Microwave crosslinking

This approach has recently been extended by the same group for the synthesis of noncovalently crosslinked nanoparticles, which can be formed reversibly upon application of external stimuli (Seo etal, 2008). This group have also recently reported the application of microwave crosslinking chemistries for the synthesis of collapsed and functionalized polymer... 

Bogdal, D., Penczek, E, Pielichowski, J. and Prociak, A. Microwave Assisted Synthesis, Crosslinking, and Processing of Polymeric Materials. Vol. 163, pp. 193-263. 

Figure 4. Variation of the linewidth of the parallel signal for Cu(ll) in crosslinked polyacrylamide gels of pore diameter 0.7 nm as a function of the microwave frequency, for mj = -3/2 and -1/2. The solid line is calculated from the values of aH, 6A and 6g given in Table I. Measured values are indicated.

Microwave Supported Crosslinking. Because of abrasion in conventional UHMWPE, the body may react with inflammations and tissue alterations. The mechanical properties can be improved by additional crosslinking. Crosslinking is customarily achieved by way of intermediate stages involving radicals that are produced either by means of ionizing radiation or, by chemical processes. 

Highly crosslinked UHMWPE can be produced by irradiation of a blank UHMWPE with ionizing radiation, in particular by X-rays, y-rays or electron beams, in order to produce radicals. The subsequent treatment of the irradiated material consists in exciting free radicals, which have not recombined, by means of microwave radiation or ultrasound. The process is claimed to ensure a substantially complete recombination of the free radicals. In addition, the crosslinking of the UHMWPE is also further optimized (30). 

The most commonly accepted point of view is that heat is responsible for unmasking the epitopes. In fact, Battifora (1996) has introduced the phrase heat-induced epitope retrieval (HIER). Heating at KXPC is a powerful treatment that can unmask hidden, buried, or crosslinked epitopes. Heat can be provided not only by a microwave oven, but also by an autoclave, a pressure cooker, steam, or a hot plate. A consensus on which method of heating is most effective in the retrieval of all types of epitopes is lacking. Therefore, some... 

As previously discussed, the most used support is variously crosslinked polystyrene, because it is chemically stable in the usual solvents and conditions used with microwave heating. 

Part A and Part B were mixed at weight ratio of 1 1 and placed in a microwave oven and 1 KW energy was applied. The temperature of the mixture reached about 150°C in 3 min and crosslinking reactions took place. The elastomer thus obtained had deep section uniform curing all the way through. The same type of curing was obtained in the absence of Fe203. 

These two experiments demonstrate that the heat generated by the microwave decomposes the peroxide to give radicals, which initiate simultaneously the crosslinking reaction shown below (7,8). 

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