A new approach for silane curing polyolefin elastomer/linear low density polyethylene blends by Monosil and Sioplas processes

Abstract

Silane cross-linking of metallocene-based polyethylene-octene elastomer (POE)/linear low density polyethylene (LLDPE) blend was carried out using the single-step Monosil process and two-step Sioplas process in an industrial scale twin-screw extruder. The study revealed that benzoyl peroxide (BPO) is a better initiator than dicumyl peroxide (DCP) for grafting reaction of vinyl trimethoxysilane (VTMS). The optimum values of compression set, gel content and tear strength which were, respectively, found to be 40.4%, 79% and 22.6% obtained at 0.2 w% of BPO. Addition of 0.3 w% antioxidant cause the curing time decreased from 14 to 16 h to 8 h. Oit of the sample was increased linearly with increasing the antioxidant content up to 0.5 w%. The effect of dibutyltin dilaurate (DBTDL) as catalyst on the melt flow index (MFI) of the silane grafted compounds, with the aim of selecting an appropriate silane grafting process, was investigated. The results showed a MFI= 6.4 g/10 min for the silane grafted compound obtained from the Sioplas process, but, MFI= 1.9 g/10 min which was due to the presence of the catalyst in the Monosil process indicated that this method is not a promising process for silane grafting.

Highlights

• Silane crosslinking POE/LLDPE blend was carried out using the Monosil and Sioplas processes in a twin-screw extruder.

• BPO is better initiator for grafting reaction of VTMS than DCP.

• The curing time required for confirming hot set test was decreased from 14 to 16 h to 8 h by addition of 0.3 wt% antioxidant, Irganox 1010.

• OIT time increased linearly with increasing the antioxidant concentration.

• Sioplas process caused lower crosslinking degree as well as minimum pre-crosslinking, which prevented the formation of gell spots and rough surface.

Keywords:

• POE/LLDPE blend
• Sioplas process
• Monosil process
• pre-crosslinking
• silane grafting

Acknowledgments

The authors gratefully acknowledge the financial support of Ferdowsi University of Mashhad (project code: 3/43281), Mashhad, Iran, and the technical equipment and chemical support of Baspar Sazeh Toos Co. of Part Lastic Group Co.