Hydroxyl-Terminated Saponified Natural Rubber Based on the H2O2/P25-TiO2 Powder/UVC-Irradiation System

Natural rubber (NR), a long-chain hydrocarbon polymer mostly consisting of cis-1,4-polyisoprene units, has a high molecular weight (MW) and viscosity, enabling it to show excellent physical properties. However, NR has no reactive functional group, making it difficult to react with other molecules, especially in manufacturing processes. The functionalized low-molecular-weight NR (FLNR) is a requirement to disperse ingredients into the rubber adequately. Here, the FLNR was prepared by a photochemical degradation process under UVC-irradiation in the presence of H2O2 using P25-titanium oxide (TiO2) powder as a photocatalyst. The optimum condition for the preparation of FLNR was the use of 2.0 g of TiO2 powder per 100 g of rubber and H2O2 at 20% w/w under UVC-irradiation for 5 h. The hydroxyl groups were found on the NR chains due to the chain-scission of polyisoprene chains and hydroxyl radicals in the system. The weight average MW of NR decreased from 12.6 × 105 to 0.6 × 105 gmol−1, while the number average MW decreased from 3.3 × 105 to 0.1 × 105 gmol−1

Green composite sponge of natural rubber reinforced with cellulose filler using alginate as a dispersing agent

Composite sponges of natural rubber and cellulose fiber (NR-C) using sodium alginate (SA) as a dispersing agent were successfully fabricated by the Dunlop process. The aim of this work was to develop a green composite NR-C sponge with high mechanical properties and efficient water absorption capacity (WAC). The addition of SA could promote cellulose fiber dispersion in NR matrix and NR-cellulose interactions; accordingly, it resulted in highly macro-porous sponges with improved mechanical properties and higher hydrophilicity. NR-C sponge supplemented with cellulose at 45 parts per hundred rubbers (phr) and SA at 1 phr revealed significantly higher compressive stress and higher modulus of elasticity of about 5 times those of NR sponge. The maximum WAC at around 400 % was obtained from NR-C sponge supplemented with 30–45 phr cellulose and 1 phr SA. The initial water absorption rate and WAC of NR-C sponges were increased up to 5.6 and 1.8 times those of NR sponges, respectively. In addition, NR-C reinforced with high content of cellulose and SA could be sufficiently biodegraded in soil for about 21–27 % in120 days, which was considerably higher than that of NR sponges. According to their improved properties, NR-C composite sponges could be used an adsorbent or supporting material in many applications, including agriculture applications, such as a seed germination sponge or a hydroponic planting material and could also be further developed for biomedical applications as wound dressing

The majority of minerals present in natural rubber are associated with the macrogel: An ICP-MS and SEM/EDX investigation

International audienceThe mineral composition of the insoluble (macrogel) and soluble fractions of two natural rubber (NR) samples made from the latex of two different clones (RRIM600 from Thailand and GT1 from Côte d'Ivoire) was determined using inductively coupled plasma mass spectrometry (ICP‐MS). The ICP‐MS results showed that mineral elements were concentrated in the macrogel. The major mineral elements found in macrogel were phosphorus, magnesium, potassium, and sulfur. Some mineral elements were mostly concentrated in micron‐sized mineral aggregates, visible at the surface of the samples using scanning electron microscopy coupled with an energy dispersive X‐ray microanalyzer (SEM/EDX). The nature of these mineral aggregates was found to be highly variable. Their inhomogeneous distribution in the macrogel indicates that these aggregates do not have a major influence on macrogel structure