Cross linking techniques

There has been interest, particularly in Japan, in the production of cross-linked low-density polyethylene foam. Some processes, such as the Furukawa process and the Hitachi process, use chemical cross-linking techniques whilst others, such as the Sekisui process, involve radiation cross-linking. 

Bouizar, Z., Fouchereau-Person, M., Taboulet, J., Moukhtar, M.S., and Milhaud, G. (1986) Purification and characterization of calcitonin receptors in rat kidney membranes by covalent cross-linking techniques. Eur. J. Biochem. 155, 141-147. 

Oner, L. and Groves, M.J. (1993b). Properties of human albumin microparticles prepared by a chilled cross-linking technique. J. Pharm. Pharmacol., 45, 866-870. 

In 2001, Franco et al. [52] reviewed an alternative method using a cross-linking technique to improve the durability of polysaccharide CSPs. Kimata et al. 

These monoclonal antibodies to the rabbit prolactin receptor showed little or no cross-reaction with the rat receptor, and monoclonal antibodies have therefore been prepared also to the receptor from rat liver [51]. Two such antibodies were produced, which recognized prolactin receptors from several different rat tissues but did not cross-react with receptors from other species. Studies with these antibodies confirmed the Mr of the prolactin receptor (or its subunit) as 42000 - 46000, close to the value obtained by cross-linking techniques (see above). Biological effects of these monoclonal antibodies were not reported, although stimulatory actions of polyclonal antibodies to the rat prolactin receptor have been described [47,48,52]. 

The topography of Complex IV with respect to the membrane has been studied both by the aid of several kinds of labelling and cross-linking techniques (see Refs. 85, 92, 95, 96, 99), and by image reconstruction of two-dimensional crystal structures [102-106]. The wealth of this information may be summarised as the model in Fig. 

Tayade PT, Kale RD. Encapsulation of water insoluble drug by a cross-linking technique Effect of process and formulation... 

Researchers identified hnRNP proteins by first exposing cultured cells to high-dose UV irradiation, which causes covalent cross-links to form between RNA bases and closely associated proteins. Chromatography of nuclear extracts from treated cells on an oligo-dT cellulose column, which binds RNAs with a poly(A) tail, was used to recover the proteins that had become cross-linked to nuclear polyadenylated RNA. Subsequent treatment of cell extracts from unlrradiated cells with monoclonal antibodies specific for the major proteins identified by this cross-linking technique revealed a complex set of abundant hnRNP proteins ranging in size from 34 to 120 kDa. 

Thermoplastic resins can be further processed by cross-linking techniques to produce thermosets. 

In the literature several methods to chemically modily poly(styrene) have been reported. The interest in the surface functionalization stems from the need to improve cell adhesion on PS petri-dishes for medical and biological applications, while PS cross-linking techniques were investigated for potential application as lithography resist. However, only two of the numerous reported techniques proved to be effective and suitable for the mesoporous styrenic templates, namely exposure to ozone or plasma ignited in several atmospheres, such as nitrogen, air, oxygen, and water vapor. 

The application of cross-linking techniques has the potential to correct damage to wool fibers that is caused by peptide bond hydrolysis occurring during processing. 

Novel photoinitiated mechanisms of polymerization have also been developed to pattern cellular behavior within bulk hydrogel constmcts. For example, a sequential cross-linking technique was used to pattern MSG spreading within adhesive and enzymatically degradable HA... 

Nawawi and Hassan (2003) prepared homogeneous (unmodified) and cross-linked chitosan (extracted from shrimp shells) membranes. Chitosan membranes were modified via a chemical cross-linking technique. PV experiments were done using an IPA-water system. From the PV experiments, it was observed that chitosan membranes exhibited preferential permeation to water. The modified chitosan membrane showed a lower permeation flux, but a higher separation factor than the unmodified membranes. The modified chitosan membrane had a better PV performance than the unmodified membranes in terms of a PSI. 

A material which hardens or sets by heat, chemical, or radiation cross-linking techniques and which, once set, cannot be resoftened by heating. 

The other types of capillary columns are shown in Figure 6.3, the SCOT or support-coated open tubular column, on the left, and the PLOT or porous layer open tubular column, on the right. SCOT columns contain an adsorbed layer of very small solid support (such as Celite ) coated with a liquid phase. SCOT columns can hold more liquid phase, and have a higher sample capacity than the thin films common to the early WCOT columns. However, with the introduction of cross-linking techniques, stable thick films are possible for WCOT columns, and the need for SCOT columns has disappeared. A few SCOT columns are still commercially available but only in stainless steel tubing. 

Thick films (1.0 pm or greater) are made possible today due to improved techniques in cross-linking liquid phases, and also to the more inert fused silica surface. Cross-linking techniques will be discussed later in this chapter. Such thick films show increased retention of sample components—essential for volatile compounds. In addition, their high capacity allows injection of larger samples this can be important when mass spectrometers or Fourier transform-infrared spectrometers are to be used for subsequent analysis. 

Accelerated-sulfur vulcanization is the most widely used method. For many applications, it is the only rapid cross-linking technique that can, in a practical manner, give the delayed action required for processing, shaping, and forming before the formation of the intractable vulcanized network. It can be used to vulcanize natural rubber (NR), synthetic isoprene rubber (IR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), butyl rubber (HR), chlorobutyl rubber (CIIR), bromobutyl rubber (BUR), and ethylene-propylene-di-ene-monomer rubber (EPDM). The reactive moiety for all of these elastomers can be represented by... 

---