Study Of Inhomogeneous Orientation Of Rubbers During Stretching

The molecular chains of Natural Rubber will orientation and crystallization during uniaxial stretching. The micro structure change, orientation and crystallization, will enhance the mechanical properties of NR, which called self-reinforcement effect. The current researches mainly focus on the strain-induced crystallization of crystalline rubbers (i.e. NR) and ignore the amorphous orientation of non-crystalline rubbers, such as SBR and NBR. However chain orientation is also a key point for non-crystalline rubber and affect the mechanical properties of rubber. So it’s important to find out the orientation behavior of crystalline and non-crystalline rubbers during stretching. This work analysis the orientation of NR, BR, SBR and NBR during stretching combined with infrared dichroism, X-ray diffraction and sonic method. The achievements are(1) the orientation function of NR, BR, SBR and NBR, measured by infrared dichroism and sonic method, increases with the strain during stretching. X-ray patterns show that NR start to crystallization at strain of3and no crystal reflect of BR and SBR, which means no SIC happened. The amorphous orientation ratio of NR increase firstly and then drop to bottom at strain of3, continue to grow after that. However, it keeps increasing with strain for BR and SBR.(2) We confirmed the stability and reliability of sonic machine, the practicability of sonic method in measuring orientation of stretched rubber. The orientation function of NR obtained by sonic single-phase model is much bigger than the infrared dichroic one, which can be explained by the existing of highly oriented crystal phase and amorphous phase. We suggest that there are two phase in stretched BR and SBR—high oriented regions and low oriented regions.