Silicone rubber is a kind of product with large output and wide application in organosilicon products. Silicone rubber vulcanized with excellent resistance to high, low temperature, weather, hydrophobia, electrical insulation, physiological inertia and other characteristics, has been widely used in national defense, military, medical and health, industrial and agricultural production and people's daily life. In this paper, the main characteristics and future development of silicone rubber are briefly introduced.

1. Introduction to characteristics and applications of silicone rubber

Silicone rubber polymer molecule is a chain structure connected by Si-O (silicon-oxygen) bond, the main component of which is high molar mass linear polysiloxane. Because the Si-O-Si key is the basic bond type, the silicon atom mainly connects the methyl, the side chain introduces a very small number of unsaturated groups, the molecular force is small, the molecule is helical structure, the methyl is arranged outward and can rotate freely, so that silicone rubber has better heat resistance, electrical insulation, chemical stability and so on than other ordinary rubber. Typical silicone rubber is poly-formaldehyde siloxane, with a spiral molecular configuration, its intermolecular force is small, so it has a good resilience, while pointing to the spiral outside the formaldehyde base can be freely rotated, so that silicone rubber has a unique surface properties, such as hydrophobicity and surface anti-stickiness. The following table lists the main features and uses of silicone rubber.

Heat resistance: Silicone rubber has much better heat resistance than ordinary rubber, can be used almost forever at 150 degrees without change in performance, can be used continuously at 200 degrees for 10,000 hours, and may be used for a period of time at 350 degrees. Widely used in demanding heat-resistant situations: Thermos bottle sealing ring pressure cooker ring heat-resistant handle

Cold resistance: ordinary rubber late for-20 degrees ~-30 degree, that is, silicone rubber in-60 degrees ~-70 degree still has a good elasticity, some special formula of silicone rubber can also withstand very low temperature. Low Temperature sealing ring

Weather resistance: Ordinary rubber degrades rapidly under the action of ozone produced by corona discharge, while silicone rubber is not affected by ozone. And for a long time in ultraviolet and other climatic conditions, its physical property has only minor changes. Sealing materials for outdoor use

Electrical properties: Silicone rubber has a high resistivity and maintains a stable resistance value over a wide temperature and frequency range. At the same time, silicone rubber has good resistance to high voltage corona discharge and arc discharge. High Voltage insulator TV high pressure cap electrical parts Other

Conductivity: When conductive fillers (such as carbon black) are added, silicone rubber has a keyboard conductive contact point

Thermal conductivity: When adding some heat conduction filler, silicone rubber will have thermal conductivity heat sink thermal gasket copier, fax machine heat conduction roller

Radiant: The radiation resistance of silicone rubber containing benzene greatly improves the connectors for electric insulated cable nuclear power plants, etc.

Flame Retardant: Silicone rubber itself combustible, but when adding a small amount of anti-combustion agent, it has flame retardancy and self-extinguishing, and because silicone rubber does not contain organic halides, so burning without smoke or release of poison gas. A variety of strictly fireproof occasions

Breathability: Silicone rubber film has better breathability than ordinary rubber and plastic wax film. Another feature is that it has a strong selectivity to different breathability rates. Gas exchange membrane medical supplies artificial organs

2. The main properties and applications of silicone rubber: silicone rubber According to its vulcanization temperature, can be divided into high temperature (heating) vulcanization type and room temperature vulcanization type two categories, high-temperature adhesive is mainly used in the manufacture of a variety of silicone rubber products, while room temperature glue is mainly used as adhesives, sealing materials or molds.

(1) Thermal vulcanized silicone Rubber (HTV) Thermal vulcanized Silicone Rubber (HTV) is an important category of silicone products, methyl vinyl silicone rubber (VMQ) is the main variety of HTV *, commonly known as high temperature glue. Methyl vinyl Silicone rubber (raw rubber) is colorless, odorless, non-toxic, no mechanical impurities of the glue, raw rubber according to the need to add appropriate reinforcement agent, structural Control agent, vulcanizing agent and other additives mixed together, and then heating molding or extrusion molding, and then through two sections of vulcanization into a variety of products. Its products have excellent electrical insulation, anti-arc, Corona, EDM ability, waterproof, moisture-proof, impact resistance, good earthquake resistance, with physiological inertia, breathability and other properties. Mainly used in aviation, instrumentation, electrical and electronic appliances, navigation, metallurgy, machinery, automotive, medical and health departments, can do a variety of shapes of seals, gaskets, tubes, cables, can also do ****, blood vessels, breathable film and rubber molds, precision casting mold release agent.

