Abstract Synthesis and characterization of a flexible polymer produced from silane coupling agent (SCA) and hydroxyl terminated polybutadiene (HTPB) were performed. Mechanical properties of chemically and electrochemically prepared conducting composites synthesized from this polymer were investigated. Conductivities of the composites were also measured. Polypyrrole enhanced the mechanical properties of the chemically prepared conducting composite. Doping with iodine greatly changed the conductivity of the composite. However, the change in mechanical properties and the conductivities of the electrochemically prepared composite were not as significant when compared with the electrochemically prepared polypyrrole. Among the composites, a chemically prepared composite was highly flexible like rubber. However, the electrochemically produced composite possesses two orders of magnitude higher conductivity. Also, this composite revealed higher tensile strength and elasticity with respect to pristine polypyrrole. 相似文献
Polypropylene (PP) particles were chemically coated with polypyrrole (PPy). The content of polypyrrole varied from 0.8 to 7.6 wt.-%. Electrical conductivity of compression moulded samples depends on the concentration of polypyrrole and reached values from 4×10−10 to 5×10−3 S/cm, which is about 7 orders of magnitude higher than the conductivity in the blends prepared by mechanical mixing of PP and PPy in the same PPy concentration range. Highly conductive composites were also obtained from a mixture of coated and non-coated PP particles. The PP/PPy composites were characterized by elemental analysis, SEM and mechanical testing. The antistatic properties of PP/PPy composites were demonstrated. The electrical and mechanical properties depend on processing of composites. 相似文献
Composites of a polyindole (PIN) and poly(vinyl acetate) (PVAc) were prepared chemically using FeCl3 as an oxidant agent in anhydrous media. The composite compositions were altered by varying the indole monomer during preparation. The composites were characterized by FTIR and UV‐visible spectroscopies, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), stress‐strain experiments and conductivity measurements. Moreover, the film of PVAc and PIN/PVAc composites were prepared by casting on glass Petri dishes to examine their stress‐strain properties. PIN/PVAc composites are thermally more stable than PIN. It was found that the conductivities of PIN/PVAc composites depend on the indole content in the composites. 相似文献
New types of composites were prepared using low-density polyethylene (LDPE) filled with modified organic filler, Canadian switch grass coated with polypyrrole (PPy). The grass surface was entirely covered when 10 wt.% of pyrrole was used for the modification, as confirmed by scanning electron microscopy and infrared spectroscopy. LDPE composites filled with modified grass were prepared by melt mixing and their properties were compared with the properties of the composites filled with unmodified grass. The influence of crosslinking, induced by 1 wt.% of peroxide, on mechanical, thermal and electrical properties of the composites was investigated. Crosslinking enhanced the tensile strength of the prepared composites in the entire range of the filler content. The Young’s modulus of the composites prepared by crosslinking is slightly lowered when compared with the uncrosslinked composites if the filler content is less than 60 wt.%, for higher filler content it is increased. The conductivity of the uncrosslinked composites containing 40 wt.% of grass modified by PPy was in the range 1 × 10−6 S cm−1, which is a value by 5 orders of magnitude higher than the conductivity of the crosslinked materials. The presence of PPy on grass surface leads to a reduction of crosslinking of the LDPE matrix. 相似文献
Long glass fiber reinforced poly(butylene terephthalate) composites (LGF/PBT) were prepared by a new process. PBT oligomers with low melt viscosity were impregnated into the reinforcing glass fiber and then grafted to the reinforcing glass fiber surface treated with a silane coupling agent during solid‐state polymerization. The reinforcing glass fiber, after removing ungrafted PBT from LGF/PBT, was investigated with the result showing the presence of a grafted PBT layer on the surface of treated glass fiber. The mechanical properties of the composites were significantly improved owing to the grafting of the PBT macromolecules. The fiber length distribution and fiber arrangement in the injection molded composites were also studied and the results showed that a small amount long glass fiber could be connected at junction points in the composites, which were of benefit to the mechanical properties of the composites. 相似文献
The dry pulp direct kneading method is an industrially viable, low-energy process for manufacturing cellulose nanofiber (CNF)-reinforced polymer composites, where the chemically modified pulps are nanofibrillated and uniformly dispersed in the polymer matrix during melt compounding. In the present study, cellulose fibers of various sizes ranging from surface-fibrillated pulps (20 μm in width) to fine CNFs (20 nm in width) were prepared from softwood bleached kraft pulps using a refiner and a high-pressure homogenizer. These cellulose fibers were modified with alkenyl succinic anhydride and dried. The dried fibers were used as a feed material for melt compounding in the dry pulp direct kneading method to fabricate CNF-reinforced high-density polyethylene (HDPE). When surface-fibrillated pulps were employed as a feed material, the pulps were nanofibrillated and dispersed uniformly in the HDPE matrix during melt compounding. The resulting composites had much better properties—i.e., much higher tensile modulus and strength values, and much lower coefficient of thermal expansion values—than the composites produced using pulps without pre-fibrillation. However, when CNFs were used as a feed material, they were shortened and agglomerated during melt compounding, and the properties of the composites consequently deteriorated. The study concludes that surface-fibrillated pulp, which can be produced cost-effectively using a refiner on an industrial scale, is more suitable as a feed material than CNFs for melt compounding in the dry pulp direct kneading method. This finding enables the elimination of a preliminary step in the preparation of CNFs from pulps, which is a time-consuming and energy-intensive process.
