IMPROVED AGING PERFORMANCE OF VIRGIN EPDM ROOF-SHEETING COMPOUNDS WITH AMINE-DEVULCANIZED EPDM WEATHERSTRIP MATERIAL

Sulfur-cured EPDM building-profile material was reclaimed in a co-rotating twin-screw extruder using hexadecylamine as reclaiming aid. This reclaim was blended with increasing amounts of a virgin EPDM roof-sheeting masterbatch and cured at temperatures allowing for a reversion-free vulcanization. The trends in cure characteristics showed that increasing amounts of reclaim employed in the blends lowered the reversion-free cure temperature and the maximum torque values, while the vulcanization speed was increased. The insoluble fraction and crosslink density both decreased, while the ratio of mono- to di- and polysulfidic crosslinks increased with growing reclaim contents. A SEM-EDX morphology study of the blends, in order to evaluate the dispersion of the reclaim into the virgin rubber matrix showed, that even large amounts of reclaimed material resulted in homogeneous and smooth compounds. Tensile strength, modulus at 300% strain and hardness decreased, while elongation at break, tear strength and compression set at 70 degrees C increased with increasing reclaim ratios. Irrespective of the blend ratios, the mechanical properties all fulfilled the most stringent UEAtc specifications for EPDM roof-sheeting. Increasing reclaim contents improve the aging resistance and prolong the time before a practical limiting value for elongation at break of 250% for EPDM roof-sheeting purposes is reached.