(2) room temperature vulcanized Silicone Rubber (RTV) room temperature vulcanized silicone rubber generally includes condensation type and addition molding two categories. The molded room temperature adhesive is based on the vinyl linear polysiloxane as the base adhesive, with hydrogen siloxane as crosslinking agent, in the presence of the catalyst at room temperature to medium temperature cross-linked reaction and become elastomer. It has good heat resistance, hydrophobicity, electrical insulation, at the same time, due to the introduction of active end base, so that it has excellent physical and mechanical properties, especially in tensile strength, relative elongation and tear strength has been significantly improved. It is suitable for a variety of vulcanization methods, such as radiation vulcanization, peroxide vulcanization and molding vulcanization, widely used in heat resistance, moisture-proof, electrical insulation, high-strength silicone rubber products. Condensation type room temperature vulcanized silicone rubber is characterized by the condensation reaction between silicon hydroxyl group and other active substances, at room temperature can be crosslinked into elastomer silicone rubber, the product is divided into single-part packaging and double-part packaging two forms. Single component room temperature vulcanized silicone rubber (referred to as RTV-1 gum) is one of the main products in condensed liquid silicone rubber. It is usually prepared from basic polymers, crosslinking agents, catalysts, fillers and additives. Product packaging in the sealed hose, when used extrusion, contact with the air can be self-vulcanized into elastomers, the use of extremely convenient. Vulcanized adhesive can be used in the (–60~+200℃) temperature range for a long time, with excellent electrical insulation properties and chemical stability, water resistance, ozone, resistance to climate aging, a variety of metal and non-metallic materials have good adhesion. Mainly used as a variety of electronic components and electrical equipment Shang, sealing materials from insulation, moisture-proof, shockproof effect, as a semiconductor device surface protection materials, can also be used as sealing filler and elastic adhesives. Two-component room temperature vulcanized silicone rubber (referred to as RTV-2 gum) is not easy to use RTV-1 glue, but the proportion of its components are rich in change, a variety can get a variety of specifications of the performance of sulfide products, but also deep vulcanization, so it is widely used in electronic appliances, automobiles, machinery, construction, textiles, chemicals, light industry, Printing and other industries for insulation, packaging, seam, sealing, moisture-proof, seismic and production of roller materials. In addition, due to the excellent demoulding nature of RTV-2, it is widely used as a soft mold material for the reproduction and manufacture of cultural relics, handicrafts, toys, electronic appliances, mechanical parts, etc. One of the typical applications of silicone sealants is the glass curtain wall. The glass and aluminum alloy frame is bonded with silicone structure adhesive as the external wall material, and the expansion joint is used as waterproof seal with silicone weathering adhesive. Other applications include the surrounding seals for aluminum alloy doors and windows and plastic steel doors and windows, the stitching of glass mounting and moving grooves, the sealing of rivets and fixing screws: kitchens, bathrooms, sanitary ware in toilets and waterproof seals between countertops, walls and furniture, and seals for aquariums, canopies, metal caps, windows, counters, wall panels and colored steel plates , And is used for waterproof seam sealing between plate of high grade highway. In addition to building sealants, RTV also includes sealing materials for aerospace, nuclear power plants, electronics, machinery, automobiles and other industries, silicone sealing materials for the sealing of electronic components, silicone mold adhesives for soft mold materials, etc. The demand for these varieties is relatively small, but in many cases it is indispensable.

TECHNICAL

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硅橡胶，改变我们的生活

硅橡胶是有机硅产品中产量较大、应用较为广泛的一大类产品。硅橡胶硫化后具有优异的耐高、低温、耐候性、憎水、电气绝缘性、生理惰性等特点，在国防军工、医疗卫生、工农业生产及人们的日常生活中获得了广泛应用。本文对硅橡胶的主要特点和未来发展方向做了简介。

1．硅橡胶的特点和用途简介

硅橡胶高聚物分子是由Si-O（硅-氧）键连成的链状结构，其主要组成是高摩尔质量的线型聚硅氧烷。由于Si-O-Si键是其构成的基本键型，硅原子主要连接甲基，侧链上引入极少量的不饱和基团，分子间作用力小，分子呈螺旋状结构，甲基朝外排列并可自由旋转，使得硅橡胶比其他普通橡胶具有更好的耐热性、电绝缘性、化学稳定性等。典型的硅橡胶即聚二甲醛硅氧烷，具有一种螺旋形分子构型，其分子间力较小，因而具有良好的回弹性，同时指向螺旋外的甲醛基可以自由旋转，因而使硅橡胶具有独特的表面性能，如憎水性及表面防粘性。下表列出了硅橡胶的主要特点和用途。

耐热性：　硅橡胶比普通橡胶具有好得多的耐热性，可在150度下几乎永远使用而无性能变化；可在200度下连续使用10，000小时；在350度下亦可使用一段时间。　广泛应用于要求耐热的场合：热水瓶密封圈　压力锅圈耐热手柄

耐寒性：　普通橡胶晚点为-20度~-30度，即硅橡胶则在-60度~-70度时仍具有较好的弹性，某些特殊配方的硅橡胶还可承受极低温度。　低温密封圈

耐侯性：　普通橡胶在电晕放电产生的臭氧作用下迅速降解，而硅橡胶则不受臭氧影响。且长时间在紫外线和其他气候条件下，其物性也仅有微小变化。　户外使用的密封材料

电性能：　硅橡胶具有很高的电阻率　且在很宽的温度和频率范围内其阻值保持稳定。同时硅橡胶对高压电晕放电和电弧放电具有很好的抵抗性。　高压绝缘子　电视机高压帽　电器零部件　其他