This article reports the studies of photo-oxidative behaviour of polypropylene/maleic anhydride-grafted polypropylene/organic modified montmorillonite (PP/PPgMA/OMMT) composites prepared by two different melt processing methods. Samples of pristine polypropylene (PP) and PP/PPgMA/OMMT composites were prepared in an internal mixer and in a twin screw extruder. The samples were exposed to long wavelength radiations (λ > 300 nm) for the photo-oxidation. The samples were examined by FTIR, X-ray diffraction and microscopy. Similar to the pristine (PP), it is found that the photo-oxidation process in the composites depends on the melt processing conditions, which could cause the deterioration of organic modifier of the clay and the polymer matrix. The new radicals formed in addition to the iron impurities in the montmorillonite accelerate the photo-oxidation. 相似文献
Abstract Adduct polymer (PPGMA) prepared from polypropylene glycol and maleic anhydride was found to give stable inverted emulsions when mixtures of cement, water, and vinyl monomers were vigorously stirred in the presence of PPGMA. In this case, the carboxyl groups of PPGMA were neutralized with metal ions generated from the cement into neutralized PPGMA which acts as an effective W/O type emulsifier. The inverted emulsions containing cement gave a new type of polymer-cement composites by polymerization of the vinyl monomers and also by hardening of the cement. Water-free composites were easily obtained by removing evaporative water. The effect of cement on the physical properties of the water-free composites was remarkable. Further, the use of mixed fillers of cement and Al(OH)3 was found to improve the flame-retardant properties of the composites; however, increasing the Al(OH)3 content in the fillers resulted in a decrease in the physical properties. Generally, the composites have improved resistance to acid media in which the usual foamed hydrated cement is eroded. 相似文献
In this work, a free-radical grafting method was used to modify multi-walled carbon nanotubes (MWNT) to improve their dispersion in a polymer matrix by use of a compounding technique. By free-radical grafting for in-situ polymerization, MWNT agglomerates are turned into a networked micro-structure, which in turn builds up a strong interfacial interaction with the polymeric matrix during the mixing procedure. Polystyrene (PS)-MWNT with a hairy rod nanostructure were synthesized by in-situ free-radical polymerization of styrene monomer on the surface of MWNT. PS-MWNT/polypropylene (PP) nanocomposites were prepared by melt mixing. The effect of polystyrene-grafted multi-walled carbon nanotube (PS-MWNT) content on the rheological properties of the polypropylene (PP)-based nanocomposites was investigated. Surface characteristics of PS-MWNT were investigated by infrared spectroscopy, Raman spectroscopy (FT-Raman), thermogravimetric analysis, and transmission electron microscopy. The rheological properties of the PS-MWNT/PP composites were confirmed by rheometry. The complex viscosity of the PS-MWNT/polypropylene (PP) nanocomposites increased with increasing PS-MWNT content, primarily because of an increase in the storage modulus G??. In-situ-polymerized PS-MWNT were uniformly distributed in the PP matrix. In addition, the PS-MWNT were interconnected in the PP matrix and then formed PS-MWNT networks, resulting in the formation of a conducting network. Therefore, compared with samples with pristine MWNT, PS-MWNT-reinforced samples have lower conductivity as a resulting of PS grafting on the surface of MWNT. 相似文献
Rossells fiber reinforced polypropylene composites were prepared by melt mixing. The fiber content was 20 wt%. Octadecyltrimethoxysilane (OTMS) and maleic anhydride grafted polypropylene (MAPP) were used to improve the adhesion between poly(propylene) (PP) and the fiber. The mechanical, rheological, and morphological properties, and heat distortion temperature (HDT) of the composites were investigated. Tensile strength, impact strength, flexural strength and HDT of MAPP modified PP composites increased with an increase in MAPP content. However, no remarkable effect of MAPP content on the Young's modulus of the composites was found. OTMS resulted in small decreases of tensile strength and Young's modulus, and increase in impact strength. Scanning electron micrographs revealed that MAPP enhanced surface adhesion between the fiber surface and PP matrix. 相似文献
