Effect of alkali treatment on properties of unidirectional isora fibre reinforced epoxy composites

Abstract

Unidirectional isora fibre reinforced epoxy composites were prepared by compression moulding. Isora is a natural bast fibre separated from Helicteres isora plant by retting process. The effect of alkali treatment on the properties of the fibre was studied by scanning electron microscopy (SEM), IR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Mechanical properties such as tensile strength, Young's modulus, flexural strength, flexural modulus and impact strength of the composites containing untreated and alkali treated fibres have been studied as a function of fibre loading. The optimum fibre loading for tensile properties of the untreated fibre composite was found to be 49% by volume and for flexural properties the loading was optimised at ～45%. Impact strength of the composite increased with increase in fibre loading and remained constant at a fibre loading of 54·5%. Alkali treated fibre composite showed improved thermal and mechanical properties compared to untreated fibre composite. From dynamic mechanical analysis (DMA) studies it was observed that the alkali treated fibre composites have higher E' and low tan δ maximum values compared to untreated fibre composites. From swelling studies in methyl ethyl ketone it was observed that the mole percentage of uptake of the solvent by the treated fibre composites is less than that by the untreated fibre composites. From these results it can be concluded that in composites containing alkalised fibres there is enhanced interfacial adhesion between the fibre and the matrix leading to better properties, compared to untreated fibre composites.     

Effect of storage on ultraviolet irradiated HDPE

Abstract

Oxygen containing groups such as C=O and C–O were introduced onto high density polyethylene (HDPE) chains by ultraviolet (irradiated at 70°C and different light intensities in air). The contents of oxygen containing groups were unchanged after storage, indicating that these groups were stable in HDPE chains. The water contact angles of the irradiated HDPE at different light intensities after storage were equivalent to those of the irradiated HDPE before storage. Small quantity of the irradiated HDPE at different light intensities before and after storage as a compatibiliser were added into the HDPE/CaCO₃ composite respectively, and the HDPE/CaCO₃/irradiated HDPE before and after storage composite were prepared respectively. The tensile strength and the impact strength of HDPE/CaCO₃/irradiated HDPE after storage composite were similar to those of the HDPE/CaCO₃/irradiated HDPE before storage composite. The irradiated HDPE after storage was an efficacious compatibiliser.     

Study of natural aging of industrial low density polyethylene by X-ray photoelectron spectroscopy

Abstract

X-ray photoelectron spectroscopy (XPS) was used to study the natural outside aging of industrial low density polyethylene (LDPE) under the influence of one year round weather. Two types of LDPE were studied. The first type was LDPE without additives and the second type was doped with 4% of hindered amine light stabilisers (HALS). Unstabilised and 4% HALS stabilised LDPE samples underwent an oxidation of the polymeric matrix, by the production of C–O, C=O and O=C–O groups. These chemical functions were observed in high resolution XPS spectra around C1s and O1s peaks. From these results, it was then possible to propose mechanisms of natural aging of LDPE in such conditions. On the other hand, there is no clear evidence that HALS could be effective in natural aging for the polymer surfaces with exposure to the elements.     

Effects of temperature on interlaminar fracture toughness of fibre reinforced plastic composites made by newly proposed rubber pressure moulding technique

Abstract

The present paper has investigated the effect of temperatures (i.e.?70–100°C) on the interlaminar fracture toughness (ILFT) of fibre reinforced plastic (FRP) composite panels made by a recently developed process known as the rubber pressure moulding (RPM) technique. The RPM technique is based on the matching die set, where the die is made of hard metal like steel and the punch from flexible rubber like materials. The use of flexible rubber punch helps to intensify and uniformly redistribute pressure (both operating pressure and developed hydrostatic pressure due to the flexible rubber punch) on the surface of the product. Natural rubber was used to prepare rubber punch in this investigation. For performance evaluation of FRP composites made by the RPM technique, FRP composites were also made by conventional method and tested at the same temperatures. It is observed that Mode I ILFT of FRP composites decreases towards higher and lower extremes of the temperature range selected. FRP composites made by the RPM technique show a higher Mode I ILFT over the 25–100°C temperature range than those made by the conventional process.     

