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Radiation crosslinking of polyamide 610
Radiation Physics and Chemistry 63 (2002) 493–496
Radiation crosslinking of polyamide 610 W. Fenga,*, F.M. Hub, L.H. Yuana, Y. Zhoua, Y.Y. Zhoua a
Faculty of Chemistry, Key Laboratory for Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, Sichuan, People’s Republic of China b Chenguang Research Institute of Chemical Industry, Chengdu 610041, Sichuan, People’s Republic of China
Abstract In the present paper the gel formation of polyamide 610 by g-ray irradiation in the presence of polyfunctional monomer and g-crystal nucleating agent under vacuum or air atmosphere had been studied. It was found that the gel formation was dependent on the content of polyfunctional monomer and nucleating agent. However, there was very little difference between gel contents irradiated under vacuum and air atmosphere. The results showed that the crosslinking by g-irradiation enhanced the mechanical properties of PA610 especially at high temperature in the presence of polyfunctional monomer and g-crystal nucleating agent. The mechanism of radiation crosslinking and scission was discussed according to the composition and quantity of gas released from three kinds of PA during irradiation. r 2002 Published by Elsevier Science Ltd. Keywords: Polyamide 610; Irradiation; Crosslinking
1. Introduction
2. Experimental
Polyamide resins are in the category of engineering plastics since they have excellent physico-mechanical properties. Further enhancing the physico-mechanical properties especially the heat-resistance by means of radiation crosslinking is still interesting to many radiation chemists (Zhang et al., 1984; Li et al., 1996a,b; Ueno, 1990). The crosslinking reaction of polyamide is often simultaneous with the scission reaction during irradiation. The relationship between crosslinking and scission for polyamides is dependent mainly on the length of methylene group chain in the polyamide macromolecules and the condition of crystallinity (Deev et al., 1980). In this paper the radiation crosslinking of polyamide 610 in the presence of crosslinker, g-crystal nucleating agent and filler have been studied. The possible mechanism of crosslinking and scission was discussed.
2.1. Material
*Corresponding author. Tel.: +86-28-541-0252. E-mail address: [email protected] (W. Feng).
PA610 was purchased from Helongjiang Institute of chemical Industry; triallyl isocyanate (TAIC) was imported from Russia; potassium iodide (KI), iodine (I2 ) and m-cresol were obtained from Shanghai Chemical Reagent Station. Talcum powder was in commercial grade. All materials were used without further handling.
2.2. Sample preparation PA610 samples for radiation were prepared by blending the different additives in a twin-screw extruder. The samples for tensile strength test were prepared in the injection machine (made in Germany ARURG). The granular of PA were charged into the specially made ampoules. After being subjected to evacuation of the ampoules for 24 h, the samples were sealed in ampoules followed by irradiating with 60Co g-ray at various irradiation doses.
0969-806X/02/$ - see front matter r 2002 Published by Elsevier Science Ltd. PII: S 0 9 6 9 - 8 0 6 X ( 0 1 ) 0 0 6 3 5 - 1
W. Feng et al. / Radiation Physics and Chemistry 63 (2002) 493–496
494
2.3. The measurement of gel content 80
60
Gel Content/%
0.3 g of irradiated samples of PA610 at various dose were accurately weighed and put into the Soxhlet extractor. After extracting with m-cresol for 48 h and with methanol for 24 h, the residue was dried in the vacuum oven till the constant weight was obtained, based on which the gel content was calculated.
40
20
2.4. The measurement of properties 0
The size of dumbbell sample was 60 10 3 2 mm. The tensile strength and elongation were determined by using WD-5 Electron Universal Testing Equipment. The tensile strength at 2201C was measured by the machine equipped with a heat oven designed by us. The total quantity and composition of gas released from the PA samples during irradiation were measured by gas chromatography (PERKAN-ELMER SIGMA15).
0
75
150
225
300
375
450
Dose/kGy
Fig. 2. The effect of filler content on gel formation of PA610 during irradiation in vacuum (TAIC: 3 phr) talcum: (’) 25 phr; () 8 phr; (m) 4 phr (.) 2 phr; (E) 0 phr.
