Effects of sizing materials on the properties of carbon fiber‐reinforced polyamide 6,6 composites

This article aims to study the effect of the sizing materials type on the mechanical, thermal, and morphological properties of carbon fiber (CF)‐reinforced polyamide 6,6 (PA 6,6) composites. For this purpose, unsized CF and sized CFs were used. Thermogravimetric analysis was performed, and it has been found that certain amounts of polyurethane (PU) and PA sizing agents decompose during processing. The effects of sizing agent type on the mechanical and thermomechanical properties of all the composites were investigated using tensile, Izod impact strength test, and dynamic mechanical analysis. Tensile strength values of sized CF‐reinforced composites were higher than that of unsized CF‐reinforced composites. PA and polyurethane sized CF‐reinforced composites exhibited the highest impact strength values among the other sized CF‐reinforced composites. PU and PA sized CF‐reinforced composites denoted higher storage modulus and better interfacial adhesion values among the other sizing materials. Scanning electron microscope studies indicated that CFs which were sized with PU and PA have better interfacial bonding with PA 6,6 matrix among the sized CFs. All the results confirmed that PA and PU were suitable for CF's sizing materials to be used for PA 6,6 matrix. POLYM. COMPOS., 34:1583–1590, 2013. © 2013 Society of Plastics Engineers     

Investigation of structure and mechanical properties of toughened poly(l‐lactide)/thermoplastic poly(ester urethane) blends

In this study, poly(l ‐lactide) (PLA) is melt‐blended with thermoplastic polyurethane (TPU) to modify the brittleness of PLA. An aliphatic ester‐based TPU was selected in order to have an ester sensitivity for degradation and an inherent biocompatibility. Using this compatible TPU, there was no need to apply problematic compatibilizers, so the main positive properties of PLA such as biocompatibility and degradability were not challenged. The detected microstructure of PLA/TPU blends showed that when the TPU content was lower than 25 wt %, the structure appeared as sea‐islands, but when the TPU content was increased, the morphology was converted to a cocontinuous microstructure. A higher interfacial surface area in the blend with 25 wt % TPU (PLA25) resulted in a higher toughness and abrasion resistance. The various analyses confirmed interactions and successful coupling of two phases and confirmed that melt‐blending of PLA with the aliphatic ester‐based TPU is a convenient, cost‐effective, and efficient method to conquer the brittleness of PLA. The prepared blends are general‐purpose plastics, but PLA25 showed an optimum mechanical strength, toughness, and biocompatibility suitable for a wide range of applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43104.     

Temperature effect on graphene‐filled interface between glass–carbon hybrid fibers and epoxy resin characterized by fiber‐bundle pull‐out test

The overall mechanical performance of glass–carbon hybrid fibers reinforced epoxy composites depends heavily upon fiber–matrix interfacial properties and the service temperatures. Fiber‐bundle pull‐out tests of glass (GF) and/or carbon fiber (CF) reinforced epoxy composites were carried out at room and elevated temperatures. Graphene nanoplatelets were added in the interfacial region to investigate their influence on the interfacial shear strength (IFSS). Results show that IFSS of specimens with fiber‐bundle number ratio of GF:CF = 1:2 is the largest among the hybrid composites, and a positive hybridization effect is found at elevated temperatures. IFSS of all the specimens decreases with the increasing of test temperatures, while the toughness shows a contrary tendency. As verified by scanning electron microscopy observations, graphene nanoplatelets on fiber surface could enhance the IFSS of pure glass/carbon and hybrid fibers reinforced epoxy composites at higher temperatures significantly. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46263.     

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.     

Morphologies and mechanical properties of polylactide/thermoplastic polyurethane elastomer blends

To explore a potential method for improving the toughness of a polylactide (PLA), we used a thermoplastic polyurethane (TPU) elastomer with a high strength and toughness and biocompatibility to prepare PLA/TPU blends suitable for a wide range of applications of PLA as general‐purpose plastics. The structure and properties of the PLA/TPU blends were studied in terms of the mechanical and morphological properties. The results indicate that an obvious yield and neck formation was observed for the PLA/TPU blends; this indicated the transition of PLA from brittle fracture to ductile fracture. The elongation at break and notched impact strength for the PLA/20 wt %TPU blend reached 350% and 25 KJ/m², respectively, without an obvious drop in the tensile strength. The blends were partially miscible systems because of the hydrogen bonding between the molecules of PLA and TPU. Spherical particles of TPU dispersed homogeneously in the PLA matrix, and the fracture surface presented much roughness. With increasing TPU content, the blends exhibited increasing tough failure. The J‐integral value of the PLA/TPU blend was much higher than that of the neat PLA; this indicated that the toughened blends had increasing crack initiation resistance and crack propagation resistance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical and thermal properties of wood fibers reinforced poly(lactic acid)/thermoplasticized starch composites

