Effect of polyurethane sizing agent on interface properties of carbon fiber reinforced polycarbonate composites

This work is aimed at investigating how molecule structure of polyurethanes (PUs) as sizing agents influence the interface properties of carbon fiber (CF) reinforced polycarbonate (PC) composites. Effects of four PUs as sizing agents for CF on the interlaminar shear strength (ILSS) of CF reinforced PC composites are investigated. It is found that the three PUs except PC–PU as sizing agents on oxidized CF (OCF) made the ILSS of their reinforced PC composites increase up to 62.9 MPa by more than 24.8%. The chemical interaction between PU sizing agents and CF are attributed to high reactivity of isocyanate, but carbonate groups on PC–PU may have a chain unzipping reaction due to active groups on the surface of OCF. The chemical interaction between PU sizing agents and PC are attributed to transesterification. As a result, PUs containing isocyanate or polyester groups are ideal sizing agents for CF reinforced PC composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47982.     

笼状硅氧烷/硅橡胶复合材料的非等温结晶性能

采用溶液共混法制备了笼状硅氧烷低聚物(POSS)/硅橡胶复合材料,用差示扫描量热仪在不同降温速率下研究了POSS/硅橡胶复合材料的非等温结晶性能,考察了POSS质量分数分别为5%(试样P5)、10%(试样P10)和30%(试样P30)时对复合材料非等温结晶参数和活化能的影响,并选用Ozawa及Ozawa-Avrami联合法对POSS/硅橡胶的非等温结晶性能进行了分析。结果表明,Ozawa-Avrami联合方法适合描述POSS/硅橡胶的非等温结晶现象;POSS/硅橡胶复合材料成核速率的大小依次为P5、P15和P30,生长速率则相反,而结晶速率大小依次为P30、P5和P15。     

笼状硅氧烷低聚物/聚合物复合材料的研究进展

介绍了笼状硅氧烷低聚物（POSS）的概念、分类及其合成工艺,综述了POSS／聚合物复合材料的制备方法及其在提高聚合物在热稳定性、阻燃性能、医学性能、光电性能、形状记忆及表面性能等方面的应用。     

Curing and thermal behaviors of inorganic–organic hybrid polyarylacetylene resins with polyhedral oligomeric octa(propargylaminophenyl)silsesquioxane

Polyhedral oligomeric octa(propargylaminophenyl)silsesquioxane (OPAPS) was used to prepare composite resins with prepolyarylacetylene (prePAA). The curing and thermal behaviors of the PAA/OPAPS composites were studied through Fourier‐transform infrared (FTIR), X‐ray diffraction (XRD), differential scanning calorimetric (DSC), thermogravimetric (TGA), and scanning electron microscopic (SEM) analysis and by direct observation. The morphologies of the PAA/OPAPS resins proved that there was good compatibility between PAA and OPAPS. FTIR analysis indicated formation of a conjugated diene and aromatic ring groups in the thermal curing process of the resins. DSC analysis implied that the addition of OPAPS to prePAA could decrease the exothermic heat and widen the temperature range in the curing process of prePAA. According to TGA analysis, a 10 wt % addition of OPAPS to PAA can maintain the thermal stability of PAA in N₂ atmosphere and somewhat enhance the thermal‐oxidative stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis,structure, and properties of high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane nanocomposites

The organic–inorganic hybrid nanocomposites from high‐impact polystyrene/octavinyl polyhedral oligomeric silsesquioxane (HIPS/POSS) containing various percentages of POSS were prepared by free radical polymerization and characterized by Fourier transform infrared spectroscopy (FTIR), ¹H‐NMR, thermal gravity analysis (TGA), X‐ray diffraction (XRD), and transmission electron microscopy (TEM). The octavinyl POSS has formed covalent bond connected PS‐POSS hybrid with polystyrene. POSS can well disperse in the composites at the composition of 0.5 and 1 wt%. The mechanical properties and thermostability of HIPS/POSS nanocomposites were significantly improved. The tensile strength, the izod impact strength, and the elongation at break of the nanocomposite containing 1 wt% of POSS was increased, respectively, by 15.73%, 75.62%, and 72.71% in comparison with pristine HIPS. The thermal decomposition temperature of HIPS/POSS (1 wt% of POSS) was 33°C higher than that of pristine HIPS. The HIPS/POSS nanocomposites showed great potential for applications in many fields, such as electric appliance and automotive trim. POLYM. COMPOS. 37:1049–1055, 2016. © 2014 Society of Plastics Engineers     

Compatibilization of polyhedral oligomeric silsesquioxane for polypropylene–titanium dioxide composites and effect of the processing temperature

