Effect of hybridization and chemical modification on the water‐absorption behavior of banana fiber–reinforced polyester composites

The water sorption characteristics of banana fiber–reinforced polyester composites were studied by immersion in distilled water at 28, 50, 70, and 90°C. The effect of hybridization with glass fiber and the chemical modification of the fiber on the water absorption properties of the prepared composites were also evaluated. In the case of hybrid composites, water uptake decreased with increase of glass fiber content. In the case of chemically modified fiber composites, water uptake was found to be dependent on the chemical treatment done on the fiber surface. Weight change profiles of the composites at higher temperature indicated that the diffusion is close to Fickian. The water absorption showed a multistage mechanism in all cases at lower temperatures. Chemical modification was found to affect the water uptake of the composite. Among the treated composites the lowest water uptake was observed for composites treated with silane A1100. Finally, parameters like diffusion, sorption, and permeability coefficients were determined. It was observed that equilibrium water uptake is dependent on the nature of the composite and temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3856–3865, 2004     

Effect of nonionizing radiation on the physicomechanical properties of banana fiber/pp composites with HEMA

Banana fiber‐reinforced polypropylene (PP)‐based unidirectional composites (40% fiber by weight) was manufactured by compression molding. Banana fibers and PP sheets were treated with UV radiation at different intensities and then composites were fabricated. It was found that mechanical properties of irradiated banana fiber and irradiated PP‐based composites were found to increase significantly compared to that of untreated counterparts. Irradiated banana fibers were also treated with 2‐hydroxyethyl methacrylate (HEMA) mixed with methanol (MeOH) under thermal curing method at different temperatures (30–70°C) for different curing times (20–60 min). A series of solutions of different concentrations of HEMA in methanol along with 2% benzyl peroxide were prepared. Monomer concentration, curing temperature and curing time were optimized in terms of polymer loading and mechanical properties. Composites made of 15% HEMA, 50°C and 40 min curing time showed the best mechanical properties than those of untreated composite. Scanning electron microscopy (SEM), water uptake, and simulating weathering test of the composites were also investigated. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effect of hygrothermal aging on the diffusion of seawater in epoxy/glass composites studied by positron lifetime spectroscopy

The effect of hygrothermal aging on the free volume controlled diffusion of seawater in the epoxy/glass (E/G) composite samples with E‐glass fibers woven at 0° and 45° to the epoxy matrix has been studied using Positron lifetime technique. The equilibrium mass uptake of seawater is assessed by the gravimetric method. The positron results indicate that the free volume hole size increases with hygrothermal aging in the composite E/G (0°) suggesting swelling while the hole size shows continuous decrease in the E/G (45°) composite up to 45°C. We also found that hygrothermal aging process in the present composites is an exothermic process. Although the equilibrium uptake of seawater decreases with the increasing temperature in both the cases, the magnitude of decrease is more in 0°‐oriented composite than in 45°‐oriented composite. The heat of absorption calculated from the temperature dependence of equilibrium mass uptake is found to be negative in both the cases. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers     

Effects of porosity,fiber size,and layering sequence on sound absorption performance of needle‐punched nonwovens

The relationships between the material parameters, i.e., the fiber fineness, porosity, areal density, layering sequence, and airflow resistivity with the normal‐incidence sound absorption coefficient of nonwoven composites consisting of three layers have been studied. The monofiber or multifiber needle‐punched nonwovens included poly(lactic acid) (PLA), polypropylene (PP), glass fiber, and hemp fibers. Air flow resistivity was statistically modeled and was found to increase with decreasing fiber size and nonwoven porosity. The former models developed for glass fiber mats in the literature were found to be inconsistent with the air flow resistance of the nonwovens reported below. The effects of the layering sequence on air flow resistivity and sound absorption were obtained. It was found that when the layer including reinforcement fibers, i.e., hemp or glass fiber, faced the air flow/sound source, the air flow resistance and the absorption coefficient were higher than the case when the layer including reinforcement fibers was farthest from the air flow/sound source. The difference was more pronounced if there was a greater difference between the resistivity values of the constituent layers of the nonwoven composite. Sound absorption coefficient was statistically modeled in terms of air flow resistivity and frequency. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Esterification effect of maleic anhydride on swelling properties of natural fiber/high density polyethylene composites

The natural fibers (banana, hemp, and sisal) and high density polyethylene were taken for the preparation of natural fiber/polymer composites in different ratios of 40 : 60 and 45 : 55 (w/w). These fibers were esterified with maleic anhydride (MA) and the effect of esterification of MA was studied on swelling properties in terms of absorption of water, at ambient temperature, and steam. It was found that the steam penetrates more within lesserperiod of time than water at ambient temperature. Untreated fiber composites show more absorption of steam and water in comparison to MA‐treated fiber composites. The more absorption of water was found in hemp fiber composites and less in sisal fiber composites. Steam absorption in MA‐treated and untreated fiber composites are higher than the water absorption in respective fiber composites. The natural fiber/polymer composites containing low amount of fibers show less absorption of steam and water at ambient temperature than the composites containing more amount of fibers in respective fiber composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Water absorption behavior of PALF/GF hybrid polyester composites

