Characterization of N-Vinyl pyrrolidone grafting into silicone rubber

1989 ◽  
Vol 47 ◽  
pp. 882-883
Author(s):  
R. Lee ◽  
R. Greer
Keyword(s):  
Cross Sections ◽  
Silicone Rubber ◽  
Sodium Bicarbonate Solution ◽  
Monomer Concentration ◽  
Surface Preparation ◽  
Vinyl Pyrrolidone ◽  
Grafted Polymers ◽  
Depth Of Penetration ◽  
Structural Reinforcement ◽  
Thickness Measurements

Since 1960, hydrogels have been utilized in a large number of biomedical products. The poor mechanical strength of hydrogels necessitates the use of a stronger support material in order to provide structural reinforcement. Methods of surface preparation include radiation grafting. Parameters of importance for grafting N-vinyl pyrrolidone (NVP) into silicone rubber include the choice of solvent, monomer concentration, radiation dose and use of selective inhibitors. Post irradiation extraction of homopolymer and monomer from the silicone rubber substrate after grafting is an important step. NVP grafted polymers can be stained by many dyes for depth of penetration studies.Fourteen cm sections of non-reinforced Silastic® (silicone rubber, Dow Corning) tubing, 0.078″x0.125″, were boiled for three 1 h periods in aqueous 2.0% sodium bicarbonate solution. Prior to irradiation, monomer solutions used to fill tubes were bubbled with nitrogen for at least 30 min. Several monomer/solvent formulations (100% NVP; 80% NVP/20% methanol; and 60% NVP/40% methanol, and gamma irradiation doses (50, 150, 200 and 250 krad) were used.) After irradiation, samples were flushed with either acetone/methanol (50:50 v/o) or ethanol/water (50:50 v/o) , followed by three 30 min agitated washes in the same type of solution. To test the effect of methanol concentration on rim thickness measurements, 0.5 cm lengths of cleaned Silastic , acetone/methanol extracted Silastic®, and grafted tubing of 100% NVP and 80% NVP/20% methanol formulations were immersed in 0.1% acid fuchsin stains in 10, 50, and 100% methanol for 48 h. After rinsing and drying, cross sections were cut, and the penetration depth of the stain (i.e., graft depth) was measured.

Nonthrombogenic surface preparation for silicone rubber

1969 ◽  
Vol 3 (4) ◽  
pp. 587-613 ◽  
Author(s):  
Sennen Uy ◽  
Karl Kammermeyer
Keyword(s):  
Silicone Rubber ◽  
Surface Preparation

Shape Design Enhancement of Pultruded FRP Profiles for Structures Ancillary to Masonry Constructions

2019 ◽  
Vol 817 ◽  
pp. 83-88
Author(s):  
Giosuè Boscato ◽  
Ivano Aldreghetti ◽  
Daniele Baraldi ◽  
Antonella Cecchi ◽  
Giorgio Costantini ◽  
...  
Keyword(s):  
Cross Sections ◽  
Ad Hoc ◽  
Shear Stiffness ◽  
Numerical Approach ◽  
Fiber Reinforced Polymers ◽  
Structural Systems ◽  
Historical Building ◽  
Structural Improvement ◽  
Structural Reinforcement ◽  
Steel Shapes

The historical building heritage, monumental, civil and industrial has highlighted, especially in the last decade, the high vulnerability with respect to horizontal actions. The need to design stable and strong structural systems with respect to the stresses acting in various directions has oriented research to develop lightweight technologies for structural systems, independent or ancillary, with reduced mass to mitigate the consequent applied load. In this scenario all-FRP (Fiber Reinforced Polymers) systems can be a valid alternative for new constructions and / or structural reinforcement. The scenario described above, highlights the importance of developing innovative technologies suitable for the functional and structural improvement of the existing buildings. It is necessary to define an innovative approach aimed at identifying an ad-hoc profile for the FRP pultruded profiles (currently referring to the steel shapes), which allows to capitalize the performance capabilities, limiting the main defects related to low shear stiffness of FRP pultruded material. This research analyses how the shape enhancement of the cross sections, with shape redraw, allows to increase the structural performances of FRP pultruded profiles. Experimental data of previous research on buckling behaviour of different open cross section profiles, narrow and wide flanges, have been analysed and validated by numerical approach and compared with new strengthened shapes.

scholarly journals Surface Preparation of Cross Sections of Traditional and Modern Paint Using the Argon Ion Milling Polishing CP System

2006 ◽  
Vol 12 (S02) ◽  
pp. 1322-1323 ◽  
Author(s):  
JJ Boon ◽  
S Asahina
Keyword(s):  
Cross Sections ◽  
Surface Preparation ◽  
Ion Milling ◽  
Argon Ion

