Crosslinking mechanisms

Further details of each crosslinking mechanism will be discussed below. 

A crosslinking mechanism based on these data was proposed. Initial monoalkylation at guanine is followed by a template-directed alkylation at either guanine or adenine two base pairs away on the opposite strand. In support of this, Armstrong... 

Sulphur vulcanisation of rubber is catalysed by the presence of alkali materials. This activation of the vulcanisation system can result in unwanted short scorch times. The addition of weak acids to the rubber compound results in retardation of the crosslinking mechanism. The common materials used for retardation are... 

By interactive in this context we mean that the filler can adsorb network polymer and thereby become involved in the crosslinking process, creating a larger number of network links. In some cases the polymer-particle interaction may be the main crosslinking mechanism. 

With the purpose of understanding the crosslinking mechanism of 1,2-polybutadiene with aromatic nitrene, we studied the reaction of phenylnitrene with unsaturated olefine monomers such as 3-methyl-1-butene and cyclohexene. These monomers are structually similar to a unit segment of 1,2-polybutadiene. 

Figure 4. Crosslinking mechanism proposed for pectins in presence of Ca2+ (10). Black dots represent the calcium.

Crosslinking of alkyds containing conjugated double bonds results in more carbon-carbon bonds in the crosslinks than in the alkyds containing unconjugated double bonds. The crosslinking mechanism involves the formation and decomposition of cyclic peroxides, to yield radicals that initiate crosslinking by 1,4-polymerization of the polymer molecules. 

Polydiene rubbers can also be crosslinked by heating with p-dinitrosobenzene, phenolic resins, or maleimides [Coran, 1978 Gan and Chew, 1979 Gan et al., 1977, 1978 Sullivan, 1966]. The crosslinking mechanism is similar to that for accelerated sulfur vulcanization, for example, for vulcanization by p-dinitrosobenzene... 

Although this work was carried out with a model compound, the results are quite consistent with the mechanisms suggested by the BP team [86] which was working within a bisnadimide. However, the work of Meador et al. [42] presents some diverging conclusions by minimizing the role of the reverse Diels-Alder reaction in the crosslinking mechanism. 

The conclusions of these works are very similar firstly the crosslinking mechanism is stopped when the vitrification takes place, secondly the Tg values of the networks are mainly dependent on the nature of the starting end-capped oligomer. 

Many other modifications to acrylic adhesives are useful. Improved heat resistance of acrylic adhesives can be achieved by incorporating small amounts of epoxy resin into the formulations,77 or by including cyanate esters and organometallic compounds to provide an additional crosslinking mechanism.78 Lower sensitivity of oxygen can be achieved by... 

Time resolved absorption and emission spectral techniques can be used to probe the reactions occuring during radiolysis or photolysis of CMS and SNR. By identifying the intermediate species we have been able to develop some understanding of the crosslinking mechanism in these resists. 

Figure 4.28. Molecular structures and photoinduced reactions of common photoresists. Shown (top) is the positive tone resist containing the active diazonapthoquinone (DNQ) chromophore group. Chemical amplification (CAM) reactions are illustrated in (i)-(iii). Reaction (i) represents photoinduced acid generation step (ii) is an acid-catalyzed deprotection mechanism (positive tone resist) and step (iii) is an acid-catalyzed crosslinking mechanism (negative tone resist).

In the coatings industry, emulsion polymerization, as a synthetic tool for the preparation of acrylic and vinyl polymers, allows the manufticturer access to a wide array of polymeric systems, simply based on the types and ratios of the monomers used [7]. However, coatings derived fi"om these emulsion polymers often are deficient in performance because of lack of an internal crosslinking mechanism. Silanes can remedy this deficiency. 

Among the silicone rubbers there are different product groups which differ in their crosslinking mechanism and application areas. 

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