Studies on thermal,mechanical, morphological,and viscoelastic properties of polybenzimidazole fiber reinforced high density polyethylene composites

High density polyethylene (HDPE) and polybenzimidazole fiber (PBI) composites were prepared by melt blending in a twin screw extruder. The thermomechanical properties of PBI fiber reinforced HDPE composite samples (1%, 4%, and 8%) of fiber lengths 3 mm and 6 mm were investigated using differential scanning calorimeter (DSC), universal testing machine, rheometer, and scanning electron microscopy (SEM). The effects of fiber content and fiber lengths on the thermomechanical properties of the HDPE‐PBI composites were studied. The DSC analysis showed a decrease in crystallinity of HDPE‐PBI composites with an increase of fiber loading. SEM images revealed homogeneous distribution of the fibers in the polymer matrix. The thermal behavior of the composites was evaluated from thermogravimetric analysis and the thermal stability was found to increase with the addition of fibers. The evidence of homogeneous distribution was verified by the considerably high values of tensile strength and flexural strength. In the rheology study, the complex viscosities of HDPE‐PBI composites were higher than the HDPE matrix and increased with the increasing of PBI fiber loading. POLYM. COMPOS., 5–13, 2016. © 2014 Society of Plastics Engineers     

Processability,morphology and mechanical properties of wood flour reinforced high density polyethylene composites

Abstract

Wood flour reinforced high density polyethylene (HDPE) composites have been prepared and their rheological properties measured. The melt viscosity decreased as the processing temperature increased and the wood flour content decreased. A power law model was used to describe the pseudoplasticity of these melts. Adding wood flour to HDPE produced an increase in tensile strength and modulus. Composites compounded in a twin screw extruder and treated with a coupling agent (vinyltrimethoxysilane) or a compatibliser (HDPE grafted with maleic anhydride) exhibited better mechanical properties than the corresponding unmodified composites because of improved dispersion and good adhesion between the wood fibre and the polyalkene matrix. Scanning electron microscopy of the fracture surfaces of these composites showed that both the coupling agent and compatibiliser gave superior interfacial strength between the wood fibre and the polyalkene matrix.     

Studies on the comprehensive performance of graphite and additives filled high density polyethylene composites

The comprehensive performance of graphite and additives filled high‐density polyethylene (HDPE) composites is studied in this article. Four graphites with different particle diameters are used as conductive fillers in HDPE/graphite. Plasticizer, nucleator, and certain particle diameter graphite are employed to prepare HDPE composite. The behavior of crystallization and the distribution of graphite are also studied by means of SEM. An orthogonal design experiment is taken to optimize the content of the filler. The experimental results indicate that the positive temperature coefficient (PTC) effect is related to the particle diameter of graphite. And the bending strength of HDPE/graphite composite with the plasticizer and nucleator is two times less than that of HDPE‐graphite blends. Meanwhile, the high PTC intensity (the ratio of peak resistivity to room temperature resistivity) is also preserved. An excellent comprehensive performance conductive composite is prepared. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of nitric acid surface treatment on tensile and tribological properties of thermoplastic polyimide composite filled with carbon fibre

Abstract

Polyacrylonitrile based carbon fibres were submitted to nitric acid oxidation treatments to improve the interfacial adhesion of the carbon fibre reinforced polyimide (CF/PI) composite. The carbon fibre surfaces were characterised by X-ray photoelectron spectroscopy. Nitric acid oxidation not only affects the oxygen concentration, but also produces an appreciable change in the nature of the chemical functions, namely the conversion of hydroxy type oxygen into carboxyl functions. Nitrogen concentration of nitric acid oxidation treated carbon fibre is ～1·2 times higher compared with untreated one. The mechanical and tribological properties of the CF/PI composites treated with nitric acid oxidation were investigated. Results showed that the tensile strength of the CF/PI composites improved remarkably due to nitric acid treatment along with enhancement in friction and wear performance.     

