Mechanical Properties and Mullins Effect in Natural Rubber Reinforced by Grafted Carbon Black

Wen Fu,Wenlong Peng,Li Wang,Haotuo Xiao,Shenglin Li,Cuiwen Liu,Jianning Huang

doi:10.1155/2019/4523696

Wen Fu, Wenlong Peng + Show 5 more

Open Access

https://doi.org/10.1155/2019/4523696

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Abstract

The obvious polarity difference between the carbon black (CB) and the natural rubber (NR) causes the CB hard to be dispersed in the NR matrix when the addition amount is large. In this paper, polyethylene glycol (PEG) was grafted onto the surface of CB by the liquid phase. The grafted carbon black (GCB) was prepared and applied to reinforce NR. The main physical and mechanical properties of NR were improved because of the better compatibility between GCB and NR. The Mullins effect of the vulcanizate was calculated by the cyclic stress-strain experiment. The results showed that the Mullins effect both existed in the virgin NR system and filled NR system. The degree of Mullins effect was increased with the increase of the filler addition, but that was different for CB and GCB. When the filler addition was below 20 phr, the Mullins effect of NR/GCB was stronger than that of NR/CB. However, when the filler addition was over 30 phr, the Mullins effect of NR/CB was stronger than that of NR/GCB. The Mullins effect was affected by the heat treatment temperature and time. The mechanisms of the Mullins effect were analyzed.

Highlights

Because the rubber materials have high elasticity, damping, and other excellent properties, they have been widely used in tires, electronics, military, aerospace, and other fields [1,2,3]
In order to test the effect of the treatment temperature and storage time on the Mullins effect, after the sample was stretched three times, the sample was stored for 2 h at 60∘C, and the sample was stretched to the same specified strain at room temperature and the required energy was recorded as Ws
Due to the large difference in polarity between carbon black (CB) and natural rubber (NR), it is difficult for CB to be uniformly dispersed in the rubber matrix, especially when the amount of CB is large, thereby affecting the physical and mechanical properties of the rubber

Summary

Introduction

Because the rubber materials have high elasticity, damping, and other excellent properties, they have been widely used in tires, electronics, military, aerospace, and other fields [1,2,3]. Grafting some polymer chains on the surface of CB to reduce the polarity difference between CB and the matrix is a good strategy, thereby enhancing the reinforcing effect of CB. Houwink [21] put forward that the Mullins effect resulted from the slipping of the molecular chains adsorbed on the filler surface during the stretching process. The hard phase would be transferred to the soft phase, which led to the Mullins effect This view was further perfected by Johnson [22]. Under the external force, the rubber molecular chains adsorbed on the surface of fillers would be desorbed, reducing the thickness of the rubber shell and weakening the interaction between the rubber and carbon black. The Mullins effect mechanisms were deduced by comparing the effects of GCB and CB on the Mullins effect of NR under different conditions

Experiments

Sample Preparation

Characterization

Results and Discussion

Conclusions