Thermomechanical and crystallization behavior of polylactide-based flax fiber biocomposites

In this work, the rheological, thermal and mechanical properties of melt-compounded flax fiber-reinforced polylactide composites were investigated. The effect of compounding on fiber length and diameter, and the relationship between fiber content and the crystallization behavior of the biocomposites, at various temperatures, were also examined. After melt-compounding, fiber bundles initially present were, to a large extent, broken into individual fibers and the fiber length was decreased by 75 %, while the aspect ratio was decreased by nearly 50 %. The crystallization half-time was found to decrease with increasing flax fiber content, and showed a minimum value at 105 °C for all systems. The elastic modulus was increased by 50 % in the presence of 20 wt% flax fibers. The addition of maleic anhydride-grafted polylactide had a positive effect on the mechanical properties of the biocomposite. This system is particularly interesting in the context of sustainable development as it is entirely based on renewable resources and biodegradable.     

Evaluation of activation energy conformity derived from model-free non-isothermal predictions and Arrhenius isothermal results

Organically modified montmorillonite (OMMT) was used as synergist to enhance the flame-retardant and mechanical properties of poly(butylene succinate)/intumescent flame retardant (PBS/IFR) composites. The flame-retardant, thermal degradation and combustion properties of PBS and its flame-retardant composites were characterized by limiting oxygen index (LOI) test, vertical burning (UL-94) test, thermogravimetric analysis, cone calorimeter and scanning electron microscopy, respectively. The results indicate that PBS/IFR composites exhibit excellent flame retardance when OMMT is at an appropriate content. PBS/IFR composite with 20 wt% IFR and 1.5 wt% OMMT has an LOI of 40.1% and can pass the UL-94 V0 rating. The synergistic effect between OMMT and IFR on the flame-retardant properties of PBS depends on the content of OMMT, and excessive OMMT diminish this synergistic effect. The possible flame-retardant mechanism of OMMT on PBS/IFR composite is proposed. The results of mechanical test also indicate that OMMT can effectively increase the notched impact strength of PBS/IFR composites.     

Effect of sepiolite fiber on the structure and properties of the sepiolite/silica aerogel composite

Sepiolite fiber-reinforced silica aerogel composites for thermal insulators were prepared by dispersing sepiolite fiber in silica sol, aging, solvent exchanging, and drying in supercritical fluid. The surface treated sepiolite fiber and sepiolite/silica aerogel composite were characterized by scanning electron microscope; transmission electron microscope and Fourier transform infrared spectroscopy. The influence of surface treated sepiolite fiber on the mechanical and thermal properties of the aerogel composite was studied. The results indicate the hydroxyl groups on silica sol particles surface able to condense with the hydroxyls of sepiolite fibers with forming Si–O–Si between sepiolite fibers and aerogel matrix in the sol–gel process, which achieves excellent interfacial interaction in the sepiolite/silica aerogel composite, so the mechanical properties of the aerogel composite have been improved effectively without sacrificing much thermal insulating performance.     

Improving hydrophobicity and compatibility between kenaf fiber and polymer composite by surface treatment with inorganic nanoparticles

Compatibility of natural fiber with hydrophobic matrix is a herculean task in literature works. Surface treatment is a well-known approach for increasing the strength of interfacial adhesion between fibres and polymer matrices. Therefore, this study aims to examine the impact of surface treatment with zinc oxide nanoparticles (ZnONPs) in improving hydrophobicity of kenaf fiber (KF) to enhance the compatibility between KF and polymer matrix. In this study, KF reinforced unsaturated polyester composites (KF/UPE) were fabricated by the hand lay-up method with varying fiber loadings (wt %) of 10 20, 30, and 40. KF were treated with five different contents of ZnONPs (1% to 5 wt%) to make UPE/KF-ZnONPs composites. The composites were studied in terms of wetting response (contact angle measure and water absorption), mechanical properties, chemical structure (FTIR), crystalline structure (XRD), and surface morphology (SEM, AFM). The investigational findings indicate that the composite samples incorporating ZnONPs exhibit optimum hydrophobicity and mechanical properties, as they possessed a higher contact angle than the untreated KF composite. The optimum content of ZnONPs was found to be 2 wt%. Regarding water absorption, the untreated UPE/KF composites absorbed more water than the treated UPE/KF-ZnONPs composites. SEM images showed changes in the morphology of the KF, while FTIR analysis proved the presence of ZnONPs functional groups in the UPE/KF composites. AFM images revealed that the ZnONPs could actively produce nanolevel roughness, advantageous to the hydrophobic characteristics.     

