Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers possess excellent dielectric,mechanical properties and heat resistance.However,the surface of PBO fibers is smooth and highly chemical inert,resulting in poor interfaci...Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers possess excellent dielectric,mechanical properties and heat resistance.However,the surface of PBO fibers is smooth and highly chemical inert,resulting in poor interfacial compatibility to polymer matrix,which severely limits its wider application in high-performance fiber-reinforced resin matrix composites.In this work,random copolymers(P(S-co-BCB-co-MMA))containing benzocyclobutene in the side-chain were synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization,which were then utilized to form dense random copolymer membrane on the surface of PBO fibers by thermally cross-linking at 250°C(PBO@P fibers).Four kinds of synthesized P(S-co-BCB-co-MMA)with different number-average molar mass(Mn)were well controlled and possessed narrow dispersity.When the Mnwas 32300,the surface roughness of PBO@P fibers was increased from 11 nm(PBO fibers)to 39 nm.In addition,PBO@P fibers presented the optimal interfacial compatibility with bisphenol A cyanate(BADCy)resins.And the single fiber pull-out strength of PBO@P fibers/BADCy micro-composites was 4.5 MPa,increasing by 45.2%in comparison with that of PBO fibers/BADCy micro-composites(3.1 MPa).Meantime,PBO@P fibers still retained excellent tensile strength(about 5.1 GPa).Overall,this work illustrates a simple and efficient surface functionalization method,which would provide a strong theoretical basis and technical support for controlling the surface structure&chemistry of inert substrates.展开更多
The high mechanical and thermal performance of poly p-phenylene- 2, 6 - benzobisoxazole （ PBO ） fiber provides great potential applications as reinforcement fibers for composites. A composite of PBO fiber and epoxy ...The high mechanical and thermal performance of poly p-phenylene- 2, 6 - benzobisoxazole （ PBO ） fiber provides great potential applications as reinforcement fibers for composites. A composite of PBO fiber and epoxy resin has excellent electrical insulation properties, therefore, it is considered to be the best choice for the reinforcement in high magnetic field coils for pulsed magnetic fields up to 100 T. However, poor adhesion between PBO fiber and matrix is found because of the chemically inactive and/or relatively smooth surface of the reinforcement fiber preventing efficient chemical bonding in the interface, which is a challenging issue to improve mechanical properties. Here, we report the surface modification of PBO fibers by ultraviolet （UV） irradiation, O2 and NH3 plasma, as well as acidic treatments. The interfacial adhesion strength values of all the treatments show the similar level as determined for aramid fibers by pull-out tests, a significant impact on fibermatrix-adhesion was not achieved. The surface free energy and roughness are increased for both sized and extracted fibers after plasma treatments together with maleic anhydride grafting. The sized fiber shows marginal improvement in adhesion strength and no change in fiber tensile strength because of the harrier effect of the finish. For the extracted fiber, different surface treatments either show no apparent effect or cause reduction in adhesion strength. Atomic force microscopy （AFM） topography analysis of the fracture surfaces proved adhesive failure at the fiber surface. The fiber surface roughness is increased and more surface flaws are induced, which could result in coarse interface structures when the treated fiber surface has no adequate wetting and functional groups. The adhesion failure is further confirmed by similar adhesion strength and compression shear strength values when the fiber was embedded in various epoxy resins with different temperature behavior. The tensile strength of fiber is sensitive to surface treatment conditions as revealed by a bimodal Weibull statistical distribution analysis. Considerable strength reduction occurred, particularly for cases of acidic and plasma treatments, while UV irradiation shows the better ability to retain fiber strength.展开更多
