Silicone cure characteristics

C]-Urea Cure characteristics Cured meat Cured silicone LIM Cure rate... 

Technology which couples fast ultraviolet (UV) cure response with silicone performance characteristics suitable for integrated circuit protection has been developed. One-part silicones which can be cured in several seconds to provide products of excellent purity, stress relief, thermal stability, and protection against harsh environments are the result. 

Cure time testing tends to be somewhat subjective, but again there are methods available, such as ASTM C-679, Tack-Free Time of Elastomeric Sealants. Tack-free time is the curing time required for the product to develop a skin that is not damaged when subjected to application and removal of a plastic film. It is important in all cases to determine the cure characteristics of the product in actual working conditions. Since most silicones cure by reaction with moisture in the air, the sensitivity of cure time to humidity should be determined. Surface cure rates can usually be tailored to meet application requirements. 

McConville, C. Andrews, G. P. Laverty, T. P. Woolfson, A. D. Malcolm, R. K., Rheological Evaluation of the Isothermal Cure Characteristics of Medical Grade Silicone Elastomers. J. Appl. Polym. Sci. 2010,116, 2320-2327. 

Silicone resins are frequently used to coat materials to provide desired characteristics. The measurement of silicone films on paper products has also been performed. A silicone curing reaction on a paper substrate was studied using NIR. The degree of cure could be followed by the disappearance of the Si—OH bands and the appearance of Si—C—H bands. 

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. 

When formulating a silicone adhesive, sealant, or coating, based on hydrosilylation addition cure, one must consider the following properties of the uncured product pot life, dispensing technique, rheology, extrusion rate, cure performance. These characteristics directly affect the processing properties of the polymer base or crosslinker parts. The degree of cure conversion at the temperature of interest is determined by properties such as tack free time, cure profile and cure time. Once... 

Ethyl p-aminobenzoate was used as the test compound for determining release characteristics. It was suspended in silicone elastomer base (Dow Corning Silastic, type 382). After the benzoate was thoroughly dispersed in the elastomer, the catalyst was added and the voids in the device were immediately filled. When cured, excess rubber was trimmed off so that the bottoms of the cells were flush with the lower surface of the device. 

This compounded cured elastomer or rubber99 shares with all the other methyl silicone products the common characteristic of exceptional thermal stability. The material does not melt when heated in air at 300° C., which is far above the decomposition temperature of natural rubber or of any of the synthetic organic elastomers. Service over long periods of time at 150° C. does not destroy its elasticity. 

Summary The backgrounds for elastomer and glassy silicone compositions cured by a polyaddition mechanism have been developed. Their thermal stability as a function of basic sdoxane chain framework and change in some physical-chemical and physical-mechanical characteristics over a wide temperature range are studied. 

Planarization and Adhesion Characteristics. The adhesion of the SOG films on unpatterned surfaces of silicon, thermal Si02 and aluminum was qualitatively evaluated by placing cured SOG films on the various substrates in boiling water for 30 min. No detachment or lifting-off of either film from any substrate was observed. However, it was found that SOG 203 spun on aluminized substrates had a tendency to form cracks (craze) upon cure at 400°C indicating poor adhesions, or, more likely, mismatch of thermal expansion coefficients of the two materials. 

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