Preparation and properties of pitch plasticized melt spinning polyacrylonitrile-based carbon fibers precursor
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摘要: 为了降低聚丙烯腈(PAN)的熔点和提升熔纺PAN纤维的性能，本文以各向同性萘沥青(INP)和煤焦油沥青(ICP)作为增塑剂，比较了二者对85∶14∶1 摩尔比的聚(丙烯腈-丙烯酸甲酯-4-丙烯酰氧基二苯甲酮)三元共聚物(P(AN-MA-ABP))的增塑效果。优选1wt%的INP与P(AN-MA-ABP)充分混合、熔融纺丝、牵伸制备了1wt%INP/P(AN-MA-ABP)共聚物纤维，并研究了紫外(UV)辐照时间对1wt%INP/P(AN-MA-ABP)共聚物纤维的影响。结果表明：相比于稠环结构的ICP，长链含硫杂环结构的INP具有良好的增塑效果。制备的1wt%INP/P(AN-MA-ABP)共聚物纤维直径约52 μm，拉伸强度约250 MPa，表面光滑，结构致密。UV辐照时间从0 min增加到60 min，纤维表面氧含量由17.3%提高到26.0%。氮气条件下，环化起始温度由303.8℃降到292.4℃，环化峰值温度由318.0℃降到308.8℃。空气条件下，环化起始温度由299.9℃降到295.0℃，环化峰值温度由316.4℃降到312.6℃。UV辐照20 min，氮气条件下800℃时纤维的碳收率由41.0%提高到43.4%。UV辐照降低了1wt%INP/P(AN-MA-ABP)共聚物纤维的环化起始温度、峰值温度、焓值，提高了碳收率，有利于后续热处理。Abstract: In order to reduce the melting point of polyacrylonitrile (PAN) and improve the properties of melt-spun PAN fibers, the effects of isotropic naphthalene pitch (INP) and coal tar pitch (ICP) as plasticizers on 85∶14∶1 mole percent poly(acrylonitrile-methyl acrylate-4-acryloxy dibenzophenone) terpolymer (P(AN-MA-ABP)) were investigated in detail. The 1wt%INP/P(AN-MA-ABP) terpolymer fibers were prepared by mixing 1wt%INP with P(AN-MA-ABP), and then melting spinning and drawing. The effects of UV irradiation time on 1wt%INP/P(AN-MA-ABP) terpolymer fibers were studied. The results show that the long-chain sulfur heterocyclic INP has a better plasticizing effect than the ICP with a thick ring structure. The diameter of the 1wt%INP/P(AN-MA-ABP) terpolymer fibers is about 52 μm, and the tensile strength is about 250 MPa, which has a smooth surface and a dense structure. Delaying the UV irradiation from 0 min to 60 min, the oxygen content on the surface of 1wt%INP/P(AN-MA-ABP) terpolymer fibers increases from 17.3% to 26.0%. Under nitrogen conditions, the initial cyclization temperature decreases from 303.8℃ to 292.4℃, and the cyclization peak temperature decreases from 318.0℃ to 308.8℃. Under air conditions, the initial cyclization temperature decrease from 299.9℃ to 295.0℃, and the cyclization peak temperature decreases from 316.4℃ to 312.6℃. After UV irradiation for 20 min, the carbon yield of 1wt%INP/P(AN-MA-ABP) terpolymer fibers carbonized at 800℃ under nitrogen increases from 41.0% to 43.4%. UV irradiation decreases the initial cyclization temperature, peak temperature, and enthalpy value of 1wt%INP/P(AN-MA-ABP) terpolymer fibers and increases the carbon yield, which are beneficial to the subsequent heat-treatment process.
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Key words:
- pitch /
- plasticizer /
- melt spinning /
- polyacrylonitrile (PAN) /
- carbon fiber /
- precursor
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图 1 聚(丙烯腈-丙烯酸甲酯-4-丙烯酰氧基二苯甲酮)(P(AN-MA-ABP))三元共聚物的FTIR图谱
Figure 1. FTIR spectrum of poly(acrylonitrile-methyl acrylate-4-acryloxy dibenzophenone) terpolymer (P(AN-MA-ABP)) terpolymer
图 2 P(AN-MA-ABP)三元共聚物的1H NMR图谱
Figure 2. 1H NMR spectrum of P(AN-MA-ABP) terpolymer
AN—Acrylonitrile; MA—Methyl acrylate; ABP—Acryloyl benzophenone
图 4 INP/P(AN-MA-ABP)和ICP/P(AN-MA-ABP)熔体流动指数 (MFI) 曲线
Figure 4. Melt flow index (MFI) curves of INP/P(AN-MA-ABP) and ICP/P(AN-MA-ABP) melt
图 5 INP/P(AN-MA-ABP)和ICP/P(AN-MA-ABP)熔体黏度随剪切速率的变化曲线
Figure 5. Viscosity curves of INP/P(AN-MA-ABP) andICP/P(AN-MA-ABP) melt with shear rate
图 6 1wt%INP/P(AN-MA-ABP)三元共聚物纤维的EDS图：(a) 表面的元素含量；(b) 表面的元素分布
Figure 6. EDS diagram of 1wt%INP/P(AN-MA-ABP) terpolymer fibers: (a) Surface element content; (b) Surface element distribution
图 7 UV辐照不同时间的1wt%INP/P(AN-MA-ABP)三元共聚物纤维的凝胶含量
Figure 7. Gel contents of 1wt%INP/P(AN-MA-ABP) terpolymer fibers irradiated by UV for different time
图 8 UV辐照不同时间的1wt%INP/P(AN-MA-ABP)三元共聚物纤维的FTIR图谱
