Unexpected Improvement of Both Mechanical Strength and Elasticity of EPDM/PP Thermoplastic Vulcanizates by Introducing β-Nucleating Agents

Thermoplastic vulcanizates (TPVs) are among the most concerned polymer materials because they exhibit a combination of good elasticity and easy processibility and recyclability. Herein, a β-nucleating agent (β-NA) was introduced into ethylene propylene diene monomer (EPDM)/polypropylene (PP) TPVs through a simple and effective postprocessing method to induce the formation of β-PP crystals for preparing high-performance TPV products. High content of β-PP crystals is achieved in TPV, but the total crystallinity of the PP matrix remains constant. Unexpectedly, both mechanical strength and elasticity of TPV with β-PP crystals (β-TPV) are significantly higher than those of TPV with α-PP crystals (α-TPV). The change in the structure of both α-TPV and β-TPV during real-time deformation and the deformation mechanism was carefully studied by combining Synchrotron two-dimensional wide-angle X-ray diffraction (2D-WAXD) and atomic force microscopy nanomechanical mapping (AFM-NM) techniques. The mechanism for the simultaneous improvement of mechanical strength and elasticity of TPV is revealed.