80
3. Results and discussion 3.1. The effects of additives and irradiation atmosphere on PA610
80
40
20
0 0
75
150
225
300
375
450
Dose/kGy
Fig. 3. The effect of filler content on gel formation of PA610 during irradiation in air (TAIC: 3 phr) talcum: (’) 25 phr; () 8 phr; (m) 4 phr; (.) 2 phr; (E) 0 phr.
80
60
Gel Content/%
The effects of various additives of TAIC, filler of talcum powder and g-crystal nucleating agents of KI and I2 (Deev et al., 1980) on the formation of gel of PA610 during irradiation are shown in Figs. 1–4. It can be seen from the Fig. 1 that there was almost no formation of gel in the absence of TAIC, indicating that the crosslinking and scission occurred simultaneously during irradiation of PA610. While the addition of 5 phr TAIC led to a marked increase of the gel content up to about 75%, which demonstrated that the crosslinking predominated over the scission reaction. On comparing PA610-TAIC it can be clearly seen that the overall
Gel Content/%
60
40
20
Gel Content/%
60
0 40
0
75
150
225
300
375
450
Dose/kGy
Fig. 4. The effect of crystal nucleating agent on gel formation of PA610 during irradiation in air (TAIC: 3 phr) KI+I2: () 0.06 wt%+0.06%; (’) 0 wt%.
20
0 0
75
150
225
300
375
450
Dose/kGy
Fig. 1. The effect of polyfunctional monomer on gel formation of PA610 during irradiation in air TAIC: (’) 5 phr; () 3 phr; (m) 0 phr.
tendency in density of the network is in the order of PA610-5 phrTAIC>PA610–3 phrTAIC>PA610. Thus, TAIC is very effective here as a crosslinking additive for PA 610 under irradiation.
W. Feng et al. / Radiation Physics and Chemistry 63 (2002) 493–496
3.2. The mechanical properties of radiation crosslinked PA610 In Figs. 5 and 6 are given the influence of both polyfunctional monomer and fillers on the mechanical properties of PA610 during irradiation in air. For PA610 with TAIC and filler the tensile strength grew and the elongation at break decreased with increasing the irradiation dose. In contrast, the tensile strength and the elongation of PA610 without TAIC and talcum fell, reflecting the degradation of PA610 during irradiation. These results indicated that the presence of talcum contributed to the formation of gel and density of network of PA610-TAIC. The tensile strength of irradiated PA610 at 2201C is shown in Fig. 7. Obviously, the irradiated PA610 still had certain tensile strength at this high temperature. The tensile strength increased with the increasing of gel content and then tended to be 130
Tensile Strength/MPa
120
250
Elongation/%
200
150
100
50
0 0
75
150
225
300
375
450
Dose/kGy
Fig. 6. The effect of filler content on the elongation of PA610 during irradiation in air talcum+TAIC: (’) 0 phr X talcum+3 phrTAIC: X: (E) 8 phr; (.) 4 phr; (m) 2 phr; () 0 phr. 10
8
Tensile Strength/MPa
It is noteworthy that in the presence of both talcum and TAIC the gel content rose faster with the increasing of content of talcum powder than that in the presence of TAIC as shown in Figs. 2 and 3. This implies that the gel formation can also be accelerated both in vacuum and air with talcum as an additive. In this case the residual filler of talcum was not found from the crosslinked PA610 upon extraction. It may suggest that during irradiation of PA610 the link was formed between talcum and macromolecule of PA610. Besides, there is very little difference in the formation of gel for PA610 in the atmosphere of air and vacuum. The minor influence of air atmosphere on the process of gel formation may be accounted for by the fact that PA610 was in granular state and the diffusion of oxygen to the inside of granular was very difficult. In the meanwhile KI+I2 was found to be of benefit to gel formation during irradiation of PA610 as shown in Fig. 4.The result is similar to that reported by Deev (Deev et al., 1980)
495
6
4
2
0 0
10
20
30
40
50
60
Dose/kGy
Fig. 7. The effect of filler content on tensile strength at 2201C of PA610 (3 phr TAIC) at different dose in air X talcum (’) 8 phr; () 4 phr; (m) 2 phr; (.) 0 phr.
stationary. The tensile strength for irradiated PA6103 phrTAIC-8 phr talcum at 2201C was raised to 8 MPa. In contrast, the unirradiated PA610 already melted at this temperature. Thus the PA 610 prepared here under g-irradiation in the presence of TAIC or talcum via crosslinking possessed the advantage in heat-resistance over the unirradiated one at higher temperature.
