Satoru Hosoda

Degree of branch inclusion into the lamellar crystal for various ethylene/α-olefin copolymers

Various copolymers of ethylene with α-olefins, i.e. propylene, but-1-ene, hex-1-ene, oct-1-ene, dodec-1-ene and 4-methylpent-1-ene, were degraded oxidatively with fuming nitric acid (FNA). For all copolymers, the fraction of residue after FNA treatment was in close agreement with the degree of crystallinity before treatment. The X-ray diffraction pattern of the treated sample did not show any amorphous peak. These results indicate that selective removal of the amorphous region occurs by FNA treatment. The 13 C nuclear magnetic resonance (n.m.r.) spectrum and size exclusion chromatogram of the degraded sample suggested that the main component of the residue was dicar☐ylic acid, with a molecular weight dependent on the lamellar crystal thickness. Inclusion of short-chain branches into the crystalline core was also proved directly via the 13 C n.m.r. spectrum. The probability of branch inclusion determined from the n.m.r. spectrum is in the order>methyl>ethyl>n-butyl=n-hexyl=n-decyl>isobutyl, which seems to depend on the bulkiness of the branch. The difference in the probabilities of branch inclusion between n-butyl and isobutyl could be explained from the viewpoint of the mobility of the branch when the methylene sequences containing the branches crystallize from the molten state.

Chemiluminescence imaging of polymer materials under thermal oxidation and stress

Abstract Chemiluminescence imaging was successfully carried out for some polymer materials under heating or mechanical stress using a two-dimensional photoelectron detector. Oxidative degradation could be visualized for the press-moulded sheets of Nylon 6 (Ny6) and polystyrene (PS), and for the multilayered sheet composed of polyethylene (PE) and styrene-butadiene triblock copolymer (SBS) by heating samples at 50–154†C in air. The chemiluminescence intensity varied over the surface of the sample specimen; the surface trimmed with a razor blade and the cracked portion exhibited especially strong luminescence for Ny6 and PS samples. The difference in the oxidation reaction rate between the two kinds of materials could be visualized clearly for the multilayered sheet of PE and SBS. Stress-induced luminescence was observed on drawing Ny6 at room temperature, and it was found that the luminescence was remarkably strong around the stress-concentrated part of the specimen.

Chemiluminescence of polyethylene induced by UV irradiation

SummaryThe chemiluminescence (CL) of polyethylene (PE) film induced by UV irradiation was investigated. CL parameter, I0, which indicates the oxidation rate under UV irradiation was obtained from a kinetic analysis. The I0 was found to be valuable to evaluate the durability of PE films.

Propylene polymerization using various metal-containing MCM-41 as cocatalyst

Polymerizations of propylene were conducted with rac -ethylene(bisindenyl)zirconium dichloride ( rac -Et(Ind) 2 ZrCl 2 ) with triisobutylaluminum (Al( i -C 4 H 9 ) 3 ) using various metal-containing MCM-41(Metal-MCM-41). The catalyst system gave selectively isotactic polypropylene. The order of the cocatalytic activity of Metal-MCM-41 (Si/Metal=ca. 13) was as follows: GaMCM-41>ZnMCM-41>AlMCM-41≫TiMCM-41. The linear relationship between the polymer yield and the number of strong Lewis acid sites was observed. This strongly suggests that not weak Lewis acid sites but strong Lewis acid sites generated on Metal-MCM-41 can activate the metallocene compound effectively, resulting in the formation of active sites for propylene polymerization.

34. Structure and Properties of Ethylene / α-Olefin Copolymers Polymerized with Homogeneous and Heterogeneous Catalysts

Abstract Structure and properties of various ethylene / α-olefin copolymers were comparatively investigated. Copolymers polymerized with a heterogeneous Ziegler-Natta catalyst showed a wide intermolecular structural distribution, contrary to a narrow distribution of the copolymers obtained with a homogeneous catalyst system. This structural distribution was found to be correspondingly reflected in the distribution on a crystalline level such as a lamella thickness distribution (LTD). Mechanical properties of the copolymers were strongly influenced by the structural distribution; i.e., the narrower the chemical composition distribution and LTD, the stronger the impact strength. This result could be explained from the viewpoints of tie molecular concentration and its orientational homogeniety with deformation.

Isospecific polymerization of propylene with Metal-MCM-41

Abstract Polymerizations of propylene were conducted using various Metal-MCM-41 prepared by the post-synthesis method. Ti-, Zr-, Hf-, Mn- and Zn-MCM-41 combined with alkylaluminiums were found to give isotactic polypropylenes with wide molecular mass distributions.

Propylene polymerization behavior of Ti-containing mesoporous silicas

Ti-containing mesoporous silicas (Ti-MCM-41, Ti-MCM-48 and Ti-SBA-15) were prepared by the post-synthesis with Ti(OC 4 H 9 ) 4 and their propylene polymerization behavior was investigated. It was found that these Ti-containing mesoporous silicas combined with Al( i -C 4 H 9 ) 3 provide the isotactic polypropylene. Polypropylenes outside and inside the mesopores of Ti-containing mesoporous silicas had different characteristics despite being polymerized concurrently. The crystallization of polypropylenes confined in the mesopores was considerably depressed due to the limited space.

Characterization of Polymer Interface by Micro Raman Spectroscopy

Micro Raman spectroscopy was applied to characterize the interface region of multi-layered film specimens in which ethylene-propylene random copolymer(EPR) was sandwiched with polyethylene(PE) or polypropylene(PP) sheets. Micro Raman line scan of the interface region for PE/EPR pair indicated that PE molecules migrated into the EPR phase and crystallized there, forming a mixed phase where the PE crystallites were embedded in EPR matrix. Apparent diffusion constant(D) evaluated from the thickening rate of the mixed phase strongly depended on the chemical composition of EPR, i.e., D increased with increasing the ethylene content of EPR. On the contrary, the mixed phase thickness of PP/EPR pair showed the opposite dependence on the composition of EPR.