In situ Formation of Mildly Oxidized Graphene Oxide/Polydicyclopentadiene Composite and Reinforced Mechanical and Thermal Performances

A series of mildly oxidized graphene oxide (MOGO) reinforced polydicyclopentadiene composites (MOGO/polyDCPD) were prepared via the in situ polymerization of DCPD in the presence of MOGO using ring-opening metathesis polymerization (ROMP). The inter-crosslinking networks between MOGO and polyDCPD backbones formed the reinforced composite structures, examined qualitatively by swelling tests. Bending tests, DMA and TGA measurements were employed to study the optimal loading content of MOGO for achieving the best mechanical and thermal properties of MOGO/polyDCPD composites. The results showed that the maximum mechanical performance was achieved with 0.1 wt% of MOGO loading. Excess MOGO led to decreased mechanical properties due to the poor solubility and uneven distribution of MOGO in the polymer matrix, which was confirmed by SEM. Meanwhile, the thermal stability of MOGO/polyDCPD composites showed a similar trend. The decomposition temperature at 10 wt% weight loss was significantly increased compared with the unfilled polyDCPD, but decreased with composition of MOGO above 0.1 wt%. The addition of MOGO may not only inhibit the back-biting from the catalyst and the formation of low molecular weight oligomers in the polymer, but also covalently immobilize them on its flake.     

Rheological,morphological and mechanical properties of flax fiber polypropylene composites: influence of compatibilizers

In this work, the rheological, mechanical and morphological properties of flax fiber polypropylene composites were investigated. The effect of incorporating a polypropylene grafted acrylic acid or a polypropylene grafted maleic anhydride on these properties has been studied as well. According to scanning electron microscopic observations and tensile tests, the addition of a compatibilizer improved the interfacial adhesion between the flax fibers and the polymer matrix. The tensile modulus of composite containing 30 wt% flax fibers was improved by 200 % and the tensile strength improved by 60 % in comparison with the neat PP. Plasticizing effect of the compatibilizers as a result of their lower melt flow index was also shown to decrease the rheological properties of the composites, even though the effect was not pronounced on the mechanical properties.     

Novel fiber reinforced bismaleimide/diallyl bisphenol A/microcapsules composites

Three kinds of poly(urea‐formaldehyde) (PUF) microcapsules filled with epoxy resins (MCEs) were applied to bismaleimide (BMI)/O,O′‐diallyl bisphenol A (BA) system to develop novel fiber reinforced BMI/BA/MECs composites. The effects of MCEs on the mechanical properties, the hot‐wet resistance, and the dynamic mechanical properties of fiber reinforced BMI/BA composites were investigated. The morphologies of fiber reinforced BMI/BA/MCEs composites were characterized by scanning electron microscope (SEM) and optical microscope (OM). Results indicate that the appropriate contents of MCEs can significantly improve the mechanical properties and the hot‐wet resistance of fiber reinforced BMI/BA composites. In this study, MCEs may decrease the storage modulus of fiber reinforced BMI/BA composite but they have no significant influence on the glass transition temperature (T_g) of the composite. Copyright © 2010 John Wiley & Sons, Ltd.     

Extraction and characterization of alkali-treated red coconut empty fruit bunch fiber

This article discusses the extraction and characterization of new natural fiber extracted from red coconut empty fruit bunch. The physicochemical, mechanical, and thermal properties of alkali-treated red coconut empty fruit bunch fibers (ARCEFBFs) were reported and compared with other natural fibers for the first time. Cellulose content (65.02 wt%), wax (0.32 wt%), density (1.421 g/cc), and tensile strength (1299.49 MPa) were identified in ARCEFBFs. Fourier transform infrared spectroscopy and X-ray diffraction analysis confirmed that ARCEFBFs are rich in cellulose content with crystallinity index of 53.6%. Thermogravimetric analysis revealed that these fibers are thermally stable until 270.48°C.     