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

scholarly journals Uncertainty quantification of fiber orientation distribution measurements for long-fiber-reinforced thermoplastic composites

2017 ◽  
Vol 52 (13) ◽  
pp. 1781-1797 ◽  
Author(s):  
Bhisham N Sharma ◽  
Diwakar Naragani ◽  
Ba Nghiep Nguyen ◽  
Charles L Tucker ◽  
Michael D Sangid
Keyword(s):  
Cross Sections ◽  
Fiber Orientation ◽  
Surface Preparation ◽  
Orientation Distribution ◽  
Elastic Stiffness ◽  
Thermoplastic Composites ◽  
Fiber Reinforced ◽  
Fiber Orientation Distribution ◽  
Discontinuous Fiber ◽  
Reinforced Thermoplastics

We present a detailed methodology for experimental measurement of fiber orientation distribution in injection-molded discontinuous fiber composites using the method of ellipses on two-dimensional cross sections. Best practices to avoid biases occurring during surface preparation and optical imaging of carbon-fiber-reinforced thermoplastics are discussed. A marker-based watershed transform routine for efficient image segmentation and the separation of touching fiber ellipses is developed. The sensitivity of the averaged orientation tensor to the image sample size is studied for the case of long-fiber thermoplastics. A Mori–Tanaka implementation of the Eshelby model is then employed to quantify the sensitivity of elastic stiffness predictions to biases in the fiber orientation distribution measurements.

scholarly journals Biological macromolecule chitosan grafted co-polymeric composite: bio-adsorption probe on cationic dyes

2021 ◽  
Author(s):  
Shyam R. Khairkar ◽  
Shubham V. Pansare ◽  
Amol A. Shedge ◽  
Shraddha Chhatre ◽  
Dnyaneshwar K. Kulal ◽  
...  
Keyword(s):  
Monomer Concentration ◽  
Polymeric Composite ◽  
Sorption Process ◽  
Vinyl Monomer ◽  
Grafted Polymers ◽  
Biological Macromolecule ◽  
Buffer Solution ◽  
Toxic Dyes ◽  
Ph Buffer Solution ◽  
Ph Buffer

AbstractChitosan biological macromolecule is a versatile polymer; chemical modification has been carried out that lead to the formation of chitosan grafted polymers composites (Chito-g-PC). We proposed synthesis of six various Chito-g-PC as sorbents for toxic dyes. A novel graft copolymerization method based on radical polymerization with vinyl monomer like acrylic acid, acrylamide, N-isopropylacrylamide, methacrylic acid and polyacrylonitrile were utilized in order to address the large amount of swelling at four different pH buffers solution. The effect of initiator and monomer concentration, time and temperature on % grafting and % grafting efficiency were performed. Comparative characterization of Chito and Chito-g-PC were evaluated by SEM, XRD and FTIR, as well as solubility characteristics of the composites were determined by various pH buffer solution. Cationic toxic dyes Malachite green (MG) and Methylene blue (MB) were selected as the sorbet, and Chito-g-PC were used as biosorbents. Thermodynamic analysis showed that the sorption process was spontaneous and endothermic with an increased randomness. The sorption experiments were realized with six different Chito-g-PC for MG and MB at various pH.

scholarly journals Non-destructive thickness measurement of thermal barrier coatings using terahertz radiation

2021 ◽  
Author(s):  
Luis Isern ◽  
Andrew J. Waddie ◽  
Christine Chalk ◽  
Andrew J. Moore ◽  
John R. Nicholls
Keyword(s):  
Refractive Index ◽  
Thermal Barrier Coatings ◽  
Cross Sections ◽  
Thickness Distribution ◽  
Thickness Measurement ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Thickness Variations ◽  
Thickness Measurements ◽  
Non Destructive

AbstractA non-destructive thickness measurement technique based on terahertz (THz) reflectivity was successfully deployed to interrogate 7 wt.% yttria-stabilised zirconia thermal barrier coatings (TBCs) produced by electron-beam physical vapour deposition (EB-PVD). The THz technique was shown to produce accurate thickness maps for different samples with a resolution of 1 × 1 mm over a surface of 65 × 20 mm that were compared with direct examination of key cross-sections. All thickness measurements on different samples were calculated using a single value of refractive index. Small defects characteristic of EB-PVD, such as “carrot growths” and variations on column inclination, were evaluated and did not produce significant variations in the refractive index of the TBC. Moreover, the thickness maps correctly display thickness variations that are a consequence of the point-source nature of EB-PVD evaporation. In summary, this paper demonstrates the technique can be successfully deployed on large surfaces, and across different coatings of the same material produced under the same deposition conditions. It is shown that a single n value is required to map the thickness distribution for all samples. This combination of qualities indicates the potential of the technique for in-line control of TBC manufacture.