Effect of fibre length and chemical modifications on the tensile properties of intimately mixed short sisal/glass hybrid fibre reinforced low density polyethylene composites

Hybrid composites prepared by the incorporation of two or more different types of fibres into a single polymer matrix deserve much attention. This method of hybridisation of composites offers a profitable procedure for the fabrication of products while the resulting materials are noted for their high specific strength, modulus and thermal stability. The influence of the relative composition of short sisal/glass fibres, their length and distribution on the tensile properties of short sisal/glass intimately mixed polyethylene composites (SGRP) was examined. Different compositions of sisal and glass such as 70/30, 50/50 and 30/70 have been prepared with varying fibre lengths in the range of 1–10 mm. Emphasis has also been given to the variation of fibre–matrix adhesion with several fibre chemical modifications. Chemical surface modifications such as alkali, acetic anhydride, stearic acid, permanganate, maleic anhydride, silane and peroxides given to the fibres and matrix were found to be successful in improving the interfacial adhesion and compatibility between the fibre and matrix. The nature and extent of chemical modifications were analysed by infrared spectroscopy while improvement in fibre–matrix adhesion was checked by studying the fractography of composite samples using a scanning electron microscope. Assessment of water retention values has been found to be a successful tool to characterize the surface of the stearic acid modified fibres. It was found that the extent of improvement in tensile properties of SGRP varied with respect to the nature of chemical modifications between fibre and matrix. Improved mechanical anchoring and physical and chemical bonding between fibre and polyethylene matrix are supposed to be the reasons for superior tensile strength and Young's modulus in treated composites. Several secondary reasons such as high degree of fibre dispersion and reduced hydrophilicity in chemically modified fibres also are believed to play a role. Among the various chemical modifications, the best tensile strength and modulus was exhibited by the SGRP with benzoyl peroxide treated fibres. This is attributed to the peroxide‐initiated grafting of polyethylene on to the fibres. Copyright © 2004 Society of Chemical Industry     

Flow stress of high density polyethylene and nylon 66 at high rates of strain

Measurement of the flow stress of high density polyethylene (HDPE) and nylon 66 at strain rates of 10³ s^?1 using a split Hopkinson pressure bar technique is discussed. The flow stress at a strain of 10% has been determined for both polymers at 20°C. The intrinsic errors involved in this technique are briefly reviewed. The results indicate that the flow stress of HDPE and nylon 66 were 50MPa and 150MPa, respectively, at strain rates of about 10³s^?1.     

Effect of compatibiliser on rheological behaviour of straw fibre/low density polyethylene composites

Abstract

Rheological behaviour of suspensions of straw fibre in low density polyethylene (LDPE) melts was investigated at a certain temperature over a wide range of frequencies using a plate rheometer operated in dynamic mode. The viscoelastic of composite melt changed gradually with the straw fibre content increasing, for example at the low frequency region the slope of the G′ decreased from 1.67 of the plain LDPE to 0.889 of 50?wt-% straw fibre plastic composite. The addition of compatibiliser doubled the tensile strength, and the relaxation time reduced from 405 to 214?s. It was observed that the presence of compatibiliser may be attributed to improve interaction between the polymer and filler, which reduces the resistance of the agglomeration of straw fibres, lessening the relaxation time. Consequently, the straw fibre plastic composite is easier to produce.     

玻璃纤维增强PEEK复合材料成型工艺研究

本文初步探索了玻璃纤维增强聚醚醚酮(PEEK)复合材料的成型工艺．通过力学性能、微观形貌分析等试验,探索了不同工艺参数对玻璃纤维增强PEEK复合材料性能的影响,进而制定了复合材料较优的成型工艺参数．其成型工艺参数包括冷却速度、成型压力、成型温度、保温时间．     

Glass fiber/wood flour modified high density polyethylene composites

Composites of high density polyethylene (HDPE) with the reinforcements of glass fiber (GF) and wood flour (WF) have been studied in this work. High‐density polyethylene‐grafted maleic hydride (HDPE‐g‐MAH) was used as a compatibilizer. In particular, the effect of GF, WF, and HDPE‐g‐MAH on the overall properties of GF/WF/HDPE composites (GWPCs in short form) was systematically studied. The results indicate that HDPE‐g‐MAH as a compatibilizer can effectively promote the interfacial adhesion between GF/WF and HDPE. By the incorporations of GF/WF, the heat deflection temperature can reach above 120°C, and the water absorption can be below 0.7%, also the tensile strength, flexural strength, and impact strength of GWPCs can surpass 55.2 Mpa, 69.4 Mpa, and 11.1 KJ/m², respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Low density polyethylene composites reinforced with Australian King Palm fibers: mechanical and thermal properties

