Effect of exfoliated organophilic montmorillonite on the structure and conductivity of polypropylene/polyaniline composites

This study concentrates on the effect of organophilic montmorillonite (OMMT) nanolayers on conductivity, structure, morphology, and mechanical properties of the polypropylene/polyaniline (PP/PANI) composites. The composite was prepared by in situ polymerization of aniline at different composition ratios in the presence of PP powder. The structure and conductivity of ternary PP/PANI/OMMT nanocomposites were compared with those of PP/PANI composites. DC electrical conductivity measurements indicated that electrical conductivity decreased in the presence of OMMT layers. Scanning electron microscopy showed that the surface of ternary nanocomposites have more rough regions. The interaction between PANI and OMMT was confirmed by Fourier transform infrared spectroscopy. The distribution of OMMT layers in the polymer matrix, as an effective parameter on the properties of nanocomposite, was investigated and confirmed using X‐ray diffraction and transmission electron microscopy. The results showed an exfoliated array for OMMT layers in the nanocomposite structure. The shear storage modulus for PP/PANI composites was lower than that for pure PP; however, it was increased for PP/PANI/OMMT nanocomposites. The data from the tensile and izod impact strength showed that the Young's modulus and izod impact strength were increased slightly by the addition of OMMT, whereas the elongation at break was decreased. POLYM. COMPOS., 38:699–707, 2017. © 2015 Society of Plastics Engineers     

Effect of coupling agents on the thermal and mechanical properties of polypropylene–jute fabric composites

Composites with different jute fabric contents and polypropylene (PP) were prepared by compression molding. The composite tensile modulus increased as the fiber content increased, although the strain at break decreased due to the restriction imposed on the deformation of the matrix by the rigid fibers. Moreover, and despite the chemical incompatibility between the polar fiber and the PP matrix, the tensile strength increased with jute content because of the use of long woven fibers. The interfacial adhesion between jute and PP was improved by the addition of different commercial maleated polypropylenes to the neat PP matrix. The effect of these coupling agents on the interface properties was inferred from the resulting composite mechanical properties. Out‐of‐plane instrumented falling weight impact tests showed that compatibilized composites had lower propagation energy than uncompatibilized ones, which was a clear indication that the adhesion between matrix and fibers was better in the former case since fewer mechanisms of energy propagation were activated. These results are in agreement with those found in tensile tests, inasmuch as the compatibilized composites exhibit the highest tensile strength. Scanning electron microscopy also revealed that the compatibilized composites exhibited less fiber pullout and smoother fiber surface than uncompatibilized ones. The thermal behavior of PP–compatibilizer blends was also analyzed using differential scanning calorimetry, to confirm that the improvements in the mechanical properties were the result of the improved adhesion between both faces and not due to changes in the crystallinity of the matrix. Copyright © 2006 Society of Chemical Industry     

The influence of matrix viscosity on properties of polypropylene/polyaniline composite fibers—Rheological,electrical, and mechanical characteristics

Electrically conductive composites containing polypropylene (PP) and polyaniline (PANI) were prepared using PP with three different melt flow rates (MFRs) and a commercial PANI‐complex in proportions of 80% by weight and 20%, respectively. Composite blends were melt‐spun to fibers under different solid‐state draw ratios. Rheological studies of dynamic viscosity, as well as the storage modulus and loss modulus showed that the prepared PANI‐complex/PP blends exhibit different dynamic rheological behavior, depending on the PP used. This confirms the blends' morphological differences. PP matrix viscosity was found to play an important role in the electrical properties of the prepared fibers. Fibers prepared using the matrix with the lowest viscosity, showed a larger dispersed phase size in the cross‐sectional SEM micrographs, maximum conductivity observed at higher draw ratios and a more linear resistance–voltage relationship than those of the fibers prepared using the higher viscosity matrices. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Electroconductive polyblend fibers of polyamide‐6/polypropylene/polyaniline: Electrical,morphological, and mechanical characteristics

