Dynamic mechanical analysis of novel composites from commingled polypropylene fiber and banana fiber

Polypropylene (PP)/banana fiber (BF) composites were fabricated from PP fiber and short BF by novel commingling method. The dynamic mechanical analysis (DMA) of the composites was performed with reference to BF loading and fiber surface treatments. By the incorporation of BF into the PP matrix, the storage modulus and loss modulus have been found to increase, whereas damping factor has been found to decrease. Glass transition temperature was found to increase with increase in BF loading. The viscoelastic properties of the composites were also found to depend on fiber surface treatments. The activation energy of the composites for the glass transition has been found to be increased by the increase in BF loading. Surface treatment of the BF further increased the activation energy of the composites, indicating a stronger interface for treated fiber composites. Scanning electron microscopy (SEM) photographs of the BF showed the physical changes induced by the surface treatments. Fourier transform infrared spectroscopy (FTIR) was used to ascertain the existence of the type of interfacial bonds. The use of theoretical equations to predict the storage modulus has also been discussed. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Alfa fiber/polypropylene composites: Influence of fiber extraction method and chemical treatments

Alfa fiber/polypropylene composites were manufactured using twin-screw extrusion. Fibers were extracted using alkaline and steam explosion methods. Three chemical treatments were also applied to the alkaline-extracted fibers: stearic acid (SA), and potassium permanganate dissolved in water (KW) and in acetone (KA). Finally, thermal annealing was applied to the composites. The results indicate that composites with steam-exploded fibers had a significantly higher melt flow index than composites with alkaline-extracted fibers. Moreover, the incorporation of fibers into the matrix increased the Young's modulus, where the optimum results were obtained utilizing the alkaline-extracted fibers. Both extraction methods also significantly decreased the water uptake, especially the steam explosion. The three chemical treatments increased the melt flow index and conversely decreased the tensile strength and Young's modulus. In addition, KW treatment decreased the water uptake. Finally, thermal annealing increased the tensile strength and Young's modulus of composites with SA-treated fibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47392.     

阻燃香蕉纤维增强聚乳酸复合材料的制备与表征

采用乙酰柠檬酸三丁酯(ATBC)作为增塑剂增塑聚乳酸,添加改性香蕉纤维和膨胀型阻燃剂(IFR)制备阻燃香蕉纤维增强聚乳酸复合材料.研究结果表明,偶联剂处理纤维的效果最好,使复合材料的拉伸、弯曲强度分别达到57.49MPa、101.80MPa,与扫描电子显微镜(SEM)的结果一致;IFR含量为5份(以聚乳酸为100份计)时综合性能最佳,材料的极限氧指数达到了 32.8%,垂直燃烧实验达到了 V-0 级(UL-94),材料的拉伸和弯曲强度分别为43.97 MPa 和87.95MPa,效果最好.热失重研究结果表明,阻燃香蕉纤维的加入能明显提高聚乳酸的热分解温度和残炭量.     

Rheological properties of polypropylene/hemp fiber composites

This study investigates the effect of hemp fibres on the shear and elongational rheology of polypropylene (PP). The parameters studied were hemp content (0‐30%) and maleic anhydride polypropylene (MAPP) addition (0‐0.6%). Shear rheology revealed that fibre content mainly influences low shear rate properties like yield stress and zero‐shear‐viscosity while coupling agent addition mainly influences intermediate to high shear rate parameters like relaxation time, power‐law index and Yasuda parameter. On the other hand, elongational rheology results showed a strain softening behaviour of the composites with increasing consistency and decreasing strain at break as fibre concentration increases. MAPP addition is also shown to improve the fibre‐polymer compatibility, but at the same time produces a plasticizing effect having a significant effect on rheological properties. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Fibers from polypropylene/nano carbon fiber composites

Fibers from polypropylene and polypropylene/vapor grown nano carbon fiber composite have been spun using conventional melt spinning equipment. At 5 wt% nano carbon fiber loading, modulus and compressive strength of polypropylene increased by 50 and 100%, respectively, and the nano carbon fibers exhibited good dispersion in the polypropylene matrix as observed by scanning electron microscopy.     

