Showing papers by "Ming Qiu Zhang published in 2004"
TL;DR: The sliding wear performance of epoxy composites filled with nano-sized Al2O3 particles was studied in this paper, where the nanoparticles were pretreated by either silane coupling agent or graft polymerization to enhance the interfacial interaction between the fillers and the matrix polymer.
171 citations
TL;DR: In this paper, the relationship between the interfacial interactions in polypropylene-based composites and tensile performance was analyzed. But the results were limited to the case of low silica concentration and low percentage grafting.
Abstract: Polypropylene-based composites were prepared by melt blending with nano-silica, which was pre-treated by grafting polymerization onto the surface. Tensile moduli and strengths of the composites were determined as a function of the nano-silica content and the amount of the grafting polymers chemically attached to the nanoparticles, ie percentage grafting. To analyse the relationships between the interfacial interactions in the composites and tensile performance, a number of models dealing with the static and dynamic mechanical behaviours of the particulate composites were applied. It was found that stronger interfacial interactions exist in the grafted nano-silica-filled polypropylene composites as compared to the composites with untreated nano-silica. Since the interfacial interactions occur only within a very short range, the greatest interaction between the modified nanoparticles and the matrix is achieved in the case of low silica concentration and low percentage grafting. An increase in the percentage grafting for various grafted nanoparticles definitely results in an increase of interphase thickness, but the interfacial interactions and the tensile performance of the composites are not necessarily improved because the agglomeration structure of the nanoparticles and the miscibility between the components play the leading role. Copyright © 2004 Society of Chemical Industry
144 citations
TL;DR: In this paper, the grafting polymers on the nanoparticles provided the composites with a tailorable interphase, which is beneficial to stress transfer and stiffening, strengthening, and toughening effects.
Abstract: Grafted inorganic nanoparticles can greatly improve the mechanical performance of polymers. To examine the effects of the interfacial characteristics generated by the grafting polymer bonded to nanoparticle surfaces, we chemically grafted nano-silica with different polymers and then melt-mixed it with polypropylene (PP). We extracted the homopolymers produced during the graft polymerization from the grafted products before the composites were manufactured to get rid of the side effects of the nongrafting polymers. We tailored the interfacial interaction between the grafted nano-SiO2 and PP matrix by changing the amount of the grafting polymers on the nanoparticles, that is, the grafting percentage. Mechanical tests indicated that all the composites incorporated with grafted nano-SiO2 particles possessed much higher impact strength than untreated SiO2/PP composites and neat PP. The greatest contribution of the particles was made at a low grafting percentage. Tensile measurements showed that the treated nanoparticles could provide PP with stiffening, strengthening, and toughening effects at a rather low filler content (typically 0.8 vol %) because of the enhanced interfacial adhesion resulting from molecular entanglement and interdiffusion between the grating polymers on the nanoparticles and matrix macromolecules. The presence of grafting polymers on the nanoparticles provided the composites with a tailorable interphase. The tensile performance of the composites was sensitive to the nature of the grafting polymers. Basically, a hard interface was beneficial to stress transfer, whereas a soft one hindered the development of cavities in the matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1771–1781, 2004
105 citations
TL;DR: In this paper, the synthesis of conductive composites consisting of waterborne polyurethane (WPU) and carbon black (CB) is reported, and it is found that different mechanisms are responsible for the broad applicability of the composites as candidates for gas sensing materials owing to the different interactions among the matrix polymer, the filler particles and the solvent molecules.
96 citations
TL;DR: In this article, the authors investigated the electrical resistance of amorphous polymer composites against various organic vapors at low concentrations by using polymerization-filling fabricated carbon black/poly(butyl methacrylate) (CB/PBMA) system as the model material.
88 citations
TL;DR: In this article, nano-sized Al2O3 particles grafted with polystyrene or polyarcrylamide were employed as fillers for fabricating epoxy based composites.
