Effect of Morphology and Chemical Modification on Water Degradation Behavior of Polyvinyl Alcohol - Gelatin Blend

2016 ◽  
Vol 705 ◽  
pp. 82-86 ◽  
Author(s):  
Jopeth M. Ramis ◽  
Bryan B. Pajarito

Polyvinyl Alcohol - Gelatin (PVAG) nanofibers were successfully synthesized using the electrospinning method. After synthesis, the degradation study of electrospun PVAG nanofibers was done using Quartz Crystal Microbalance submerged in distilled water at ambient conditions. Additional samples were prepared: PVAG film, and cross-linked PVAG nanofibers using 37% formaldehyde vapor, to analyze the effects of the morphology and chemical modification on the degradation property of PVAG blend. Results revealed significant differences in the degradation properties of different samples. PVAG film exhibited initial mass loss at the beginning but afterwards began to uptake water from the environment, achieving steady state value. PVAG nanofibers' behavior was in a continuous mass loss behavior in contrast to the film morphology, probably due to its large surface area exposed to the aqueous environment that readily solubilized PVA and gelatin components of the nanofibers. Analysis on the PVAG cross-linked nanofibers showed degradation profile comparable to a damped sinusoid function, achieving a pseudo steady-state profile after considerable time. Evidence from QCM studies show that morphology and chemical modification has an effect on the degradation property of PVAG, and further tuning of these effects could be utilized for functional use in tissue engineering, drug delivery systems, and other chemical and biomedical use.

1979 ◽  
Vol 83 ◽  
pp. 151-154
Author(s):  
Sun Kwok ◽  
C. R. Purton

A program to search for steady-state thermal emissions from stars has been in progress for several years in Canada (Purton 1976). In this program we have specifically excluded flaring objects (such as β Lyr or HR1099) where non-thermal emission is probably responsible. Out of the 30 or so detections, about 1/4 of them show a ~+1 spectral index, suggesting a 1/r2 density profile in the emitting region. This implies the existence of a non-static circumstellar envelope which is mostly likely the result of continuous mass outflow.


2021 ◽  
Author(s):  
Hongchen Liu ◽  
Hongying Yang ◽  
Kunkun Zhu ◽  
Fang Peng ◽  
Lei Guo ◽  
...  

Excessive exposure to ultraviolet (UV) light is harmful to human health. However, the traditional preparation of anti-UV films through doping UV absorbers is unstable. Chemical modification of polyvinyl alcohol (PVA)...


2018 ◽  
Vol 31 (4) ◽  
pp. 569-574
Author(s):  
Sho Fujisawa ◽  
Masumi Yamamoto ◽  
Daiki Kashiwai ◽  
Pedram Azari ◽  
Ying Ying Khaw ◽  
...  

2016 ◽  
Author(s):  
Yusril Yusuf ◽  
Nur Mufidatul Ula ◽  
Khannah Jahidah ◽  
Ervanggis Minggar Kusumasari ◽  
Kuwat Triyana ◽  
...  

1974 ◽  
Vol 192 ◽  
pp. 429 ◽  
Author(s):  
D. Nelson Limber
Keyword(s):  

1989 ◽  
Vol 114 ◽  
pp. 507-510
Author(s):  
Mariko Kato ◽  
Hideyuki Saio ◽  
Izumi Hachisu

AbstractThe growth rate of a white dwarf which accretes hydrogen-rich or helium matter is studied. If the accretion rate is relatively small, unstable shell flash occurs and during which the envelope mass is lost. We have followed the evolutions of shell flashes by steady state approach with wind mass loss solutions to determined the mass lost from the system for wide range of binary parameters. The time-dependent models are also calculated in some cases. The mass loss due to the Roche lobe overflow are taken into account. This results seriously affects the existing scenarios on the origin of the type I supernova or on the neutron star formation induced by accretion.


1981 ◽  
Vol 59 ◽  
pp. 345-346
Author(s):  
A. Harpaz ◽  
A. Kovetz

The evolution of a 1.2Mʘ star along the asymptotic branch with continuous mass loss is presented, showing that this mass loss leads to the formation of a PN with a typical central star in its center.A former investigation (Harpaz and Kovetz, 1980) has shown that mechanisms for PN creation based on sudden violent processes are not likely to work in the envelope of a red giant star. On the other hand, significant mass loss from red giants was observed as a general phenomenon.We have followed the evolution of a 1.2Mʘ star along the asymptotic branch, including in the evolutionary calculations a mass loss according to Reimers’ empirical formula. It was found that towards the end of this stage, the mass loss rate was about 2.7xl0-6Mʘ/y, which is consistent with the formation of a typical PN within 30,000 years. When the mass content of the hydrogen rich envelope dropped to 1.5x10-3Mʘ, the star began to contract rapidly, forming a typical central star of 0.6Mʘ


2020 ◽  
pp. 002199832096979
Author(s):  
Fatih Yıldırım ◽  
Necati Ataberk ◽  
Mürsel Ekrem

In this study, the thermal and mechanical properties of nanocomposite materials were investigated. Produced nanocomposite materials are epoxy-based and reinforced with Multiwalled Carbon Nano Tube dopped polyvinyl alcohol (PVA) nanofibers. Nanofibers were produced by the electrospinning method. Nanofibers were used for reinforcement as 5, 10, and 15 number of layers. These nanocomposite materials were subjected to uniaxial tensile tests at constant tensile speed in accordance with ASTM D882-02 standards. Tensile strength, elasticity modulus, Poisson's ratio, and toughness values were obtained and these values were compared with the values of reference pure epoxy samples without the nanofiber. For obtaining the thermal properties of the samples Thermogravimetric and Differential Thermal Analysis were performed. In order to investigate the damage mechanisms, the fractured tensile test specimens' surfaces were visualized by Scanning Electron Microscopy. Mechanical and thermal properties of the epoxy were improved by using the PVA nanofibers dopped the MWCNT.


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