Several works have been based on the study of thermal variations in biomass to derive more valuable products such as fuels capable of replacing oil in the event of a crisis or activated carbon used as an adsorbent mat...Several works have been based on the study of thermal variations in biomass to derive more valuable products such as fuels capable of replacing oil in the event of a crisis or activated carbon used as an adsorbent material, widely used in industry for the elimination of unwanted materials, both in liquid and gaseous environments. A study of thermal parameters such as: heating speed, retention time, drying temperature, carbonization temperature, particle size, was carried out with the aim of determining the characteristic factors of the carbonization of Polyethylene terephthalate (PET), sawdust (SC) and sawdust/polyethylene terephthalate (CPS) mixture. The results of the immediate analysis revealed a very low level of ash in PET (0.013%) compared to the level of ash in sawdust (2.9%), as well as a high level of fixed carbon (82.960%), which suggests the presence of mineral oxides and a significant carbon matrix unlike PET, which indicates a very significant organic matrix (essentially made up of organic matter) with the absence of mineral oxides. The study of thermal parameters showed the water loss from Sawdust (SC) and the Sawdust/Polyethylene terephthalate (CPS) mixture, an increase with temperature, unlike that of PET whose variation is essentially zero. Without heat treatment, sawdust alone contains approximately 7% water. The optimal drying temperature for this study is 110˚C for a stay of 24 hours. It appears that the largest mass losses for the PET samples are between 87.19% and 96.05%, followed by that of the mixture, between 47.33% and 64.37%. And the lowest are observed, those of sawdust (from 24.02% to 62.6%). However, here we can say that the influence of the mass is not great, given the slight difference between the losses by temperature. The results of the study of the influence of grain size showed that the differences are insignificant, even if we vary the diameter of the grains from simple to triple. To better minimize physical constraints such as the intragranular diffusibility of the volatile matter and the homogeneity of the temperature in the grains, 75 μm particles are found to be optimal for our study. It can be noted when studying the heating rate that the mass loss at the end of the reaction is approximately the same depending on each precursor material. However, it has been demonstrated that the heating rate strongly influences the nature of the reaction products both for volatile materials and for the solid residue as well as on the kinetic parameters of the chemical reaction. Furthermore, the variation in apparent density shows a decrease as a function of the increase in the residence time of the materials in the reactor. As the carbonization time increases, the apparent density decreases. We note, for the lignocellulosic material, that the apparent density stabilizes after 60 minutes.展开更多
This study elaborates on the effects of matrix rigidity on the high-velocity impact behaviour of UHMWPE textile composites using experimental and numerical methods.Textile composite samples were manufactured of a plai...This study elaborates on the effects of matrix rigidity on the high-velocity impact behaviour of UHMWPE textile composites using experimental and numerical methods.Textile composite samples were manufactured of a plain-weave fabric(comprising Spectra?1000 fibres)and four different matrix materials.High-velocity impact tests were conducted by launching a spherical steel projectile to strike on the prepared samples via a gas gun.The experimental results showed that the textile composites gradually changed from a membrane stretching mode to a plate bending mode as the matrix rigidity and thickness increased.The composites deformed in the membrane stretching mode had higher impact resistance and energy absorption capacity,and it was found that the average energy absorption per ply was much higher in this mode,although the number of broken yarns was smaller in the perforated samples.Moreover,the flexible matrix composites always had higher perforation resistance but larger deformation than the rigid matrix counterparts in the tested thickness and velocity range.A novel numerical modelling approach with enhanced computational efficiency was proposed to simulate textile composites in mesoscale resolution.The simulation results revealed that stress and strain development in the more rigid matrix composite was localised in the vicinity of the impact location,leading to larger local deformation and inferior perforation resistance.展开更多
High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in lan...High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.展开更多
