Higher Crystallinity Values Research Articles

The investigation of the mechanical thermal and physical properties of using waste toner/MCC/old newspaper fiber in polypropylene hybrid composites

AbstractIn this study, the effects of polypropylene (PP) composites produced by adding 10% old newspaper fibers (ONP), 5% microcrystalline cellulose (MCC), 3% polypropylene carbonate (PPC), and waste toner from 1% to 4% on the mechanical properties, physical properties, morphological, and thermal properties were investigated. According to the FTIR‐ATR and SEM‐EDS analysis results, it was determined that a significant part of the waste toner used in the study consisted of polystyrene co‐acrylate, and the remaining part consisted of carbon black and trace amounts of silicate. In the research, it was determined that the flexural and tensile strengths of MCC/ONP/PP composites containing 1% waste toner and 3% PPC increased by 13% and 46%, respectively, compared to the control sample. Additionally, the samples with the lowest water absorption values were measured in composites containing 1% waste toner and 3% PPC. The highest crystallinity value (50.75%) was obtained with the use of 1% waste toner and 3% PPC in MCC/ONP/PP composites. However, with waste toner usage above 1%, the mechanical, thermal properties, and water absorption rate have slightly decreased. As a result of the study, it was concluded that up to 1% waste toner with 3% PPC can be used successfully in MCC/ONP/PP composites.

Effects of chemical treatment and gamma-ray irradiation on the structure-properties of sunn hemp and okra hessian cloth reinforced high-density polyethylene composites: A comparative study

Okra hessian cloth and Sunn hemp hessian cloth were prepared and treated with 5, 10, and 15 wt% alkali solutions for 1 h. The optimized concentration of alkali is 10 wt%. The untreated and treated hessian cloths reinforced high-density polyethylene (HDPE) composites were then prepared using the compression molding method. Alkali-treated, and 55 wt% fiber contents reinforced composites showed improved mechanical properties among 40, 45, 50, 55, 60, and 65 wt% fiber contents composites. 55 wt% fiber contents reinforced composites were then irradiated under gamma-ray at doses 2.5–7.5 kGy at the rate of 6 kGy/h. According to the X-ray diffraction analysis results, only alkali-treated Okra reinforced, and Sunn hemp-reinforced HDPE composites had higher crystallinity values than untreated and irradiated composites. Surface micrographs showed that the Okra-HDPE and Sunn hemp-HDPE had better matrix and fiber attachment. Cross-linking between the two varieties of fibers and matrix was seen using Fourier-transform infrared (FTIR) spectroscopy. Both irradiated composites exhibited greater hydrophobicity in their water intake characteristics compared to untreated and alkali-treated composites. The tensile strength ( TS) value of Sunn hemp composite for 5 kGy gamma-ray irradiation dose is 68 MPa, which is 14% and 42% higher than that of treated and untreated composites, respectively. For comparison, the TS value for 5 kGy dose irradiated Okra composite is 66 MPa, which is 17% and 44% higher than that of treated and untreated composites, respectively. Young’s modulus ( Y) values of irradiated Okra composite and irradiated Sunn hemp composite showed higher values than that of other composites. Both irradiated composites have better thermal and structural characteristics than untreated and alkali-treated composites.

Effect of waste toner powder on the performance of microcrystalline cellulose‐talc reinforced polypropylene hybrid composites

AbstractThis study examines reducing the environmental hazards of toner waste and producing low‐cost: high‐performance value‐added hybrid polypropylene‐PP‐composites. The incorporation of microcrystalline cellulose (MCC) and inorganic filler(s) into a polymer matrix leads to superior performance and environmental advantage compared to inorganic‐filled polymer composites. Waste toner (WT) was used up to 2% by weight with increments of 0.5 and the other fillers: MCC/talc/polypropylene carbonate loading ratios were kept constant as 5/10/3 wt% in this study. The production process of hybrid PP composites was carried out with single‐screw extrusion and molding. Chemical and thermal characterization of the filler and the hybrid PP composites were performed by FTIR and it was revealed that the main resin of WT consists of polystyrene co‐acrylate. In DSC analysis, the highest crystallinity value was calculated as 52.36% in the composite containing 1.5% waste toner. SEM micrographs proved the PPC prompts the dispersion quality of MCC and talc in the PP matrix. Mechanical, water absorption and surface properties of the hybrid composites were enhanced by adding WT at 1 and 1.5 wt%. Above this ratio, all properties of the hybrid composites moderately decreased. In light of the results, the WT could be utilized as a filler up to 1.5% in the PP‐matrix.Highlights TS of the composites increased by increasing the waste toner content to 1.5%. PP‐based hybrid composites had higher flexural properties than unfilled PP. The crystallinity increased up to the addition of 1.5% wt. PPC‐coupling agent promoted the interaction between talc/MCC and PP matrix.

