Sulfur, lignin

The synthesis of sulfur lignin is relatively simple, and on a large scale its preparation becomes less expensive than the preparation of synthetic polymers currently used in the semiconductor industry. 

The thermal degradation of lignin occurs over a wide temperature range, from about 420-773 K. Several practical ways exist for the preparation of sulfur lignin. These are summarized in Table I. 

Table I. Some of the methods to prepare sulfur lignin at the temperature of 473-513 K...

Synthesis conditions and analytical results (Table II) are consistent with the hypothetical structures of sulfur lignin shown in Figure 2. Sulfur lignin is an aromatic thioether and it resembles polyphenylene sulfide derivatives (8). 

Figure 2. The reaction and possible structures of sulfur lignin.

Conductivity Sulfur lignin can be made conducting by compounding and by doping... 

Conductivities of sulfur lignin (SL), sodium lignosulfonate (NaLS), and some common materials are represented in Table III. 

Polyaromatic sodium lignosulfonate and sulfur lignin resin can be made conducting by doping. The conductivity increases by several decades through doping with electron acceptors and donors as shown in Table IV. 

We have doped sulfur lignin and sodium lignosulfonate in vapor-phase (iodine, bromine, and ammonia) and in liquid phase (sodium and ferrichlo-ride). The conductivity mainly depends on the nature of the dopant ion and the doping degree. Doping can be monitored by IR-spectroscopy. The intensities of the peaks decrease, and the fine structure vanishes, when the... 

Table IV. Conductivities of sodium lignosulfonate (NaLS) and sulfur lignin (SL) with some dopants ...

Table V. A/B-ratios of sulfur lignin doped with bromine...

The effect of doping sulfur lignin with bromine on the IR spectra is shown in Figure 3a and 3b. 

A new series of sulfur lignin-graphite samples with known graphite content were treated with bromine in the vapor phase (doped). After measuring the conductivities, we recorded the curve shown in Figure 4b (Kuusela, T. A., The University of Helsinki, Finland, to be published). 

Figure 3. a, the effect of doping degree on IR spectra (bromine) b, ESR-spectra of sulfur lignin doped with bromine. 

When sodium lignosulfonate or sulfur lignin are compounded, for instance, with iodine or bromine, complexes supposedly form (16-17). These systems are conductors with mixed ionic and electronic nature. Presumably they are charge transfer complexes, since the electronic conductivity predominates (18-19). These compounded materials form charge transfer structures (20). Water is supposed to introduce ionic conductivity to the system. Impurities affect conductivity, too (21). In any case, the main models of conductivity are probably based on the band model and/or the hopping model. 

Figure 4. Compounding sulfur lignin with graphite (a) and with graphite and bromine (b).

Chemical modifiers Sulfur, lignin and certain organo-metallic compounds (2), (5), (6), [8], [9], [12]... 

The chemical modifiers, such as sulfur, lignin and certain organo-metallic compounds, do not really modify the bitumen but, rather, the properties of the asphalt mixture. The sulfur or the lignin extend the properties of the bitumen and modify the properties of the asphalt. Hence, the sulfur and the lignin are called bitumen extenders. The organo-metallic compounds modify the asphalt mixture by their catalytic action. 

Spent Acid Sulfuric Lignin Crude Tall Oil, pH 3. ... 

Sulfur lignin is a totally amorphous material Amorphous structure, particle sizes are between 1000-40000 nm Sulfur content in samples from different experiments varies between 10-26 mass-% Stable sulfur linkages between the aromatic units are formed... 

Material is nearly completely desulfonated Material is demethoxylated and the propyl group is split off. Polymer is branched. Sulfur lignin can be made conducting by compounding and by doping Paramagnetic structures and radicals are found... 

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