The water absorption characteristics of pineapple leaf fiber (PALF)/glass fiber (GF) hybrid polyester(PER) composites, and chemically modified PALF/polyester composites were evaluated by immersion in distilled water at 28, 60, and 90°C. The diffusion properties of the intimately mixed (IM) and the layered hybrid composite GPG (Glass skin and PALF core) of different PALF/GF ratio at the three temperatures were compared in order to identify the environmental ageing mechanism at different temperatures. The effect of temperature on the kinetics and thermodynamics of diffusion were also examined. The water uptake of both IM and GPG hybrid composites was decreased with increase in glass fiber content; the lowest water uptake was observed for 0.46 V_f GF hybrid composite. Among the chemically modified composites, vinyl tri 2‐methoxy ethoxy silane treated composites showed the lowest water uptake. Finally, parameters like diffusion, sorption, and permeability coefficients were determined. It was observed that equilibrium water uptake is dependent on the nature of the composite and temperature. Experimental results were also compared with theoretical predictions. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Long‐term water uptake behavior of lignocellulosic‐high density polyethylene composites

Composites of different lignocellulosic materials and high‐density polyethylene were prepared and their long‐term water absorption behaviors were studied. Wood flour, rice hulls, newsprint fibers, and kenaf fibers were mixed with the polymer at 25 and 50 wt % fiber contents and 1 and 2% compatibilizer, respectively. Water absorption tests were carried out on injection‐molded specimens at room temperature for five weeks. Results indicated a significant difference among different natural fibers with kenaf fibers and newsprint fibers exhibiting the highest and wood flour and rice hulls the lowest water absorption values, respectively. Very little difference was observed between kenaf fiber and newsprint composites and between rice hulls and wood flour composites regarding their water uptake behavior. The difference between 25 and 50% fiber contents for all composite formulations increased at longer immersion times, especially for the composites with higher water absorption. Kenaf fiber composites containing 50% kenaf fibers exhibited the highest water diffusion coefficient. A strong correlation was found between the water absorption and holocellulose content of the composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3907–3911, 2006     

Morphology and properties of polystyrene/agave fiber composites and foams

In this work, agave fibers were blended with polystyrene to produce foamed and unfoamed composites. The effect of fiber size and density reduction on the morphological, thermal, mechanical, and rheological properties, as well as crystallinity and water absorption kinetics of the composites was assessed. The results show that Young's modulus and tensile strength increased with increasing fiber content, but decreased with density reduction. Increasing fiber content and decreasing the size of the fibers both increased crystallinity of the composites. Finally, water uptake and diffusion coefficient were found to increase with increasing fiber content for all sizes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Absorption of steam and water at ambient temperature in wood polymer composites prepared from agro-waste and Novolac

Banana (Musa paradisica), Hemp (Hibiscus cannabinus), and Agave (Agave jourcroydes) fibers were treated with Novolac resin for the formation of their composites in the ratio of 50 : 50 (wt/wt). These fibers were also treated with maleic anhydride, and it was found that composites based on treated fibers showed higher absorption of steam (at 100°C) up to 12 h; and beyond 18 h, it is less than the untreated fiber composites. However, at ambient temperature, the absorption of water is lesser for composites based on maleic anhydride-treated fiber than for composites based on untreated fibers. The SHORE-D hardness was commonly higher for composites based on maleic-anhydride-treated fibers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1417–1421, 1998     

Effect of layering pattern on dynamic mechanical properties of randomly oriented short banana/sisal hybrid fiber–reinforced polyester composites

Dynamic mechanical test methods have been widely employed for investigating the structures and viscoelastic behavior of polymeric materials to determine their relevant stiffness and damping characteristics for various applications. Randomly oriented short banana/sisal hybrid fiber–reinforced polyester composites were prepared by keeping the volume ratio of banana and sisal 1 : 1 and the total fiber loading 0.40 volume fraction. Bilayer (banana/sisal), trilayer (banana/sisal/banana and sisal/banana/sisal), and intimate mix composites were prepared. The effect of layering pattern on storage modulus (E′), damping behavior (tan δ), and loss modulus (E″) was studied as a function of temperature and frequency. Bilayer composite showed high damping property while intimately mixed and banana/sisal/banana composites showed increased stiffness compared to the other pattern. The Arrhenius relationship has been used to calculate the activation energy of the glass transition of the composites. The activation energy of the intimately mixed composite was found to be the highest. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2168–2174, 2005     

