Pulsed n.m.r. studies of the crystallization kinetics of polyethylene from the melt and solution

1979 ◽  
Vol 367 (1730) ◽  
pp. 343-351 ◽  
Keyword(s):  
Induction Period ◽  
Crystallization Kinetics ◽  
Volume Change ◽  
Crystallization Time ◽  
Rapid Crystallization ◽  
Amorphous Fraction ◽  
Melting Temperatures ◽  
Solution Crystallization ◽  
Kinetics Of

Pulsed n.m.r. techniques have been used to determine the crystallization rates of polyethylene samples, both commercial polydispersed and monodispersed, in bulk and in approximately 5 % (by mass) solution in tetrachloroethylene. Where comparable, the results agree well with those obtained by Mandelkern (1956)using volume change measurements, but extend his temperature range towards the more rapid crystallization rates. The crystallization-time curves show the existence of an induction period, and a residual amorphous fraction which is lower in solution crystallization. The results agree well with the relation between bulk crystallization rates and degree of supercooling proposed by Mandelkern et al. (1954) provided appropriate melting temperatures,T m , are used. The technique has several advantages for the determination of polymer crystallization rates.

Study on the Crystallization Kinetics of Polymer Thin Films

2012 ◽  
Vol 466-467 ◽  
pp. 102-105
Author(s):  
Yi Jin Ren
Keyword(s):  
Thin Film ◽  
Growth Rate ◽  
Film Thickness ◽  
Crystallization Kinetics ◽  
Crystallization Time ◽  
Crystal Thickness ◽  
Polymer Thin Film ◽  
Crystal Growth Mechanism ◽  
The Relationship ◽  
Kinetics Of

The crystallization kinetics of polymer thin film has a great difference from that in the bulk. Generally, the growth rate of the crystal confined in thin film reduces with decreasing film thickness, which is believed that the interaction between chains and substrate is responsible for the decrease of the growth rate. In addition, the ratio of film thickness over crystal thickness is also a key parameter in determining the growth rate. The relationship between the crystal lateral size and the crystallization time also dominates the crystal growth mechanism in polymer thin film.

The Non-Isothermal Crystallization Kinetics of Dispersible Nano-SiO2/PA66 Composites

2012 ◽  
Vol 535-537 ◽  
pp. 94-102
Author(s):  
Lei Jia ◽  
Li Ping Guo ◽  
Xiang Min Xu
Keyword(s):  
Crystallization Kinetics ◽  
Isothermal Crystallization ◽  
Activation Energies ◽  
Crystallization Time ◽  
Dsc Analysis ◽  
Screw Extruder ◽  
Isothermal Crystallization Kinetics ◽  
Melt Compounding ◽  
Twin Screw ◽  
Kinetics Of

The PA66-based composites containing dispersible nano-SiO2 (DNS) were prepared in a twin-screw extruder by melt compounding. The microstructures of dispersible nano-SiO2/PA66 composites were investigated by means of TEM and XRD, and the non-isothermal crystallization behavior was studied through Jeziorny method and Mo method based on DSC analysis. The results showed that the dispersion of DNS was uniform in PA66 matrix, which could be related to surface structure of dispersible nano-SiO2. It was found from the study of the non-isothermal crystallization kinetics that dispersible nano-SiO2 possessed a heterogeneous nucleation capability in PA66 matrix, and its addition could hinder the motion of PA66 molecular chain, lower the crystallization temperature, and prolong the crystallization time of PA66. In addition, the activation energies for non-isothermal crystallization of neat PA66 and composites were also evaluated by the Kissinger method. The result showed that the activation energies of dispersible nano-SiO2/PA66 composites were higher than that of neat PA66.

Isothermal Crystallization Kinetics of Polypropylene and Hyperbranched Polyester Blends

2011 ◽  
Vol 396-398 ◽  
pp. 1688-1691
Author(s):  
Qing Chun Fan ◽  
Fei Hong Duan ◽  
Huai Bing Guo ◽  
Tian Wu
Keyword(s):  
Crystallization Kinetics ◽  
Isothermal Crystallization ◽  
Crystallization Rate ◽  
Nucleating Agent ◽  
Interfacial Free Energy ◽  
Crystallization Time ◽  
Hyperbranched Polyester ◽  
Isothermal Crystallization Kinetics ◽  
Half Crystallization Time ◽  
Kinetics Of

The isothermal crystallization kinetics of PP with different contents of AB2 hyperbranched polyester(HBP) added has been investigated. The results show that HBP acts as a nucleating agent for PP, and the hyperbranched polyester can decrease the half crystallization time (t1/2) and increase the crystallization rate of PP greatly. The Avrami exponents of PP and nucleated PP are all close to 2.5. Hoffman theory was adopted to calculate the interfacial free energy per unit area perpendicular to PP chains σe of PP and PP/HBP blends.

scholarly journals Nonisothermal Crystallization Kinetics of Acetylated Bamboo Fiber-Reinforced Polypropylene Composites

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1078 ◽  
Author(s):  
Yu-Shan Jhu ◽  
Teng-Chun Yang ◽  
Ke-Chang Hung ◽  
Jin-Wei Xu ◽  
Tung-Lin Wu ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Crystallization Kinetics ◽  
Crystallization Rate ◽  
Bamboo Fiber ◽  
Crystallization Time ◽  
Nucleation Agent ◽  
Relative Crystallinity ◽  
Crystallinity Degree ◽  
Friedman Method ◽  
Kinetics Of

The crystallization behavior of bamboo fiber (BF) reinforced polypropylene (PP) composites (BPCs) was investigated using a differential scanning calorimeter (DSC). The results showed that unmodified BF as a nucleation agent accelerated the crystallization rate of the PP matrix during cooling whereas there is no significant effect on the improved crystallization rate in BPCs with acetylated BFs. Based on the Avrami method, Avrami–Ozawa method, and Friedman method, the corresponding crystallization kinetics of PP reinforced with different acetylation levels of BFs were further analyzed. The results demonstrated that the crystal growth mechanism of the PP matrix for BPCs with unmodified and various acetylated BFs exhibited tabular crystal growth with heterogeneous nucleation. A higher cooling rate is required to achieve a certain relative crystallinity degree at the unit crystallization time for BPCs with a higher weight percent gain (WPG) of acetylated BFs (WPG >13%). Furthermore, based on the Friedman method, the lowest crystallization activation energy was observed for the BPCs with 19% WPG of acetylated BFs.

Effect of surface-modified zinc oxide nanowires on solution crystallization kinetics of poly(3-hexylthiophene)

Polymer ◽  
2014 ◽  
Vol 55 (8) ◽  
pp. 2008-2013 ◽  
Author(s):  
Taylor W. Wagner ◽  
Yanqi Luo ◽  
Neil D. Redeker ◽  
Chad E. Immoos ◽  
Shanju Zhang
Keyword(s):  
Zinc Oxide ◽  
Crystallization Kinetics ◽  
Zinc Oxide Nanowires ◽  
Oxide Nanowires ◽  
Solution Crystallization ◽  
Surface Modified ◽  
Kinetics Of ◽  
Effect Of Surface
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