scholarly journals Multiphasic effect of vinyl pyrrolidone polymers on amyloidogenesis, from macromolecular crowding to inhibition

2018 ◽  
Vol 475 (21) ◽  
pp. 3417-3436 ◽  
Author(s):  
Richard Berwick ◽  
David J. Vaux ◽  
Létitia Jean
Keyword(s):  
Molecular Mass ◽  
Surface Activity ◽  
Type Ii Diabetes ◽  
Volume Fraction ◽  
Macromolecular Crowding ◽  
Monomer Concentration ◽  
Vinyl Pyrrolidone ◽  
Bulk Solution ◽  
Type Ii

Deposition of misfolded amyloid polypeptides, associated with cell death, is the hallmark of many degenerative diseases (e.g. type II diabetes mellitus and Alzheimer's disease). In vivo, cellular and extracellular spaces are occupied by a high volume fraction of macromolecules. The resulting macromolecular crowding energetically affects reactions. Amyloidogenesis can either be promoted by macromolecular crowding through the excluded volume effect or inhibited due to a viscosity increase reducing kinetics. Macromolecular crowding can be mimicked in vitro by the addition of non-specific polymers, e.g. Ficoll, dextran and polyvinyl pyrrolidone (PVP), the latter being rarely used to study amyloid systems. We investigated the effect of PVP on amyloidogenesis of full-length human islet amyloid polypeptide (involved in type II diabetes) using fibrillisation and surface activity assays, ELISA, immunoblot and microscale thermophoresis. We demonstrate that high molecular mass PVP360 promotes amyloidogenesis due to volume exclusion and increase in effective amyloidogenic monomer concentration, like other crowders, but without the confounding effects of viscosity and surface activity. Interestingly, we also show that low molecular mass PVP10 has unique inhibitory properties as inhibition of fibril elongation occurs mainly in the bulk solution and is due to PVP10 directly and strongly interacting with amyloid species rather than the increase in viscosity typically associated with macromolecular crowding. In vivo, amyloidogenesis might be affected by the properties and proximity of endogenous macromolecular crowders, which could contribute to changes in associated pathogenesis. More generally, the PVP10 molecular backbone could be used to design small compounds as potential inhibitors of toxic species formation.

The use of argon cluster bombardment for the surface preparation of paint cross-sections for analysis by ToF-SIMS

2014 ◽  
Vol 46 (10-11) ◽  
pp. 781-785 ◽  
Author(s):  
M. Vermeulen ◽  
C. Poleunis ◽  
A. Delcorte ◽  
P. Bertrand ◽  
J. Sanyova
Keyword(s):  
Cross Sections ◽  
Surface Preparation ◽  
Cluster Bombardment ◽  
Tof Sims

Evaluation of Pressure Free Nanoparticle Sintered Silver Die Attach on Silver and Gold Surfaces

2013 ◽  
Vol 2013 (HITEN) ◽  
pp. 000237-000245 ◽  
Author(s):  
G. Lewis ◽  
G. Dumas ◽  
S. H. Mannan
Keyword(s):  
Shear Strength ◽  
Cross Sections ◽  
Storage Time ◽  
Sintering Process ◽  
Die Attach ◽  
Free Process ◽  
Sintered Ag ◽  
Bondline Thickness ◽  
Ag Substrate ◽  
Thickness Measurements

A commercially available silver nanoparticle based die attach material was used in a pressure free process to bond 2.5 mm square Ag plated Si die to Ag and Au plated substrates. The two substrate types were 5mm square Ni/Ag plated silicon substrate and a W/Ni/Au metallised cofired alumina package. The assemblies were stored at 300 °C for up to 500 h and the morphology of the sintered Ag and the shear strength was monitored as a function of time. Bondline thickness measurements were carried out after following the paste manufacturer's drying and sintering temperature profile. On Ag substrate it was found that die shear strength increased with storage time. The fracture surfaces of the sheared die and substrate as well as cross sections of untested die were examined using electron microscopy. It was found that the Ag grains grew in size and porosity decreased over time. There was also a clear difference in morphology between sintered Ag at the die edge and centre. During shearing the Ni layer was found to separate from the chip at the edges of the die after ageing. On Au substrate, it was found that die shear strength decreased with storage time. It was found that the Au diffused into the Ag, creating a low porosity Au-Ag layer. Ag also migrated towards the Au surface, leaving behind a layer of voids which contributed to weakening of the joint. Rapid Au diffusion was associated with the high density of grain boundaries arising from the sintering process.

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