Melt spun drawn fibers were prepared using a ternary blend of PP/PA6/PANI‐complex (polypropylene/polyamide‐6/polyaniline‐complex). Their electrical and mechanical properties were compared to those of binary blend fibers of PP/PANI‐complex. The results of the morphological studies on 55:25:20 PP/PA6/PANI‐complex ternary fibers were found to be in accordance with the predicted morphology for the observed conductivity vs. fiber draw ratio. The scanning electron microscopy (SEM) micrographs of the ternary blend illustrated at least a three‐phase morphology of a matrix/core‐shell dispersed phase style, with widely varying sizes of droplets. This resulted in a dispersed morphology that, in some parts of the blend, approached a bicontinuous/dispersed phase morphology due to coalescence of the small droplets. The matrix was PP and the core‐shell dispersed phase was PA6 and PANI‐complex, in which a part of the PANI‐complex had encapsulated the PA6 phase and the remaining was solved/dispersed in the PA6 core, as later confirmed by X‐ray mapping. When the ternary blend fibers were compared to the binary fibers, the formers were able to combine better conductivity (of an order of 10^?3 S cm^?1) with a greater tensile strength only at a draw ratio of 5. This indicated that the draw ratio is more critical for the ternary blend fibers, because both conductivity and tensile strength depended on the formation of fibrils from the core‐shell dispersed phase of the PA6/PANI‐complex. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Morphological,mechanical, and physical properties of composites made with wood flour‐reinforced polypropylene/recycled poly(ethylene terephthalate) blends

Wood flour (WF)‐filled composites based on a polypropylene (PP)/recycled polyethylene terephthalate (r‐PET) matrix were prepared using two‐step extrusion. Maleic anhydride grafted polypropylene (MAPP) was added to improve the compatibility between polymer matrices and WF. The effects of filler and MAPP compatibilization on the water absorption, mechanical properties, and morphological features of PP/r‐PET/WF composites were investigated. The addition of MAPP significantly improved mechanical properties such as tensile strength, flexural strength, tensile modulus, and flexural modulus compared with uncompatibilized composites, but decreased elongation at break. Scanning electron microscopic images of fracture surface specimens revealed better interfacial interaction between WF and polymer matrix for MAPP‐compatibilized PP/r‐PET/WF composites. MAPP‐compatibilized PP/r‐PET/WF composites also showed reduced water absorption due to improved interfacial bonding, which limited the amount of absorbable water molecules. These results indicated that MAPP acts as an effective compatibilizer in PP/r‐PET/WF composites. POLYM. COMPOS., 38:1749–1755, 2017. © 2015 Society of Plastics Engineers     

玻纤增强PP热塑性片材的制备及力学性能研究

采用熔融浸渍法制备了玻璃纤维毡增强聚丙烯（PP）热塑性复合片材;通过在PP中加入复合改性PP改善了基体与增强纤维间的相容性;考察了相容剂、PP种类及玻纤毡种类对复合片材的影响。结果表明,相容剂的加入可使复合片材的拉伸强度提高29％、拉伸模量提高23％、弯曲强度提高42％、弯曲模量提高25％;高熔体质量流动速率PP可使片材的弯曲与冲击性能进一步改善。连续玻纤毡和长玻纤毡增强PP复合片材,前者综合力学性能良好,而后者则冲击强度较弱、弯曲性能加强。     

Improvement in properties of multiwalled carbon nanotube/polypropylene nanocomposites through homogeneous dispersion with the aid of surfactants

The effects of different surfactants on the properties of multiwalled carbon nanotubes/polypropylene (MWCNT/PP) nanocomposites prepared by a melt mixing method have been investigated. Sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (NaDDBS) were used as a means of noncovalent functionalization of MWCNTs to help them to be dispersed uniformly into the PP matrix. The effects of these surfactant‐treated MWCNTs on morphological, rheological, thermal, crystalline, mechanical, and electrical properties of MWCNT/PP composites were studied using field emission scanning electron microscopy, optical microscopy, rheometry, tensile, and electrical conductivity tests. It was found that the surfactant‐treatment and micromixing resulted in a great improvement in the state of dispersion of MWCNTs in the polymer matrix, leading to a significant enhancement of Young's modulus and tensile strength of the composites. For example, with the addition of only 2 wt % of SDS‐treated and NaDDBS‐treated MWCNTs, the Young's modulus of PP increased by 61.1 and 86.1%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical,thermal, and morphological properties of maleic anhydride‐g‐polypropylene compatibilized and chemically modified banana‐fiber‐reinforced polypropylene composites