110
3.3. Gases released from pure PA610 during irradiation 100
90
0
75
150
225
300
375
450
Dose/kGy
Fig. 5. The effect of filler content on the tensile strength of PA610 during irradiation in air talcum+TAIC: (’) 0 phr X talcum+3 phr TAIC: X: (E) 8 phr; (.) 4 phr; (m) 2 phr; () 0 phr.
According to the structure of aliphatic polyamide the macromolecule consisted of different length of methylene group incorporated with amide group. However, the similar backbone as polyethylene did not provide the similar radiation-initiated reaction as observed here in the scission reaction due to the weaker cyanic link in the amide group. It means that the crosslinking and scission were concomitant during irradiation of PA610. Meanwhile, gases were released accompanying the process of crosslinking and scission of PA610 (Deev et al., 1980).
W. Feng et al. / Radiation Physics and Chemistry 63 (2002) 493–496
496
Table 1 Released gases from polyamides during irradiation Gas
Radiation chemical yield (molecule/100 eV)
H2 CO CH3CHO Total
PA6
PA610
PA1010
0.098 0.0013 Trace 0.0994
0.115 0.035 Trace 0.151
0.123 0.011 Trace 0.134
d
d
2CH2 2 C O þ N H2CH2 2CH2 2H2 -2CH2 2CHO þ NH2 CH2 2CH2 2 2CH2 2CH2 2CH2 2CHO r
d
d
2 2CH2 2 C H2 þ C H2 2CHO d
2 C H2 2CHO þ H2 -2CH3 2CHO:
Gas chromatographic analysis demonstrated that the gases were mainly composed of H2, CO and trace of acetaldehyde. The yield of gases or G value of these gases was dependent on the polyamide or the length of the chain of methylene group in the polyamide macromolecule. The results of analysis are summarized in Table 1. Obviously, hydrogen gas accounted for the majority among the three components released and its amount increased with increment of length of the chain of methylene group. Based on the above results, a similar mechanism (Deev et al., 1980) of radiation crosslinking and scission of PA610 during irradiation was proposed as follows: 2CH2 CONH2CH2 CH2 2 d
r
d
2 2CH2 2CONH2 C H2CH2 2 þ H
4. Conclusion 1. The crosslinking and scission occurred simultaneously during irradiation of PA 610. The presence of TAIC, filler of talcum powder and g-crystal nucleating agents of KI and I2 was beneficial to radiation crosslinking of PA 610 2. PA 610 in the presence of TAIC or talcum by girradiation crosslinking possessed the advantage in heat-resistance over the unirradiated one, especially at higher temperature (2201C), the tensile strength was almost retained for irradiated PA 610. 3. The mechanism of crosslinking and scission during irradiation of PA 610 was discussed based on the gas released.
d
2CH2 CONH2CH2 CH2 2 þ H d
-2CH2 2CONH2 C H2CH2 2 þ H2 d
22CH2 CONH2 C H2 CH2 2 -2CH2 2CONH2CH2CH2 2CH2 2CONH2CH2CH2 2 2CH2 2CONH2CH2 CH2 2 d
r
d
2 2CH2 2 C O þ N H2CH2 2CH2 2 d
d
2CH2 2CH2 2 C O-2CH2 2 C H2 þ CO d
22CH2 2 C H2 þ H2 -22CH2 2CH3
References Deev, U.S., Subbotin, U.S., Riabov, E.A., 1980. Radiationchemical modification of polyamide. Plastmasse 4, 52. Li, B.Z., Zhang, L.H., Yu, J.Y., 19963a. g-radiation damage to crystalline polyamide 1010 containing heterogeneous. J. Radiat. Res. Radiat. Proc. 14, 4. Li, B.Z., Zhang, L.H., Yu, J.Y., 1996b. Post radiation effects on polyamide 1010. J. Radiat. Res. Radiat. Proc. 14, 153. Ueno, K., 1990. Section 2.3. CrosslinkingFthe radiation crosslinking process and new products. Radiat. Phys. Chem. 35, 126. Zhang, L.H., Li, S.Z., He, Z.D., Su, W., Zhang, Z.C., 1984. Radiation-induced crosslinking of polyamide 1010. J. Radiat. Res. Radiat. Proc. 3, 32.
