Preliminary Ecology Study On The Community Of Native Metasequoia Glyptostroboides In Lichuan City

The petroleum resources are being exhausted gradually, and the problem of environmental pollution from the waster and litter of nondegradable polymer materials that are mainly derived from petroleum resources becomes more and more serious. Therefore, polymer science and technology, face new challenge. Nowdays, research and exploitation of new materials based on naturalpolymers have become the front of polymer science. Konjac Glucomannan (KGM) is the main content of the local resource Konjac as a kind of natural polymer. KGM has the similar structure to cellulose, but has the water solubility that is not embodied by cellulose. The abundant hydroxyl groups in KGM molecules are high active, and it contains certain amount of acetyl groups, so that KGM is ease to be chemically modified by green technology. The main research contents and conclusions are as follow:1. KGM with good water solubility has been isolated from Konjac flour, through defatting, deprotein, decolor, ultracentrifuge, precipitation etc.2. In esterification and crosslinking modification of Konjac Glucomannan with sodium pyrophosphate ( Na₄P₂O₇, SPP ), best results were obtained in the following conditions: SPP:KGM=l:8(w/w), pH =3, reaction temperature 50°C, and reaction time 2h. Modified KGM was shown to be superior to the raw Konjac Glucomannan in viscosity, transparency, freeze-thaw stability and fungistasis. Resisting water rush ability of modified film was obviously improved.3. Konjac Glucomannan was deacetyl for membranes. The membranes made from denatured KGM showed better tensile strength, water resistance and resisting water rush than that from undenatured KGM. By means of infrared absorption spectroscopy , X-ray diffraction, the relationship of structures and functional properties was discussed. Studies on the conservation of tomatoes by pure KGM membrane and modified KGM membrane were carried out under room temperature. The results showed that modified Konjac Glucomannan membrane had better fresh-keeping affection on tomatoes.4. Konjac Glucomannan and Guaran gum were blended for membranes. There were excelent properties while the blend content was 1%(wt) and the mixed ratio of KGM and Guran gum was 60/40. The blend membranes showed better properties in tensile strength, water resistance, resisting water rush and transparency index than that of pure KGM membrane. By means of infrared absorption spectroscopy and scanning electron microscope, the relationship of structures and functional properties was discussed. Studies on the conservation of grapes by pure KGM membrane and blend membranes were carried out under room temperature. The results showed that blend membranes had better fresh-keeping affection on grapes.5. Konjac Glucomannan is not gelation polysaccharide. It can get gelation when Gellan gum and KGM are mixed by some ratio. This is the synergistic interaction result of polysaccharide s molecules. There was synergistic interaction maximum while the mixed ratio of KGM and Gellan gum was 40/60, the total polysaccharide concentration 1.0%(wt), reaction temperature 80 ℃ and salt ionic (Ca ²+)concentration 6.0mmol/L Interraction machanism of two polysaccharide molecules was investigated by infrared absorption spectroscopy.6. (NH₄)₂Ce(NO₃)₆ initiated graft copolymerization of N, N-diethylenediacrylam-ide onto Konjac Glucomannan and the action rule was studied. This copolymer was easy to dissolve in water. The solution had higher viscosity. Therefore, the copolymer was a good thickener in industries.