| The present article is mainly concentrated on the photocrosslinking NBR andits related modified works. The results obtained through this paper are dividedinto four areas:Firstly, the photo initiated crosslinking behavior of nitrile rubber (NBR) inthe presence of benzophenone (BP) as a photoinitiator and triallyl isocyanurate(TAIC) as a crosslinker were investigated through the determination of gel con-tent. The properties of photocrosslinked NBR were studied by the mechanicalmeasurement, oil swelling test, thermo gravimetric analysis, differential scan-ning calorimetry, and dynamic mechanical thermal analysis. The results showedthat the gel content increased rapidly with increasing the UV irradiation timeand reached to81.5%within a UV irradiation time of10s. Both mechanicalproperties and oil resistance increased evidently along with UV irradiation time.The data of TGA showed the better thermal stability for the sample irradiatedfor5s. The DSC and DMTA results showed that both glass transaction tempera-ture (Tg) and storage modulus (E’) increased after photocrosslinking.Secondly, the photo (UV)-initiated crosslinking behavior of nitrile rubber/silica and its related properties were investigated. The Results showed that thegel content increased with increasing amounts of silica up to50phr, whereasdecreased with further increasing the amounts of silica. The mechanicalmeasurements showed a remarkable increase in tensile strength, while thecorresponding values of elongation at break decreased. The results of heatextension test and TGA illustrated that the thermal stability of NBR/silicaenhanced evidently along with increasing amounts of silica. The data of DMTAindicated that the increasing amounts of silica restricted the mobility ofmacromolecular chains that led to the increase in storage modulus (E’) and glasstransaction temperature (Tg).Then, photoinitiated crosslinking of NBR/HDPE with the blend ratio50:50inthe prese nce of photoinitiator and crosslinker,the mechanical and physicalproperties were studied as a function of UV irradiation time, as well as thecontent of compatibilizer EVA-g-MA in the blends were investigated throughthe determination of gel content, mechanical test, oil swelling test,volumeresistivity,scanning electron microscopy(SEM),differential scanning calorimetry (DSC). The Results showed that the gel content increased with increasing theirradiation time and reached to89.2%within8s UV irradiation. With increasingthe irradiation time, the tensile strength and oil resistance of materialsincreased.The blends with EVA-g-MA showed an increase in both the tensilestrength and elongation at break for the same irradiation time. The oil resistanceof material improved along with the irradiation time, while decreased withincreasing the EVA-g-MA. The trend is similar to the variation of volumeresistivity. The SEM results revealed that UV irradiation improved the compati-bility between NBR and HDPE, as well as the loading of EVA-g-MA. Theresults of DSC showed that the UV irradiation could accelerate the overallcrystallization process of HDPE first and then impede it with a long-termUV-irradiation.Finally, the NBR/MH/DBOPE blends were photocrosslinked by UV irradia-tion. The related physical and flammability properties have been studied byheat extension test, mechanical test, limiting oxygen index and UL-94verticalcombustion level. The results showed that the vertical combustion level reachedof V-0, and the LOI reached48indivually blending with50phr MH and50phrDBOPE.The heat extension test indicated that samples could be crosslinked byUV irradiation. The degree of crosslinking increased with increasing theDBOPE content. The results of mechanical test show that the photocrosslinkedhave better mechanical propertiesm than unphotocrosslinked samples. Thelimiting oxygen index and UL-94vertical combustion level showed that thecorresponding LOI values decrease about2％after UV irradiation while theleval of vertical combustion were unchanged. |
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