Study On Machining And Painting Properties For Three Kinds Of Plantation Wood Of Guangxi

In order to reveal the machining and painting properties of Toona sinensis, Michelia macclurei Dandy and Taiwania cryptomerioides plantation wood to provide theory and technology for the high-value utilization of their solid wood, testing for six kinds of machining properties (including planning, sanding, shaping, boring, mortising, turning) was carried out based on the standard ASTM D1666-87. Surface roughness, primer coating amount, face paint coating amount and setting time as influence factor, four factors and four levels orthogonal test, and variance analysis method and the integrated balance method for test result was adopted to study the five kinds of painting properties (including film adhesion, abrasion resistance, impact resistance, color changes on the wood surface, glossiness changes). Of which, the influence of surface roughness on the surface contact angle, and relation between the contact angle and painting properties was also focused. More over, SEM was applied to analysis the microstructure of bonding interface between coating layer and wood surface. The sdudy shows:1?In the machining performance comprehensive evaluation system for full marks 50 points, Toona sinensis wood was 43.4 points as well as Michelia macclurei Dandy as 41.8 points and Taiwania cryptomerioides as 42.9 points, which indicate the three kinds of wood have a good machining properties.2?The machining roperties of Toona sinensis, Michelia macclurei Dandy, Taiwania cryptomerioides show excellent in planning, sanding, shaping and turning, then the boring property shows good. The mortising property of Toona sinensis and Taiwania cryptomerioides shows good, while Michelia macclurei Dandy is medium.3?150# sand band is applied on Toona sinensis and Michelia macclurei Dandy,which have two minimum contact angles with water that respectively are 53.65° and 53.65°;240# sand band is used on Taiwania cryptomerioides, while its minimum contact angle with water is 42.94°.4?After polyurethane varnish and waterborne wood coatings are finished on Toona sinensis, Michelia macclurei Dandy and Taiwania cryptomerioides wood surface, all physical properties of coating are almost same, Michelia macclurei Dandy> Toona sinensis> Taiwania cryptomerioides on the film adhesion. The film adhesion is associated with the reaction extent of the paint and wood surface,whose surface bonding degree is higher and the film adhesion is better.The painting properties of Toona sinensis and Taiwania cryptomerioides coated with polyurethane varnish show grade 2, the affected areas are respectively 6.73% and 12.78%, while Michelia macclurei Dandy which has affected area of 4.95% show grade 1. Then the painting properties of Toona sinensis and Michelia macclurei Dandy coated with waterborne wood coatings show grade 2, the affected areas of them are respectively 7.82% and 6.94%, while Taiwania cryptomerioides show grade 3, which has affected area of 17.83%. However, there are not obvious differences on the abrasion resistance among the woods. In terms of the impact resistance, Michelia macclurei Dandy is the best, while Taiwania cryptomerioides is the worst. Consequently, conclusions based on the best technology process:Michelia macclurei Dandy consumes the minimum amount of primer coating and face paint coating as well as the the shortest curing time of paint film, and shows the best physical properties of the paint film. Toona sinensis takes the second place. However, Taiwania cryptomerioides consumes the maximum amount of primer coating and face paint coating, and takes much longer curing time. Therefore, Michelia macclurei Dandy wood has better painting performance than Toona sinensis and Taiwania cryptomerioides.5?L* value of test materials decreases, while the b* value increases, and the yellowish features of wood was strengthened after the surface was painted with different alkyd varnish. Of which, the polyurethane varnish enhances the reddish features of wood, but waterborne wood coatings reduce Toona sinensis and Taiwania cryptomerioides reddish features.6?Glossiness of wood surface was significantly improved by painting with alkyd varnish. Especially, after painted with polyurethane varnish, the glossiness along the parallel texture direction can reach the light level, while the glossiness along parallel texture direction can reach the matte level after painted with waterborne wood coatings.