Bums, poly

Acrolein is highly toxic by skin absorption. Brief contact may result in the absorption of harmful and possibly fatal amounts of material. Skin contact causes severe local irritation and chemical bums. Poly(vinyl chloride) coated protective gloves should be used (99). 

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Figure 12.30 Potential uses of polyphosphazenes (a) A thin film of a poly(aminophosphazene) sueh materials are of interest for biomedical applications, (b) Fibres of poly[bis(trifluoroethoxy)phosphazene] these fibres are water-repellant, resistant to hydrolysis or strong sunlight, and do not burn, (c) Cotton cloth treated with a poly(fluoroalkoxyphosphazene) showing the water repellaney eonferred by the phosphazene. (d) Polyphosphazene elastomers are now being manufaetured for use in fuel lines, gaskets, O-rings, shock absorbers, and carburettor eomponents they are impervious to oils and fuels, do not bum, and remain flexible at very low temperatures. Photographs by eourtesy of H. R. Allcock (Pennsylvania State University) and the Firestone Tire and Rubber Company.

Poly(hydroxyethyl methacrylate) Soft contact lenses, bum dressings... 

Allied to flammability is smoke density suppression especially in confined spaces, e.g., airliners, houses, warehouses. Many aromatic compounds bum with a smoky flame (e.g., styrene), whereas corresponding aliphatic compounds tend to burn with a clean "transparent" flame. This is because air-bome poly-aromatic vapours decompose to give volatile carbon (smoke) in low oxygen environments. 

Accounting for these facts one should not be surprised coming across entirely different recommendations regarding the metal-acid-ethylene glycol ratio, which varies from 1-1.88-1.25 [5] or 1-4-1 [8] to 1-4.25-17.5 [7]. It is even sometimes noticed that a carboxylic acid and a poly hydroxy alcohol simply play the role of a fuel to bum a precursor and to form target oxides [16]. To shed some light on the aforementioned problems, the following steps could be of some help. 

W.J. Mitchell, C. Pena, and P.L. Bum, Thermal routes to low HOMO-LUMO energy gap poly(arylene vinylene)s, J. Mater. Chem., 12 200-205, 2002. 

Mahajan, R., Bums, R., Schaefer, M., and Koros, W.J. (2002) Challenges in forming successful mixed matrix membranes with rigid polymeric materials. /. Appl. Poly. Sci., 86, 881-890. 

Small quantities of explosive laboratory chemicals can be destroyed following known methods. By adopting standard methods, it is possible to destroy or reduce the dangerous nature of laboratory chemicals and check their reaction. Hydrocarbons (e.g., alkanes, alkenes, alkynes, arenas) bum well and can be disposed of by incineration or as fuel supplants. Also, many hydrocarbons commonly used in chemical laboratories may be easily ignited. Some cyclic compounds such as alkanes and cyclohexane may form explosive peroxides. Personnel trained in handling explosives should destroy these compounds using detonation. Many poly(nitro) aromatic compounds are explosive, and their disposal requires the services of an expert. 

Lu Y, Yang H, SeUinger A, Lu M, Huang J, Fan H, Haddad R, Lopez G, Bums AR, Sasaki DY, Shelnutt J, Brinker CJ (2001) Self-assembly of mesoscopicaUy ordered chromatic poly-diacetylene/sUica nanocomposites. Nature 410 913-917... 

The flammability of plastics can be a useful tool in their identification, but the additives present have an influence on their ability to bum. A clear test to indicate the presence of chlorine, mainly found in PVC and poly(vinylidene chloride) is the Beilstein test. A clean, copper wire 30-40 cm long, with a cork or other heat-insulating material at one end as a handle, is heated with a Bunsen burner to clean it of residual impurities, heating it until the flame is colourless. The hot, cleaned wire is placed in contact with the plastic to be analysed so that a small piece is melted onto it. The wire is returned to the flame and the colour noted a green or blue-green flame denotes the presence of chlorine while other colours suggest the plastic to be other than PVC or poly(vinylidene chloride). 

Virgin (rigid) poly(vinyl chloride) contains about 51% chlorine and shows low flammability. PVC-based WPCs have FSI between 25 and 60. When bums, PVC pyrolyzes to form HCl and volatile organic (aromatic) compounds, which evolve large amounts of smoke. 

Many polymers can be roughly identified by their behavior when carefully heated and ignited. Nitrocellulose and plastics containing this (e.g., celluloid) bum with explosive violence and other materials such as poly(vinyl chloride) or fluoro-hydrocarbons decompose with the evolution of poisonous or irritating vapors. Only... 

Bum PL, Bradley DDC, Brown AR, Friend RH, Holmes AB. Studies on the efficient synthesis of poly(phenylenevinylene) (PPV) and poly(dimethoxy phenyleneviny-lene) (dimethoxy-PPV). Synth Met 1991 41(1-2) 261. ... 

Kim SM, Bums MA, Hasselbrink EF (2006) Electro-kinetic protein preconcentration using a simple glass/ poly(dimethylsiloxane) microfluidic chip. Anal Chem 78(14) 4779 785... 

Staphaseptic is a new approach to wound care. Use in place of a triple antibiotic or poly-biotic ointment as an everyday infection prevention product for minor cuts, scrapes, abrasions and bums. Simply cleanse the wound and apply Staphaseptic before a bandage. For a free sample contact JaneUe Nichols at jnichols teclabsinc. com. Tec Labs, www.teclabsinc.com, (800) 482-4464. Circle 279... 

Carpick, R.W., T.M. Mayer, D.Y. Sasaki, and A.R. Bums. 2000. Spectroscopic ellipsometry and fluorescence study of thermochromism in an ultrathin poly(diacetylene) film Reversibility and transition kinetics. Langmuir 16 4639. 

Marks, R.N., D.D.C. Bradley, R.W. Jackson, P.L. Bum, and A.B. Holmes. 1993. Charge injection and transport in poly(p-phenylene vinylene) light-emitting diodes. Synth Met 55-57 4128-4133. 

To provide a prolonged and controlled drug release to the surface of wounds or bums, the material may contain two or more microfiber layers. Different layers may have different compositions. Each layer includes the biodegradable polymer with or without poly(N-vinyl)lactam. The layers may also have different biodegradable polymers (78). 

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