128
7 Rubber Reinforcement with Lignin
mixing of lignin powder into solid NR is not so much as expected by many rubber
engineers. The soft process introduced in Chap. 6 is on in situ silica, namely using
the sol–gel reaction involving TEOS (liquid) at the rubber processing step for filler
introduction. In the present soft process involving lignin, lignin is used as a solution.
For the industrialization of this soft process, the coagulation of NR latex on addition of lignin alkaline solution has to be avoided perfectly by adjusting the mixing
conditions. Also, the liquid state is to be maintained by the mixing with the curing reagents. However, the soft process in general may enable us to establish a new
energy-saving simple process. There may have been very similar projects even within
rubber arena. For example, epoxy NR or SBR was reported to be mixed with organic
clay in solution state, which was a candidate for tire rubbers [44]. The development
of various soft processing methods of rubber is an increasingly urgent issue for the
worldwide rubber industries.
7.3 Lignin as Reinforcing Filler for Soft Biocomposite
The lignin/NR soft biocomposites, prepared by the soft process shown in Fig. 7.3,
are subjected to morphological and tensile studies, the results of which are described
in this section. All the specimens were cross-linked by a sulfur/accelerator system
shown in Table 7.1, specifically used in NR latex vulcanization [14, 42, 43, 45].
Figure 7.4 shows a conventional TEM image of the composite containing 10 phr of
lignin (NR-L0-S-soft) [43], and Fig. 7.5 displays phase and height images of scanning
Fig. 7.4 Conventional TEM
image of NR-L10-S-soft
(from Fig. 3 in Ref. [43])
7 Rubber Reinforcement with Lignin
mixing of lignin powder into solid NR is not so much as expected by many rubber
engineers. The soft process introduced in Chap. 6 is on in situ silica, namely using
the sol–gel reaction involving TEOS (liquid) at the rubber processing step for filler
introduction. In the present soft process involving lignin, lignin is used as a solution.
For the industrialization of this soft process, the coagulation of NR latex on addition of lignin alkaline solution has to be avoided perfectly by adjusting the mixing
conditions. Also, the liquid state is to be maintained by the mixing with the curing reagents. However, the soft process in general may enable us to establish a new
energy-saving simple process. There may have been very similar projects even within
rubber arena. For example, epoxy NR or SBR was reported to be mixed with organic
clay in solution state, which was a candidate for tire rubbers [44]. The development
of various soft processing methods of rubber is an increasingly urgent issue for the
worldwide rubber industries.
7.3 Lignin as Reinforcing Filler for Soft Biocomposite
The lignin/NR soft biocomposites, prepared by the soft process shown in Fig. 7.3,
are subjected to morphological and tensile studies, the results of which are described
in this section. All the specimens were cross-linked by a sulfur/accelerator system
shown in Table 7.1, specifically used in NR latex vulcanization [14, 42, 43, 45].
Figure 7.4 shows a conventional TEM image of the composite containing 10 phr of
lignin (NR-L0-S-soft) [43], and Fig. 7.5 displays phase and height images of scanning
Fig. 7.4 Conventional TEM
image of NR-L10-S-soft
(from Fig. 3 in Ref. [43])