Hiremath等[14]在纺织级PAN基复合长丝中实现了 C-CNF的均匀分散,并通过在丙烯腈表面接枝C-CNF提高其在PAN纤维基体中的分散性。结果表明,与对照组相比,加入3.2%功能化C-CNF并经牵伸处理后的复合纤维,其拉伸强度和弹性模量均提高了3倍以上。Chang等[15]将纤维素纳米晶(CNC)分散于PAN中,发现CNC的引入显著改善了 PAN 纤维的综合性能,且环化反应和交联反应的活化能分别降低了17.5% 和19%。Krishnaswamy等[16]探讨了聚酰胺6/SA复合材料的制备及其对气凝胶结构完整性的影响,发现当填料含量为0.04%时,气凝胶在复合材料中的结构完整性能够得到较好保持。Sedighi等[17]分别以 0.4%、1%和2%的质量分数成功制备了填充SA的聚酯复合纤维,结果表明该纤维具有实心截面、表面粗糙及疏水等特性。
自2003年以来,有研究围绕PAN基共聚物的可熔融改性开展了系统研究,并成功实现了可熔融PAN基共聚物的批量制备[18-
1 实验部分
1.1 实验材料与仪器
亲水性SiO2气凝胶(SA),天津朗盛高新材料科技有限公司;氨水(NH4OH)、乙烯基三乙氧基硅烷(VTES)、4-丙烯酰氧基二苯甲酮(ABP)、羧基化纤维素纳米纤维(C-CNF,4~10 nm,6% 分散液)以及过硫酸铵((NH4)2S2O8),上海麦克林生化科技股份有限公司;无水乙醇(C2H5OH),天津丰川化学试剂科技有限公司;丙烯腈(AN)、丙烯酸甲酯(MA)、亚硫酸氢钠(NaHSO3)、正十二烷基硫醇(RSH)和十二烷基硫酸钠(SDS),天津美鼎科技有限公司;N,N-二甲基甲酰胺(DMF)、溴化锂(LiBr),上海阿拉丁生化科技股份有限公司;乳化剂(OP-10)、无水硫酸镁(MgSO4),北京宇晟化工有限公司。
WIGGENS D-500D数显均质乳化机(维根技术北京有限公司);BFDUV-X2K240紫外光固化机(深圳市博飞达科技有限公司);JC-QM-4行星式球磨机(青岛聚创华业分析仪器有限公司)HTGD-20双螺杆挤出机(广州市哈尔技术有限公司);Autosorb-iQ-C全自动物理化学吸附仪(美国康塔仪器公司);Mastersizer2000激光粒度分析仪(英国马尔文公司);Tensor 37傅里叶变换红外光谱仪(赛默飞世尔科技);DRL-III导热系数测试仪(湖南振华分析仪器有限公司);Waters 1525凝胶渗透色谱仪(沃特世公司);XNR-400C型熔体流动速率仪(承德市纵驰检测仪器有限公司);D8 DISCOVER X射线衍射仪(布鲁克科技有限公司);TGA Q5000 热重分析仪、DSC200F3差示扫描量热仪(德国耐驰制造有限公司);S4800扫描电子显微镜(HITACHI公司);LLY-11B单纤维强力仪(山东省纺科院科技有限公司)。
1.2 PAN/C-CNF聚合物的制备
将适量去离子水、乳化剂OP-10、SDS以及RSH混合后充分乳化,加入到三口烧瓶中并通10 min N2。量取一定量AN和MA单体倒入三口烧瓶,加入占单体总质量0.1%的C-CNF分散液,在60 ℃下反应。反应结束后将无水硫酸镁溶于水中,再将所得乳液倒入其中进行破乳,随后经静置、过滤、洗涤和干燥后得到PAN/C-CNF聚合物。
1.3 SA-PAN的制备
称取15 g SA,用无水乙醇充分浸润后分散于1 000 mL水中,加入50 g VTES,水解 3 h;随后加入 15 mL 氨水,在 40 ℃下搅拌反应 4 h 后终止反应,经离心洗涤并真空干燥72 h,制得SA-VTES[21]。将AN、ABP、无水乙醇和水按照质量比35∶3∶60∶2加入烧杯中混合均匀,配制改性溶液。将SA-VTES先用无水乙醇浸润后加入改性溶液中,使用数显均质乳化机快速分散,再继续搅拌2 h 使其混合均匀,随后在紫外光固化机中反应2 h。反应完成后,经离心洗涤并真空干燥72 h得到SA-PAN。
1.4 熔融纺丝PAN基隔热纤维的制备
