Using the experience gained from the development of polymer–polymer nanofibrillar composites (NFCs), an attempt was undertaken to manufacture PET single polymer nanofibrillar composites. For this purpose polypropylene (PP) was removed by selective extraction from a knitted textile manufactured with PP/PET (80:20 by wt) blend. The remaining PET nanofibrillar textile was then sandwiched between lower‐melting PET films and compression molded at 120 °C. The obtained PET single polymer NFCs comprised PET nanofibrils as reinforcement and showed an improvement in the tensile strength and modulus of 37–100 and 40–140%, respectively (depending on the annealing temperature after compression molding and the test direction) compared to those of the starting isotropic matrix film.
In situ PET microfibrils are created by drawing melt‐blended PP and PET. The drawn blend is used to prepare polymer/polymer MFCs, and isolated PET microfibrils are used for the manufacturing of MF‐SPCs. Samples are prepared with different fibril orientations to determine the effect of orientation on the mechanical properties of the two types of composites. The resulting composites show improvements in stiffness of 77% for uniaxial MFCs, and 125% for uniaxial MF‐SPCs, with the highest recorded modulus of 8.57 GPa for a uniaxial MF‐SPC sample. SEM observations confirm that the fibrillar structure and excellent alignment is maintained. The changes in the reinforcement effect with orientation are very similar to those predicted by the rule of mixtures for the crossply.
A new class of polymer materials is reviewed, the SPCs, in which the matrix and the reinforcement share the same chemical composition. In addition to their milder environmental impact as compared to traditional polymer composites, they show superior mechanical performance mainly due to the improved adhesion between matrix and reinforcement. Another advantage of SPCs is the missing dispersion step in their production, thus contrasting the common polymer nanocomposites. Definition, manufacturing, classification, and the application opportunities of SPCs are described. Special attention is paid on the very new members of the SPC family, the micro‐ and nanofibrillar SPCs, including the techniques for preparation of their starting neat micro‐ and nanofibrils using bulk polymers.
A simple, easily accessible solvent‐free method for the dispersion of MWCNTs into PET is proposed, based on the preparation of a microparticulate polymer/nanotube masterbatch via cryogenic impact‐milling and its subsequent melt blending with the bulk polymer. Thermal and mechanical properties of nanocomposites prepared using this method were evaluated as a function of nanotube concentration. Thermal stability was improved, and superior crystallization behavior of PET in the nanocomposites was observed. Significant improvements of around 25% in tensile strength and tensile modulus of the nanocomposites was achieved using this strategy, with only 0.25 wt.‐% MWCNT, compared to previous literature data where 1 wt.‐% MWCNT was employed.
Unsaturated fatty acid (FA)–modified nanocellulose (m‐NC) shows potential application in improving mechanical properties of unsaturated polyester/m‐NC nanocomposites (UPe/m‐NC). A polyester matrix is obtained by polycondensation of maleic anhydride and products of poly(ethylene terephthalate) depolymerization with propylene glycol. Two methods of NC modification are performed: direct esterification with oleic acid, linseed, or sunflower oil FAs, and esterification/amidation with maleic acid/ethylene diamine (MA/EDA) bridging group followed by amidation with methyl ester of FAs. Increases of stress at break in the ranges from 148.8% to 181.4% and from 155.8% to193.0% for UPe/m‐NC composites loaded with 1 wt% of NC modified directly or via MA/EDA cross‐linker, respectively, are obtained. Results of the modeling of tensile modulus, by using the Cox–Krenchel model, show good agreement with experimentally obtained data. The effect of FAs' cross‐linking capabilities on the dynamic‐mechanical and thermal properties of the UPe/m‐NC is studied. Cross‐linking density, modulus, and Tg of the nanocomposite show appropriate relation with the unsaturation extent/structure of NC modification. 相似文献
A composite material consisting of hydroxide‐modified hemp fibres and euphorbia resin was produced. The composites were tested in tension, short‐beam interlaminar shear stress and in impact. There was an increase in the tensile strength and modulus for resins with high‐hydroxyl‐group based composites. Similar results were obtained for interlaminar shear stress while low‐hydroxyl group euphorbia resin based composites exhibited high impact strength. The euphorbia resin with high hydroxyl content yielded composites with high stiffness. The use of euphorbia‐based resins in composite manufacture increases the value of the euphorbia oil as well as creating a new route of composite manufacturing.
