Yoshitaka Ogiwara

Free radical formation and degradation of cellulose by ionizing radiations

Abstract Free radicals produced during interaction of visible, ultraviolet and ionizing radiations with cellulose have been identified by reference to the available experimental ESR evidence and recent ESR-ENDOR spectroscopy. The subsequent chemical transformations of these radicals were deduced by reference to the products derived by radiation chemical studies of carbohydrate systems.

Preparation of Ultraviolet Stabilizing Polymers. I. Copolymerization of 2-Hydroxy-4-acryloyloxybenzophenone and Its Ultraviolet Stability

Abstract To obtain ultraviolet stabilizing polymers, 2-hydroxy-4-acryloyloxybenzophenone was prepared from 2,4-dihydroxybenzophenone and copolymerized with styrene. Copolymers containing three different amounts of ultraviolet absorber were prepared. These copolymers, unstabilized pure polystyrene and a series of stabilized polystyrene, were exposed to ultraviolet, and the ultraviolet stability of these polymers was compared by the relative amount of infrared absorption around 1700 cm−1 due to the carbonyl group. Ultraviolet stability of the copolymers is very similar to that of blend polymers and is higher than that of unstabilized pure polystyrene.

Swelling Degree of Cellulose Materials and Hydrolysis Rate with Cellulase

We investigated some relationships between the hydrolysis rate with cellulase and the swelling degree of the cellulose fibers of different samples. The water retention value (WRV) determined by the centrifugal method was used as a measure of the swelling degree. A linear relationship was observed between the hydrolysis rate and the WRV of the untreated pulps of different chemical composition and crystallinity. A similar linearity was observed also for pulps treated mechanically or chemically, but the slope of the regression line differed with the treating methods, and it decreased in proportion with the degree of degradation of the fiber structure.

Preparation of Polymeric Ultraviolet Absorbers and Their Effects on the Photodegradation of Polyethylene

Abstract Polymeric ultraviolet absorbers were prepared from 2-hydroxy-4-acryloyloxybenzophenone and 2-hydroxy-4-methacryloyloxybenzophenone and their inhibitive effect for photodegradation of polyethylene were examined by measuring mechanical strength, melt index, carbonyl group, and color difference. The polymeric ultraviolet absorbers were superior to the same type of ultraviolet absorber with low molecular weight in many properties, but inferior to Tinuvin, a commercial reagent, which has a different molecular structure. Therefore, within the ultraviolet absorbers examined, molecular structure seems to be a more important factor than molecular weight.

Benzophenone-sensitized photodegradation of polyethylene

Abstract The effects of benzophenone (BP) on the photodegradation of polyethylene were investigated by analyzing the ESR and infrared spectra of the irradiated samples. The unsensitized sample irradiated at −196°C with light of λ > 300 nm yielded a spectrum composed of 8-line (alkyl radical) and 5-line (allyl radical) components with splitting constants of 22 gauss and 12 gauss, respectively. With the BP-sensitized sample, the 8-line component decayed, emphasizing the 5-line component. The BP-sensitized samples exposed at room temperature to light of λ > 220 nm and λ > 300 nm exhibited a singlet with a line width of 14 gauss (polyenyl radical) and a 5-line spectrum with a splitting constant of 12 gauss, respectively. Infrared spectra of the irradiated samples showed that BP strongly accelerates the formation of double bonds. It is believed that BP acts in the photodegradation of polyethylene to enhance the formation of allyl and polyenyl radicals, which starts at the double bonds in the sample.

Comparative examination of sensitizers in photografting on polymer films

Abstract Photografting (λ > 300 nm) of methacrylic acid on low-density polyethylene film (thickness 30 μm) was carried out at 60°C for 60 min in water medium, and the activity of sensitizers towards the grafting was examined. Various sensitizers, involving hydrogen atom abstraction (aromatic ketones and quinones), radical generation, and energy transfer (aromatic hydrocarbons), were coated on the film sample beforehand. High percentages of grafting ( > 800%) were recorded for aromatic ketones (xanthone, thioxanthone and benzophenone), for quinones (2-chloroanthraquinone, 2-methylanthraquinone and 9,10-phenanthraquinone) and for radical generators (benzoin ethyl ether and phenyl disulfide). However, energy-transfer types (anthracene, phenanthrene and naphthalene) exhibited little effect on the grafting. Carbazoles, as well as the above sensitizers, were found to be considerably effective. Characteristics of each type of sensitizer are discussed in terms of the amount coated and the kinds of film (polypropylene and nylon 6) and monomer (acrylic acid and methyl methacrylate).

