Evaluation of Electron Induced Crosslinking of Masticated Natural Rubber at Different Temperatures

Abstract

In this work, natural rubber (NR) was masticated using an internal mixer to fit the requirements of reactive blending with polylactide and characterized by size exclusion chromatography (SEC), Fourier-transform infrared (FT-IR) spectroscopy and dynamic rheology measurements. Subsequently, the effect of elevated temperatures (25 °C, 80 °C, and 170 °C) on the electron beam (EB) induced crosslinking and degradation of masticated natural rubber (mNR) in a nitrogen atmosphere without adding crosslinking agents has been investigated. The sol gel investigation showed that the gel dose of mNR slightly increased with increasing irradiation temperature, which is also confirmed by the swelling test. The chain scission to crosslinking ratio (Gs/Gx) was found to be less than 1 for irradiated mNR at 25 °C and 80 °C, suggesting a dominating crosslinking behavior of mNR. However, a significant increase of Gs/Gx ratio (~1.12) was observed for mNR irradiated at 170 °C due to the enhanced thermal degradation behavior at high temperature. A remarkably improved elasticity (higher complex viscosity, higher storage modulus, and longer relaxation time) for EB modified mNR was demonstrated by dynamic rheological analysis. Particularly, the samples modified at higher temperatures represented more pronounced elasticity behavior which resulted from the higher number of branches and/or the longer branched chains.

The effects of the cross‐linking mechanism of low doses of gamma irradiation on the mechanical, thermal, and viscoelastic properties of the natural rubber latex/poly(styrene‐block‐isoprene‐block‐styrene) block copolymer blend

“…This solid‐like behavior has also been reported in other cross‐linked polymer systems. [ 41,63 ] The plot of the loss factor tan δ ( G ′′/ G ′) against ω is given in Figure 6D. The neat NRL and unirradiated 70 NRL /30 SIS blend show a rising hump of tan δ and continuous decline at higher frequencies.…”

“…[20,38,40] The swelling analysis provides information to measure the gel content and cross-link density using the Flory-Rehner equation. [41] The unirradiated 70 NRL /30 SIS blend gives gel content and cross-link density of 10.73% and 4.2 Â 10 À5 molÁcm À3 , respectively, as is shown in Figure 4C. As in the result of gel content, the 70 NRL /30 SIS blend is immersed in toluene, in which the SIS is soluble in toluene due to their close solubility parameter (PS = 17.6, PI = 17.4, and toluene = 18.0 MPa 1/2 ).…”

Electron Beam Irradiation: A Method for Degradation of Composites Based on Natural Rubber and Plasticized Starch

“…Two absorption bands characteristic of natural rubber can be observed in the region 1500-1300 cm −1 : the first one due to the -CH 2 deformation between 1448-1444 cm −1 and the second one due to the -CH 3 asymmetric deformation between 1376-1374 cm −1 [67]. These bands' modifications are more pregnant in the case of C10 and C50 and less for the C0 sample.…”

“…Absorptions that can be observed in the regions 1242-1239 cm −1 and 1154-1148 cm −1 can be attributed to the presence of some impurities in NR as proteins, lipids, amino acids and unstable peptides that can also be degraded by EB irradiation [67][68][69].…”

Degradation by Electron Beam Irradiation of Some Composites Based on Natural Rubber Reinforced with Mineral and Organic Fillers

“…Bands attributed to -C=C-stretching vibration in the NR structure, to hydroxyl stretching vibrations of absorbed water and to carboxylate or conjugated ketone (>C=O) that are oxidative products derived from degradation, were found between at 1658-1647 cm −1 and 1655-1651 cm −1 [18,71,76]. Bands that correspond to symmetric and asymmetric deformations of -CH 2 and CH 3 from natural rubber have been found at 1448-1445 cm −1 and 1376-1375 cm −1 , respectively [18,77]. The modification of these bands due to irradiation shows that the degradation of composite materials also occurs through the oxidation of methyl terminal groups with the formation of degradation products such as the for-mation of carboxylic acid derivatives group, the hydration of double bond to tertiary alcohol (aldehyde and ketones) and the cleavage of the internal bond resulting in polymeric molecular chain breakage [74,78,79].…”