有机硅改性聚酰亚胺复合膜的抗原子氧性能研究

由端氨丙基聚二甲基硅氧烷（PDMS）、均苯四甲酸二酐（PMDA）和4,4’-二氨基二苯醚（ODA）在N,N’-二甲基乙酰胺（DMAc）中共聚,热亚胺化法制备有机硅改性聚酰亚胺复合膜。通过傅立叶变换红外吸收光谱仪（FTIR）、X射线光电子能谱（XPS）分析材料的化学结构,采用扫描电子显微镜（SEM）观察材料的表观形貌,利用地面原子氧（AO）模拟设备研究了该复合膜的抗原子氧性能。结果表明有机硅改性聚酰亚胺复合膜在AO累积通量达到2.06?020atom/cm2时,复合膜的AO剥蚀率可以达到6.69?0-25 cm3/atom,约是纯聚酰亚胺薄膜抗原子氧性能的4.5倍。     

二(p-氨基苯氧基)二甲基硅烷及聚酰亚胺

中国地质大学的胡应模等人以二甲基二氯硅烷和对氨基苯酚为原料,采用一步法得到二(p-氨基苯氧基)二甲基硅烷(SIDA);以此及4,4’-二氨基对苯醚为原料与均苯四羧酸二酐反应,合成得到有机硅氧烷聚酰亚胺;并分别采用热酰胺化与化学酰胺化制得了有机硅氧烷改性聚酰亚胺,并进行结构表征。     

有机硅改性聚ε-己内酯型聚氨酯弹性体的性能研究

以聚ε-己内酯(PCL-210N)、甲苯二异氰酸酯(TDI)和3,3′-二氯-4,4′-二氨基二苯基甲烷(MOCA)为原料,有机硅二醇为改性材料,通过预聚物法合成了一系列有机硅化学改性聚氨酯弹性体。分别用红外光谱测试、应力-应变测试、热重测试、差示扫描量热测试、扫描电镜、接触角以及动态力学测试等对其性能进行了研究。红外分析表明有机硅成功接入到聚氨酯分子中;扫描电镜表明有机硅向体系表面迁移并富集;改性聚氨酯弹性体的硬度、拉断伸长率、拉伸强度、100%和300%定伸模量及撕裂强度均有一定程度的提高,其吸水率由1.46%降至1.21%,接触角由78.69°升至101.97°,疏水性能提高;另外,其耐热性能也有所改善。     

2L-FCCL用聚酰亚胺复合膜的制备与性能

采用2,2′-双[4-(4-氨基苯氧基)苯基]丙烷(BAPP)、4,4′-二氨基二苯醚(ODA)和3,3′,4,4′-二苯酮四酸二酐(BTDA)合成BAPP/ODA/BTDA型聚酰亚胺(PI)的前驱体聚酰胺酸(PAA)溶液,将该溶液涂覆于3,3′,4,4′-联苯四甲酸二酐(BPDA)/ODA型PI基膜上,通过去溶剂和热亚胺化制备PI复合膜,将复合膜的热塑面与铜箔复合,热压制得二层挠性覆铜板(2L-FCCL)。研究了BAPP/ODA/BTDA型PI、BPDA/ODA型PI、PI复合膜及2L-FCCL的性能。结果表明:BAPP/ODA/BTDA型PI薄膜的玻璃化转变温度为238℃,耐热性能优异,PI复合膜在280℃,15MPa下与铜箔层压50~60min制得的2F-FCCL剥离强度大于0.8N/mm,且经360℃焊锡浴测试未分层、未起泡,耐热性能和剥离强度均满足工业要求。     