Study on surface appearance of polyolefin plates modified by photografting: Effect of polymerization conditions

Abstract Thermal and photo- grafting of vinyl monomers on polypropylene plates of 1 mm thickness were carried out in water using benzoyl peroxide and benzophenone respectively as initiators. The resulting grafted samples were subjected to electron microscopy in a morphological observation of their surfaces. The grafted samples prepared by thermal grafting revealed a flat surface irrespective of the type of monomer used. The appearance of the surface of the samples prepared by photografting may be classified roughly into two types, flat or grainy. The flat surfaces were provided by the hydrophobic monomers methyl methacrylate and styrene. The grainy type was obtained using the hydrophilic monomers acrylic acid, methacrylic acid and N-vinylpyrrolidone. Photografting of the hydrophilic monomers was characterized by the high susceptibility of the grafted chains to photodecomposition. It was supposed that the formation of a grainy surface is closely related to an abnormal polymerization in which grafted chains are more susceptible to photodecomposition.

Photopolymerization of acrylonitrile induced by aniline derivatives

Photopolymerization of acrylonitrile in the presence of aniline derivatives was investigated at 30°C in N,N-dimethylformamide and dimethylsulfoxide under irradiation with light of λ > 300 nm. The activity of aniline derivatives to initiate the polymerization was in the order N,N-dimethylaniline > N-methylaniline > aniline, the highest being indicated for tertiary amine. A higher activity was shown for aniline derivatives substituted with a higher alkyl group on the nitrogen atom. The apparent activation energy of 8–9 kcal mol−1 was recorded for primary and secondary amines, and 4–5 kcal mol−1 for tertiary amines. The rate of polymerization was found to be proportional to the 12 power of amine concentration and to the 32 power of monomer concentration. Measurements of absorption and ESR spectra were performed for photoirradiated N,N-dimethylformamide solutions of aniline derivatives, and of mixtures of aniline derivatives and acrylonitrile. Based on the results, the mechanisms of initiating photopolymerization due to aniline derivatives are discussed in terms of radical generation induced by the amine and acrylonitrile system.

Thermal oxidative degradation of polypropylene. Part X: Inhibition of the copper-catalysed thermal oxidative degradation of polypropylene by chelating dyes

Abstract Polypropylene is unstable to heat and light in the presence of a minute amount of heavy metals and their compounds, especially cobalt, manganese and copper and their compounds. Therefore the inhibition of the metal-catalysed thermal oxidative degradation is a serious problem whem polypropylene is used for plastics and fibers. In this study, four groups of chelating dyes, namely, benzimidazoles, benzoxazoles, benzthiazoles and diazo-compounds were prepared, and their effect on the catalysed degradation was examined by the conventional oxygen-uptake method. Among the heavy metals, copper was used as the catalyst for the degradation. The following chelating dyes were found to be extremely effective for the inhibition of the copper-catalysed thermal oxidative degradation of polypropylene: 2-(2-benzimidazolyl)-phenol, 3-(2-imidazolin-2-yl)-2-napthol, 4-diethylamino-2,2′-dioxy-5-methylazobenzene and 3-methyl-4-(2-oxy-5-methylphenylazo)-1-phenyl-5-pyrazolone.

Benzophenone-sensitized photo-degradation of polyolefins: Influence of benzophenone on model compounds

Abstract The influence of benzophenone (BP) on the photo-degradation of model compounds of polyethylene and polypropylene was examined by means of ESR spectra of the compounds irradiated at − 196°C with light of λ >300 nm. BP-sensitized n -hexane, 2,4-dimethylpentane and 1-octene yielded 8-line, 4-line and 6-line spectra with splitting constants of 22 gauss, 24 gauss and 20 gauss, respectively. The spectral intensities increased with the amount of BP, but decreased gradually above a certain concentration of BP. The spectra recorded for the three samples disappeared when large amounts of BP were present, being replaced by a singlet spectrum with a line width of 14 gauss. By studying UV spectra, the formation of polyene with a triene structure was observed when 1-octene was irradiated in the presence of BP. BP is believed to influence the photo-degradation of model compounds such that it participates in the formation of alkyl radicals, but promotes the formation of polyenyl radicals in the system containing a large amount of BP.