Modifying plastics surfaces

Alternatively, mass produced protein-coated plates can be purchased from commercial sources but may add significant cost to an assay. Advances in producing modified plastic surfaces to mimic the structure of collagen also have been used to provide an improved environment to culture cells. This approach can eliminate the use of animal-derived products that may contain undefined ingredients (Vukicevic et al. 1992) and provide a more consistent surface. These surfaces may prove to be a useful alternative for screening with cells that do not exhibit the desired responsiveness on a standard tissue culture treated polystyrene surface. 

The situation becomes most complicated in multicomponent systems, for example, if we speak about filling of plasticized polymers and solutions. The viscosity of a dispersion medium may vary here due to different reasons, namely a change in the nature of the solvent, concentration of the solution, molecular weight of the polymer. Naturally, here the interaction between the liquid and the filler changes, for one, a distinct adsorption layer, which modifies the surface and hence the activity (net-formation ability) of the filler, arises. Therefore in such multicomponent systems in the general case we can hardly expect universal values of yield stress, depending only on the concentration of the filler. Experimental data also confirm this conclusion [13],... 

With the growth of plastic use in containers and packages, requirements to make them more compatible or useful resulted in new developments occuring and continue to occur. The two major approaches for providing permeability resistance in plastic containers involve chemically modifying the plastics surfaces and, more important from a marketing standpoint, the use of barrier plastics with nonbarrier types to meet cost-to-performance requirements. This is achieved through coextrusion, coinjection, corotation, and other such processes (Chapter 8). 

Aroxmd the same time, Beckman Instruments (now Beckman Coulter) had begun an array-based product development program focused on the use of modified plastics. Silzel and coworkers (1998) and Matson et al. (2001) of Beckman Coulter were among the first to pursue printing of antibodies onto a plastic surface in a microarray format. Silzel et al. immobilized biotinylated monoclonal antibodies onto an avidin-coated polystyrene surface and performed micro-ELISA-based isotyping of IgG species. Matson et al. 

Plasma oxidation of fibers is an example of a treatment aimed at chemically modifying the surface to improve a surface property. These treatments have wide application in industry and are used to improve wettability and printability of plastics, the adhesion of materials to surfaces including tissue culture cells, and a variety of other applications (36). 

The available concentration of a compound may determine whether it is toxic to cells. The concentration of a test compound available to cells may not be the same as the final concentration added to the sample if the toxin is bound by albumin present in serum used to supplement the medium. Chemical compounds also may bind to plastic surfaces, become concentrated inside cells, be chemically converted by modifying enzymes in the cytoplasm, or actively pumped out of cells. 

Following treatment with the alcoholic base and an alcohol rinse, the modified white residues can be removed by immersion in a mixture of an alcohol and an aggressive solvent. SEM and XPS analysis of a polyetherimide sample following treatment in a 50/50 mixture of dimethylformamide/methanol is shown in Figure 10. Little physical change to the plastic surface has occurred. The plastic surface properties, however, have now been altered. The sample is now water wettable. 

Renewable raw materials can contribute to the sustainability of chemical products in two ways (i) by developing greener, biomass-derived products which replace existing oil-based products, e.g. a biodegradable plastic, and (ii) greener processes for the manufacture of existing chemicals from biomass instead of from fossil feedstocks. These conversion processes should, of course, be catalytic in order to maximize atom efficiencies and minimize waste (E factors) but they could be chemo- or biocatalytic, e.g. fermentation [3-5]. Even the chemocatalysts themselves can be derived from biomass, e.g. expanded com starches modified with surface S03H or amine moieties can be used as recyclable solid acid or base catalysts, respectively [6]. 

In the notched Izod impact test, with the exception of some rubber modified plastics, the fracture surface of a specimen that has failed ductilely exhibits significant inward collapsing on the sides of the impact bar near the notch, indicating that a large amount of plastic flow has... 