Preparation of high-modulus and high-strength isotactic polypropylene fiber by zone-annealing method

The zone-annealing method was utilized to prepare a high-modulus and high-strength fiber from isotactic polypropylene. The dynamic storage modulus at room temperature of the fiber obtained reached 21 times; 10¹⁰ dyn/cm², which corresponded to 51% of the crystal modulus along the molecular chains, 41.2 × 10¹⁰ dyn/cm². The relationships between mechanical properties and superstructure were investigated based on results of measurements of orientation, crystallinity, tensile properties, and dynamic viscoelasticity. It was found that the excellent mechanical properties were directly attributed to the large number of tie molecules and to the high orientation of the amorphous chains. Further, the characteristics of this method were discussed compared with the results obtained by other investigators.     

Comparative experimental measurements of jute fiber/polypropylene and coir fiber/polypropylene composites as ionizing radiation

Jute and coir fiber‐reinforced polypropylene (PP) composites (45 wt% fiber) were prepared by compression molding. Composites were fabricated with irradiated jute fiber/irradiated PP and irradiated coir fiber/irradiated PP at different doses (250–1,000 krad). It was revealed that jute‐based composites had better mechanical properties as compared to coir‐based composites. Interfacial shear strength of jute/PP and coir/PP systems was measured by using the single‐fiber fragmentation test. Scanning electron microscopy investigation shows poor fiber matrix adhesion for coir‐based composites than that of jute‐based composites. Water uptake and soil degradation tests of the composites were also performed. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Nonisothermal crystallization kinetics of kenaf fiber/polypropylene composites

Nonisothermal crystallization behavior of model ecocomposites based on polypropylene (PP), maleic anhydride modified polypropylene (PP_m), and kenaf fibers were extensively studied. Melting and crystallization behavior of the composites with 20 wt/wt% kenaf fibers were analyzed by differential scanning calorimetry (DSC) in dynamic regime (with heating rate of 10 K/min, and cooling rates of 5, 10, 15, 20, and 40 K/min). It was shown that the kenaf fiber surface acts as a nucleating agent during nonisothermal crystallization of both PP matrices, shifting the onset and peak crystallization temperatures toward higher values. Crystallization behavior was analyzed by Avrami, Jeziorny, Ozawa, Mo, and Kissinger methods. The results confirmed the applicability of the used models, with exception of the Ozawa approach that was rather inapplicable for these composites. POLYM. ENG. SCI., 47:745–749, 2007. © 2007 Society of Plastics Engineers.     

Preparation and characterization of polypropylene/serpentine composites

Composites of serpentine and polypropylene (PP) were prepared by twin‐screw extrusion. Serpentine was collected as rocks from the Ankara–Beynam region and ground into powder with an average particle size of about 3 μm for composite production. Both as‐received (rock) and powdered serpentine were characterized. A silane coupling agent (SCA), γ‐aminopropyl triethoxy silane, was used for the surface treatment of serpentine. Mechanical properties of the composites were measured in terms of impact strength, elastic modulus, stress at yield, stress at break, and percentage strain at break. The addition of serpentine was found to have a profound effect on the reinforcement of the PP matrix. Because of the stronger interactions at the interphase induced by SCA treatment, mechanical properties were improved further in comparison with the untreated composites. Similar thermal and morphological behaviors were recorded for the composites with and without surface treatment. Thermal studies showed an increase in both melting temperature and percentage crystallinity of the composites. Scanning electron microscopy analysis revealed that homogeneous distribution of filler was observed at low filler contents, but a certain extent of agglomeration was also seen at high filler loadings. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Conducting polypyrrole‐coated banana fiber composites: Preparation and characterization

In this study, conducting banana fibers (BF) were obtained through in situ oxidative polymerization of pyrrole (Py) on the BF surface using ferric chloride hexahydratate (FeCl₃·6H₂O) as an oxidant. Suitable reaction conditions are outlined for the polymerization of Py: oxidant/monomer molar ratio, Py concentration and polymerization time of 2/1, 0.05 mol.L⁻¹ and 30 min, respectively. Under these conditions, high‐quality conducting fibers containing polyPy and BF (PPy‐BF) were obtained with an electrical resistivity as low as 0.54 Ω.cm. The PPy‐BF was blended with different concentrations of polyurethane (PU) by mixing the two components in a vacuum chamber and then applying compression molding. The electrical resistivity of composites with 25 wt% of PPy‐BF was around 1.8 × 10⁵ Ωcm, which is approximately 10⁸ times lower than that found for pure PU. Moreover, PU/PPy‐BF composites exhibited higher mechanical properties than pure PU and PU/PPy, indicating that these conducting fibers can also be used as reinforcement for polymer matrices. The properties of the PPy‐BF obtained by the method described herein open interesting possibilities for novel applications of electrically conducting fibers, from smart sensors to new conducting fillers that can be incorporated into several polymer matrixes to develop conducting polymer composites with good mechanical properties.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

