Docstoc

degrad of polystyrene4

Document Sample
degrad of polystyrene4 Powered By Docstoc
					                                  ‫:‪PHOTODEGRADATION OF POLYS TYRENE‬‬
                                 ‫‪EFFECT OF POLYMER S TRUCTURE ON THE‬‬
                                 ‫‪FORMATION OF DEGRADATION PRODUCTS‬‬

                                               ‫‪Ayako Torikai* and Hiroshi Shibata‬‬
                                                  ‫‪Department of Applied Chemistry‬‬
                                                   ‫‪Graduate School of Engineering‬‬
                                                         ‫‪Nagoya University‬‬
                                               ‫3068-464 ‪Furo-cho, Chikusa-ku, Nagoya‬‬
                                                               ‫‪Japan‬‬




                                                                                                      ‫ﺍﻟﺨﻼﺼــﺔ‬
                    ‫ﺗﻤﺖ دراﺳﺔ اﻟﺘﺪهﻮر اﻟﻀﻮﺋﻲ ﻟﻨﻮﻋﻴﻦ ﻣﻦ اﻟﺒﻮﻟﻲ ﺳﺘﺎﻳﺮﻳﻦ )‪ (atactic‬و )‪ (syndiotactic‬ﺏﻮﺳﺎﻃﺔ‬
                    ‫ﻗﻴﺎس اﻻﻣﺘﺼﺎص اﻟﺒﺼﺮي ، وﻣﻄﻴﺎﻓﻴﺔ ﻓﻮرﻳﻴﺮ دون اﻟﺤﻤﺮاء ، واﻟﺮﻥﻴﻦ اﻟﺪوراﻥﻲ اﻹﻟﻜﺘﺮوﻥﻲ . وﹸﺃﺟﺮﻳﺖ‬
                    ‫اﻹﺷﻌﺎﻋﺎت اﻟﻀﻮﺋﻴﺔ ﺏﺎﺳﺘﺨﺪام ﻣﺼﺒﺎح زﺋﺒﻘﻲ ﻣﺘﻮﺳﻂ اﻟﻀﻐﻂ ) أﺡﺎدي وﻣﺘﻌﺪد اﻷﻟﻮان ( ﻓﻲ ﻣﻄﻴﺎﻓﻴﺔ‬
                    ‫أوآﺎزاآﻲ اﻟﻜﺒﻴﺮة . وأﻇﻬﺮت اﻟﻨﺘﺎﺋﺞ ﺗَـ َـﻜﱡـ ﻞ اﻟﻤﻨﺘﺠﺎت اﻟﻤﺆآﺴﺠﺔ ﻓﻲ اﻟﺒﻮﻟﻲ ﺳﺘﺎﻳﺮﻳﻦ )‪ (atactic‬ﺥﻼل‬
                                                                      ‫ـﺸ ـ َ‬
                    ‫ﻓﺤﻮﺹﺎت اﻟﺘﺪهﻮر اﻟﻀﻮﺋﻲ ، ﻓﻲ ﺡﻴﻦ ﺗﺸﻜﻠﺖ اﻟﺮواﺏﻂ اﻟﻤﺰدوﺟﺔ اﻟﻤﺘﺮاﻓﻘﺔ ﻓﻲ اﻟﺒﻮﻟﻲ ﺳﺘﺎﻳﺮﻳﻦ‬
                    ‫)‪ . (syndiotactic‬وﻇﻬﺮت اﻟﺮواﺏﻂ اﻟﻤﺰدوﺟﺔ اﻟﻄﻮﻳﻠﺔ ﻓﻲ اﻟﺒﻮﻟ ﻲ ﺳﺘﺎﻳﺮﻳﻦ اﻟﻤﻌﺮض ﻟﻸﺷﻌﺔ اﻟﻀﻮﺋﻴﺔ .‬
                                                              ‫ً‬                  ‫ـﺸ ـ ِ‬                        ‫َﱠ‬
                    ‫وﻗﺪ ﺗﻤﺖ ﻣﻨﺎﻗﺸﺔ اﻻﺥﺘﻼف ﻓﻲ ﺗَـ َـﻜﱡـ ﻞ هﺬﻩ اﻟﻤﻨﺘﺠﺎت ﺏﻨﺎ ء ﻋﻠﻰ اﻟﺘﺮآﻴﺐ اﻟﺪاﺥﻠﻲ ﻟﻬﺬﻩ اﻟﺒﻮﻟﻴﻤﺮات . وﺗﻢ‬
                                                                                ‫ـ‬
                    ‫ﺗﻘﺪﻳﺮ اﻟﻄﻮل اﻟﻤﻮﺟﻲ اﻷوﻟﻲ ﻟﺘﺸﻜ ﱡـ ﻞ اﻟﻤﻨﺘﺠﺎت اﻟﻤﺆآﺴﺠﺔ ﻣﻦ ﺗﺠﺎرب اﻻﺷﻌﺎع أﺡﺎدﻳﺔ اﻟﻠﻮن ﻋﻨﺪ ﺡﻮاﻟﻲ‬
                                                                            ‫)٠٠٣( ﻥﺎﻥﻮﻣﺘﺮ ﻟﻜﻼ اﻟﻨﻮﻋﻴﻦ ﻣﻦ اﻟﺒﻮﻟﻴﻤﺮ .‬