Thermoplasticized starch (TPS) filled poly(lactic acid) (PLA) blends are usually found to have low mechanical properties due to poor properties of TPS and inadequate adhesion between the TPS and PLA. The purpose of this study was to investigate the reinforcing effect of wood fibers (WF) on the mechanical properties of TPS/PLA blends. In order to improve the compatibility of wood with TPS/PLA blends, maleic anhydride grafted PLA (MA‐g‐PLA) copolymer was synthesized and used. TPS, TPS/PLA blends, and WF reinforced TPS/PLA composites were prepared by twin‐screw extrusion and injection molded. Scanning electron microscope and crystallinity studies indicated thermoplasticity in starch. WF at two different weight proportions, that is, 20% and 40% with respect to TPS content were taken and MA‐g‐PLA at 10% to the total weight was chosen to study the effect on mechanical properties. At 20% WF and 10% MA‐g‐PLA, the tensile strength exhibited 86% improvement and flexural strength exhibited about 106% improvement over TPS/PLA blends. Increasing WF content to 40% further enhanced tensile strength by 128% and flexural strength by 180% with respect to TPS/PLA blends. Thermal behavior of blends and composites was analyzed using dynamic mechanical analysis and thermogravimetric analysis. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46118.     

Iron phthalocyanine coatings on the surface of carbon fibers and their improved interfacial interactions with poly(arylene ether)nitrile

Riveted carbon fibers (CFs) were fabricated via in situ thermopolymerization. Iron phthalocyanine was like rivets distributed on the surface of the acidulated CFs. The rivets were characterized by scanning electron microscopy (SEM) and distributed uniformly on the surface of the CFs with a uniform microsphere size of 120 nm. Next, the pristine and riveted CFs were used to prepare fiber‐reinforced poly(arylene ether)nitrile (PEN)‐based composites with a hot‐press molding technique. The creep behaviors of PEN on the pristine and riveted CFs were investigated by dynamic rheological measurements. Among the samples, the viscosities changed with the frequency, and the stress relaxation and Cole–Cole plots are presented and discussed in detail. These results indicated better interlocking between the PEN chains and the rivets on the surface of the CFs. The dynamic mechanical properties of the composites were examined in three‐point bending mode with a dynamic mechanical analyzer. The results indicate that the reduction of the tan δ peak height may have been due to the improved interfacial adhesion between the CFs and PEN. Additionally, the interfacial morphologies of the CF‐reinforced PEN composites were monitored; this also confirmed the improved adhesion between the PEN chains and the riveted CFs in comparison with that of the pristine CFs. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46466.     

Interfacial shear strength in carbon fiber‐reinforced poly(phthalazinone ether ketone) composites

We studied interfacial shear strength (IFSS) in carbon fiber (CF)‐reinforced poly (phthalazinone ether ketone) (PPEK) composites system, with emphasis on the influence of forming temperature of composite and sizing agent on CFs. To obtain apparent IFSS of CF‐reinforced PPEK composites shaped at various forming temperatures ranged from 20 up to 370°C, microbond test was carried out at single‐fiber composites. Results of microbond test showed that apparent IFSS was directly proportional to the difference between the matrix solidification temperature (forming temperature) and the test temperature and approximately 80% of the apparent IFSS in CF/PPEK composite system was attributed to residual radial compressive stress at the fiber/matrix interface. By sizing CF with sizing agent, the wettability of the fiber by the matrix was improved and the final apparent IFSS was also improved. POLYM. COMPOS., 34:1921–1926, 2013. © 2013 Society of Plastics Engineers     

Effects of thermoplastic polyurethane on the properties of poly(lactic acid)/organo‐montmorillonite nanocomposites based on novel vane extruder

