Search Results

You are looking at 1 - 3 of 3 items for

  • Author or Editor: Pei Wang x
  • All content x
Clear All Modify Search

Abstract  

In this study, α-phase nucleating agent (NA) 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS), β-phase rare earth NA (WBG), and their compound NAs were introduced into isotactic polypropylene (iPP) matrix, respectively. Crystallization kinetics and subsequent melting behavior of the nucleated iPPs were comparatively studied by differential scanning calorimetry (DSC) under both isothermal and nonisothermal conditions. For the isothermal crystallization process, it is found that the Avrami model successfully described the crystallization kinetics. The active energy of nonisothermal crystallization of iPP was determined by the Kissinger method and showed that the addition of nucleating agents increased the activation energy. Melting behavior and crystalline structure of the nucleated iPPs are dependent on the nature of NAs and crystallization conditions. Higher proportion of β-phase can be obtained at higher content of β-nucleating agent and lower crystallization temperature or lower cooling rate.

Restricted access

Abstract

Crystallization behavior of isotactic polypropylene (iPP)/magnesium salt whisker (MSW) composites modified by compatibilizer PP-g-MAH was studied under both isothermal and nonisothermal conditions. Analysis of the isothermal crystallization showed that the Avrami model successfully described the crystallization process. On the basis of Lauritzen–Hoffman theory, a regime transition was observed at about 139 °C for the iPP/MSW composite, and a decrease in the fold surface free energy was calculated with the addition of MSW and PP-g-MAH. The addition of MSW filler and PP-g-MAH compatibilizer distinctly improved the crystallization temperature and accelerated the total crystallization rate of iPP. It was observed that MSW induced the formation of β-iPP but PP-g-MAH suppressed the formation of β-iPP.

Restricted access

Abstract  

The fractional cumulative yields (FCY) of133mTe and133gTe in the spontaneous fission of252Cf were measured for the first time by a radiochemical method. The values ofFCY are 0.533±0.014 and 0.291±0.042 for133mTe and133gTe, respectively. The isomeric state to ground state fractional independent yield (FIY) ratio of133Te,R, was found to be 3.5. The root-mean-square angular momentum of the primary fragment corresponding to the fission product133Te, Jr.m.s.=8.8h, was estimated according to a simple one-parameter statistical model. The fractional cumulative yields from this work together with other literature data in the mass region A=131–141 are compared with the normal yields given by the empiricalZ p model by Whhl. It suggests that both theN=82 neutrons shell and nucleus pairing effects are not apparent for the spontaneous fission of252Cf.

Restricted access