SiO_2-g-DOPO填充聚酰亚胺基杂化材料的制备及性能

使用4,4′-(六氟异丙烯)二酞酸酐(6FDA)、3,3′,4,4′-二苯酮四酸二酐(BTDA)、4,4′-二胺基二苯醚(ODA)、顺-5-降冰片烯-内型-2,3-二羧酸酐(NA)为反应单体,采用两步聚合法合成了系列聚酰亚胺树脂,并通过添加SiO_2-g-DOPO(二氧化硅-g-9, 10-二氢-9-氧杂-10-磷杂菲-10-氧化物)制备了聚酰亚胺基杂化材料,表征了杂化材料的耐热性能,研究了树脂结构及SiO_2-g-DOPO填充量对杂化材料性能的影响。结果表明:以6FDA/BTDA为基体,添加SiO_2-g-DOPO质量分数为10%时,所制备的杂化材料性能最佳,5%热失重温度为540℃,玻璃化转变温度为320℃,线烧蚀率为-4.200 0 mm/s,质量烧蚀率为0.008 2 g/s;与传统酚醛材料相比,杂化材料烧蚀隔热性能显著提高。     

端环氧苯基三(二甲基硅氧烷基)硅氧烷改性环氧树脂的性能研究

采用端环氧苯基三(二甲基硅氧烷基)硅氧烷对环氧树脂进行改性,制备了一系列有机硅改性环氧树脂,研究了端环氧苯基三(二甲基硅氧烷基)硅氧烷对环氧树脂力学性能、热学性能及原子氧剥蚀性能的影响。结果表明,改性树脂的综合性能随着端环氧苯基三(二甲基硅氧烷基)硅氧烷含量的增加而增强。当有机硅质量分数为30%时,有机硅改性环氧树脂的拉伸强度、弯曲强度和冲击强度与纯环氧树脂相比分别由48.2 MPa、100 MPa、12.7 k J/m~2提高至57.2 MPa、126 MPa、18.5 k J/m~2;质量损失率10%时的热失重温度提高了64℃;经过36 h的原子氧辐照后,质量损失率仅为纯环氧树脂的6.4%。     

（MMA／PMOE）共聚物交联改性研究

分别采用交联剂N,N′-亚甲基双丙烯酰胺(MBA)、二甲基丙烯酸乙二酯(EGDMA)对[甲基丙烯酸甲酯(MMA)/磷酸甲基丙烯酰氧乙基酯(PMOE)]共聚物进行改性,研究了改性材料的弯曲性能、维卡软化温度及吸水性。结果表明,(MMA/PMOE)共聚物经交联改性后材料的弯曲强度随着交联剂含量的增加而先提高后降低,维卡软化温度随着交联剂含量的增加而先升高后降低,以EGDMA为交联剂时材料的吸水率较低,EGDMA的加入并不影响(MMA/PMOE)共聚物作为特殊光学功能材料的应用。     

耐原子氧刻蚀有机硅改性环氧树脂的开发

通过端环氧苯基硅氧烷与双酚A型环氧树脂的共聚反应制得有机硅改性环氧树脂。研究了苯基硅氧烷用量对有机硅改性环氧树脂性能的影响。结果表明,有机硅改性环氧树脂固化物的冲击强度和耐原子氧剥蚀性能有明显提高;当改性剂苯基硅氧烷质量分数为30%时,有机硅改性环氧树脂的冲击强度由6.7k J/m~2提高到33.4 k J/m~2,原子氧辐照后质量损失降低为纯环氧树脂的20%。     

PP/MM复合材料的抗老化性能

将3,5-二-叔丁基-4-羟基苯基丙酸(AO)插层改性绢云母与聚丙烯(PP)共混挤出注塑制得PP/改性绢云母复合材料,通过老化试验箱进行人工老化实验,然后对不同老化时间材料力学性能、微观形貌及结晶性能进行表征,来研究不同含量AO对复合材料抗热氧老化过程中材料性能的影响。研究表明,AO的加入显著提升了材料的拉伸强度、弯曲强度和冲击强度,特别是在老化35 d后,试样弯曲强度不降反升,由25.1 MPa提高至34.0 MPa,同时改性绢云母的加入使复合材料的球晶完善度增加。     

