Study on the Variations of Molecular Weight and Its Distribution and Micro-structure on Mechanical and Dynamical Properties of CB Reinforced SSBR Compounds Using Different Curing Systems

Document Type : Research Paper

Authors

Department of Rubber Processing and Engineering, Faculty of Processing, Iran Polymer and Petrochemical Institute, P.O. Box: 14975-112, Tehran, Iran

Abstract

Hypothesis: The physical and mechanical as well as the viscoelastic properties of SSBR compounds are strongly dependent on the molecular weight and its distribution, 1,2 vinyl branch, and styrene content, as well as the selected cure system which has been thoroughly studied in this work 
Methods: Three commercial SSBR grades were selected. The GPC technique was used to determine the molecular weight and its distributions. Four conventional sulfur cure systems with two primary and secondary accelerators were chosen and 12 compounds have been prepared with their corresponding test specimens. A series of experiments were conducted including the measurements of the storage and loss moduli of the master compounds, cure properties, mechanical properties (tensile strength, elongation-at-break, modulus and hardness), abrasion resistance, dynamic mechanical thermal analysis (temperature sweep at a constant frequency) and dynamic properties using RPA (strain sweep at constant frequency and temperature)
Findings: Increasing the molecular weight would decrease the Payne effect in master compounds. Rubber compounds with TMTD as the secondary accelerator have higher crosslink density and hardness which have been enhanced with increasing the molecular weight but the abrasion resistance was decreased. A comparison of the mechanical properties between compounds prepared with an identical micro-structure revealed that rubber with a broader molecular weight distribution and longer chains shows better mechanical properties. In addition, the compounds in which the rubber has a higher molecular weight, average polydispersity index, lower glass transition temperature, and lower 1,2 vinyl content showed lower and higher loss factors at 60 oC and 0 oC, respectively. This indicates that it can be used as a good potential rubber in tire tread.

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Iranian Journal of Polymer Science and Technology
Volume 37, Issue 5 - Serial Number 193
January and February 2025

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