PROCESSING STABILIZATION OF HDPE - A COMPLEX STUDY OF AN ADDITIVE PACKAGE

Response surface methodology (RSM) has been applied for optimizing an additive formulation in HDPE. This experimental approach allows a more precise description of the whole complexity of the polymer stabilizat ion. In contrast to the generally used single parameter variations, RS M gives access to the mutual interactions of the additives and their t emperature dependence. Several responses (MFI, melt pressure, vinyl un saturation content) are shown to be sensitive to the composition of th e additive system. The data emphasize the importance of the phosphorus based stabilizer for HDPE melt processing. The contribution of the ph enolic antioxidant is temperature dependent passing through a maximum. Some interaction terms, including the effects of processing aids, gai n importance under certain conditions, and their influence can even su rpass the direct contributions of the single additives.