三苯胺桥联的分散红衍生物的合成及光物理性质研究

设计和制备了一种新的有机光活性材料三苯胺桥联的分散红衍生物。该材料能很好地溶解于许多常见的有机溶剂。通过紫外可见吸收光谱、稳态和时间分辨荧光光谱、激光瞬态解析光谱、Z-扫描技术等方法研究了材料的光学和非线性反饱和吸收性能。与起始原料5-(N,N′-二苯氨基)苯基-1,3-二醛的荧光寿命(4.76ns)相比,三苯胺桥联的分散红衍生物的荧光寿命要短很多,为1.2ns,这个结果与接枝到5-(N,N′-二苯氨基)苯基上1,3-位的分散红的强吸电子作用密切相关。材料的双光子吸收截面为32GM(1GM=10-50cm4·s/photon·mol)。     

Preparation and Thermal Degradation of White Fluorinated Polyimide/TiO2 Composite Films with Strong Shielding Performance

A series of white fluorinated polyimide/TiO₂ composite films were prepared by a solution mixing method. They showed high tensile strength beyond 95.1MPa and excellent insulting property with surface and volume resistances exceeding 1.9 × 10¹¹Ω and 2.3 × 10¹² Ω cm, respectively, coupled with water absorptions below 1.1%, water contact angles up to 95.9 and whiteness beyond 58.5. It was found that their optical transparency decreased dramatically with the increasing doping of TiO₂. The thermal degradation of pure fluorinated polyimide (FPI) and representative polyimide/TiO₂ composite film with 5 wt% of TiO₂ (PI/TiO₂-5 wt%) was also studied.     

Atomic oxygen resistant coating from poly(tetramethyldisilylene‐co‐styrene)

A polydisilahydrocarbon, namely, poly(tetramethyldisilylene‐co‐styrene), synthesized from dimethyldichlorosilane and styrene in 1 : 0.5 mol ratio under dechlorination conditions was evaluated as an atomic oxygen (AO) resistant coating for polyimide film and C‐polyimide composite. Exposure of the polymer coating on a quartz plate to an AO fluence of 2.1 × 10²¹ atoms/cm² resulted in practically no mass loss, indicating the AO resistance of the polymer. Ten percent solution of the polymer in toluene was applied on aluminized Kapton® polyimide film (125 μm thick) to obtain a coating thickness of ～ 5 μm on the unaluminized surface. In a similar way, the coating was applied on a C‐polyimide composite. The coated and uncoated samples of Kapton® film and C‐polyimide composite were exposed to AO in a plasma barrel system. The uncoated aluminized Kapton® film (125 μm) lost 6.35 mg/cm² when exposed to AO fluence of 1.6 × 10²¹ atoms/cm² whereas the corresponding coated film lost only 0.14 mg/cm² even after exposure to AO fluence of 2.1 × 10²¹ atoms/cm². In the case of the C‐polyimide composite, the uncoated sample lost 63.64 mg/cm² on exposure to AO fluence of 1.8 × 10²¹ atoms/cm² whereas the coated one lost only 0.21 mg/cm² even after exposure to AO fluence of 2.1 × 10²¹ atoms/cm². SEM studies suggest that the coating offers good protection to the substrates. Formation of cracks on some portions of the coating was noticed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2368–2375, 2004     

Effect of atomic oxygen on corrosion and friction and wear behavior of polyimide composites

Thermosetting polyimide (TPI) composite with better wear resistance and lower friction was obtained with various functional fillers after a high–low temperature cycle test. Nevertheless, taking into consideration of harsh space condition, the friction and wear behavior of TPI composite were also explored after atomic oxygen (AO) irradiation. It reveals that TPI composite behaves excellent properties against AO mainly attributed to g-C₃N₄ with more negative electronegativity N than carbon atom. Moreover, the mechanism of friction and wear demonstrated that degradation caused by AO led to TPI composite surface with special “carpet-like” morphology and this resulted into lubrication failure, especially when temperature was increased from 200 °C to 350 °C. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48441.     

