Silicone ElastomersPeter Jerschow (Wacker-Chemie GmbH) ISBN: 1-85957-297-9 . ........................................................... 3............................................................................................................................................................................. 5.............8 Food Sector .................4 3..............................................................................................................................................................................................................................................................................................................................3 Wire and Cable ....................... 27 5..................... 24 Spin Casting............... 13 3........................................................1 Speciality Mould Making RTV-2 Materials .............. 29 5................................ 29 5.................................................................. Introduction ... 33 5.............................................................. 25 4..1 General ........................................1 Introduction and Classifications .... 5 2....................................... 6 3.............................2 3........5 ....................................................7............................................................ 32 5................... 7 3........................................................ 26 Room Temperature Vulcanising Silicone Elastomers ............. 33 1 .....8 Condensation Curing RTV-2 Compounds for Encapsulation ...................................6 Electronics ........... 32 5................................... 23 Aerospace ........................9................................................... 7 4..........................5 Transmission and Distribution .............................................. 20 3..... 16 3............................................. 21 3...............................................9 Adhesives and Sealants Based on Condensation Curing RTV-2 Compounds .........................................6 Condensation Curing RTV-2 Systems ....................................................................... 28 5..........3 RTV-1 for CIPG and FIPG ............................7 Mould Making ........... 27 5........... 25 4............ 24 Pharmaceutical .......3 3.....................................7 Mould Making Condensation Curing RTV-2 Materials ................................................................10 Addition Curing RTV-2 Systems ...........................4 RTV-1 for Baking Tray Coatings ..... 9 3.........................4 Sanitary............................................ 28 5........................................................................................................................... 31 5..............9............................................. Household and Leisure .....................................................1 Nomenclature.......................................................................................................................................................................................1 Automotive ................................................................. 17 3.................................2 Healthcare and Medical ......................................................................Silicone Elastomers Contents 1............................................. Silicone Elastomers Market ..................................................................................... 24 Composition and Function of Silicone Elastomers...................... 5 1................................ 23 Safety Applications ........5 Adhesive RTV-1 Materials .......... 24 Building Industry ..........2 Properties of Silicone Elastomers .....................................................9.....................................................................................................................................................................................................2 Condensation Curing RTVs ...............................9 Other 3.................................11 3................................. 25 4.......1 3...............9................................................... Applications for Silicone Elastomers ...................................................................................................................................................................................................................................................... 31 5.................................................................................................................................................................9........................3 Chemistry and Curing Mechanisms of Silicone Elastomers .. ............14 Addition Cured RTV-2 Adhesives and Sealants ..............4......11 Silicone Gels ...................................................11 HTV for Transmission and Distribution (T&D) Applications ............1 General ...... 34 5.........................7 Self Adhesive LR ..................... 47 7................................................... 39 6............................................... 50 7..................................................................... 37 6................................... 50 7.....6 Oil Resistant LR (NPC) ..................................... 50 7................. 37 6..................................1 Addition Cure ......... 40 6....................................2...............................4............ 49 7...................1 High Tear LR ..............................................................................1 Introduction ..................................5 Addition Cured HTV ............. 47 6.....................................................................4.........................................................................................5...............................2 Peroxide Cure ........................................................................................................................................................ 47 7...........................................................................................................................9 Steam Resistant HTV .......................5 Self Lubricating LR (NPC) ............................... 