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Polyolefin Particles (polyolefin + particle)
Selected AbstractsTransport and Reaction Characteristics of Reconstructed Polyolefin ParticlesMACROMOLECULAR REACTION ENGINEERING, Issue 6 2008Libor Seda Abstract The 3D spatial structure of porous polyethylene particles was reconstructed from their X-ray micro-tomography images. Several polyolefin particles with an artificial granular structure were generated. Transport in reconstructed particles was calculated for the case of a monomer diffusing through both the pores and the polymer. The calculated degassing characteristics of reconstructed polyolefin particles can be compared to experiments. Monomer mass transport limitations are important not only in the early stage of particle growth, but also in fully-developed polyolefin particles. The problems and limitations of the developed method are discussed. The method developed allows prediction of the effect of particle structure on mass transport limitations for real particle structures. [source] Functionalization of LDPE by Melt Grafting with Glycidyl Methacrylate and Reactive Blending with Polyamide-6MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2003Qian Wei Abstract Low-density polyethylene (LDPE) was functionalized by melt radical grafting with glycidyl methacrylate (GMA) and employed for reactive blending with polyamide-6 (PA6). The effect of the reaction procedure on the grafting degree of LDPE- g -GMA samples (0.5,12.5 wt.-% GMA) was analyzed as a function of the concentration of GMA monomer, radical initiator (BTP), and addition of styrene as co-monomer. Optimized grafting conditions were obtained when the amount of the monomer is below 10 wt.-% and that of peroxide in the range 0.2,0.4 wt.-%. Binary blends of PA6 with LDPE- g -GMA (3.5 wt.-% GMA) and with LDPE at various compositions (80/20, 67/33, 50/50 wt.-%) were prepared in an internal mixer and their properties were evaluated by torque, SEM and DSC analyses. Morphological examination by SEM showed a large improvement of phase dispersion and interfacial adhesion in PA6/LDPE- g -GMA blends as compared with PA6/LDPE blends. The average diameter of dispersed polyolefin particles was about 0.4 ,m for LDPE- g -GMA contents <,50 wt.-%. A marked increase of melt viscosity was observed for the compatibilized blends depending on the concentration of grafted polyolefin, and it was accounted for by the reaction between the epoxy groups of GMA and the carboxyl/amine end-groups of PA6. The variation of torque was thus related to the molar ratio of reactive group concentration. The analysis of crystallization and melting behavior pointed out marked differences in the phase structure of the blends due to the presence of the functionalized polyolefin. Finally, the in situ formation of a graft copolymer between LDPE- g -GMA and PA6 was investigated by means of a selective dissolution method (Molau test) and by FT-IR and DSC analyses. SEM micrograph of fracture surface of PA6/LDPE- g -GMA 50/50 blend. [source] Transport and Reaction Characteristics of Reconstructed Polyolefin ParticlesMACROMOLECULAR REACTION ENGINEERING, Issue 6 2008Libor Seda Abstract The 3D spatial structure of porous polyethylene particles was reconstructed from their X-ray micro-tomography images. Several polyolefin particles with an artificial granular structure were generated. Transport in reconstructed particles was calculated for the case of a monomer diffusing through both the pores and the polymer. The calculated degassing characteristics of reconstructed polyolefin particles can be compared to experiments. Monomer mass transport limitations are important not only in the early stage of particle growth, but also in fully-developed polyolefin particles. The problems and limitations of the developed method are discussed. The method developed allows prediction of the effect of particle structure on mass transport limitations for real particle structures. [source] Estimation of Morphology Characteristics of Porous Poly(propylene) Particles from Degassing MeasurementsMACROMOLECULAR REACTION ENGINEERING, Issue 2 2008Marek Bobak Abstract The transport of reaction species in polyolefin particles affects both the polymerization and the degassing of the powder in the down-stream processing. The morphology of particles , that is, the distribution of polymer and pore phases , predetermines their degassing behavior. We utilize gravimetric measurements to obtain the dynamics of degassing and to determine morphology characteristics of porous poly(propylene) particles. We found that Fick's diffusion model is not generally capable of fitting the shape of degassing curves of porous particles. Therefore we propose a particle model including two sizes of compact polymer granules and demonstrate that the degassing can be described by this model and that the model is capable of estimating fractions of large and small compact zones and the size of large compact zones. [source] | ||||||||||