‫:‪*Address for Correspondence‬‬
‫‪Daido Institute of Technology‬‬
‫‪Takiharu-cho, Minami-ku‬‬
‫‪Nagoy a 457-8530 Japan‬‬
‫‪e-mail: torikaia@msj.biglobe.ne.jp‬‬
‫.‪All correspondence should preferably be made by e-mail‬‬


‫2002 ‪June‬‬                                                           ‫.‪The Arabian Journal for Science and Engineering, Volume 27, Number 1C‬‬   ‫11‬
     A. Torikai and H. Shibata



                        ABSTRACT
                          Photodegradation of atactic and syndiotactic polystyrene has been investigated using
                        optical absorption and Fourier Trans form Infrared (FTIR) spectral analysis and
                        electron spin resonance (ESR) spectroscopic measurements. Photoirradiations were
                        carried out with radiation from a medium pressure mercury lamp (polychrom atic
                        radiation) and monochromatic radiation using the Okazaki Large Spectrograph (OLS).
                        Oxygenated products form ation was favored in the photodegradation of atactic
                        polystyrene, while conjugated doubl e bond formation in syndiotactic polystyrene is
                        superior to that in atactic polystyrene. Longer conjugated doubl e bonds were found in
                        photoirradiated syndiotactic polystyrene. The difference in the products formed was
                        discussed on the basis of the structures of both polymers. The threshold wavelength
                        for oxygenated products formation estimated from the monochrom atic radiation
                        experiments was found to be around 300 nm for both polymers.

                        Classification: Chemistry, Photodegradation, Polymer Structure.




12   The Arabian Journal for Science and Engineering, Volume 27, Number 1C.                                      June 2002
                                                                                                   A. Torikai and H. Shibata