Absorption of water at ambient temperature and steam in wood–polymer composites prepared from agrowaste and polystyrene

Hemp, banana, and agave fibers were employed for the preparation of wood–polymer composites using polystyrene in the ratio of 50 : 50 w/w. These fibers were esterified with maleic anhydride (MA) and the effect of MA was studied on the absorption of water at ambient temperature and steam in wood–polymer composites made from said fibers and polystyrene. The absorption of water increases with increase in time from 2 to 30 h in all fiber composites. The maximum absorption of water was found in hemp fiber composites, and the minimum in agave fiber composites. The MA-esterified fiber composites showed less absorption of water than did the untreated fiber composites. Steam absorption in MA-treated and untreated fiber composites is higher than the water absorption in the respective fiber composites. Untreated fiber composites show more absorption of steam in comparison to MA-treated fibers composites. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 681–686, 1998     

Environmental durability of banana‐fiber‐reinforced phenol formaldehyde composites

We explored the environmental aging behavior of banana‐fiber‐reinforced phenol formaldehyde (PF) composites. The composites were subjected to water aging, thermal aging, soil burial, and outdoor weathering. The effects of chemical modification and hybridization with glass fibers on the degradability of the composites in different environments were analyzed. The extent of degradation was measured by changes in the weight and tensile properties after aging. Absorbed water increased the weight of water‐aged composites, and chemical treatments and hybridization decreased water absorption. The tensile strength and modulus of the banana/PF composites were increased by water aging, whereas the strength and modulus of the glass/PF composites were decreased by water aging. As the glass‐fiber loading was increased in the hybrid composites, the increase in strength by water aging was reduced, and at higher glass‐fiber loadings, a decrease in strength was observed. The tensile properties of the composites were increased by oven aging. The percentage weight loss was higher for soil‐aged samples than for samples weathered outdoors. The weight loss and tensile strength of the glass/PF composites and banana/glass/hybrid/PF composites were much lower than those of the banana/PF composites. Silane treatment, NaOH treatment, and acetylation improved the resistance of the banana/PF composites on outdoor exposure and soil burial. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2521–2531, 2006     

Swelling of glass‐fiber reinforced polyamide 66 during conditioning in water,ethylene glycol,and antifreeze mixture

The weight and dimensional changes of injection‐molded glass‐fiber reinforced polyamide 66 composites based on two glass fiber products with different sizing formulations and unreinforced polymer samples have been characterized during conditioning in water, ethylene glycol, and a water‐glycol mixture at 50°C and 70°C for a range of times up to 900 h. The results reveal that hydrothermal ageing in these fluids causes significant changes in the weight and dimensions of these materials. All conditioned materials showed a time dependent weight and dimension increase. The change observed in water could be well modeled by a simple Fickian diffusion process; however, the absorption process followed a more complex pattern in the other conditioning fluids. It was not apparent that changing the glass fiber sizing affected the dimensional stability of the composites under these relatively mild conditions. There was a strong correlation between the swelling of these samples and the level of fluid absorption. The composites exhibited highly aniosotropic levels of swelling. These effects were well in line with the influence of fibers on restriction of the matrix deformation in the fiber direction. The polymer and composite swelling coefficients correlated well with data previously obtained at higher conditioning temperatures. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Effect of layering pattern on the physical,mechanical, and thermal properties of jute/bagasse hybrid fiber‐reinforced epoxy novolac composites

In this study, randomly oriented short jute/bagasse hybrid fiber‐reinforced epoxy novolac composites were prepared by keeping the relative volume ratio of jute and bagasse of 1:3 and the total fiber loading 0.40 volume fractions. The effect of jute fiber hybridization and different layering pattern on the physical, mechanical, and thermal properties of jute/bagasse hybrid fiber‐reinforced epoxy novolac composites was investigated. The hybrid fiber‐reinforced composites exhibited fair water absorption and thickness swelling properties. To investigate the effect of layering pattern on thermomechanical behavior of hybrid composites, the storage modulus and loss factor were determined using dynamic mechanical analyzer from 30 to 200°C at a frequency of 1 Hz. The fracture surface morphology of the tensile samples of the hybrid composites was performed by using scanning electron microscopy. The morphological features of the composites were well corroborated with the mechanical properties. Thermogravimetric analysis indicated an increase in thermal stability of pure bagasse composites with the incorporation of jute fibers. The incorporation of hybrid fibers results better improvement in both thermal and dimensional stable compared with the pure bagasse fiber composites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

The Compatibilizing Effect of Maleic Anhydride on Swelling Properties of Plant-Fiber-Reinforced Polystyrene Composites

