Delayed cross-linking systems

Delayed Cross-Linking Systems. As illustrated in Figure 16, high magnitudes and long periods of shear reduce the viscosity of HPG-titanium... 

The action of redox metal promoters with MEKP appears to be highly specific. Cobalt salts appear to be a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cobalt activity can be supplemented by potassium and 2inc naphthenates in systems requiring low cured resin color lithium and lead naphthenates also act in a similar role. Quaternary ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, faciUtating the transition to the lower oxidation state. Copper naphthenate exerts a unique influence over cure rate in redox systems and is used widely to delay cure and reduce exotherm development during the cross-linking reaction. 

Figure 17. Enhanced viscosities with delayed cross-linker. Delayed zirconate cross-linkers produce gels with higher viscosity levels because the network does not develop during the high shear part of the history simulation. In this system cross-linking is initiated as the temperature rises from ambient to 60 C over the first 20 min of the test.

A recently published fast-DC protocol, stimulating monocytes for only 2 days ex vivo in the presence of IFN-y and lipopolysaccharide (LPS), reported tumour-peptide-specific responses (to Her/2b) and decreased tumour volumes in vaccinated breast cancer patients [47], the mechanism being dependent on a delayed IL-12 burst. Alternatively, maturation can be induced in vivo following administration of the antigen-loaded DC with systemically applied antibodies cross-linking stimulatory molecules on DC, such as anti-CD40 antibody [48]. 

The undesirable premature cross-linking of pol5uner chains in the processing step is called scorch the ability of the vulcanization system to withstand the heat of processing without premature cross-linking is called scorch safety. This attribute of delayed action (scorch safety) with fast cure is imique to accelerated sulfur vulcanization, and allows for safe and rapid mixing and fabrication of rubber compounds and parts coupled with rapid cure. 

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