In-situ composites based on dispersed poly (ethylene terephthalate) (PET) or polyamide (PA), and continuous polyethylene (PE) were prepared through a single screw extruder of Haake rheometer system with a rod-die rela...In-situ composites based on dispersed poly (ethylene terephthalate) (PET) or polyamide (PA), and continuous polyethylene (PE) were prepared through a single screw extruder of Haake rheometer system with a rod-die relatively small in diameter. The extrudate was drawn at a drawing ratio of 3.1, and then quickly cooled in cold water. The specimens were obtained by injection molding at processing temperatures less than 190℃, far below the melting temperature of PET (265℃) and PA (230℃), which can maintain the solid state of PET and PA microfiber phase in the composites. Morphological observation with scanning electron microscopy (SEM) indicated that PET and PA can more or less form in-situ microfibers at compositions studied (0~20 wt pct PET or PA), and especially, PET and PA were almost deformed into fibers at the concentration of 15 wt pct. Tensile strength and modulus of the blends reinforced by PET or PA microfibers showed to be increased from the tensile test results. The most noticeable improvement of the tensile properties occurred at 15 wt pct of PET in PET/PE system, corresponding to the highest microfiber content, where the tensile strength reached 32.5 MPa, whereas only 19.5 MPa for the pure PE.展开更多
A thermogravimetric analysis (TG) was conducted to study the thermal decomposition behavior and kinetics of composites from coal and high density polyethylene (HDPE), linear low density polyethylene (LLDPE) or low den...A thermogravimetric analysis (TG) was conducted to study the thermal decomposition behavior and kinetics of composites from coal and high density polyethylene (HDPE), linear low density polyethylene (LLDPE) or low density polyethylene (LDPE). The results show that coal facilitates melting of the polyethylene before temperatures reach 700 K in nitrogen due to the exothermic effect of coal. Above 700 K, adding coal into the polyethylene will result in smaller maximum rates of mass loss and higher initial mass loss temperatures of the composites. Hence, some chemical interactions, occurring between liquid compounds released in the pyrolysis of the coal and polymer, depend on several factors, such as coal rank and the molecular structure of polymers. Synergetic effects in coal and polymers were also found. Both chemical interactions and synergetic effects control the entire thermal decomposition behavior of compos- ites. The larger the amount of coal in the composites, the greater the decomposition temperature spans and the higher the maximum decomposition temperature, the smaller the devolatilization rates. The effect of coal on the thermal stability of composites lies in the hydrogen acceptor effect of the coals. Thermal decomposition of the coals, the polymers and related composites can be modelled via first order parallel reactions between 563 K and 763 K.展开更多
Quasi-static and high strain rate compressive behaviors and failure mechanisms of hygrothermal treated ultra-high molecular weight polyethylene/polyurethane(UHMWPE/PU)composites have been studied in this paper.Firstly...Quasi-static and high strain rate compressive behaviors and failure mechanisms of hygrothermal treated ultra-high molecular weight polyethylene/polyurethane(UHMWPE/PU)composites have been studied in this paper.Firstly,the UHMWPE composites were immersed in water at 70℃.The out-ofplane compression test was then performed on the dry/wet state specimens at quasi-static states(0.001-0.01 s^(-1))and high strain rate states(800-2 400 s^(-1)).The split Hopkinson pressure bar(SHPB)was adopted in the dynamic tests and waveform shapers were used to smooth and control the incident pulse.The results show that there are two platforms for the water absorption curve of UHMWPE composites.The absorption of moisture reduces the quasi-static compressive strength of the material while initially increasing,then decreasing the dynamic compressive strength.Matrix plasticization,fiber/matrix interface degradation and void expansion are the main factors affecting the irregular change of static/dynamic compressive strength of UHMWPE composites.展开更多
The in-plane compressive characteristics of the ultra-high molecular weight polyethylene(UHMWPE)fibre(Dyneema█)reinforced composites,both in 0/90°and±45°fibre orientations with respect to the loading d...The in-plane compressive characteristics of the ultra-high molecular weight polyethylene(UHMWPE)fibre(Dyneema█)reinforced composites,both in 0/90°and±45°fibre orientations with respect to the loading direction,have been investigated.The composite made from unidirectional high modulus fibres(volume fraction 83%)and low strength polyurethane matrix(volume fraction 17%)is layered in an orthogonally alternating manner.The different failure mechanisms for the composites with 0/90°and±45°fibre orientations have been detected with the methods of experimental measurement,SEM observation and theoretical analysis.The composites specimens of 0/90°fibre orientation failed with macro-buckling of the high-modulus UHMWEP fibre layers with the matrix damage,whereas the specimens of±45°fibre orientation failed with the shearing of the soft matrix.Hence,the composite specimens in 0/90°fibre orientation had higher stiffness as well as compressive strength than those in±45°fibre orientation.The failure criteria of the composites under in-plane compression was employed to characterize the failure mechanism.Compared with the traditional thermoset matrix,the soft thermoplastic matrix leads to lower strength and higher failure strain of fibre reinforced composites under in-plane compression.In addition,the composite specimens cut by waterjet machine exhibited higher stress levels than those cut by bandsaw that introduced more initial imperfections with the temperature rising and tensile shocking.The comparison between the methodologies for cutting the tough composites can provide a valuable suggestion to obtain required composite structures without reducing the mechanical properties.展开更多
