Preparation Of Polypropylene Research Articles

Density gradient structure foams prepared by novel two-step foaming strategy: Performance, simulation and optimization

Functional gradient foam materials play a crucial role in meeting the diverse performance and functionality requirements of modern engineering. Density gradients enable the distribution of mechanical, dielectric, and optical properties within materials, exhibiting a gradient representation. However, creating density gradients within foams poses a significant challenge, especially for semi-crystalline polymers. The paper proposed a novel two-step foaming method for preparing polypropylene (PP) foams with density gradient structure (DGS). Initially, a pre-foaming process was conducted to prepare PP pre-foams with uniform structure (US) at low temperatures, followed by a secondary foaming process on partially saturated PP pre-foams to fabricate PP DGS foams. By adjusting the duration of partial saturation time, PP foams with various DGS can be achieved. Compared with the commonly used one-step foaming method and uniform foaming method in the literature, the DGS foams prepared by the two-step foaming method exhibit not only a significant enhancement in mechanical property but also achieve the lowest thermal conductivity, while maintaining comparable and outstanding sound insulation performance. Finally, a comprehensive evaluation model using COMSOL Multiphysics was developed for the DGS foams, providing insights for optimizing foam performance through process enhancements.

Generation of nano-to-microplastics from polypropylene surfaces via femtosecond laser ablation in liquids with different viscosities

Preparation of polypropylene (PP) nano and microparticles, crucial for investigating the effects of plastics on both human health and the environment, presents a significant and immediate challenge. Utilizing an fs laser system in different liquid mediums such as water, dodecane, and hexadecane, we have successfully generated PP particles with sizes ranging from 1.8 to 4911 nm. This outcome is partly attributed to the constraint on plasma expansion caused by the viscosity of the liquid media. We investigated the areas of material removal and observed a transition from ordered to disordered removal patterns during this process. The formation of filaments and pillars within the material removal cavity, along with the deposition layer at the cavity edge, primarily occurred due to insufficient plasma formation at low laser energy levels. Furthermore, we observed neck-shaped filaments and nano cracks on the deposition surface, which were attributed to the heat effect during laser interaction with the PP substrate. Moreover, we collected distinct nano-Fourier transform infrared spectroscopy (FTIR) signals from both the nanoparticle area and the deposition layer, revealing a 2 cm−1 wavenumber difference between the two regions. This discrepancy proved to be a valuable method for distinguishing between the nanoparticle area and the deposition layer.

Dyeability and mechanical properties of banana fiber reinforced polypropylene composite

AbstractBanana fibers being highly strong and biodegradable, have always been an interesting aspect of polymer science. The research examines the pretreatment process to enhance the dyeability of banana fibers with synthetic dyes, followed by the preparation of polypropylene (PP) composites with dyed fibers to explore their mechanical properties. Raw banana fibers were extracted from the pseudo stems of banana plants for pretreating with sodium hydroxide and hydrogen peroxide and further dyed in the exhaust method using direct, basic, reactive, and vat dyes. Despite a decrease in fiber strength, the scoured‐bleached fibers appeared whiter and lustrous compared to untreated fibers. Direct dye exhibited a higher color strength (K/S) value of 20.7 and better wash fastness on average of 4‐3 rating compared to basic dye. Later polypropylene sheets were prepared using a Hot Plate Molding Machine, and composite specimens were fabricated by sandwiching the fibers between PP sheets and hot pressing. Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed minor bond formations between the dyed fibers and polypropylene matrix in composites showing significant bonding at NH, CH, and OH regions. The composites containing dyed fibers showed slight improvements in tensile strength and modulus which is at best 2% than that of untreated fiber.Highlights Direct and basic dyes were determined as the most suitable synthetic dyes. FTIR analysis revealed minimal bond formation between the fiber and PP matrix. Composites having dyed banana fiber showed little better mechanical features.

Preparation of polypropylene with photothermal conversion and hydrophilicity by one-step impregnation for efficient interfacial water evaporation

Solar-driven interfacial water evaporation is a technology that is currently attracting significant interest for tackling freshwater scarcity. However, the creation of porous membranes with photothermal conversion and hydrophilicity remains a challenging task. This study utilizes melt-blown polypropylene nonwoven (PP), a substrate with high porosity, low cost and high yield, to prepare evaporation membranes exhibiting photothermal conversion properties. The PP surface was treated with a one-step impregnation method to produce both shell and nanoparticles containing MnO2−x. The addition of MnO2−x grants the PP membranes both photothermal conversion and hydrophilicity simultaneously. Sunlight absorption efficiency of PP membranes covered with MnO2−x (M-PP) is 85.83%, and its hydrophilicity and porosity enable it to form an ultra-thin layer of water during evaporation, promoting rapid escape of vapors. Evaporation rate of M-PP membranes reach 1.02 kg m−2 h−1, much higher than that of PP and bulk water. In addition, M-PP membranes have excellent corrosion resistance, which is potentially valuable in treating wastewater and desalinating seawater.