Abstract: Nano-sized Al2O3 particles grafted with polystyrene or polyarcrylamide were employed as fillers for fabricating epoxy based composites. Curing habit, mechanical properties and tribological performance revealed by sliding wear tests of the composites were investigated. The experimental results indicated that the nanoparticles accelerate curing of epoxy, increase composites' impact strength and decrease wear rate and frictional coefficient of the composites. The surface modification by means of grafting polymerization can further enhance the properties improvement of epoxy due to the increased filler/matrix interfacial interaction. Compared to frictional coefficient, wear rate of epoxy can be decreased more remarkably by the addition of nano-alumina when rubbing against steel. The wear mode changes from severe peeling off of unfilled epoxy to mild micro-ploughing in the case of nano-alumina filled composites.
67 citations
TL;DR: In this paper, the degradation behavior of self-reinforced sisal composites was evaluated with reference to the effects of ageing in water, enzyme solution and soil, respectively.
58 citations
42 citations
TL;DR: In this article, grafting of glycidyl methacrylate (GMA) onto the surface of alkyl nano-SiC was carried out, resulting in composite particles with SiC core and polymeric shell.
Abstract: To improve the tribological performance of nano-SiC particles filled epoxy composites, surface modification of the fillers is necessary. By means of soapless emulsion polymerization method, graft polymerization of glycidyl methacrylate (GMA) onto the surface of alkyl nano-SiC was carried out, resulting in composite particles with SiC core and polymeric shell in which polyglycidyl methacrylate (PGMA) is chemically attached to the nanoparticles by the double bonds introduced during the pretreatment with a coupling agent. By analyzing the reaction mechanism, the emulsion polymerization loci were found to be situated at the SiC surface. Also, the factors affecting the grafting yielding of PGMA on the particles were investigated, including monomer concentration, initiator consumption, reaction temperature, reaction time, etc. Accordingly, an optimum grafting reaction condition was determined. It was shown that the grafted nanoparticles exhibit greatly improved dispersibility in good solvent for the grafting polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3842–3852, 2004
34 citations
TL;DR: In this paper, a polyurethane-based composite with 3.5 wt.% of carbon black was used for gas sensor arrays with much smaller sizes and wide sensitivity.
28 citations
TL;DR: In this paper, the effect of the reaction conditions, such as alkalinity, temperature and the extent of benzylation, was studied in detail, and structural characteristics, melt flow and mechanical properties of the modified sisal and their composite sheets were analyzed.
Abstract: SUMMARY To prepare self-reinforced sisal composites, sisal fibers were cleaned, treated with NaOH solution, and then benzylated with benzyl chloride. In this way, the skin layers of the fibers were converted into thermoplastic material while the core of the fiber cells remained unchanged. Under the circumstances of hot pressing, self-reinforced all-plant fiber composites of sisal can be prepared, in which plasticised sisal serves as matrix and the unplasticised cores of the fibers as reinforcement. In this work the effect of the reaction conditions, such as alkalinity, temperature and the extent of benzylation, was studied in detail. The roles of quaternary ammonium salts and γ-ray irradiation treatment on the efficiency of benzylation were also taken into account. In addition, structural characteristics, melt flow and mechanical properties of the modified sisal and their composite sheets were analysed. It was found that a balance between melt processability and the reinforcing effect of the benzylated sisal fibers was required.
TL;DR: In this paper, the synthesis of nanometer-sized clusters of CdS in inverse-micellar solution and in situ chemical derivatization of the surface of these cluster compounds were studied.
TL;DR: In this paper, the mechanical performance of the nanocomposites and the morphological changes induced by the addition of the nanoparticles were investigated and it was confirmed that the copolymer chains were chemically bonded to the silica particles during mechanochemical grafting in the ball mill.
Abstract: Nanocomposites consisting of ethylene-propylene block copolymer filled with nanosilica (pre-treated by ball milling aided graft polymerisation) were prepared by a conventional compounding technique. The mechanical performance of the nanocomposites and the morphological changes induced by the addition of the nanoparticles were investigated. It was confirmed that the copolymer chains were chemically bonded to the silica particles during mechanochemical grafting in the ball mill. Morphology observations revealed that strong interfacial interaction between the grafting polymer (i.e., poly(butyl acrylate)) and the matrix (i.e., ethylene-propylene block copolymer) is critical for bringing the reinforcing effect of the nanoparticles into play. Owing to the enhanced interfacial interaction, the grafted nanoparticles exhibited a nucleating effect and improved the crystallinity of the polymer matrix. In addition, the particles also had a toughening effect on the amorphous polypropylene phase because of entanglements between the grafting polymer and the matrix. Insufficient interaction between the nanoparticles and ethylene-propylene rubber phase of the copolymer matrix actually introduces restraints. As a result, the tensile strength and modulus of the nanocomposites can be significantly increased by using low loadings of the treated nanoparticles. The decrease in the notched Charpy impact strength was insignificant in comparison to that of conventional micron-scale inorganic particles filled composites. The technical route proposed is therefore feasible for fabricating polymer composites with inorganic nanoparticles.
