MSc thesis from Luleå tekniska universitet (Luleå Univeristy of Technology/Maskinteknik/Polymer Engineering)

Author: Jinxia Li; [2008]

Keywords: Recycled EPDM rubber; Unvulcanized rubber; LDPE; EMA; Reactive compatibilization; Non-reactive compatibilization; Ethylene octene copolymer; Phenolic resins; Tensile properties; Tear strength; Microstructure; Pressing pressure; rubber recycling,

Abstarct: Blends containing recycled EPDM rubber and thermoplastics, EMA and LDPE were studied. Two compatibilization methods, reactive and non-reactive, were evaluated. Ethylene octene copolymer (EXACT 0210) was used as non-reactive compatibilizer. Phenolic resins (SP1045 & HRJ10518) were reactive agents. There existed an optimal composition of compatibilizers which were 25wt% in the case of reactive and non-reactive agents added to 15wt%EMA and 55-60wt% EPDM rubber.

EXACT-compatibilized blends gave high elongation at break while phenolic resin-compatibilized mixtures gave high stiffness in comparison with the chosen reference material. Comparison in compatibilizing capabilities HRJ-10518 and SP-1045 was carried out. The former one had better capabilities than the latter at high compatibilizer content. Talcum was used as anti-agglomeration agent but failed to work properly. Pressing pressure could be minimized without any adverse effect. Non-vulcanized rubber was used to enhance tear strength but its effect was small by assuming that there exists degradation of the interfacial surface at high temperature. SEM analysis revealed homogeneous microstructure in both kinds of compatibilization. EXACT 0210-compatibilized blends showed more plastic deformation of the matrix than reactive blends. Stable connection between phases was also observed.

Tensile strength of the LDPE based blends were a little lower than that of EMA based blends and the hardness was a little higher. Compared to EMA based blends, the elongation at break was much lower while the young's modulus was much higher with LDPE based blends. Compression set of both LDPE and EMA based blends was high compared to the reference materials supplied by Rerub AB, Piteå.

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