Radiation crosslinking of polyamide 610 W. Fenga,*, F.M. Hub, L.H. Yuana, Y. Zhoua, Y.Y. Zhoua a
Faculty of Chemistry, Key Laboratory for Radiation Physics and Technology of Ministry of Education, Institute of Nuclear Science and Technology, Sichuan University, Chengdu 610064, Sichuan, People’s Republic of China b Chenguang Research Institute of Chemical Industry, Chengdu 610041, Sichuan, People’s Republic of China
Abstract In the present paper the gel formation of polyamide 610 by g-ray irradiation in the presence of polyfunctional monomer and g-crystal nucleating agent under vacuum or air atmosphere had been studied. It was found that the gel formation was dependent on the content of polyfunctional monomer and nucleating agent. However, there was very little difference between gel contents irradiated under vacuum and air atmosphere. The results showed that the crosslinking by g-irradiation enhanced the mechanical properties of PA610 especially at high temperature in the presence of polyfunctional monomer and g-crystal nucleating agent. The mechanism of radiation crosslinking and scission was discussed according to the composition and quantity of gas released from three kinds of PA during irradiation. r 2002 Published by Elsevier Science Ltd. Keywords: Polyamide 610; Irradiation; Crosslinking
1. Introduction
2. Experimental
Polyamide resins are in the category of engineering plastics since they have excellent physico-mechanical properties. Further enhancing the physico-mechanical properties especially the heat-resistance by means of radiation crosslinking is still interesting to many radiation chemists (Zhang et al., 1984; Li et al., 1996a,b; Ueno, 1990). The crosslinking reaction of polyamide is often simultaneous with the scission reaction during irradiation. The relationship between crosslinking and scission for polyamides is dependent mainly on the length of methylene group chain in the polyamide macromolecules and the condition of crystallinity (Deev et al., 1980). In this paper the radiation crosslinking of polyamide 610 in the presence of crosslinker, g-crystal nucleating agent and filler have been studied. The possible mechanism of crosslinking and scission was discussed.
2.1. Material
*Corresponding author. Tel.: +86-28-541-0252. E-mail address: [email protected] (W. Feng).
PA610 was purchased from Helongjiang Institute of chemical Industry; triallyl isocyanate (TAIC) was imported from Russia; potassium iodide (KI), iodine (I2 ) and m-cresol were obtained from Shanghai Chemical Reagent Station. Talcum powder was in commercial grade. All materials were used without further handling.
2.2. Sample preparation PA610 samples for radiation were prepared by blending the different additives in a twin-screw extruder. The samples for tensile strength test were prepared in the injection machine (made in Germany ARURG). The granular of PA were charged into the specially made ampoules. After being subjected to evacuation of the ampoules for 24 h, the samples were sealed in ampoules followed by irradiating with 60Co g-ray at various irradiation doses.
0969-806X/02/$ - see front matter r 2002 Published by Elsevier Science Ltd. PII: S 0 9 6 9 - 8 0 6 X ( 0 1 ) 0 0 6 3 5 - 1
W. Feng et al. / Radiation Physics and Chemistry 63 (2002) 493–496
494
2.3. The measurement of gel content 80
60
Gel Content/%
0.3 g of irradiated samples of PA610 at various dose were accurately weighed and put into the Soxhlet extractor. After extracting with m-cresol for 48 h and with methanol for 24 h, the residue was dried in the vacuum oven till the constant weight was obtained, based on which the gel content was calculated.
40
20
2.4. The measurement of properties 0
The size of dumbbell sample was 60 10 3 2 mm. The tensile strength and elongation were determined by using WD-5 Electron Universal Testing Equipment. The tensile strength at 2201C was measured by the machine equipped with a heat oven designed by us. The total quantity and composition of gas released from the PA samples during irradiation were measured by gas chromatography (PERKAN-ELMER SIGMA15).
0
75
150
225
300
375
450
Dose/kGy
Fig. 2. The effect of filler content on gel formation of PA610 during irradiation in vacuum (TAIC: 3 phr) talcum: (’) 25 phr; () 8 phr; (m) 4 phr (.) 2 phr; (E) 0 phr.