将含不同比例SA-PAN的PAN/C-CNF混合物置于行星式球磨机中混合均匀,再经螺杆挤出机挤出造粒得到纺丝原料。随后将纺丝原料加入双螺杆纺丝机中进行熔融纺丝。挤出机转速为50 r/min,纤维收集速度为300 r/min,螺杆5个温区的温度分别设定为160、180、185、190和195 ℃。之后在热辊上对纤维进行热牵伸,牵伸温度为110~120 ℃。最终制得SA-PAN 质量分数分别为1%、3%、5%和7% 的 PAN/C-CNF/SA-PAN纤维,分别记为PCS1%、PCS3%、PCS5% 和 PCS7% 纤维。采用上述相同方法,进一步制得熔融纺丝PAN纤维和PAN/C-CNF 纤维,分别记为PAN纤维和PC纤维。
1.5 表征与测试
1.5.1 孔径和粒径测试
采用全自动物理化学吸附仪在N2条件下进行孔径吸附-脱附测试,表征SA孔结构特性。测试前取适量SA样品,在120 ℃真空脱气处理6 h消除吸附水与残留小分子。以N2为吸附介质,低温采集吸附-脱附等温线。基于BET理论计算比表面积,借助BJH模型解析孔径分布、总孔容及平均孔径;采用激光粒度分析仪测试SA的粒径分布。测试前取少量SA分散于无水乙醇中,超声波分散10 min实现充分分散,以无水乙醇为分散介质,设置折射率参数完成测试,获取样品粒径尺寸与分布曲线。
1.5.2 隔热性能测试
采用导热系数测试仪在室温环境下表征纤维织物的导热性能。为方便测试,将纤维编织成尺寸为5 cm×5 cm的方形织物试样,测试时取2块完全一致的织物分别置于探头上下两侧包裹传感探头,保证接触紧密;每组平行测试3次,记录并计算样品平均热导率,热扩散系数由导热系数测试仪同步测得。
1.5.3 化学结构表征
采用傅里叶变换红外光谱仪(FT-IR)分别对SA、聚合物及纤维样品进行化学结构表征。测试波数范围为4 000~400 cm-1,光谱分辨率设置为4 cm-1。其中,聚合物及气凝胶粉体采用压片法制样测试;纤维织物采用衰减全反射法(ATR)直接测试,无需压片处理。
1.5.4 聚合物分子量测试
在室温下将聚合物样品溶于的DMF中,以溴化锂作为洗脱剂,通过尺寸排阻色谱法测定合成聚合物的重均分子量(Mw)、数均分子量(Mn)及分子量分布指数(PDI)。
1.5.5 聚合物晶体结构表征
采用X射线衍射仪(XRD)分别对SA与纤维样品进行物相结构表征。测试辐射源为Cu Kα射线,设置管电压为40 kV、管电流为40 mA,扫描速率为5 (°)/min,2θ扫描区间为5°~45°。通过所得衍射图谱分析气凝胶的无定形特征及纤维的结晶结构变化。
1.5.6 熔体流动测试
参照GB/T 3682.1—2018《塑料 热塑性塑料熔体质量流动速率(MFR)和熔体体积流动速率(MVR)的测定 第1部分:标准方法》,采用熔体流动速率仪测试不同SA添加量PAN复合材料的熔体流动速率。测试温度为210℃,加载砝码总质量为2.16 kg。将干燥后的样品颗粒装入料筒并恒温熔融,稳定后在恒定载荷挤压下挤出熔体,截取并称量10 min内挤出的熔体质量,计算得到样品熔体流动速率,用以评价不同SA添加量PAN复合材料的熔融加工流动性。
1.5.7 微观形貌表征
采用场发射扫描电子显微镜观察SA、聚合物及纤维的微观形貌,使用配套EDS能谱仪对纤维表面开展元素面扫,分析SiO2填料在PAN基体中的分散均匀性。SA及聚合物粉末直接粘贴于导电胶上待测。纤维样品分为2组,一组剪刀裁切观察表面形貌,另一组经液氮冷冻脆断获取平整横截面,所有样品均真空喷金消除荷电效应,设置低加速电压分别采集气凝胶和聚合物颗粒、纤维表面、纤维脆断面微观图像。
1.5.8 热稳定性测试
采用热重分析仪在N2氛围下测试样品的热稳定性。测试前,将样品充分干燥,取适量样品置于热重分析坩埚中。测试温度范围为室温至800 ℃,升温速率为 10 ℃/min。测试过程中记录样品质量随温度升高的变化,获得TG曲线和DTG曲线。通过分析样品的初始质量损失温度、主要热分解温度区间、最大质量损失速率温度及800 ℃下残炭率,评价C-CNF和SA-PAN对PAN基纤维热稳定性及耐高温性能的影响。采用差示扫描量热仪表征PAN基纤维的热转变性能。测试全程通入N2保护,样品以10 ℃/min的升温速率从20 ℃升温至230 ℃,恒温10 min以消除内部热历史,随后以10 ℃/min的降温速率冷却至20 ℃,获得纤维的熔融和结晶热学特征参数。
