Silicone rubber modification

ADVANTAGES IN MODIFICATION OF NONDEGRADABLE SILICONE RUBBER FOR BIOMEDICAL APPLICATIONS... 

Price C, Waters MGJ, Williams DW, Lewis MAO, and Stickler D. Surface modification of an experimental silicone rubber aimed at reducing initial candidal adhesion. J Biomed Met Res, 2002, 63, 122-128. 

As neutral carriers for the chemical modification, 16-crown-5 and calix[4]arene derivatives possessing a triethoxysilyl group (7) and (8) were designed for Na sensors. Triethoxysilylethyl-16-crown-5(7) was then mixed with a silicone-rubber precursor for the membrane fabrication accompanying covalent bonding of the neutral carrier. Comparison of IR spectra before and after extraction of the nonbonded neutral carrier... 

SCHEME 1 Mechanism for chemical modification of poly(dimethysiloxane) (silicone rubber) membranes with ion-sensing active material. 

Membranes with extremely small pores ( < 2.5 nm diameter) can be made by pyrolysis of polymeric precursors or by modification methods listed above. Molecular sieve carbon or silica membranes with pore diameters of 1 nm have been made by controlled pyrolysis of certain thermoset polymers (e.g. Koresh, Jacob and Soffer 1983) or silicone rubbers (Lee and Khang 1986), respectively. There is, however, very little information in the published literature. Molecular sieve dimensions can also be obtained by modifying the pore system of an already formed membrane structure. It has been claimed that zeolitic membranes can be prepared by reaction of alumina membranes with silica and alkali followed by hydrothermal treatment (Suzuki 1987). Very small pores are also obtained by hydrolysis of organometallic silicium compounds in alumina membranes followed by heat treatment (Uhlhom, Keizer and Burggraaf 1989). Finally, oxides or metals can be precipitated or adsorbed from solutions or by gas phase deposition within the pores of an already formed membrane to modify the chemical nature of the membrane or to decrease the effective pore size. In the last case a high concentration of the precipitated material in the pore system is necessary. The above-mentioned methods have been reported very recently (1987-1989) and the results are not yet substantiated very well. 

Effect of surface modification on pull-out force of PPTA silicone rubber composite ... 

Inagaki, N., Tasaka, S. and Kawai, H. (1992). Surface modification of Kevlar 49 fiber by a combination of plasma treatment and coupling agent treatment for silicon rubber composite. J. Adhesion Sci. Technol. 6, 279-291. 

For instance, the modification of silicone rubbers, poly-(tetrafluoroethylene), polyethylene, and segmented polyurethanes by ionic attachment of heparin was shown to result in a decrease of platelet adhesion onto these polymers71 74 75. A similar... 

The surface of PDMS is hydrophobic which results in poor wettability with aqueous solvents and promotes non-specific protein adsorption. It is also relatively inert to chemical modification [25]. The liquid silicon rubber chosen for fabrication of the reaction plate contained pyrogenic silicic acid as a filler. Aside from its effect on elastomer properties the silicic acid can be expected to provide additional silanol... 

The hydrophobicity of the surface prevents the wetting by tear and tends to expose dry surface of a contact lens. Therefore, rapid dehydration of the corneal tissues could occur, which could cause the damage of corneal epithelium. However, this explanation seems to be oversimplified in light of the adsorption of protein, which makes a hydrophobic surface wettable by tear fluid, as described in Chapter 26. Moreover, the highly hydrophobic surface characteristic of silicone rubber tends to encourage the deposition of protein and mucus of the tear on the surface of the lens. Lipids and lipid-soluble materials follow the same track and eventually penetrate into the bulk phase of the contact lens. Because of these undesirable factors, the use of silicone contact lenses of various chemical compositions and with surface treatments has not been successful but rather disastrous because of the interfacial characteristics of silicone contact lens on the cornea, which cannot be oflfset by these efforts. It indicates that more profound surface modification to cope with the problems rather than mere surface treatment is needed in capitalizing on the advantageous bulk properties of silicone polymers. 

The modification of PPS with silicone rubber and aminosilane improves the mechanical properties. It is believed that the aminosilane functions as a type of compatibilizer between the silicone rubber and PAS. It has been found that PAS resins lacking an aminosilane additive and containing a functionalized silicone rubber have different impact and elongation characteristics compared to PAS resins containing a non-functional-ized silicone rubber and an aminosilane. It is believed that the aminosilane, non-functionalized silicone rubber, and PAS components undergo a reaction in the melt. ... 

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