Composites were prepared with chemically modified banana fibers in polypropylene (PP). The effects of 40‐mm fiber loading and resin modification on the physical, mechanical, thermal, and morphological properties of the composites were evaluated with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Infrared (IR) spectroscopy, and so on. Maleic anhydride grafted polypropylene (MA‐g‐PP) compatibilizer was used to improve the fiber‐matrix adhesion. SEM studies carried out on fractured specimens indicated poor dispersion in the unmodified fiber composites and improved adhesion and uniform dispersion in the treated composites. A fiber loading of 15 vol % in the treated composites was optimum, with maximum mechanical properties and thermal stability evident. The composite with 5% MA‐g‐PP concentration at a 15% fiber volume showed an 80% increase in impact strength, a 48% increase in flexural strength, a 125% increase in flexural modulus, a 33% increase in tensile strength, and an 82% increase in tensile modulus, whereas the heat deflection temperature increased by 18°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Pineapple leaf fiber reinforced thermoplastic composites: Effects of fiber length and fiber content on their characteristics

Pineapple leaf fiber (PALF) was used as a reinforcement in polyolefins. Polypropylene (PP) and low‐density polyethylene (LDPE) composites with different fiber lengths (long and short fibers) and fiber contents (0–25%) were prepared and characterized. The results showed that the tensile strength of the composites increased when the PALF contents were increased. It was observed that the composites containing long fiber PALF were stronger than the short fiber composites as determined by greater tensile strength. An SEM study on the tensile fractured surface confirmed the homogeneous dispersion of the long fibers in the polymer matrixes better than dispersion of the short fibers. The unidirectional arrangement of the long fibers provided good interfacial bonding between the PALF and polymer which was a crucial factor in achieving high strength composites. Reduction in crystallinity of the composites, as evident from XRD and DSC studies suggested that the reinforcing effect of PALF played an important role in enhancing their mechanical strength. From the rule of mixtures, the stress efficiency factors of the composite strength could be calculated. The stress efficiency factors of LDPE were greater than those of PP. This would possibly explain why the high modulus fiber (PALF) had better load transfers to the ductile matrix of LDPE than the brittle matrix of PP. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Direct fluorination of Twaron fiber and investigation of mechanical thermal and morphological properties of high density polyethylene and Twaron fiber composites

Composites consisting of high density polyethylene (HDPE) reinforced with randomly oriented chopped Twaron fibers (both fluorinated and nonfluorinated) show a significant increase in mechanical and thermal properties. To increase the better fiber matrix adhesion, the Twaron fiber is surface fluorinated using elemental fluorine. The surface of the Twaron fiber becomes very rough and the diameter of Twaron fiber increases from ～ 12 to 14 μm after fluorination. The composites were prepared using solution method to overcome the damage of the fiber. The tensile strength and the Young's modulus increases with increasing fiber content. The tensile strength and modulus of modified fiber (fluorinated Twaron fiber) composites is much higher than nonmodified fiber composites indicating that there is better mechanical interlocking between the modified fiber and the matrix. Thermal properties obtained from DSC and DTA‐TG analysis of the fluorinated fiber composites are also improved. Contact angle measurements, as well as the surface energy measurements, indicate that the composites are more wettable and is maximum for fluorinated fiber composites i.e., surface energy for fluorinated fiber composites is highest. Crystallinity is also higher for fluorinated fiber composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

An investigation of the interfacial adhesion between reclaimed newspaper and recycled polypropylene composites through the investigation of their mechanical properties

The effects of different parameters (e.g. method of defibration of newspaper; size of the fiber; type and concentrations of coupling agents, impact modifiers, and fire retardants) on the mechanical properties of old newspaper fiber-filled recycled polypropylene (PP) have been evaluated. Statistical methods were applied to determine the effects of variables on the tensile strength, Young's modulus, tensile toughness, and impact strength. Statistical analysis revealed that the composites based on newspaper fiber prepared by mechanical defibration showed a better tensile strength compared with those prepared by the steam explosion process, while the latter type of fiber outperformed the former as far as the other mechanical properties are concerned. In the presence of maleic anhydride grafted PP (MPP) and the initiator dicumyl peroxide (DCPO), the tensile strength of the composites increased with increasing fiber loading and fiber size. Moreover, both the tensile strength and the modulus increased with an increase in the concentrations of MPP and DCPO, even in the presence of an impact modifier and fire retardants for surface-modified newspaper-filled composites. Since the tensile strength of short fiber reinforced composites is strongly dependent of the degree of adhesion between the fiber and matrix, the experimental results suggest that either one of these (MPP and DCPO) or both act as the interfacial bonding agent to develop a strong interphase between old newspaper fiber and recycled PP.     

