Effect of annealing time, film thickness, and molecular weight on surface enrichment in blends of polystyrene and deuterated polystyrene

1994 ◽  
Vol 27 (2) ◽  
pp. 596-605 ◽  
Author(s):  
P. P. Hong ◽  
F. J. Boerio ◽  
S. D. Smith
Keyword(s):  
Molecular Weight ◽  
Film Thickness ◽  
Annealing Time ◽  
Surface Enrichment

Surface Enrichment and Evaporation in a Polymer Mixture of Long and Short Chains

1989 ◽  
Vol 166 ◽  
Author(s):  
Russell J. Composto ◽  
Richard S. Stein ◽  
Gian P. Felcher ◽  
Abdelkader Mansour ◽  
Alamgir Karim
Keyword(s):  
Molecular Weight ◽  
Film Thickness ◽  
Concentration Profile ◽  
Scattering Length ◽  
Weight Fraction ◽  
Polymer Mixture ◽  
Light Chains ◽  
Neutron Reflectivity ◽  
Surface Enrichment ◽  
Polymer Interface

ABSTRACTNeutron reflectivity has been used to determine the concentration profile at the vacuum-polymer interface for a two polymer blend. To quantify surface enrichment and evaporation due to differences in chain length, we have measured the reflectivity of a mixture of short deuterated and long protonated polystyrene chains (DPS & PS), with a weight fraction of 0.5. When a mixture of DPS and PS chains of molecular weight 720 and 910k respectively were annealed, a small but measurable increase in asymptotic reflectivity occured, coupled with a decrease of film thickness and scattering length density. This is indicative of surface enrichment and evaporation of the light chains (DPS). Ellipsometry studies confirmed that the short chains evaporated and its rate was established as a function of the temperature. Upon increasing the DPS molecular weight to 9600, the enrichment becomes considerably greater whilst the evaporation becomes negligible.

scholarly journals Effect of 1,4-Napthaquinone (NQ) and benzophenone (BPH)on the photodegradation and biodegradation of methyl cellulose film

2010 ◽  
Vol 7 (1) ◽  
pp. 737-744
Author(s):  
Baghdad Science Journal
Keyword(s):  
Molecular Weight ◽  
Film Thickness ◽  
Carbonyl Compounds ◽  
Methyl Cellulose ◽  
Chain Scission ◽  
Cellulose Derivative ◽  
Accelerated Weathering ◽  
Cellulose Derivatives ◽  
Photodegradation Rate ◽  
Aromatic Carbonyl Compounds

The induced photodegradation of methyl cellulose (MC) films in air was investigated in the absence and presence of aromatic carbonyl compounds(photosenssitizers): 1,4-naphthaquinone (NQ) and benzophenone (BPH) by accelerated weathering tester. The addition of (0.01 wt %) of low molecular weight aromatic carbonyl compounds to cellulose derivatives films(25µm in thickness) enhanced the photodegradation of the polymer films.The photodegradation rate was measured by the increase in carbonyl absorbance. Decreases in solution viscosity and reduction of molecular weight were also observed in the irradiated samples. Changes in the number-average chain scission, the degree of deterioration and in the quantum yield of chain scission values are also observed, and it was concluded that branching or cross-linking has occurred for cellulose derivative with NQ and BPH. Findings from all analytical techniques indicated that the 1,4-naphthaquinone (NQ) photosensitizer enhance the photodegradation of methyl cellulose more than benzophenone (BPH). The effect of the photosensitizer concentration, (ranging from 0.01 to 0.1 %), on the rate of photodegradation was also monitored for MC films. The rates are increased with increasing the photosensitizer concentration. The effect of film thickness is also studied at fixed sensitizer concentration (0.05%), and results show that the rate of cellulose derivative photodegradation decreases with increasing film thickness. The rate constants of the photodegradation of the photosensitizers deduced in cellulose derivatives films, [at concentration of (0.1%)by weight and thickness (25µm)]. Biodegradation of irradiated cellulose derivatives films was conclusively established with bacteria type Pseudomonas aeuroginosa Rb-19 isolated from crude oil. The amount of bacteria growth on MC after 30 days was lower, while there was no growth observed in MC with BPH

An Investigation Into the Influence of Fluid Viscoelasticity in a Squeeze Film Bearing

1978 ◽  
Vol 100 (1) ◽  
pp. 56-64 ◽  
Author(s):  
John A. Tichy ◽  
Ward O. Winer
Keyword(s):  
Molecular Weight ◽  
Film Thickness ◽  
High Molecular Weight ◽  
Hydrodynamic Lubrication ◽  
Load Capacity ◽  
Surface Film ◽  
Free Fall ◽  
Squeeze Film ◽  
Delayed Response ◽  
High Molecular Weight Polymers

This investigation concerns a prediction of the behavior of viscoelastic fluids in a parallel circular squeeze film with a constant approach velocity, and a comparison to experimental results. The squeeze film geometry has direct application to unsteady hydrodynamic lubrication. The analysis predicts that load capacity of a viscoelastic fluid may be increased due to normal stress effects or decreased due to a delayed response of shear stress to a change in shear rate. Ten tested fluids include Newtonian control fluids, silicone fluids, high molecular weight polymers in petroleum oils, and extremely high molecular weight polymers in water and glycerin. The experimental squeezing is accomplished by the free fall of a cylindrical steel rod along its axis toward a stationary opposing surface. Film thickness, velocity of approach and load are measured. The velocity of approach is essentially constant in the range of film thickness considered. The water-glycerin-polymer solutions exhibited load capacity increases up to 33 percent, while the petroleum-polymer and silicone fluids showed decreases to 23 percent. It appears that viscoelastic effects cannot account for the reported improved bearing performance of polymer-additive lubricants.

