PHYSICAL AGING OF ORGANO-INORGANIC NANOCOMPOSITES BASED ON POLYIMIDE WITH CARD SUBSTITUENTS

2021 ◽  
Vol 43 (4) ◽  
pp. 295-303
Author(s):  
N.V. KOZAK ◽  
◽  
T.A. SHANTALII ◽  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physical Aging ◽  
Sol Gel ◽  
Thermal Relaxation ◽  
Nanocomposite Films ◽  
Molecular Probe ◽  
Inorganic Component ◽  
Inorganic Particles

The physical aging was investigated of obtained by sol-gel technology nanocomposites based on polyimide (PI) with card substituents and tetraethoxysylane (TEOS). The results for organic-inorganic composites, that contain of 5%. 20% or 50 % of TEOS, demonstrate that at temperatures well below (400K) the glass transition temperature of the polymer can take place changes in the dynamic characteristics of polymer macrochains and its permeability to low molecular probe as well as changes in aggregation of inorganic component. According to the methods of EPR, optical microscopy, etc. changes that occur in the characteristics of sol-gel polyimide based nanocomposites during long-term storage at temperatures much lower than the glass transition temperature of the polymer can be described as follows. The segmental mobility of the organic component is significantly reduced and the dynamic heterogeneity of the polymer increases. The decrease in the relative permeability of aged nanocomposites with increased content of inorganic component as compared with aged pure PI does not correlate with the content of TEOS in contrast to the initial samples of the same composition. PI macrochains chemically bonded to the inorganic phase have limited ability to realize an optimal conformation in the process of thermal relaxation (physical aging) so the increasing the content of the inorganic component has less effect on reducing the permeability of aged composites compared to aged pure PI. This is consistent with changes in the distribution of inorganic aggregates of composites. There are changes in the mean size of aggregates of inorganic particles in the composite and a decrease in their number. Smoothing is observed of the surface of nanocomposite films as well as disappearance of inhomogeneities caused by the surface of support. Due to the chemical bonding of inorganic particles and polyimide matrix, the peculiarities of the physical aging process of such composites are due to the mutual influence of the inorganic and polymer components.

scholarly journals Thermal and Mechanical Properties of Chitosan/SiO2Hybrid Composites

2010 ◽  
Vol 2010 ◽  
pp. 1-7 ◽  
Author(s):  
F. Al-Sagheer ◽  
S. Muslim
Keyword(s):  
Electron Microscopy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Energy Dispersive Spectrometer ◽  
Sol Gel ◽  
Chitosan Film ◽  
Silica Content ◽  
Nanocomposite Films ◽  
Maximum Increase

Chitosan-silica (CSSi) hybrid films have been fabricated by sol-gel process using tetraethoxysilane (TEOS) as precursor. The structure of the resulting hybrid has been characterized by Fourier transform infrared spectroscopy (FTIR). Fracture surface has been revealed through a field emission-scanning electron microscopy/energy dispersive spectrometer (FE-SEM/EDS) to probe the dispersion degree and the size ofSiO2particle. Study of morphology using a SEM micrograph and the High Resolution Transmission Electron Microscopy (HRTEM) images of the nanocomposite films suggests that theSiO2nanoparticles are within the range of 2–7 nm in diameter and are uniformly dispersed in the polymer matrix. Thermal properties of these composite materials have been studied as a function of silica, indicating that thermal stability of the chitosan film is enhanced. Dynamical mechanical thermal analysis (DMTA) has been carried out to measure the shift in the glass transition temperature (Tg) of the composites from the maxima of theαtransition curves. The glass transition temperature and the storage modulus show an increase with increasing silica content. The maximum increase in theTgvalue, that is,159.37∘C,is seen with 30 wt% silica. A gradual increase of 3.0 GPa in the modulus relative to the pure polymer is observed.

scholarly journals Physical Aging Behavior of a Glassy Polyether

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 954
Author(s):  
Xavier Monnier ◽  
Sara Marina ◽  
Xabier Lopez de Pariza ◽  
Haritz Sardón ◽  
Jaime Martin ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physical Aging ◽  
Glassy State ◽  
Aging Behavior ◽  
Scanning Calorimetry ◽  
Narrow Temperature Range ◽  
Glass Forming ◽  
Fast Scanning Calorimetry

The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the α relaxation does not hold true when aging is carried out deep in the glassy state.

scholarly journals Physical aging of polycarbonate far below the glass transition temperature: Evidence for the diffusion mechanism

2004 ◽  
Vol 70 (22) ◽  
Author(s):  
D. Cangialosi ◽  
M. Wübbenhorst ◽  
J. Groenewold ◽  
E. Mendes ◽  
H. Schut ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Physical Aging ◽  
Diffusion Mechanism

Isothermal Physical Aging of Poly(ethyl methacrylate)/Polyhedral Oligomeric Silsequioxanes Nanocomposite Thin Films

2011 ◽  
Vol 287-290 ◽  
pp. 2234-2239 ◽  
Author(s):  
Sil Ro Jin ◽  
Jong Keun Lee
Keyword(s):  
Thin Films ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Film Thickness ◽  
Methyl Methacrylate ◽  
Relaxation Function ◽  
Physical Aging ◽  
Pmma Film ◽  
Nanocomposite Thin Films

The effects of the polyhedral oligomeric silsequioxanes (POSS) in stacked poly(methyl methacrylate) (PMMA) film samples were investigated in two different film thicknesses, ~50 and ~660 nm. The types of the POSS include methacryl-, octaisobutyl-, and octasilane-POSS. The glass transition temperature (Tg) and isothermal physical aging was depressed by the reduction of film thickness. Among POSS molecules used in this work, methacryl-POSS was the greatest effect in both Tgand relaxation enthalpy (DHRelax) due to the physical aging. The Kohlrausch-Williams-Watts (KWW) relaxation function was used to further understand the effect of POSS and film thickness on the physical aging.

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