Agriculture Reference
In-Depth Information
Figure 2. Summary of modification of NR via chemical modification, blending and the addition of a
chemical agent.
The three forms of NR that have been used for modifications include latex (Riyajan et al.,
2012a), solution (Nakason et al., 2004) and melt (Xavie et al., 2001). Compared to
modifications in solution, the modification in melt is more advantageous in terms of energy
savings and the environment. However, the disadvantages of chemical modification in the
melt form are the possibilities of an easy side reaction, because of the heterogeneous
properties of modified rubber. In addition, the investigations with regard to modification in
form have been carried out using brabender-type internal mixers, a two-roll mill, a single-
screw extruder and a twin-screw extruder. Recently, modifications to its latex form have been
widely used for improving the properties of rubber owing to the friendly environment, high
productivity and an available process such as a dipping process. Water is no doubt the most
environmentally friendly solvent. When modification is carried out in the latex form, the
process of modification of the properties of NR would be much more efficient due to there
being no use of organic materials. Thus, modification in the latex phase is attractive.
However, its usage in the organic reaction processes has limitations because many organic
materials do not dissolve in water. In addition, many reactive intermediates and catalysts are
decomposed by water. This is the case for Lewis acid catalyzed reactions, which are of great
current interest because of their unique creativities and selectivity and it can be achieved
using mild conditions (Hayashi et al., 2011).
Prevulcanizsation
Vulcanization is a chemical modification of NR that converts natural rubber or related
polymers into a more durable material by using curing agents e.g., sulfur, peroxide and other
chemicals (Datta et al., 2007). These curing agents modify the NR molecule by forming
crosslinks (bridges) between individual NR chains as shown in Figure 3. The outstanding
property of vulcanized NR is that it is less sticky, operates well in any outdoor environment
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