Effect of Film Thickness and Annealing Time on Residual Stress of High-k Al2O3 Film on Si-(100) Substrate

2013 ◽  
Vol 644 ◽  
pp. 161-164
Author(s):  
Wu Tang ◽  
Ji Jun Yang ◽  
Chi Ming Li
Keyword(s):  
Thin Film ◽  
Residual Stress ◽  
Film Thickness ◽  
Annealing Time ◽  
Gate Dielectric ◽  
Electron Beam Evaporation ◽  
Film Stress ◽  
X Ray Diffraction ◽  
Thin Film Stress ◽  
High K

In this paper, Al2O3 thin film samples were deposited on Si-(100) substrate by electron beam evaporation with different thickness at substrate temperature 400°C and after that, annealed in the air at 500°C with different time. The structure, thickness and residual stress of these films were measured by X-ray diffraction (XRD), stylus profiler and electronic thin film stress distribution tester, respectively. The effects of several parameters on the properties of Al2O3 films were studied. In addition, the relations between thickness and residual stress of Al2O3 thin films as the high-k gate dielectric was analyzed. The results shown that the residual stress becomes smaller after annealing, the residual stress was depressed down to maximum value 300MPa from 580MPa for annealing time 30min, and depressed down to minimum value 220MPa from 580MPa for annealing time 60min. But eventually, it has a critical film thickness point on the scale.

The Generalized Newtonian Fluid Model and Elastohydrodynamic Film Thickness

2002 ◽  
Vol 125 (1) ◽  
pp. 70-75 ◽  
Author(s):  
Scott Bair ◽  
Farrukh Qureshi
Keyword(s):  
Molecular Weight ◽  
Film Thickness ◽  
Fluid Model ◽  
Shear Thinning ◽  
Nonequilibrium Molecular Dynamics ◽  
Generalized Newtonian Fluid ◽  
Flow Curves ◽  
Liquid Behavior ◽  
Inlet Zone ◽  
Film Thinning

The nature of real shear-thinning in elastohydrodynamic contacts is well-known from both experimental measurement and nonequilibrium molecular dynamics to follow a power-law. Shear-thinning will affect the film thickness when the Newtonian limit is low enough to occur in the inlet zone (less than about 1 MPa shear stress). Then kinetic theory tells us that film thinning should occur for molecular weight greater than 2000 kg/kmol. We present a review of generalized Newtonian models, flow curves for real lubricants and comparison of calculated and measured film thickness. The calculations utilize measurable liquid behavior, in contrast to most previous work.

Elastohydrodynamic lubrication analysis of ultra-high molecular weight polyethylene hip joint replacements under squeeze-film motion

2001 ◽  
Vol 215 (2) ◽  
pp. 141-151 ◽  
Author(s):  
M Jagatia ◽  
D Jalali-Vahid ◽  
Z M Jin
Keyword(s):  
Molecular Weight ◽  
Femoral Head ◽  
Film Thickness ◽  
Hip Joint ◽  
Elastohydrodynamic Lubrication ◽  
Squeeze Film ◽  
Acetabular Cup ◽  
Joint Replacements ◽  
Hip Joint Replacements ◽  
Ultra High Molecular Weight

Elastohydrodynamic lubrication was analysed under squeeze-film or normal approach motion for artificial hip joint replacements consisting of an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup and a metallic or ceramic femoral head. A simple ball-in-socket configuration was adopted to represent the hip prosthesis for the lubrication analysis. Both the Reynolds equation and the elasticity equations were solved simultaneously for the lubricant film thickness and hydrodynamic pressure distribution as a function of the squeeze-film time was solved using the Newton-Raphson method. The elastic deformation of the UHMWPE cup was calculated by both the finite element method and a simple equation based upon the constrained column model. Good agreement of the predicted film thickness and pressure distribution was found between these two methods. A simple analytical method based upon the Grubin -Ertel-type approximation developed by Higginson in 1978 [1] was also applied to the present squeeze-film lubrication problem. The predicted squeeze-film thickness from this simple method was found to be remarkably close to that from the full numerical solution. The main design parameters were the femoral head radius, the radial clearance between the femoral head and the acetabular cup, and the thickness and elastic modulus for the UHMWPE cup; the effects of these parameters on the squeeze-film thickness generated in current hip prostheses were investigated.

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