Mechanical and morphological properties of injection-molded rice husk polypropylene composites

In this work, the investigation of the physical, mechanical, and morphological properties of the rice husk flour/polypropylene composites was performed utilizing various filler loadings and coupling agent. Five levels of filler loading (35, 40, 45, 50, and 55 wt%) were designed. In addition, to help the interaction between fiber and polypropylene matrix, struktol coupling agent was added to the composites. All of tensile strength, Young's modulus, flexural strength, flexural modulus, and impact strength properties of the composites were carried out. Moreover, the 50 wt% filler-loaded composites had optimum tensile strength, flexural strength, and flexural modulus, whereas the 35 wt% of filler loading case was the best regarding Young's modulus, flexural strength, flexural modulus, and impact strength. Furthermore, the scanning electron microscope results demonstrate that as filler loading increases, more voids and fiber pullout occur.     

The effect of fiber content on the mechanical and thermal expansion properties of biocomposites based on microfibrillated cellulose

A new method to obtain composites of phenolic resin reinforced with microfibrillated cellulose with a wide fiber content was established and the mechanical properties were evaluated by tensile test. A linear increase in Young’s modulus was observed at fiber contents up to 40 wt%, with a stabilizing tendency for higher fiber percentages. These results were ratified by measurements of the coefficient of thermal expansion (CTE) relative to fiber content, which indicated a strong thermal expansion restriction rate below 60 wt% fiber content, indicating the effective reinforcement attained by the cellulose microfibrils. The low CTE achieved of 10 ppm/K is one of the important properties of cellulose composites.     

Mechanical,dynamic mechanical,and thermal analysis of Shorea robusta-dispersed polyester composite

The influence of Shorea robusta natural filler loading (5, 10, 15, 20, and 25 v/v%) on the mechanical, dynamic mechanical, biodegradability, and thermal stability of the polyester composite was analyzed. The composites were fabricated using hand lay-up method. The maximum mechanical properties, storage modulus, and glass transition temperature were observed for the composite with 20 v/v% filler. The peak height of Tanδ was found to be lesser for the same. Thermal analysis results revealed that the thermal stability of composite increased with the incorporation of Shorea robusta as natural filler. Biodegradability testing showed that the addition of filler resulted in weight loss of the composite under soil burial test.     

Physicochemical properties of new cellulosic Artisdita hystrix leaf fiber

The characterization of new natural fiber is increasing due to its excellent properties. This drives investigators to create high performance composites. The present investigation was designed to study the physicochemical properties of fibers obtained from the leaf of the Artistida hystrix. The Artistida hystrix fibers (AHFs) had crystallinity index (44.85%), cellulose (59.54 wt%), hemicellulose (11.35 wt%), lignin (8.42 wt%), and density (540 kg m^?3). The tensile strength of AHFs was 440 ± 13.4 MPa with an average strain rate of 1.57 ± 0.04%. The calculated microfibril angle of AHFs was 12.64 ± 0.45°, which influenced the mechanical properties.     

Experimental investigation on the mechanical properties of Cyperus pangorei fibers and jute fiber-based natural fiber composites

The present era uses natural fibers as a partial replacement for synthetic fibers, thereby utilizing eco-friendly materials in a number of automotive applications (namely, bumpers, wind shields, doors, ceilings, etc.). Although there are many research findings related to natural fiber composites, in this work, a new sandwich layer of Cyperus pangorei fibers and jute fiber epoxy hybrid composites is developed using the hand lay-up technique and compared with the pure Cyperus pangorei fiber and pure jute fiber epoxy composites. The mechanical properties like tensile, flexural, compressive, impact, and hardness are performed as per ASTM standards for the developed composites. The test results show that Cyperus pangorei hybrid composite 3 had a tensile strength of 50.2 MPa, flexural strength of 301.48 N mm^?2, ultimate compression load of 15.03 KN, impact energy of 6.34 J, and Shore D hardness of 82.7, which are superior by 1.1–1.5 times to all the other developed composites. The microstructural characterizations are performed using scanning electron microscope which played a vital role in analyzing the failure morphology of the composites.     

