Ammonia wood plasticization

The use of aqueous ammonia in the preparation of wood fiber filled phenolic plastic molding has been investigated. In this case ammonia both plasticizes the wood filler and catalyzes the phenolic methylol condensation. With proper formulations and treatments, it is possible to maximize the quantity of wood fiber that can be used and minimize the resin without deterioration of properties of the molded product (61). 

A recent process development from Zurich by M. Bariska (20) has a number of important and interesting features. The method is specifically designed to test the applicability of ammonia forming to commercial practice. Secondly it constitutes a lower extremum, an investigation of conditions of minimum useful plasticity. Furthermore it is based on extensive investigations of kinetics, thermodynamics, sorption processes, and structural changes characteristics of the ammonia wood system. 

Most solvated electron-treated wastes require posttreatment. The first posttreatment involves removing and recovering ammonia from the matrix. This is accomplished by passing hot water or steam through the jacket of the treatment cell and by condensing the ammonia for reuse. Materials such as shredded paper, wood, plastic, rubber, and PPE can be volume-reduced after the SET treatment by using commercially available compacting equipment. 

The low water absorptivity and good resistance to hydrostatic pressure make syntactic foams very useful for marine and submarine construction. Materials to be used for deep-sea application must have 1) low compressibilities at high hydrostatic pressure, 2) low thermal expansion coefficients, 3) low water absorption, and 4) good fire resistance. The fluids used for buoyancy in deep water submersibles include gasoline, ammonia, and silicone oil, while the solids include plastic, glass and aluminium foams, lithium, wood, and monolithic polyolefins. The liquids are dense but have low... 

Effect of Water. Wood is usually treated with ammonia in the presence of some amount of water. The effect of water depends not only on the amount of water but also somewhat on the history of the wood sample and the method of treatment. Thus, when oven-dried veneer strips were treated with cold liquid ammonia-water mixtures at ambient pressure, the flexibility of the treated wood was substantially decreased when the moisture content of the ammonia was much above 10% (26). Other protonic solvents act similarly (26). In apparent contrast, the rate of sorption of ammonia from the gas phase by wood is markedly enhanced by moisture in the wood (19). Bone dry wood absorbs ammonia quite slowly at ambient temperatures but if the wood has ten to twenty percent moisture content, sorption and plasticization occur much more rapidly. Presumably the moisture opens the pore structure of the wood and also dissolves ammonia much more readily than bone-dry wood. On continued treatment, the water is presumably displaced from the wood by the ammonia... 

In general, two stages of the gaseous ammonia plasticization process can be distinguished. In the initial phase the hydrate envelope of the wood substance interacts with ammonia, causing the formation of ammonia-complexes, NHi +0H , NHi 0H etc. These... 

Preliminary investigations suggest that wood slicing with knives can be applied successfully to ammonia plasticized wood and that thicker boards and veneers can be cut than by conventional methods. Savings of material and energy are envisioned over the use of sawing (62). 

Davidson, R. W., "Plasticizing Wood with Anhydrous Ammonia," Technical Bulletin, Dept. Wood Products Engineering, SUNY College of Environmental Science and Forestry, Syracuse,... 

The first observation of the plasticization of wood by ammonia was by Stamm, A. J., Forest Products Journal, (1955), 413-416. 

Anhydrous ammonia also is known to cause temporary platicization of wood. The ammonia swells and plasticizes both the lignin and the cellulose, and the crystalline structure of the cellulose is converted to a different form in the process. To shape the wood, it is immersed in liquid ammonia or treated with gaseous ammonia under pressure until the cell walls have been penetrated and the wood becomes pliable and flexible. In this condition it is easily shaped and formed by hand or mechanically. The ammonia readily vaporizes and evaporates from the wood, so that the wood regains its normal stiffness but retains the new form into which it has been shaped. With this process the wood can be distorted into quite complex shapes without springing back to its original form. Treating plants have been developed on a pilot-plant scale, but the process has not been widely adopted. 

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