Polylactic acid (PLA)/organo‐montmorillonite (OMMT) nanocomposites toughened with thermoplastic polyurethane (TPU) were prepared by melt‐compounding on a novel vane extruder (VE), which generates global dynamic elongational flow. In this work, the mechanical properties of the PLA/TPU/OMMT nanocomposites were evaluated by tensile, flexural, and tensile tests. The wide‐angle X‐ray diffraction and transmission electron microscopy results show that PLA/TPU/OMMT nanocomposites had clear intercalation and/or exfoliation structures. Moreover, the particles morphology of nanocomposites with the addition of TPU was investigated using high‐resolution scanning electronic microscopy. The results indicate that the spherical TPU particles dispersed in the PLA matrix, and the uniformity decreased with increasing TPU content (≤30%). Interestingly, there existed abundant filaments among amount of TPU droplets in composites with 30 and 40 wt% TPU. Furthermore, the thermal properties of the nanocomposites were examined with differential scanning calorimeter and dynamic mechanical analysis. The elongation at break and impact strength of the PLA/OMMT nanocomposites were increased significantly after addition of TPU. Specially, Elongation at break increased by 30 times, and notched impact strength improved 15 times when TPU loading was 40 wt%, compared with the neat PLA. Overall, the modified PLA nanocomposites can have greater application as a biodegradable material with enhanced mechanical properties. POLYM. ENG. SCI., 54:2292–2300, 2014. © 2013 Society of Plastics Engineers     

Effect of curauá fiber content on the properties of poly(hydroxybutyrate‐co‐valerate) composites

Poly(hydroxybutyrate‐co‐valerate) (PHBV), a biodegradable polymer produced from a renewable microbiological source, was reinforced with varying amounts of curauá fibers (CFs). The composites were produced using a twin‐screw extrusion and injection process. Scanning electron microscopy showed poor adhesion between the matrix and fiber; however, mechanical testing showed that the addition of the fiber improved the mechanical properties. Composites with 20 and 30 wt% CF displayed the best properties; however, because of the difficulties in processing composites with a CF content of 30 wt%, it was concluded that the ideal content of CF was 20 wt%. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Improving the interfacial and flexural properties of carbon fiber–epoxy composites via the grafting of a hyperbranched aromatic polyamide onto a carbon fiber surface on the basis of solution polymerization

Hyperbranched aromatic polyamide (HBP) was grafted successfully onto carbon fibers (CFs) on the basis of solution polymerization to enhance the interfacial adhesion strength of CF-reinforced epoxy resin composites. The microstructure and interfacial properties of the CFs before and after decoration were researched. The results indicate that HBP was deposited uniformly onto the CFs with γ-aminopropyl triethoxysilane as the bridging agent. The active groups, roughness, and surface energy of the modified fiber [hyperbranched aromatic polyamide grafted carbon fiber (CF–HBP)] increased visibly in comparison with those of the untreated CFs. The CF–HBP composites revealed simultaneous remarkable enhancements (65.3, 34.3, and 84.8%) in their interfacial shear strength, flexural strength, and modulus, respectively; this was attributed to the improvement in the fiber–epoxy interface through enhanced chemical interactions, mechanical interlocking, and wettability. These agreed with the scanning electron microscopy observations from the fracture surface morphologies of the composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47232.     

Biodegradable composites of poly(butylene succinate‐co‐butylene adipate) reinforced by poly(lactic acid) fibers

Biodegradable composites of poly(butylene succinate‐co‐butylene adipate) (PBSA) reinforced by poly(lactic acid) (PLA) fibers were developed by hot compression and characterized by Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analyzer, and tensile testing. The results show that PBSA and PLA are immiscible, but their interface can be improved by processing conditions. In particular, their interface and the resulting mechanical properties strongly depend on processing temperature. When the temperature is below 120 °C, the bound between PBSA and PLA fiber is weak, which results in lower tensile modulus and strength. When the processing temperature is higher (greater than 160 °C), the relaxation of polymer chain destroyed the molecular orientation microstructure of the PLA fiber, which results in weakening mechanical properties of the fiber then weakening reinforcement function. Both tensile modulus and strength of the composites increased significantly, in particular for the materials reinforced by long fiber. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43530.     

Fiber–matrix interactions in aramid‐short‐fiber‐reinforced thermoplastic polyurethane composites

The mechanical and dynamic mechanical properties of thermoplastic polyurethane (TPU) elastomers reinforced with two types of aramid short fibers, m‐aramid (Teijin‐Conex) and copoly(p‐aramid) (Technora), were investigated in this study with respect to the fiber loading. In general, both types of composites exhibited very similar stress–strain behaviors, except that Technora–TPU was stronger than Conex–TPU. This was primarily due to the intrinsic strength of the reinforcing fibers. Both types of fibers reinforced TPU effectively without any surface treatment. This could be attributed to good fiber–matrix interactions, which were revealed by the broadening of the tan δ peak in dynamic mechanical analysis. Furthermore, the morphologies of cryogenically fractured surfaces of the composites and extracted fibers, investigated with scanning electron microscopy, revealed possible polar–polar interactions between the aramid fibers and TPU matrices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1059–1067, 2003     

