparation Example 1

[0093] Preparation of microfibrillated cellulose-chitosan crosslinked complex:

[0094] N1: Disperse 15 parts of lithium bromide in 10 parts of deionized water, stir for 20 min, add 3 parts of microfibrillated cellulose and 1 part of chitosan, stir at 50℃ for 30 min to obtain the precursor solution;

[0095] N2: Pour the precursor solution into a petri dish, add 50 parts of deionized water at 50℃, let stand for 48 hours, wash, and freeze dry to obtain the microfibrillated cellulose-chitosan crosslinked complex.

[0096] Example 1

[0097] Preparation of high elongation silicone rubber:

[0098] M1: Place 30 parts of second-terminal vinyl dimethylsiloxane and 10 parts of modified filler A in a mixer and mix at 40°C for 5 minutes. Then add 70 parts of first-terminal vinyl dimethylsiloxane and 8 parts of vinyl MQ resin and heat to 85°C to mix for 15 minutes. After mixing, dry at 90°C for 2 hours to obtain the masterbatch.

[0099] M2: Place the cooled masterbatch in a mixer, add 6 parts of polymethylhydrosiloxane and 0.008 parts of methylbutyninol, mix at 50°C for 1 min, then add 0.002 parts of Karstedt catalyst, mix at 50°C for 1 min, then mold at 100°C using a flat vulcanizing machine at a pressure of 15 MPa for 20 min, and finally cure at 120°C for 3 h to obtain high elongation silicone rubber.

[0100] Example 2

[0101] Preparation of high elongation silicone rubber:

[0102] Similar to Example 1, the only difference is the mass ratio of the first-terminal vinyldimethylsiloxane and the second-terminal vinyldimethylsiloxane used in step M1. Specifically, the difference is as follows:

[0103] M1: Place 10 parts of second-terminal vinyl dimethylsiloxane and 10 parts of modified filler in a mixer and mix at 40°C for 5 minutes. Then add 90 parts of first-terminal vinyl dimethylsiloxane and 5 parts of vinyl MQ resin and heat to 85°C to mix for 15 minutes. After mixing, dry at 90°C for 2 hours to obtain the masterbatch.

[0104] Example 3

[0105] Preparation of high elongation silicone rubber:

[0106] Similar to Example 1, the only difference is the mass ratio of the first-terminal vinyldimethylsiloxane and the second-terminal vinyldimethylsiloxane used in step M1. Specifically, the difference is as follows:

[0107] M1: Place 50 parts of second-terminal vinyl dimethylsiloxane and 10 parts of modified filler in a mixer and mix at 40°C for 5 minutes. Then add 50 parts of first-terminal vinyl dimethylsiloxane and 5 parts of vinyl MQ resin and heat to 85°C to mix for 15 minutes. After mixing, dry at 90°C for 2 hours to obtain the masterbatch.

[0108] Example 4

[0109] Preparation of high elongation silicone rubber:

[0110] It is largely the same as Example 1, except that the modified filler A in step M1 is replaced with modified filler B.

[0111] Example 5

[0112] Preparation of high elongation silicone rubber:

[0113] It is largely the same as Example 1, except that the modified filler A in step M1 is replaced with modified filler C.

[0114] Comparative Example 1

[0115] Preparation of high elongation silicone rubber:

[0116] Similar to Example 1, except that in step M1, the modified filler A is replaced with polyvinyl alcohol-β-cyclodextrin complex A.

[0117] Comparative Example 2

[0118] Preparation of high elongation silicone rubber:

[0119] Similar to Example 1, except that the modified filler A in step M1 was replaced with the microfibrillated cellulose-chitosan crosslinked complex obtained in Comparative Preparation Example 1.

[0120] Comparative Example 3

[0121] Preparation of high elongation silicone rubber:

[0122] It is largely the same as Example 1, except that the modified filler A in step M1 is replaced with modified filler D.

[0123] Test section

[0124] The high elongation silicone rubbers prepared in the examples and comparative examples were subjected to performance tests. The high elongation silicone rubbers were cut into dumbbell-shaped specimens with a length of 40 mm, a test length of 10 mm, and a thickness of 2 mm.