In this work the fibers of banana, hemp, and sisal are employed as fillers for the formation of wood polymer composites with polystyrene in the different ratios of 40:60 and 45:55 (wt/wt), respectively. These fibers were esterified with maleic anhydride, and the effect of maleic anhydride was studied on absorption of steam and water at ambient temperature in wood polymer composites. Untreated fiber composites show more absorption of steam in comparison to maleic anhydride (MA)–treated fiber composites. The absorption of water increases with the increase in time from 2–30 h in all untreated fiber composites. The maximum absorption of water was found in hemp fiber composites and the minimum in sisal fiber composites. The maleic anhydride esterified fiber composites showed less absorption of water than the untreated fiber composites. Steam absorption in MA treated and untreated fiber composites is higher than the water absorption in respective fiber composites. The wood polymer composites containing low amount of fiber shows less absorption of steam and water at ambient temperature than the composites containing a greater amount of fiber in respective fiber composites.     

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     

Phthalonitrile-carbon fiber composites

Phthalonitrile polymers offer promise as matrix materials for advanced composite applications. The phthalonitrile monomer is readily converted to a highly crosslinked thermosetting polymer in the presence of thermally stable organic amine catalysts. Rheometric studies were conducted to elucidate the optimum amine concentration for composite formulations. High quality composite panels were processed in an autoclave using unsized IM7 carbon fibers. Mechanical properties of the phthalonitrile/carbon composite are either better than or comparable to the state-of-the-art PMR-15 composites. Dynamic mechanical analysis reveal that samples postcured at elevated temperatures (375°C) do not exhibit a glass transition temperature up to 450°C and also retain °90% of their initial modulus at 450°C. Flame resistance of phthalonitrile/carbon composites, evaluated by cone calorimetric studies, excels over that of other polymeric composites for marine applications. The composites also show low water uptake, <1% after exposure to water for 16 months.     

Effect of the fiber orientation on the sorption kinetics of seawater in an epoxy/glass composite: A free-volume microprobe study

The conventional gravimetric method and positron lifetime spectroscopy have been used to investigate the effect of glass fiber orientation on the diffusion behavior of seawater in epoxy-based composite samples with glass fiber orientations of 0 and 45°. The equilibrium mass uptake of seawater in 45 and 0° orientation composites has been found to be 2.77 and 1.57%, respectively. The diffusion process is non-Fickian in a 45° fiber oriented composite, whereas it is Fickian in a 0° oriented composite. Free-volume data for 45° fiber oriented composites indicates swelling upon the sorption of seawater leading to structural relaxation, and hence the diffusion becomes non-Fickian. On the other hand, a 0° fiber orientation sample exhibits no swelling, and this suggests that water diffusion to the fiber–resin interface through the resin matrix is impeded by the large number of bonds. A polymer–fiber interaction parameter determined from these results also further supports the idea that interface interaction in a 45° fiber oriented composite is less than that in a 0° fiber oriented composite. Positron and gravimetric results support this argument. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of fiber orientation and fiber content on properties of sisal‐jute‐glass fiber‐reinforced polyester composites

The incorporation of natural fibers with polymer matrix composites (PMCs) has increasing applications in many fields of engineering due to the growing concerns regarding the environmental impact and energy crisis. The objective of this work is to examine the effect of fiber orientation and fiber content on properties of sisal‐jute‐glass fiber‐reinforced polyester composites. In this experimental study, sisal‐jute‐glass fiber‐reinforced polyester composites are prepared with fiber orientations of 0° and 90° and fiber volume of sisal‐jute‐glass fibers are in the ratio of 40:0:60, 0:40:60, and 20:20:60 respectively, and the experiments were conducted. The results indicated that the hybrid composites had shown better performance and the fiber orientation and fiber content play major role in strength and water absorption properties. The morphological properties, internal structure, cracks, and fiber pull out of the fractured specimen during testing are also investigated by using scanning electron microscopy (SEM) analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42968.     

Water absorption properties of phosphate glass fiber‐reinforced poly‐ϵ‐caprolactone composites for craniofacial bone repair

The moisture uptake of polymers and composites has increasing significance where these materials are specified for invasive, long‐term medical applications. Here we analyze mass gain and the ensuing degradation mechanisms in phosphate glass fiber reinforced poly‐?‐caprolactone laminates. Specimens were manufactured using in situ polymerization of ?‐caprolactone around a bed of phosphate glass fibers. The latter were sized with 3‐aminopropyltriethoxysilane to control the rate of modulus degradation. Fiber content was the main variable in the study, and it was found that the moisture diffusion coefficient increased significantly with increasing fiber volume fraction. Diffusion, plasticization, and leaching of constituents appear to be the dominant aspects of the process over these short‐term tests. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008