Polyhedral oligomeric silsesquioxanes (POSSs), with inorganic cores, offer excellent mechanical properties and have external organic substituents. On the basis of their hybrid organic?inorganic characteristics, which allow for a tunable reaction or miscibility with various materials, in this study, we introduced a bifunctional POSS as a novel rigid compatibilizer for polypropylene (PP)–titanium dioxide (TiO₂) composites and evaluated its compatibilizing effects at different processing temperatures. The results show that the attached hydroxyl and isobutyl groups allowed for the reaction with TiO₂ and miscibility with the PP matrix. However, at lower processing temperatures, POSS existed in the form of solid particles, and its interfacial absorption was too poor for sufficient coverage of the TiO₂ surface; this resulted in a weak compatibilization effect on the PP–TiO₂ composite. When the processing temperature was increased to 240 °C, the solid POSS turned into a liquid and thus had strong mobility; this was favorable for the diffusion of TiO₂ onto the surface and the construction of a strong interfacial phase. Because the rigid characteristic of POSS made a positive contribution to the performances of the composites, the PP–TiO₂ composites prepared at higher processing temperatures exhibited better mechanical properties, with the maximum increases occurring in the compositions containing 5 wt % POSS. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44766     

Interface improvement of carbon fiber/methylphenylsilicone resin composites by fiber surface coating of polyhedral oligomeric silsesquioxanes

To enhance interfacial properties of carbon fibers (CFs)-reinforced methylphenylsilicone resin (MPSR) composites, we introduced an appropriate interface reinforced by trisilanolphenyl-polyhedral oligomeric silsesquioxanes (trisilanolphenyl-POSS) between CFs and MPSR with a liquid phase deposition strategy. Chemical bonds among silanol groups of trisilanolphenyl-POSS, hydroxyl-functionalized CF (CF–OH), and silanol end groups of MPSR in the coating were expected to be formed through condensation reaction during the prepared process. CFs with and without sizing treatment-reinforced MPSR composites were prepared by a compression molding method. X-ray photoelectron spectroscopy revealed that trisilanolphenyl-POSS particles enhanced the contents of fiber surface oxygen-containing groups and silicon-containing functional groups. Scanning electron microscopy and atomic force microscopy images showed that trisilanolphenyl-POSS nanoparticles have been introduced onto the fiber surface obviously and the surface roughness increased sharply. Dynamic contact angle analysis indicated that trisilanolphenyl-POSS-modified sizing agent could improve the fiber wettability and surface energy significantly. Short-beam bending test and impact toughness test results showed that the interlaminar shear strength and impact resistance of the sized CFs composites were enhanced greatly with increasing amplitudes of more than 35 and 27% in comparison with those of untreated CF composites, respectively. Cryo-fractured surface topographies of composites confirmed that interfacial adhesion between CFs and MPSR has been improved after sizing treatment. Meanwhile, the sizing treatment does not decrease single fiber tensile strength.     

The effect of a p‐phenylen‐bis‐maleamic acid grafted atactic polypropylene interface agent on the impact properties of iPP/mica composites

The present article is twofold. One of the purposes of this work lies in the study of the impact behavior of the polypropylene/mica system incorporating an interface modifier obtained from an industrial polymerization byproduct. The interface agent used was a p‐phenylen‐bis‐maleamic grafted atactic polypropylene (aPP‐pPBMA) obtained in our labs. The other objective is to obtain a mathematical model capable of forecasting the composite properties accurately. Consequently, this work has been undertaken by using a statistical Box‐Wilson experimental design in order to model the behavior of the composite system in terms of Charpy impact parameters. Two independent variables have been considered, the amount of mica particles and of interface agent. Impact strength, maximum force, and deformation were the dependent variables in the models. The existence of critical values in mica and interface agent optimizing the impact behavior is established. Additionally, an excellent correlation between the impact strength and the strength results coming from flexural and tensile tests is found. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44619.     

Effect of rare earth elements surface treatment on tensile properties of aramid fiber‐reinforced epoxy composites

Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of aramid fiber. Tensile properties of both the aramid/epoxy composites and single fibers were tested. The effects of RES concentration on tensile properties of aramid/epoxy composites were investigated in detail to explore an optimum amount of rare earth elements in solution for modifying aramid fiber. The fracture surface morphologies of tensile specimens were observed and analyzed with the aid of SEM. The experimental results show that rare earth treatment is superior to ECP grafting treatment in promoting interfacial adhesion between the aramid fiber and epoxy matrix. Meanwhile, the tensile strengths of single fibers were almost not affected by RES treatment. The optimum performance is obtained when the content of rare earth elements is 0.5 wt %. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1037–1041, 2004     

