Synthesis and Properties of Melt Processable Acrylonitrile-N-vinylimidazole Copolymers and Fiber†

doi:10.7503/cjcu20150309

Abstract

Abstract:

Polyacrylonitrile(PAN) and acrylonitrile(AN)-N-vinylimidazole(VIM) copolymers[abbreviated as P(AN-co-VIM)] with various n(AN)∶n(VIM)(93∶7—80∶20) were synthesized by free-radical solution copolymerization in dimethyl formamide(DMF). The P(AN-co-VIM) copolymers(82∶18 and 80∶20) possessed good melt processability, which were melt spun at the temperature of 210—220 ℃. The crystallinity, thermodynamics behavior and the composition of P(AN-co-VIM) copolymers were studied and characterized by ubbelodhe viscosimeter, Fourier transform infrared spectroscopy(FTIR), nuclear magnetic resonance(¹H NMR), differential scanning calorimetry(DSC), X-ray diffraction(XRD) analyses and hot stage microscope. The results revealed that P(AN-co-VIM) could be synthesized successfully by free-radical solution copolymerization. P(AN-co-VIM) could be melt processable as VIM molar fraction is higher than 10%. The melting temperature of P(AN-co-VIM) shifts continuously to the lower temperature with the comonomer contents increasing. When the molar fraction of VIM is increased to 20%, the melting point of P(AN-co-VIM) copolymer reduced from 317 ℃ to 180 ℃. The highest decomposition temperature is 313.7 ℃. The apparent morphology and mechanical properties of the P(AN-co-VIM) fibers were characterized by scanning electron microscope(SEM) and single fiber electronic tensile strength test. The results show that the fibers have smooth surface and compact cross section. As-spun P(AN-co-VIM) fiber gets the fracture strength of 1.58 cN/dtex and the elongation at break attained 11.2%. After post-treatment, the fiber is expected to be widely used in the field of carbon fiber.

Key words: Acrylonitrile, N-vinylimidazole, Solution copolymerization, Melt spinning, Fiber

CLC Number:

TrendMD:

HAN Na, LI Huihui, LI Chuanbao, ZHANG Xingxiang, LI Wei, WANG Dong. Synthesis and Properties of Melt Processable Acrylonitrile-N-vinylimidazole Copolymers and Fiber^†[J]. Chem. J. Chinese Universities, 2015, 36(10): 2073.

Figures/Tables 15

Table 1 P(AN-co-VIM) prepared with various n(AN)∶n(VIM)

P(AN-co-VIM)	n(AN)∶n(VIM)		Conversion(%)
P(AN-co-VIM)	Feed		Copolymer
A	100∶0	100.0∶0	88.5
B	93∶7	91.1∶8.9	66.2
C	90∶10	84.7∶15.3	68.9
D	88∶12	83.1∶16.9	78.0
E	85∶15	80.1∶19.9	83.5
F	82∶18	73.8∶26.2	72.9
G	80∶20	72.3∶27.7	84.9

Fig.1 FTIR spectra of PAN(a) and P(AN-co-VIM) copolymers(b—g)n(AN)∶n(VIM): a. 100∶0; b. 93∶7; c. 90∶10; d. 88∶12; e. 85∶15; f. 82∶18; g. 80∶20.

Fig.2 1H NMR spectrum of P(AN-co-VIM)(85∶15) copolymer

Fig.3 DSC heating curves(10 ℃/min) of PAN(a) and P(AN-co-VIM) copolymers(b—g)n(AN)∶n(VIM): a. 100∶0; b. 93∶7; c. 90∶10; d. 88∶12; e. 85∶15; f. 82∶18; g. 80∶20.

Table 2 Thermodynamic data of PAN and P(AN-co-VIM) copolymers

Sample	n(AN)/n(VIM)	T_g/℃	T_m/℃	T_do/℃	T_dp/℃
A	100∶0	135.0		261.6	265.2
B	93∶7	113.2	232.2	273.7	284.1
C	90∶10	112.7, 148.6	199.4	276.1	291.4
D	88∶12	114.0, 149.7	200.2	281.6	296.5
E	85∶15	117.1		286.9	302.1
F	82∶18	120.8		299.2	312.6
G	80∶20	118.9		294.7	313.7

Fig.4 DSC heating curves(60 ℃/min) of PAN(a) and P(AN-co-VIM) copolymers(b—g)n(AN)∶n(VIM): a. 100∶0; b. 93∶7; c. 90∶10; d. 88∶12; e. 85∶15; f. 82∶18; g. 80∶20.

Fig.5 DSC cooling curves(60 ℃/min) of PAN(a) and P(AN-co-VIM) copolymers(b—g)n(AN)∶n(VIM): a. 100∶0; b. 93∶7; c. 90∶10; d. 88∶12; e. 85∶15; f. 82∶18; g. 80∶20.

Fig.6 Hot stage microscope photos of P(AN-co-VIM)(85∶15) copolymer Temprature/℃: (A) 170; (B) 180; (C) 190; (D) 200.

Table 3 Melting temperature range of PAN and P(AN-co-VIM)

Sample	n(AN)∶n(VIM)	Melting temperature range/℃	Sample	n(AN)∶n(VIM)	Melting temperature range/℃
A	100∶0	Not melt	E	85∶15	170—200
B	93∶7	Not melt	F	82∶18	170—190
C	90∶10	190—200	G	80∶20	170—180
D	88∶12	190—205

Fig.7 X-ray diffraction patterns of PAN(a) and P(AN-co-VIM) copolymers(b—g)n(AN)∶n(VIM): a. 100∶0; b. 93∶7; c. 90∶10; d. 88∶12; e. 85∶15; f. 82∶18; g. 80∶20.

Table 4 Crystallinity and crystallite dimension of PAN and P(AN-co-VIM) copolymers

Sample	n(AN)∶n(VIM)	Crystallinity (%)	Crystallite dimension/nm	Sample	n(AN)∶n(VIM)	Crystallinity (%)	Crystallite dimension/nm
A	100∶0	48.4	4.0	E	85∶15	41.1	2.3
B	93∶7	38.3	3.3	F	88∶12	41.0	2.0
C	90∶10	41.0	2.6	G	80∶20	35.8	1.9
D	88∶12	39.0	2.4

Fig.8 SEM images of the surface of melt-spinning P(AN-co-VIM) fibers(A) P(AM-co-VIM)(82∶18); (B) P(AN-co-VIM)(80∶20).

Fig.9 SEM images of the cross-cutting section(A) and pull-broken section(B) of P(AN-co-VIM)(80∶20) fiber

Fig.10 Stress-strain curves of as-spun P(AN-co-VIM) fibers by melt spinning a. P(AN-co-VIM)(82∶18); b. P(AN-co-VIM)(80∶20).

Table 5 Physical mechanical properties of melt-spinning P(AN-co-VIM) fibers

Sample	n(AN)∶n(VIM)	Fineness/dtex	Tenacity/cN	Elongation(%)	Breaking strength/(cN·dtex^-1)
A	82∶18	104	145	7.1	1.4
B	80∶20	120	190	11.2	1.6

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