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Effect of Masterbatch Carrier Type on Rheological, Thermal and Mechanical Properties of Bimodal Polyethylene Compounds with Different Short Chain Branching Distribution

Gholami, Farzad | 2017

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 51334 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Pircheraghi, Gholamreza
  7. Abstract:
  8. Polyethylene is one of the most widely used industrial materials for producing water and gas pipes due to low pricing and mechanical properties and high corrosion resistance. Various parameters such as molecular weight and the short chain branches distribution strongly affect the mechanical properties of these materials. PE100 grade of this material has been introduced with bimodal molecular weight distribution, has excellent mechanical properties and especially high creep resistance and today is used for pipe production in water distribution systems. In the first part of this study, the effect of 1-butene comonomers on different properties of three PE100 and two PE80 resins produced in different petrochemical complexes in Iran has been investigated. To investigate the chemical structure and distribution of the comonomer in these specimens’ rheology, DSC tests, and tensile tests were performed and the data of these test verified by data of creep test. If the distribution of short chain branches on long chain molecules were uniform, morphology is unordered and non-spherulite, and therefore creep resistance is higher in these specimens. In this context, with the reduction of the parameter n in the Avrami equation, the morphology will be layer ordered, then resistance to crack growth will increase. Polyethylene tubes, exposed to sunlight due to ultraviolet absorption, are subject to severe mechanical degradation, which is why they use carbon black as the cheapest and most affordable absorbent of ultraviolet radiation. In the second part of this study, to investigate the effect of masterbatch Carrier on different properties of black compounds from two different types of carbon black masterbatches that have different Carrier (HDPE and LDPE). It has been observed that the masterbatch with LDPE carrier polymer has been shown to improve the processability of the samples due to the low viscosity and, on the other hand, with different tests, it has been shown that the presence of LDPE chains in the structure compared to HDPE chains will improve the resistance to slow crack growth. This is because of an increase in the amount of entanglement of crystalline layers in the presence of LDPE chains. The results of the FNCT test show that the creep life at 50 ℃ and 9.5 MPa for the best PE100 sample with a uniform comonomer distribution is approximately 500 hours, while for the blacked sample with LDPE and HDPE masterbatch, this value is approximately 300 hours and 250 hours, respectively. Reducing the creep life of black specimens attributed to the effect of carbon black on the stress concentration and the inhibition of the entry of long branched chain into crystalline structures. The loss of creep life in black samples from LDPE masterbatch is lower due to the entry of carrier polymer chains to the crystalline structure
  9. Keywords:
  10. Rheological Properties ; Mechanical Properties ; Carbon Black ; Short Chain Branches Distribution ; Full Notch Creep Test ; Slow Crack Growth ; Polyethylene 100

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