Simplification and application of single fiber fragmentation test on silylated polyester–glass fiber composites

Single fiber fragmentation test (SFFT) was used to investigate the interfacial adhesion in glass fiber‐unsaturated polyester composites. A simplified approach was developed for SFFT based on determination of the maximum number of fragments on the fiber at the end of the test. This approach does not involve length measurements and shortens the experiment time to a few minutes. By using a digital camera attached to the microscope, photographs of the coupon were taken during the test, and the number of fragments within the gauge length were counted later. This method allows quick, quantitative comparison of different fibers and matrices. The test samples were prepared by using commercial polyester resin and E‐glass fibers having different commercial sizings. SFFT results were in excellent agreement with the macromechanical test done on samples prepared with the same glass fiber and same polyester. The crack modes and debonding phenomena were examined from the microscopic images. Atomic force microscopic (AFM) images of the fiber were examined to get detailed topographic information about fiber surfaces. To improve interfacial adhesion, commercial unsaturated polyester was reacted with 3‐aminopropyltriethoxy silane via Michael Addition reaction on the maleate double bonds of the polyester. The resulting silylated polyester was characterized by H¹ NMR spectroscopy. The results of SFFT showed that the maximum numbers of fragments increased 23% on using silylated polyester. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal and mechanical properties of polyhedral oligomeric silsesquioxane (POSS)/polycarbonate composites

A series of composite materials were produced incorporating polyhedral oligomeric silsesquioxane (POSS) derivatives into polycarbonate (PC), by melt blending. Significant differences in compatibility were observed depending on the nano-scale filler's specific structure: trisilanol POSS molecules generally provided better compatibility with PC than fully-saturated cage structures, and phenyl-substituted POSS grades were shown to be more compatible with PC than fillers with other functional groups. Trisilanolphenyl-POSS/PC composites possess the best overall performance among the POSS materials tested. The high compatibility between the trisilanolphenyl-POSS and polycarbonate matrix results in generation of transparent samples up to 5 wt% POSS content. Slightly enhanced mechanical properties including tensile and dynamic mechanical modulus are observed with the increase of trisilanolphenyl-POSS loading at the cost of decreasing ductility of the nanocomposites. Importantly, upon orientation of the PC/POSS nanocomposite, crystallization of POSS within the oriented material results—this observation is consistent with a growing number of observations which suggest that ‘bottom-up’ formation of structures incorporating multiple POSS cages result from orientation of these nanocomposites, and that the hybrid organic-inorganic inclusions may be at the heart of observed nano-scale reinforcement.     

Effect of polyhedral oligomeric silsesquioxane on water sorption and surface property of Bis‐GMA/TEGDMa composites

2,2‐Bis[4‐(2‐hydroxy‐3‐methacryloxypropoxy)phenyl]propane (Bis‐GMA), one of the most important light‐curable dimethacrylate resins, is widely used as dental restorative material. However, one problem of Bis‐GMA is the high water sorption due to the hydrophilic hydroxyl (–OH) group, resulting in a short life in actual application. In this study, to overcome the drawback stated above, novel organic–inorganic dimethacrylate monomer containing polyhedral oligomeric silsesquioxanes (POSS), Bis‐GMA‐graft‐POSS, is synthesized via the nucleophilic addition reaction of isocyanate functionalized POSS (IPOSS) and pendent hydroxyl group of Bis‐GMA. Then the as‐synthesized Bis‐GMA‐graft‐POSS, of which hydroxyl group was substituted by hydrophobic POSS, is also introduced into the Bis‐GMA/TEGDMA matrix to prepare a series of methacrylate‐based hybrids for dental materials under visible light with camphorquinone and ethyl‐4N,N‐dimethy‐laminobenzoae (EDMAB) as initiator and coinitiator, respectively. Compared to Bis‐GMA/TEGDMA composites, water sorption of modified composites can be significantly reduced with the addition of Bis‐GMA‐graft‐POSS. Moreover, the Bis‐GMA/TEGDMA/POSS hybrids show hydrophobic surfaces, leading to much higher water contact angles than that of Bis‐GMA/TEGDMA composites. The morphology of hybrids containing POSS was furthermore studied by X‐ray diffraction (XRD) analysis and X‐ray photoelectron spectroscopy (XPS). The results show that POSS disperses in the matrix in noncrystalline form and tend to migrate to the surface of the modified composites that lead to the lower water sorption and higher water contact angles. These results are very useful for design of novel methacrylate monomers and clinical application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Crystallization behavior of ultrahigh‐molecular‐weight polyethylene/polyhedral oligomeric silsesquioxane nanocomposites prepared by ethylene in situ polymerization