Addition of wood particles to polymers can cause a change of properties of the composites which depends on features of lignocellulosic materials and those of polymers. It is also observed in the flammability characteristics of the composites.In this work, the flammability of polypropylene composites with pine wood particles obtained by extrusion and press moulding was analyzed. The amount of wood particles was 50%. Polymers with various melt flow index (MFI) were used (Malen F-401, PP HY-202 and Malen S-702).The samples were tested using Cone Calorimeter at heat flux of 35 kW/m2. Heat release rate (HRR) curves of composites show that thermal decomposition depends on the kind of polypropylene used. In the presence of PP HY-202 and Malen S-702, the flammability characteristic is similar to that of lignocellulosic materials, in contrast to composites with matrices prepared from Malen F-401. The observed phenomenon is interpreted in terms of the wettability of particles of pine wood by polymers of varying melt viscosity. 相似文献
ABSTRACT The role of di-cumyl peroxide (DCP) as compatibilizer in low density Polyethylene/Polypropylene (LDPE/PP) blends has been explored. Mixtures with varying LDPE/PP ratio were prepared in a Brabender plasticorder and tested for their mechanical properties and calorimetric response. Then peroxide was added at concentrations up to 0.5%, and the mechanical properties of the these new blends were measured. Also, the mixing torque, melt flow index and gel content of the above products were recorded as a function of peroxide concentration. It was found that the incorporation of DCP restricts the thermoplastic characteristics of the melt, which was primarily attributed to branching which occurs in LDPE. This results in an enhancement in the adhesive bonding between the two polymers mainly due to chain entanglements. This was further supported by the fact that mechanical properties of the treated blend were significantly improved. 相似文献
Isotactic polypropylene (iPP) based nanocomposites filled with calcium carbonate nanoparticles (CaCO3) were prepared by melt mixing and structure-properties relationships of the nanomaterials were studied. Elongated CaCO3 nanopowders coated with two different coating agents, polypropylene-maleic anhydride graft copolymer (iPP-g-MA) and fatty acids (FA), were tested as nanoreinforced phases. The influence of surface treatment of the nanoparticles on the polymer/nanofillers interfacial adhesion and on the final materials properties was investigated. Morphological analysis showed that the selected coating agents induce different iPP/nanofiller adhesion degrees. Young's modulus increases as a function of the nanoparticles content and the coating agent nature. Finally, all the prepared nanocomposites showed a significant improvement of iPP barrier properties either to oxygen or to carbon dioxide. 相似文献
The influence of multiwalled carbon nanotubes (MWCNTs) on phase morphology, lamellar structure, thermal stability, melting behaviour and isothermal crystallisation kinetics of polycarbonate/polypropylene (PC/PP) blend nanocomposites has been investigated. Both neat blends and PC/PP (60/40)/MWCNT nanocomposites were prepared by melt mixing method. Morphological analyses were performed by high-resolution X-ray micro-computed tomography and scanning electron microscopy. The co-continuous morphology of the blend was retained irrespective of MWCNT loading. In addition, a substantial refinement in the co-continuous structure was observed. Wide angle and small angle X-ray scattering studies were used to analyse the structural properties of the blend nanocomposites. The addition of MWCNT increases the long period of polypropylene. The influence of addition of MWCNT on the crystallisation temperature and equilibrium melting temperature (Tm°) of polypropylene was followed. The MWCNTs promote crystallisation rate of polypropylene in the blend nanocomposites. 相似文献