PHOTODEGRADATION OF POLYS TYRENE: EFFECT OF POLYMER S TRUCTURE ON
           THE FORMATION OF DEGRAD ATION PRODUCTS


1. INTRODUCTION
  Generally, degradation of polymers is affect ed by various factors including the molecular structure of polymers. It has
been reported that syndiotactic polypropylene is more stable against thermo-oxidative degradation than the isotactic
polymer [1, 2]. Similar results were obtained for atactic and isotactic polypropylene, where at actic polypropylene is
more stable than the isotactic polymer. An explanation for this phenomenon is that isotactic polypropyl ene has a much
more favorabl e structure for the backbiting reaction, where a peroxy radical abstracts an adj acent tertiary hydrogen on
the same polymer chain, which leads to the degradation of polypropylene [1]. In thermo-oxidative degradation,
however, it seems ambiguous whether the stereoregularity is kept in its original form, because the temperature during
thermo-oxidation may be too high to keep it. As photodegradation take place at around ambient temperature, the
stereoregularity of polymer may be kept during the degradation reaction.
  Recently, syndiotactic polystyrene has been produced at a Japanes e Company (Idemitsu Petrochemicals Co., Ltd.).
As we were kindly supplied with this sample, we have planned to study the effect of stereoregularity on the
photodegradation of polystyrene.
  Polystyrene is a widely us ed plastic in various industrial fields. This polymer has an absorption maximum at
λ = 250 nm due to s0 to s1 transition of benzene ring [3]. Since this absorption band extends to the longer wavelengths to
around 300 nm, polystyrene can absorb the UV-B radiation in the sunlight and begin the degradation reaction.
   Aspects of the photodegradation of polystyrene such as photon absorbing species [4], effect of atmosphere [5],
reaction mechanisms including elementary processes [6], photosensitized degradation [7], effect of additives (e.g. flame
retardants) [8, 9], wavelength sensitivity [9], and so on have been studied by many authors.
  In spite of many studies on the photodegradation of polystyrene, there are few studies on the effect of stereoregularity
on this process.
  The present paper aims mainly to clarify the effect of stereoregularity on the photodegradation of polystyrene.


EXPERIMENTAL
  Atactic and syndiotactic polystyrene were supplied, as pellets, from Mitsubishi Monsanto Chemicals and Idemitsu
Petrochemicals Co., Ltd, respectively. Polymer pellets were hot-pressed at a pressure of 80 kg/cm2 and at 190°C for
atactic polystyrene and 300°C for syndiotactic polymer, and then cooled to ambient temperature. The thickness of films
used in this experiment was adjusted to around 0.09 mm for both samples.
   A Toshiba medium pressure mercury lamp (H400-P) was used as a polychrom atic radi ation source. Photon intensity
at sample position was measured using a YSI M ODEL 65A radiomet er. Irradiation temperature was around 40°C.
Irradi ations of monochromatic radiation were carried out using the Okazaki Large Spectrograph (OLS), which gives
monochromatic radiation of any desired wavelength between 250 and 1000 nm with high radiation intensity. The details
of this spectrograph and the irradiation procedure for the samples were reported previously [10]. Irradiations were
carried out at 23°C in air and the irradiation wavelengths were 275, 290, 305, 320, 350, and 380 nm. The photon
intensity at each wavelength was measured by a Rayon PFDM–2000LX Photon Density meter developed for the OLS.
The stability of the source was continuously monitored at two wavelengths during irradiations. Total photon flux at each
wavelength was adjusted to the same value. Immediately after irradiations, the samples were put into a black envelope,
then stored in a desiccator at ambient temperature.
  UV–Visible and Fourier Trans form Infrared (FTIR) spect ra of photoirradiated s amples were taken on a Jasco V-550
and a Jasco 5300 spect rophotometer, respectively, to analyze the structural change of the polymer. Thermal behavior of
atactic and syndiotactic PSt was analyzed by DSC measurement.

June 2002                                                    The Arabian Journal for Science and Engineering, Volume 27, Number 1C.   13
     A. Torikai and H. Shibata



       Electron spin resonance (ESR) spectra of photoirradiated samples were obtained using a JEOL–3BX ESR
     spectrometer at ambient temperature in air.


     RESULTS AND DISCUSSION
     Degradation Behavior of Atactic and Syndiotactic Polystyrene
       Polystyrene samples were irradiated with the radiation from a medium pressure mercury lamp. The optical absorption
     spectra of photoirradiated at actic and syndiotactic polystyrene are shown in Figures 1 and 2. In these cases, the
     difference spectra (irradiated–uni rradi ated) are given to show the newly produced species clearly.




                                 Figure 1. Difference UV–Visible spectra of photoirradiated atactic polystyrene.
                                 Photon energy, from the bottom to the top; 1200, 2700, 4050, and 6150 W h/m 2.


