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Preliminary study on application PE filler modified by radiation
Radiation Physics and Chemistry 57 (2000) 411±416
www.elsevier.com/locate/radphyschem
Preliminary study on application PE ®ller modi®ed by radiation I. Legocka a, b,*, Z. Zimek a, K. Mirkowski a, A. Nowicki a a
Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195, Warsaw, Poland b Industrial Chemistry Research Institute, Rydygiera 6, 01-763, Warsaw, Poland
Abstract Mineral ®ller magnesium oxide (MgO) has been modi®ed by a grafting process initiated by electron beam treatment. The methacrylic acid (MAA), methyl methacrylate (MM) and maleic anhydride (MA) were used as modifying monomers. The products of performed modi®cation has been investigated by FTIR, DSC and TG methods. Modi®ed ®llers have been used in compositions with polyethylene (LDPE). Structure of the samples has been investigated by the SEM method. Mechanical properties of selected samples have been studied and discussed. The optimal results depends on dose level which is speci®c for certain monomers, ratio and type of monomers used and for grafting process. This paper presents data released to in¯uence the type of monomer on properties of grafted ®ller. The obtained samples of ®lling polyethylene were characterized generally by better dispersibility and some mechanical properties. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Radiation grafting; Fillers; Magnesium oxide; Radiation modi®cation
1. Introduction Inorganic ®llers (their surface) are modi®ed by some methods: grafting (Fujiki et al., 1990; Tsubokawa et al., 1990), appreting, shealing, etc. to improve dispersibility and compatibility with polymer matrixes. Generally, graft of inorganic materials by chemical initiation is dicult, but ionizing radiation can make them active which leads to the grafting process (Golubiv et al., 1977; Korsak et al., 1978). Modi®cation of the ®llers has been developed using the graft method stimulated by radiation initiation in the recent years. The inorganic ®llers such as chalk, zinc oxide, magnesium oxide and talc are generally used in compositions with polyethylene and poly-
* Corresponding author. Fax: +48-22-633-82-95.
propylene. Radiation method had recently been used to modify ®ller surfaces by Guanglin et al. (1993) and Yuding et al. (1993). 2. Experimental Materials: magnesium oxide (MgO), methyl methacrylate (MM), methacrylic acid (MAA), maleic anhydride (MA), LDPE polyethylene (PE). 2.1. Modifying process of ®ller Monodispersity, dry powder of the magnesium oxide with monomers 10 and 15 wt% (MM and MMA), before irradiation treatment, had been preliminarily mixed and wetted for 24 h. The preparation of the sample in the case used for the modi®cation of the
0969-806X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 9 - 8 0 6 X ( 9 9 ) 0 0 4 4 8 - X
412
I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
Table 1 Investigated ®ller compositions and graft yield No.
Composition of ®ller
Dose (kGy)
Graft yielda (%)
1 2 3 4 5 6
MgO+15 MgO+15 MgO+15 MgO+15 MgO+15 MgO+15
20 30 20 30 20 30
8.7 9.5 11.6 12.3 12.8 11.4
a
wt% wt% wt% wt% wt% wt%
MA MA MAA MAA MM MM
After separating homopolymer and monomer (extracting with re¯uxing benzene, 30 min).
maleic anhydride (MA) had been done according to the following procedure: maleic anhydride was dissolved in acetone, and the ®ller was wetted by this solution for 24 h by prepared solution. The solvent was easily evaporated from the system before irradiation treatment. Irradiation was carried out at room temperature in air by electron beam in a LAE 13/9 type accelerator (electron energy 10 MeV, average beam power 9 kW) using doses of 20±30 kGy. The products were investigated using dierent measuring methods such as: FTIR, DSC, TG and electron scanning microscopy (SEM).
Fig. 1. FTIR transmittance spectra of MgO and grafted MgO (all spectra in KBr matrix).
I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
413
Fig. 2. SEM microphotographs of MgO particles modi®ed with monomers. Magni®cation 500 . (a) MgO-g-MA, (b) MgO-gMM, (c) MgO-g-MAA.