The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after proces...The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraaffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin-screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0. 23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.展开更多
Unsupervised and supervised pattern recognition( PR)techniques are used to classify the acoustic emission( AE) data originating from the quasi-isotropic self-reinforced polyethylene composites,in order to identify the...Unsupervised and supervised pattern recognition( PR)techniques are used to classify the acoustic emission( AE) data originating from the quasi-isotropic self-reinforced polyethylene composites,in order to identify the various mechanisms in the multiangle-ply thermoplastic composites. Ultra-high molecular weight polyethylene / low density polyethylene( UHMWPE / LDPE)composites were made and tested under quasi-static tensile load. The failure process was monitored by the AE technique. The collected AE signals were classified by unsupervised and supervised PR techniques, respectively. AE signals were clustered with unsupervised PR scheme automatically and mathematically. While in the supervised PR scheme,the labeled AE data from simple lay-up UHMWPE / LDPE laminates were utilized as the reference data.Comparison was drawn according to the analytical results. Fracture surfaces of the UHMWPE / LDPE specimens were observed by a scanning electron microscope( SEM) for some physical support. By combining both classification results with the observation results,correlations were established between the AE signal classes and their originating damage modes. The comparison between the two classifying schemes showed a good agreement in the main damage modes and their failure process. It indicates both PR techniques are powerful for the complicated thermoplastic composites. Supervised PR scheme can lead to a more precise classification in that a suitable reference data set is input.展开更多
Noil discarded fibers from fiber production for textile industry have short length and are always considered less valuable.Here,noil ramie fibers/HDPE composite is prepared using twin-screw extruder and the dynamic me...Noil discarded fibers from fiber production for textile industry have short length and are always considered less valuable.Here,noil ramie fibers/HDPE composite is prepared using twin-screw extruder and the dynamic mechanical and thermal properties are studied.The influence of ramie fiber and maleic anhydride-grafted polyolefin(MA-g-PO)on mechanical,dynamic mechanical and thermal properties is investigated.It is observed that the tensile,flexural and impact properties of the composites treated with MA-g-PO are all improved in comparison to the untreated composites.Dynamic mechanical properties of the composite with MA-g-PO show an increase in the storage modulus with a higherαrelaxation peak,together with the micromorphology analysis,indicating an improved interfacial bonding between fiber and matrix by the MA-g-PO addition.Furthermore,the change in TGA thermograms of composite caused by MA-g-PO exhibits that the addition of MA-g-PO is also helpful to increase the thermal stability of noil ramie fiber/HDPE composites.展开更多
Electrochemical oxidation of polyethylene glycol(PEG) in an acidic(pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the ...Electrochemical oxidation of polyethylene glycol(PEG) in an acidic(pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified(PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon(TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model.展开更多
文摘Several works have been based on the study of thermal variations in biomass to derive more valuable products such as fuels capable of replacing oil in the event of a crisis or activated carbon used as an adsorbent material, widely used in industry for the elimination of unwanted materials, both in liquid and gaseous environments. A study of thermal parameters such as: heating speed, retention time, drying temperature, carbonization temperature, particle size, was carried out with the aim of determining the characteristic factors of the carbonization of Polyethylene terephthalate (PET), sawdust (SC) and sawdust/polyethylene terephthalate (CPS) mixture. The results of the immediate analysis revealed a very low level of ash in PET (0.013%) compared to the level of ash in sawdust (2.9%), as well as a high level of fixed carbon (82.960%), which suggests the presence of mineral oxides and a significant carbon matrix unlike PET, which indicates a very significant organic matrix (essentially made up of organic matter) with the absence of mineral oxides. The study of thermal