The aim of this work is to obtain and evaluate the mechanical and thermal properties of low Density Polyethylene (LDPE) composites reinforced with fibers from Australian King Palm fibers. Raw fibers were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy. The chemical composition of the fibers was also evaluated. After characterizing the fibers were mixed into the LDPE, in proportions of 5, 10, 15 and 20% (wt/wt) using a thermokinetic mixer model MH-50H. Furthermore tensile, flexural and impact specimens were prepared for evaluation of mechanical properties. The composites were analyzed through SEM micrographs of fractured surfaces and thermal analysis. The results indicate that the reinforcement decreases the thermal stability of the composites, but caused an increase the mechanical properties of the composites. The composites reinforced with of raw fibers 20% (wt/wt) showed significant increase in the tensile strength, flexural and impact.     

Isothermal crystallization of high density polyethylene and nanoscale calcium carbonate composites

High density polyethylene (HDPE) and calcium carbonate (CaCO₃) nanocomposites with maleic anhydride grafted HDPE (manPE) as a compatibilizer were prepared via compounding in a twin‐screw extruder. The CaCO₃ are well dispersed in the HDPE matrix from the observation of transmission electron microscope. The isothermal crystallization kinetics was studied by differential scanning calorimetry and simulated by Avrami and Tobin models. The nucleation constants and fold surface free energy were estimated from Lauritzen–Hoffman relation. The results indicate that both manPE and well‐dispersed CaCO₃ particles would act as nuclei to induce heterogeneous nucleation and enhance crystallization rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Mechanical and thermal properties of coal gasification fine slag reinforced low density polyethylene composites

Coal gasification fine slag (CGFS) was processed via a grading technique. The CGFS products (CGFS‐S1, CGFS‐S2, CGFS‐S3) with different sizes were obtained. Effects of particle size and unburned carbon on tensile properties of filled low density polyethylene (LDPE) were studied within the CGFS weight fractions ranging from 10 to 50 wt %. The tensile strength was found to increase with decreasing CGFS size, and the tensile properties exhibited good performance, owing to unburned carbon. The tensile strength of the composites increased with increasing CGFS‐S3 weight fraction. The analysis of mathematical model and SEM revealed that the firm improvement of tensile strength resulted from the strong interactions between LDPE polymer chains and CGFS‐S3 particles, and good dispersion of CGFS‐S3 in resin. Thermogravimetric analysis proved obvious reinforcement in thermal‐oxidative stability by incorporation of CGFS‐S3. The degree of crystallinity of LDPE/CGFS‐S3 showed the first increased and then decreased variation tendency. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46203.     

Effect of maleic anhydride grafting on nanokaolinclay reinforced polystyrene/high density polyethylene blends

Nanofillers have revolutionized the field of polymer modification. Modification of polymer blends with nanofillers opens up a myriad of opportunities to develop materials of choice. Polystyrene (PS) and high density polyethylene (HDPE) are two widely used standard plastics. To generate high modulus and strength a PS rich blend of PS/HDPE (80/20) was selected and the blend was modified using low cost nanokaolin clay, a 1:1 alumina silicate. The effect of maleic anhydride grafted PS/PE as compatibilizer in this system was studied. The incorporation of the compatibilizer improves the mechanical properties. This can be correlated with better interfacial adhesion as evidenced by scanning electron microscopy. The optimum in these properties was obtained at a compatibilizer concentration of 10–15%. The composites were characterized byX‐ray diffraction, differential scanning calorimetric, and dynamic mechanical analyzer techniques. This study shows that kaolin can be used as potential modifier of PS/HDPE blend. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

Interfacial modification of high density polyethylene/glass fiber reinforced and non reinforced polyamide 66 blends