The effect of granite powder on mechanical,structural and water absorption characteristics of alkali treated cordia dichotoma fiber reinforced polyester composite

Environmental and societal concerns such as pollution, disposal of solid waste, requirement of different conflicting properties for materials in varied applications and cost are the main reasons for the development of new materials from the existing materials. The concerns may possibly be overcome by substituting natural fibers for synthetic fibers. In this study, a hybrid composite was developed by reinforcing the natural fiber “cordia dichotoma” and filler “granite powder” into polyester resin. This composite was fabricated using hand lay-up method. Cordia dichotoma fibers were surface treated with NaOH for reducing the hydrophilic nature of the fiber. Unused industrial waste in the form of granite powder obtained from the granite polishing industry is utilized as reinforcement in polymer composite. The hybrid composite was prepared by reinforcing a constant cordia dichotoma fiber content of 20 wt % and varying the granite powder weight (wt. %) percentages (0, 5, 10, 15, and 20) into polyester resin. Mechanical properties (tensile, flexural and impact) of hybrid composites were investigated. The novelty of this work lies in utilization of granite powder sourced from industrial waste utilized as filler material. Granite, as one of the hard materials, may improve wear and other mechanical properties. Following the results obtained, granite powder could be evidenced as a good filler material for the betterment of composites mechanical properties. Also, the ability of this filler material is proved in decreasing water absorption and chemical resistance. Scanning electron microscope (SEM) analysis was performed to investigate the bonding and distribution of granite powder within both the fiber as well as resin in the composite. Besides, the presence of chemical functional groups in the composite was traced by Fourier transform Infrared spectroscopy (FTIR). Also, Thermo-gravimetric analysis (TGA) was carried out and the composite was found to be thermally stable up to 415 °C.     

Nanoclay modified silica phenolic composites: mechanical properties and thermal response under simulated atmospheric re‐entry conditions

Ablative nanocomposites based on nanoclay‐dispersed addition curable propargylated phenolic novolac (ACPR) resin, reinforced with chopped silica fiber, were investigated for their thermal response behavior under simulated heat flux conditions corresponding to typical atmospheric re‐entry conditions. Organically modified nanoclay (Cloisite 30B) was incorporated to different extents (1–10%) in the ACPR resin matrix containing silica fiber to form the composite. The composites displayed optimum mechanical properties at around 3 wt% of nanoclay loading. The resultant composites were evaluated for their ablative characteristics as well as mechanical, thermal and thermo‐physical properties. The reinforcing effect of nanoclay was established and correlated to the composition. The mechanical properties of the composites and its pyrolysed product improved at moderate nanoclay incorporation. Plasma arc jet studies revealed that front wall temperature is lowered by 20°C and that at backwall by 10–13°C for the 3 wt% nanoclay‐incorporated composites due to impedance by nanoclay for the heat conduction. Nanoclay diminished the coefficient of thermal expansion by almost 50% and also reduced the flammability of the composites. The trend in mechanical properties was correlated to the microstructural morphology of the composites. The nanomodification conferred better strength to the pyrolysed composites. Copyright © 2014 John Wiley & Sons, Ltd.     

Impact of surface adaptation and Acacia nilotica biofiller on static and dynamic properties of sisal fiber composite

Nowadays, the awareness of the public along with strict legitimate forces over the use of polymers, the manufacturing and automotive industries started using the renewable materials. Since, natural fiber reinforced composites play vital role in developing lightweight structural materials, this study focuses on utilizing sisal fiber as reinforcement in polyester matrix along with natural filler. The influence of fiber length and fiber volume fraction on the mechanical properties of sisal fiber was studied initially. Test results revealed that the composite with 20?mm fiber length and 20-volume fraction composite has better mechanical properties. Furthermore, the effect of fiber surface modification has been analyzed using various chemical solutions such as NaOH, KMnO₄, stearic acid, and maleic acid. Of these, NaOH treatment enhances the mechanical properties of composite compared to all other cases. Finally, the influence of Acacia nilotica, a natural filler addition into the alkali-treated sisal fiber composite has been evaluated by mechanical and dynamic mechanical properties. It is found that the addition of natural filler and surface treatment has enhanced the properties of composites due to their synergetic effect. This effect improves the adhesion and uniform stress transfer among the reinforcements. The fiber surface morphology was evaluated using micrographs obtained from scanning electron microscope.     

