Resistance to Microorganisms

Resistance to Microorganisms and Insects. Resistance of triacetate to microorganisms, based on soil-burial tests, is high, approaching that of polyester, acryUc, and nylon fibers. Sod-burial test results on acetate, triacetate, and cotton are shown in Figure 8. Neither acetate nor triacetate fiber is readdy attacked by moths or carpet beedes. 

Nonmetallic materials should have the following desirable characteristics low moisture absorption, resistance to microorganisms, stability through temperature range, resistance to flame and arc, freedom from out-gassing, resistance to weathering, and compatibility with other materials. 

Urea-formaldehyde resins are used as the main adhesive in the forest product industry because they have a number of advantages, including low cost, ease of use under a wide variety of curing conditions, low cure temperatures, water solubility, resistance to microorganisms and to abrasion, hardness, excellent thermal properties, and a lack of color, especially in the cured resin. 

UV, hydrolysis and/or heat stabilized lower cost improved colour and gloss retention cold-temperature ductility and flexibility soft touch food contact fireproofed low compression set and creep reduced oil swelling improved chemical resistance better resistance to microorganisms transparent colourable glass fibre reinforced antistatic grades... 

Other 2-ethylhexanol based plasticizers were introduced, including some which imparted outstanding low temperature flexibility—dioctyl adipate (DOA), dioctyl azelate (DOZ), dioctyl sebacate (DOS), and trioctyl phosphate (TOF). In addition, TOF showed high resistance to microorganisms which was important in military applications. Furthermore, TOF improved flame resistance. However, the mixed ester—octyl diphenyl phosphate—also introduced in the forties—was far superior and showed a better balance of low temperature performance and flame resistance than either TOF or the well-established plasticizer—tricresyl phosphate (TCP). Each of these found a market as a specialty plasticizer because of these specific performance attributes. None, however, was a serious threat to DOP on an overall price-performance basis. Rather, they were used to supplement the properties of DOP where its performance was inadequate. 

Acetate is also derived from wood pulp, is treated in acetone, and then is extruded through a spinneret into a stream of warm air. In triacetate the hydroxyl groups of the cellulose molecules are completely replaced by acetyl groups, which further alter the properties of the fiber, giving it fewer cellulose characteristics. It has a higher resistance to microorganisms than viscose and has been used to impart easy-care properties to fabrics (Cowan and Jungerman 1962). 

Vapor or Spraying Applications. Cyanoethylation. Reaction of cellulose with acrylonitrile, CH2=CHCN, a vinyl monomer, was selected for study because it is known to produce several desirable changes in the properties of cellulosic fabrics and yams. After cyanoethylation, undegraded cotton becomes more resistant to microorganism attack, heat, acid, and abrasion (3). Moisture absorption decreases and the electrical properties change. The extent of these changes varies considerably... 

The first membranes used, based on cellulose acetate, were uot very resistant to microorganisms, shocks, temperature or pH. Second-generation membranes, made from polysulfone or polyacrylonitrile polymers, were much tougher. Cur-reut third-geueration inorganic membranes have good chemical, physical and heat (temperature >100°C) resistance characteristics. They have almost unlimited lifetimes and are easily cleaned and disinfected. The operating parameters are as follows (a) transmembrane differential pressure,... 

Coating type Chemical and solvent resistance Moisture and humidity resistance Weatherabi 1 i ty Resistance to microorganisms Flamma- bility... 

A different use for antimicrobials is in polymers that are inherently resistant to microorganisms and do not contain susceptible additives, but are frequently used in hygiene-conscious environments like hospitals, bathrooms and kitchens. There has been a rapid increase in the use of antimicrobial additives in the last four years to protect or reassure the user, rather than the product. Typical applications include kitchen surfaces and chopping boards, toothbrushes, rubbish cans, air filters, mattresses, and the ceilings, wallcoverings and floors of canteens and hospitals. Certain medical devices may also have biocidal protection. 

Excepting polymers having ester groups in the main chain, the synthetic polymers with MW > 1 kg/mol are resistant to microorganisms attack. By contrast, most natural... 

It must be resistant to microorganisms which might otherwise attack the materials which it contains. 

Physiological purity Resistance to microorganisms Taste neutrality Use under pressure Operating temperatures... 

Copolymers made from vinyl chloride and vinyl acetate are resistant to microorganisms in their pure state. However, their resistance decreases sharply with non-resistant plasticizer content here, they resemble PVC [32]. 

Plasticizer-free polymethyl methacrylate is resistant to microorganisms, while plasticized PMMA can be attacked by mold. This can significantly alter its mechanical properties [32]. 

Cellulose and its derivatives exhibit little resistance to microorganisms. Cellulose acetate, acetobutyrate, propionate, and nitrate are attacked by mold, bacteria, and yeast [32]. In soil, microorganisms degrade cellulose acetate to carbon dioxide, oxygen, water, and humus. Ethyl cellulose is the most resistant cellulose derivate, presuming it does not contain non-resistant plasticizers. Interestingly enough. 

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