80
3. Results and discussion 3.1. The effects of additives and irradiation atmosphere on PA610
80
40
20
0 0
75
150
225
300
375
450
Dose/kGy
Fig. 3. The effect of filler content on gel formation of PA610 during irradiation in air (TAIC: 3 phr) talcum: (’) 25 phr; () 8 phr; (m) 4 phr; (.) 2 phr; (E) 0 phr.
80
60
Gel Content/%
The effects of various additives of TAIC, filler of talcum powder and g-crystal nucleating agents of KI and I2 (Deev et al., 1980) on the formation of gel of PA610 during irradiation are shown in Figs. 1–4. It can be seen from the Fig. 1 that there was almost no formation of gel in the absence of TAIC, indicating that the crosslinking and scission occurred simultaneously during irradiation of PA610. While the addition of 5 phr TAIC led to a marked increase of the gel content up to about 75%, which demonstrated that the crosslinking predominated over the scission reaction. On comparing PA610-TAIC it can be clearly seen that the overall
Gel Content/%
60
40
20
Gel Content/%
60
0 40
0
75
150
225
300
375
450
Dose/kGy
Fig. 4. The effect of crystal nucleating agent on gel formation of PA610 during irradiation in air (TAIC: 3 phr) KI+I2: () 0.06 wt%+0.06%; (’) 0 wt%.
20
0 0
75
150
225
300
375
450
Dose/kGy
Fig. 1. The effect of polyfunctional monomer on gel formation of PA610 during irradiation in air TAIC: (’) 5 phr; () 3 phr; (m) 0 phr.
tendency in density of the network is in the order of PA610-5 phrTAIC>PA610–3 phrTAIC>PA610. Thus, TAIC is very effective here as a crosslinking additive for PA 610 under irradiation.
W. Feng et al. / Radiation Physics and Chemistry 63 (2002) 493–496
3.2. The mechanical properties of radiation crosslinked PA610 In Figs. 5 and 6 are given the influence of both polyfunctional monomer and fillers on the mechanical properties of PA610 during irradiation in air. For PA610 with TAIC and filler the tensile strength grew and the elongation at break decreased with increasing the irradiation dose. In contrast, the tensile strength and the elongation of PA610 without TAIC and talcum fell, reflecting the degradation of PA610 during irradiation. These results indicated that the presence of talcum contributed to the formation of gel and density of network of PA610-TAIC. The tensile strength of irradiated PA610 at 2201C is shown in Fig. 7. Obviously, the irradiated PA610 still had certain tensile strength at this high temperature. The tensile strength increased with the increasing of gel content and then tended to be 130
Tensile Strength/MPa
120
250
Elongation/%
200
150
100
50
0 0
75
150
225
300
375
450
Dose/kGy
Fig. 6. The effect of filler content on the elongation of PA610 during irradiation in air talcum+TAIC: (’) 0 phr X talcum+3 phrTAIC: X: (E) 8 phr; (.) 4 phr; (m) 2 phr; () 0 phr. 10
8
Tensile Strength/MPa
It is noteworthy that in the presence of both talcum and TAIC the gel content rose faster with the increasing of content of talcum powder than that in the presence of TAIC as shown in Figs. 2 and 3. This implies that the gel formation can also be accelerated both in vacuum and air with talcum as an additive. In this case the residual filler of talcum was not found from the crosslinked PA610 upon extraction. It may suggest that during irradiation of PA610 the link was formed between talcum and macromolecule of PA610. Besides, there is very little difference in the formation of gel for PA610 in the atmosphere of air and vacuum. The minor influence of air atmosphere on the process of gel formation may be accounted for by the fact that PA610 was in granular state and the diffusion of oxygen to the inside of granular was very difficult. In the meanwhile KI+I2 was found to be of benefit to gel formation during irradiation of PA610 as shown in Fig. 4.The result is similar to that reported by Deev (Deev et al., 1980)
495
6
4
2
0 0
10
20
30
40
50
60
Dose/kGy
Fig. 7. The effect of filler content on tensile strength at 2201C of PA610 (3 phr TAIC) at different dose in air X talcum (’) 8 phr; () 4 phr; (m) 2 phr; (.) 0 phr.
stationary. The tensile strength for irradiated PA6103 phrTAIC-8 phr talcum at 2201C was raised to 8 MPa. In contrast, the unirradiated PA610 already melted at this temperature. Thus the PA 610 prepared here under g-irradiation in the presence of TAIC or talcum via crosslinking possessed the advantage in heat-resistance over the unirradiated one at higher temperature.
