SYNTHESIS AND THERMAL CROSSLINKING OF p-TOLYL CONTAINING POLYQUINOXALINES

1977 ◽  
pp. 125-137
Author(s):  
Stanley E. Wentworth
Keyword(s):  
Thermal Crosslinking

Enhanced CO2 permeability of thermal crosslinking membrane via sulfonation/desulfonation of phenolphthalein-based cardo poly(arylene ether ketone)

2020 ◽  
Vol 598 ◽  
pp. 117824 ◽  
Author(s):  
Ruisong Xu ◽  
Lin Li ◽  
Mengjie Hou ◽  
Jiajia Xue ◽  
Yuzhe Liu ◽  
...  
Keyword(s):  
Arylene Ether ◽  
Thermal Crosslinking ◽  
Ether Ketone

scholarly journals Comparison of Single and Double-Network PVA Pervaporation Performance: Effect of Operating Temperature

2020 ◽  
Vol 64 (3) ◽  
pp. 377-383
Author(s):  
Asmaa Selim ◽  
András József Tóth ◽  
Enikő Haáz ◽  
Dániel Fózer ◽  
Péter Mizsey
Keyword(s):  
Operating Temperature ◽  
Sorption Process ◽  
Ethanol Solution ◽  
Sequential Method ◽  
Ethanol Mixture ◽  
Performance Effect ◽  
Double Network ◽  
Thermal Crosslinking ◽  
High Ethanol ◽  
And Diffusion

Thermal crosslinking sequential method applied for DN-PVAs generation efficiently. The swelling measurements investigated that the hydrophilicity of the membrane decreases because of the collaboration of the second thermal crosslinked PVA matrix. The dehydration performance of ethanol solution showed improved using the thermal crosslinked double network PVA membrane. The pervaporation dehydration of the water-ethanol mixture was investigated at different conditions. The separation selectivity showed a significant improvement, while the permeation flux declines due to the incorporation of the second PVA network under 95 % ethanol and at 40 °C. Increasing the feed temperature enhanced the permeability of the membrane, while decreasing the water content in the feed resulted in an increase in the selectivity. The overall results showed that, at high operating temperature and high ethanol concentration in the feed, the prepared membranes are highly selective towards the water with reasonable fluxes values. The influence of temperature permeation parameter and diffusion coefficient of the feed component is also discussed. The negative heat of sorption ( ∆Hs ) values calculated on the basis of the estimated Arrhenius activation energy values indicates that the sorption process is controlled by Langmuir's mode.

Fabrication of Gellan Gum Tubular Structure Using Coaxial Needles: A Study on Wall Thickness and Encapsulation

2018 ◽  
Author(s):  
Ilhan Yu ◽  
Roland Chen ◽  
Samantha Grindrod
Keyword(s):  
Wall Thickness ◽  
Rate Ratio ◽  
Gellan Gum ◽  
Flow Rate Ratio ◽  
Tubular Structures ◽  
Extrusion Speed ◽  
Extrusion Rate ◽  
Coaxial Needle ◽  
Thermal Crosslinking ◽  
Phosphate Buffered Saline

Tubular structures of hydrogel are used in a variety of applications such as 3D cell culturing for delivery of nutrient supplies. The wall thickness of the tube determines the speed of diffusion or delivery rate. In this study, we aimed to fabricate tubular structures with varying of wall thicknesses using a thermal-crosslinking hydrogel, gellan gum, with the coaxial needle approach. The wall thickness is controlled by changing the flow rate ratio between the inner (phosphate-buffered saline) and outer needles (gellan gum). A simulation model was developed to estimate the proper extrusion speed to allow the gellan gum to be extruded around its glass transition temperature. While keeping the extrusion rate of gellan gum fixed, different PBS extrusion rates were tested to investigate the printability to form continuous tubular structures, range of printable wall thickness, and possibility to form tubes with closed ends to encapsulate fluid or drug inside the tube. The ranges of printable wall thickness with two pairs of coaxial needle were identified. It was found that at about 200% of the baseline PBS extrusion speed, a maximum of 20% difference in wall thickness can be achieved, while a close end can still be formed.

Controllability Over Wall Thickness of Tubular Structures and Encapsulation During Co-Axial Extrusion of a Thermal-Crosslinking Hydrogel

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Ilhan Yu ◽  
Samantha Grindrod ◽  
Roland Chen
Keyword(s):  
Flow Velocity ◽  
Wall Thickness ◽  
Dynamic Viscosity ◽  
Element Model ◽  
Extrusion Process ◽  
Tubular Structures ◽  
Needle Size ◽  
Thermal Crosslinking ◽  
Outer Needle ◽  
Phosphate Buffered Saline

Abstract Tubular structures of the hydrogel are used in a variety of applications such as delivering nutrient supplies for 3D cell culturing. The wall thickness of the tube determines the delivery rate. In this study, we used the coaxial extrusion process to fabricate tubular structures with varying wall thicknesses using a thermal-crosslinking hydrogel, gellan gum (GG). The objectives of this study are to investigate the thermal extrusion process of GG to form tubular structures, the range of achievable wall thickness, and a possibility to form tubular structures with closed ends to encapsulate fluid or drug inside the tube. The wall thickness is controlled by changing the relative flow velocity of the inner needle (phosphate-buffered saline, PBS) to the outer needle, while keeping the velocity of outer needles (GG) constant. Two pairs of coaxial needles were used which are 18-12 gauge (G) and 20-12G. The controllable wall thickness ranges from 0.618 mm (100% relative velocity) to 0.499 mm (250%) for 18-12G and from 0.77 mm (80%) to 0.69 (200%) for 20-12G. Encapsulation is possible in a smaller range of flow velocities in both needle combinations. A finite element model was developed to estimate the temperature distribution and the wall thickness. The model is found to be accurate. The dynamic viscosity of GG determines the pressure equilibrium and the range of achievable wall thickness. Changing the inner needle size or the flow velocity both affect the heat exchange and thus the temperature-dependent dynamic viscosity.

scholarly journals Nanocrystalline Cellulose/Polyvinylpyrrolidone Fibrous Composites Prepared by Electrospinning and Thermal Crosslinking

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Katrina M. Hatch ◽  
Jana Hlavatá ◽  
Katherine Paulett ◽  
Tatsiana Liavitskaya ◽  
Sergey Vyazovkin ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Fibrous Composite ◽  
Weight Ratio ◽  
Nanocrystalline Cellulose ◽  
Process Efficiency ◽  
Swelling Properties ◽  
Thermal Crosslinking ◽  
Swelling Capacity ◽  
Fibrous Membranes ◽  
Composite Fibrous Membranes

Nanocellulose/polyvinylpyrrolidone (nCel/PVP) fibrous composite materials containing rod-like nanocrystalline cellulose particles with the lengths varying in the range from 100 to 2000 nm were prepared by using DC electrospinning. The particle size had a strong effect on the precursor viscosity, process efficiency, and resulting fiber diameter. The thermal crosslinking of nCel/PVP composite nanofibers with up to 1.0 :  8.0 nCel/PVP weight ratio resulted in fibrous membranes with textural, air transport, and mass swelling properties varying significantly with the size of cellulose particles. The presence of nCel particles increased the oxidation resistance of PVP during the crosslinking and affected the morphological changes of nCel/PVP fibrous membranes in aqueous solutions. Particles with the smallest size improved the strength of the membrane but decreased its mass swelling capacity, whereas the larger particles led to a more porous and flexible, but mechanically weaker, membrane structure with a higher swelling ability. Thus, by using the nCel particles of different size and shape, the properties of nCel/PVP composite fibrous membranes can be tailored to a specific application.

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