The Influence of the Degree of Crystallinity on the Glass Transition Temperature of Polymers

2013 ◽  
Vol 864-867 ◽  
pp. 751-754 ◽  
Author(s):  
Andrey Askadskii ◽  
Marina Popova ◽  
Tatyana Matseevich ◽  
Elena Kurskaya
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Degree Of Crystallinity ◽  
Low Degrees ◽  
The Degree Of Crystallinity

The influence of the degree of crystallinity of polymers on the glass transition temperature Tg of their amorphous domains is quantitatively analyzed. The analysis is made based on the Mandelkerns ideas [ concerning the restrictive effect of crystallization on the mobility of macromolecules within the amorphous domains. At low degrees of crystallinity, Tg of amorphous domains slowly increases, and then increases much faster at high degrees of crystallinity.

The Effect of Methylene Diphenyl Diisocyanate on the Nonisothermal Properties of Polylactic Acid/Elaeis guineensis Fibres Biocomposites

2013 ◽  
Vol 594-595 ◽  
pp. 823-827
Author(s):  
Luqman Hakim Ahmad Subri ◽  
Sakinah Mohd Alauddin ◽  
Senawi Rosman
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Polylactic Acid ◽  
Elaeis Guineensis ◽  
Fibre Surface ◽  
Degree Of Crystallinity ◽  
Chain Mobility ◽  
Methylene Diphenyl Diisocyanate ◽  
The Degree Of Crystallinity

Biocomposites demands are significantly rising due to environmental regulations and concerns. However, incompatibility between the fibre and matrix is a major setback that diminishes the biocompostie properties. Therefore in this work, methylene diphenyl diisocynate (MDI) compatibilizers were used together with fibre surface treatment in order to increase compatibility between polylactic acid (PLA) and Elaeis Guineensis Fibres (EGF) biocomposite. Nonisothermal properties were investigated and it was found that, MDI increased compatibility of the PLA and EGF which led to the restriction of chain movements in the biocomposite. This restriction in chain mobility caused an increase the glass transition temperature and crystallization temperature and also reduced the degree of crystallinity.

Uniaxial Stretching above the Glass Transition Temperature of Poly(Ethylene Terephthalate) and its Effects on the Structure Development

2008 ◽  
Vol 587-588 ◽  
pp. 529-533
Author(s):  
Lyudmil V. Todorov ◽  
Olga M. Freire ◽  
Júlio C. Viana
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Ethylene Terephthalate ◽  
Degree Of Crystallinity ◽  
Structure Development ◽  
Scanning Calorimetry ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
Stretching Ratio

This work deals with an experimental investigation of the strain-induced crystalline microstructure that develops under uniaxial elongation of amorphous poly(ethylene terephthalate), PET, above its glass transition temperature, as an approach for industrial stretch-blow moulding processes. The present study aims at: a) defining the most relevant processing parameters which govern and are of significance for the induced morphology, and b) establishing of relationships between processing and morphology. Compression moulded amorphous PET was uniaxial stretched with variations of following stretching parameters: stretching temperature, Tst, stretching velocity, Vst, and stretching ratio, λst, that were varied in two levels according to a L8 Taguchi orthogonal array. The developed morphologies were characterized by differential scanning calorimetry (DSC) and birefringence measurements. Obtained results were analyzed by ANOVA statistical tool. The glass transition temperature, Tg, is influenced mainly by the stretching ratio. The cold crystallization temperature, Tcc, is determined by complex influence of all stretching variables and the interaction Tstxλst. The degree of crystallinity, χc, mainly depends upon Vst and Tstxλst interaction. The birefringence, n, is essentially determined by λst and the interaction Vstxλst. The distinct morphological parameters are then related with the purpose of understand the structure development upon polymer stretching.

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