Physicochemical and Technofunctional Comparison of Starch from Varieties of Native Potato (Solanum Phureja) with Commercial Starches

Due to the high genetic variability of the potato, the starch can exhibit different properties of interest to the industry. With the present investigation, it is intended to know these differentiating characteristics in comparison with commercial sources that can be useful in different sectors. Therefore, the objective of this research was to establish a comparison between potato starches extracted from native varieties (Solanum phureja) with commercial potato and corn starches. A physicochemical analysis was carried out, for which characteristics such as amylose content, phosphorus, resistant starch (RS), slow digestibility starch (SDS), rapid digestibility starch (RDS), granule shape, granule size and crystallinity were evaluated. The technofunctional analysis included variables such as amylographic, thermogravimetric and differential scanning calorimetry analysis. The starches of the native varieties exhibited differential characteristics with respect to the commercial starches. Andina variety obtained the highest peak viscosity (8714 cP), followed by Ratona Blanca starch (6148 cP). In addition, these two varieties had the highest content of resistant starch (33.14±0.8) % and (28.9±0.7) % respectively), higher content of amylose (33.9 % and 35.5 % respectively), phosphorus (>0,08 % for both varieties), high crystallinity and higher enthalpy values (> 19 J/g for both varieties), which make them materials of potential use in different industries. The correlations presented between variables such as resistant starch (RS), enthalpy and crystallinity, showed possible differences at the structural level, which highlighted the differential characteristics of each starch.

Enhanced mechanical and thermal properties of graphene nanoplatelets‐reinforced polyamide11/poly(lactic acid) nanocomposites

AbstractThe present paper aims to obtain a sustainable nanocomposite by using bio‐based polyamide 11 and biodegradable poly (lactic acid) blend as matrix and graphene nanoplatelets (GNP) as nanofiller. GNP was incorporated in the PA11/PLA blend matrix in the ratio of 0.5‐1‐3‐5‐10 wt% through the twin‐screw extruder. The crystallinity of PA11 in the blend, which was 12.9%, increased with the inclusion of GNP, and the highest crystallinity value was observed at 20% for the 1GNP sample. The crystallinity of PLA in the blend, which was 2.3%, increased to 4.6% with 5 wt% GNP addition. The inclusion of GNP to PA11/PLA improved the thermal degradation temperatures and increase the char residue. Also, increments were observed for storage modulus, loss modulus, and glass transition temperature of the matrix with the inclusion of GNP. The addition of GNP caused the tensile strength of the matrix to increase first and then decrease at higher amounts due to the agglomerations. 0.5–1 wt% GNP increased tensile strength by 10% and 5%, respectively. Increasing the amount of GNP to 10 wt% led to a sharp decrease in tensile strength by 24%. Overall, GNP is a suitable nanofiller to enhance the thermal and mechanical features of the PA11/PLA blend.

Structure-digestibility relationship from noodles based on organocatalytically esterified regular and waxy corn starch obtained by reactive extrusion using sodium propionate

Health-promoting starchy noodles (spaghetti-type pastas) were manufactured from organocatalytically esterified regular and waxy corn starches. The noodles were obtained via reactive extrusion (REx) using sodium propionate (NaPro) as a precursor of propionic acid (PAc – short-chain fatty acid, SCFA) and tartaric acid (TAc) as a food-grade green organocatalyst. The values of degree of substitution (DS) determined by titration varied between 0.78 and 1.22. Solid-state 13 C CP MAS NMR spectra evidenced that all Pro-containing noodle systems were propionylated, regardless of the use of the organocatalyst. However, the determination of DS values could not be adequately calculated from the solid-state 13 C CP MAS NMR spectra, since the organocatalyst and the unreacted Pro inevitably remained embedded in the REx-processed noodle systems. The results also suggest that amylose (amorphous regions of starch) is more susceptible to being esterified by Pro than amylopectin (crystalline regions of starch). Greater thermal resistance, more compact morphologies and higher crystallinity values were evidenced by increasing the DS values. The long-range ordered structure was dominated by the A-type crystalline structure for all noodle systems studied. Notwithstanding, V-type structure was also evidenced, and related to short-range ordered crystalline structures. Organocatalytically propionylated corn starch-based noodle systems had lower free Pro values compared to non-organocatalyzed propionylated corn starch-based noodle systems upon pancreatic digestion, thus confirming the positive effect of the use of organocatalyst for the esterification of Pro onto starch. All propionylated corn starch-based noodle systems showed slower starch digestibility, regardless of amylose content. • Health-promoting starchy noodles were manufactured from organocatalytically esterified regular and waxy corn starches. • All propionate-containing noodle systems were propionylated under reactive extrusion conditions, regardless of the use of the organocatalyst. • Amylose is more susceptible to propionylation than amylopectin. • All propionylated corn starch-based noodle systems showed slower starch digestibility, regardless of amylose content.