parameters showed the water loss from Sawdust (SC) and the Sawdust/Polyethylene terephthalate (CPS) mixture, an increase with temperature, unlike that of PET whose variation is essentially zero. Without heat treatment, sawdust alone contains approximately 7% water. The optimal drying temperature for this study is 110˚C for a stay of 24 hours. It appears that the largest mass losses for the PET samples are between 87.19% and 96.05%, followed by that of the mixture, between 47.33% and 64.37%. And the lowest are observed, those of sawdust (from 24.02% to 62.6%). However, here we can say that the influence of the mass is not great, given the slight difference between the losses by temperature. The results of the study of the influence of grain size showed that the differences are insignificant, even if we vary the diameter of the grains from simple to triple. To better minimize physical constraints such as the intragranular diffusibility of the volatile matter and the homogeneity of the temperature in the grains, 75 μm particles are found to be optimal for our study. It can be noted when studying the heating rate that the mass loss at the end of the reaction is approximately the same depending on each precursor material. However, it has been demonstrated that the heating rate strongly influences the nature of the reaction products both for volatile materials and for the solid residue as well as on the kinetic parameters of the chemical reaction. Furthermore, the variation in apparent density shows a decrease as a function of the increase in the residence time of the materials in the reactor. As the carbonization time increases, the apparent density decreases. We note, for the lignocellulosic material, that the apparent density stabilizes after 60 minutes.
文摘This study elaborates on the effects of matrix rigidity on the high-velocity impact behaviour of UHMWPE textile composites using experimental and numerical methods.Textile composite samples were manufactured of a plain-weave fabric(comprising Spectra?1000 fibres)and four different matrix materials.High-velocity impact tests were conducted by launching a spherical steel projectile to strike on the prepared samples via a gas gun.The experimental results showed that the textile composites gradually changed from a membrane stretching mode to a plate bending mode as the matrix rigidity and thickness increased.The composites deformed in the membrane stretching mode had higher impact resistance and energy absorption capacity,and it was found that the average energy absorption per ply was much higher in this mode,although the number of broken yarns was smaller in the perforated samples.Moreover,the flexible matrix composites always had higher perforation resistance but larger deformation than the rigid matrix counterparts in the tested thickness and velocity range.A novel numerical modelling approach with enhanced computational efficiency was proposed to simulate textile composites in mesoscale resolution.The simulation results revealed that stress and strain development in the more rigid matrix composite was localised in the vicinity of the impact location,leading to larger local deformation and inferior perforation resistance.
文摘High-density poly-ethylene (HDPE) is a nonbiodegradable recyclable plastic which is widely utilized in single use packaging applications. Consequently, it constitutes a significant amount of plastic waste found in landfills. From literature, it has been shown that parts produced using composites of HDPE with carbohydrate-based polymers, such as thermoplastic starch (TPS), experience mechanical degradation through hydrolytic degradation process. The possible utilization of recycled-HDPE (rHDPE) and TPS composite in nonconventional manufacturing processes such as Fused filament fabrication (FFF) has however not been explored. This study explores the potential application of rHDPE and TPS composites in FFF and optimizes the extrusion process parameters used in rHDPE-TPS filament production process. Taguchi method was utilized to analyze the extrusion process. The extrusion process parameters studied were the spooling speed, extrusion speed and the extrusion temperatures. The response variable studied was the filament diameter. In this research, the maximum TPS content achieved during filament production was 40 wt%. This filament was however challenging to use in FFF printers due to frequent nozzle clogging. Printing was therefore done with filaments that contained 0 - 30 wt% TPS. The experimental results showed that the most significant parameter in extrusion process was the spooling speed, followed by extrusion speed. Extrusion temperature had the least significant influence on the filament diameter. It was observed that increase in TPS content resulted in reduced warping and increased rate of hydrolytic degradation. Mechanical properties of printed parts were investigated and the results showed that increasing TPS content resulted in reduction in tensile strength, reduction in compression strength and increase in stiffness. The findings of this research provide valuable insights to plastic recycling industries and researchers regarding the utilization of recycled HDPE and TPS composites as substitute materials in FFF.
