Thermal properties of polypropylene nanocomposites: Effects of carbon nanomaterials and processing (original) (raw)
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Polymer Engineering & Science, 2011
Carbon nanotubes (CNTs) have been added to polypropylene (PP) matrix to improve the overall performance of composites. The mixing process has been carried out by melt compounding using a twin screw co‐rotating extruder with different CNTs amounts in the 0.5–10 wt% from a concentrated PP‐CNTs masterbatch (20 wt% CNTs). Results show a remarkable increase in tensile strength and elastic modulus while a decrease in elongation at break is detected. With regard to thermal behavior, a remarkable increase in thermal stability at high temperatures (decomposition process studied by thermogravimetric analysis) is obtained as the CNTs amount increases. In addition to this improvement, a noticeable increase in thermal stability at medium temperatures (degradation onset determined by differential scanning calorimetry, DSC) is also observed. In a similar way, other property related to thermal and mechanical performance, such as Vicat softening temperature (VST) is improved with CNTs content. The o...
Crystallization and thermal stability of polypropylene/multi-wall carbon nanotube nanocomposites
Philosophical Magazine Letters, 2016
Polypropylene (PP)/multi-wall carbon nanotube (MWCNT) nanocomposites were prepared via a melt compounding method using a twin-screw extruder. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the crystallization and thermal stability of the nanocomposites. The DSC analysis results revealed that the existence of MWCNTs in a PP matrix, which acted as a nucleating agent enhancing the crystallization process of PP matrix. This behaviour was manifested by an increase in the crystallization temperature and crystallinity index of the nanocomposites. Additionally, the TGA results showed that the addition of MWCNTs dramatically increased the thermal stability of the PP/MWCNT nanocomposites. Generally, MWCNT type C-70P showed improved crystallization and better thermal stability of the nanocomposites compared to type C-150P.
Polymers
In this paper, nanocomposites based on polypropylene (PP) filled with up to 5 wt.% of multi-walled carbon nanotubes (MWCNTs) were investigated for determining the material property data used in numerical simulation of manufacturing processes such as the injection molding and extrusion. PP/MWCNT nanocomposite pellets were characterized for rheological behavior, crystallinity, specific volume and thermal conductivity, while injection-molded samples were characterized for mechanical and electrical properties. The addition of MWCNTs does not significantly change the melting and crystallization behavior of the PP/MWCNT nanocomposites. The effect of MWCNTs on melt shear viscosity is more pronounced at low shear rates and MWCNT loadings of 1–5 wt.%. However, with the addition of up to 5 wt.% of MWCNTs, the PP/MWCNT nanocomposite still behaves like a non-Newtonian fluid. The specific volume of the PP/MWCNT nanocomposites decreases with increasing MWCNT loading, especially in the MWCNT range...
Journal of Materials Research and Technology, 2019
In this study, multi-walled carbon nanotube (MWCNT) filled polypropylene (PP) nanocomposites prepared by melt processing methods by employing extruder and injection molding techniques were examined with various characterization methods and test procedures, in detail. Aim and novelty of the work were to merely investigate the effects of amount and dispersion of MWCNTs on mechanical, thermal and rheological properties of PP including no compatibilizer and thus chemical interaction and/or interfacial adhesion effect. The mechanical test results showed that the incorporation of MWCNTs increased the tensile strength (18.4%), flexural strength (35.2%) and modulus of elasticity (45%) while it decreased the impact strength (18%) and elongation at break (690%) values of PP/MWCNT nanocomposites. Thermal analysis data revealed that the MWCNT addition slightly increased the crystallization peak onset and peak maximum temperatures of PP under non-isothermal conditions. Frequency-dependent melt rheological behaviors of nanocomposites in linear viscoelastic regime pointed out that the storage modulus (G'), loss modulus (G"), complex viscosity (Á*), and relaxation time of PP increased with the increasing amount of MWCNT. Non-linear rheological tests such as creep and stress relaxation also depicted that nanocomposites exhibited lower creep strain and relaxation rate than PP. Based on the thermal and mechanical test results, 0.3 wt% of MWCNT could be considered as the critical filler amount also called as "percolation threshold" for improving the solid-state physical properties of PP/MWCNT nanocomposites under the circumstances of no compatibilizer.