Synthesis, characterization and heating efficiency of Gd-doped maghemite (γ-Fe2O3) nanoparticles for hyperthermia application

In this paper, sol-gel technique was used to prepare Gd-doped γ-Fe2O3 nanoparticles and their heating efficiency for magnetic hyperthermia application was investigated. The obtained nanoparticles are characterized by several techniques. The structural properties are performed by X-ray diffraction (XRD), energy-dispersive X-ray spectrometer (EDAX) and X-ray Photoelectron Spectroscopy (XPS), while the morphology is investigated by Transmission electron microscopy (TEM). The magnetic properties and heating ability under an alternating magnetic field are performed by vibrating sample magnetometer (VSM) and magnetherm respectively. XRD, XPS and TEM results confirmed the maghemite (γ-Fe2O3) phase, the presence of Gd ions and crystallinity. VSM hysteresis loops showed a negligible coercive field and remanence suggesting superparamagnetic behavior, which was also confirmed by Langevin method. Heating efficiency under an AC alternating magnetic field measurements showed that doped and un-doped samples display high heating ability and reached magnetic hyperthermia (42 °C) in relatively short times with shorter time (∼2 min) observed for γ-Fe2O3 compared to 6 min for Gd (5%) doped γ-Fe2O3 nanoparticles. The specific absorption rate (SAR) values decreased with increased concentration of Gd but remain considerable for all doped samples (up to 40W/g for Gd (5%)). The high crystallinity, superparamagnetic behavior and good SARs values make these nanoparticles a promising candidate for hyperthermia application.

Degradation of a mechanically recycled polylactide/halloysite nanocomposite in an ethanolic food simulant

<p class="JARTEAbstract">This work aims to study the effect of immersion in a ethanolic food simulant in mechanically recycled poly(lactic acid) (PLAR) and its nanocomposites reinforced with halloysite nanotubes (HNT). PLAR was obtained by subjecting PLA to an accelerated ageing process, which includes photochemical, thermal and hydrothermal ageing steps, followed by a final demanding washing step. PLAR was further reinforced with 4 %wt. HNT to improve the properties of the PLAR films. The materials were melt compounded by melt extrusion and processed into films by compression molding. The resulting films were exposed to food simulant D1 (50 %vol. ethanol solution) for 10 days at 40 °C. The intrinsic viscosity, crystallization behavior, thermal stability as well as the mechanical performance were analyzed before and after the contact with the food simulant. The swelling, plasticizing and hydrolyzing effect of the food simulant led to an important decrease of the intrinsic viscosity of all the samples, along with a significant increase of the crystallinity. Thermal stability was negatively affected by the decrease of the molecular weight, while the high crystallinity values resulted in materials with higher Vickers hardness values after the immersion in the food simulant.</p>

Tailoring the triboelectric output of poly-L-lactic acid nanotubes through control of polymer crystallinity

Triboelectric devices capable of harvesting ambient mechanical energy have attracted attention in recent years for powering biomedical devices. Typically, triboelectric energy harvesters rely on contact-generated charges between pairs of materials situated at opposite ends of the triboelectric series. However, very few biocompatible polymeric materials exist at the ‘tribopositive’ end of the triboelectric series. In order to further explore the use of triboelectric energy harvesting devices within the body, it is necessary to develop more biocompatible tribopositive materials and look into ways to improve their triboelectric performance in order to enhance the harvested power output of these devices. Poly-L-lactic acid (PLLA) is a tribopositive biocompatible polymer, frequently used in biomedical applications. Here, we present a way to improve the triboelectric output of nanostructured PLLA through fine control of its crystallinity via a customised template-assisted nanotube (NT) fabrication process. We find that PLLA NTs with higher values of crystallinity (∼41%) give rise to a threefold enhancement of the maximum triboelectric power output as compared to NTs of the same material and geometry but with lower crystallinity (∼13%). Our results thus pave the way for the production of a viable polymeric and biocompatible tribopositive material with improved power generation, for possible use in implantable triboelectric nanogenerators.

