Wheat straw was liquefied in the mixture of polyethylene glycol (PEG 400) and glycerin in the presence of acid at the temperature 130-160 C. The final liquefaction products having the hydroxyl number of 250-430 mg KOH/g and the M n of about 1050 can be used as the polyol component to manufacture polyurethane. A kind of polyurethane foam was prepared from liquefied wheat straw, commercial polyol, and diisocyanates in the presence of organotin catalysts and foaming agents. The polyurethane foam presented better compressive strength and thermal stability than that manufactured from diisocyanate and polyol alone. The thermal stability of PU foam was improved with the increase of [NCO]/[OH] ratio and the addition of liquefied wheat straw. The polyurethane foam presented faster biodegradation at ambient temperature than normal polyurethane foam did.

A series of biodegradable plastics from soy protein isolate (SPI) and lignosulfonate (LS) with a weight ratio of 0:10 to 6:4 were prepared with 40 wt % glycerol as a plasticizer by compression molding. Their properties were investigated by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamical mechanical thermal analysis (DMTA), scanning electron microscopy (SEM), and tensile tests. The results indicated that the introduction of a moderate LS content from 30 to 40 parts in the blends could simultaneously enhance the tensile strength, elongation, and Young's modulus of soy protein plastics alone. Studies of the water sensitivity of the materials suggested that the strong interaction between LS and SPI could restrict the effect of water on the swelling and the damage of the materials, resulting in lower water absorption. The improvement of the properties was attributed mainly to the existence of the beneficial microphase separation and the formation of crosslinked structures because of the introduction of LS into soy protein plastics. Therefore, a model of a crosslinked network formed from SPI molecules with an LS center was established based on the existence of strong physical interactions between LS and SPI.

The color of lignin was obviously reduced via a chemical-reaction-free fractionation using methanol/water as a solvent.

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