Oxidation of polystyrene

Figure 6 (A) Non-isothermal chemiluminescence runs for oxidation of polystyrene (PS), polyethylene terephthalate) (PETP) and polyfmethyl methacrylate) (PMMA), in oxygen, heating rate 2.5°C/min. (B) Non-isothermal chemiluminescence runs for oxidation of polypropylene (PP), polyamide 6 (PA 6), poly(vinyl pyrrolidone) (PVP), polyethylene (PE) and polyamide 66 (PA 66), in oxygen, heating rate 2.5°C/min.

G. Geuskens, D. Baeyens Volant, G. Delaunois, Q. Lu Vinh, W. Piret, and C. David, Photo oxidation of Polymers II. The Sensitized Decomposition of Hydroperoxides as the Main Path for Initiation of the Photo oxidation of Polystyrene Irradiated at 253.7 nm, Eur. Polym. J., 14, 299 303 (1978). 

Terminal air oxidation of polystyrene has recently been carried out by degradation of polystyrene in the presence of azo-bis-isobutyronitiile and air oxygen the polystyrene dihydroperoxide can initiate the polymerization of methyl methacrylate and acrylonitrile [193, 194). The yield of homopolymer is very low, indicating an exceptional difference of efficiency between the macroradical and the OH radical. 

Oxidation of Polystyrene and Pyrolytic Carbon Surfaces by Radiofrequency Glow Discharge... 

Photo-oxidation of polystyrene (254nm, AOOtorr oxygen)... 

It is illuminating to consider the effects of errors in activation energy on scaled tests. As an illustration, we draw on recent results for the oxidation of polystyrene (13). Table I shows the error in activation energy (a) at test temperatures of 100, 200, 300, 400 and 500 C which will result in errors in rates of 1, 5, 10, 25, 50, 100 and 250% at service conditions of 25 C. 

The greater the temperature difference between service life and accelerated test, the smaller the error in activation energy must be for a given error in scaled rate. In the oxidation of polystyrene between 225 C and 275 C, the final averaged activation energy is 21.5 0.2 kcal/mole. Using an error value of 2a 0.4 kcal/mole for a 95% confidence level, we estimate by interpolation in Table I that an error of 31% would be introduced into the calculated rate if the rates observed at v- 225 C were scaled to room temperature. 

We will now illustrate these points very briefly using our results (13) for the oxidation of polystyrene ... 

TFe activation energy for the oxidation of polystyrene is 21.5 .2 kcal/mole. 

Table 17. Oxidation of Polystyrene and Polylamine Resins in a One-Week Accelerated Test at 90°Cf ...

Grassie and Weir [254], Achhammer et al. [2] and Jellinek and Lipovac [313] have found that during photo-oxidation of polystyrene, C02 and H20 were the main volatile products, with others such as benzaldehyde, benzophenone and benzyl alcohol. 

Rabek [498, 505] examined the rapid degradation of cis-1,4-polyisoprene on exposure to light in the presence of p-quinones p-quinone, chloranil, 1,4-naphthoquinone, anthraquinone, phenanthrene-quinone and 1,2-benzanthraquinone (Fig. 20). Later, Rabek [504] also found that p-quinone sensitizes the photo-oxidation of polystyrene in benzene in the presence of UV radiation. 

Rabek [504] found that anthracene sensitizes the degradation and photo-oxidation of polystyrene in solution. It also sensitizes the degradation of cis-polybutadiene in benzene solution. 

Ranby et have also used model compounds such as 3-phenylpentane for investigating the mechanisms of photo-oxidation of polystyrene. The photooxidation of polystyrene has been investigated in solution by a number of workers. Woolinski has observed the development of unsaturation and implicated the involvement of singlet oxygen in the mechanism of photo-oxidation, whereas Easton and MacCallum " invoke the involvement of polymer-solvent complexes in initiation. The photo-oxidation of polystyrene has been found to have a kinetic chain length of 10 —... 

Waligora et have studied the sensitized photo-oxidation of polystyrene by a,jS-enones. These chromophores introduced an induction period due to... 

Wojtczak have found that the photosensitized degradation of polyethylene glycols decreases in the order triethylene glycol > polyethylene glycol 400 mol. wt. > polyethylene glycol 4000 mol. wt. Sastre and Gonzalez have shown that bromoalkanes are powerful sensitizers for the photo-oxidation of polystyrene, and Rabek and Ranby have found that polynuclear aromatics are photosensitizers for polybutadiene. Aromatic carbonyls have been shown to induce free-radical formation in cellulosic materials. 

Plasma oxidation versus photo oxidation of polystyrene, Polym. Commun. 32, 217 (1991) A.F. Whitaker and B.Z. Jang, The mass loss mechanisms of polymers in a radio frequency induced atomic oxygen environment, J. Appl. Polym. Sci. 48, 1341 (1993). 

Kirschning and coworkers have developed several polymer-supported halogen-ate(I) complexes [49-53]. Specifically, the polymer-supported diacetoxyiodine-ate(I) complex 29 was prepared by the oxidation of polystyrene-bound iodide 28 using (diacetoxyiodo)benzene (Scheme 5.16) [49]. 

B O Donnell and J R White, Photo-oxidation of polystyrene under load , J Mater Sci 1994 29 3955-3963. 

The above cases dealt with polymers that were chemically modified in solution. Chemical modification of surfaces of solid polymers is an attractive alternative technique. Oxidation of polystyrene surfaces has b rigShown to increase the negative charging capacity linearly.Introduction of carbonyl coo taining functionalities (acceptor groups) is known to occur. Oxidation and ozonization of branched (unsaturated) polyethylene surfaces led to ver. similar results, i.e., enhanced negative charging- capacity.Oxidation of coal was similar in effect. ... 

Fig. 46 Data obtained on PS/PSox patterned surfaces produced by photolithography and oxygen plasma oxidation of polystyrene (a) XPS mapping of the O Is peak intensity (obtained with a Kratos Axis Ultra spectrometer) (b) adhesion map obtained by AFM in water with a sUicon probe (vertical scale = 25 nN), revealing the hydrophobicity contrast in the pattern (c) ToF-SIMS image recorded with the signal of CNO ions on a patterned surface conditioned with a solution of flbronectin and Plutonic F68, revealing the selective adsorption of the extracellular matrix protein on the oxidized tracks and (d) micrograph of rat hepatocytes on a patterned substrate conditioned with a solution of type I collagen and Plutonic F68, showing the selective adhesion of the cells on the oxidized tracks. Adapted from Refs, 25 and 312...

Thermal oxidation of polystyrene is suppressed by adding phenols, such as 2,6 di-tert-butyl-p-cresol (BHT), long chain 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propion-ates or sebacates in combination with phosphorous compounds, such as substituted phenyl phosphites (TNPP) or phosphonites. Impact modified polystyrene is stabilized only by phenols, because phosphites affect the polymerization kinetics. 

During photo-oxidation of polystyrene carbon dioxide and water are also formed [834]. The quantum yield of COj formation depends on the measuring technique < co2 = 1-2 x 10 (from absorption on Carbosorb i.e. soda asbestos) or co2 = 8.3 X10 (from chromatographic measurements). The quantum yield of water formation is h20 = 9.5 x 10 [745]. 

The sample cell should be purged constantly with oxygen-free nitrogen to inhibit oxidation (see later section on oxidation of polystyrene). The samples should be stored under vacuum to eliminate absorbed oxygen. 

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