Study of radiation graft styrene onto preirradiated polychlorotrifluoroethylene films

Radlat Phys Chem Vol 31, Nos 4-6, pp 805-808, 1988 Int J Rater Appl lnstrum Part C Planted m Great Bntmn

0146-5724/88

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STUDY ON RADIATION GRAFT STYRENE ONTO PREIRRADIATED POLYCHLOROTRIFLUOROETHYLENE FILMS

Zhao Xiang-zhen

Jin Ji-lin

Shanghai Institute of Organic Chemistry Academia Sinica

ABSTRACT In this paper, we reported that peroxy fluoropolymeric radicals produced in polychlorotrifluoroethylene (PCTFE) during irradiation were slowly decayed and existed at room temperature over 9 years, which were shown by ESR and the graft reaction of styrene onto preirradiated PCTFE films. ~O~S Preirradiated! graft ; radicals; ESR; fluoropolymers. Through a long period of observatlon of the decay of fluorine containing polymeric radicals at room temperature, we found that the peroxy fluoropolymeric radicals existing in preirradiated polychlorotrifluoroethylene films decay slowly at room temperature, they exist over 6 years (Zhao Xiang-zhen, 1981, 1982a, 1982b, 1984, 1986). This finding has both scientific and practical importance. It shows that in nature there are some active radicals which are stable at room temperature for a long time, but also indicate many important practical uses. For example, some radiation graft copolymers can be produced by preirradiation methods in factory without radiation sources. Parts of the enormous radiation energy emerged from the nuclear reactors can be transformed to chemical energy and stored for futher applications. Therefore we observe the decay of peroxy fluoropolymeric radicals continuously. The present paper reports some new results. The concentration of radicals contained in PCTFE films irradiated with fast electrons in air which stored at room temperature after 2758 days, 3461 days, 3390 days were determined by ESR.

Fig. i.

ESR spectrum from PCTFE film irradiated with fast electrons subjected to 3.5 k@y in air and standing at room temperature for 2758 days, concentration of free radicals: 5.36 x lOlTe/g

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ZHAO XIANC,-7.,HENand J ~ JI-LIN

Fig. 2.

Fig. 3.

ESR spectrum from PCTFE film irradiated with fast electrons subjected to 3.5 kGy in air and standing at room temperature for 3461 days, concentration of free radicals: 3.99 x lO17e/g

ESR spectrum from PCTFE film irradiated with fast electrons subjected to 14 kGy in air and standing at room temperature for 3390 days, concentration of free radicals: 9.15 x lO17e/g

It can be seen that the long lived peroxy fluoropolymeric radicals still exist. The concentration of radicals existing in PCTFE films subjected to 3.5 kGy which stored at room temperature after 2758 days was 5.36 x lOl7e/g, and it was 3.99 x lOiYe/g after 3461 days. The radicals decay slowly. Moreover, the more the dose, the more the concentration of radicals. When the preirradiated I~TI~ films subjected to 14 kGy, the concentration of radicals was 9.15 x lOlTe/g after 3390 days. Such long lived fluoropolymeric radicals still have the chemioKl activity, they initiated the polymerization of styrene, and graft copolymers are formed.

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TABLE 1.

807

Graft Polymerization of Styrene onto Preirradiated Polychlorotrifluoroethylene

Time Standing at Room Temperature (days)

Reaction Temperature (°C)

(hrs)

3559 (3.5 kOy)

50

24

19.3

5487 (14 kGy)

50

24

34.8

TABLE 2.