[0125] Tensile strength test: Refer to the national standard GB / T 528-2009, and test the tensile strength TS0 (MPa) of the specimen at a tensile rate of 200 mm / min.

[0126] Elongation at break test: Referring to national standard GB / T 528-2009, the elongation at break E of the specimen was tested at a tensile rate of 200 mm / min. b (%).

[0127] The average value of the 5 test results is shown in Table 1.

[0128] Table 1

[0129]

[0130] As shown in Table 1, the silicone rubbers obtained in each embodiment have better elongation at break than those in the comparative examples. This may be because, in Comparative Example 1, the lack of a microfibrillated cellulose-chitosan crosslinked composite network restricts the polyvinyl alcohol-β-cyclodextrin complex, which is prone to aggregation, leading to a reduction in the number of chain segments involved in stress dispersion. Furthermore, the interface between the aggregated polyvinyl alcohol-β-cyclodextrin complex and the matrix may contain pores, which can easily lead to stress concentration during stretching, resulting in a decrease in elongation. In Comparative Example 2, the filler is only a microfibrillated cellulose-chitosan crosslinked composite. When the tensile stress exceeds the elastic limit of the microfibrillated cellulose-chitosan crosslinked composite, the hydrogen bonds will break irreversibly, causing the network structure to collapse and making it impossible to redistribute stress. In Comparative Example 3, the modified filler has not undergone silane modification treatment, which may lead to a decrease in its interfacial compatibility, dispersibility, and stress transfer efficiency with the silicone rubber matrix, resulting in deterioration of tensile properties.

[0131] As can be seen from Examples 1-3, the mass ratio of the first-terminal vinyldimethylsiloxane to the second-terminal vinyldimethylsiloxane has a certain influence on the elongation of silicone rubber. When the mass ratio of the first-terminal vinyldimethylsiloxane to the second-terminal vinyldimethylsiloxane is 1:0.4-0.5, the elongation of silicone rubber is higher.

[0132] As can be seen from Examples 1 and 4, the preparation process of the modified filler has a certain impact on the elongation of silicone rubber. When the modified filler is hydrophobically treated, the elongation of silicone rubber is higher.

[0133] As can be seen from Examples 1 and 5, the degree of hydrolysis of polyvinyl alcohol has a certain influence on the elongation of silicone rubber. When the degree of hydrolysis of polyvinyl alcohol is 75%~85%, the elongation of silicone rubber is higher.

[0134] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A high elongation silicone rubber, characterized in that, Includes the following quantities of raw materials: 100 parts vinyl-terminated polydimethylsiloxane, 5-15 parts modified filler, 2-10 parts vinyl MQ resin, 3-8 parts polymethylhydrosiloxane, 0.001-0.03 parts methylbutynol, 0.001-0.003 parts platinum catalyst; The modified filler includes a silane-modified microfibrillated cellulose-chitosan crosslinked composite and a polyvinyl alcohol-β-cyclodextrin-based composite loaded in the silane-modified microfibrillated cellulose-chitosan crosslinked composite. The polyvinyl alcohol-β-cyclodextrin complex was prepared by the following steps: S1: Polyvinyl alcohol and β-cyclodextrin with a degree of alcoholysis of 75%~85% are dispersed in water, and β-cyclodextrin is incorporated into the un-hydrolyzed acetate units of polyvinyl alcohol through intermolecular hydrogen bonds and hydrophobic cavities to obtain polyvinyl alcohol-β-cyclodextrin. S2: Polyvinyl alcohol-β-cyclodextrin and isophorone diisocyanate are dispersed in N,N-dimethylformamide, and the isocyanate groups of isophorone diisocyanate undergo a carbamate reaction with the hydroxyl groups to obtain a polyvinyl alcohol-β-cyclodextrin complex. The modified filler is prepared by the following steps: N1: Microfibrillated cellulose, chitosan, lithium bromide, and polyvinyl alcohol-β-cyclodextrin complex are dispersed in water to form a cross-linked network of microfibrillated cellulose and chitosan and load the polyvinyl alcohol-β-cyclodextrin complex, thus obtaining a microfibrillated cellulose-chitosan cross-linked complex loaded with the polyvinyl alcohol-β-cyclodextrin complex. N2: The microfibrillated cellulose-chitosan crosslinked complex loaded with polyvinyl alcohol-β-cyclodextrin group complex and methyltrimethoxysilane are dispersed in ethanol to introduce hydrophobic groups on the surface of the microfibrillated cellulose-chitosan crosslinked complex, thus obtaining the modified filler.

