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A traditional strategy for toughening modification of polypropylene (PP) is to utilize the excellent impact resistance of β-PP by introducing β-phase nucleating agent (β-NA) into PP matrix. In this work, highly oriented PP/TMB-5 composites and PP/POE/TMB-5 composites were prepared via solid die-drawing (SDD) at 135 °C. The results show that after SDD, on the existence of β-α phase transformation in processing, the toughness of PP/TMB-5 composites was though improved but still limited. Then, introduced polyolefin elastomer (POE) particles into PP/TMB-5 matrix, β-α phase transformation was suppressed, and the toughness were further improved. The effect of grain refinement caused by β-NA were further enhanced by drawing stress and meantime abundant microsized voids generated between oriented lamellae, which were all beneficial to its toughness. The oriented structure inherently strengthened materials rigidity. Thus, the tensile strength and impact strength of PP/POE/TMB-5 composites after SDD were 145.45 MPa and 30.6 kJ/m2, 4.8 times and 3.8 times higher than pure PP, respectively. [ABSTRACT FROM AUTHOR]

An investigation specifically focusing on the relationship among processing parameters, structure, and mechanical properties of solid two‐stage die‐drawn polypropylene (PP) has been done in this study, which aimed at providing a reliable reference in the choose of appropriate conditions that can be able to meet a specific processing requirement. PP sheets were drawn through a self‐design solid two‐stage die‐drawing apparatus to various drawing ratios (DRs) at different speeds and with different die‐exit thicknesses. The results showed that tensile strength, modulus, and the degree of orientation significantly increased with the nominal DR and could be further improved by increasing the drawing speed. While the crystallinity increased prior and decreased to near a constant value when the drawing speed was over 150 mm/min in the researched scope. Larger the die‐exit thickness was, lower the orientation degree was but higher the crystallinity could be obtained. Compared with crystallinity, orientation degree plays a leading role in the final product properties during a two‐stage solid die‐drawing process. POLYM. ENG. SCI., 59:2347–2355, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Oriented structure, mainly controlled by processing conditions, is another efficient method of reinforcing polymer materials in addition to compounding with rigid inorganic fillers such as carbon nanotubes (CNTs). The mechanical properties of oriented polypropylene (PP)/multiwalled CNT (MWCNT) composites, which are vital to their application fields, are investigated extensively in this paper, with an aim to distinguish the contribution of MWCNTs contents from that of the oriented structure to the final performance of the composite. The results indicate that MWCNTs mainly increase the modulus of the composites by approximately 140%. The oriented structure formed during the die-drawing process contributes more to the enhancement of tensile strength, increasing up to 550%. The modulus and tensile strength can be further improved by increasing the drawing speed. Moreover, the tensile stress field in the die-drawing process can vastly improve the dispersion of the MWCNTs in the matrix, thus providing a new idea for improving the dispersion of nanofillers in the polymer matrix. • Die-drawing process contributes more to increase tensile strength. • MWCNTs mainly increase modulus rather than tensile strength. • Tensile strength and modulus can be further improved by increasing the drawing rate. • The die-drawing process can vastly improve the dispersion of MWCNTs in the PP matrix. • MWCNTs can hinder the molecular chain orientation. [ABSTRACT FROM AUTHOR]