导电性：　当加入导电填料（如碳黑）时，硅橡胶便具有　键盘导电接触点

导热性：　当加入某些导热填料时，硅橡胶便具有导热性　散热片　导热密封垫　复印机、传真机导热辊

辐射性：　含有苯基的硅橡胶的耐辐射大大提高　电绝缘电缆　核电厂用连接器等

阻燃性：　硅橡胶本身可燃，但添加少量抗燃剂时，它便具有阻燃性和自熄性；且因硅橡胶不含有机卤化物，因而燃烧时不冒烟或放出毒气。　各种防火严格的场合

透气性：　硅橡胶薄膜比普通橡胶及塑料打腊膜具有更好的透气性。其另一特征就是对不同的透气率具有很强的选择性。　气体交换膜医用品　人造器官

2．硅橡胶的主要性能及应用：硅橡胶按其硫化温度，可分为高温（加热）硫化型及和室温硫化型两大类，高温胶主要用于制造各种硅橡胶制品，而室温胶则主要是作为粘接剂、灌封材料或模具使用。

（1）热硫化硅橡胶（HTV）　热硫化硅橡胶（HTV）是有机硅产品中*重要的一类，甲基乙烯基硅橡胶（VMQ）是HTV中*主要的品种，俗称高温胶。　甲基乙烯基硅橡胶（生胶）是无色、无臭、无毒、无机械杂质的胶状物，生胶按需要加入适当的补强剂、结构控制剂、硫化剂等助剂一起混炼，然后升温模压成型或挤出成型，再经二段硫化做成各种制品。其制品具有优良的电绝缘性，抗电弧、电晕、电火花能力强，防水、防潮、抗冲击力、抗震性好，具有生理惰性，透气性等性能。　主要用于航空、仪表、电子电器、航海、冶金、机械、汽车、医疗卫生等部门，可做各种形状的密封圈、垫片、管、电缆，也可做****、血管、透气膜以及橡胶模具，精密铸造的脱模剂等。

（2）室温硫化硅橡胶（RTV）　室温硫化硅橡胶一般包括缩合型和加成型两大类。　加成型室温胶是以具有乙烯基的线性聚硅氧烷为基础胶，以含氢硅氧烷为交联剂，在催化剂存在下于室温至中温下发生交联反应而成为弹性体。它具有良好的耐热性、憎水性、电绝缘性，同时由于活性端基的引入，使其具有优异的物理机械性能，尤其是在抗张强度、相对伸长和撕裂强度上有了明显的提高。它适用于多种硫化方法，如辐射硫化、过氧化物硫化及加成型硫化，广泛用于耐热、防潮、电绝缘、高强度硅橡胶制品等方面。　缩合型室温硫化硅橡胶是以硅羟基与其他活性物质之间的缩合反应为特征，于室温下即可交联成为弹性体的硅橡胶，产品分为单组份包装和双组份包装两种形式。单组分室温硫化硅橡胶（简称RTV-1胶）是缩合型液体硅橡胶中主要产品之一。通常由基础聚合物、交联剂、催化剂、填料及添加剂等配制而成。产品包装在密封软管中，使用时挤出，接触空气后能自行硫化成弹性体，使用极为方便。硫化胶能在（–60～+200℃）温度范围长期使用，具有优良的电气绝缘性能和化学稳定性，能耐水，耐臭氧，耐气候老化，对多种金属和非金属材料有良好的粘接性。主要用作各种电子元器件及电气设备的涂复，包封材料起绝缘，防潮，防震作用；作为半导体器件的表面保护材料；也可作为密封填隙料及弹性粘接剂等。　双组分室温硫化硅橡胶（简称RTV-2胶）使用上没有RTV-1胶方便，但其组分比例富于变化，一个品种可以得到多种规格性能的硫化制品，而且还能深度硫化，因而被广泛用于电子电器、汽车、机械、建筑、纺织、化工、轻工、印刷等行业作绝缘、封装、嵌缝、密封、防潮、抗震及制作辊筒的材料。此外，由于RTV-2具有优异的脱模性，因而作为软模材料大量用于文物、工艺品、玩具、电子电器、机械零件等的复制与制造。　有机硅密封胶的典型应用场合之一是玻璃幕墙。将玻璃与铝合金框架用有机硅结构胶粘接作为外墙材料，伸缩缝则用有机硅耐候胶做防水密封。其他方面的应用还包括用于铝合金门窗和塑钢门窗的周边密封，玻璃安装及移动槽的拼缝、铆钉及固定螺丝的密封：厨房、浴室、洗手间的卫生洁具及台面、墙体、家具之间的防水密封；水族馆、天棚、金属顶盖、橱窗、柜台、护墙板、彩钢板的密封；用于高等级公路板块间的防水嵌缝密封等。　RTV除了建筑用密封胶以外，还包括用于航空航天、核电站、电子、机械、汽车等行业的密封材料，用于电子元器件灌封的有机硅灌封材料，用作软模材料的有机硅模具胶等。这些品种的需求量相对较少，但在很多场合却是不可少的。