46 6.................................................................. 41 6.............................................................3 Extrusion HTV ............................................................................................10 Extra Liquid Rubber (XLR®) .................................................................................... 2 Liquid Silicone Rubber ............4.................................................................................4......4 Speciality HTV (all peroxide) ..................................................................................2 Curing Mechanisms of Solid Silicone Rubbers.......................................................................................................................................................3 Heat Stabilised LR .................................................................................. 50 7.....Silicone Elastomers 5... 48 7.............. 38 6..............2 Addition Curing ............. 47 Solid Silicone Rubber ...................... 42 6........15 Addition Cured RTV-2 Foam for Compressible Gaskets ................................................................................................................................ 53 7..........................4....................................4.....................................5 Pigment Pastes ......4........................................... 7.......................... 41 6................. 39 6...........................4.................................................3 Standard Solid Silicone Rubbers ....................................................................................................................................5 Oil Resistant HTV (NPC) ......................................................................................... 51 7......................................8 High Green Strength/Coolant Resistant HTV .....................................................................................................4..... 47 6.4......12 Addition Curing Systems for Mould Making ................................ 42 6.....4.................................................................................................................................................................4..................................................................................2 Economy High Tear HTV .................................11 Other Types of LR .........2 Curing Mechanism of Liquid Silicone Rubbers .1 High Tear HTV ............................................................4..............................................................6 Electrically Conductive HTV .. 39 6....2............................................. 48 7............4...................... 49 7............................4.......... 50 7.......................4...........................................................4 Cable HTV ................9 Flame Retardant LR ...4. 46 6.......................... 52 7......... 36 6.....................................................................................................................................4................................................................................................4...........................4... 53 7.......................................................................................4 Coolant Resistant LR (NPC) .................... 52 7..................................................4................ 51 7.8 Electrically Conductive (Antistatic Silicone!) LR ................. 50 7............................................................................................. 36 5......................5................................................................................10 Heat Conductive HTV ....... 53 ................................1 General ....4 Speciality LRs ................................7 Super Heat Stable HTV .........2 No Post Cure LR .... 53 7....... 35 5............ 52 7.. 37 6....................................................................................................................13 Addition Cured RTV-2 Systems for Encapsulation ................................................ 35 5..................3 Standard Liquid Silicone Rubbers .................... ...........................................................................................................4 7........................................................ 58 8......1 Mould Making: Flexible Moulds .. 65 Abbreviations and Acronyms ......................................3 LR and HTV .............................. 62 8......................................3............................3 Injection Moulding LR and HTV ....................1 RTV-1 Systems ...............................................................................................................................................................5..........................................................3.....3.............3...... 55 Moulding: 2K Addition Cured HTV ............. 55 Extrusion HTV ..........................................2.......................................................... 58 8.................... 56 Post Curing of Addition Cured HTV ..2..3 Mould Making: Skin Moulds ......6 7........................................................................... 58 8..... 62 8.........................5 Moulding HTV (General) ...................................................................................................8 Bonding .......................................................................................................................... 65 References from the Rapra Abstracts Database ..................................7 8...........................................................2................... 56 Processing Silicone Elastomers ................................................................................................... 9...........................................................5..........1 Press Curing HTV ............6 Calendering HTV .............................................................................................................................2 Mould Making: Block Moulds .............................3...........5......... 59 8.............................................................................2 RTV-2 Systems ........... 