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Studying the Effect of Rubber Type on Mechanical Behavior and Scratch Resistance of Rubber-Modified Copolypropylene

Najaf Tomaraei, Golnaz | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42791 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. Polypropylene (PP) has a great market among the commodity thermoplastics. However, its application as an engineering plastic is limited due to the poor toughness and impact strength, especially at low temperatures and high deformation rates. To overcome this shortcoming, elastomeric modifiers have been used in engineering applications and thus rubber-modified PP blends have become a field of growing interest. In this regard, there have been great advances in blending technologies and also catalysts used for polymerization of olefins. Among these advances, the most applicable ones are impact polypropylene copolymers and also the advent of new types of olefinic copolymers that can replace EPR with higher compatibility with PP. It is well recognized that introducing a rubbery phase reduces the modulus, yield stress and scratch resistance of the PP matrix. Previous researches conducted in our group show that cavitation resistance of the elastomeric phase and its adhesion to the matrix are key parameters to control the scratch resistance of PP. In the current study, an attempt has been made to investigate the effect of these parameters on scratch behavior of rubber-modified co-polypropylene. For the purpose of this study, elastomers with different cavitation resistance and different degree of compatibility with the co-PP matrix have been considered. The microstructure was investigated via scanning electron microscopy. DSC, XRD and transmission optical microscopy (TOM) techniques were conducted to investigate the crystallization and melting behavior, crystallinity and crystalline structure of blends. Furthermore, DMTA was used to study the glass transition temperature of the components of the blends. Mechanical properties were evaluated via tensile, impact charpy and scratch tests. The deformation micromechanisms at notch tip and the scratched surface were analyzed by TOM and SEM respectively. Results show that the microstructure and mechanical properties of the blends are significantly affected by the rubber type. Ultimately, in the studied range of composition, it is found that the highest impact strength as well as the lowest loss of scratch hardness is achieved in the blends containing TPV as an elastomeric phase.
  9. Keywords:
  10. Scratch Rsistance ; Consistency ; Cavitation Resistance ; Rubber-Modified Polypropylene ; Co-Polypropylene

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