TL;DR: Novel cellulose derivatives were prepared from reacting (1R)-(+)-camphor-10-sulfonic chloride with cellulose acetate in acetone and triethylamine and exhibited decreased thermal stability, improved solubility in organic solvents and enhanced enantioselectivity towards tyrosine isomers.
TL;DR: In this paper, the performance of nano-silica filled epoxy has been evaluated in terms of wear and friction coefficient and wear rate at rather low filler loading (∼2 vol%) in comparison with unfilled epoxy.
Abstract: To enhance service performance of polymeric materials for tribological applications, micrometer inorganic particulates are generally incorporated [1], which increases load-bearing capacity and thermal conductivity of the matrices, promotes adhesion of the transferred film to the counterface, etc. However, these micron particulate composites have some inherent disadvantages. The detached particles, for instance, tend to be entrapped within the rubbing interface, leading to severe abrasion of the composites [2]. Besides, the fraction of the particles needed to achieve sufficient improvement of the tribological properties of the composites is relatively high, which remarkably decreases the processability of the polymers. To solve the problems, employment of particles of reduced size, i.e., nanoparticles, proves to be an effective method. By either improving dispersion of nanoparticles in matrices [3] or enhancing their affinity to the surrounding polymers [4], the defects of the micro-sized particulate composites can be overcome. As shown by our previous works [4, 5], nano-silica filled epoxy has significantly low frictional coefficient and wear rate at rather low filler loading (∼2 vol%) in comparison with unfilled epoxy. Besides, the above positive effect can be further strengthened when the nanoparticles are pregrafted by some polymer chains that can take part in curing reaction of epoxy. Considering that friction and wear are involved mostly in the top layer of a rubbing surface when a bulk material serves in tribological environment, mechanophysically and mechanochemically induced changes in the surface layer would certainly in turn influence the tribological performance of the material [6, 7]. Therefore, post-mortem characterization of frictional surface is able to yield valuable information about the wear processes that cannot be obtained by other techniques.
01 Jan 2004
TL;DR: In this paper, an all-plant fiber composite material is characterized by easy processing, environment friendly and low cost, and the physical heterogeneity of the current natural fiber composite is favorable for interfacial interaction.
Abstract: Plasticization of fir sawdust was carried out in the present work to prepare natural resources based plastics. It was found that thermoplasticity and mechanical properties of the chemically modified wood flour changed with the substitution reaction conditions. By compounding sisal fibers and the plasticized fir sawdust, unidirectional laminates were manufactured similar to conventional thermoplastic composites. Such an all-plant fiber composite material is characterized by easy processing, environment friendly and low cost. Instead of chemical heterogeneity of conventional composites, physical heterogeneity of the current natural fiber composite is favorable for interfacial interaction.
TL;DR: In the course of long-term service, electrically conductive polymer composites acting as positive temperature coefficient (PTC) materials are faced with performance decay characterized by gradually increased room temperature resistivity and decreased PTC intensity as mentioned in this paper.
Abstract: In the course of long-term service, electrically conductive polymer composites acting as positive temperature coefficient (PTC) materials are faced with performance decay characterized by gradually increased room temperature resistivity and decreased PTC intensity. To reveal the influencing factors and to find appropriate ways for solving the problems, thermal-cold cycling experiments (which simulate the extreme operating conditions of PTC type materials in a laboratory environment) and electrification tests are carried out in the current work. The results demonstrate that irreversible damage of partial conductive networks and, in particular, oxidation degradation induced crystallizability deterioration of the matrix polymer are responsible for the electrical performance decay. Additionally, an increase in the contact resistance formed at the metallic electrode/composite contacts exerts a negative influence on the service life of the composites. Polym. Compos. 25:270–279, 2004. © 2004 Society of Plastics Engineers.
