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.

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.

Microstructures and Mechanical Properties of Melt Spinning Spandex

2014 ◽  
Vol 1048 ◽  
pp. 36-40
Author(s):  
Wei Lai Chen ◽  
Lin Yan Wan ◽  
Hong Qin
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Heat Treatment ◽  
Scanning Electron Microscopy ◽  
Tensile Strength ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Melt Spinning ◽  
Scanning Electron

Microstructures and mechanical properties of melt spinning spandex were studied in this article.Cross section and longitudinal surface were observed and analyzed by JSM-5610LV scanning electron microscopy. Q2000 DSC differential scanning calorimeter was used to test the glass transition temperature and melting temperature which indicated glass transition temperature is about 44°C and melting temperature is about 200°C. We employed JSM-5610LV scanning electron microscopy to observe adhesion of melt spinning spandex with nylon filament after different time and temperature processing. It concluded that after 150°C90s、160°C60s、160°C90s、170°C30s heat treatment, the adhesive of melt spinning spandex with nylon is good. At the same time,tensile strength and elastic properties of melt spinning spandex which was processed under different time and temperature were tested, tensile strength and elastic recovery of melt spinning spandex after160°C 90s heat treatment is the best.

Cryomicroscopy of Latex and Latex Films

2000 ◽  
Vol 6 (S2) ◽  
pp. 316-317
Author(s):  
O. L. Shaffer ◽  
M. S. El-Aasser
Keyword(s):  
Electron Microscopy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Low Temperature ◽  
Protective Coatings ◽  
Continuous Film ◽  
The Core ◽  
Film Forming ◽  
Water Uses

Latexes are dispersions of homopolymers and copolymers, usually in water. Uses of these latexes are many such as protective coatings and adhesives. In order to form a continuous film the polymer must have film forming properties such as a low glass transition temperature (Tg). Latexes are being designed such as one polymer in the core of the particle and a shell of another polymer or perhaps a series of shell layers. Microscopy has become a powerful tool in the examination of the morphology of the latex particles. Because of the use of low Tg polymers, sample preparation and examination by electron microscopy at temperatures above the Tg of the polymer causes the particles to become distorted and no longer representative of their true morphology. Low temperature methods therefore have become crucial in the field of latex microscopy.

Poly(methyl methacrylate)–nanoribbon nanocomposites with high thermal stability and improvement in the glass-transition temperature

2007 ◽  
Vol 22 (12) ◽  
pp. 3316-3323 ◽  
Author(s):  
Yanyan Ding ◽  
Zhou Gui ◽  
Jixin Zhu ◽  
Zhengzhou Wang ◽  
Yuan Hu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Methyl Methacrylate ◽  
Network Formation ◽  
Nanocomposite Films ◽  
Host Matrix ◽  
Poly Methyl Methacrylate ◽  
Inorganic Content

A novel poly(methyl methacrylate) (PMMA) nanocomposite containing dispersed inorganic nanoribbons [ZnO–0.15Zn(CH3COO)2–0.85H2O] was prepared by free radical polymerization of methyl methacrylate in the acetone solution. Experimental results showed that inorganic nanoribbons were uniformly distributed in and bonded to the PMMA host matrix without macroscopic organic–inorganic phase separation. It was found that the thermal stability and glass-transition temperature of the nanocomposite films increased effectively with increasing inorganic content at low content and remained above 1 wt% inorganic content. These results suggest the network formation because of the strong interaction between the inorganic nanoribbons and the polymer matrix, which induces the mobility restriction of polymer chains. The characteristics of the one-dimensional inorganic nanoribbons we used here may play a key role in the formation of the “cross-link” networks and in the decision to lower the content of the inorganic nanoribbon additive.

scholarly journals New casting glass technique through the use of geopolymers

2019 ◽  
Vol 274 ◽  
pp. 03004
Author(s):  
Jorge Duran-Suarez ◽  
Maria-Angeles Villegas ◽  
Rafael Peralbo-Cano ◽  
Joâo Castro Gomes
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Water Glass ◽  
Silica Content ◽  
Mechanical Resistance ◽  
Glass Waste ◽  
Recycled Glass ◽  
Heat Treated ◽  
High Temperature Processing

