Crosslinking electron beam irradiation

The increase in the modulus for Bis A PSF and Hq/Bp PSF with irradiation indicated that crosslinking predominated for both polymers and that the crosslink structures were probably basically similar. Hq/Bp(50) PSF was considerably more radiation resistant than Bis-A PSF, as shown by the rate of decrease in the elongation at failure. For both polymers, there was an initial rapid decrease in the elongation at failure followed by a slower decrease. This effect was also demonstrated by the variation in the fracture toughness (KI(.) with irradiation for Bis-A PSF. This work with cobalt-60 gamma radiation complements earlier studies of these materials using high dose rate electron beam irradiation (6). 

LDPE and EVA were blended in a 80/20 ratio and the non-crosslinked foam thereof was exposed to various doses of electron beam irradiation in air. The foam was made using isobutane as blowing agent. It was found that foam with uniform cell structure was not achieved in the case of pre-crosslinked foam with more than 40% gel fraction. Non-crosslinked foams were, however, easily crosslinked to a gel content of about 57% with electron beam irradiation under optimum conditions. The gel... 

Peroxide crosslinked ionomer mixtures made from the abovementioned raw materials may be used in contact with fatty foods under certain limited conditions, according to their raw materials and additives. Vinyl chloride and vinylidene chloride should not be used in materials having either ionic (ionomer) or physical (e.g. through electron beam irradiation) crosslinks. Crosslinked polyethylene can be used for the manufacture of food contact materials, e.g. for drinking water pipes and fittings. The cross-linking can be done using either peroxide or electron beam irradiation. 

Havens and Bell performed an electron beam irradiation of methylene-bridged aromatic polyesters, which were synthesized by polycondensation between two pairs of aromatic diacid chlorides and 3,3 -methylenediphenol or 4,4 -methylenediphenol [54]. They found that irradiation of thin films of these polyesters at room temperature resulted in some chain extension and cross-linking, and that irradiation at a temperature near or above the glass transition temperatures of the polymers greatly enhanced the tendency for the polymers to crosslink. 

In comparison, electron beam irradiation was also utilized to crosslink isolated CNTs or their ropes of thin SWNT films in order to transform them into high-strength and multifunctional fabrics. It also provides a practical means to mass production of strong CNT membrane materials. Usually, SWNT membranes can be irradiated with electron accelerators. Figure 14.16 shows the effects of... 

Irradiation crosslinking of PVC-U, carried out using electron beam, has shown a marked increase in glass transition temperature in the presence of a triacrylate, with minimal thermal degradation (216). Electron beam irradiation has also been investigated on a PVC-P wire coating formulation in the presence of different reactive monomers (185). Flame retardancy has also been improved with the incorporation of appropriate flame retardants (118). The effect of UV irradiation on formulations, incorporating iron chloride or cobalt chloride, has also been studied (67). 

The main reactions leading to crosslinking of CMS under electron beam irradiation are as follows. 

Moreover, ultrafiltration membranes derived from polyaramide were successfully modified by electron beam irradiation [63]. As displayed in Fig. 9, an increase in retention capability without any change in permeate flux was achieved, due to chemical reactions leading to crosslinks and to the introduction of hydrophilic groups into the polymer backbone. 

Under gamma or electron beam irradiation of NR, several kinds of active species (such as radicals, ion etc) are liberated either inside of NR particles or in the water phase. Further reaction between the active species will easily takes place with the end result a crosslinked NR. The possible reaction mechanism is as following ... 

Crosslinking was done by electron beam irradiation immediately after foam was expanded and was still at elevated temperature. 

The mechanical and physical properties of PLA are severely degraded when subjected to electron beam irradiation [89], because the dissipated energy from the irradiation easily causes chain scission of the backbone chain of PLA and forms free radicals. Additional additives, such as a crosslinking agent, are therefore... 

Yan, S. R, Yin, J. B., Yu, Y., Luo, K., Chen, X. S., Thermo- and pH-sensitive poly(vinylmethyl ether)/carboxymethylchitosan hydrogels crosslinked using electron beam irradiation or using glutaraldehyde as a crosslinker. Polymer International 2009, 58,1246-1251. 

Electron-beam irradiation breaks the acid anhydride linkage, thus restoring solubility to the irradiated areas. Several systems derived from that of Roberts have been studied [33, 34], Resistance to plasma and to developer solvent is improved by the anhydride crosslinking. 

An interesting comparison of the effect of electron beam irradiation on PVDF and ETFE, which differ only in chemical stmcture and have the same chemical composition, has shown that the irradiation has a more detrimental effect on tensile strength for ETFE than PVDF [139]. In fact, PVDF shows an increase in tensile strength compared to ETFE which shows a decease. In both cases, the elongation at break dropped with increasing dose, indicating crosslinking. 

The effect of electron beam irradiation on the miscible poly(styrene) and poly(vinyl methyl ether) (PVME) blend has been studied. The poly (styrene), being much more resistant to effects of irradiation, does not offer any protectimi to the poly(vinyl methyl ether). Gel content studies indicated significant crosslinking [199]. Further studies of this... 

Sharif et reported that NR/OC nanocomposites were prepared by melt blending using electron beam irradiation as a substitute for sulfur. It was found that the physical and mechanical properties of radiation-induced crosslinking of NR composites with OC were improved due to the presence of nanosize intercalated silicate layers in the NR matrix. Replacing sulfur with radiation-induced crosslinking of NR/OC nanocomposites was not significantly affected by the amount of OC up to 10 phr. Meanwhile, the thermal stability of NR/OC nanocomposites improved with an increase in clay content up to 10 phr. 

If the reactive blending is stopped at an intermediate stage, the micelles and the shrunken particles coexist and a bimodal particle distribution is realized, as shown in Fig. 8.39. In the case of Fig. 8.39, PA-6 was mixed with polyethylene (PE) modified with a small amount of MAH (0.1 wt%) and glycidyl methaciylate (3-12 wt%), at a 70/30 (PA/PE) blend ratio. The bimodal system can be easily crosslinked by electron beam irradiation at a low dose level, the same as that used for neat PE (Pan et al. 2002). The crosslinked PA/PE alloy shows good heat resistance in a lead-free solder test thus, it may be applied in making construction parts with melt-down resistance in fires, e.g., a window frame. 

Banik, 1., Bhowmick, A.K. Effect of electron beam irradiation on the properties of crosslinked rubbers. Radiat Phys. Chem. 58, 293-298 (2000)... 

Choi, J.H., Jung, C.H., Kang, D.W., Hwang, I.T., Choi, J.H. Preparation and characterization of crosslinked poly( -caprolactone)/polyhedral oligomeric silsesquioxane nanocomposites by electron beam irradiation. Nucl. Instrum. Meth. Phys. Res. B 287, 141-147 (2012)... 

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