The effect of Ag, ZnO, and CuO nanoparticles on the properties of the compatibilized polyethylene/thermoplastic starch blend films

AbstractIn this study, the effects of Ag, ZnO, and CuO nanoparticles (NPs) on the mechanical, thermal, and biodegradability properties of the compatibilized polyethylene (PE)/thermoplastic starch (TPS) blends were investigated. Polyethylene‐grafted maleic anhydride (PE‐g‐MA) was used as the compatibilizer. The compatibilized PE/TPS blends with different NPs were prepared by melt mixing method in a laboratory scale extruder and then pressurized in the press machine. The use of ZnO NP together with the compatibilizer in PE/TPS‐based films significantly increased the tensile stress values. The use of different type NPs did not cause any significant change in the thermal stability of PE/TPS‐based films. However, the effects of NPs were observed on the TPS degradation steps. The prepared films with different NPs showed an antibacterial activity between 60% and 70%. The highest crystallinity value was obtained in Ag NP containing films, among others. According to scanning electron microscopy analysis, better distribution was observed for ZnO and Ag NPs than CuO NP. In general, it can be said that the addition of NPs to PE/TPS‐based blends significantly reduces the partial biodegradability of the resulting films.

Isolation and characterization of Cellulose Nanofiber from Subang Pineapple Leaf Fiber waste produced using Ultrafine Grinding method

Pineapple leaf fiber (PALF) is one of natural fibres that has high cellulose content. However, pineapple plants must be replaced with new plants once it is harvested, leaving the leaves as waste. In this research, the isolation and characterization of Subang based PALF were conducted. Chemical pre-treatments including alkaline treatment with Sodium Hydroxide and bleaching to remove nanocellulosic constituents such as lignin and hemicellulose were conducted. This process was followed by mechanical treatment using ultrafine grinder to produce cellulose nanofiber (CNF). Transmission Electron Microscopy (TEM) images showed that the CNF had 45-75 nm in diameters. The percentage crystallinity was determined by X-ray diffraction (XRD). The crystallinity values of raw PALF, treated PALF, and CNF were 74.97%, 76,29%, and 69.52% respectively. Fourier Transform Infrared (FTIR) spectroscopy analysis was carried out to investigate the chemical structure changes after both chemical and mechanical treatments. The presence of a peak that related to cellulose confirmed that the process was well conducted. These results indicated that PALF waste could become added value to agricultural waste and expected to become reinforcement agent in nanocomposite for structural application since PALF had low aspect ratio and had high percentage crystallinity values.

A correlation on ultrasonication with nanocrystalline cellulose characteristics

Catalytic ionic liquid hydrolysis of cellulosic material have been considered as a green and highly efficient dissolution process. However, application of a pre-treatment process, i.e; ultrasonication enhances the hydrolysis of cellulose in ionic liquid by providing mechanical force. In this paper, we describe the impact of both chemical and mechanical approaches to produce nanocrytalline cellulose (NCC) with anticipated particle size, and crystallinity with improved yields. The ultrasonication treatment was evaluated in terms of treatment time and vibration amplitude. It was found that the lowest ultrasonication time (5 min) produced the NCC of highest crystallinity (73 %), but the lowest yield (84 %). In contrary, the highest ultrasonication vibration amplitude at 90 % produced NCC with highest crystallinity value (67 %) as well as yields (90 %). It concludes that ultrasonic pre-treatment improves the hydrolysis process of cellulose in ionic liquid with increasing yield and crystallinity of NCC.

Crystallization-driven microstructure changes during microphase separation for environment-friendly thermoplastic triblock copolymer elastomers

A study on the crystallization-driven microstructure changes during microphase separation for a series of high transparent semicrystalline thermoplastic triblock copolymer elastomers (TBCPEs), polylactide-b-polyisoprene-b-polylactide (PLA-b-PI-b-PLA) was conducted in this work. A series of PLA-b-PI-b-PLA TBCPEs with different molecular masses of PI midblock and same molecular mass of PLA end blocks were synthesized. Differential scanning calorimetry was applied to demonstrate the microphase separation and crystallization behaviors of these samples. Small-angle X-ray scattering and ultra-small-angle X-ray scattering techniques were employed to investigate the different microphase-separated structures between solvent-cast and melt quenched PLA-b-PI-b-PLA films. It was disclosed that crystallization of the PLA end blocks could obviously enlarge the interdomain distance if the microphase-separated structures in PLA-b-PI-b-PLA took lamella or cylinder formats, while much less effect was noticed if the structures took sphere format. Wide-angle X-ray diffraction measurement demonstrated that PLA end blocks in PLA-b-PI-b-PLA could crystallize and eventually form α-form crystals with relatively high crystallinity values. The α-form crystals stay clear with high transparency even with high crystallinity values, because the initially formed microphase-separated structures could confine crystallization of PLA end blocks, preventing the growth of any large PLA crystals eventually.