Patent•
28 Jan 2004
TL;DR: In this article, the mixed polyurethane emulsion and conduction carbon black is used to make composite material and the prepared composite material possesses the advantages of low filtration value, favorable processability of material and mechanical property as well as high stability.
Abstract: Naturally drying the mixed polyurethane emulsion and conduction carbon black makes the composite material. The prepared composite material possesses the advantages of low filtration value, favorable processability of material and mechanical property as well as high stability. Moreover, the method provides simple processing technique, low cost and safe environment protection.
TL;DR: In this article, in situ grafting of certain monomers was applied during the melt compounding process to improve the conductive properties of carbon-black-filled low-density polyethylene.
Abstract: To improve the conductive properties of carbon-black-filled low-density polyethylene, in situ grafting of certain monomers was applied during the melt compounding process. The experimental data obtained demonstrated that chemical bonding could thus be established between the fillers and the matrix polymer. The degree of enhancement of the filler/matrix interfacial interactions in the composites prepared in this way depends on the species of the grafting monomers being employed. When compared with the untreated carbon black composites, the composites manufactured through in situ melt grafting exhibited reduced room temperature resistivities and greatly increased positive temperature coefficient intensities, as well as favorable performance reproducibility. This proposed technical route has several advantages, including simplicity, low cost and easy control. Copyright © 2004 Society of Chemical Industry
01 Jan 2004
TL;DR: In this article, the performance of the nanocomposites and morphological changes induced by the addition of the nanoparticles are investigated and it is confirmed that the polymer chains are chemically bonded to the particles during the mechanochemical grafting in the ball mill.
Abstract: Nanocomposites of ethylene-propylene block copolymer filled with nanosilica pre-treated through ball milling aided graft polymerization are prepared by conventional compounding technique. Mechanical performance of the nanocomposites and morphological changes induced by the addition of the nanoparticles are investigated. It is confirmed that the polymer chains are chemically bonded to the particles during the mechanochemical grafting in the ball mill. Morphology observations reveal that strong interfacial interaction between the grafting polymer and the matrix is critical to bring reinforcing effect of the nanoparticles into play. Owing to the enhanced interfacial interaction, grafted nanoparticles ehxibit nucleating effect and improve crystallinity of the polymer matrix. In addition, the particles also have toughening effect on the amorphous polypropylene phase due to the entanglement between the grafting polymer and the matrix. The insufficient interaction between the nanoparticles and rubber phase of the copolymer matrix actually introduces restraints. As a result, the tensile strength ofnanocomposites can be significantly increased at low loading of the treated nanoparticles. The decrement of notched Charpy impact strength is insignificant in comparison to that of conventional micron-scale inorganic particles filled composites. The technical route proposed in the current work is thus proved to be feasible for fabricating polymer composites with inorganic nanoparticles.
01 Jan 2004
TL;DR: In this article, a grafting of PGMA onto the surface of alkyl nano-SiC was carried out by means of soapless emulsion polymerization method.
Abstract: To improve the tribological performance of nano-SiC particles filled epoxy composites, surface modification of the fillers is necessary. By means of soapless emulsion polymerization method, graft polymerization of glycidyl methacrylate (GMA) onto the surface of alkyl nano-SiC was carried out. The monomer, polyglycidyl methacrylate (PGMA) is chemically attached to the nanoparticles by the double bonds introduced during the pretreatment with a coupling agent. By analyzing the reaction mechanism, the emulsion polymerization loci were found to be situated at the SiC surface. Besides, the factors affecting the grafting yielding of PGMA on the particles were investigated, including monomer concentration, initiator consumption, reaction temperature, reaction time, etc. Accordingly, an optimum grafting reaction condition was determined. It was shown that the grafted nanoparticles exhibit greatly improved dispersibility in good solvent for the grafting polymer. The primary studies about the tribological performance of epoxy composite showed a positive effect of grafted nano-SiC as expected.