Peng Fei Fang

Study of structural characteristics of HDPE/CaCO3 nanocomposites by positrons

Abstract The positron lifetime spectra were measured as a function of weight fraction Φw of CaCO3 nanoparticles in the high-density polyethylene/CaCO3 (HDPE/CaCO3) (polymer) nanocomposites. It is observed that, first, positronium (Ps) is formed and annihilates in the free-volume hole of HDPE and the free-volume concentration decreases with increasing fraction of the CaCO3 nanoparticles in the HDPE/CaCO3; second, the positron lifetime τ2 and its intensity I2 are strongly affected by the structure of the interface layer between CaCO3 nanoparticles and HDPE matrix.

Positron Lifetimes and Crystallinity of γ-Irradiated Polypropylenes

The microstructure of the polypropylenes (PP) irradiated by gamma ray was studied by positron lifetime technique and differential scanning calorimetry (DSC). Lifetime measurement shows o-Ps intensity decreases with increasing γ irradiation dose. The crystallinity of irradiated samples was detected by DSC method. The correlation between o-Ps intensity and crystallinity indicates γ-ray can induce higher crystallinity in the polypropylene at low irradiation dose.

Effect of Oxygen on the Free Volume Property of Poly (Ether-Urethane) Irradiated by Neutron

The free volume property and intermolecular interaction (especially hydrogen bonding) of poly (ether-urethane) (PEU) irradiated by neutron under different atmosphere has been studied by positron annihilation lifetime spectroscopy (PALS) and Fourier transform infrared (FTIR). The results suggested that the hydrogen-bonding interactions and free volume property in PEU depended strongly on the neutron irradiation dose.

The Effect of Anneal on PP and PA Blends Studied by Positron

The anneal effect of PP/PA/MMT blends had been studied by positron annihilation lifetime spectra (PALS). The o-Ps lifetime and intensity of unannealed blends were linearly additive basis on the PA weight fraction, which was coincident to the simple compound rule. However, the o-Ps intensity of the samples decreased after samples annealed.

Temperature Dependence of Free Volume in Epoxy/Rectorite Nanocomposites by Positron Annihilation

Recently polymer nanocomposites[1,2] have been receiving special attention because of its advantages and unique properties in comparison to the traditional polymer composites.The structural transformation of Epoxy (cured by polyamide) and epoxy/Rectorite nanocomposite(with 0.5% rectorite content) is studied by PALS as a function of temperature from 30K to 490K. For Epoxy and Epoxy/Rectorite nanocomposite, the glass transition temperature (Tg) is observed to be 270K and 260K, the second transition temperature (Tγ) is 160K and 120K, the viscous flow temperature (Tf) is the same as 380K. The result shows that properties of the free-volume in nanocomposite have been changed by the rectorite platelets fully separated in material at low temperature. At the same time, we find that the intensity of o-Ps decreases with increase of the temperature at the softening temperature above the Te.

The Interface of Multi-Phase Polymer Systems Studied by Positron Annihilation

MA-g-HDPE and PA6-MMT were selected to improve the compatibility of HDPE and PA6. Positron annihilation lifetime spectroscopy (PALS) and optical microscopy were utilized to characterize the interface of the blends.