Influence of Post-Treatment Media on Morphological Changes in Transient Macromolecules of Polymeric Fibers

Abstract There is a growing literature investigating the effects of thermal annealing and green solvent exposure on the microstructural changes, in general, and transient structures in polyester fibers, in particular, using such techniques as birefringence, differential scanning calorimetry, X-ray diffraction, and dynamic mechanical analysis. The results obtained from these studies consistently indicate that transient structures in polyester fibers strongly depend on the medium used so that treatment in different media produces important changes such as the transformation of the intermediate domain into an amorphous or crystalline region. Compared to polyester samples annealed at high temperatures over long treatment times, those exposed to green solvents yield higher values of crystallinity, orientation, density, transient structure, crystallite size in lateral directions, and elastic modulus but lower values of fractional free volume. Being environmentally friendly, green solvents may, thus, be considered as superior replacements for the conventional materials used in thermal annealing, especially because they change the fine structure of polyester fibers over shorter treatment times and at lower temperatures.

Mid-Miocene climatic optimum: Clay mineral evidence from the red clay succession, Longzhong Basin, Northern China

The Mid-Miocene Climatic Optimum (MMCO) is one of Earth's most recent prolonged warming events, recorded in both the deep ocean and mid- to high-latitude continents. Thick Cenozoic deposits in the Longzhong Basin, Northwest China, provide great potential for characterizing the MMCO, but have not been well documented. In this study, we carry out clay mineralogical and geochemical analyses of the Miocene red clay succession from the eastern Longzhong Basin, employing X-ray diffraction and geochemistry, and discuss the climatic characteristics of the MMCO. The results reveal that the MMCO occurred at 16–14Ma and is associated with relatively high kaolinite and smectite contents, high illite crystallinity values and kaolinite/(illite+chlorite) ratio, and lower chlorite and illite contents. These clay mineral assemblages confirm a warm and moist climate during the MMCO. Furthermore, the SiO2/Al2O3 ratio declined with increasing Al2O3, indicative of greater precipitation and intensified weathering during this period. When compared with local and global records, we find that our clay mineral records reflect regional climatic change superimposed upon global climatic trends during the MMCO. It is suggested that a high concentration of CO2, and associated global warming, may have been responsible for the MMCO, rather than the uplift of the Tibetan Plateau.

The mineralogy of newly formed dust in active galactic nuclei

The tori around active galactic nuclei (AGN) are potential formation sites for large amounts of dust, and they may help resolve the so-called dust budget crisis at high redshift. We investigate the dust composition in 53 of the 87 Palomar Green (PG) quasars showing the 9.7 μm silicate feature in emission. By simultaneously fitting the mid-infrared spectroscopic features and the underlying continuum, we estimate the mass fraction in various amorphous and crystalline dust species. We find that the dust consists predominantly of alumina and amorphous silicates, with a small fraction in crystalline form. The mean crystallinity is 8±6%, with more than half of the crystallinities greater than 5%, well above the upper limit determined for the Galaxy. Higher values of crystallinity are found for higher oxide fractions and for more luminous sources.

Cellulose nanofibers produced from banana peel by chemical and mechanical treatments: Characterization and cytotoxicity assessment