Journal of Applied Polymer Science, 2013
Modulated differential scanning calorimetry (MDSC) was used to measure the complex specific heat of the crystallization and melting transitions of nanocomposites of isotactic polypropylene (iPP) and carbon nanotubes (CNT) as function of CNT weight percent and temperature scan rate. In the last few years, great attention has been paid to the preparation of iPP/CNT nanocomposites due to their unique thermal and structural properties and potential applications. As the CNT content increases from 0 to 1 wt %, heterogeneous crystal nucleation scales with the CNT surface area. Above 1 wt %, nucleation appears to saturate with the crystallization temperature, reaching 8Kabovethatoftheneatpolymer.Heatingscansrevealacomplex,two−step,meltingprocesswithasmallspecificheatpeak,firstobserved8 K above that of the neat polymer. Heating scans reveal a complex, two-step, melting process with a small specific heat peak, first observed 8Kabovethatoftheneatpolymer.Heatingscansrevealacomplex,two−step,meltingprocesswithasmallspecificheatpeak,firstobserved8 K below a much larger peak for the neat iPP. For iPP/CNT samples, these two features rapidly shift to higher temperatures with increasing / w and then plateau at $3 K above that in neat iPP for / w ! 1 wt %. Scan rates affect dramatically differently the neat iPP and its nanocomposites. Transition temperatures shift nonlinearly, while the total transition enthalpy diverges between cooling and heating cycles with decreasing scan rates. These results are interpreted as the CNTs acting as nucleation sites for iPP crystal formation, randomly pinning a crystal structure different than in the neat iPP and indicating complex transition dynamics.
Journal of Thermoplastic Composite Materials, 2012
Multi-walled carbon nanotubes (CNTs) were functionalized on treatment with nitric acid and the surface-modified CNT was characterized using Fourier transform infrared spectroscopy (FTIR). Isotactic polypropylene (iPP)/CNT composites at different CNT loadings (ie, 0.1, 0.25, 1.00, and 5.00 wt%) were prepared by melt blending in a mini blender. The differential scanning calorimetric (DSC) studies showed the nucleating effect of CNTs on the crystallization behavior of iPP. Results of X-ray diffraction studies are in ...
Processing effects on the thermo-physical properties of carbon nanotube polyethylene composite
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2009
Processing effects on the thermo-physical and mechanical properties of multiwalled carbon nanotubes reinforced polyethylene composites are reported. Composites were prepared by solution mixing followed by melt processing through different extrusion processing times (11 and 45 min). The composites were then pressed using hot compression molding. Thermogravimetric analysis, differential scanning calorimetry and tensile test were conducted to study their thermo-physical and mechanical properties. Results show that processing has strong effects on the thermal and mechanical behavior of the composites. 45 min processed samples crystallize easier and demonstrated superior mechanical properties when compared to sample processed for 11 min.
Crystallization and melting behavior of isotactic polypropylene and carbon nanotube nanocomposites
2009
Polymer nanocomposites (PNCs) are the most recent development in the field of polymer science and technology. Geared toward creating novel polymer based materials, PNCs are the largest commercial application for nanotubes. Spherulitic polymer crystal growth was changed by inducing new fibrillar crystals on the surface of carbon nanotubes. Upon isothermal melt crystallization at 135^oC, CNTs lead to monoclinic crystal growth perpendicularly to the long axis of the nanotubes, explained by the multiple nucleation centers formed at the interface of the carbon nanotube and the polymer chains. Using Microscopic Transmission Ellipsometry (MTE), the sign of the alpha crystallographic phase was determined as positive. Using Differential Scanning Calorimetry (DSC), a decrease in the Avrami exponent was measured with increase of concentration of nanotubes.
Effect of carbon nanotubes content on crystallization kinetics and morphology of polypropylene
2009
Thermoplastic nanocomposites were prepared in a laboratory mixer using polypropylene (PP) and different amounts of single-walled carbon nanotubes (SWNT) in the range 0.25-2 wt%. The effect of SWNT content on the thermal and mechanical properties and also morphology of the PP/SWNT nanocomposites were studied. The results obtained from nonisothermal crystallization of PP and the nanocomposites, which were carried out using the differential scanning calorimetry technique, showed that not only the overall rate of crystallization of PP increased when SWNT was added to the polymer but also the rate of nucleation was higher and the crystallite size distribution was more uniform for the nanocomposites than for PP. From the optical microscopy studies, it was found that the PP spherulites decreased in size when SWNT was introduced into the polymer and also the mature spherical shaped crystals of PP changed in part to the immature kidney-or beanshaped crystal forms in the nanocomposites. In addition, the crystallization kinetics was also studied by using isothermal spherulitic growth rate, and the values of nucleation constant, K g , and end surface free energy, s e , were calculated for PP and the nanocomposites according to Lauritzen-Hoffman theory. The reductions of these two parameters were in agreement with the fact that the rate of crystallization of PP in nanocomposites was higher than that of the pristine polymer.