It was found that air dielectric barrier discharge(DBD) plasma contributed to the grafting of epoxy resin onto continuous PBO fiber surface. This air-plasma-grafting-epoxy method yielded a noticeable enhancement in th...It was found that air dielectric barrier discharge(DBD) plasma contributed to the grafting of epoxy resin onto continuous PBO fiber surface. This air-plasma-grafting-epoxy method yielded a noticeable enhancement in the interfacial adhesion between PBO fiber and thermoplastic matrix resin, with the interlaminar shear strength of the resulting composites increased by 66.7%. DSC and FTIR analyses were then used to study the curing behavior of epoxy coating on PBO fiber surface, deduce the possible grafting reactions and investigate the grafting mechanism. More importantly, TGA measurement showed that the grafting of epoxy onto PBO fiber had almost no effect on the composite heat resistance, and there was more thermoplastic matrix resin adhering to the fiber surface; the latter could also be clearly found in the SEM photos. Thereby, the air-plasma-grafting-epoxy treatment was proved to be an effective method for the improvement of continuous PBO fiber surface adhesive properties.展开更多
Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorin...Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorine/adamantane PBO precursor(pre FABPBO)as interfacial compatibilizer to prepare the corresponding PBO fibers/FABPBO/LCFE-BADCy wave-transparent laminated composites.LCFE could improve the order degree of BADCy cured network,in favor of enhancing the wave-transparent perfor-mance,mechanical properties,and intrinsic thermal conductivity.The dielectric constant and dielectric loss of PBO fibers/FABPBO/LCFE-BADCy composites are highly temperature(25–200℃)and frequency(10^(4)–10^(7) Hz and 8.2–12.4 GHz)stable with the value of 2.49 and 0.003 under 10^(6) Hz at 25℃,and the corresponding wave transmission efficiency is 95.0%,higher than that of 92.5%for PBO fibers/BADCy com-posites.The interlamellar shear strength and flexural strength are respectively 50.7 MPa and 682.5 MPa,38.1%and 16.2%higher than those of PBO fibers/BADCy composites.Besides,the volume resistivity,breakdown voltage,heat resistance index,glass transition temperature,flame retardant grade,and ul-timate oxygen index of PBO fibers/FABPBO/LCFE-BADCy composites are respectively 5.3×10^(15)Ωcm,29.75 kV/mm,217.2℃,245.7℃,V-1 grade,and 33.6%,expected to be performed as a new generation of“lightweight/loading/wave-transparent”electromagnetic window materials in advanced military weapons and civil communication base station.展开更多
In this work, the surface modification of poly （1, 4-phenylene-cis-benzobisoxazole） （PBO） fibers by O 2 /Ar coaxial atmospheric dielectric barrier discharge was investigated, as well as the interfacial adhesion pr...In this work, the surface modification of poly （1, 4-phenylene-cis-benzobisoxazole） （PBO） fibers by O 2 /Ar coaxial atmospheric dielectric barrier discharge was investigated, as well as the interfacial adhesion properties of modified PBO fibers/epoxy composites. The results indicated that the contact angle decreased remarkably from 84.7 to 63.5 after 3 min O 2 /Ar plasma treatment. SEM and AFM images showed that the surface of the treated PBO fibers became rather rough. In addition, XPS results suggested that the polar functional group （O=C- O） was introduced on the surface of the treated PBO fiber. The interfacial adhesion test showed that the interfacial shear strength （IFSS） and the interlaminar shear strength （ILSS） increased significantly by 63.54% and 130%, respectively. Moreover, the excellent tensile property of the PBO fibres was well preserved.展开更多
Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptio...Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptional dielectric properties.However,the weak interfacial bonding between these two materials hampers their full potential.In this study,we successfully addressed this limitation by enhancing the surface roughness of PBO fibers and introducing active sites through the insitu grafting of silica nanowires.The added silica acted as an interfacial anchor on the PBO fiber surface,significantly improving the bonding force between PBO and PTFE.PBO/PTFE wave-transparent laminated composites were fabricated using hot compression molding.The results demonstrate that the PBO(treated with insitu grown silica)/PTFE laminated composites exhibit superior interlaminar shear strength(ILSS),flexural strength,flexural modulus,and tensile modulus compared to the pristine PBO/PTFE laminated composites.Specifically,these properties are found to be 58.6%,32.9%,138.1%,and 25.35%higher,respectively.Additionally,these composites demonstrate low dielectric constant and dielectric loss.Most notably,they achieve a wave transmittance of 91.45%at 10 GHz,indicating significant potential for wide-range applications in next-generation advanced military weapons,such as“lightweight/high-strength/wavetransparent”electromagnetic window materials,as well as civilian communication base stations.展开更多
为缓解现代电子设备电磁辐射对人体健康的影响问题,开发质轻、易于精密加工的电磁屏蔽材料具有重要意义。文章采用去质子化诱导纳米纤维重构和湿法纺丝技术制备PBO凝胶纤维为载体,通过“银镜反应”将银纳米粒子负载于PBO凝胶纤维表面,...为缓解现代电子设备电磁辐射对人体健康的影响问题,开发质轻、易于精密加工的电磁屏蔽材料具有重要意义。文章采用去质子化诱导纳米纤维重构和湿法纺丝技术制备PBO凝胶纤维为载体,通过“银镜反应”将银纳米粒子负载于PBO凝胶纤维表面,并借助冷冻干燥技术,成功制备出具备多孔结构的复合气凝胶纤维。通过调节银纳米粒子的负载量,深入研究其对材料电磁屏蔽性能等方面的影响。研究结果显示,该复合材料在X波段(8.2~12.4 GHz)的电磁干扰(EMI)屏蔽效能值达到33 dB,且EMI SE A占总EMI值的60%,说明其以吸收屏蔽为主导,这基于气凝胶纤维的高比表面积和银纳米粒子的导电性对电磁波的吸收。展开更多
基金support and funding from National Scientific Research ProjectSpace Supporting Fund from China Aerospace Science and Industry Corporation(2019-HT-XG)+1 种基金Fundamental Research Funds for the Central Universities(310201911qd003)China Postdoctoral Science Foundation(2019M653735)。
文摘Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers possess excellent dielectric,mechanical properties and heat resistance.However,the surface of PBO fibers is smooth and highly chemical inert,resulting in poor interfacial compatibility to polymer matrix,which severely limits its wider application in high-performance fiber-reinforced resin matrix composites.In this work,random copolymers(P(S-co-BCB-co-MMA))containing benzocyclobutene in the side-chain were synthesized by reversible addition-fragmentation chain transfer(RAFT)polymerization,which were then utilized to form dense random copolymer membrane on the surface of PBO fibers by thermally cross-linking at 250°C(PBO@P fibers).Four kinds of synthesized P(S-co-BCB-co-MMA)with different number-average molar mass(Mn)were well controlled and possessed narrow dispersity.When the Mnwas 32300,the surface roughness of PBO@P fibers was increased from 11 nm(PBO fibers)to 39 nm.In addition,PBO@P fibers presented the optimal interfacial compatibility with bisphenol A cyanate(BADCy)resins.And the single fiber pull-out strength of PBO@P fibers/BADCy micro-composites was 4.5 MPa,increasing by 45.2%in comparison with that of PBO fibers/BADCy micro-composites(3.1 MPa).Meantime,PBO@P fibers still retained excellent tensile strength(about 5.1 GPa).Overall,this work illustrates a simple and efficient surface functionalization method,which would provide a strong theoretical basis and technical support for controlling the surface structure&chemistry of inert substrates.