Cellulose nanoparticles from a vegetable source (cellulose fiber) have been evaluated for future use as reinforcement of polymeric matrixes (e.g., biodegradable films). Cellulose nanoparticles have numerous advantages: they are inexpensive and biodegradable, and they originate from renewable sources. Here, cellulose nanofibers (CNFs) were isolated from banana peel by chemical (alkaline treatment and bleaching followed by acid hydrolysis with 0.1, 1, or 10% (v/v) H2SO4) and mechanical (high pressure homogenizer) treatments. Atomic Force Microscopy (AFM) analysis showed all treatments effectively isolated banana fibers at the nanometer scale (average diameter of 3.72 nm). CNFs displayed ζ-potential values ranging from −37.60 to −67.37 mV, which prevented their aggregation. CNFs had high crystallinity values, from 63.1 to 66.4%, which indicated they could be good reinforcing agents. FTIR results confirmed that the chemical and mechanical treatments removed the amorphous fractions. Regarding cytotoxicity, low CNF concentrations (50–500 μg/mL) did not cause cell death, but CNFs at concentrations above 1000 μg/mL significantly decreased cell viability. The use of different sulfuric acid concentrations provided more detailed knowledge of the treatment methods and CNF features, which could help to improve the CNF production process. The combination of chemical and mechanical treatments proved to be an efficient strategy to prepare CNFs from banana peels as a potential reinforcing agent of polymeric matrixes (e.g., food packaging).

The precursors effects on biomimetic hydroxyapatite ceramic powders

In this study, effects of the starting material on chemical, physical, and biological properties of biomimetic hydroxyapatite ceramic powders (BHA) were investigated. Characterization and chemical analysis of BHA powders were performed by using XRD, FT-IR, and ICP-AES. Microstructural features such as size and morphology of the resulting BHA powders were characterized by using BET, nano particle sizer, pycnometer, and SEM. Additionally, biological properties of the BHA ceramic powders were also investigated by using water-soluble tetrazolium salts test (WST-1). According to the chemical analysis of BHA ceramic powders, chemical structures of ceramics which are prepared under different conditions and by using different starting materials show differences. Ceramic powders which are produced at 80°C are mainly composed of hydroxyapatite, dental hydroxyapatite (contain Na and Mg elements in addition to Ca), and calcium phosphate sulfide. However, these structures are altered at high temperatures such as 900°C depending on the features of starting materials and form various calcium phosphate ceramics and/or their mixtures such as Na-Mg-hydroxyapatite, hydroxyapatite, Mg-Whitlockit, and chloroapatite. In vitro cytotoxicity studies showed that amorphous ceramics produced at 80°C and ceramics containing chloroapatite structure as main or secondary phases were found to be extremely cytotoxic. Furthermore, cell culture studies showed that highly crystalline pure hydroxyapatite structures were extremely cytotoxic due to their high crystallinity values. Consequently, the current study indicates that the selection of starting materials which can be used in the production of calcium phosphate ceramics is very important. It is possible to produce calcium phosphate ceramics which have sufficient biocompatibility at physiological pH values and by using appropriate starting materials.

Enhancing the photocatalytic reduction of CO2 through engineering of catalysts with high pressure technology: Pd/TiO2 photocatalysts

Converting carbon dioxide (CO2) to hydrocarbons that can be used as fuel is beneficial from both environmental and economic points of view. However, more efficient catalysts should be developed to bring the process from laboratory to commercial scale. Thus, in this study, in order to improve the CO2 conversion process, Pd doped photocatalysts based on titanium dioxide (Pd/TiO2) are synthesized. The new catalysts are produced from alcohols and precursors of titania and Pd in the presence of supercritical carbon dioxide so the dispersion of metal species (palladium) into the TiO2 lattice is possible. Following this approach, photocatalysts with better or similar features (higher values of crystallinity, surface area, and improved absorbance in visible range) than those of commercial TiO2 have been produced. Moreover, methane and CO production rates up to 22 and 2 times higher than those corresponding to the commercial catalyst, respectively, have been attained with Pd/TiO2 photocatalysts synthesized in this work.

Processing–morphology–property relationships of polypropylene–graphene nanoplatelets nanocomposites

ABSTRACTPolypropylene (PP) nanocomposites reinforced with graphene nanoplatelets (GNPs) were prepared via melt extrusion. A special sheet die containing with two shunt plates was designed. The relationships among the flow field of the special die, exfoliation, and dispersion morphology of the GNPs in PP and the macroscopic properties of the nanocomposites were analyzed. Flow field simulation results show that the die with shunt plates provided a high shear stress, high pressure, and high velocity. The differential scanning calorimetry, X‐ray scattering, and electron microscopy results reveal that the nanocomposites prepared by the die with the shunt plates had higher crystallinity values and higher exfoliation degrees of GNPs. The orientation of the GNPs parallel with the extrusion direction was also observed. The nanocomposites prepared by the die with shunt plates showed a higher electrical volume conductivity, thermal conductivity, and tensile properties. This indicated that the high shear stress exfoliated the GNPs effectively to a thinner layer and then enhanced the electrical, thermal, and mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44486.