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I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
Table 2 Thermal stability of ®llers modi®ed by vinyl monomersa Weight decreasing at temperature range (%) Sample
308C±3008C
308C±4308C
308C±5008C
Tonset (8C)b
MgO+10% MM MgO+10% MM MgO+10% MA MgO+15% MA Mg)O+10% MAA MgO+15% MAA
4.52 4.88 4.66 4.58 4.92 4.70
20.52 20.99 21.24 20.74 23.52 22.35
22.59 23.02 23.82 22.10 25.21 29.3
457.25 455.02 457.46 459.18 442.21 444.32
a b
All samples after extracting of hompolymer and monomer with re¯uxing benzene, 30 min. Tonset, temperature of the beginning of rapid decomposition.
2.2. Filling of PE Filling of PE was performed using a twin-screw extruder. The samples contained 35 wt% and 50 wt% of the ®ller. The products were characterized by DSC, TG, SEM and mechanical methods. 3. Results and discussion Investigated ®ller compositions and graft yield are displayed in Table 1. Observed yield of reaction shows
that with higher dose the yield was increased, but not by much. FTIR spectra of modi®ed MgO with MA and MM show characteristic vibration peaks. It was found that increased band in the range 1700±1800 cmÿ1 is due to overlap of the band characteristic for anhydride and the band of MgO (sample MgO-g-MA). The sample of MgO-g-MM is characterized by the range 1700±1750 cmÿ1, which was increased due to the carbonyl group of methyl methacrylate. The bands within the range 2800±3000 cmÿ1 have been revealed as a result of C±H bond vibration. It suggested that grafting had been done (Fig. 1).
Fig. 3. The egzothermic peaks of modi®ed ®llers. Determined by Perkin-Elmer DSC7. (a) MgO-g-MA, (b) MgO-g-MM, (c) MgOg-MAA.
I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
415
Fig. 4. The melting endotherms of modi®ed with ®llers samples of PE. Determined by Perkin-Elmer DSC7. (a) PE+MgO-g-MA, (b) PE+MgO-g-MM, (c) PE+MgO-g-MAA, (d) PE alone.
products which is also dierent compared with initial properties of PE samples (Fig. 4). The most signi®cant disturbance of the melting endotherms is observed when MgO-g-MM is applied. The microscopic investigation performed with the SEM method application suggests uniform distribution of the modi®ed ®ller in polymer matrix. The phase separation has not been observed in the system (Fig. 5). That may be important for mechanical properties of the obtained composite. Table 3 contains the data regarding some mechan-
Microphotographs of particles of modi®ed MgO show growth of polymeric layers onto substrate. It seems that MgO modi®ed with MM has the largest layer (Fig. 2). Table 2 contains data regarding thermal stability of ®llers modi®ed by vinyl monomers. The character of DSC curves of grafted MgO (Fig. 3) can suggest possibilities to obtain polymer compositions reinforced by crosslinking ®llers. This eect may be observed, especially for MgO-g-MA and MgO-g-MAA. The thermal investigation of the ®lled PE samples (DSC curves) shows dierentiated crystalinity of the obtained
Table 3 Mechanical properties of ®lled polyethylene (PE, type FGNX23-D022)a Melt ¯ow index (MFI g/10 min) No. Sample
Filler (% of ®lling)
Eg (MPa)
dgf an (MPa) (kJ/m2)
ak (kJ/m2)
TUM 1908C/5kG 1908C/2.16 kG (8C)
1 2 3 4 5
MgO-g-MM 50 MgO-g-MM 50 MgO-g-MA 50 MgO-g-MAA 50 ±
240 237 228 205 185±190
6.42 6.44 6.42 6.28 5.42
No No No No
95 95 95 96 96
PE+(MgO+10% MM) PE+(MgO+15% MM) PE+(MgO+10% MA) PE+(MgO+10% MAA) PE FGNX23-D022
No No No No
cracks cracks cracks cracks ±
cracks cracks cracks cracks ±
2.72 3.02 2.25
± ±
1.98 2.16 1.90
± ±
a Eg, ¯exural modulus; dgf, ¯exural strength; an, impact strength; ak, notchet impact strength; TUM, temperature of the de¯ection by Martens.
