The Research Of Preprocessing And Dyring Characteristics Of B.costata Disk

The tree disk, which is cross cut from a log, for making wood artifacts and material for home-decorating, is a wood product with unique aesthetics character and artistic value, and also is one way to effectively utilize wood(especially crooked wood, small-diameter log etc.). to improve timber unit economic benefit and additional value. However, disk drying is much more difficult than drying lumber because of severe check problems. Therefore it's necessary to research the problem of disk drying. The thesis with resourceful B.costata of Northeast China Region as the object of study, put forward research method of special drying and preprocessing of disk, systematically researched drying properties of RF/V, the influence of preprocessing for conventional drying properties and drying cost, the mechanism of restrained cracking of disk. It's first time to research the application of NaCl. to introducing "dual cooperation thought" to solve deficiency in in preprocessing of disk. The thesis researched mechanism of action between preprocessing chemicals and wood by SEM. FTIR and XRD instrument. The main research contents were as follows:(1) Through the analysis of experimental results and unique features of disk, put forward the cracking potential of disk and the model about drying strain of disk in circumference direction, which indicated that drying strain depends on disk radius and difference of drying shrinkage in circumference and radial direction.Put forward the relational model between drying stress and radial shrinkage. which indicated that:drying stress closed related with the ratio of restrained shrinkage and free shrinkage in radial direction.When disk radius is unchanged. the relationship between drying strain and difference of drying shrinkage in circumference and radial direction has positive correlation. therefore put forward difference of drying shrinkage as the cracking potential of disk. The correctness of the models had been confirmed through drying experiments.(2) Dependding on disk characteristic, the thesis first put forward low-temperature intermittent drying method, which could ensure the drying quality of disk; and then researched when the cracks produced and changed in rapid drying schedule, finally raised "rapid-low temperature intermittent combinated drying" to obviously shorten drying period.(3) Drying quality and efficiency of disk were satisfactory, the reducing of MC gradient and'cracking potential'restrained the cracking of disk in RF/V. The mechanism of restrained cracking in RF/V was analysed by the model, which describes the relationship between drying shrinkage and resultant force inside and outside cell wall.(3) The thesis put forward to processing B.costata disk with NaCI and PEG400, which are pollution-free, non-toxic for people, livestock and environment, are suitable for processing of green wood. The thesis analysed the influence of preprocessing factor for physical properties and the influence of preprocessing for radial change trend of physical property in wood. All of the work provided basic for analyzing the reason of restrained cracking.(5) The thesis analysed dyring character of preprocessing disk by the model of existential state of chemicals and hydrone in micro-capillary. Preprocessing obviously shortened drying period, especially processing by PEG400. The analysis indicated that reducing of 'cracking potential' was the main reason to restrain the cracking of disk, which also confirmed that model about drying strain of disk in circumference direction was right. The analysis of compound mechanism between processing chemicals and wood by SEM. XRD and FTIR showed:NaCI could enter the amorphous region of cellulose and combined with free hydroxyl by hydrogen bonding; a PEG400 mainly mechanically deposited in wood, it also explained the influence of preprocessing for tensile strength and drying rate.(6) The thesis introduced dual cooperative processing of NaCI/SiO2 to resolve the deficiency of higher avsorb moisture of disk processing by NaCI. The synergy of NaCI/SiO2 was realized by using the methods of controlled low-temperature hydro therman and sol-gel. The analysis of SEM, XRD and FTIR showed:the first method reduced hygroscopic by change of crystal morphology of NaCI, the second method reduced hygroscopic by cover of SiO2 for NaCI(7) The thesis analysised drying cost from current assets, fixed assets, drying period, scope of application and drying quality. The results showed:the drying cost by processing of NaCI was lowest, and then PEG400, the preprocessing has advantages for example:drying cycle is shortest, drying quality is best, scope of application is wide, therefore, preprocessing was the best method for disk drying. Drying methord in RF/V was taked second place. The last was united drying and intermittent low temperature drying, which has shortage for example:drying cycle is longest; it was only suitable in small diameter disk. Therefore we should pertinently choose suitable drying methord of disk according to actual demand and characteristic of preprocessing and drying methord.