Effects of alkali and alkali/silane treatments of corn fibers on mechanical and thermal properties of its composites with polylactic acid

Different chemically modified (including treatments with alkali alone and a combination of alkali and silane coupling agent) corn fibers (CFs) have been used as reinforcements in polylactic acid (PLA) matrix to improve the mechanical and thermal properties of the CF/PLA composites. A comparative study has been made to find out how the two treatments affect the mechanical and thermal properties such as tensile, flexural, and impact strengths and glass transition temperature (T_g), crystallinity, and heat deflection temperature (HDT) of the CF/PLA composites. Scanning electron microscopy analyses have been conducted to evaluate the fiber–matrix adhesion. It has been observed that the treatment with a combination of alkali and silane is more efficient in strengthening fiber–matrix bonding, and thus more significantly improving the tensile and flexural strengths, crystallinity, T_g, and HDT of the CF/PLA composites than the treatment with alkali alone. However, alkali treatment produces the optimal impact strength. Mechanisms have been proposed to interpret the observed changes in mechanical and thermal properties as a result of fiber treatments. It is inferred that the surface treatment of CFs with a combination of alkali and silane may also be applied in other CF–polymer composite systems. POLYM. COMPOS., 37:3499–3507, 2016. © 2015 Society of Plastics Engineers     

Preparation and properties of L‐lactide‐grafted sisal fiber–reinforced poly(lactic acid) composites

Pretreatment of the sisal fiber (SF) grafting with L‐lactide (LA) monomer via a ring‐opening polymerization catalyzed by a Sn(II)‐based catalyst was performed to improve the interfacial adhesion between SF and poly (lactic acid) (PLA). Biocomposites from LA‐grafted SF (SF‐g‐LA) and PLA were prepared by compression molding with fiber weight fraction of 10, 20, 30, and 40%, and then were investigated in contrast with alkali‐treated sisal fiber (ASF) reinforced PLA composites and untreated SF reinforced PLA composites. PLA composites reinforced by half‐and‐half SF‐g‐LA/untreated SF (half SF‐g‐LA) were prepared and studied as well, considering the disadvantages of SF‐g‐LA. The results showed that both the tensile properties and flexural properties of the SF‐g‐LA reinforced PLA composites were improved noticeably as the introduction of SF‐g‐LA, compared with pure PLA, untreated SF reinforced PLA composites and ASF reinforced PLA composites. The mechanical properties of the half SF‐g‐LA reinforced PLA composites were not worse, even better in some aspects, than the SF‐g‐LA reinforced PLA composites. Fourier transform infrared analysis and differential scanning calorimetry analysis exhibited that both the chemical composition and crystal structure of the SFs changed after LA grafting. In addition, the fracture surface morphology of the composites was studied by scanning electron microscopy. The morphological studies demonstrated that a better adhesion between LA‐grafted SF and PLA matrix was achieved. POLYM. COMPOS., 37:802–809, 2016. © 2014 Society of Plastics Engineers     

Enhanced fracture toughness of nanostructured carbon‐fiber reinforced poly(urethane‐isocyanurate) composites at low concentrations

Carbon fiber reinforced poly(urethane‐isocyanurate)‐nanosilica composites CF‐(PUI‐NS) were manufactured by means of the vacuum‐assisted resin transfer moulding technique (VARTM) at very low NS concentrations (0–4 wt%). The high strain to failure of the PUI matrix (>7%) affected tensile tests by CF reorientation. Both the tensile strength and strain to failure were highly dependent on its kinematics. CF(PUI‐NS) caused an increase of the static toughness with a maximum improvement of tensile strain to failure and modulus of +28.8% and +39% at 1 wt% and 2 wt% of NS, respectively. The interlaminar shear strength (G_IC) of the composites showed both a deterioration of ?12.9% and an improvement of +9.9% for NS concentrations of 1 wt% and 4 wt%, respectively. Regardless of the G_IC value, all of the composites prepared with NS presented secondary maxima of the force versus displacement plots, indicating a substantial arrest of the crack propagation velocity after delamination started. Fractographic analysis revealed several features, such as fiber pull‐out, bridging as well as river patterns whereas the composites prepared with NS behaved in a more ductile fashion due to the presence of river patterns and a reduced fiber pull‐out. POLYM. ENG. SCI., 58:1241–1250, 2018. © 2017 Society of Plastics Engineers     

