| For above one hundred years . the nature forests have been felled on a large scale . On the one hand , the existent natural resource of timber forest is on verge of exhaustion . And there have been soil erosion , desertification . shortage of water resources, the frequent disaster of flood and drought, warming weather on the earth , ecological balance fast broken and so on . On the other hand , the demand for industrial wood is facing an supply severely deficit . In order to protect forests , to improve ecological environment and to maintain ecological balance . almost all countries have done something to prohibit the nature forests form felling . The project of the nature forests has been in China since August, 1998 . However , after the nature forests were kept form cutting , the supply of prime , big diameter-class logs , mature wood and over adult wood has been fastly lower . Otherwise , small diameter-class log , wrack , under mature wood and juvenile wood of industrial plantation come to take the place of timber of the nature forests for all kind of wood products quantitatively . Because the man-made forest raw maters has qualities of high proportion of juvenile wood , low mechanical properties of wood , easily spitting in timber seasoning , easily erosion of sapwood and bad permeability of heart wood . milling and utilization system of them is not same as that of timber of the nature forests . So there are plenty of problems in reasonable and scientific utilization of plantation forest. To improve defective log , to the most efficiently utilize and enhance the cost of wood of fast growth industrial plantation and to lengthen the lives of the products , the wood processing and utilizing science and techniques are still studied further . If wood of fast growth industrial plantation is reconstituted , reinforced, softened, plasticized , bleached , stained , treated by decay resistance agent and fire retardant agent and so on , it can have the same good feathers as prime . That means plantation forest plays an important and basic role in maintenance of ecological balance and in assuage the wood deficiency in the world .There are many native pine trees -P. massonicma Lamb. , P. armandi Francha. and P. yunnanensis Franch. in the south of China and Larix gmeiinil Rupr., P. Kerajensis Sieb, et Zucc. And P. sylvestris Var. mongolica Litven. in the north. The number of wood of plantation is very much big . However. there is too much pine oleoresin in pine wood . When the products are used for long or in high temperature , rosin with turpentine oil bleeds through and will make them blistering , paint film flaking , staining paint film and clothing and adhering hands . On the other hand , pine oleoresin embarrasses water to bleed though by gas from in wood . Namely , the blockage water and steam passages by resin in the timber is reason why pine wood is difficult to dry and easy to crack Then pine wood has high ratio of T to R shrinkage and bad dimensional stability . So improving properties of pine wood is necessary and important . Since 1980s , wood industries . forestary institutes and universities in China have studied properties and utilization science and technology of, wood of many pine species . Five deresination methods -saponification , solvent seasoning , pine oleoresin polymerization reaction . high temperature drying and vacuum drying were used in wood industry . But the methods are not still accepted by the market in China mainly because are too expensive and not satisfactry effectiveness of deresination . In a word , deresination methods need further study and invention .After the test are done for two years . further studying and inventing deresination methods has been accomplished completely . the satisfactory effectiveness of deresination and the desirablecost have been reasonably and successfully combined. Under centralized guidance of the technologists and professors in Central South Forestary University , I have broken old deresination theory in a sense . Depriving resin from pi... |
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