Characterization of new natural cellulosic fiber from the Perotis indica plant

This investigation summarizes the characteristics of biofiber extracted from the Perotis indica plant. Cellulose content (68.4 wt%), density (785 kg m^?3), crystallinity index (48.3%), tensile strength (317–1,608 MPa), and Young’s modulus (8.41–69.61 GPa) properties were identified in the P. indica fibers (PIFs), and thermal stability was studied using thermal gravimetric analysis and derivative thermogravimetric analysis, which revealed its cellulose degradation at a temperature of 339.1°C. Further, the properties of PIFs ensured that it can play an imperative role as new reinforcement as green composites in the manufacturing industries.     

The role of organoclay on the properties of Polymethylsilsesquioxane: A systematic study

In this study, an attempt is made to improve the properties of PMSQ, an organosilicone polymer which possesses distinguished properties, through an easy and facile route by the inclusion of organically modified montmorillonite clay. PMSQ-clay composites were prepared by solution blending of the components initially and then heat curing under load. The effect of clay content, varied at 5–40 wt.%, on mechanical, thermal and dynamic mechanical properties was evaluated and the optimum was obtained for 20%. Morphology investigation as well as microstructure analysis revealed intercalated to exfoliated morphology of PMSQ-clay composite. An appreciable improvement in mechanical properties of PMSQ, compressive strength and impact strength in particular, was achieved by clay inclusion up to 20%. The properties declined at ≥ 30% clay loading. The composites showed increased thermal stability compared to unmodified PMSQ up to 400 °C. Also, increase in clay content accelerated conversion to ceramic SiOC. PMSQ-clay composites exhibited good visco-elastic characteristics with higher T_g probably due to enhanced polymer-clay interactions. Thus, a simple and viable method to enhance the mechanical and thermal characteristics of PMSQ by way of preparing its composite with the reinforcing filler organoclay is demonstrated here.     

Development of continuous process enabling nanofibrillation of pulp and melt compounding

Microfibrillated cellulose (MFC), a mechanically fibrillated pulp mostly consisting of nanofibrils, is a very attractive material because of its high elastic modulus and strength. Although much research has been done on composites of MFC and polypropylene (PP), it has been difficult to produce such composites at an industrial level because of the difficulties in using MFC in such composites are not only connected to the polarity (that can be improved with compatibilizers), but also with the challenge to make a homogeneous blend of the components, and also the low temperature stability of cellulose that could cause problems during processing. We developed a new processing method which enables continuous microfibrillation of pulp and its melt compounding with PP. Never-dried kraft pulp and powdered PP were used as raw materials to obtain MFC by kneading via a twin-screw extruder. Scanning electron microscopy showed nano to submicron wide fibers entangled in the powdered PP. MFC did not aggregate during the melt compounding process, during which the water content was evaporated. Maleic anhydride polypropylene (MAPP) was used as a compatibilizer to reinforce interfacial adhesion between the polar hydroxyl groups of MFC and non-polar PP. We investigated the effect of MAPP content on the mechanical properties of the composite, which were drastically improved by MAPP addition. Needle-leaf unbleached kraft pulp (NUKP)-derived MFC composites had better mechanical properties than needle-leaf bleached kraft pulp (NBKP)-derived MFC composites. Injection molded NUKP-derived MFC composites had good mechanical and thermal properties. The tensile modulus of 50 wt% MFC composite was two times, and the tensile strength 1.5 times higher than that of neat PP. The heat distortion temperature of 50 wt% MFC content composite under 1.82 MPa flexural load was increased by 53 °C, from 69 to 122 °C. This newly developed continuous process using powder resin has the potential for application at an industrial level.     

Completely biodegradable composites of poly(propylene carbonate) and short,lignocellulose fiber Hildegardia populifolia

The composites of biodegradable poly(propylene carbonate) (PPC) reinforced with short Hildegardia populifolia natural fiber were prepared by melt mixing followed by compression molding. The mechanical properties, thermal properties, and morphologies of the composites were studied via static and dynamic mechanical measurements, thermogravimetric analysis, and scanning electron microscopy (SEM) techniques, respectively. Static tensile tests showed that the stiffness and tensile strength of the composites increased with an increasing fiber content. However, the elongation at break and the energy to break decreased dramatically with the addition of short fiber. The relationship between the experimental results and the compatibility or interaction between the PPC matrix and fiber was correlated. SEM observations indicated good interfacial contact between the short fiber and PPC matrix. Thermogravimetric analysis revealed that the introduction of short Hildegardia populifolia fiber led to a slightly improved thermooxidative stability of PPC. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 666–675, 2004