1.5.9 力学性能测试
为了增强纤维的力学强度,对不同样品纤维进行不同倍率的热牵伸(最后一个热辊速率与初始热辊速率的比值即为牵伸倍数),3个热辊温度分别为90、100、110 ℃。采用单纤维强力仪测试纤维的力学性能。测试前,选取表面较完整且无明显缺陷的单根纤维作为测试样品。测试时,将单根纤维固定于强力仪上下夹具之间,夹持距离设定为10 mm,拉伸速度设定为10 mm/min。启动仪器后对纤维进行拉伸,直至纤维断裂,记录断裂强度和断裂伸长率。每组样品至少测试10次,去除明显异常值后取平均值,用于评价C-CNF和SA-PAN添加量对PAN基隔热纤维力学性能的影响。
2 结果与讨论
2.1 改性SiO2气凝胶的结构与性能
图1(a)、(b)分别示出SA和SA-PAN的BET吸附-脱附曲线。SA的比表面积、孔体积和孔径分别为171.271 m2/g、0.442 cm3/g、2.519 nm;SA-PAN的分别为 127.475 m2/g、0.316 cm3/g、2.195 nm。与SA相比,SA-PAN的比表面积、孔体积和孔径均有所下降。通常情况下,较小的孔径和较高的孔隙率有利于材料隔热性能的提升[22]。图1(c)表明,原始SA的平均粒径为28.416 μm,主要分布在0~25 μm范围内,且分布较为均匀;SA-VTES的平均粒径降至 12.177 μm,粒径分布仍保持均匀;SA-PAN的平均粒径进一步减至6.079 μm,且粒径分布更加集中,这有利于其在熔融加工制备复合隔热纤维过程中实现更均匀的分散。
图1
图1
SA及改性气凝胶的结构与热性能
Fig.1
Structural and thermal properties of SA and modified aerogels. (a) BET adsorption-desorption isotherms of SA; (b) BET adsorption-desorption isotherms of SA-PAN; (c) Particle size distribution of SA and modified aerogels; (d) FT-IR spectra; (e) TG curves; (f) Infrared thermal imaging curves recorded on hot stage at 65 ℃
由图1(d)可知,SA-VTES在1 410和1 600 cm-1处分别出现了烯烃的特征吸收峰,对应于C—H面内弯曲振动和C══C键伸缩振动;在约3 000 cm-1处出现了烯烃(══C—H)的伸缩振动峰。SA-PAN在1 450 cm-1处出现与PAN相同的—CH2弯曲振动峰,并在2 240 cm-1处出现了PAN的特征吸收峰,该峰归属于C≡N氰基的伸缩振动[23]。图1(e)显示,SA在800 ℃下的质量损失率为2.23%,表现出良好的耐高温性能。SA-VTES的质量损失率为 6.63%,较SA提高了4.40%。SA-PAN的质量损失率为 14.00%,分别较SA-VTES和SA提高了7.37%和 11.77%,且其质量损失曲线与PAN相似。这表明PAN 已成功接枝到SA-PAN中,接枝率为20.4%;同时,材料仍保持了SA优异的耐高温性和较高的热稳定性。
由图1(f)可知,SA的表面温度在90 s内由室温逐渐升高至约38 ℃,在随后90 s内缓慢升至39 ℃,之后基本保持稳定。改性后SA-PAN也表现出相似的温度变化趋势,说明SA-PAN具有良好的隔热性能。SA和SA-PAN的热学性能数据测试结果:SA、SA-PAN的热导率分别为0.045 1、0.055 2 W/(m·K),二者均处于较低水平,且改性后SA-PAN的热导率仅增加了0.010 1 W/(m·K)。其热扩散系数由0.196 1 mm2/s增至0.219 9 mm2/s,进一步表明其仍具有良好的隔热性能。
