Authors:Zhiyong Wei, Wanxi Zhang, Guangyi Chen, Jicai Liang, Shu Yang, Pei Wang, and Lian Liu
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
Authors:Yuhai Wang, Hao Shen, Gu Li, and Kancheng Mai
interaction between particles and polymer matrix, and then influences the crystallization and meltingbehavior of polymer composites. It is found that nano-CaCO 3 particles treated with nonionic modifier increased the crystallization rate of PP matrix [ 11
Authors:Bo Song, Yong Wang, Hongwei Bai, Li Liu, Yanli Li, Jihong Zhang, and Zuowan Zhou
]. Here, we attempted to research the nucleation effect of TMB-5 on crystallization of PP-MA. The β-crystallization tendency of PP-MA has been reported recently [ 15 ]. Isothermal and nonisothermal crystallization behaviors and subsequent meltingbehaviors
Authors:M. Gazzano, M. Soccio, N. Lotti, L. Finelli, and A. Munari
phase, the so called “rigid-amorphous phase” (RAP) or “inter-phase” between crystalline and amorphous layers has to be taken into consideration in these structures. In this view, herein the meltingbehavior and the isothermal crystallization kinetics of
isothermal crystallization and meltingbehavior of WF/PP composites, especially in the presence of m -TMI- g -PP. Therefore, fundamental studies on the effect of the presence of WF and with m -TMI- g -PP as a compatibilizer on the crystallization and
differential scanning calorimetry, the melting behaviour of poly(oxytetramethylene)-alt-(aromatic oligoamide) (POTM-alt-AOA)
has been studied in comparison with that of polyoxytetramethylene glycohols
(POTMGs). The apparent melting temperature of the block copolymers is found
to be less than that of the corresponding POTMGs by approximately 30°C.
The relaxation time of melting of a POTM segment has been estimated and compared
with that of POTMG. The relaxation time of POTM-alt-AOA
is slightly shorter than that of POTMG when the molar mass of the POTM segment
is 2900; however, it is longer when the molar mass is 1400.
Fish oil which is characterised by important amounts of poly-unsaturated ω-3 fatty acids attach increasing importance within
functional foods. Recently attention is directed on physical methods that allow fast and relatively easy the identification
and discrimination of oils. DSC measurements yield in information on thermal effects, characterised by changes in enthalpy
and their temperature range such as melting and crystallisation. The aim of the investigation presented here was to take DSC
curves in the temperature range +20 to −40°C on several fish oils and fish oil capsules to visualise the crystallisation and
melting behaviour and to compare transition temperatures and enthalpies.
Authors:H. Fretwell, J. Duffy, M. Alam, and R. Evans
In this paper we present our recent positron annihilation study of the liquid»solid phase boundary for CO2 confined in nanometer pores of VYCOR glass. We find that CO2 remains liquid in the pores far below the bulk freezing temperature and there is pronounced hysteresis between freezing and melting compared to that seen at the gas-liquid boundary in the pores. On freezing we see evidence of open space created in the pores. This leads to complex melting behaviour possibly involving the formation of gas-liquid interfaces. We see that frezing in the pores is totally irreversible, so that any solid which forms (no matter how small) remains stable up to the higher melting temperature. In contrast melting is more reversible (possibly indicating nucleation centres which permit immediate re-freezing). Finally, the pre-frozen state in the pores is different to the post-melted state.
Authors:M. Lappalainen, I. Pitkänen, H. Heikkilä, and J. Nurmi
enantiomeric forms of xylose were identified as α-D-xylopyranose
and α-L-xylopyranose by powder diffraction.
Their melting behaviour was studied with conventional DSC and StepScan DSC
method, the decomposition was studied with TG and evolved gases were analyzed
with combined TG-FTIR technique. The measurements were performed at different
heating rates. The decomposition of xylose samples took place in four steps
and the main evolved gases were H2O, CO2
and furans. The initial temperature of TG measurements and the onset and peak
temperatures of DSC measurements were moved to higher temperatures as heating
rates were increased. The decomposition of L-xylose
started at slightly higher temperatures than that of D-xylose
and L-xylose melted at higher temperatures
than D-xylose. The differences were more
obvious at low heating rates. There were also differences in the melting temperatures
among different samples of the same sugar. The StepScan measurements showed
that the kinetic part of melting was considerable. The melting of xylose was
anomalous because, besides the melting, also partial thermal decomposition
and mutarotation occurred. The melting points are affected by both the method
of determination and the origin and quality of samples. Melting point analysis
with a standardized method appears to be a good measure of the quality of
crystalline xylose. However, the melting point alone cannot be used for the
identification of xylose samples in all cases.
The effect of the dyeing on the melting behavior of poly(lactic acid) fabrics was investigated by differential scanning calorimeter.
The DSC melting peaks at 10C min-1 of the untreated poly(lactic acid) fabric were observed at a temperature higher than those of the dyed fabrics. The restricting
force from the extended tie molecules along the fiber axis seems to decrease in the dyeing process. When the sample was rapidly
heated, the crystallites melted at lower temperatures since recrystallization was restricted. It was estimated, based on the
heating-rate dependency of melting behavior, that the original crystallites of the untreated sample melted at 146.1C and
those of the dyed samples melted at higher temperatures, suggesting that their crystallites are grown to be more perfect in
the dyeing process.