153 The views and opinions expressed by authors in Rapra Review Reports do not necessarily reflect those of Rapra Technology Limited or the editor......Silicone Elastomers 7......................... 58 8...............................................................................................................3 7.......................................... 63 8.................................................3.............. 56 8.................................. 64 8........5....5..........3............................................ 56 8........... 54 Moulding: 1K Self Adhesive Addition Cured HTV .... 57 8....................................................................................................................... 67 Subject Index ...............7 Rollers .................................................................................................................... 64 Summary .......................................................................................... 64 Additional References ........................................... 58 8............................................................ The series is published on the basis that no responsibility or liability of any nature shall attach to Rapra Technology Limited arising out of or in connection with any utilisation in any form of any material contained therein...............................................3.....................................................2 Transfer Moulding HTV ................................................... Moulding: 1K Addition Cured HTV ..............4 Extrusion of HTV ......................................................................... 56 8................... 3 ........5 7....................................... Silicone Elastomers 4 . It is common to use LSR or LR as an abbreviation instead of HTV.1 Nomenclature Silicone elastomers are elastic substances which contain linear silicone polymers crosslinked in a 3dimensional network. HTV rubbers are mainly so-called solid silicone rubbers. These will be described in more detail when concentrating on specific groups of materials and applications. Silicone rubbers are essentially divided into two groups of materials. chemical or physical properties. a. dialysis apparatus) Anaesthetic tubing (composite) Body contact electrodes X-ray opaque shunts Various pads Wire and cable Wear resistant cables Instrument cables Safety signal cables Safety power cables Battery cables Economy grade cables Heat resistant cables Cable sleeving. Because of their low viscosity and paste-like behaviour they were named liquid silicone rubbers (LSR) or simply liquid rubbers (LR). Approximately 25 years ago a new group of materials appeared that was intended for processing in injection moulding machines. We will not refer too much to silicone adhesives in this article. room temperature vulcanising (RTV) and high temperature vulcanising (HTV). biocompatibility.g. Some examples are shown in Table 1. i. wear resistant Cables from silicone rubber pellets continued… 5 . Hence silicone elastomers can be widely used in a great variety of applications.1.. RTV-2. In most cases this network also contains a filler which acts as a reinforcing agent or as an additive for certain mechanical. They have a very high viscosity in the uncured state and appear as solids.. The nomenclature classifies silicone elastomers by their curing mechanism and curing conditions. in spite of the fact that they form silicone elastomers when being cured.g. even though they vulcanise at high temperatures as in the case of solid silicone rubbers. When silicones are crosslinked to form a silicone rubber their characteristic properties are still prevalent. Table 1 Brief overview of applications for silicone elastomers Application area Applications Automotive Exhaust pipe hangers Crank shaft seals Radiator seals Ignition cables Connector seals Spark plug boots Medical Catheters Respiration masks Various valves (e.Silicone Elastomers 1 Introduction 1. This behaviour has also led to the creation of the term ‘High Consistency Rubber’ (HCR).e. In general all silicones (usually we refer to silicones as polydimethyl siloxanes) are noted for their high thermal stability. e.. electrical and release properties. These materials have been referred to extensively in the literature (a. A number in the name indicates the number of components that upon mixing will form a curable composition. RTV systems are able to cure at room temperature and HTV systems at temperatures well above 100 °C. hydrophobic nature.2). Silicone Elastomers Table 1 Brief overview of applications for silicone elastomers continued Application area Applications Sanitary and household Gaskets in tap water equipment Gaskets for toilets O-rings (composite) Various valves Transmission and distribution (T & D) Electronics Medium and high voltage insulators Medium and high voltage cable accessories Anode caps and cables Key pads (composite) Various gaskets Encapsulation Coatings Adhesives Pottings Food appliances Food dispensing valves Various gaskets Baby care articles Mould making Prototyping Models for design and/or display Functional models Pre-series models Working moulds for gypsum Plaster moulding Ornaments and window frames Moulded furniture parts Imitation leather moulds Moulds for shaped foodstuffs (e. RTV-2. high consistency rubber Liquid rubber. Figure 1 shows the market shares between the material categories. In summary the silicone industry uses the terms RTV1. requirements and materials and why to choose silicone elastomers in the cases discussed.g. two component 2 Silicone Elastomers Market HTV LR 6 High temperature vulcanising. In this article I will concentrate on applications. Among all silicone elastomers LR exhibits the highest growth rate and HTV has the highest portion of the market. chocolate) Do-it-yourself (DIY) applications Archaeological applications Restoration For the most part all LR materials are 2 component systems which cure after mixing and at elevated temperatures. RTV-1 Room temperature vulcanising. These refer to the material categories as follows: The second half of this review will concentrate on the various types of silicone elastomers. .000 tons of silicone elastomers. LR or LSR. HTV or HCR. one component RTV-2 Room temperature vulcanising. liquid silicone rubber (which is also cured at high temperatures). In 1999 the global market consumed approximately 170. solid silicone rubber. their chemistry and processing..