This type of assay is valuable for characterizing the immunoreactivity of various antigens because accurately known amounts of competing antigen can be included in the assay well with no dependency on their ability to bind to plastic surfaces. It is also important because the quantity of analyte is not limited to what can be adsorbed to plastic, so that small amounts of modified base in many micrograms af DNA can be determined. 

While this is a dynamic system subject to shear force, as compared with the static system of a flask or dish, the cells growing on microcarriers are still anchorage dependent. The microcarrier bead can be made of a variety of coated and derivatized materials glass (Solo Hill, MA, USA) dextran (Pharmacia) or modified plastic (MatTek, MA, USA). The same requirements for good surface attachment and growth still apply, and must be determined experimentally. 

Nonreactive adhesives are already in their final chemical state at the moment of adhesive application and therefore do not require any special dosing or mixing processes. There is also no reaction time to achieve maximum adhesive strength. The adhesive strength is derived solely from physical processes such as the evaporation of solvents and the cooling of melted adhesives. The parameters by which the adhesive process and adhesive strength are influenced therefore differ from those that apply to the reactive adhesives. On the other hand, many nonreactive adhesives are modified to enter into chemical interactions with plastic surfaces after application. Chemical interaction with metals is less frequent. 

Carbon-supported catalysts, especially of platinum group metals, are used industrially in hundreds of reactions, particularly for manufacture of pharmaceuticals, perfumes, and plastics. Most carbon supports are manufactured by pyrolysis of carbonaceous materials such as wood, charcoal, coal, or organic polymers. Chemical pretreatment is used to modify the surface chemistry to impart superior catalytic properties. 

Polyolefin films have been post-irradiation grafted with materials such as trifluorostyrene or methacrylic acid followed by sulfonation to control ion flow through nickel-cadmium batteries [8, 9], Investigation is underway to use crosslinked films grafted with selected monomers to develop lower cost membranes for fuel cells. A major commercial use of EB grafting has been to modify the surfaces of plastic films and paper with low molecular weight silicones to impart adhesive or release properties. 

Polyethylene terephthalate is a low-cost polymer that exhibits excellent optical and mechanical properties. PET is commonly used in the field of packaging, specifically plastic bottles. PET is also used as flexible substrate in organic solar cells. Exposing this polymer to environmental atmosphere changes its external appearance, modifies its surface, and degrades its properties. 

The use of narrower rounded turns for microchip-based SCCE is reported for reducing band broadening at the corners. This approach has been shown to reduce the broadening seen for turns in other microfluidic chip designs. Other, more exotic approaches to reducing dispersion at the turns of channels on microfluidic devices have been reported. One technique using a pulsed UV laser to modify the surface of plastic chips at the turn to increase the EOF by up to 4%. This technique was shown to reduce band broadening at the turns. ... 

Many pretreatment techniques are used in practice (Table 8.2). The normal physical method used to improve the adhesive strength of the coating to the substrate is to slightly roughen the surface by solvent treatment, abrasion, or blasting. Some plastics (e.g., polyolefins) require special pretreatment methods processes that modify the surface molecular layers of the plastic to increase their polarity have proved suitable (e.g., flaming, immersion in an oxidizing acid, immersion in a benzophenone solution with UV irradiation, corona treatment, plasma treatment). 

Modifying the surfaces of plastics to impart specialized properties is also likely to he a growing area. Acrylonitrile butadiene styrene (ABS) has recently been surfece treated with silver compounds to impart anti-bacterial properties which remain... 

Plasma treatment of PDMS followed by adsorption of self-assembled silane monolayers has enabled us to controllably modify the surface energy of elastomer surfaces as described in the section on the Johnson, Kendall, and Roberts approach to deriving the surface free energy of solids. A similar treatment of silicon substrates has produced a useful, low—hysteresis model substrate for contact angle study. There are three types of PDMS contact angle substrates usually studied fluids baked or otherwise chemisorbed on solids such as glass or metals cross-linked coatings on flexible substrates, such as paper or plastic film PDMS elastomer surfaces. 

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