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Study the Effect of Carrier Resin of the Nucleating Agent Masterbatch on Crystalline Structure and Physical and Mechanical Properties of Polypropylene

Shokrollahi, Maryam | 2019

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52455 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. Polypropylene (PP) is one of the most widely used commercial plastics in various industrial applications due to its desirable physical and mechanical properties and low cost. Engineering properties of this polymer depend very much on its crystalline structure. It is a common practice in polymer industry to modify crystalline structure by means of nucleating agents. Since nucleating agents are added in a rather low level to polymers, some investigators have tried this task in modifying crystalline structure of polypropylene by incorporating nucleating agent masterbatches. However, none have looked at the possible influence of the carrier resin in such masterbatches on the performance of nucleating agent in the parent matrix. In this study, the effect of carrier resin of the nucleating agent masterbatch was investigated by adding an α-phase nucleating agent (DMDBS) into a pipe grade polypropylene block copolymer. Four samples were made in this study. The control sample was free from nucleating agent and the other three contained 0.3 wt% DMDBS. Nucleating agent was incorporated in two samples by means of masterbatches while the carrier resins of the masterbatch in these samples were a copolymer and a homopolymer of PP, respectively. The forth sample had a composition exactly the same as the third one but the entire constituents were added in a single step, i.e. masterbatch was not made prior to the final compounding.In order to analyze the influence of nucleating agent and the carrier resin of the masterbatch on the structure and crystalline behavior of the polymer matrix, different characterization techniques including rheological test, X-ray diffraction (XRD), differential scanning calorimetry (DSC), and optical microscopy were employed. Both isothermal and non-isothermal crystallization kinetics were studied. It was shown that addition of 0.3 wt% DMDBS, regardless of its incorporation method, led to 16°C increase in isothermal and non-isothermal crystallization temperature and 30% increase in crystallinity. The isothermal melt crystallization data were analyzed against Avrami and L-H models. The results indicated that the maximum crystallization rate in the testing temperature range was reached in the fourth sample, i.e. the one that the carrier resin was added without making masterbatch. L-H theory revealed that addition of DMDBS in the form of masterbatch results in a remarkable increase in overall crystallization rate, and the sample with homopolypropylene as carrier resin in the masterbatch showed the maximum crystallization rate. According to TTT diagrams developed based on the L-H model, the critical cooling rate where the drastic change in crystallinity occurs with increasing cooling rate, varies in different samples made in this study. This analysis shows the highest critical cooling rate belongs to the sample with homo-polypropylene as the carrier resin in the masterbatch. Based on the results of this study, one may conclude that under high cooling rate of industrial setting, samples with higher critical cooling rate provide higher degree of crystallinity in the final product
  9. Keywords:
  10. Homo-polypropylene ; Copolymer Polypropylene ; Nucleating Agent ; Masterbatch Carrier Resin ; Crystallization Rate ; Isothermal Crystallization

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