Properties of (Low‐density polyethylene)/(natural rubber)/(water hyacinth fiber) composites: The effect of polyaniline

The effects of polyaniline (PANI)‐modified water hyacinth fiber on the properties of (low‐density polyethylene)/(natural rubber)/(water hyacinth fiber) (LDPE/NR/WHF) composites were studied. The composites were prepared by using a Brabender Plasticorder at 160^oC and a rotor speed of 50 rpm for 6 minutes. LDPE/NR/WHF_PANI composites exhibited higher tensile strength, Young's modulus, elongation at break, melting temperature, and electrical conductivity but lower molar sorption, capacitance, percentage crystallinity, and interparticle spacing than LDPE/NR/WHF composites. Scanning electron microscopy morphology showed a better interfacial adhesion of PANI‐modified water hyacinth fiber (WHF_PANI) and the LDPE/NR phases than when unmodified WHF was used. J. VINYL ADDIT. TECHNOL., 20:122–130, 2014. © 2014 Society of Plastics Engineers     

Utilization of polyethylene terephthalate waste as a carbon filler in polypropylene matrix: Investigation of mechanical,rheological, and thermal properties

Polyethylene terephthalate (PET) waste was converted into carbon and the feasibility of utilizing it as a reinforcing filler material in a polypropylene (PP) matrix was investigated. The carbon produced by the pyrolysis of waste PET at 900°C in nitrogen atmosphere contains high carbon content (>70 wt%). PP/carbon composites were produced by melt blending process at varying loading concentrations. Scanning electron microscopy images at the fractured surface revealed that the carbon filler has better compatibility with the PP matrix. The mechanical, thermal, and rheological properties and surface morphology of the prepared composites were studied. The thermogravimetric analysis studies showed that the thermal stability of the PP/carbon composites was enhanced from 300 to 370°C with 20 wt% of carbon. At lower angular frequency (0.01 rad/s), the storage modulus (G′) of PP was 0.27 Pa and those of PP with 10 and 20 wt% carbon was 4.06 and 7.25 Pa, respectively. Among the PP/carbon composite prepared, PP with 5 wt% carbon showed the highest tensile strength of 38 MPa, greater than that of neat PP (35 MPa). The tensile modulus was enhanced from 0.9 to 1.2 GPa when the carbon content was increased from 0 to 20 wt%.     

Effect of the delignification of wood fibers on the mechanical properties of wood fiber–polypropylene composites

The effect of the delignification of hornbeam fibers on the mechanical properties of wood fiber–polypropylene (PP) composites was studied. Original fibers and delignified fibers at three levels of delignification were mixed with PP at a weight ratio of 40:60 in an internal mixer. Maleic anhydride (0.5 wt %) as the coupling agent and dicumyl peroxide (0.1 wt %) as the initiator were applied. The produced composites were then hot‐pressed, and specimens for physical and mechanical testing were prepared. The results of the properties of the composite materials indicate that delignified fibers showed better performance in the enhancement of tensile strength and tensile modulus, whereas the hardness of the composites was unaffected by delignification. Delignified fibers also exhibited better water absorption resistance. Notched impact strength was higher for delignified fiber composites, but it was reduced at higher delignification levels. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4759–4763, 2006     

Processing and characterization of epoxy nanocomposites reinforced by cup-stacked carbon nanotubes

The effect of the dispersion, ozone treatment and concentration of cup-stacked carbon nanotubes on mechanical, electrical and thermal properties of the epoxy/CSCNT nanocomposites were investigated. Ozone treatment of carbon fibers was found to increase the surface oxygen concentration, thereby causing the contact angle between water, epoxy resin and carbon fiber to be decreased. Thus, the tensile strength, modulus and the coefficient friction of carbon fiber reinforced epoxy resin were improved. Moreover, the dispersion of fibers in polymer was increased and the electrical resistivity was decreased with the addition of filler content. The dynamic mechanical behavior of the nanocomposite sheets was studied. The storage modulus of the polymer was increased by the incorporation of CSCNTs. But the glass transition temperature decreased with increasing fiber loading for the ozone treated fiber composites. The ozone treatment did affect the morphology, mechanical and physical properties of the CSCNT.     

