Polymer degradation polyolefins

Pyrolysis GC/MS is limited in application to those studies in which the compounds formed are capable of being analysed by GC, that is it is only reasonably suitable for low molecular weight products. Many synthetic polymers degrade (pyrolyse) by processes that may simply be described as either random scission (e.g., polyolefins), unzipping to produce mostly monomers (e.g., PMMA)... 

A few relatively recent published examples of the use of NMR spectroscopy for studying polymer degradation/oxidation processes will now be discussed briefly. At the early stages of degradation, the technique can be used to provide chemical identification and quantification of oxidised species for polyolefins, oxidation sites can be identified by the chemical shifts of -CH2- groups a and ji to carbons bonded to oxygen [85]. Spin-spin relaxation times may be determined by a pulse sequence known as the Hahn spin-echo pulse sequence. 

T.J. Henman, Characterisation of oxidised polyolefines by reaction with sulphur dioxide. In N. Grassie (Ed.), Developments in Polymer Degradation-6, Elsevier Applied Science, Barking, 1985, pp. 107-145. 

Xie, R.C. and Qu, BJ. 2001. Synergistic effects of expandable graphite with some halogen-free flame retardants in polyolefin blends. Polymer Degradation and Stability 71(3) 375-380. 

Ravadits, I., Toth, A., Marosi, G., Marton, A., and Szep, A. 2001. Qrganosilicon surface layer on polyolefins to achieve improved flame retardancy through an oxygen barrier effect. Polymer Degradation and Stability 74 419-22. 

Gugumus FL, "Polyolefin Stabilization From Single Stabilizers to Complex Systems", in Hamid SH (Ed) "Handbook of Polymer Degradation", Marcel Dekker, New York, 2nd Ed, 2000, Chap. 1. 

M. Predel and W. Kaminsky, Pyrolysis of mixed polyolefins in a fluidized - bed reactor and on a pyro-GC/MS to yield ahphatic waxes. Polymer Degradation and Stability, 70, 373 (2000). 

J. Gonzalez, C. Albano, M. Ichazo, M. Hernandez and R. Sciamanna, Analysis of thermogravimetric data of blends of polyolefins with calcium carbonate treated with Lica 12, Polymer Degradation and Stability, 73, 211-224 (2001). 

U. Arena, M. L. Mastellone, G. Camino and E. Boccaleri, An innovative process for mass production of multi-wall carbon nanotubes by means of low-cost pyrolysis of polyolefins. Polymer Degradation and Stability, 91, 763-768 (2006). 

Recently the pyrolysis of polymer mixtures has become a focus of interest due to the increasing role of plastics recycling. Many researchers have investigated the thermal decomposition of various polymers in the presence of PVC. Kniimann and Bockhom [25] have studied the decomposition of common polymers and concluded that a separation of plastic mixtures by temperature-controlled pyrolysis in recycling processes is possible. Czegfny et al. [31] observed that the dehydrochlorination of PVC is promoted by the presence of polyamides and polyacrylonitrile however, other vinyl polymers or polyolefins have no effect on the dehydrochlorination. PVC generally affects the decomposition of other polymers due to the catalytic effect of HCI released. Even a few per cent PVC has an effect on the decomposition of polyethylene (PE) [32], HCI appears to promote the initial chain scission of PE. Day et al. [33] reported that PVC can influence the extent of degradation and the pyrolysis product distribution of plastics used in the... 

J. Aguado, D. P. Serrano, J. M. Escola, E. Garagorri and J. A. Fernandez, Catalytic conversion of polyolefins into fuels over zeolite beta, Polym. Degrad. Stab., 69, 11-16 (2000). 

Fig. 10 Strain at break Vs. UV exposure time for polypropylene copolymer bars made from (a) virgin polymer (V) (b) virgin polymer + undegraded recyclate (U) (c) virgin polymer + photodegraded recyclate (P). Results for blends with recyclate contents of 10% and 25% are shown. (More details in Craig, I.H. White, J.R. Mechanical properties of photo-degraded recycled photo-degraded polyolefins. J. Mater. Sci. 2006, in press.)...

N.S. Allen, A. Parkinson, F.F. Loffelman, and P.V. Susi, Photo-Stabilising action of ap-hydroxybenzoate compound in polyolefins. Part I. Thermal and photochemical behaviour in polypropylene film, Polym. Degrad. Stab. 1983, 5, 241-266. 

D.W. Grattan, D.J. Carlsson, and D.M. Wiles, Polyolefin photo-stabilisation mechanisms. Reaction of tetramethylpiperidine derivatives in model systems, Polym. Degrad. Stab. 1979, 1, 69-84. 

F. Gugumus, Possibilities and limits of synergism with light stabilizers in polyolefins 1. HALS in polyolefins, Polym. Degrad. Stab. 2002, 75, 295-308. 

A pioneering and comprehensive study of the effect of copper on the thermal oxidative degradation of polyolefins has been made by a Bell Laboratories research group (1-6). They found that surface reactions at the interface between metal and polymer are important factors in many applications including metal-polymer composites, polyolefin-insulated... 

TV/Tetal surfaces often have adverse catalytic effects on the rates of oxidative degradation (by molecular oxygen) of polymers, particularly polyolefins. Previous papers in this series have shown for the specific case of the 02/polyethylene/copper system between 40 °C and 90 °C that copper carboxylate salts, initially formed at the interface, are re-... 

Contat-Rodrigo, L., Haider, N., Ribes-Greus, A., and Karlsson, S., Ultrasonication and microwave-assisted extraction of degradation products from degradable polyolefin blends aged in soil, J. Appl. Polym. Set, 79, 1101-1112, 2000. 

CORl s are the prime machines for polymer blending and reactive extrusion [Brown, 1992]. They have been used as reactors for the addition polymerization (polyacrylates, SAN, S-MMA, PA-6, POM, or TPU) and for the polycondensation (PA-66, polyarylates, PEST, PEI). Polymer grafting (polyolefin + silane, maleic anhydride, acetic anhydride, etc.) as well as mechanical and chemical degradation of polypropylene have also been carried out. 

In the presence of oxygen or ozone, as soon as free radicals form, oxygenation of the radicals gives rise to peroxy radicals, which through a complex series of reactions result in polymer degradation. Oxidative degradation may occur at moderate temperature (thermal oxidation) or under the influence of ultraviolet radiation (photooxidation). Unsaturated polyolefins are particularly susceptible to attack by oxygen or ozone (Equation 9.6). 

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