The Type and Amount of Cellulose Fiber

Wood flour or rice hulls contribute to the increase in stability of WPGs against thermooxidation (see, for example, data in Table 3.11 and 15.15). 

Not only plastic but also cellulose contributes to free radical formation and adds their share to the system. Gellulose is degraded by temperature effects and UV light. 

TABLE 15.15 Effect of rice hulls on the OIT (at 190°C) of an HDPE, processed on the Brabender laboratory extruder 

However, cellulose is a relatively stable material. In lignified cellulose, such as wood flour, the degradation of lignins dominates the photochemical processes. Most of the lignin is lost from the wood surface during UV exposure, and the depth of degradation is in the range of 0.5-2.5 mm (0.02 -0.1 ) [9]. 

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