基金Thanks are kindly given to the Scientific and Technological Committee of Sichuan for financial supportWe are also grate-ful for project subsidizing by the Special Funds for Major Basic Research (Contract No. G1999064805) the National Natural Science
文摘In-situ composites based on dispersed poly (ethylene terephthalate) (PET) or polyamide (PA), and continuous polyethylene (PE) were prepared through a single screw extruder of Haake rheometer system with a rod-die relatively small in diameter. The extrudate was drawn at a drawing ratio of 3.1, and then quickly cooled in cold water. The specimens were obtained by injection molding at processing temperatures less than 190℃, far below the melting temperature of PET (265℃) and PA (230℃), which can maintain the solid state of PET and PA microfiber phase in the composites. Morphological observation with scanning electron microscopy (SEM) indicated that PET and PA can more or less form in-situ microfibers at compositions studied (0~20 wt pct PET or PA), and especially, PET and PA were almost deformed into fibers at the concentration of 15 wt pct. Tensile strength and modulus of the blends reinforced by PET or PA microfibers showed to be increased from the tensile test results. The most noticeable improvement of the tensile properties occurred at 15 wt pct of PET in PET/PE system, corresponding to the highest microfiber content, where the tensile strength reached 32.5 MPa, whereas only 19.5 MPa for the pure PE.
基金Project 06JK244 supported by the Special Foundation of Education Department of Shaanxi Province
文摘A thermogravimetric analysis (TG) was conducted to study the thermal decomposition behavior and kinetics of composites from coal and high density polyethylene (HDPE), linear low density polyethylene (LLDPE) or low density polyethylene (LDPE). The results show that coal facilitates melting of the polyethylene before temperatures reach 700 K in nitrogen due to the exothermic effect of coal. Above 700 K, adding coal into the polyethylene will result in smaller maximum rates of mass loss and higher initial mass loss temperatures of the composites. Hence, some chemical interactions, occurring between liquid compounds released in the pyrolysis of the coal and polymer, depend on several factors, such as coal rank and the molecular structure of polymers. Synergetic effects in coal and polymers were also found. Both chemical interactions and synergetic effects control the entire thermal decomposition behavior of compos- ites. The larger the amount of coal in the composites, the greater the decomposition temperature spans and the higher the maximum decomposition temperature, the smaller the devolatilization rates. The effect of coal on the thermal stability of composites lies in the hydrogen acceptor effect of the coals. Thermal decomposition of the coals, the polymers and related composites can be modelled via first order parallel reactions between 563 K and 763 K.
基金Supported by the Ministerial Level Advanced Research Foundation(2030301020502)
文摘Quasi-static and high strain rate compressive behaviors and failure mechanisms of hygrothermal treated ultra-high molecular weight polyethylene/polyurethane(UHMWPE/PU)composites have been studied in this paper.Firstly,the UHMWPE composites were immersed in water at 70℃.The out-ofplane compression test was then performed on the dry/wet state specimens at quasi-static states(0.001-0.01 s^(-1))and high strain rate states(800-2 400 s^(-1)).The split Hopkinson pressure bar(SHPB)was adopted in the dynamic tests and waveform shapers were used to smooth and control the incident pulse.The results show that there are two platforms for the water absorption curve of UHMWPE composites.The absorption of moisture reduces the quasi-static compressive strength of the material while initially increasing,then decreasing the dynamic compressive strength.Matrix plasticization,fiber/matrix interface degradation and void expansion are the main factors affecting the irregular change of static/dynamic compressive strength of UHMWPE composites.
基金Funded by the National Natural Science Foundation of China(No.11305138)the Jiangsu Science and Technology Department Support Program(No.BY2019188)the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province(No.14KJD540004).