       On photoirradiation, the optical density at 280 nm increased with the irradiation time. At the same time, the
     absorption at longer wavelength increas es in its intensity. Small peaks having absorption maxima at longer wavelength
     are produced. The increase in the intensity at λmax = 280 nm is assigned to the formation of carbonyl groups by photo-
     oxidation. Small peaks at longer wavelengths are attributed to the formation of conjugat ed double bonds in the polymer
     backbone ( I ) [11].

                         ~CH2 –CH(Ph)–(CH= CH)n –CH2 ~                                                                   (I )

     where, Ph rep resents the phenyl group in polystyrene and n is the number of conjugated doubl e bonds. The absorption
     maximum of conjugated double bond (λ) is calculated from the following Equation (1).

                         λ = 280 + 30(n – 1).                                                                            (1)

14   The Arabian Journal for Science and Engineering, Volume 27, Number 1C.                                        June 2002
                                                                                                      A. Torikai and H. Shibata




                      Figure 2. Difference UV–Visible spectra of photoirradiated syndiotactic polystyrene.
                        Photon energy, from the bottom to the top; 1200, 2250, 4500, and 6750 W h/m 2.



  In the present experiment, the numbers of conjugated double bonds for photoirradiated atactic and syndiotactic
polystyrene were estimated to be n = 1 to 4 and n = 1 to 6, respectively. Comparing Figure 1 and Figure 2, it is clear that
the carbonyl formation is favored in atactic polystyrene, while the rate of conjugat ed double bond form ation seems faster
in syndiotactic polystyrene than in the atactic polymer.
  The elementary processes of photodegradation of PSt initiates from photon absorption by polystyrene and the
formation of polystyryl radical ( II ) [6].
                           •
                  ~ CH 2 − C(Ph) − CH 2 ~                                                                                        ( II )

  The polystyryl radical thus formed reacts with oxygen and produces polymer peroxy radical. This radical abstracts
hydrogen from the polymer backbone and produces hydroperoxide, which is the precursor of oxygenated products [6].
  Hydroperoxide and oxygenat ed products formation can be followed by FTIR spectra. FTIR spectra of photoirradiated
atactic and syndiotactic polystyrene are shown in Figures 3 and 4.
  The absorption bands at around 1700 cm–2 increase in their intensity with the increase of the irradiation time and have
been attributed to the carbonyl groups. The peak centered at 1740 cm–2 is assigned to a carbonyl (C = O) vibration. The
intensity of this band increas es with the irradiation time (repres ented by photon energy) for at actic and syndiotactic
polystyrene, as shown in Figure 5. The changes in the absorption band at 3450 cm–2 (ROOH) are also plotted against
photon energy in the same figure.

June 2002                                                       The Arabian Journal for Science and Engineering, Volume 27, Number 1C.    15
     A. Torikai and H. Shibata




             2.5000




                 ABS




              0.0000
                  2200.0                                1800.0            1600.0                   1400.0                1200.0
                                                                     Wavenumber

              0.4000




                  ABS




             –0.1000
                   2200.0                                1800.0            1600.0                   1400.0                   1200.0
                                                                      Wavenumber

                       Figure 3. FTIR spectra of photoirradiated atactic polystyrene (A) and their difference spectra (B).
                                   Photon energy, from the bottom to the top; 2700, 4050, and 6150 Wh/m 2.


16   The Arabian Journal for Science and Engineering, Volume 27, Number 1C.                                                      June 2002
                                                                                                         A. Torikai and H. Shibata




        2.5000




              ABS




            0.0000
                 2200.0                           1800.0           1600.0                      1400.0                 1200.0
                                                              Wavenumber

       0.4000




             ABS




      –0.1000
            2200.0                               1800.0            1600.0                     1400.0                 1200.0
                                                              Wavenumber

               Figure 4. FTIR spectra of photoirradiated syndiotactic polystyrene (A) and their difference spectra (B).
                             Photon energy, from the bottom to the top; 2250, 4500, and 6750 Wh/m 2.