416
I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
ical properties of polyethylene with modi®ed ®llers. The best results we can see for compositions with MgO-g-MM. 4. Conclusions
1. Yield of grafting monomers onto MgO is increased signi®cantly with dose at 20±30 kGy. 2. The highest thermal stability was obtained for PE ®lled with MgO-g-MA, but the highest mechanical properties were obtained for PE ®lled with MgO-gMM at a ratio of 50:50. 3. SEM microphotograph of composition PE+MgOg-MM shows that ®ller is well dispersed in the polymer matrix. 4. The works on radiative modi®cation of ®llers and its application will be continued.
References Fujiki, K., et al., 1990. Radical grafting from carbon black. Polym. J. 22, 661. Golubiv, V.N., et al., 1977. Mechanism of graft polymerization by radiation from gaseous phase on the mineral surfaces. Dokl. Akad. Nauk SSSR 198, 1085 (in Russian). Guanglin, H., et al., 1993. Study of radiation grafting of Al2O3. Radiat. Phys. Chem. 42, 61. Korsak, V.V., et al., 1978. Grafting vinyl pyridines by chemical-radiation methods on the surface of SiO2. Vysokmol. Soedin. A20, 1010 (in Russian). Tsubokawa, N., et al., 1990. Graft polymerization of vinyl monomers from inorganic ultra®ne particles initiated by azo groups introduced onto the surface. Polym. J. 22, 827. Yuding, F., et al., 1993. Surface modi®cation of MgO ®ller by radiation. Radiat. Phys. Chem. 42, 77.
Fig. 5. SEM microphotographs of the ®lled PE with MgO-gMM. Magni®cation 500 . (a) PE+MgO, (b) PE+MgO-gMM.
www.elsevier.com/locate/radphyschem
Preliminary study on application PE ®ller modi®ed by radiation I. Legocka a, b,*, Z. Zimek a, K. Mirkowski a, A. Nowicki a a
Institute of Nuclear Chemistry and Technology, Dorodna 16, 03-195, Warsaw, Poland b Industrial Chemistry Research Institute, Rydygiera 6, 01-763, Warsaw, Poland
Abstract Mineral ®ller magnesium oxide (MgO) has been modi®ed by a grafting process initiated by electron beam treatment. The methacrylic acid (MAA), methyl methacrylate (MM) and maleic anhydride (MA) were used as modifying monomers. The products of performed modi®cation has been investigated by FTIR, DSC and TG methods. Modi®ed ®llers have been used in compositions with polyethylene (LDPE). Structure of the samples has been investigated by the SEM method. Mechanical properties of selected samples have been studied and discussed. The optimal results depends on dose level which is speci®c for certain monomers, ratio and type of monomers used and for grafting process. This paper presents data released to in¯uence the type of monomer on properties of grafted ®ller. The obtained samples of ®lling polyethylene were characterized generally by better dispersibility and some mechanical properties. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Radiation grafting; Fillers; Magnesium oxide; Radiation modi®cation
1. Introduction Inorganic ®llers (their surface) are modi®ed by some methods: grafting (Fujiki et al., 1990; Tsubokawa et al., 1990), appreting, shealing, etc. to improve dispersibility and compatibility with polymer matrixes. Generally, graft of inorganic materials by chemical initiation is dicult, but ionizing radiation can make them active which leads to the grafting process (Golubiv et al., 1977; Korsak et al., 1978). Modi®cation of the ®llers has been developed using the graft method stimulated by radiation initiation in the recent years. The inorganic ®llers such as chalk, zinc oxide, magnesium oxide and talc are generally used in compositions with polyethylene and poly-
* Corresponding author. Fax: +48-22-633-82-95.