The potential of polymerization in a dispersed system as an attractive technique for polymer/graphene composite synthesis is discussed. This overview is focused on the preparation of graphene/polymer composite materials by two methods: (i) emulsion mixing or blending of polymer and graphene aqueous dispersions, and (ii) in situ polymerization in a dispersed system (emulsion, miniemulsion, microemulsion, and Pickering‐stabilized emulsion). Various methods for the stabilization of graphene nanoplatelets (GNPs) prior to composite preparation are presented, and the established specific interactions between the filler and the matrix are discussed. The determination of the electrical conductivity and the opportunity offered by polymerization in a dispersed system for the formation of a segregated network of graphene filler in the frame of a polymer matrix are presented. The mechanical and thermal properties of the composites are also discussed. A short summary of the open questions regarding the synthesis of water‐borne polymer/graphene composites is presented.
In this work, an efficient approach to improving the fire retardancy and smoke suppression for intumescent flame‐retardant polypropylene (PP) composites is developed via incorporating functionalized sepiolite (organo‐modified sepiolite [ONSep]). The PP composites with different amounts of intumescent flame retardants and ONSep were prepared by melt compounding. The morphology, thermal behavior, fire retardancy, smoke suppression, and mechanical property of flame‐retardant PP composites were studied. The results indicate an appropriate amount of ONSep in the flame‐retardant PP composites can increase thermal degradation temperature and char formation as well as a reduction of the peak heat release rate and total heat release; moreover, the addition of ONSep significantly decreases the CO production, total smoke production, smoke production rate, and smoke temperature. Simultaneously, the impact strength of intumescent flame‐retardant PP composite is also maintained by introducing an appropriate amount of ONSep as compared with that without ONSep. 相似文献
Solar light responsive polymer composites which can deform their shape according to the variation in sunlight power density are prepared by incorporating the solar light photothermal filler of Sm0.5Sr0.5CoO3 (SSC) into crosslinked poly[ethylene‐ran‐(vinyl acetate)] (EVA). Dual shape‐memory effect, temperature‐memory effect, and reversible bidirectional shape‐memory effect are all achieved in such EVA‐SSC composites. Dual shape‐memory effect with fixation ratio over 99% and recovery ratio over 95% is presented, while the responsive power density is adjusted from 0.4 to 0.1 w cm?2 by simply decreasing the programming temperature from 140 to 50 °C. Furthermore, during a cyclic variation in power density from 0 to 0.3 w cm?2 and back to 0 w cm?2 in 6 min, the composite specimens show a reversible angle deformation. Finally, a sunlight‐adaptive circuit switch is demonstrated using such composites, automatically turning off the LED lamp and turning on the motor fan according to the sunlight power density.
Composites with several hierarchical structures were prepared by using different clays, compatibilizers, and PPs. TGA showed that the thermal stability of the composites can be strongly improved, under either inert or thermo‐oxidative conditions, depending on the type of clay and its morphology. Drastic increases in the temperature of the maximum rate of weight loss (ΔTpeak ≈ 170 °C) under thermo‐oxidative conditions were observed depending on the clay dispersion. Furthermore, some composites had a complex multi‐step degradation behavior instead of a single‐step process related with different clay morphologies that can be present simultaneously. Finally, it was concluded that the TGA has a higher sensitivity toward the composite morphology than the mechanical properties.
A two‐step method is suggested to predict the Young's modulus of polymer nanocomposites assuming the interphase between polymer matrix and nanoparticles. At first, nanoparticles and their surrounding interphase are assumed as effective particles with core–shell structure and their modulus is predicted. At the next step, the effective particles are taken into account as a dispersed phase in polymer matrix and the modulus of composites is calculated. The predictions of the two‐step method are compared with the experimental data in absence and presence of interphase and also, the influences of nanoparticles size as well as interphase thickness and modulus on the Young's modulus of nanocomposites are explored. The predictions of the suggested model show good agreement with the experimental data by proper ranges of interphase properties. Moreover, the interphase thickness and modulus straightly affect the modulus of nanocomposites. Also, smaller nanoparticles create a higher level of modulus for nanocomposites, due to the large surface area at interface and the strong interfacial interaction between polymer matrix and nanoparticles.
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