June 2002                                                          The Arabian Journal for Science and Engineering, Volume 27, Number 1C.   17
     A. Torikai and H. Shibata




     Figure 5.Changes in the optical density at 1740 cm –2 and 3450 cm –2. □ atactic polystyrene at 1740 cm –2; ○ syndiotactic polystyrene at
                           1740 cm –2; ■ atactic polystyrene at 3450 cm –2; ● syndiotactic polystyrene at 3450 cm –2.


        The rate of carbonyl and hydroperoxide formation is faster in atactic polystyrene than in syndiotactic polymer,
     although there are small differences in the rate at initial stage of irradiation. The band near 1680 cm–2 can be assigned to
     the carbonyl group attached to the phenyl group (III), and also increases in its intensity with the irradiation time.
                            O
                          (– C – Ph –)                                                                                                  ( III )

       Since various types of carbonyl groups were form ed in the case of photo-degradation of polystyrene in the
     1640–1800 cm–2 region, we compared the carbonyl groups form ation in this region by calculating the area under the
     curve for at actic and syndiotactic polystyrene The results are shown in Figure 6.
       The rate of oxygenated product formation is also faster in atactic polystyrene than in the syndiotactic polymer.
       From the results obtained above, it was found that the rate of oxygenated products formation is faster in at actic
     polystyrene than in syndiotactic polymer, while conjugated double bond formation is favored in syndiotactic
     polystyrene.
       We have also examined the radical formation in photoirradiat ed polystyrene to compare thes e di fferences. The decay
     in radicals produced by photoirradiation is plotted against decay time in Figure 7.
        The difference in the decay rates for atactic and syndiotactic polystyrene seems to be very small. Radicals thus formed
     may be distributed to oxygenated compounds and conjugated double bond formation in the succeeding reaction. The
     ratio of distribution may depend on the polymer structure and/or their crystallinity, which will be discussed in the
     following paragraph.

18   The Arabian Journal for Science and Engineering, Volume 27, Number 1C.                                                        June 2002
                                                                                                           A. Torikai and H. Shibata




Figure 6. Various types of oxygenated products formation in photoirradiated atactic polystyrene (□) and syndiotactic polystyrene ( ○).
                                          The ordinate is represented in arbitrary units.




            Figure 7. Decay of radicals produced in photoirradiated atactic polystyrene (□) and syndiotactic polystyrene ( ○);
                                                         irradiation time, 4hr.


June 2002                                                            The Arabian Journal for Science and Engineering, Volume 27, Number 1C.   19
     A. Torikai and H. Shibata



     Effect of Polymer Structure on the Degradation
       Molecular structure of at actic and syndiotactic polystyrene are shown in Figure 8.




                                      Figure 8. Molecular structure of atactic and syndiotactic polystyrene.



        Similar to the explanation for stereoregular polypropylene [1], polystyryl radical produced from syndiotactic
     polystyrene has an unfavorable structure for autooxidation via a backbiting mechanism, where peroxy radi cals abstract
     adjacent tertiary hydrogens on the same polymer chain, producing hydroperoxide which is the precursor of oxygenated
     products. On the other hand, atactic polystyrene has a random structure regarding the conform ation of H-atoms, so that
     it partly has a favorable structure for a backbiting reaction on the same polymer chain. This seems to be one reason for
     the predominant form ation of oxygenat ed products in atactic polystyrene.

       An alternative explanation for the di fference in the oxygenated product form ation may be possible in terms of the
     crystallinity of the polymers. To clari fy this problem, we have carried out DSC measurem ents on both polymers. The
     results were shown in Figure 9.