A [3‐t‐Bu‐2‐O? C₆H₃CH?N(C₆F₅)]₂TiCl₂ catalyst (bis(phenoxyimine)titanium dichloride complex – FI catalyst) was immobilized on disilanolisobutyl polyhedral oligomeric silsesquioxane (OH‐POSS) to prepare ultrahigh molecular‐weight polyethylene (UHMWPE)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites during ethylene in situ polymerization. The dispersion state of POSS in the UHMWPE matrix was characterized by X‐ray diffraction measurements and transmission electron microscopy. It was shown that the OH‐POSS achieved uniformed dispersion in the UHMWPE matrix, although its polarity was unmatched. The isothermal and nonisothermal crystallization behavior of the nanocomposites was investigated by means of differential scanning calorimetry. The crystallization rate of the nanocomposites was enhanced because of the incorporation of POSS during the isothermal crystallization. POSS acted as a nucleus for the initial nucleation and the subsequent growth of the crystallites. For nonisothermal studies, POSS showed an increase in the crystallinity. The crystallization rate of the nanocomposites decreased because the presence of POSS hindered the crystal growth. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40847.     

Formation of a carbon fiber/polyhedral oligomeric silsesquioxane/carbon nanotube hybrid reinforcement and its effect on the interfacial properties of carbon fiber/epoxy composites

A carbon fiber/polyhedral oligomeric silsesquioxane/carbon nanotube (CF–POSS–CNT) hybrid reinforcement was prepared by grafting CNTs onto the carbon fiber surface using octaglycidyldimethylsilyl POSS as the linkage in an attempt to improve the interfacial properties between carbon fibers and an epoxy matrix. X-ray photoelectron spectroscopy, scanning electron microscopy, dynamic contact angle analysis and single fiber tensile testing were performed to characterize the hybrid reinforcements. Interlaminar shear strength (ILSS), impact toughness, dynamic mechanical analysis and force modulation atomic force microscopy were carried out to investigate the interfacial properties of the composites. Experimental results show that POSS and CNTs are grafted uniformly on the fiber surface and significantly increase the fiber surface roughness. The polar functional groups and surface energy of carbon fibers are obviously increased after the modification. Single fiber tensile testing results demonstrate that the functionalization does not lead to any discernable decrease in the fiber tensile strength. Mechanical property test results indicate the ILSS and impact toughness are enhanced. The storage modulus and service temperature increase by 11 GPa and 17 °C, respectively. POSS and CNTs effectively enhance the interfacial adhesion of the composites by improving resin wettability, increasing chemical bonding and mechanical interlocking.     

Preparation and properties of polyhedral oligomeric silsesquioxane/epoxy hybrid resins

Octaaminophenyl polyhedral oligomeric silsesquioxane (OAPS) was synthesized using three‐step method and used to modify o‐cresol‐novolac epoxy resin (ECN) for printed circuit board. The influence of OAPS on the reactivity and the final properties of the hybrid networks were evaluated. The intercrosslinking reaction between ECN and OAPS was confirmed by Fourier transform infrared spectra. The ECN/OAPS hybrids have better impact strength, higher electrical resistivity and thermal stability, lower water absorption than the unmodified ECN. The volume resistivity and surface resistivity of the hybrids increase by an order of magnitude or more compared to the neat epoxy. The thermal stability of the hybrids improves by the incorporation of OAPS; the initial decomposition temperature and char yield show an increasing tendency up to 4 wt% loading of OAPS. The hybrids exhibit higher storage modulus and glass transition temperature (T_g) than the neat epoxy. The T_g of the hybrids greatly improves up to 153.3°C at 3 wt% content, much higher than 119.4°C of the neat epoxy. POLYM. COMPOS., 34:1753–1760, 2013. © 2013 Society of Plastics Engineers     

Synthesis and properties of silicon‐containing arylacetylene resins with polyhedral oligomeric silsesquioxane

A series of silicon‐containing arylacetylene resins containing polyhedral oligomeric silsesquioxane (PS resins) were synthesized by the hydrosilylation reaction between poly(dimethylsilyleneethynylenephenyleneethynylene) (PMSEPE) and octakis(dimethylsiloxy)octasilsesquoixane ( ) in the presence of a platinum catalyst (Pt‐dvs). The chemical structures and properties of PS resins were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, rheological analysis, differential scanning calorimetry, dielectric measurement, thermogravimetric analysis, and scanning electron microscopy. The results show that PS resins can be crosslinked to form thermosets at temperatures less than 260°C. With the increment of , the dielectric constants of the thermosets gradually decrease from 2.91 to 2.73. The thermooxidative stabilities of PMSEPE thermosets are obviously improved with the incorporation of . POLYM. ENG. SCI., 55:316–321, 2015. © 2014 Society of Plastics Engineers     