The role of interface modification on thermal degradation and crystallization behavior of composites from commingled polypropylene fiber and banana fiber

The thermal degradation behavior of banana fiber and polypropylene/banana fiber composites has been studied by thermogravimetric analysis. Banana fiber was found to be decomposing in two stages, first one around 320°C and the second one around 450°C. For chemically treated banana fiber, the decomposition process has been at a higher temperature, indicating thermal stability for the treated fiber. Activation energies for thermal degradation were estimated using Coats and Redfern method. Calorific value of the banana fiber was measured using a constant volume isothermal bomb calorimeter. Crystallization studies exhibited an increase in the crystallization temperature and crystallinity of polypropylene upon the addition of banana fiber. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Study of the flexural modulus of natural fiber/polypropylene composites by injection molding

Effect of fiber compression on flexural modulus of the natural fiber composites was examined. The kenaf, bagasse, and polypropylene were mixed into pellets, and composites were fabricated by injection molding. To predict flexural modulus of the composites, the Young's modulus of kenaf and bagasse fiber were measured. Using the obtained Young's modulus, the flexural modulus of the composites was predicted by Cox's model that incorporates the effect of fiber compression. It was found that those fibers with high Young's modulus were more compressed than that with low Young's modulus. Moreover, the distribution of fiber length and orientation in the composites were also investigated. To calculate the orientation factor for the prediction model, the distribution function of fiber orientation was determined to a triangular function. The flexural modulus of the composites increased with increase of volume fraction. The predicted values were in good agreement with the experimental values. Furthermore, it was revealed by SEM that the porous structure of the natural fibers was compressed. The fiber compression ratio (3.6) in bagasse was higher than that in kenaf (1.4) due to the difference in porous structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 911–917, 2006     

Facilitating transcrystallization of polypropylene/glass fiber composites by imposed shear during injection molding

The transcrystal plays an important role in the enhancement of mechanical and thermal performances for polymer/glass fiber composites. Shear has been found to be a very effective way for the formation of transcrystal. Our purpose of this study was to explore the possibility to obtain the transcrystal in real processing such as injection molding. We will report our recent efforts on exploring the development of microstructure of polypropylene (PP)/glass fiber composite from skin to core in the injection-molded bars obtained by so-called dynamic packing injection molding which imposed oscillatory shear on the melt during solidification stage. A clear-cut shear-facilitated transcrystallization of PP on glass fibers was observed in the injection-molding bar for the first time. We suggested that shear could facilitate the transcrystalline growth through significantly improving the fiber orientation and the interfacial adhesion between fiber and matrix.     

Production and characterisation of vapour grown carbon fiber/polypropylene composites

Polymeric composites are widely used in the aircraft and automotive industries. Their high strength-to-weight ratio makes significant weight reduction possible. Beside this advantage, the polymer materials also offer a good corrosion resistance but the mechanical and electrical properties are not satisfactory. In order to increase these properties, vapour grown carbon fibers (VGCF) with high strength and metal-like electrical conductivity can be embedded in the polymeric matrix. To ensure a good adhesion between the fibers and the polymer matrix a functionalization of the chemically inert surface of the fibers is necessary.In the present research work oxygen-containing functional groups were introduced on the fiber surface through cold plasma treatment. Measurements of the fiber surface energy after plasma functionalization showed an enhancement of at least 50% of the initial value. The VGCF/PP composites with different amounts of VGCF were made through extrusion and injection molding. The results show that the degree of fiber surface functionalization and the fiber distribution and orientation in the polypropylene (PP) matrix may strongly influence the mechanical properties of the composite.     