2. The silicone rubber according to claim 1, characterized in that, The terminated vinyl polydimethylsiloxane comprises a first terminated vinyl polydimethylsiloxane and a second terminated vinyl polydimethylsiloxane. The viscosity of the first terminated vinyl polydimethylsiloxane at 25°C is 10,000~30,000 mPa·s, and the viscosity of the second terminated vinyl polydimethylsiloxane at 25°C is 100~500 mPa·s. The mass ratio of the first terminated vinyl polydimethylsiloxane to the second terminated vinyl polydimethylsiloxane is 1:0.4~0.

5.

3. The silicone rubber according to claim 1, characterized in that, The polyvinyl alcohol-β-cyclodextrin complex was prepared by the following steps: S1: Disperse 10 parts of polyvinyl alcohol with a degree of alcoholysis of 75%~85% and 7~10 parts of β-cyclodextrin in 50~100 parts of water, and react at 10~50℃ for 5~15h to obtain polyvinyl alcohol-β-cyclodextrin. S2: 10 parts of polyvinyl alcohol-β-cyclodextrin, 14-20 parts of isophorone diisocyanate, and 0.001-0.02 parts of dibutyltin dilaurate are dispersed in 10-100 parts of N,N-dimethylformamide and reacted at 10-50℃ for 6-12 h to obtain polyvinyl alcohol-β-cyclodextrin complex.

4. The silicone rubber according to claim 1, characterized in that, The modified filler is prepared by the following steps: N1: Disperse 2-4 parts of microfibrillated cellulose, 0.5-2 parts of chitosan, 10-50 parts of lithium bromide, and 1 part of polyvinyl alcohol-β-cyclodextrin complex in 10-100 parts of water at 20-60°C, and react at 10-50°C for 24-96 h to obtain a microfibrillated cellulose-chitosan crosslinked complex loaded with polyvinyl alcohol-β-cyclodextrin complex; N2: 10 parts of microfibrillated cellulose-chitosan crosslinked complex loaded with polyvinyl alcohol-β-cyclodextrin complex, 1-10 parts of methyltrimethoxysilane, and 0.01-0.1 parts of formic acid are dispersed in 10-50 parts of ethanol and reacted at 40-80℃ for 2-8 hours to obtain the modified filler.

5. The silicone rubber according to claim 2, characterized in that, The silicone rubber satisfies at least one of the following conditions: 1) The vinyl content of the first-terminated vinyl polydimethylsiloxane is 0.05wt%~0.5wt%; 2) The vinyl content of the second-terminated vinyl polydimethylsiloxane is 1wt%~2wt%; 3) The vinyl MQ resin has a viscosity of 5000~15000 mPa·s at 25°C, an M / Q value of 0.7~0.9, and a vinyl content of 0.5wt%~2wt%. 4) The polymethylhydrosiloxane has a viscosity of 0.01~0.1 Pa·s at 25°C and a hydrogen content of 0.1wt%~1wt%. 5) The platinum catalyst includes the Karstedt catalyst.

6. A method for preparing high elongation silicone rubber, characterized in that, include: Provide raw materials for the silicone rubber according to any one of claims 1 to 5; The raw materials are mixed and cured to obtain high elongation silicone rubber.

7. The method according to claim 6, characterized in that, include: Vinyl-terminated polydimethylsiloxane, modified filler, and vinyl MQ resin are mixed at 30-90℃ for 10-20 min, and then dried at 80-100℃ for 1-2 h to obtain masterbatch. After the masterbatch is cooled, polymethylhydrosiloxane, methylbutynol and platinum catalyst are added. After mixing, the mixture is molded and vulcanized at 80~110℃ for 15~30min. After vulcanization, it is post-cured at 110~130℃ for 2~4h to obtain high elongation silicone rubber.

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