Effects of halloysite nanotubes on the performance of plasticized poly(lactic acid)‐based composites

The objective of this study is processing and characterization of Halloysite nanotube (HNT)/poly(lactic acid) (PLA) nanocomposites. As HNT filler, a domestic source was used (ESAN HNT). The results obtained from this HNT were compared with a well‐known reference HNT (Nanoclay HNT). To achieve the desired physical properties and clay dispersion, composites were compounded via direct melt mixing in a laboratory twin‐screw compounder. However, the constituents were observed to be incompatible without a compatibilizer. To improve the flexibility of nanocomposites and provide compatibilization between PLA and HNT, two types of blends were prepared: PLA plasticized with poly(ethylene glycol) (PEG) denoted as P‐PLA and PLA toughened with a thermoplastic polyurethane (TPU) denoted as T‐PLA. Despite the limited improvement in the P‐PLA blends, TPU addition improved the flexibility of PLA/HNT without deteriorating the tensile strength in a great manner. This was attributed to the relatively better compatibilization effect of TPU and the role of nanotubes acting as bridges between the TPU and PLA phases. POLYM. COMPOS., 37:3134–3148, 2016. © 2015 Society of Plastics Engineers     

Preparation and mechanical characterization of chicken feather/PLA composites

Green composites, a bio‐based polymer matrix is reinforced by natural fibers, are special class of bio‐composites. Interest about green composites is continuously growing because they are environment‐friendly. This study describes the preparation and mechanical characterization of green composites using polylactic acid (PLA) matrix including chicken feather fiber (CFF) as reinforcement. Extrusion and an injection molding process were used to prepare CFF/PLA composites at a controlled temperature range. CFF/PLA composites with fiber mass content of 2%, 5%, and 10% were manufactured. The effects of fiber concentration and fiber length on mechanical properties of CFF/PLA composites have been studied. Mechanical properties of composites were investigated by tensile, compression, bending, hardness, and Izod impact testing. The results of experiments indicated that Young's modulus, compressive strength, flexural modulus, and hardness of the PLA reinforced CFF composites are higher but tensile strength, elongation at break, bending strength and impact strength of them are lower than pure PLA. The results indicate that these types of composites can be used for various applications. POLYM. COMPOS., 38:837–845, 2017. © 2015 Society of Plastics Engineers     

Microstructure and fracture behavior of (co)injection‐molded polyamide 6 composites with short glass/carbon fiber hybrid reinforcement

The mechanical and fracture properties of injection molded short glass fiber)/short carbon fiber reinforced polyamide 6 (PA 6) hybrid composites were studied. The short fiber composites of PA 6 glass fiber, carbon fiber, and the hybrid blend were injection molded using a conventional machine whereas the two types of sandwich skin–core hybrids were coinjection molded. The fiber volume fraction for all formulations was fixed at 0.07. The overall composite density, volume, and weight fraction for each formulation was calculated after composite pyrolysis in a furnace at 600°C under nitrogen atmosphere. The tensile, flexural, and single‐edge notch‐bending tests were performed on all formulations. Microstructural characterizations involved the determination of thermal properties, skin–core thickness, and fiber length distributions. The carbon fiber/PA 6 (CF/PA 6) formulation exhibits the highest values for most tests. The sandwich skin‐core hybrid composites exhibit values lower than the CF/PA 6 and hybrid composite blends for the mechanical and fracture tests. The behaviors of all composite formulations are explained in terms of mechanical and fracture properties and its proportion to the composite strength, fiber orientation, interfacial bonding between fibers and matrix, nucleating ability of carbon fibers, and the effects of the skin and core structures. Failure mechanisms of both the matrix and the composites, assessed by fractographic studies in a scanning electron microscope, are discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 957–967, 2005     

挤出-注塑制备黄麻增强PLA复合材料及其性能

通过挤出共混、造粒、注射成型的方式制备了黄麻纤维填充聚乳酸(PLA)复合材料,研究了复合材料的力学性能以及黄麻与PLA之间的微观界面形貌。结果表明:黄麻的加入,并没有很好地改善黄麻/PLA复合材料的拉伸强度和弯曲强度;碱处理后的黄麻与PLA之间的界面性能有所改善;碱处理黄麻的加入,改善了黄麻/PLA复合材料的断裂伸长率与冲击韧性。