Properties of the Specific Silicone Polymers

1 Actually there are at least 57, for there are four or more outside the numbered series and two within the series which bear supplementary numbers (37a and 45a). The entire numbered series (1 to 51) appears in the Journal of the Chemical Society, and for convenience the papers are listed below by reference to volume and page of that journal. References to specific investigations by Professor Kipping also have been made at the appropriate places in the text. 

Even after a very short experience, it was evident that corresponding derivatives of the two elements in question showed very considerable differences in their chemical properties it may now be said that the principal if not the only case in which they exhibit a really close resemblance is that of the paraffins and those particular silicohydrocarbons, containing a silicon atom directly united to four alkyl radicals.2 

Oddly enough, Kipping had not been concerned primarily with the organosilicon polymers for which his work may best be remembered. He and his students had been interested principally in the preparation and characterization of new compounds, and in the study of their reactions. From such reactions they strove to isolate pure compounds as products, but in certain hydrolytic reactions they constantly were troubled by the appearance of oily or gluelike substances which could not be crystallized and which acted like very complex mixtures when subjected to fractionation procedures. It now seems surprising that they were able to isolate as many of the simpler cyclic and linear polymers as they did, considering the annoying qualities of the resinous masses. 

Nothing in his writings indicates that Kipping foresaw any usefulness in the resinous silicone polymers with which he worked so long. Certainly he made no attempt to develop or apply them. Indeed, his 

We have considered all the known types of organic derivatives of silicon and we see how few is their number in comparison with the purely organic compounds. Since the few which are known are very limited in their reactions, the prospect of any immediate and important advance in this section of chemistry does not seem very hopeful. 

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This chapter first reviews the general structures and properties of silicone polymers. It goes on to describe the crosslinking chemistry and the properties of the crosslinked networks. The promotion of both adhesive and cohesive strength is then discussed. The build up of adhesion and the loss of adhesive strength are explained in the light of the fundamental theories of adhesion. The final section of the chapter illustrates the use of silicones in various adhesion applications and leads to the design of specific adhesive and sealant products. 

A chemical property of silicones is the possibility of building reactivity on the polymer [1,32,33]. This allows the building of cured silicone networks of controlled molecular architectures with specific adhesion properties while maintaining the inherent physical properties of the PDMS chains. The combination of the unique bulk characteristics of the silicone networks, the surface properties of the PDMS segments, and the specificity and controllability of the reactive groups, produces unique materials useful as adhesives, protective encapsulants, coatings and sealants. 

The surface energy of silicones, the liquid nature of the silicone polymers, the mechanical properties of the filled networks, the relative insensitivity to temperature variations from well below zero to very high, and the inherent or added reactivity towards specific substrates, are among the properties that have contributed to the success of silicone materials as adhesives, sealants, coatings, encapsulants, etc. 

A new convenient polymer modification for the conversion of the Si—H to Si—OH by the selective oxidation of the Si—H bond by dimethyldioxirane has been described. The oxyfunctionalization of the silane precursor polymers proceeded rapidly and quantitatively and can be applied to the synthesis of a wide variety of novel silanol polymers with specific properties from the corresponding precursor polymers containing Si—H functional groups. Control over the properties of these silanol polymers, such as reactivity and self-association of silanols, was realized through the placement of different substitute groups bonded directly to the silicon atom and by the variation of silanol composition in a copolymer. These novel silanol polymers with a... 

The atomic composition of polymers encompasses primarily non-metallic elements such as carbon (C), hydrogen (H) and oxygen (O). In addition, recurrent elements are nitrogen (N), chlorine (Cl), fluoride (F) and sulfur (S). The so-called semi-organic polymers contain other non-metallic elements such as silicon (Si) in silicone or polysiloxane, as well as bor or beryllium (B). Although other elements can sometime be found in polymers, because of their very specific nature, we will not mention them here. The properties of the above elements lead to specific properties that are common of all polymers. These are ... 

The use is discussed of Vanquish biocides from Zeneca Biocides. They are antimicrobials developed specifically for the plastics industiy, and have a broad spectmm of activity in a wide range of polymers, including PVC, polyurethanes, polyolefins and silicones. Features and properties of the products are described, and their application in silicone, polyurethane and PVC products is examined. 

Specific physicochemical properties of the supercritical fluids offer flexible alternatives to established processes like chemical vapor deposition (CVD), which is used in the preparation of high-quality metal and semiconductor thin films on solid surfaces. Watkins et al. [43] reported a method named chemical fluid deposition (CFD) for the deposition of CVD-quality platinum metal films on silicon wafers and polymer substrates. The process proceeds through hydrogenolysis of dimethyl-(cyclooctadiene)platinum(ll) at 353 K and 155 bar. 

The curing process takes advantage of the versatile chemical property of silicones. Chemical reactivity is built in the polymer and allows the formation of silicone networks of controlled molecular architectures with specific adhesion properties. The general and inherent molecular properties of the PDMS polymer are conferred to the silicone network. Pure PDMS networks are mechanically weak and do not satisfy the adhesive and cohesive requirements needed for most applications. Incorporation of fillers like silica or calcium carbonate is necessary to reinforce the silicone network (see Composite materials). 

Table 17.1 lists typical thermal conductivity values important to PCB and electronic components. Where a range of material properties is given, multiple factors determine the exact thermal conductivity value. These factors can include the filler percentage and composition in a polymer, or in the case of silicon (Si), the doping type and level. Material property measurement or vendor data should be used to determine the thermal conductivity of the specific material of interest. One alloy of Cu is shown to demonstrate that the Cu alloy... 

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