Polypropylene, radiation

Garcia-Uriostegui, L., Burillo, G., and Bucio, E. 2012. Synthesis and characterization of thermosensitive interpenetrating polymer networks based on N-isopropylacrylamide/N-acryloxysuccinimide, crosslinked with polylysine, grafted onto polypropylene. Radiat Phys Chem. 81 295-300. 

Guimon, C. 1979. Radiation grafting of high density poly-ethylene and polypropylene. Radiat Phys Chem. 14 841-846. 

Computer>aided simulation of injection moulding of a polypropylene radiator f cowl, (a) Mesh of triangular elements used in the numerical analysis of melt flow, (b) Positions of melt fronts predicted for various times (in seconds) from the start of mould-filling. The mould is full within approximately 3 seconds. (After C. R. Fenn and M. Sharrock, Chloride Lorivail Ltd., and Larufrover UK Ltd.)... 

Nedkov and Dabreva [18] showed that in isotactic polypropylene, radiation doses up to 100 kGy improve crystalline perfection, but with high gamma radiation doses up to 200 kGy, damage occurs in both the crystal and amorphous laminar parts of the polypropylene. 

Jia, H., Wang, H., Chen, W. The combination effect of hindered amine light stabilizers with UV absorbers on the radiation resistance of polypropylene. Radiat. Phys. Chem. 76, 1179-1188 (2007)... 

Laboratory tests indicated that gamma radiation treatment and cross-linking using triaHylcyanurate or acetylene produced a flexible recycled plastic from mixtures of polyethylene, polypropylene, general-purpose polystyrene, and high impact grade PS (62). 

Polypropylene molecules repeatedly fold upon themselves to form lamellae, the sizes of which ate a function of the crystallisa tion conditions. Higher degrees of order are obtained upon formation of crystalline aggregates, or spheruHtes. The presence of a central crystallisation nucleus from which the lamellae radiate is clearly evident in these stmctures. Observations using cross-polarized light illustrates the characteristic Maltese cross model (Fig. 2b). The optical and mechanical properties ate a function of the size and number of spheruHtes and can be modified by nucleating agents. Crystallinity can also be inferred from thermal analysis (28) and density measurements (29). 

Degradation of polyolefins such as polyethylene, polypropylene, polybutylene, and polybutadiene promoted by metals and other oxidants occurs via an oxidation and a photo-oxidative mechanism, the two being difficult to separate in environmental degradation. The general mechanism common to all these reactions is that shown in equation 9. The reactant radical may be produced by any suitable mechanism from the interaction of air or oxygen with polyolefins (42) to form peroxides, which are subsequentiy decomposed by ultraviolet radiation. These reaction intermediates abstract more hydrogen atoms from the polymer backbone, which is ultimately converted into a polymer with ketone functionahties and degraded by the Norrish mechanisms (eq. 

Photodegradation of polyethylene waste can be markedly accelerated via its grafting with acrylamide [98], In contrast, photostabilization of polyethylene and polypropylene can be achieved as a result of the grafting of 2-hydroxy-4-(3-methacryloxy-2-hydroxy-propoxy) benzophenone using gamma radiation [ 147], In this case, the grafted compound acting as a U V stabilizer is chemically bound to the backbone chain of the polymer and its evaporation from the surface can be avoided. 

Polypropylene, natural Poor/Fair affected color-corrected radiation formulations are available. Physical properties greatly reduced when... 

Polypropylene, stabilized irradiated. Radiation-stabilized grades,... 

Additive-free film samples of isotactic polypropylene (iPP, 30pm Himont Profax resin) and polyethylenes (LLDPE, 120ym, linear low density DuPont Sclair resin, and UHMW-PE, 120wm, ultra high molecular weight, high density Himont LSR 5641-1B resin) were oxidized by exposure in air to y-radiation (AECL Gamma Cell 220, 1.0... 

Simulation programs for the ESR line shapes of peroxy radicals for specific models of dynamics have been developed for the study of oxidative degradation of polymers due to ionizing radiation [66]. The motional mechanism of the peroxy radicals, ROO, was deduced by simulation of the temperature dependence of the spectra, and a correlation between dynamics and reactivity has been established. In general, peroxy radicals at the chain ends are less stable and more reactive. This approach has been extended to protiated polymers, for instance polyethylene and polypropylene (PP) [67],... 

A polypropylene square slab, 0.3 m on a side, bums in a steady manner. Polypropylene does not char, and it can be considered that its radiation characteristics do not vary, with the flame radiative fraction at 0.38 and the flame incident heat flux to the fuel surface at 25 kW/m2. It burns in a wind as shown in various conditions as specified. Its convective heat transfer coefficient can be taken as 50 W/m2 K. The properties of polypropylene are listed as follows. 

Several polyheterocyclic compounds containing a condensed 1,2,4-triazole nucleus, such as 3,5-disubstituted thiazolo [2,3-r][ 1,2,4] triazoles, are thermostabilizers for polypropylene and polycaproamide <2003MI2>. Triazolo[3,4-A][l,3]benzothiazoledicarbonitrile derivatives are used to prepare hexazocyclanes-fluorophores as active media for liquid and solid lasers, scintillators, and for transformation of short-wave radiation to long-wave radiation <2004RUP2238276>. 

Our library synthesis was carried out with a set of 27 tube-shaped solid phase synthesis support, called MicroTubes. These supports are prepared by radiation grafting of polystyrene ( — 350 pmol) onto polypropylene tubes, chemically functionalizing the polystyrene with aminomethyl groups to afford about 55 imol of amine per tube, inserting a reusable Rf ID tag into each tube, and heat-sealing the tube ends to prevent loss of the tag. The chemical conversion of all 36 aminomethyl tubes was carried out simultaneously using standard procedures with rink amide linker, each with —46 pmol of available amine per tube.1 2... 

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