Plywood Made from Plasma-Treated Veneers: Investigation of Performance Differences between Plasma-Pretreated and Untreated Beech Veneers at Comparable Melamine Resin Load

In this study, the dimensional stability and mechanical properties of plywood made from untreated and plasma-pretreated beech veneers were compared. The wood veneers used (native and thermally modified) were impregnated with melamine resin in a simple dipping process prior to plywood production. The duration of the impregnation process was adjusted to give the same melamine resin loading for the different veneer types, with the plasma-pretreated veneers requiring only a fraction of the impregnation time compared with non-plasma-pretreated veneers. With comparable melamine loading, testing of the mechanical properties of the plywood for the different specimen collectives showed significant differences in some cases with respect to compressive strength, bending strength and tensile strength (with the associated moduli of elasticity). For example, it was shown that plywood made from plasma-pretreated native beech veneers shows an increase in bending strength of about 8%, and from plasma-pretreated and thermally modified beech veneers, there is an increase of about 10% compared to the reference.

A Study of Ralex Membrane Morphology by SEM

A comparative analysis of the effect of the manufacturing technology of heterogeneousion-exchange membranes Ralex CM Pes manufactured by MEGA a.s. (Czech Republic) on the structural properties of their surface and cross section by SEM was carried out. The CM Pes membrane is a composite of a sulfonated ion-exchanger with inert binder of polyethylene and reinforcing polyester fiber. In the manufacture of membranes Ralex the influence of two factors was investigated. First, the time of ion-exchange grain millingvaried at a constant resin/polyethylene ratio. Second, the ratio of the cation-exchanger and the inert binder of polyethylene varied. It has been found that the membrane surface becomes more electrically homogeneous with the growth of the ion-exchanger loading and a decrease in its particle size. With an increase in the milling time of resin grainsfrom 5 to 80 min a more than 1.5-fold decrease in their radius and in the distance between them was revealed.Besides, there is a 1.5-fold decrease in the fraction, as well as in the size of pores and structure defects. The fraction of the ion-exchange phase on the membrane surface decreases by 7%. With an increase in the resin loading from 45 to 70 wt %, the growth of the fraction of conducting regions on the surface is almost twofold, while their sizes remain practically unchanged. More significant changes in the surface structure of the studied membranes are established in comparison with the cross section. An increase in the resin content in the membranes from 45 to 70 wt % corresponds to a 43% increment of its fraction on the cross-section.The increase in the ion-exchanger content of Ralex membranes is accompanied by the growth of the fraction of macropores and structure defects on the membrane surface by 70% and a twofold decrease in the distance between conducting zones.

Water Related Properties of Birch Wood Modified with Phenol-Formaldehyde (PF) Resins

In this study, Silver birch (Betula pendula) wood veneers and solid wood blocks were treated with commercial phenol-formaldehyde (PF) resin water solutions. Birch veneers and solid wood blocks of different size were impregnated with PF resin solutions in water with concentrations of 10, 20 and 30 wt%. The weight percent gain (WPG) and bulking after drying and curing of resin treated wood specimens were determined to evaluate the impact of specimen sizes and density. The leaching procedure according to EN 84 was performed to evaluate the PF resin fixation stability. The anti-swelling efficiency (ASE) of untreated and treated specimens during seven soaking-drying cycles was examined. Higher WPG values were obtained for specimens with lower density, but no correlation was found between the specimen size and WPG. The WPG of veneers and solid wood was 8.7 - 17.7% and 8.5 - 24.4%, respectively. The ASE of wood blocks treated with PF resins after the 1st cycle was in the range of 37 - 51% depending on the resin loading in the wood. However, the ASE values decreased after every next soaking-drying cycle, reaching 33 - 48% after the 7th cycle. After leaching, the WPG of specimens decreased by 2.3 - 3.0%.

Preparation and Characterization of Levalbuterol Hydrochloride Drug-Resin

In this study, our objective was to prepare levalbuterol hydrochloride drug-resin and investigate its characteristics. This work is basis for the study of the next levalbuterol hydrochloride sustained-release suspensions. The drug-resin was prepared by bath method. The effect of factors , including resin types, drug concentration, speed, temperatures and pH on evaluation index, was evaluate by Drug utilization rate and the resin loading. Then the Box-Behnken Design-response surface method was used to optimize the preparation. The drug content determined by UV method and drug-resin were characterize by IR and DSC．The best formulation of levalbuterol hydrochloride drug-resin was used the bath method IRP69 resin at 30°C. The drug concentration was 1.8 mg•ml-1, and the rotate speed was 250 rpm, the pH was 5.8. The preparation of levalbuterol hydrochloride drug-resin method is simple and feasible, and the drug combined with the resin by the chemisorption of ionic bond.

Mechanical and Electrical Properties of Graphite/Carbon Fiber/Phenolic Resin Composite

Composites made of phenolic resin filled with natural graphite platelets and carbon fibers are fabricated by mechanical mixing, followed by compression molding. The flexural strength and electrical conductivity of composite are analyzed to determine the influence of phenolic resin and carbon fiber on mechanical and electrical properties. It is found that there is a marked dependence of the electrical conductivity and flexural strength on phenolic resin content. The electrical conductivity decreases and flexural strength increases with the increasing of phenolic resin loading. The presence of carbon fiber helps improve the flexural strength of composite such that 4 wt% CF increases the flexural strength of composite about 90%. However, an excess amount of carbon fiber reduces the flexural strength due to poor dispersion of carbon fiber in composite. The result also shows that the addition of carbon fiber exhibits a slight effect on the electrical conductivity of composite at low carbon fiber loadings.