Polymer coatings, thickness determination

Nutrients are released from POLYON-coated fertilizers by osmotic diffusion. The RLC process permits appHcation of ultrathin, hence lower cost, membrane coatings which distinguishes this technology from many other polymer-coated fertilizers. The coating thickness determines the diffusion rate and the duration of release. POLYON-coated urea at a 4% coating (44% N) will release at twice the rate and will have half the duration as an 8% coating... 

The thickness of the polymer coatings was determined as follows. Polymer films were spin cast (15) from a MDI/ED/PTMO polyurethaneurea of known composition. The film thickness, measured by a micrometer, was found to correlate linearly with the height of the 1600 cm peak (v(C C) benzene ring), thus allowing determination of a Beer s law extinction coeffecient for the mass fraction of benzene rings in these polymers. Transmission spectra of the dip coated IRE s were obtained, and the polymer thickness determined assuming that the Beer s law extinction coefficient was unchanged on these thin films. 

Encouraged by the X-ray and contact angle results, we performed some preliminary gas-permeation measurements. Here, a self-supporting film is required and only the longer block copolymers were used. Fluoro-PSB-II and Fluoro-triblock were coated on porous Celgard 2400 membranes the measurements were taken at room temperature at a driving pressure of 5 bars. Since no absolute polymer layer thickness has been determined, only relative values of the permeability are given (Table 10.6). In the case of the separation of C02 from... 

Polymer coatings on stiffer substrates can be measured by time-resolved techniques (Sinton et al. 1989). Often in these cases it is not convenient to measure a direct reflection from an uncoated part of the substrate at more or less the same time, and anyway the substrate may not be flat, but this may not matter if it can be assumed that either the thickness or the longitudinal velocity of the coating does not vary. The time interval between the echoes from the top and bottom surfaces of the coating can then be used to determine the unknown quantity. An example of the kind of signal that can be obtained is shown in Fig. 10.5. The specimen was a coating of PET (polyethylene terephthalate) 15 m thick on a stone-finish rolled steel substrate. Although there is some overlap of the two echoes, there is no difficulty in... 

In the next step, polymer films (thickness 200 nm) of PS-COOH or FPS-COOH were spin coated on the top of the GPS layer from 2% toluene solutions. After casting, the films were annealed in a vacuum oven at 150 °C for 15 h. Non-grafted polymer was removed by Soxhlet extraction in toluene for 6 h. The thickness of PS and FPS grafted layers was determined using null ellipsometiy. 

CEC was demonstrated in the analysis of /i-adrenergic antagonists using capillaries modified with propranolol-imprinted polymer. In situ molecular imprinting was performed via photo-polymerisation at — 20°C within a capillary that was premodified with 3-methacryloxypropyltrimethoxysilane. The time for UV irradiation was carefully determined so as to obtain a polymer coating of appropriate thickness. Enantioseparation of the racemate of propranolol was successfully demonstrated with a separation factor of 1.12 and a resolution factor of 1.26. 

The commercial polypropylene films were coated with a layer of A1 by physical vapor deposition. The coating thickness was determined from SEM pictures of commercial film 1 seen in Fig. 1.1a as 32 nm for commercial film 1. The coating had the shape of the polymer layer. There were... 

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