Figure 8. FTIR spectra of 1wt%INP/P(AN-MA-ABP) terpolymer fibers irradiated by UV for different time
图 9 空气气氛下UV辐照PAN的环化机制
Figure 9. Mechanism of PAN cyclization under UV irradiation in air atmosphere
图 10 UV辐照不同时间的1wt%INP/P(AN-MA-ABP)三元共聚物纤维的DSC曲线：(a)氮气；(b)空气
Figure 10. DSC curves of 1wt%INP/P(AN-MA-ABP) terpolymer fibers irradiated by UV for different time: (a) N2； (b) Air
图 11 氮气条件下UV辐照不同时间的1wt%INP/P(AN-MA-ABP)三元共聚物纤维的TGA和DTG曲线
Figure 11. TGA and DTG curves of 1wt%INP/P(AN-MA-ABP) terpolymer fibers irradiated by UV at different time under nitrogen condition
图 12 UV辐照1wt%INP/P(AN-MA-ABP)三元共聚物纤维的SEM图像
Figure 12. SEM images of 1wt%INP/P(AN-MA-ABP) terpolymer fibers irradiated by UV
表 1 样品的组成编号
Table 1. Composition number of the samples
Sample P(AN-MA-ABP)/wt% INP/
wt%ICP/
wt%0.5wt%INP/P(AN-MA-ABP) 99.5 0.5 – 1wt%INP/P(AN-MA-ABP) 99.0 1.0 – 3wt%INP/P(AN-MA-ABP) 97.0 3.0 – 5wt%ICP/P(AN-MA-ABP) 95.0 – 5.0 Notes: INP—Isotropic naphthalene pitch; ICP—Isotropic coal tar pitch; P(AN-MA-ABP)—Poly(acrylonitrile-methyl acrylate-4-acryloxy dibenzophenone) terpolymer. 
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表 2 P(AN-MA-ABP)三元共聚物的组成与性质
Table 2. Composition and properties of P(AN-MA-ABP) terpolymers
Feed ratio
/mole percentComposition
/mole percentMn/(g·mol−1) Mw/(g·mol−1) Mw/Mn Melt processible 85∶14∶1 84.3∶14.3∶1.4 25000 52000 2.1 Yes 85∶14∶1 84.5∶14.2∶1.3 49000 74000 1.5 No 85∶14∶1 84.4∶14.3∶1.3 15000 30000 2.0 Yes 85∶14∶1 84.2∶14.4∶1.4 21000 42000 2.0 Yes Notes: Mn—Number average molecular weight; Mw—Weight average molecular weight.
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表 3 同性萘沥青(INP)和煤焦油沥青(ICP)的元素组成(单位：wt%)
Table 3. Element composition of isotropic naphthalene pitch (INP) and coal tar pitch (ICP) (Unit: wt%)
Pitch C H N S O INP 67.6 2.1 0.2 27.1 1.2 ICP 84.7 5.1 1.2 0.4 5.5
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表 4 熔纺聚丙烯腈(PAN)纤维的力学性能
Table 4. Mechanical properties of melt-spun polyacrylonitrile (PAN) fibers
Sample Diameter/
μmTensile
strength/
MPaElongation/% P(AN-MA-ABP) 51±1.8 247.3±6.4 15.5±2.4 0.5wt%INP/P(AN-MA-ABP) 51±2.3 245.6±8.1 17.5±2.6 1wt%INP/P(AN-MA-ABP) 50±2.1 241.6±7.8 18.1±3.4 3wt%INP/P(AN-MA-ABP) 50±2.5 214.3±8.3 17.2±4.5 5wt%ICP/P(AN-MA-ABP) 52±1.7 175.9±7.9 23.2±5.1
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表 5 UV辐照不同时间的1wt%INP/P(AN-MA-ABP)三元共聚物纤维的原子浓度数据和原子比
Table 5. Atomic concentration data and atomic ratio of 1wt%INP/P(AN-MA-ABP) terpolymer fibers irradiated by UV at different time
Element Atomic concentration/at% Non-irradiated UV 20 min UV 40 min UV 60 min C 74.6 72.0 69.9 67.0 O 17.3 21.3 22.3 26.0 N 8.1 6.7 7.8 7.0 O/C 0.2 0.3 0.3 0.4 N/C 0.1 0.1 0.1 0.1
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表 6 UV辐照不同时间的1wt%INP/P(AN-MA-ABP)三元共聚物纤维的DSC热力学数据
Table 6. DSC thermodynamic data of 1wt%INP/P(AN-MA-ABP) terpolymer fibers irradiated by UV at different time
Atmosphere UV irradiation time/min Tonset
/℃TM
/℃△Hc
/(J·g−1)Nitrogen 0 303.8 318.0 537.8 20 296.4 310.6 474.8 40 294.0 309.1 443.7 60 292.4 308.8 442.1 Air 0 299.9 316.4 725.8 20 299.6 314.4 683.7 40 297.7 314.2 678.4 60 295.0 312.6 676.4 Notes: Tonset—Onset temperature of exothermic reaction (10℃/min); TM—Maximum temperature of exothermic reaction (10℃/min); ΔHc—Enthalpy of exothermic reaction (10℃/min).
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表 7 UV辐照不同时间的1wt%INP/P(AN-MA-ABP)三元共聚物纤维的力学性能
Table 7. Mechanical properties of 1wt%INP/P(AN-MA-ABP) terpolymer fibers irradiated by UV at different time
UV irradiation time/min Tensile strength/MPa Elongation/% 0 252.8±6.3 15.5±2.4 20 247.5±7.8 15.8±3.5 40 243.6±8.3 16.9±2.6 60 231.5±7.1 16.1±2.2
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