Polypropylene oxidation

Polypropylene differs from polyethylene in its chemical reactivity because of the presence of tertiary carbon atoms occurring alternately on the chain backbone. Of particular significance is the susceptibility of the polymer to oxidation at elevated temperatures. Some estimate of the difference between the two polymers can be obtained from Figure 1J.7, which compares- the rates of oxygen uptake of eaeh polymer at 93°C. Substantial improvements can be made by the inclusion of antioxidants and such additives are used in all commercial compounds. Whereas polyethylene cross-links on oxidation, polypropylene degrades to form lower molecular weight products. Similar effects are noted... 

Fig. 22 Images and data representing development and application of DLS on a chip a one iteration in the design of a microfluidic DLS fabricated from aluminum with the surface anodized black to reduce surface reflections b image of a microfluidic chip that integrates polymer synthesis with DLS. The machined channels have been covered by a Kapton sheet fixed with adhesive c data for temperature depended micelle formation of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (Pluronic P85) at 2% by volume in water. (Derived from [106] with permission)...

Enikolopyan NS, Grigorov LN, Smirnova SG (1989) Possible superconductivity near 300 K in oxidized polypropylene. JETP Lett 49 371-375... 

Compound Name N-Propyl Mercaptan Isopropyl Mercaptan N-Propyl Mercaptan Isopropyl Mercaptan Glycerine Propionic Acic Propionic Anhydride N-Propyl Alcohol Isopropyl Alcohol Beta-Propiolactone Acetone Acrolein Allyl Alcohol Acrylamide Propylene Propylene Oxide Polypropylene Acrylic Acid Beta-Propiolactone Propionaldehyde Propionic Acid Propionaldehyde Propionic Anhydride Beta-Propiolactone Propionic Anhydride N-Propyl Acetate Isopropyl Acetate N-Propyl Alcohol Isopropyl Alcohol N-Propyl Alcohol Propionaldehyde N-Butyl Alcohol Propylene... 

Cyclic Chain Termination in Oxidized Polypropylene Inhibition of Synthetic Rubber Degradation... 

The nonionic triblock copolymer polyethylene oxide-polypropylene oxide polyethylene oxide (PEO-PPO-PEO) has been widely used in medicine and has shown low toxicity. Wanka et al. [91] studied aggregation behavior of PEO-PPO-PEO polymeric micelles. In this study, the hydrophobic core of this micellar system consisted of dehydrated poly(oxy-propylene) groups which were surrounded by an outer shell of hydrated poly(oxyethylene) groups. The feasibility of using PEO-PPO PEO micelles as a topical ocular carrier for gene delivery was addressed in an in vivo study on nude mice and albino rabbits [92], Each animal eye was treated with a topical application (10 pL for mouse and 50 pL for rabbit) of 0.08 mg/mL of plasmid and 0.3% (w/v) PEO-PPO-PEO polymeric micelles. After 2 days of three times per day topical delivery, the reporter expression was detected in the treated eyes... 

Ring opening Polyamide 6 Polycaprolactone Polyethylene oxide Polypropylene oxide... 

Pluronics tri-block copolymer polyethylene oxide-polypropylene oxide-poly-ethylene oxide (PEO-PPO-PEO)... 

As it was demonstrated by staining the oxidized polypropylene and its observation by UV microscope, a high degree of inhomogeneity at the micron level was observed even for the most thoroughly annealed samples. In most cases this is clearly associated with the catalyst residues. An observation of microdomains in the oxidized polymer in which the degree of oxidation is by far pronounced than in the rest of polymer may be explained by the effect of higher oxidation state of transition metal ions M which interact directly with polymer ... 

Schillen K, Bryskhe K (1999) Vesicles formed from a polyethylene oxide) — polypropylene oxide) — poly(ethylene oxide) triblock copolymer in dilute aqueous solution. Macromolecules 32 6885-6888... 

Ethylene glycol Ethylene oxide Polypropylene EniChem... 

Pluronic polyethylene oxide-polypropylene oxide triblock surfactant, (EO)m(PO) (EO)m, for example, P123 = (EO)2o... 

Valenza, A. La Mantia, F.P. Recycling of polymers. Part 1. Photo-oxidized polypropylene. Polym. Degrad. Stab. 1987,19, 135-145. 

Secondary O/W emulsifiers High-HLB surfactants or polymers may be used, such as Tween 20, polyethylene oxide-polypropylene oxide (PPO) block copolymers (Pluronics) may be used. 

Termination. Just as peroxy radicals are key to the propagation sequence, so the bimolecular recombination of these radicals is the major termination process in the unstabilized polymer. The existence of an intermediate tetroxide has been established in solution (25). Several factors influence the competitive pathways of subsequent decomposition to form alcohols, ketone and singlet oxygen or to form alkoxy radicals which can couple before separation from the reaction center to form a peroxide. This latter process is a route to crosslinking in the case of polymeric peroxy radicals. The effect of steric control, viscosity and temperature have been studied in solution. However, in the solid phase the rates of bimolecular processes which require the mutual diffusion of the reactant groups will be limited by the diffusion process. As a standard, we have assumed a value close to that determined from oxygen absorption (26) and by ESR spectra (27) for oxidized polypropylene films. 

A comparison of the thermal stability of polyethylene oxide, polypropylene oxide, polyethylene and polypropylene has been presented by Madorsky and Straus [230]. More recently, studies on the thermal degradation of polytetramethylene oxide (I), polyhexamethylene oxide (II) and polydioxolane (III)... 

Carlsson and Wiles [36] have studied the change in the infrared spectrum and the composition of the volatile products evolved on irradiation of previously oxidized polypropylene. They conclude that the main reactions occurring during the photolysis are... 

Polymeric hydroperoxides are the major product of low temperature oxidation [Refs. 46, 113,115, 148, 189, 191, 193,195,196, 300]. Yields of hydroperoxides in oxidized polypropylene exceed 40%, and more than half that amount is contained in low molecular weight degradation products. It was shown that isolated hydroperoxide groups in thermally oxidized polypropylene constitute less than 10% of the total hydroperoxide concentration, and the majority of the polypropylene hydroperoxide groups occur in dimers, trimers, or longer sequences [148]. 

Fig. 3. Infrared spectra of oxidized polypropylene and polyethylene (20 mil sheets) in O—H region (The dotted lines refer to O—H absorption after hydroxyperoxide decomposition at high temperature under nitrogen.) [5].

FUNCTIONAL GROUP CONTENT IN THERMALLY OXIDIZED POLYPROPYLENE AND POLYETHYLENE [5, 7]... 

CONDENSABLE PRODUCTS FROM IRRADIATED, OXIDIZED POLYPROPYLENE 122]... 

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