文摘The high mechanical and thermal performance of poly p-phenylene- 2, 6 - benzobisoxazole （ PBO ） fiber provides great potential applications as reinforcement fibers for composites. A composite of PBO fiber and epoxy resin has excellent electrical insulation properties, therefore, it is considered to be the best choice for the reinforcement in high magnetic field coils for pulsed magnetic fields up to 100 T. However, poor adhesion between PBO fiber and matrix is found because of the chemically inactive and/or relatively smooth surface of the reinforcement fiber preventing efficient chemical bonding in the interface, which is a challenging issue to improve mechanical properties. Here, we report the surface modification of PBO fibers by ultraviolet （UV） irradiation, O2 and NH3 plasma, as well as acidic treatments. The interfacial adhesion strength values of all the treatments show the similar level as determined for aramid fibers by pull-out tests, a significant impact on fibermatrix-adhesion was not achieved. The surface free energy and roughness are increased for both sized and extracted fibers after plasma treatments together with maleic anhydride grafting. The sized fiber shows marginal improvement in adhesion strength and no change in fiber tensile strength because of the harrier effect of the finish. For the extracted fiber, different surface treatments either show no apparent effect or cause reduction in adhesion strength. Atomic force microscopy （AFM） topography analysis of the fracture surfaces proved adhesive failure at the fiber surface. The fiber surface roughness is increased and more surface flaws are induced, which could result in coarse interface structures when the treated fiber surface has no adequate wetting and functional groups. The adhesion failure is further confirmed by similar adhesion strength and compression shear strength values when the fiber was embedded in various epoxy resins with different temperature behavior. The tensile strength of fiber is sensitive to surface treatment conditions as revealed by a bimodal Weibull statistical distribution analysis. Considerable strength reduction occurred, particularly for cases of acidic and plasma treatments, while UV irradiation shows the better ability to retain fiber strength.
基金Project(L2014056)supported by the Liaoning Education Department,ChinaProject(201501089)supported by the Dr.Start-up Fund of Liaoning Province,China
文摘It was found that air dielectric barrier discharge(DBD) plasma contributed to the grafting of epoxy resin onto continuous PBO fiber surface. This air-plasma-grafting-epoxy method yielded a noticeable enhancement in the interfacial adhesion between PBO fiber and thermoplastic matrix resin, with the interlaminar shear strength of the resulting composites increased by 66.7%. DSC and FTIR analyses were then used to study the curing behavior of epoxy coating on PBO fiber surface, deduce the possible grafting reactions and investigate the grafting mechanism. More importantly, TGA measurement showed that the grafting of epoxy onto PBO fiber had almost no effect on the composite heat resistance, and there was more thermoplastic matrix resin adhering to the fiber surface; the latter could also be clearly found in the SEM photos. Thereby, the air-plasma-grafting-epoxy treatment was proved to be an effective method for the improvement of continuous PBO fiber surface adhesive properties.
基金The authors are grateful for the support and funding from National Scientific Research Project(Basis Strengthening Plan)State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202103).
文摘Bisphenol A dicyanate ester resins modified by fluorine-containing liquid crystal compound(LCFE)are applied as polymer matrix(LCFE-BADCy),poly(p-phenylene-2,6-benzobisoxazole)(PBO)fibers as rein-forcements,and fluorine/adamantane PBO precursor(pre FABPBO)as interfacial compatibilizer to prepare the corresponding PBO fibers/FABPBO/LCFE-BADCy wave-transparent laminated composites.LCFE could improve the order degree of BADCy cured network,in favor of enhancing the wave-transparent perfor-mance,mechanical properties,and intrinsic thermal conductivity.The dielectric constant and dielectric loss of PBO fibers/FABPBO/LCFE-BADCy composites are highly temperature(25–200℃)and frequency(10^(4)–10^(7) Hz and 8.2–12.4 GHz)stable with the value of 2.49 and 0.003 under 10^(6) Hz at 25℃,and the corresponding wave transmission efficiency is 95.0%,higher than that of 92.5%for PBO fibers/BADCy com-posites.The interlamellar shear strength and flexural strength are respectively 50.7 MPa and 682.5 MPa,38.1%and 16.2%higher than those of PBO fibers/BADCy composites.Besides,the volume resistivity,breakdown voltage,heat resistance index,glass transition temperature,flame retardant grade,and ul-timate oxygen index of PBO fibers/FABPBO/LCFE-BADCy composites are respectively 5.3×10^(15)Ωcm,29.75 kV/mm,217.2℃,245.7℃,V-1 grade,and 33.6%,expected to be performed as a new generation of“lightweight/loading/wave-transparent”electromagnetic window materials in advanced military weapons and civil communication base station.