Reaction of carbon fiber sizing and its influence on the interphase region of composites

What might happen with the interphase region of composite if the sizing agent cannot afford the attack of processing temperature and firstly reacted before its combination with the resin, is rarely reported. On the basis of this, herein, effects of sizing reaction on the interphase region of composite were investigated, as well as on the carbon fiber surface properties. It showed that the interfacial shear strength of carbon fiber/epoxy composite was improved after the sizing reaction. The interphase modulus was also increased with a thinner gradient distance. Further analysis indicated that the fiber surface roughness increased, the fiber wettability with the resin lowered, and the chemical reactions between sizing agent and resin reduced after 200°C/2 h treatment on carbon fiber. These results explained the change of the interphase region, which are meaningful for sizing optimization. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41917.     

Effects of the short‐fiber tip geometry and interphase properties on the interfacial debonding behavior of rubber matrix composites

An axisymmetric finite element model of a single fiber embedded in a rubber matrix was established. A cohesive zone model was used for the fiber–matrix interface because of the interfacial failure. The effect of the fiber tip shape on the interfacial debonding of short‐fiber‐reinforced rubber matrix sealing composites (SFRCs) was investigated; the shapes were flat, semi‐elliptical, hemispherical, and conoid, respectively. The initial strain of the interfacial debonding (ε₀) was obtained. We found that among the researched fiber tips, ε₀ of the SFRC reinforced with the hemispherical tip fiber appeared to be the maximum. The initial locations of interfacial debonding were also determined. The results show that the initial locations of the interfacial debonding moved from the edge to the center of the fiber tip when the ratio of the semimajor axis and semiminor axis of the semi‐elliptical fiber tip increased gradually. Further study on the effect of the interphase properties on ε₀ with the hemispherical fiber tip was conducted. The results indicate that an interphase thickness of 0.2 μm and an interphase elastic modulus of about 752 MPa were optimal for restraining the initiation of the interfacial debonding. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42774.     

Effects of interfacial adhesion on properties of polypropylene/Wollastonite composites

Wollastonite reinforced polypropylene (PP/CaSiO₃) composites were prepared by melt extrusion. A silane coupling agent and a maleic anhydride grafted PP (PP‐g‐MA) were used to increase the interfacial adhesion between the filler and the matrix. The increased adhesion observed by scanning electron microscopy (SEM) resulted in improved mechanical properties. A model was applied to describe the relationship between the interfacial adhesion and tensile properties of PP/CaSiO₃ composites. There is stronger interfacial adhesion between silane‐treated CaSiO₃ and polymer matrix containing PP‐g‐MA as a modifier. Results of dynamic mechanical thermal analysis (DMTA) showed that stronger interfacial adhesion led to higher storage modulus. The influence of CaSiO₃ particles on the crystallization of PP was studied by using differential scanning calorimetry (DSC). The introduction of CaSiO₃ particles does not affect the crystallization temperature and crystallinity of PP matrix significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal and morphological properties of high‐density polyethylene/ethylene–vinyl acetate copolymer composites with polyhedral oligomeric silsesquioxane nanostructure

The demand for improved properties of common polymers keeps increasing, and several new approaches have been investigated. In the study reported here, composites with a polymer matrix comprising a blend of high‐density polyethylene with ethylene–vinyl acetate copolymer (EVA), and with polyhedral oligomeric silsesquioxane (POSS) as a nanostructure, were processed and characterized in terms of their thermal and morphological properties. For the preparation of the composites, the concentrations of the blend components (0, 50 and 100 wt%) and of the POSS (0, 1 and 5 wt%) were varied. X‐ray diffraction results indicated that the presence of EVA in the composites led to the appearance of crystalline domains at lower POSS concentrations. Transmission and scanning electron microscopy showed that samples with 1 wt% of POSS had a homogeneous distribution in the polymer matrix with average dimensions of ca 150 nm. However, the formation of aggregates occurred in samples with 5 wt% of POSS. Differential scanning calorimetry and thermogravimetic analyses indicated that the POSS did not affect the melt and degradation temperatures of the polymer matrix. POSS underwent aggregation at higher concentrations during the composite processing, indicating a solubility limit of around 1 wt%. The presence of EVA in the composite favors POSS aggregation due to an increase in the polarity of the polymer matrix. Copyright © 2009 Society of Chemical Industry