文摘The in-plane compressive characteristics of the ultra-high molecular weight polyethylene(UHMWPE)fibre(Dyneema█)reinforced composites,both in 0/90°and±45°fibre orientations with respect to the loading direction,have been investigated.The composite made from unidirectional high modulus fibres(volume fraction 83%)and low strength polyurethane matrix(volume fraction 17%)is layered in an orthogonally alternating manner.The different failure mechanisms for the composites with 0/90°and±45°fibre orientations have been detected with the methods of experimental measurement,SEM observation and theoretical analysis.The composites specimens of 0/90°fibre orientation failed with macro-buckling of the high-modulus UHMWEP fibre layers with the matrix damage,whereas the specimens of±45°fibre orientation failed with the shearing of the soft matrix.Hence,the composite specimens in 0/90°fibre orientation had higher stiffness as well as compressive strength than those in±45°fibre orientation.The failure criteria of the composites under in-plane compression was employed to characterize the failure mechanism.Compared with the traditional thermoset matrix,the soft thermoplastic matrix leads to lower strength and higher failure strain of fibre reinforced composites under in-plane compression.In addition,the composite specimens cut by waterjet machine exhibited higher stress levels than those cut by bandsaw that introduced more initial imperfections with the temperature rising and tensile shocking.The comparison between the methodologies for cutting the tough composites can provide a valuable suggestion to obtain required composite structures without reducing the mechanical properties.
文摘The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraaffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin-screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0. 23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.
基金Scientific Research Foundation of Guangdong Polytechnic,China(No.K2010201)
文摘Unsupervised and supervised pattern recognition( PR)techniques are used to classify the acoustic emission( AE) data originating from the quasi-isotropic self-reinforced polyethylene composites,in order to identify the various mechanisms in the multiangle-ply thermoplastic composites. Ultra-high molecular weight polyethylene / low density polyethylene( UHMWPE / LDPE)composites were made and tested under quasi-static tensile load. The failure process was monitored by the AE technique. The collected AE signals were classified by unsupervised and supervised PR techniques, respectively. AE signals were clustered with unsupervised PR scheme automatically and mathematically. While in the supervised PR scheme,the labeled AE data from simple lay-up UHMWPE / LDPE laminates were utilized as the reference data.Comparison was drawn according to the analytical results. Fracture surfaces of the UHMWPE / LDPE specimens were observed by a scanning electron microscope( SEM) for some physical support. By combining both classification results with the observation results,correlations were established between the AE signal classes and their originating damage modes. The comparison between the two classifying schemes showed a good agreement in the main damage modes and their failure process. It indicates both PR techniques are powerful for the complicated thermoplastic composites. Supervised PR scheme can lead to a more precise classification in that a suitable reference data set is input.
基金supported by the National Scientific and Technical Supporting 12th Five-year Plan Project(No.2012BAD23B0203)
文摘Noil discarded fibers from fiber production for textile industry have short length and are always considered less valuable.Here,noil ramie fibers/HDPE composite is prepared using twin-screw extruder and the dynamic mechanical and thermal properties are studied.The influence of ramie fiber and maleic anhydride-grafted polyolefin(MA-g-PO)on mechanical,dynamic mechanical and thermal properties is investigated.It is observed that the tensile,flexural and impact properties of the composites treated with MA-g-PO are all improved in comparison to the untreated composites.Dynamic mechanical properties of the composite with MA-g-PO show an increase in the storage modulus with a higherαrelaxation peak,together with the micromorphology analysis,indicating an improved interfacial bonding between fiber and matrix by the MA-g-PO addition.Furthermore,the change in TGA thermograms of composite caused by MA-g-PO exhibits that the addition of MA-g-PO is also helpful to increase the thermal stability of noil ramie fiber/HDPE composites.
文摘Electrochemical oxidation of polyethylene glycol(PEG) in an acidic(pH 0.18 to 0.42) and high ionic strength electroplating solution was investigated. The electroplating solution is a major source of wastewater in the printing wiring board industry. A paraffin composite copper hexacyanoferrate modified(PCCHM) electrode was used as the anode and a bare graphite electrode was used as the cathode. The changes in PEG and total organic carbon(TOC) concentrations during the course of the reaction were monitored. The efficiency of the PCCHM anode was compared with bare graphite anode and it was found that the former showed significant electrocatalytic property for PEG and TOC removal. Chlorides present in the solution were found to contribute significantly in the overall organic removal process. Short chain organic compounds like acetic acid, oxalic acid, formic acid and ethylene glycol formed during electrolysis were identified by HPLC method. Anode surface area and applied current density were found to influence the electro-oxidation process, in which the former was found to be dominating. Investigations of the kinetics for the present electrochemical reaction suggested that the two stage first-order kinetic model provides a much better representation of the overall mechanism of the process if compared to the generalized kinetic model.