关键词：
polyethylene
nanosphere
crystal structure
crystallinity
glass transition temperature
melting temperature
surface roughness
mechanical properties
atomic force microscope
摘要：
The high molecular weight (MW) polyethylene (PE) particles of particle size varied from macro to micron to nanometer were synthesized by Grignard reagent. The microscopy analysis (scanning electron microscope, SEM;transmission electron microscope, TEM;and atomic force microscope, AFM) shows the spherical shape of PE particles. The effects of particle size, varies from macro to nanometer scale on crystal structure, crystallinity (chi(c)), glass transition temperature (T-g), melting temperature (T-m), surface roughness and mechanical properties were studied. Differential scanning calorimetry (DSC) experiments show that the nanoparticles of PE are highly crystalline (chi(c) approximate to 72%). The crystal length of PE nanoparticles is found to be approximately 14 angstrom. Although the Gibbs-Thomson equation is explained the depression of melting temperature (Delta T-m) by 5 degrees C, the impervious results of T. are still not fully understood. The low roughness value (2 angstrom) proves the presence of "atomic-scale-chain" folding at the surface of PE nanoparticles. A novel protocol is developed, and the elastic modulus of individual nanospherical PE particles is computed from 'force-distance' mapping curves of AFM. Hemispherical tungsten (W) tip was fabricated from focused ion beam and used as an indenter to measure the mechanical properties. It is found that the nano sized PE particles have higher elastic modulus (E = 1.2-1.4 GPa) compared to the bulk or macro sized PE (E = 0.6-0.7 GPa). The results corroborate the robustness of our experiments, since, the analogous results for macro sized particles match well with the literature.
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详细信息
中文科技期刊
