Substrate durability

It is difficult to compare the data published by different authors due to differences of strains, physiological conditions, organic substrates, durability of the process, and size and peculiarities of photobioreactors. However, an evaluation of the main factors affecting the specific rate of hydrogen photoproduction can be attempted. 

The mechanisms by which microbes attach to surfaces and viability of the microorganisms are discussed. Representative microorganisms (bacteria, algae, fungi, viruses and other microbes) are listed that are problematical from a medical or health perspective and/or that lead to unwanted damage in materials. Adhesion and persistence of microorganisms, methods of decontamination of polymeric substrates, durability of antimicrobial agents on materials, and applieations, are discussed. 19 refs... 

Epoxy resins are also used in special appHcations, such as an overlaying procedure requiring a durable, heat-resistant bond of a difficult-to-bond overlay on a wood-base panel substrate. Metal sheets used as overlays, for example, often require an epoxy adhesive. 

The constmction of vinyl-coated fabrics varies according to its appHcation. A vinyl-coated fabric used for automobile seat covers is shown in Figure 3 a woven fabric is the substrate. The material is durable but stiff and heavy. Incorporating an expanded foam stmcture into the coating layer reduces the weight (Fig. 4), and replacing the woven substrate fabric with a soft knit fabric improves fiexibihty. 

Other Durable Applications. Other durable appHcations such as interlinings and coating/laminating substrates do not appear to offer much near-term opportunity for growth for spunbonded fabrics. In interlinings, however, spunlaced nonwovens have received wide acceptance because of the outstanding drape and softness previously unavailable from any other fabric. 

Another approach in chemical finishing is to use reagent systems that are reactive with themselves but only to a limited extent or not at all with the fiber substrate. An example of such approaches are in situ polymer systems that form a condensed fiber system within the fiber matrix (1,2). A third type of approach may be the deposition of a polymer system on the fiber substrate. Once deposited, such systems may show a strong affinity to the fiber and may be quite durable to laundering. Polyacrjiate and polyurethane are examples of durable deposits on cotton, which last through numerous launderings (3). 

Cross-linked finishes are not permanent in the tme sense of the word however, under optimum conditions the finish can last for the usehil life of the material. Wet abrasion during laundering is probably the principal cause of gradual removal of the finish. In order to retain antistatic protection for extended use, an excess of finish is often appHed The extent of chemical interaction between the durable antistatic agents and the fiber substrates to which they are appHed is not perfectiy understood. Certain oxidizing agents such as hypochlorite bleaches tend to depolymerize and remove some durable antistatic finishes. Some of the durable finishes have also produced undesirable side effects on textile materials, ie, harsh hand, discoloration, and loss of tensile properties. 

Silicone adhesives are generally applied in a liquid and uncured state. It is therefore the physical and chemical properties of the polymers, or more precisely of the polymer formulation, that guide the various processes leading to the formation of the cured silicone network. The choice of the cure system can be guided by a variety of parameters that includes cure time and temperature, rheological properties in relation with the application process, substrates, the environment the adhesive joints will be subjected to and its subsequent durability, and of course, cost. 

Adhesion promoter Various silanes and proprietary eomplex eompounds Enhanee adhesion of silieone to speeifie substrates. Prolonged durability. 

As coatings, silicones must exhibit strong and durable adhesion with the substrate on which they are cured. On the other hand, the surface of the cured... 

Surface cleaning/etches. As with aluminum and titanium, the most critical test for bonded steel joints is durability in hostile (i.e., humid) environments. The fact that the problem is a serious one for steel was illustrated in a study [117] that compared solvent cleaned (smooth) 1010 cold-rolled steel surfaces with FPL aluminum (microrough) substrates. Although the dry lap-shear strengths were not markedly different, stressed lap-shear joints of steel adherends that were exposed to a humid environment failed in less than 30 days, whereas the aluminum joints lasted for more than 3000 days. 

As polymer chemistry advanced in the 1930s and 1940s, stronger and more durable synthetic adhesives such as early phenol, resorcinol and urea formaldehydes began to supplant natural glues in wood aircraft manufacture. Around this time however, metal began to replace wood as the dominant material for aircraft manufacture. Aerospace adhesives research and development moved on to focus on metals, primarily aluminum, as the substrates of interest. 

Several coats of resin are applied to the prepared substrate at approximately 4- to 6-hour intervals, with one or more coats being dressed with colored paint flakes which are sealed in by the next coat and then lightly sanded. This type of flooring was widely marketed about ten years ago but, in the main, they were considered unsatisfactory due to rapid discoloration of the floor because of the lack of ultraviolet stability of the urethane resins used, which rapidly turned yellow-brown and looked dirty. However, ultraviolet-stable urethane resins that do not suffer this discoloration are now available, and this type of durable decorative flooring is gaining re-acceptance (for example, for kitchens, toilets and reception areas). 

Solvent-free high-build floor paints are available which can be readily applied with brush, roller or spray to a prepared concrete substrate to give a thickness of 0.10-0.20 mm per coat. Normally, two coats are applied and the first is often lightly dressed with fine sand or carborundum dust to give a non-slip, chemically resistant and durable colored floor, ideal for light industrial traffic conditions (for example, rubber-shod wheels). ... 

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