Characterization of the UV Oxidation of Raw Natural Rubber Thin Film Using Image and FT-IR Analysis

Abstract

Characterization of the UV oxidation for raw natural rubber (NR) was investigated in controlled conditions through image and FT-IR analysis. The UV oxidation was performed on a thin film of natural rubber coated on a KBr window at 254 nm and room temperature to exclude the thermal oxidation. Before or after exposure to UV light, image of the NR thin film was observed at a right or tilted angle. FT-IR absorption spectra were measured in transmission mode with the UV irradiation time. The UV oxidation of NR was examined by the changes of absorption peaks at 3425, 1717, 1084, 1477, 1377, and 833 cm −1 which were assigned to hydroxyl group (-OH), carbonyl group (-C=O), carbon-oxygen bond (-C-O), methylene group (-CH 2 -), methyl group (-CH 3 ), and cis-methine group (cis-CCH 3 =CH-), respectively. During the initial exposure period, the results indicated that the appearance of carbonyl group was directly related to the reduction of cis-methine group containing carbon-carbon double bond (-C=C-). Most of aldehydes or ketones from carbon-carbon double bonds were formed very fast by chain scission. A lot of long wide cracks with one orientation at regular intervals which resulted in consecutive chain scission were observed by image analysis. During all exposure periods, on the other hand, it was considered that the continuous increment of hydroxyl and carbonyl group was closely related to the decrement of methylene and methyl group in the allylic position. Therefore, two possible mechanisms for the UV oxidation of NR were suggested.

Degradation Studies Realized on Natural Rubber and Plasticized Potato Starch Based Eco-Composites Obtained by Peroxide Cross-Linking

“…After degradation, the spectra indicate that the intensity of the broad bend near 3380 cm −1 has increases. The broad band at 3380 cm −1 may be due formation of hydroxyl group (–OH) as a result of the degradation by oxidation [ 38 , 42 ]. It can be seen that after 1 year of natural ageing in temperate climate, all these bands have increased in intensity.…”

Latex balloons do not degrade uniformly in freshwater, marine and composting environments

“…This type of rubber has a crystalline structure that enables it to have high tensile strength and hardness 45 , which may contribute to its ability to persist in the environment. Overall, all latex balloons' spectra were similar to spectra of pure latex 44,46 , except for extra peaks observed between 1300-1000 cm -1 (C-O stretching region) that could indicate the presence of alcohols or starches 39 . Indeed, various fibers are used as fillers in latex balloons 24 .…”

“…Photo-oxidation causes chain scission and bond cleavage, which generate free radicals and break up the latex polymer backbone and consequently decrease elasticity 41,56 . UV additionally generates free radicals that break functional groups along the backbone 46,56 . These changes manifest as the formation of new groups (e.g.…”

Aging studies of a polypropylene and natural rubber blend

“…The presence of impurities able of absorbing UV will increase the degradation phenomena. UV irradiation of natural rubber induces various volatile degradation products such as ketones, aldehydes and organic acids [30]. The presence of tertiary carbon in the main chain of isotactic polypropylene is the reason of its great sensitivity to UV rays [30].…”

“…UV irradiation of natural rubber induces various volatile degradation products such as ketones, aldehydes and organic acids [30]. The presence of tertiary carbon in the main chain of isotactic polypropylene is the reason of its great sensitivity to UV rays [30]. Degradation reactions of semicrystalline polymers occur mainly in the amorphous regions; however, morphology parameters, such as the arrangement, size and distribution of the crystalline zones, influence highly the degradation mechanism [31,32].…”