High oxygen barrier property of polyethylene composite films with bilayer polyvinyl alcohol coating for emergency foods in high-humidity environments

The limited oxygen barrier of polyethylene (PE) films has restricted their further application in food packaging, like emergency foods. Although its oxygen barrier property can be improved by applying a polyvinyl alcohol (PVA) coating, the application of PVA/PE composite films in high-humidity environments is still challenging. Hence, this study aimed to enhance the oxygen barrier properties of PVA/PE composite films in high-humidity environments. Specifically, PVA coatings were modified by the itaconic acid (IA) and magnesium-aluminum layered double hydroxides (LDH), and then applied to PE films as bilayer coating. Because of the unique bilayer coating on the PE surface, the oxygen barrier property of PVA/PE composite film (IA/LDH-p) in high-humidity environments has been further improved. The results confirmed that IA/LDH-p had an oxygen permeability coefficient of 1.92 ± 0.16 × 10⁻¹⁶ cm³ cm/(cm² s Pa) under a high-humidity environment test, 82.42% better than that of single-layer coating coated on PE surface. After being stored at RH 90% for 36 h, the tensile strength and elongation at break values of IA/LDH-p were 27.20 MPa and 919.63%, respectively. Overall, this obtained PVA/PE composite films showed great potential for application in emergency foods packaging, particularly in high-humidity environments.     

Thermal conductive performance of organosoluble polyimide/BN and polyimide/(BN + ALN) composite films fabricated by a solution‐cast method

Organosoluble polyimide (PI)/ceramic composite films with different BN or (BN + AlN) contents were under investigation for their thermal conductive performances. The chosen polyimide constituted by 4,4′‐oxydiphthalic dianhydride/2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluor opropane could be dissolved and cast into thin films at room temperature. The commercially available BN and AlN fillers up to a volume ratio of 0.6 were added to the polyimide and their thermal conductive performances were measured. BN powders needed a surface precoating treatment to avoid sedimentation. The dense and flexible PI/BN composite films, after a drying treatment at 200°C, showed high thermal conductivity of 2.3 W/m·K⁻¹ at a BN volume ratio of 0.6, as compared with 0.13 W/m·K⁻¹ for pristine polyimide. However, in the case of PI/(BN + AlN) composite films, thermal conductive performance degraded because the films became highly porous at the higher AlN content. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Carbon nanotube reinforced rigid‐rod polyimide

Multiwalled carbon nanotube/rigid‐rod polyimide composite films have been prepared by casting a solution of precursor polymer (polyamide acid) containing multiwalled carbon nanotubes (MWNTs) into thin films, followed by a thermal imidization treatment. The composite films were characterized by FTIR, TEM, DSC, TGA and TMA, and the film tensile properties were also examined. The presence of 1.0% MWNTs in the polymer matrix led to more than twofold increase in tensile strength of the rigid‐rod polyimide composite films and improved thermal stability, but reduced in thermal deformation. However, the tensile property did not show further increase when the film contained higher composition of MWNTs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Carbonization behavior of polyimide films with various chemical structures

Six kinds of polyimide films with different molecular structures were synthesized and carbonized up to 1100°C. The carbonization behavior of polyimides was followed by measuring the changes in weight, size, and electrical conductivity. Pyrolysis gases evolved on the way to carbonize up to 1000°C were analyzed by gas chromatography. All films showed appreciable shrinkage and became a black color above 500°C. No cracks and pores were observed on the films heated up to 1100°C, even under the scanning electron microscope. A large weight decrease of 35–50% was observed in a narrow temperature range from 500 to 650°C, which seemed to be due to the departure of CO groups as either CO or CO₂. An additional weight decrease occurred gradually above 800°C, due to N₂ departure. A remarkable increase of electrical conductivity along the film surface, more than 2 orders, was observed with the increase in heat-treatment temperature. The polyimide film with a flat molecular structure (PMDA/PPD) gave the highest conductivity: 3.7 × 10²S/cm.     