Tensile properties of wood flour/kenaf fiber polypropylene hybrid composites

Hybrid composites of wood flour/kenaf fiber and polypropylene were prepared at a fixed fiber to plastic ratio of 40 : 60 and variable ratios of the two reinforcements namely 40 : 0, 30 : 10, 20 : 20, 10 : 30, and 0 : 40 by weight. Polypropylene was used as the polymer matrix, and 40–80 mesh kenaf fiber and 60–100 mesh wood flour were used as the fiber and the particulate reinforcement, respectively. Maleic anhydride and dicumyl peroxide were also used as the coupling agent and initiator, respectively. Mixing process was carried out in an internal mixer at 180°C at 60 rpm. ASTM D 638 Type I tensile specimens of the composites were produced by injection molding. Static tensile tests were performed to study the mechanical behavior of the hybrid composites. The hybrid effect on the elastic modulus of the composites was also investigated using the rule of hybrid mixtures and Halpin–Tsai equations. The relationship between experimental and predicted values was evaluated and accuracy estimation of the models was performed. The results indicated that while nonhybrid composites of kenaf fiber and wood flour exhibited the highest and lowest modulus values respectively, the moduli of hybrid composites were closely related to the fiber to particle ratio of the reinforcements. Rule of hybrid mixtures equation was able to predict the elastic modulus of the composites better than Halpin–Tsai equation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical properties of surface modified jute fiber/polypropylene nonwoven composites

In this study, the jute/polypropylene nonwoven reinforced composites were prepared using film stacking method. The surface of jute fibers was modified using alkali treatment. These alkali treated jute fiber nonwoven composites were analyzed for their tensile and flexural properties. Increasing the amount of jute fibers in the nonwovens has improved the mechanical properties of their composites. The effect of stacking sequence of preferentially and nonpreferentially aligned nonwovens within the composites was also investigated. The flexural and tensile moduli of composites were found to be significantly enhanced when nonwovens consisting of preferentially and nonpreferentially aligned jute fibers were stacked in an alternate manner. The existing theoretical models of tensile modulus of fiber reinforced composites have been analyzed for predicting the tensile modulus of nonwoven composites. In general, a good agreement was obtained between the experimental and theoretical results of tensile modulus of nonwoven composites. POLYM. COMPOS., 35:1044–1050, 2014. © 2013 Society of Plastics Engineers     

Development of novel silk/wool hybrid fibre polypropylene composites

Recycling and reusing fibrous waste is one of the most important environmental tasks that face the world, to reduce environmental loading and promote the most effective use of resources. In this study, the shuttle-less loom silk selvedge waste and wool fibres were used to produce functional composites. First, the silk selvedge waste was opened and converted into fibrous form. The opened silk fibres were mixed with wool and polypropylene staple fibres in the proportions of 35/15/50, 35/35/30 and 15/35/50. The functional composites were produced by compression moulding technique with optimum process conditions. The effect of silk and wool fibre content on the mechanical properties of silk/wool hybrid fibre polypropylene composites was studied by measuring the tensile strength, flexural strength and impact strength of the resultant composite material. The thermal conductivity and water uptake properties of the composites were also studied. The morphology of silk/wool hybrid fibre polypropylene composites was analyzed by scanning electron microscopy technique. It was found that the composite containing 35/15/50 silk/wool/polypropylene showed the best performance in mechanical properties. The tensile, flexural and impact strengths of 35/15/50 silk/wool/polypropylene composite sample were found to be 30.21 MPa, 19.88 MPa and 0.713 J, respectively. The results also showed that the thermal conductivity was the least while the silk and wool fibre contents were the most in the composite. The water absorption study showed that the composite containing more fibre content possessed maximum water uptake properties. The study strongly suggests that the silk/wool hybrid fibre polypropylene composite materials are quite capable of serving as a potential cost effective, technologically viable, and attractive substitute to the conventional glass epoxy composites used as electrical insulating materials in printed circuit boards.     

Bisphenol containing novel polyimides/glass fiber composites

A new diamine was synthesized using bisphenol‐A and p‐amino benzoic acid. Polyimides I and II were prepared with the diamine and pyromellitic dianhydride/3,3′,4,4′ benzophenone tetracarboxylic acid dianhydride. Bismaleimide (BMI) was synthesized using the same diamine and maleic anhydride. The prepared diamine and polyimides were characterized using FTIR. Thermo gravimetric analysis was used to study the thermal properties of synthesized polyimides and BMI. Woven glass fabric/unidirectional glass fiber‐polyimide/BMI composites were made and their properties (fiber volume fraction, density, tensile, flexural, impact, and hardness) were studied and compared with a few representative carbon fiber polyimide, carbon fiber–epoxy, and glass fiber–epoxy composites. The prepared composites were subjected to thermal aging and moisture absorption and their effects on tensile and flexural properties were studied. POLYM. COMPOS., 28: 372–380, 2007. © 2007 Society of Plastics Engineers