图2示出SA、SA-VTES和SA-PAN的SEM照片,SA、SA-VTES和SA-PAN均呈椭圆状形貌,且粒径分布较为均匀。改性后SA-VTES和SA-PAN的形貌与SA基本相似,粒径差异也不明显,说明接枝改性过程对SA的形貌影响较小。
图2
2.2 PAN/C-CNF 聚合物的结构与性能分析
图3示出可熔融 PAN 和 PAN/C-CNF 聚合物的FT-IR谱图,在C-CNF的FT-IR谱图中,1 650 cm-1处出现了C══O的伸缩振动峰,3 300~3 500 cm-1之间出现了—OH的伸缩振动峰,说明其表面富含羟基[24]。在PAN和PAN/C-CNF的FT-IR谱图中,2 930 cm-1处对应—CH的伸缩振动峰,1 450 cm-1 处对应—CH2的弯曲振动峰,2 244 cm-1处的特征吸收峰为PAN的特征峰,归属于C≡N的伸缩振动;1 731 cm-1处的C══O伸缩振动峰则为丙烯酸甲酯共聚单元的特征峰。此外,在PAN/C-CNF聚合物中的光谱图还观察到1 650 cm-1以及3300~3 500 cm-1范围内的特征峰,证实C-CNF已成功分散于PAN聚合物中,并形成了良好的氢键作用[25]。
图3
图3
C-CNF、可熔融 PAN 和 PAN/C-CNF聚合物的FT-IR谱图
Fig.3
FT-IR spectra of C-CNF,meltable PAN and PAN/C-CNF polymers
图4示出可熔融PAN和PAN/C-CNF聚合物的SEM照片。由图可知,PAN和PAN/C-CNF聚合物的粒径分布均较为均匀,其微观形貌均呈典型的六边形结构;C-CNF的加入并未显著改变PAN的形貌。
图4
图4
可熔融 PAN 和 PAN/C-CNF 聚合物的SEM照片
Fig.4
SEM images of meltable PAN and PAN/C-CNF polymers
表1示出可熔融 PAN 和 PAN/C-CNF 聚合物的分子量及熔体流动速率,PAN和PAN/C-CNF聚合物的数均分子量(Mn)分别约为25和28 ku,重均分子量(Mw)分别约为45和42 ku。二者的熔体流动速率均约为4.5 g/(10 min),表明其具有良好的可熔融加工性能。
表1 可熔融 PAN 和 PAN/C-CNF聚合物的分子量及熔体流动速率
Tab.1
| 样品 | Mn/ku | Mw/ku | PDI | 熔体流动速率/ (g·(10 min)-1) |
|---|---|---|---|---|
| PAN | 25 | 45 | 1.792 | 4.5 |
| PAN/C-CNF | 28 | 42 | 1.493 | 4.6 |
2.3 隔热纤维的结构与热学性能分析
图5示出熔融纺 PAN 基纤维的 FT-IR、XRD、DSC 和 TG 分析结果。由图可知,不同组分纤维的红外光谱差异并不显著,主要特征峰包括2 930 cm-1处的—CH 伸缩振动峰、1 450 cm-1处的—CH2弯曲振动峰、2 244 cm-1处的C≡N伸缩振动峰以及1 731 cm-1处的C══O伸缩振动峰。与 PAN 聚合物不同的是,2 240~2 000 cm-1范围内出现的多个吸收峰,主要是由于熔融加工后C≡N基团与相邻基团之间发生相互作用,吸收峰因此发生偏移。由于C-CNF和 SA-PAN的添加量较低,且受到熔融加工过程的影响,其特征峰被PAN基体掩盖,因此纤维的化学结构未发生明显变化。
图5
图5
不同 PCS 添加量对熔融纺 PAN 基纤维性能的影响
Fig.5
Influences of PCS contents on properties of PAN-based fibers. (a) FT-IR spectra; (b) XRD patterns; (c) DSC heating curves; (d) DSC cooling curves; (e) TG curves; (f) DTG curves
