Polyblends wood-polymer

Some commercial, linear (thermoplastic) polymers produce blends with lignin and lignin derivatives that fail to result in phase separation on macroscopic scale. Polyblends with lignin derivatives sometimes resemble plasticized or anti-plasticized materials. The greatest contribution lignin can make to thermoplastic systems is that of modulus and this is the same as that which lignin makes to the amorphous component of wood. 

In many ways, wood, one of man s oldest and most widely used materials, resembles the polyblends or composites discussed elsewhere (Hearmon, 1953). Since wood is a mixture of two polymers, it is a polyblend. Its behavior, however, more closely resembles that of oriented fiber composites. Since many synthetic materials are competitive with wood in commerce and resemble the structure of wood, it is of interest to understand the original natural product. 

In most of the two-component systems discussed so far, such as rubber-reinforced polyblends, the density or specific volume is approximately an average of the values for each component. There may be some exceptions to this generalization for example, if the smaller component fills free volume available in the major phase (Chander, 1971 Harmer, 1962 Huang and Kanitz, 1969). A similar but more important phenomenon exists when the volume available for filling by a monomer comprises not only free volume elements, but also gross pores, which may range in size from tens of angstroms to the order of micrometers or more. Examples of matrices may include partially sintered polymers, ceramics or metals, cement, concrete, minerals and rocks, paper, and wood (American Chemical Society, 1973). Clearly such systems tend to be complex even the matrix itself is often a multiphase material. 

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