Cellulose intermolecular cross-linking

When the pretreatment temperature exceeds 100 C, monophosphates of cellulose are formed, the development of intermolecular cross-linking is promoted and depolymerization of cellulose is hindered. 

The factors inhibiting macro-flow in vulcanised rubber are the chemical cross links due to vulcanisation (and probably also molecular entanglements), considerably assisted by the phenomenon of crystallisation. In unvulcanised raw rubber macro-flow may occur to a certain extend. In cellulose crystalline junction points of a high degree of stability are responsible for the exclusion of macro-flow. In rubber the chains are very flexible and consist of a large number of statistical chain sections in cellulose the chains are stiffer and consist of a small number of chain elements. In the former case the intermolecular forces are weak, in the latter case they are strong. 

In the diagram, load per unit cross section (stress) is plotted against deformation expressed as a fraction of the original dimension (strain). Even for different materials the nature of the curves will be similar, but they will differ in (1) the numerical values obtained and (2) how far the course of the typical curve is followed before failure occurs. Cellulose acetate and many other thermoplastics may follow the typical curve for almost its entire course. Thermosets like phenolics, on the other hand, have cross-linked molecules, and only a limited amount of intermolecular slippage can occur. As a result, they undergo fracture at low strains, and the stress-strain curve is followed no further than to some point below the knee, such as point 1. 

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