基金supported by Shanghai Composite Company and partially by National Natural Science Foundation of China (No.10875146)
文摘In this work, the surface modification of poly （1, 4-phenylene-cis-benzobisoxazole） （PBO） fibers by O 2 /Ar coaxial atmospheric dielectric barrier discharge was investigated, as well as the interfacial adhesion properties of modified PBO fibers/epoxy composites. The results indicated that the contact angle decreased remarkably from 84.7 to 63.5 after 3 min O 2 /Ar plasma treatment. SEM and AFM images showed that the surface of the treated PBO fibers became rather rough. In addition, XPS results suggested that the polar functional group （O=C- O） was introduced on the surface of the treated PBO fiber. The interfacial adhesion test showed that the interfacial shear strength （IFSS） and the interlaminar shear strength （ILSS） increased significantly by 63.54% and 130%, respectively. Moreover, the excellent tensile property of the PBO fibres was well preserved.
基金supported by the National Natural Science Foundation of China(No.U21A2094)CASHIPS Director’s Fund(Nos.YZJJZX202015,YZJJ202304-CX,YZJJ2023QN36)+1 种基金Anhui Province Postdoctoral Researcher Research Project(No.E24F0D27)Central Government Guiding Local Government Science and Technology Development Special Fund Project(No.2022ZB09002).
文摘Poly(p-phenylene-2,6-benzobisoxazole)(PBO)fiber and polytetrafluoroethylene(PTFE)resin have been widely acknowledged as excellent wave-transparent materials for future high-frequency applications due to their exceptional dielectric properties.However,the weak interfacial bonding between these two materials hampers their full potential.In this study,we successfully addressed this limitation by enhancing the surface roughness of PBO fibers and introducing active sites through the insitu grafting of silica nanowires.The added silica acted as an interfacial anchor on the PBO fiber surface,significantly improving the bonding force between PBO and PTFE.PBO/PTFE wave-transparent laminated composites were fabricated using hot compression molding.The results demonstrate that the PBO(treated with insitu grown silica)/PTFE laminated composites exhibit superior interlaminar shear strength(ILSS),flexural strength,flexural modulus,and tensile modulus compared to the pristine PBO/PTFE laminated composites.Specifically,these properties are found to be 58.6%,32.9%,138.1%,and 25.35%higher,respectively.Additionally,these composites demonstrate low dielectric constant and dielectric loss.Most notably,they achieve a wave transmittance of 91.45%at 10 GHz,indicating significant potential for wide-range applications in next-generation advanced military weapons,such as“lightweight/high-strength/wavetransparent”electromagnetic window materials,as well as civilian communication base stations.
文摘为缓解现代电子设备电磁辐射对人体健康的影响问题,开发质轻、易于精密加工的电磁屏蔽材料具有重要意义。文章采用去质子化诱导纳米纤维重构和湿法纺丝技术制备PBO凝胶纤维为载体,通过“银镜反应”将银纳米粒子负载于PBO凝胶纤维表面,并借助冷冻干燥技术,成功制备出具备多孔结构的复合气凝胶纤维。通过调节银纳米粒子的负载量,深入研究其对材料电磁屏蔽性能等方面的影响。研究结果显示,该复合材料在X波段(8.2~12.4 GHz)的电磁干扰(EMI)屏蔽效能值达到33 dB,且EMI SE A占总EMI值的60%,说明其以吸收屏蔽为主导,这基于气凝胶纤维的高比表面积和银纳米粒子的导电性对电磁波的吸收。