110
3.3. Gases released from pure PA610 during irradiation 100
90
0
75
150
225
300
375
450
Dose/kGy
Fig. 5. The effect of filler content on the tensile strength of PA610 during irradiation in air talcum+TAIC: (’) 0 phr X talcum+3 phr TAIC: X: (E) 8 phr; (.) 4 phr; (m) 2 phr; () 0 phr.
According to the structure of aliphatic polyamide the macromolecule consisted of different length of methylene group incorporated with amide group. However, the similar backbone as polyethylene did not provide the similar radiation-initiated reaction as observed here in the scission reaction due to the weaker cyanic link in the amide group. It means that the crosslinking and scission were concomitant during irradiation of PA610. Meanwhile, gases were released accompanying the process of crosslinking and scission of PA610 (Deev et al., 1980).
W. Feng et al. / Radiation Physics and Chemistry 63 (2002) 493–496
496
Table 1 Released gases from polyamides during irradiation Gas
Radiation chemical yield (molecule/100 eV)
H2 CO CH3CHO Total
PA6
PA610
PA1010
0.098 0.0013 Trace 0.0994
0.115 0.035 Trace 0.151
0.123 0.011 Trace 0.134
d
d
2CH2 2 C O þ N H2CH2 2CH2 2H2 -2CH2 2CHO þ NH2 CH2 2CH2 2 2CH2 2CH2 2CH2 2CHO r
d
d
2 2CH2 2 C H2 þ C H2 2CHO d
2 C H2 2CHO þ H2 -2CH3 2CHO:
Gas chromatographic analysis demonstrated that the gases were mainly composed of H2, CO and trace of acetaldehyde. The yield of gases or G value of these gases was dependent on the polyamide or the length of the chain of methylene group in the polyamide macromolecule. The results of analysis are summarized in Table 1. Obviously, hydrogen gas accounted for the majority among the three components released and its amount increased with increment of length of the chain of methylene group. Based on the above results, a similar mechanism (Deev et al., 1980) of radiation crosslinking and scission of PA610 during irradiation was proposed as follows: 2CH2 CONH2CH2 CH2 2 d
r
d
2 2CH2 2CONH2 C H2CH2 2 þ H
4. Conclusion 1. The crosslinking and scission occurred simultaneously during irradiation of PA 610. The presence of TAIC, filler of talcum powder and g-crystal nucleating agents of KI and I2 was beneficial to radiation crosslinking of PA 610 2. PA 610 in the presence of TAIC or talcum by girradiation crosslinking possessed the advantage in heat-resistance over the unirradiated one, especially at higher temperature (2201C), the tensile strength was almost retained for irradiated PA 610. 3. The mechanism of crosslinking and scission during irradiation of PA 610 was discussed based on the gas released.
d
2CH2 CONH2CH2 CH2 2 þ H d
-2CH2 2CONH2 C H2CH2 2 þ H2 d
22CH2 CONH2 C H2 CH2 2 -2CH2 2CONH2CH2CH2 2CH2 2CONH2CH2CH2 2 2CH2 2CONH2CH2 CH2 2 d
r
d
2 2CH2 2 C O þ N H2CH2 2CH2 2 d
d
2CH2 2CH2 2 C O-2CH2 2 C H2 þ CO d
22CH2 2 C H2 þ H2 -22CH2 2CH3
References Deev, U.S., Subbotin, U.S., Riabov, E.A., 1980. Radiationchemical modification of polyamide. Plastmasse 4, 52. Li, B.Z., Zhang, L.H., Yu, J.Y., 19963a. g-radiation damage to crystalline polyamide 1010 containing heterogeneous. J. Radiat. Res. Radiat. Proc. 14, 4. Li, B.Z., Zhang, L.H., Yu, J.Y., 1996b. Post radiation effects on polyamide 1010. J. Radiat. Res. Radiat. Proc. 14, 153. Ueno, K., 1990. Section 2.3. CrosslinkingFthe radiation crosslinking process and new products. Radiat. Phys. Chem. 35, 126. Zhang, L.H., Li, S.Z., He, Z.D., Su, W., Zhang, Z.C., 1984. Radiation-induced crosslinking of polyamide 1010. J. Radiat. Res. Radiat. Proc. 3, 32.