Polyhedral oligomeric silsesquioxane polyimide nanocomposites for color filters and flexible conductive films

Color filters and conductive films are widely used in spacecraft, while the lack of lightweight, flexibility, and atomic oxygen (AO) durability confine their potential applications in low earth orbit. In this study, a clear poly(amic acid) with an empirical 20 wt% polyhedral oligomeric silsesquioxane (POSS) solid content is designed for transparency and AO durability. Red, green, blue, and yellow dyes are reinforced with small amounts of 1–5 wt% in POSS polyimides for color filters. A silver nanowire network film is infiltrated onto the POSS polyimide for conductive film. Erosion depth upon hyperthermal AO exposure, surface morphology, surface chemistry, optical transparency, and conductivity have been systematically investigated. The erosion yields of all 20 wt% POSS polyimides decrease by an order of magnitude when subjected to 2.32 ± 0.05 and 2.39 ± 0.06 × 10²⁰ atoms cm⁻² AO fluences, as passivating SiO_x networks are formed on film surface. The small-amount dye additives into polyimides do not introduce obvious changes in AO durability and surface chemistry. The silver nanowire infiltrated POSS polyimide film shows a 65.7% transmittance at 550 nm and a sheet resistance of 8.50 ± 0.36 Ohm square⁻¹. This study reveals promising attempts of POSS-polyimide-based color filters and flexible conductive films for potential space applications.     

Synthesis,structure and properties of polyimide–silica hybrid composites based on biphenyltetracarboxylic dianhydride

A simple and efficient way of synthesizing nanocomposite films using a dispersion technique is reported, with the resulting films having improved mechanical and thermal properties. Nano‐SiO₂ was used in a biphenyltetracarboxylic dianhydride‐based poly(amic acid) precursor and found to be dispersed up to 7 wt% without any additives. The composites were cast to make 10 µm solid films to establish structure and property relationships between liquid and solid film. The structures of the liquid composite materials were studied using NMR and Fourier transform infrared spectroscopy. Solid film properties such as tensile strength, contact angles and thermal behaviour were evaluated for comparison. The properties of the composite films were found to be enhanced compared to polyimide film itself. Atomic force microscopy and macroscale mechanical measurements showed that composite films with more dipolar bonding interactions have higher elastic moduli and are more deformable. They yield higher adhesion energies, and therefore composite coatings offer greater adhesion. There was a limitation in the film formation beyond 5 wt% of silica. Copyright © 2011 Society of Chemical Industry     

Residual stress effect on degradation of polyimide under simulated hypervelocity space debris and atomic oxygen

Polyimides are used as the outer layer of thermal control insulation blankets covering most of the external spacecraft surfaces that are exposed to space environment. The combined effect of ground simulated hypervelocity space debris impacts and atomic oxygen (AO) on the fracture of polyimide films was studied. A laser-driven flyer system was used to accelerate aluminum flyers to impact velocities of up to 3 km/s. The impacted films were exposed to an RF plasma source, which was used to simulate the effect of AO in the low Earth orbit. Scanning electron microscopy and atomic force microscopy were used to characterize the fracture and surface morphology. When exposed to oxygen RF plasma, the impacted polyimide film revealed a large increase in the erosion rate, the damage being characterized mainly by the formation of new holes. This effect is explained by the formation of residual stresses due to the impact and enhancement of oxygen diffusivity and accumulation. A complementary experiment, in which a stressed polyimide was exposed to RF plasma, supports this model. This study demonstrates a synergistic effect of the space environment components on polymers' degradation, which is essential for understanding the potential hazards of ultrahigh velocity impacts and AO erosion for completing a successful spacecraft mission.