图5(b)表明所有熔融纺PAN基纤维均呈现典型的六方晶体结构,在2θ=17° 和2θ=30°处出现特征峰,其中宽而平缓的漫反射峰对应于PAN共聚物的无定形低有序区[26]。此外,C-CNF 的引入使纤维在2θ=22°~23°处出现额外的结晶峰,证实其作为异相成核剂发挥了作用,能够促进纤维的多重结晶,说明C-CNF与PAN之间具有良好的相互作用[27-28]。随着SA-PAN添加量的增加(含量从PCS1%增加到PCS7%),纤维结晶度由38.2% 逐渐降至22.0%,表明随着SA-PAN 的加入降低了纤维的结晶度。XRD图谱表明,PAN纤维(100)晶峰尖锐,结晶度高、取向单一、无定形区少,分子链运动受限,纤维刚性大。PC纤维(100)晶峰减弱、(002)晶峰增强,2θ=20°附近出现明显无定形宽化弥散峰,结晶度降低、取向分散,分子链形变能力更强,柔性与断裂伸长率更优。
由图5(c)、(d)可知,熔融纺PAN基纤维在约100 ℃处出现玻璃化转变温度(Tg)。在升温过程中,PAN纤维在90 ℃左右出现较宽的吸热峰,这与水分失重有关。可以看出,C-CNF在约130 ℃处存在1个较宽的吸热峰,而在加入C-CNF 后,PAN基纤维也在130 ℃处出现吸热峰,表明 PAN 基体与C-CNF之间形成了较强的相互作用。SA-PAN的加入使该峰强度逐渐减弱,这与结晶度下降的趋势一致。在降温过程中,PAN纤维在 170 ℃ 处出现明显的放热峰。C-CNF的引入使 PAN基纤维在70 ℃和110 ℃处出现额外的放热峰,进一步证实了其异相成核作用。随着SA-PAN添加量的增加,结晶放热峰的强度逐渐减弱,这与 XRD分析结果一致。
从图5(e)、(f)可见,PAN纤维存在3个明显的失重阶段[29]。第1阶段发生在90~130 ℃,主要归因于水分蒸发;第2阶段为更为显著的失重阶段,发生在280~430 ℃,主要是由于PAN基纤维发生环化和热分解,以及部分分子链分解所致。可以看出,C-CNF的加入使PAN基纤维的热分解温度提高到了约320 ℃。在480 ℃ 之后,PAN纤维的分解与炭化过程趋于平衡,仅发生轻微失重,进一步升高温度对其结构影响较小。然而,PC纤维在 480 ℃之后出现了明显而快速的失重现象,其高温下的分解和炭化过程更为剧烈,这与C-CNF的引入有关。C-CNF的纳米尺寸效应增强了PAN基纤维的结构孔隙性,使其在高温下更易发生分解,从而降低了残炭率。在加入1%和3% SA-PAN 后,PAN基纤维的残炭率分别由9.11%提高至16.41%和44.85%。同时,PAN基纤维的残炭率在高温下趋于稳定,变化不再明显,这表明SA-PAN的引入显著提升了PAN 基纤维的热稳定性和残炭率。
2.4 熔融纺 PAN 基隔热纤维的形貌分析
图6
图6
不同 PAN 基纤维截面的SEM照片
Fig.6
SEM image of sections of different PAN-based fibers
如图7所示,SA填料分布较为均匀,但填料添加比例增加至5%和7%后,PAN 基纤维中的SA已出现明显团聚。由此可见,SA-PAN的引入改变了纤维内部相结构和截面形貌,诱导形成了更多微孔。由图还可看到,PAN纤维和PC纤维表面相对光滑,外观较均匀;而加入SA-PAN后,PAN基纤维表面变得粗糙,并出现明显沟槽。随着SA-PAN添加量的增加,纤维表面粗糙度进一步增大。可以看到,当 SA-PAN添加量为1%、3% 和5%时,PAN 基纤维表面仍基本保持纤维应有的平整性;而当SA-PAN添加量增加至7%时,纤维表面粗糙度显著上升,沟槽现象更加严重,导致纤维牵伸困难、脆性增强,从而使其性能明显下降。
图7
图7
不同纤维样品表面SEM照片
Fig.7
SEM images of fibers surface of different fiber samples
2.5 隔热纤维的力学性能与隔热性能分析
由于性能差异,不同组成纤维可承受的牵伸倍数不同,对不同样品纤维进行力学性能的测试,结果如图8所示。从图中可以看出,熔融纺PAN基纤维的力学性能随着牵伸倍数的增大而提高,牵伸后纤维的拉伸强度显著增加;但当牵伸倍数达到极限后,若继续提高牵伸倍数,纤维的力学性能反而下降。
图8
图8
不同牵伸倍数下熔融纺 PAN 基纤维的断裂强度和断裂伸长率
