Lignin engineering materials

It is almost paradoxical that in the history of mankind composite materials were earlier used than their "homogeneous" rivals. The earliest "engineering materials" were bone, wood and clay. Wood is a composite of matrix lignin and a cellulosic reinforcement bone is a natural composite where fibres of hydroxyapatite reinforce the collagen matrix and the oldest building material was adobe clay as a matrix, reinforced by vegetable fibres. After the industrial revolution other composites were added reinforced rubber, reinforced concrete, reinforced asphalt, etc. 

The concept of composite materials is ancient to combine different materials to produce a new material with performance and efficiency imattainable by the individual constituents. An example is adding straw to mud for building stronger mud walls. Some more recent examples, but before engineered materials became prominent, are steel rods in concrete, cement and asphalt mixed with sand, fiberglass in resin, etc. In nature, examples abound a palm leaf, cellulose fibers in a lignin matrix (wood), collagen fibers in an apatite matrix (bone), etc. 

As important engineering materials in advanced composites for a variety of industries, carbon fibers were applied to aerospace, civil engineering, automotive, and wind-power applications. Their properties were characterized by high tensile strength, high stiffness, low density, elevated temperature tolerance, and low thermal expansion. Within a considerable amount of research in the past decade, lignin was proved to be an appropriate precursor to produce carbon fibers. And as one of three major biopolymers in the cell wall of plants, with the second most abundant terrestrial material, lignin is considered to be a very suitable, readily available, relatively... 

The advent of lignin-based polymeric materials as putative engineering plastics represents one of several technological... 

A considerable amount of data has accumulated regarding the modification of lignins to engineering plastics. Unfortunately, the incorporation of various monomers and polymers, such as di- and polyvalent epoxyphenols, esters and isocyanates, in the lignin structure in most cases resulted in brittle or tarry materials whose properties designated them as potential adhesives, lacquers, dispersants and films, but not as structural materials (36-40). 

To conclude the above methods of incorporation of modified lignin in polymer networks and blends opens new promising possibilities for the technical use of lignins and makes it competitive with other raw materials for engineering plastics. 

Various materials have been used for biosorbents to remove toxic metals from process or groundwater. Ones selected by the US Army Corps of Engineers in 1997 [1] for further study include chitosan, peat moss, seaweed (algae), and lignin. Work in our laboratoiy has shown that uptake by peat moss [2] and algae [3] occurs by an ion exdiange medianism in which an existing proton or metal is displaced in the process ... 

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