Stabilizers polymeric ultraviolet

We have shown that polymeric stabilizers, polymeric ultraviolet stabilizers, and polymeric antioxidants are effective in retarding photooxidation and thermal oxidation in polymers. Polymeric stabilizers are not volatile, not extractable or leachable, and do not provide the undesirable characteristics of toxicity, potential carcino-... 

It is primarily the prospect of reduced mobility and volatility, with the expected improvement in long-term performance, which motivates the preparation of polymeric ultraviolet stabilizers. Work in this area was reviewed thoroughly by Bailey and Vogl in 1976 (1), and more recently by the author (2). The present paper describes recent synthetic work involving four classes of effective ultraviolet stabilizers salicylate esters (I), 2-hydroxybenzophenones (II), a-cyano-3-phenyl-cinnamates (III) and hydroxyphenylbenzotriazoles (IV). In each... 

Radical polymerizations of vinyl-substituted ultraviolet stabilizers were accomplished with azobisisobutyronitrile (AIBN) as initiator, with careful exclusion of oxygen. Copolymerization was also readily achieved. The following sections describe in detail the preparation of polymeric ultraviolet stabilizers from salicylate esters, 2-hydroxybenzophenones, a-cyano-p-phenyl-cinnamates and hydroxyphenylbenzotriazoles. 

Each of the derivatives may be regarded as a substituted styrene, and classical styrene syntheses have been employed. Radical polymerization of the phenolic monomers (salicylate esters, 2-hydroxybenzophenones and hydroxyphenylbenzotriazoles) proceeds normally with AIBN as initiator, at least when oxygen is carefully excluded. It is expected that polymeric ultraviolet stabilizers, perhaps in combination with conventional stabilizer will make an important contribution to photostabilization technology. 

Persistence is the net result of many interacting factors, but chemical properties of the pesticide can play a dominant role. Volatility, solubility, stability to ultraviolet irradiation, tendency to adsorb onto or dissolve into tissue surfaces, ease of hydrolysis, sensitivity to humidity, potentiality to polymerize with or without ultraviolet irradiation, possible isomerization or other molecular rearrangement are all important chemical properties which play a significant role in persistence. Weather conditions such as wind, rain, amount and intensity of light, air temperature, and humidity play important roles. Rainfall is usually con-... 

M. Rahman and C. S. Brazel, Effectiveness of phosphonium, ammonium and imida-zolium based ionic liquids as plasticizers for poly(vinyl chloride) Thermal and ultraviolet stability. Polymeric Preprints (American Chemical Society Division of Polymer Chemistry), 45 (2004), 301-2. 

In suspension polymerization, liquid vinyl fluoride was suspended in water with the help of a dispersion stabilizer. Polymerization was initiated by an organic peroxide such as diisopropyl peroxydicarbonate below the critical temperature of vinyl fluoride.bo lb ] The reaction could also be initiated by ultraviolet light and ionizing radiation.VF dispersions were usually stabilized by water-soluble polymers such as cellulose derivatives like cellulose ester and sodium car-boxymethylcellulose, andpoly(vinyl alcohol). Inorganic salts such as magnesium carbonate, barium sulfate, and alkylsulfoacids were also used. 

Geotextiles may be woven, nonwoven, or knitted. AH types, woven, nonwoven, or knitted, are susceptible to degradation owing to the effects of ultraviolet light and water. Thus stabilizing agents are added to the base polymeric material to lessen the effects of exposure to ultraviolet light and water. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials No reactions Stability During Transport Stable Neutralizing Agemsfor Acids and Caustics Not pertinent Polymerization Polymerizes when exposed to heat, ultraviolet light, or free-radical catalysts Inhibitor of Polymerization 200 ppm Hydroquinone. 

The incorporation of four different classes of important ultraviolet stabilizers into high polymer chains has been accomplished by synthesis of polymerizable, vinyl-substituted stabilizer derivatives followed by radical polymerization. 

Uses. In ultraviolet stabilizers and smoke depressants for polymers to increase the burn rate of rocket propellants to prevent erosion of space capsule shields to improve the viscosity of lubricants to catalyze polymerization reactions to catalyze combustion some derivatives used as hematinic agents... 

Dark Stability. The examples cited have demonstrated that dye sensitized photopolymerization is potentially rapid in solution, but that substantial speed losses result when polymeric binder compositions are used in an imaging fashion. Our work has shown that TBBS activated compositions sensitized by MB can exhibit absolute photospeeds to red light that are comparable to those of commerical photopolymer systems that are sensitive only to ultraviolet wavelengths (65). These systems can offer features not now available in UV-only sensitive systems. The major failure of all such systems, however, is a pronounced lack of stability on dark storage for the lengths of time required by industry standards. 

The same chromophore is present in the p-quinonemethide precursors of DL-pinoresinol (twice) and dehydrodiconiferyl alcohol (once). Measurements in a fast-recording ultraviolet spectrometer (Cary apparatus) indicated a half-life of the quinonemethides of about 1 hour (dilute solution in 70% aqueous dioxane at 20°C. and pH 5.5) (5, 18). They may also become stabilized to a small extent by polymerization (see XLIV). Since the quinonemethide (XXI) has no opportunity to become stabilized by intramolecular prototropy, it adds on external electrolytes, particularly hydroxyl compounds and preferably water 31). 

Most ABS is made by emulsion polymerization. A polybutadiene or nitrile rubber latex is prepared, and styrene plus acrylonitrile are grafted upon the elastomer in emulsion. The effect of rubber particle size in ABS graft copolymer on physical properties is the subject Chapter 22 by C. F. Parsons and E. L. Suck. Methyl methacrylate was substituted for acrylonitrile in ABS by R. D. Deanin and co-workers. They found a better thermoprocessability, lighter color, and better ultraviolet light stability. 

Four main types of antioxidants are commonly used in polypropylene stabilizer systems although many other types of chemical compounds have been suggested. These types include hindered phenolics, thiodi-propionate esters, aryl phosphites, and ultraviolet absorbers such as the hydroxybenzophenones and benzotriazoles. Other chemicals which have been reported include aromatic amines such as p-phenylenediamine, hydrocarbon borates, aminophenols, Zn and other metal dithiocarbamates, thiophosphates, and thiophosphites, mercaptals, chromium salt complexes, tin-sulfur compounds, triazoles, silicone polymers, carbon black, nickel phenolates, thiurams, oxamides, metal stearates, Cu, Zn, Cd, and Pb salts of benzimidazoles, succinic acid anhydride, and others. The polymeric phenolic phosphites described here are another type. 

Here we discuss a new class of polypropylene stabilizers—the polymeric phenolic phosphites. These compounds exhibit unique, broad-spectrum activity which may allow simplification of polypropylene stabilizer systems. The most active species are synergistic with thiodipro-pionate esters, are effective processing stabilizers when used alone or with other compounds, and contribute to photostability. Compounds of this type appear to function as both free radical scavengers and peroxide decomposers, and through a mechanism not yet completely understood, allow significant reductions in the concentration of ultraviolet absorbers required to achieve high levels of photostability. 

The significance of the interaction between PPP and ultraviolet absorbers, such as the hydroxybenzophenones, becomes evident when the high cost of absorbers is considered. The potential cost for polymeric phenolic phosphites is low by comparison. By using a polymeric phenolic phosphite in place of a normal hindered phenolic in the heat-stabilizer system, enhanced photostability is obtained, and less ultraviolet absorber is required for a given degree of stability. 

---