propylene. Radiation method had recently been used to modify ®ller surfaces by Guanglin et al. (1993) and Yuding et al. (1993). 2. Experimental Materials: magnesium oxide (MgO), methyl methacrylate (MM), methacrylic acid (MAA), maleic anhydride (MA), LDPE polyethylene (PE). 2.1. Modifying process of ®ller Monodispersity, dry powder of the magnesium oxide with monomers 10 and 15 wt% (MM and MMA), before irradiation treatment, had been preliminarily mixed and wetted for 24 h. The preparation of the sample in the case used for the modi®cation of the
0969-806X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 9 - 8 0 6 X ( 9 9 ) 0 0 4 4 8 - X
412
I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
Table 1 Investigated ®ller compositions and graft yield No.
Composition of ®ller
Dose (kGy)
Graft yielda (%)
1 2 3 4 5 6
MgO+15 MgO+15 MgO+15 MgO+15 MgO+15 MgO+15
20 30 20 30 20 30
8.7 9.5 11.6 12.3 12.8 11.4
a
wt% wt% wt% wt% wt% wt%
MA MA MAA MAA MM MM
After separating homopolymer and monomer (extracting with re¯uxing benzene, 30 min).
maleic anhydride (MA) had been done according to the following procedure: maleic anhydride was dissolved in acetone, and the ®ller was wetted by this solution for 24 h by prepared solution. The solvent was easily evaporated from the system before irradiation treatment. Irradiation was carried out at room temperature in air by electron beam in a LAE 13/9 type accelerator (electron energy 10 MeV, average beam power 9 kW) using doses of 20±30 kGy. The products were investigated using dierent measuring methods such as: FTIR, DSC, TG and electron scanning microscopy (SEM).
Fig. 1. FTIR transmittance spectra of MgO and grafted MgO (all spectra in KBr matrix).
I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
413
Fig. 2. SEM microphotographs of MgO particles modi®ed with monomers. Magni®cation 500 . (a) MgO-g-MA, (b) MgO-gMM, (c) MgO-g-MAA.
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I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
Table 2 Thermal stability of ®llers modi®ed by vinyl monomersa Weight decreasing at temperature range (%) Sample
308C±3008C
308C±4308C
308C±5008C
Tonset (8C)b
MgO+10% MM MgO+10% MM MgO+10% MA MgO+15% MA Mg)O+10% MAA MgO+15% MAA
4.52 4.88 4.66 4.58 4.92 4.70
20.52 20.99 21.24 20.74 23.52 22.35
22.59 23.02 23.82 22.10 25.21 29.3
457.25 455.02 457.46 459.18 442.21 444.32
a b
All samples after extracting of hompolymer and monomer with re¯uxing benzene, 30 min. Tonset, temperature of the beginning of rapid decomposition.
2.2. Filling of PE Filling of PE was performed using a twin-screw extruder. The samples contained 35 wt% and 50 wt% of the ®ller. The products were characterized by DSC, TG, SEM and mechanical methods. 3. Results and discussion Investigated ®ller compositions and graft yield are displayed in Table 1. Observed yield of reaction shows
that with higher dose the yield was increased, but not by much. FTIR spectra of modi®ed MgO with MA and MM show characteristic vibration peaks. It was found that increased band in the range 1700±1800 cmÿ1 is due to overlap of the band characteristic for anhydride and the band of MgO (sample MgO-g-MA). The sample of MgO-g-MM is characterized by the range 1700±1750 cmÿ1, which was increased due to the carbonyl group of methyl methacrylate. The bands within the range 2800±3000 cmÿ1 have been revealed as a result of C±H bond vibration. It suggested that grafting had been done (Fig. 1).
Fig. 3. The egzothermic peaks of modi®ed ®llers. Determined by Perkin-Elmer DSC7. (a) MgO-g-MA, (b) MgO-g-MM, (c) MgOg-MAA.
