Effect of crystallization temperature and molecular weight on the melting temperature of linear polyethylene

1967 ◽  
Vol 71 (12) ◽  
pp. 3833-3841 ◽  
Author(s):  
M. R. Gopalan ◽  
Leo Mandelkern
Keyword(s):  
Molecular Weight ◽  
Melting Temperature ◽  
Crystallization Temperature ◽  
Linear Polyethylene

scholarly journals Raman study of uniaxial deformation of single-crystal mats of ultrahigh molecular weight linear polyethylene

2015 ◽  
Vol 594 ◽  
pp. 012010 ◽  
Author(s):  
Yu V Zavgorodnev ◽  
S N Chvalun ◽  
G Yu Nikolaeva ◽  
E A Sagitova ◽  
P P Pashinin ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Single Crystal ◽  
Uniaxial Deformation ◽  
Linear Polyethylene ◽  
Ultrahigh Molecular Weight ◽  
Raman Study

Effects of Molecular Weight of Chitosan on the Biodegradability and Thermal Properties of Polybutylene Succinate/Chitosan Composites

2018 ◽  
Vol 775 ◽  
pp. 26-31
Author(s):  
Sukantika Manatsittipan ◽  
Kamonthip Kuttiyawong ◽  
Kazuo Ito ◽  
Sunan Tiptipakorn
Keyword(s):  
Molecular Weight ◽  
Weight Loss ◽  
Thermal Properties ◽  
Water Absorption ◽  
Melting Temperature ◽  
Microbial Degradation ◽  
Decomposition Temperature ◽  
Molecular Weights ◽  
Significant Difference ◽  
Polybutylene Succinate

In this study, the biodegradability and thermal properties the composites of polybutylene succinate (PBS) and chitosan of different molecular weights (Mn = 104,105, and 106 Da) were prepared at chitosan contents of 0-10 wt%. After 10 days of microbial degradation, the results show that the amount of holes from degradation was increased with either decreasing Mn or increasing chitosan contents. However, the size of holes was increased with increasing Mn and chitosan contents. The results from Differential Scanning Calorimeter (DSC) present that the melting temperature (Tm) of PBS was decreased with increasing chitosan contents. Moreover, there was no significant difference between Tm of the composites with different Mn of chitosan. From the TGA thermograms, the decomposition temperature at 10% weight loss (Td10) was decreased with increasing chitosan contents. Moreover, the water absorption of PBS/chitosan composites was increased with increasing Mn and content of chitosan.

On the morphology of melt-crystallized polyethylene - II. Lamellae and their crystallization conditions

1981 ◽  
Vol 377 (1768) ◽  
pp. 39-60 ◽  
Keyword(s):  
Molecular Mass ◽  
Crystallization Temperature ◽  
Lamellar Thickness ◽  
Kinetic Regime ◽  
Secondary Nucleation ◽  
Constant Multiple ◽  
Linear Polyethylene ◽  
Simple Assumption ◽  
Crystallization Conditions ◽  
Prevalent Form

The microstructure of melt-crystallized linear polyethylene has been correlated with the variables of crystallization for most readily attainable conditions. All samples are filled with well defined lamellae with an aver­age chain inclination of about 35° to lamellar normals. The lamellar thickness depends upon supercooling rather than directly on crystalliza­tion temperature, which indicates that it is a kinetically determined quantity. The simple assumption that it is a constant multiple of the height given by secondary nucleation is, however, incorrect. Lamellar profiles depend only upon the crystallization temperature and molecular mass of the polyethylene concerned. They are independent of the extent of spherulitic development and are not determined solely by the kinetic régime in which crystals grow. Dominant S-shaped lamellae (Ss) and their associated subsidiary platelets are, nevertheless, the prevalent form for crystallization within régime II, i. e. in most cases of practical import­ance. The distinction between dominant and subsidiary lamellae is linked to fractional crystallization. At low supercoolings it is shown that shorter molecules are concentrated within subsidiary lamellae, and the trend to separate later-crystallizing species is likely to persist, to a lesser degree, even to quenched samples. With the use of added branched molecules this has been demonstrated to occur. The consequences of spatial segre­gation are likely to include increased vulnerability to mechanical and environmentally induced failure.

scholarly journals The nanostructuring of ultra-high-molecular-weight polyethylene in thermal and mechanical fields as revealed by DSC

2021 ◽  
Vol 2103 (1) ◽  
pp. 012095
Author(s):  
L P Myasnikova ◽  
A K Borisov ◽  
Yu M Boiko ◽  
A P Borsenko ◽  
V F Drobot’ko ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Melting Temperature ◽  
Mechanical Characteristics ◽  
Thickness Distribution ◽  
High Strength ◽  
High Modulus ◽  
Know How ◽  
First Time ◽  
Ultra High Molecular Weight

Abstract The ultra-high-molecular-weight polyethylene reactor powders are widely used for the actively developing solvent-free method for producing high-strength high-modulus PE filaments, which includes the compaction and sintering of a powder followed by orientational hardening. To find an appropriate regime of the technological process, it is important to know how the nanostructure changes when transforming from a powder to a precursor for hardening. Nanocrystalline lamellae are characteristics of the powder structure. For the first time, the DSC technique was used to follow changes in the thickness distribution of lamellae in ultra-high-molecular-weight polyethylene reactor powder on its way to a precursor for orientation hardening. It was found that the percentage of thick (>15 nm) and thin (10 nm) lamellae in compacted samples and those sintered at temperatures lower than the melting temperature of PE (140°C) remains nearly the same. However, significant changes in the content of lamellae of different thicknesses were observed in the samples sintered at 145°C with subsequent cooling under different conditions. The influence of the lamellae thickness distribution in precursors on the mechanical characteristics of oriented filaments was discussed.

Preparation and characterization of high molecular weight poly(trimethylene terephthalate) by solid-state polymerization

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Kim Seok Hoon ◽  
Kim Joon Ho
Keyword(s):  
Molecular Weight ◽  
Reaction Time ◽  
Solid State ◽  
High Molecular Weight ◽  
Melting Temperature ◽  
Average Molecular Weight ◽  
Pellet Size ◽  
Solid State Polymerization ◽  
Trimethylene Terephthalate ◽  
High Molecular Weight Poly

AbstractSolid-state polymerization has been widely used to prepare high molecular weight poly(ethylene terephthalate). Solid-state polymerization is generally carried out by heating solid, melt-phase-polymerized polymer below its melting temperature but above its glass transition temperature. Solid-state polymerization of poly(trimethylene terephthalate)(PTT) is not an independent process but rather an additional process with respect to melt polymerization that is used when PTT of a higher molecular weight is required. Two kinds of commercial PTT chips were polymerized in the solid state to prepare high molecular weight PTT, which were characterized by end group contents, molecular weight, thermal analysis and X-ray diffraction. In the solid-state polymerization of PTT, the overall reaction rate was governed by the reaction temperature, reaction time and pellet size. The content of carboxyl end groups was decreased during the solid-state polymerization with increasing reaction time and temperature. The melting temperature and crystallinity of solid-state-polymerized PTT were higher at longer times and higher temperatures of polymerization. The activation energy for the solid-state polymerization of PTT was in the range of 24~25 kcal/mol for each chip. Through the solid-state polymerization of commercial PTT chips, we could get high molecular weight polymers up to an intrinsic viscosity value of 1.63 dl/g, which is equivalent to about a 117,000 weight-average molecular weight.

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