The dynamic crystallization and multiple melting behavior of polypropylene in the in-reactor alloy: A differential scanning calorimetry study

2011 ◽  
Vol 121 (3) ◽  
pp. 1372-1383 ◽  
Author(s):  
Haijin Zhu ◽  
Hengrui Yang ◽  
Ying Zhao ◽  
Dujin Wang
Keyword(s):  
Differential Scanning Calorimetry ◽  
Melting Behavior ◽  
Scanning Calorimetry ◽  
Differential Scanning Calorimetry Study ◽  
Dynamic Crystallization ◽  
Multiple Melting Behavior ◽  
Multiple Melting

Step-Scan DSC Study on the Melting Behavior of Polypropylene/Attapulgite Nanocomposites

2011 ◽  
Vol 284-286 ◽  
pp. 763-768
Author(s):  
Li Li Sun ◽  
Kun Hu ◽  
Lin Chen ◽  
Kang Zheng ◽  
Xing You Tian
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Differential Scanning Calorimetry ◽  
Melting Behavior ◽  
Secondary Crystallization ◽  
Screw Extruder ◽  
Scanning Calorimetry ◽  
Twin Screw ◽  
Multiple Melting ◽  
Scanning Electron

Attapulgite(AT) was modified by grafting with butyl acrylate(BA) via polymerizations initiated by Gamma radiation. The polypropylene(PP)/AT nanocomposites were synthesized via melting extrude in a twin-screw extruder. The thermogravimetry(TG) and scanning electron microscopy (SEM) were used to assess the graft ratio of the hybrid materials and the dispersion of AT, respectively. Step-scan differential scanning calorimetry(SSDSC) was used to study the influence of AT on the crystallization and subsequent melting behavior. The results indicated that PP and PP/AT nanocomposites underwent multiple melting and secondary crystallization processes during heating. The melting behaviours of PP and PP/AT nanocomposites varied with the variation of crystallization temperature and AT content.

Multiple melting behavior of poly(lactic acid)-hemp-silica composites using modulated-temperature differential scanning calorimetry

2014 ◽  
Vol 34 (9) ◽  
pp. 895-903 ◽  
Author(s):  
Izan R. Mustapa ◽  
Robert A. Shanks ◽  
Ing Kong
Keyword(s):  
Differential Scanning Calorimetry ◽  
Heat Capacity ◽  
Lactic Acid ◽  
Melting Behavior ◽  
Woven Fabric ◽  
Melting Peak ◽  
Poly Lactic Acid ◽  
Scanning Calorimetry ◽  
Modulated Temperature ◽  
Multiple Melting

Abstract Poly(lactic acid) (PLA)-hemp-nanosilica (PHS) composites were prepared by impregnation of hemp woven fabric with PLA solution. Nanosilica was dispersed in the PLA solution to introduce a matrix reinforcing nanophase within the composite. The melting behavior of PLA composites was obtained by using differential scanning calorimetry (DSC) and modulated-temperature DSC (mT-DSC). Multiple melting which appeared in the non-isothermal heating curve showed that the temperature of a low melting peak increased when using a slower scanning rate. The incorporation of nanosilica in PLA composites affected the melting temperature (Tm) and sufficiently formed nucleation sites that promoted the growth of PLA crystals. Composites analyzed by a temperature-modulated program showed a broad exothermic peak before the melting peak in the non-reversing heat capacity and endothermic melting in the reversing heat capacity curve. This behavior was explained by a process of partial melting, recrystallization and remelting (mrr). The mT-DSC resolved that hemp fiber induced recrystallization and nanosilica acted as an effective nucleating agent, which promoted small and imperfect crystals that changed successively into more stable crystals through a melt-recrystallization process.

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