I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
415
Fig. 4. The melting endotherms of modi®ed with ®llers samples of PE. Determined by Perkin-Elmer DSC7. (a) PE+MgO-g-MA, (b) PE+MgO-g-MM, (c) PE+MgO-g-MAA, (d) PE alone.
products which is also dierent compared with initial properties of PE samples (Fig. 4). The most signi®cant disturbance of the melting endotherms is observed when MgO-g-MM is applied. The microscopic investigation performed with the SEM method application suggests uniform distribution of the modi®ed ®ller in polymer matrix. The phase separation has not been observed in the system (Fig. 5). That may be important for mechanical properties of the obtained composite. Table 3 contains the data regarding some mechan-
Microphotographs of particles of modi®ed MgO show growth of polymeric layers onto substrate. It seems that MgO modi®ed with MM has the largest layer (Fig. 2). Table 2 contains data regarding thermal stability of ®llers modi®ed by vinyl monomers. The character of DSC curves of grafted MgO (Fig. 3) can suggest possibilities to obtain polymer compositions reinforced by crosslinking ®llers. This eect may be observed, especially for MgO-g-MA and MgO-g-MAA. The thermal investigation of the ®lled PE samples (DSC curves) shows dierentiated crystalinity of the obtained
Table 3 Mechanical properties of ®lled polyethylene (PE, type FGNX23-D022)a Melt ¯ow index (MFI g/10 min) No. Sample
Filler (% of ®lling)
Eg (MPa)
dgf an (MPa) (kJ/m2)
ak (kJ/m2)
TUM 1908C/5kG 1908C/2.16 kG (8C)
1 2 3 4 5
MgO-g-MM 50 MgO-g-MM 50 MgO-g-MA 50 MgO-g-MAA 50 ±
240 237 228 205 185±190
6.42 6.44 6.42 6.28 5.42
No No No No
95 95 95 96 96
PE+(MgO+10% MM) PE+(MgO+15% MM) PE+(MgO+10% MA) PE+(MgO+10% MAA) PE FGNX23-D022
No No No No
cracks cracks cracks cracks ±
cracks cracks cracks cracks ±
2.72 3.02 2.25
± ±
1.98 2.16 1.90
± ±
a Eg, ¯exural modulus; dgf, ¯exural strength; an, impact strength; ak, notchet impact strength; TUM, temperature of the de¯ection by Martens.
416
I. Legocka et al. / Radiation Physics and Chemistry 57 (2000) 411±416
ical properties of polyethylene with modi®ed ®llers. The best results we can see for compositions with MgO-g-MM. 4. Conclusions
1. Yield of grafting monomers onto MgO is increased signi®cantly with dose at 20±30 kGy. 2. The highest thermal stability was obtained for PE ®lled with MgO-g-MA, but the highest mechanical properties were obtained for PE ®lled with MgO-gMM at a ratio of 50:50. 3. SEM microphotograph of composition PE+MgOg-MM shows that ®ller is well dispersed in the polymer matrix. 4. The works on radiative modi®cation of ®llers and its application will be continued.
References Fujiki, K., et al., 1990. Radical grafting from carbon black. Polym. J. 22, 661. Golubiv, V.N., et al., 1977. Mechanism of graft polymerization by radiation from gaseous phase on the mineral surfaces. Dokl. Akad. Nauk SSSR 198, 1085 (in Russian). Guanglin, H., et al., 1993. Study of radiation grafting of Al2O3. Radiat. Phys. Chem. 42, 61. Korsak, V.V., et al., 1978. Grafting vinyl pyridines by chemical-radiation methods on the surface of SiO2. Vysokmol. Soedin. A20, 1010 (in Russian). Tsubokawa, N., et al., 1990. Graft polymerization of vinyl monomers from inorganic ultra®ne particles initiated by azo groups introduced onto the surface. Polym. J. 22, 827. Yuding, F., et al., 1993. Surface modi®cation of MgO ®ller by radiation. Radiat. Phys. Chem. 42, 77.
Fig. 5. SEM microphotographs of the ®lled PE with MgO-gMM. Magni®cation 500 . (a) PE+MgO, (b) PE+MgO-gMM.