Fig.8
Tensile strength and elongation at break of melt-spun PAN-based fibers at different drafting multiples
PAN纤维的最佳断裂强度为2.41 cN/dtex,PC纤维的为3.18 cN/dtex。与PAN 纤维相比,含0.1% C-CNF的PC纤维断裂强度提高了32.0%,且原丝断裂伸长率显著提高,与XRD分析结果一致,这表明 PAN基体与C-CNF之间形成了较强的相互作用,从而显著提升了熔融纺PAN基纤维的强度和柔韧性。PCS1% 纤维的最佳断裂强度为3.50 cN/dtex,较 PAN纤维提高了45.2%,说明少量SA-PAN的加入能够改善PAN基纤维的力学性能。这是因为PC纤维本身具有较好的柔韧性,而作为填料的SA-PAN仍具有一定的硬度和刚性,少量加入可对PAN基纤维的力学性能产生一定增强作用,同时 SA-PAN与PAN/C-CNF之间形成了较好的界面结合。受 SA-PAN 硬度和刚性的影响,随着SA-PAN 添加量的增加,纤维脆性逐渐增大,且由于SA-PAN在PAN基纤维中逐渐出现团聚的影响,力学性能逐步下降[30];但当SA-PAN添加量为5%时,纤维断裂强度仍可保持在约2.38 cN/dtex的较好水平,而当添加量达到7%时,其力学性能则下降至较差水平。
表2示出不同样品的热学性能。由表可知,PAN纤维和PC纤维的热导率分别为0.101 9、0.119 9 W/(m·K)。PC纤维的热导率的轻微升高,主要是由于C-CNF具有较高比表面积,从而在一定程度上提高了材料的热传导能力。加入1% SA-PAN后,PAN基纤维的热导率降低了29.4%;随着SA-PAN 添加量的增加,PCS纤维的热导率分别降低了 32.7%、37.2%和44.8%。此外,纤维的热扩散系数也随着SA-PAN添加量的增加而降低,结合SEM分析,SA-PAN的引入一方面可降低复合体系中固相热传导能力,另一方面也改变了纤维内部相结构和截面形貌,诱导形成更多微孔,使得熔融纺丝PAN基纤维的隔热性能显著提升。
表2 不同样品的热学性能
Tab.2
| 样品 | 热导率/(W·m-1·K-1) | 热扩散系数/(mm2·s-1) |
|---|---|---|
| PAN | 0.101 9 | 0.405 6 |
| PC | 0.119 9 | 0.477 2 |
| PCS1% | 0.084 6 | 0.357 1 |
| PCS3% | 0.080 7 | 0.350 8 |
| PCS5% | 0.075 3 | 0.339 4 |
| PCS7% | 0.066 2 | 0.263 6 |
3 结论
本文成功将聚丙烯腈(PAN)接枝到SiO2气凝胶(SA)表面,制备得到接枝率为20.4% 的SA-PAN填料。在乳液聚合阶段原位加入0.1%的羧基纤维素纳米纤维(C-CNF),制备了可熔融加工的 PAN/C-CNF聚合物,并将其与不同比例的SA-PAN 进行共混,随后通过熔融纺丝法成功制备出兼具优异隔热性能和力学性能的PAN基纤维。C-CNF 的引入显著改善了纤维的柔韧性和拉伸强度。纤维断裂强度提高了32%,由2.41 cN/dtex提升至3.18 cN/dtex。SA-PAN的加入有效降低了纤维热导率,并提升了其热稳定性和残炭率。纤维热导率由0.119 9 W/(m·K)降至0.075 3 W/(m·K),降幅为37.2%;当分别加入1%和3% SA-PAN 时,PAN基隔热纤维的残炭率由 9.11% 分别提高至16.41%和44.85%。此外,少量SA-PAN的加入还能够改善纤维的力学性能。当加入1% SA-PAN 时,PAN基纤维的断裂强度提高至3.50 cN/dtex;但随着SA-PAN添加量进一步增加,纤维的力学性能有所下降。需指出的是,当SA-PAN添加量为5%时,纤维断裂强度仍可保持在2.38 cN/dtex的较好水平。
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