Organic functionalization of carbon nanofibers for composite applications

The present work reports the study of the effect of different chemical functionalization methods on the interfacial characteristics of the polymer composites formed. The chemically modified carbon nanofibers were blended with polypropylene (PP) and PP modified with maleic anhydride on a mini twin‐screw extruder. The functionalization methods were designed for minimum fiber damage and enhanced fiber/matrix interactions by chemical reaction of the functional groups introduced at the nanofibers surface with the maleic anhydride grafted at the PP. The degree of nanofiber functionalization was studied using thermogravimetric analysis. The composites were analyzed for nanofiber dispersion, mechanical properties, and electrical resistivity. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Studies on the Physicomechanical Properties of Sodium Periodate Oxidized Jute Reinforced Polypropylene (PP) Composites

In the present work, effects of oxidation and fiber content (from 20 to 35 wt. %) on the physicomechanical properties of jute-polypropylene (PP) composites were studied. Mechanical properties (tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus, and charpy impact strength) were measured for all raw and oxidized jute-PP composites. Improved mechanical properties were obtained for oxidized jute-PP composites. Interfacial adhesion and bonding between the fiber and PP matrix were investigated by scanning electron micrograph analysis. Improved interfacial interactions and reduced water absorption were found for oxidized jute-PP composites. Water absorption tests of all composites were also performed.     

Non‐traditional lightweight polypropylene composites reinforced with milkweed floss

Lightweight composites are preferred for automotive applications due to the weight restrictions and also due to the presence of inherent voids that can enhance the sound absorption of these composites. The density of the reinforcing materials plays a crucial role in such lightweight composites. Milkweed is a unique natural cellulose fiber that has a completely hollow center and low density (0.9 g cm^?3) unlike any other natural cellulose fiber. The low density of milkweed fibers will allow the incorporation of higher amounts of fiber per unit weight of a composite, which is expected to lead to lightweight composites with better properties. Polypropylene (PP) composites reinforced with milkweed fibers have much better flexural and tensile properties than similar PP composites reinforced with kenaf fibers. Milkweed fiber‐reinforced composites have much higher strength but are stiffer than kenaf fiber‐reinforced PP composites. Increasing the proportion of milkweed in the composites from 35 to 50% increases the flexural strength but decreases the tensile strength. The low density of milkweed fibers allows the incorporation of higher amounts of fibers per unit weight of the composites and hence provides better properties compared to composites reinforced with common cellulose fibers with relatively high density. This research shows that low‐density reinforcing materials can more efficiently reinforce lightweight composites. Copyright © 2010 Society of Chemical Industry     

剑麻纤维/长玻纤混杂增强PP复合材料的力学性能研究

采用剑麻纤维(SF)和长玻璃纤维(LGF)混杂增强聚丙烯(PP)复合材料,考察了SF/LGF的比例和含量对PP复合材料力学性能的影响。结果表明:SF/LGF在聚丙烯树脂基体中呈交叉网状分布,这有利于提高复合材料的冲击强度、弯曲模量、拉伸强度和软化点。在SF/LGF质量比为2 2∶,二者总质量分数为30%时,SF/LGF混杂增强PP复合材料的综合力学性能较好。     

Effects of wheat straw fiber content and characteristics,and coupling agent concentration on the mechanical properties of wheat straw fiber‐polypropylene composites

Wheat straw fiber‐polypropylene (PP) composites were prepared to investigate the effects of wheat straw fiber content (10, 20, 30, 40, and 50 wt %), fiber size (9, 28, and 35 mesh), and maleic anhydride grafted polypropylene (MAPP) concentration (1, 2, 5, and 10 wt %) on the static and dynamic mechanical properties of the wheat straw fiber‐PP composites in this study. The tensile modulus and strength of the composites increased linearly with increasing wheat straw fiber content up to 40%, whereas the elongation at break decreased dramatically to 3.78%. Compared with the composites made of the longer wheat straw fiber, the composites made of the fines (>35 mesh) had a slightly higher tensile strength of 31.2 MPa and tensile elongation of 5.39% at break. With increasing MAPP concentration, the composites showed an increase in tensile strength, and the highest tensile strength of 34.0 MPa occurred when the MAPP concentration reached 10 wt %. As wheat straw fiber content increased from 0 to 40%, the flexural modulus of the composites increased gradually from 1335 to 3437 MPa. The MAPP concentration and wheat straw fiber size distribution had no appreciable effect on the static flexural modulus of the composites. The storage flexural modulus of the composites increased with increasing wheat straw fiber content. The scanning electron microscopy (SEM) observation on the fracture surface of the composites indicated that a high wheat straw fiber content (>30 wt %) resulted in fiber agglomeration and a reduction in interfacial bonding strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009