       Atactic polystyrene has one peak at T g = 85.03°C, which shows that this polymer has an amorphous structure, whereas
     syndiotactic polystyrene has three peaks which correspond to T g , Tc, and Tm (glass transition temperature, crystallization
     temperature, and m elting temperature, respectively). Generally, oxygen penetration to an amorphous polymer is faster
     than that to a crystalline polymer. In an amorphous polymer, polystyryl radi cals produced by photon absorption reacts
     with oxygen and give peroxy radicals which are the precursors of oxygenated products. In the case of crystalline
     polymers, the permeability of oxygen to the crystalline region is very small, so the radicals produced in this region are
     utilized for the formation of conjugated double bonds and/or recombination reactions. Similar observations on
     polyethylenes di ffering in their density have been obtained in our previous work [11]. The rate of oxygenat ed products
     formation is faster in linear low density polyethylene than in high density polyethylene, whereas conjugat ed double bond
     formation is favored in high density polyethylene. Medium density polymer gave intermediate values for the formation
     of both products.

       As shown in Figure 5, the oxygenated product formation of atactic and syndiotactic polystyrene did not show any
     difference up to a photon energy of 4000 Wh/m2 . This fact seems to show that at an initial stage, oxygen attack on
     syndiotactic polystyrene occurs on the molecule part of the polymer. At longer irradiation times, the di fference in
     crystallinity may have an effect on the formation of oxygenated products. ESR spectra of photoirradiated at actic and
     syndiotactic polystyrene have been m easured to clari fy the above explanation. Decay of radicals in atactic and
     syndiotactic polystyrene has already been shown in Figure 7.

20   The Arabian Journal for Science and Engineering, Volume 27, Number 1C.                                             June 2002
                                                                                                        A. Torikai and H. Shibata




             Figure 9. DSC analysis of unirradiated polystyrene. (A) atactic polystyrene, (B) syndiotactic polystyrene.



   When polystyrene is photoirradiated in vacuum, polystyryl radicals are produced at an initial stage of degradation.
These radicals convert to peroxy radicals in air and polyenyl radicals having various lengths of conjugated double bonds
in vacuum, as we have reported previously [6]. In the pres ent study, measurement was carried out in air and at ambient
temperature; the observed radicals may consist of polystyryl, peroxy, and polyenyl radicals [6]. In the initial stage, the
decay rate of radicals is faster in the syndiotactic polymer than in atactic polystyrene. This fast decay may be partly
attributed to the recombination reaction of radicals produced adj acent to each other in the crystalline region. For longer
times, decay behavior in both polymers did not di ffer so much. This means that radical formation and thei r decay
behavior are not so di fferent in the two polystyrenes except at the initial stage. From the above observations, it may be
concluded that the main reaction of radicals in the crystalline region is form ation of conjugated double bonds, while in
the amorphous and molecule regions, this reaction is attributed to oxygenat ed products formation, as in the cas e of
photoirradiated polyethylene [11].

June 2002                                                         The Arabian Journal for Science and Engineering, Volume 27, Number 1C.   21
     A. Torikai and H. Shibata



     Wavelength Sensitivity on Oxygenated Products Formation
       Polystyrene has photon absorbing species in its molecular structure; it absorbs mainly the UV-B sunlight and begins to
     degrade via oxygenated product formation. Action spectra which repres ent the efficiency of light-induced degradation of
     polymeric materials express ed as a function of wavelength of incident radiation give crucial information to clari fy the
     wavelength which caus es damage to the materials.
       We have m easured the action spectra of atactic and syndiotactic polystyrene using the OLS as a monochromatic
     radiation source. Changes in the optical density at 280 nm in UV-spectra of photoirradiated polystyrene are selected as a
     measure of oxygenated products formation. The results are shown in Figure 10.
       Oxygenated product formation was obs erved on irradiation with radiation of shorter wavel ength than 300 nm for both
     polystyrenes under our experimental conditions. Yields of oxygenated product are higher in atactic polystyrene than that
     in syndiotactic polymer, as found in the case of polychrom atic radiation. Oxygenat ed products formation was also
     monitored by the increase in the optical density at 1740 cm–2 in FTIR measurements. The results are shown in
     Figure 11.
        Similar results on oxygenat ed products formation and threshold wavelength for the product formation were obtained
     from FTIR measurements.
       It was found that photodegradation of atactic and syndiotactic polystyrene took place on irradiation with radiation of
     shorter wavel ength than 300 nm.