High density polyethylene (HDPE) and polyamide (PA66) are well known to be incompatible. An ionomer (Surlyn) was added as a compatibilizer to HDPE and glass fiber reinforced (HDPE/GFRPA66) and non‐reinforced (HDPE/PA66) blends. Two compositions were considered: 25/75 wt % and 75/25 wt %, with an emphasis on the former formulation. The influence of the compatibilizer on the rheology, thermal properties, and the morphology, as well as mechanical properties of the blends, was investigated using melt flow index measurements, DSC, scanning electron microscopy (SEM), and impact strength. The ionomer was found to be more effective as a compatibilizer with HDPE as a minor phase compared to the case when HDPE becomes the major phase. The results indicated that the interfacial properties of the blends were improved, with a maximum appearing at a critical concentration of the ionomer (7.5 vol %). At this level of compatibilization, SEM analysis revealed better interfacial adhesion and a finer dispersion. MFI results revealed a probable reaction between the amine groups of PA66 and the acid functions of the ionomer. The mechanical properties support the above results and showed that the addition of 25 wt % HDPE did not affect the properties of PA66 much and the presence of glass fiber did not hinder the effect of the compatibilizer. Only 20% decrease in notched Izod impact strength of the blends is observed at 7.5 vol % ionomer content, suggesting that the addition of 25 wt % of HDPE to PA66 is not detrimental at this level of compatibilization. The emulsification curve was established and revealed that, in terms of impact properties, the finer the particle size, the higher the impact strength corresponding to 7.5 vol % ionomer content. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1748–1760, 2005     

Functionalization of high density polyethylene in melt state through ultrasonic initiation and its effect on mechanical properties of glass fiber reinforced composites

Summary Functionalization reaction of high density polyethylene (HDPE) with γ-methacryloxy-propyltrimethoxysilane (MAS) or with MAS and MAH performed in melt state through ultrasonic initiation by a laboratory-scale ultrasonic extruding reactor was studied in this paper. The effect of ultrasonic intensity on the percentage of grafting and melt flow rate of the functionalized products was investigated. The results show that by imposing ultrasonic vibration during melt-extruding process, the scission of HDPE chain bonds can be caused to form macroradicals, the functionalization reaction of HDPE with MAS or with MAS and MAH can be realized. The percentage of grafting and the melt flow rate of the functionalized products depend upon the ultrasonic intensity and reaction temperature. The fuctionalization reaction of HDPE with MAS can be promoted by adding a second grafting monomer MAH. The ultrasonic-induced products have a higher reactivity with the coupling agents coated on the surface of glass fibers, the mechanical properties of the composite improved by the ultrasonic induced product are higher than that of by peroxide initiated product and the mechanical properties of HDPE/GF composite modified by HDPE-g-MAH-MAS are higher than that of by HDPE-g-MAH. The SEM experimental results indicate that an oriented crystal layer exists between the interface of glass fiber and the HDPE matrix, the interfacial bonding strength is the determining factor of the formation of the oriented crystal layer.     

Studies on high density polyethylene/polycarbonate blend system compatibilized with low density polyethylene grafted diallyl bisphenol A ether

Blends of a high density polyethylene (HDPE) matrix and a polycarbonate (PC) minor phase were investigated through their morphology, heat resistance, mechanical properties, crystallizing behavior, rheological measurement and especially the compatible effect of a compatibilizer: low density polyethylene grafted diallyl bisphenol A ether (LDPE-g-DBAE). The blends without compatibilizer exhibited a phase growth and no adhesive between the HDPE matrix and the dispersed phase. In the presence of 10% by weight of LDPE-g-DBAE as a compatibilizer, more fine particles and a dim phase interface were observed, and the blends showed a remarkable increase in heat distortion temperature and mechanical properties. The compatibilized blends possessed a high apparent viscosity as compared with the noncompatibilized ones. However, the apparent viscosity of the blends, with or without the compatibilizer, was lower than that of the neat HDPE and PC. Exploration by DSC found that the melting point and the crystallinity of HDPE in the blends decreased, and especially for the blends with the compatibilizer. These facts could be interpreted in terms of the efficient compatible effect of the LDPE-g-DBAE, which resulted from the interaction between the diallyl bisphenol A ether unit of LDPE-g-DBAE and polycarbonate, and the miscibility of the LDPE unit and HDPE.