Reaction Time

Unirradiated 763 1033 1313 1644 6 years 6 years

50 50 50 50 30 25 50

Unirrad i at ed

56 key 2806

(%)

48 48 48 48 120 289 24

0.46 21.4-23.9 19.3 20.5 62.5 55.4 30.2

Percentage Graft % Heat Treated 90°C for 72 hrs

14 key 2853

Percentage Graft

Graft Polymerization of Styrene onto Preirradiated Polychlorotrifluoroethylene Film Standing at Room Temperature Over 8 Years

Films

3.5 key 2923

(%)

Graft Polymerization of Styrene onto Preirradiated Polychlorotrifluoroethylene Dose: 3.5 kGy N 2

Time Reactlon Reaction Standing at Temperature Time Room Temperature (days) (°C) (hrs)

TABLE 3 •

Percentage Graft

Water Treat ed 3000 for 94 hrs

50°0

30°0

50°C

50°0

24 hrs

N2

24 hrs

24 hrs

N2

N2

4.1-5.3 288 hrs 1.9 2 20.77 166 hrs 3.6 22.49 47.58 48.O9 22.2 142 hrs 10.9 61.6 24.33 71.1 28.46 50 hrs 22.4 28.8 16.07 19.62

4.2 23.3

26.6

28.7

808

ZHAO XiANG-zt-mN and J ~ Jt-L~

See table i. PCTFE films irradiated with dose 3.5 kGy after 3558 days at room temperature reacted with styrene at 50oc in N2 for 24 hours, a percentage ~raft 19.3% was obtained. The films irradiated with dose 14 kGy after 3487 days at room temperature reacted with styrene under the same conditions, percentage graft reached 34.8%. The extremely hzgh stability of fluoropolymerlc radicals is dub to exclusion of disproportionation reaction on fluoroorganic radicals (Stefani A. P. 1971), hydrogen abstraction reactions not proceed in fluoroorganic compounds (Zhao Xiang-zhen 1982), and the weak intermolecular force of fluoroorganic compounds. The results of graft reaction of preirradiated PCTFE films subjected to 3.5 kGy standing at room temperature after various days with styrene was shown in table 2. Under the same reaction conditions the graft reaction can not proceed in unirradiated PCTFE films. From table 2, it can be found that the graft reaction of styrene proceeding at 25oc for a long time gave a high percentage graft since the rate of termination was lower at 25°C. 3 preirradiated PCTFE films subjected to various doses stored at room temperature over 8 years reacted with styrene in N2 for 24 hrs at 30°C, 50°C respectively, and compared with the results of unirradiated PCTFE films, which reacted with styrene under the same reaction conditions. From preirradzated films the graft copolymers were obtained, degree of grafting were over 20%. The graft reaction of unzrradiated PCTFE films failed of success. Experimental data are presented in table 3. In order to test the thermal stability of peroxy fluoro-polymeric radicals existzng in preirradiated PCTFE films, we treated the preirradiated films at 95oc for 72 hrs, then conducted the reaction with styrene as before. Table 3 shows, that the percentage graft of all samples decreased, the lower the dose the more depressed the percentage graft of styrene. At 3.5 kGy dose the percentage graft was merely 2~, and at 56 kGy 22.4% obtained, which was less than the untreated films. The peroxy fluoropolymeric radicals are stable in H20. When the preirradiated PCTFE films were immersed in H20 at 30°C for 94 hrs, then reacted with styrene, the obtained results were the same as results from untreated films. The cation exchange membrane was obtained by chlorosulfonation and hdrolysis of the polychlorotrifluoroethylene-styrene cepolymer films. This cepolymer films can also be transferred to the anion exchange membrane through the chloromethylation and aminat~on. Both membranes have excellent chemical stability and ion permeabzlity.

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REFERENCES Zhao Xiang-zhen (1981) NATURE (China), Vol. 4(12) 950 Zhao Xiang-zhen (1982) HE HUAXUE YU FANGSHE HUAXUE Vol. 1(2) lll Zhao Xiang-zhen, Li Zhong-zhen (1982) Organic Chemistry No. 4, 279 Zhao Xiang-zhen (1984) Journal of Radiation Research and Radiation Processing Vol. 2(4) 58 Zhao Xiang-zhen, Jin Jz-lin (1986) POLYMER COMMUNICATIONS No. 4, 270 Stefani A. P. (1971) Fluorine Chemistry Review Vol. 5, 133