                             Figure 10. Changes in the optical density at 280nm at various irradiation wavelengths.
                        (□) atactic polystyrene; ( ○) syndiotactic polystyrene. Total photon flux, 8.3 × 1019 photons/cm 2.


22   The Arabian Journal for Science and Engineering, Volume 27, Number 1C.                                                   June 2002
                                                                                                                               A. Torikai and H. Shibata




                        Figure 11. Changes in the optical density at 1740 cm –2 at various irradiation wavelengths.
                     (□) atactic polystyrene; ( ○) syndiotactic polystyrene. Total photon flux, 8.3 × 1019 photons/cm 2.




ACKNOWLEDGEMENTS
  The authors gratefully acknowledge Prof. Masakatsu Watanabe, Mr. Sho-ichi Higashi, and Ms. Makiko Ito of the
National Institute of Basic Biology for their help in carrying out the irradiations. This study was carri ed out under the
NIBB Cooperative Research Program (99–520). The authors also express their appreciation to Dr. Nobuhide Ishihara of
Idemitsu Petrochemicals Co., Ltd., who provided syndiotactic polystyrene.

REFERENCES
[1]   H. Mori, T. Hatanaka, and M. Terano, “ Thermal Stability of Syndiotactic Polystyrene”, Macromol. Rapid Commun., 18 (1997),
      p. 157
[2]   M. Kato and Z.Osawa, Polymer Degradation and Stability, 65 (1999), p. 457.
[3]   W. Schnabel, Polymer Degradation. New York: Macmillan, 1981, p. 98.
[4]   J.F. Rabek, Polymer Photodegradation. New York: Chapman & Hall, 1985, p. 196.
[5]   A. T o ri k ai, “Pho to d eg rad ati on o f Pol ys ty ren e”, i n Han db oo k of P ol ymer S ci en ce a nd Techn olo g y vol. 2. ed. N. P. Ch eremi ns in o ff.
      New York: Marcel Dekker, 1989, pp. 616– 617.
[6]   A. Torikai, T. Takeuchi, and K. Fueki, “ Photodegradation of Polystyrene and P olystyrene Containing Benzophenone”, Polymer
      Photochemistry, 3 (1983), p. 307.
[7]   Reference [5], pp. 616– 617.
[8]   A. Torikai, H. Kato, K. Fueki., Y. Suzuki, F. Okisaki, and M. Nagata, “ Photodegradation of P olymer Materials Containing
      Flame-Cut Agents”, Journal of Applied Polymer Science, 58 (1995), p. 685.

June 2002                                                                         The Arabian Journal for Science and Engineering, Volume 27, Number 1C.                23
     A. Torikai and H. Shibata



     [9]   A. Torikai, T. Kobatake, F. Okisaki, and H. Shuyama, “ Photodegradation of P olystyrene Containing Flame-Retardant:
           Wavelength Sensitivity and Efficiency of Degradation”, Polymer Degradation and Stability, 50(1995), p. 261.
     [10] A. Torikai, “ Wavelength Sensitivity of P hotodegradation of P olymers”, in Handbook of Polymer Degradation, 2nd edn.
          ed. S.H. Hamid. New York: Marcel Dekker, 2000, pp. 575–576.
     [11] G. Geetha, A. Torikai, S. Nagaya, and K. Fueki, “ Photo-oxidative Degradation of Polyethylene: Effect of the P olymer
          Characteristics on the Chemical and Mechanical P roperties, P art 1 Quenched Polyethylene” Polymer Degradation and Stability,
          19 (1987), p. 279.

     Paper Received 3 February 2002; Accepted 23 October 2002.




24   The Arabian Journal for Science and Engineering, Volume 27, Number 1C.                                                  June 2002

				
DOCUMENT INFO
Categories:
Tags:
Stats:
views:17
posted:2/5/2010
language:English
pages:14