Solution-casting procedures

Nisin, ethylenediaminetetraacetic acid (EDTA), sodium benzoate, potassium sorbate or combinations of them were incorporated into PLA films by solution casting procedure. Their antimicrobial properties were tested against E. coli 0157 H7 and habitual microbiota in strawberiy puree. The films containing a mfacture of all preservatives presented the best results, followed by the combination of the two organic salts. These two films presented higher efficiency than direct addition of the mixed preservatives. ... 

The free surfaces of samples are studied using SEM and AFM. The smooth specimen surfaces which are required for this purpose are prepared either by ultramicrotomy or by solution-casting procedures (e.g., spin-coating). The free surface can also be etched by reactive ions via a process known as reactive ion etching (RIE) [49-51], or by using chemicals as in the case of permanganic etching [52-55]. 

It is worth noting that nanoporous 8 form hlms with an c orientation, as derived by the TCE-induced recrystallization procedure, are much less brittle than those obtained by the previously known solution casting procedure. 

The diffusion coefficients of potassium and sodium chlorides in the membrane we have found to be independent of solution concentration within experimental error. The value of sodium chloride agrees well with those found by others bearing in mind the differences in the polymer and in the membrane casting procedures (5,13). 

The above set of rules - though accurately descriptive of earlier casting procedures - has led to serious misconceptions pertaining to the formation of anisotropic membranes, and therefore, misconceptions in the formulation of new polymeric casting solutions. It is evident that the polymer solution concentration progressively increases at the surface layer during the evaporation period, and... 

The casting procedure consisted of drawing an aqueous solution of PVA to a thin layer, and after an evaporation period, immersing in the complexing bath. The complexing bath used in our study was basically a saturated CuSO solution, with or without a series of possible additives. After a period of equilibration of over 24 hours, the membranes were dried and subjected to dry heat treatment,in order to stabilize the asymmetric structure obtained. The preparation conditions of several membranes prepared by this method are shown in Table V. 

Experiments indicate that the critical strain-to-failure is also affected by the average molecular weight and by material processing history. McGrath40 reported strain-to-break of a non-crystalline ionomer (a poly(arylene-ether) random copolymer, biphenyl sulfone in H form, or bi-phenyl sulfone in H form (BPSH)) is proportional to the length of the chain. We found in our laboratory that the casting procedure also affects the strain-to-break of the solution-cast ionomer film. As shown in Fig. 19, a Nation film cast at near room... 

D. Obtain the infrared absorption spectrum of the sample by the following procedure Prepare a 0.2% aqueous solution, cast films 0.0005 cm thick (when dry) on a suitable nonstick-... 

The oligothiophene films were prepared by solution cast methods and by vacuum deposition. Depending on the cast procedure, different layer thicknesses could be achieved. Preparation from solution either by drop casting or spincoating resulted in films ranging from 50 nm to 200 nm in thickness. Vacuum sublimation yielded very thin layers in the range of 10 nm to 15 nm, which nevertheless allowed to build-up and operate an OFET structure of molecular thickness as demonstrated in this chapter. 

In the second approach, metal-ion/complex was first attached to one of the polymer blocks. A thin film of the resulting polymer metal complex was then obtained by spin coating/solution casting. Alternatively, the polymer metal complex may also be dissolved in a suitable solvent system that selectively dissolves one of the blocks. Micelles or nanosized aggregates formed in this case. The micellization of amphiphilic block copolymers and their use in the formation of metal nanoparticles has been discussed previously.44 A monolayer of micelles was introduced on a substrate surface by dipping or electrostatic attraction. The substrate was then subjected to further chemical or physical treatments as mentioned earlier. The third approach involves the formation of micelles from the metal-free block copolymer in a suitable solvent system. The micelle solution was then added with metal ion, which was selectively coordinated to one of the blocks. These micelle-metal complexes can also be processed by a procedures similar to the second approach. 

As previously mentioned, part of our work was dedicated to the study of bio-activity of the enzyme used to prepare bioartificial hydrogels the enzyme activity was monitored, in a phosphate buffer containing starch substrate (0.2 mg/ml), by measuring the substrate concentration remaining in the batch solution at different times. The results, compared with free a-amylase behaviour, indicated that the catalytic hydrolysis of starch was the same for free a-amylase and a-amylase delivered from bioartificial blend no deactivation of the enzyme because of the presence of PVA was observed either in solution or after the preparation through casting procedure. On the contrary, a-amylase seemed slightly more stable in the polymer network. 

Studies were also made of the photochemistry of styrene copolymers containing minor amounts (2-7%) of the ketone monomers to minimize the effects of energy transfer and migration. The polymers were photolyzed in thin ( 0.1 mm) solution-cast films and in solution. In the latter case the rates could be followed by automatic viscometry using the procedure described by Kilp et al. (33,34) and by Nemzek and Guillet (35). Chemical changes in the solid state were followed by FTIR spectroscopy. 

Polyacrylates are produced commercially by free-radical-initiated solution and emulsion polymerization of the appropriate monomer. Unlike for methacrylates, suspension and casting procedures are not feasible because of the rubber and adhesive nature of higher acrylates. 

Pozio and coworkers [ 175] studied the proton conductivity of solution-cast Nafion membranes, and compared the data to those obtained from commercial Nation 112 and Nafion 115 membranes. Membranes were cast under the conditions listed in Table 3. Process 01, process 02, and process 03 represent the different methods used to obtain Nafion powder. In process 01, a commercial 5 wt % dispersion of Nafion 117 in low ahphatic alcohols was used to cast a membrane. An alcohol-free Nafion 117 dispersion was prepared using an azeotropic distillation, the concentrated dispersion was neutralized with 0.1 M NaOH solution, the solution was heated at 60 °C to remove solvent, and Nafion powder was ball-milled to form a fine powder. In process 02, as-received Nafion 112 membranes in their protonic form were heated in a mixture of ethanol/water at 250 °C to prepare a dispersion. An alcohol-free Nafion dispersion was prepared by distillation, the dispersion was neutralized with 0.1 M NaOH solution, heated at 60 °C to remove solvent, and the resulting Nafion powder was ball-milled. Process 03 consisted of the same procedure but, in contrast to process 02, membranes were neu-trahzed with 0.1 M NaOH prior to dissolution. In order to form cast films, PFSI powder was mixed with the solvents listed in Table 3, sonicated, and the homogeneous dispersion placed into petri dishes. DMF-PFSI dispersions were heated at 165 °C DMSO and EG dispersions were heated at 180 °C. Dried, cast films were re-acidified using boiling nitric acid (20 wt %) followed by two boiling water treatments. 

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