Degradation of polypropylene

Kinetic Model Development Our kinetic model for the degradation of polypropylene Q.) is based upon the following reaction mechanism ... 

The catalytic degradation of polypropylene was carried out over ferrierite catalyst using a thermogravimetric analyzer as well as a fixed bed batch reactor. The activation of reaction was lowered by adding ferrierite catalyst, which was similar with that from ZSM-5. Ferrierite produced less gaseous products than HZSM-5, where the yields of i-butene and olefin over ferrierite were higher than that over HZSM-5. In the case of liquid product, main product over ferrierite is C5 hydrocarbon, while products were distributed over mainly C7-C9 over HZSM-5. Ferrierite showed excellent catalytic stability for polypropylene degradation. 

Stearamide is one of many electron donors which donate an electron to the cationic moiety in excited MAH or in propagating -MAH chains. This results in the inhibition of the homopolymerization of MAH and decreases the crosslinking of polyethylene and the degradation of polypropylene which accompany the peroxide-catalyzed reaction of MAH with these polyolefins (8,9). ... 

Oxidative degradation of polypropylene chemically incorporates oxygen to the polymeric chains. Why would an isotactic polypropylene be less susceptible to this type of degradation than one that is atactic ... 

The photo-oxidative degradation of polypropylene (PPH) can be largely summarized by the reactions 1 to h ( l,2j. During the... 

I. Blakey, Thesis Aspects of oxidative degradation of polypropylene, Queensland University of Technology, Brisbane, Australia, 2001. 

Table 3.14 Examples of UV exposure time to reach the same level of degradation of polypropylene according to the colorant...

Degradation reactions Degradation of polypropylene by shear-heating, degradation of PET with ethylene glycol... 

R. Bernstein, S.M. Thornberg, R.A. Assink, A.N. Irwin, J.M. Hochrein, J.R. Brown, D.K. Derzon, S.B. Klamo, and R.L. Clough, The origins of volatile oxidation products in the thermal degradation of polypropylene, identified by selective isotopic labeling. Polym. Degrad. Stab., 92, 2076-2094 (2007). 

Bockhorn, H., Homung, A., Homung, U., and Schwaller, D. Kinetic study on the thermal degradation of polypropylene and polyethylene. Journal of Analytical and Applied Pyrolysis 1999 48 17. 

F). To prevent degradation it is necessary to take account not only of the stability or instability of a compound but also of questions such as the period of time at the temperature, whether oxygen is present or the surrounding atmosphere is inert, and what materials are in contact with the plastic. As an example of the last, copper causes rapid degradation of polypropylene, and therefore copper cleaning pads should not be used on equipment for processing this material. 

New phenolic phosphites prepared from dihydric phenols and phosphorus halides prevent degradation of polypropylene by heat, oxidation, processing, and ultraviolet radiation. These products are active and synergistic with dithiopropionate esters. They seem to function as both free radical scavengers and peroxide decomposers. 

Processing Stability. The ability of tris (nonylphenyl) phosphite to prevent degradation of polypropylene during processing is believed related to its efficiency to decompose peroxides into non-active species. In a similar way, the phosphite groups on the polymeric phosphites may also be capable of decomposing peroxides (see top of p. 217). 

Y. Uemichi, Y. Kashiwaya, M. Tsukidate, A. Ayame, and H. Kanoh, Product distribution in degradation of polypropylene over Silica-Alumina and CaX zeolite catalysts, Bull. Chem. Soc. Jpn. 56, 2768 (1983). 

R. C. Mordi, R. Fields, and J. Dwyer, Gasoline range chemicals from zeolite-catalysed thermal degradation of polypropylene, J. Chem. Soc., Chem. Commun. 374 (1992). 

Audiso et al. [25] has studied the catalytic degradation of polypropylene using silica, alumina and silica-alumina and zeolite catalysts in the range 200-600°C. The main products in oil production using more efficient catalyst were C5-C12 olefins. Also the... 

G. Audiso, A. Silvani, P. L. Beltrame and P. Camiti, Catalytic thermal degradation of polymers degradation of polypropylene, J. Anal. Appl. Pyrolysis 1, 83-90 (1984). 

Y. Uemichi, Y. Makino and T. Kanazuka. Degradation of polypropylene to aromatic hydrocarbons over Pt- and Fe-containing activated carbon catalysts. Journal of Analytical and Applied Pyrolysis, 16, 229-238 (1989). 

Y. Sakata, M. A. Uddin, K. Koizumi, and K. Murata, Catalytic degradation of polypropylene into liquid hydrocarbons using silica-alumina catalyst, Chem. Lett., 245-246 (1996). 

It is evident in Figures 30.18 and 30.19 that, after the accelerated adhesion test, the primer-coated air LPCAT treated TPOs showed poor adhesion performance as compared to argon and methane LPCAT-treated TPOs. This is a clear indication that air-plasma treatment can achieve the paintable surface but cannot provide the treated surface that can be painted in a durable manner. The poor durability can be attributed to (1) the water-sensitive nature of adhesion and (2) the excessive degradation of polypropylene that causes weaker boundary layer. 

The volatile products of thermal degradation of polypropylene (PP) under vacuum in the temperature range 300-360°C comprise a complex mixture of saturated and unsaturated hydrocarbons. Under u.v. radiation at these temperatures (photothermal degradation), the general pattern of products is similar but the rate is Increased, ehtylene appears as a minor product and the relative amount of methane is very much greater, especially as the temperature Is decreased below 300°C. Energies of activation of the thermal, photothermal and photoreactions are 50.1, 33.9 and 11.7 k cal mole" respectively. 

Infra-red spectra of the products, volatile at ordinary temperatures, of the thermal degradations represented in figure 9 are a superlmposltlon of the spectrum of methyl methacrylate monomer on that of the volatile products of the thermal degradation of polypropylene. However, the amount of methyl methacrylate, as measured by the optical density of the carbonyl peak at 1740 cm , is strongly suppressed by pre-irradiation, as shown in figure 10. 

Silica and other fillers affect thermal stability indirectly by adsorbing thermal stabilizers which prevents them from acting as stabilizers. Some zeolites were used to catalyze the degradation of polypropylene during waste processing. The type of cation was essential in decreasing the degradation temperature (e.g., Na )."... 

Scheme 3.1. Formation of oxidation products in the degradation of polypropylene through the tertiary hydroperoxide intermediate that may he identified by MIR spectroscopy (often combined with derivatization). After Blakey (2001).

Blakey, I. (2001) Aspects of the oxidative degradation of polypropylene. Thesis, School of Physical... 

This reaction was reported for the benzophenone photosensitized degradation of polypropylene (92),polystyrene (95), poly(vinyl alcohol) (94),polyisoprene (95,96),polyurethane (97) and polyadenylic acid (98) In solid state benzophenone also produce an extensive crosslinking of polyethylene (99-105) It has also been found that benzophenone and its derivatives caused an initial rapid oxidation,increasing with ketone concentration (70) Currently the relative importance of singlet oxygen formation in energy transfer reaction between excited benzophenone and molecular oxygen is discussed (92,104) ... 

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