By using silicate inorganic binders and glass waste (colourless or coloured) it is possible to mould technical and artistic elements, which later can be hardened by means of high temperature processing. This procedure is controlled by both the glass transition temperature of binder and of glass waste used as aggregate. "water glass", catalysed with sodium hydroxide was used as a binder of glass shards from common industrial bottles, classified to a grain size distribution below 2 mm. Chemical analysis shows similarity of silica content between binder and aggregates of recycled glass, establishing as main differences in the percentages of chromophore oxides. In addition dilatometry curves of the two materials show close glass transition temperature values (575 and 598 °C, respectively), fact that facilitates sintering between binder and aggregates. The non-heat-treated samples present good compactness and mechanical resistance values, improved with heat-treatment at 700 °C. The high compactness of heated samples, showing rounded aggregate grains and softening of binder could let a good way for obtaining well-consolidated technical elements, made of recycled glass. From this test, it would be possible to use thermal ranges between 550 and 600 °C, as well as shorter exposure times for a proper hardening.

Structure-property behavior during aging of sol-gel-derived silica modified with Si–H and Si–CH3 groups

1999 ◽  
Vol 14 (5) ◽  
pp. 2100-2106 ◽  
Author(s):  
Vincenzo M. Sglavo ◽  
Sandra Diré ◽  
Maurizio Ferrari
Keyword(s):  
Refractive Index ◽  
Glass Transition ◽  
Elastic Modulus ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Sol Gel ◽  
Network Evolution ◽  
Structure Property ◽  
Pore Liquid ◽  
Physical And Mechanical Characteristics

Unsupported films and thin rods were prepared by the sol-gel method from solutions of triethoxysilane and methyldiethoxysilane. Measurements of elastic modulus, density, glass transition temperature, and refractive index were performed at different aging times. Results showed a large increase of the elastic modulus with aging time, which was related to the progressive condensation taking place in the xerogel network, as shown by solid-state nuclear magnetic resonance (NMR). The stiffness increase was shown to correspond to higher glass transition temperature and larger density and refractive index. Different increasing rates of the physical and mechanical characteristics were observed for films and rods during aging. This behavior was related to the different loss rate of the pore liquid, which affects the network evolution in the wet gel.

scholarly journals Synthesis and Thermal Characterization of PMMA-TiO2 Nanocomposites

2014 ◽  
Vol 11 (2) ◽  
pp. 168-172 ◽  
Author(s):  
Shalini Agarwal ◽  
Vibhav Saraswat
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Tio2 Nanoparticles ◽  
Average Particle Size ◽  
Research Work ◽  
Weight Percent ◽  
Nanocomposite Films ◽  
Average Particle ◽  
Scanning Calorimetry

In present research work, nanocomposite films of organic polymeric matrix polymethylmethacrylate (PMMA) and its nanocomposites with inorganic nanosized filler, namely titania (TiO2) nanoparticles, have been prepared and characterized thermally. TiO2 nanoparticles have been synthesized by chemical route method. Formation of nanoparticles and their average size have been confirmed by Transmission Electron Microscopy (TEM). The average particle size of the nanoparticles has been found to be ~19 nm. PMMA-TiO2 nanocomposites with different TiO2 weight percent (e.g. 1%, 2% and 3%) have been prepared by solution casting technique. These prepared samples have been investigated by means of Differential Scanning Calorimetry (DSC) at different heating rates. The effect of heating rate and TiO2 weight percent on glass transition temperature (Tg) and melting temperature (Tm) have been studied. It has been found that Tg and Tm increases as TiO2 content increases in PMMA matrix. An effort has also been made to calculate activation energy at glass transition temperature using Kissinger, Moynihan and Lasocka relations.

Sign in / Sign up

Export Citation Format

Share Document