Preparation of Polypropylene with Strain Hardening Characteristics via the Noncatalytic C–H Insertion of Azidoformate

Preparation of Polypropylene with Strain Hardening Characteristics via the Noncatalytic C–H Insertion of Azidoformate

Largely enhanced dielectric and thermal conductive properties of polypropylene composites by adding mixture of exfoliated boron nitride and liquid metal

For microelectronic fields, high dielectric, high insulating and high thermal conductive performances need to be simultaneously integrated in materials to improve devices’ performance, safety, and thermal management ability. Despite the huge potential of exfoliated boron nitride (BN)/polymer composites in them, the exfoliation of BN is difficult, leading to limited increases of dielectric and thermal conductive performance. Herein, BN is first exfoliated in liquid metal (LM) matrix by mechanical grinding, which activates the interaction between LM and BN to promote exfoliation. Then the one-pot mixture containing exfoliated BN and LM, is used as hybrid fillers (LM@BN) without separation for preparing polypropylene (PP)/LM@BN composites. The composites behave a remarked dielectric constant of 3.5 and thermal conductivity of 1.9 W/m·K at LM@BN content of only 5.5 vol%. Extra low dielectric loss (0.005) and low conductivity (10−11 S/cm3) of PP could be also maintained, due to suppressed space charges by the uniformly-dispersed exfoliated BN.

Evaluation of Thermal Properties of Composites Prepared from Pistachio Shell Particles Treated Chemically and Polypropylene.

The purpose of the present work was to prepare polypropylene (PP) matrix composited filled with chemically treated pistachio shell particles (PTx), and evaluate their effect on the composites’ thermal properties. PP-PTx composites were formulated in different PTx content (from 2 to 10 phr) in a mixing chamber, using the melt-mixing process. The PTx were chemically treated using a NaOH solution and infrared spectroscopy (FTIR). According to thermogravimetric analysis (TGA), the treatment of pistachio shell particles resulted in the remotion of lignin and hemicellulose. The thermal stability was evaluated by means of TGA, where the presence of PTx in composites showed a positive effect compared with PP pristine. Thermal properties such as crystallization temperature (Tc), crystallization enthalpy (∆Hc), melting temperature (Tm) and crystallinity were determinate by means differential scanning calorimetry (DSC); these results suggest that the PTx had a nucleation effect on the PP matrix, increasing their crystallinity. Dynamic mechanical analysis (DMA) showed that stiffness of the composites increase compared with that PP pristine, as well as the storage modulus, and the best results were found at a PTx concentration of 4 phr. At higher concentrations, the positive effect decreased; however, they were better than the reference PP.

Dielectric Properties of Polypropylene by Deashing Method for DC Polymer Film Capacitors

In this paper, a novel deashing method was proposed to prepare polypropylene (PP) materials with different ash contents (80 ~ 560 ppm). Effects of the ash on dielectric and energy storage characteristics of PP in polymer film capacitors were studied. The experimental results reveal that a low content of ash will help to improve the dielectric properties. Compared to the sample with 560 ppm of ash content, the PP film with 60 ppm ash possesses a lower DC conductivity (1.85×10-14S/m). After the purification, the decline of the ash content in PP prevents the local electric field distortion and enhances the breakdown strength, which is beneficial for the improvement of the discharge energy density. Meanwhile, the reduction in the number of carriers ionized by the ash weakens the transport behavior and reduces the conductivity. It is concluded that the PP with high purity shows a great potential in polymer film capacitors.

Dielectric and Energy Storage Properties of Polypropylene by Deashing Method for DC Polymer Film Capacitors

In this paper, a novel deashing method is proposed to prepare polypropylene (PP) materials with different ash contents (60–500 ppm). Effects of the ash on dielectric and energy storage characteristics of PP in polymer film capacitors are studied. The experimental results reveal that a low content of ash will help to improve the dielectric properties. Compared to the sample with 500 ppm of ash content, the PP film with 60 ppm ash possesses a higher breakdown strength (587.1 kV/mm), a lower DC conductivity (1.12 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−14</sup> S/m) and dielectric loss factor (3 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−4</sup> ). In addition, the energy storage property also shows a remarkabe improvement, the discharge energy density can be up to 3.22 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and the discharge efficiency remains at a high level. After the purification, the decline of the ash content in PP prevents the local electric field distortion and enhances the breakdown strength, which is beneficial for the improvement of the discharge energy density. Meanwhile, the reduction in the number of carriers ionized by the ash weakens the transport behavior and reduces the conductivity. It is concluded that the PP with high purity shows a great potential in polymer film capacitors.

Effect of Material Properties on the Foaming Behaviors of PP-Based Wood Polymer Composites Prepared with the Application of Spherical Cavity Mixer.

For the low weight and high strength, the microcellular extrusion foaming technology was applied in the preparation of polypropylene (PP)-based wood polymer composites, and the spherical cavity mixer was used to construct an experimental platform for the uniform dispersion of wood flour (WF). The effects of PP molecular configuration on the composite properties and cell morphology of samples were also investigated. The experimental results indicated that the application of a spherical cavity mixer with a cavity radius of 5 mm could effectively improve the mixing quality and avoid the agglomeration of WF. In addition, compared with the branched molecule, the linear molecule not only increased the melting temperature by about 10 °C, but also endowed composites with a higher complex viscosity at a shear rate lower than 100 s−1, which contributed to the cell morphology of more microporous samples.

Preparation of polypropylene with high melt strength by wet reaction blending of lignin

AbstractIn this paper, the melt strength of polypropylene is shown to be significantly improved by lignin‐cooperative construction of heterophase network structure and the evolution mechanism of lignin on the topology of polypropylene is investigated. Electron paramagnetic resonance (EPR) analysis shows that the free radicals generated by polypropylene irradiation can remain active for 2 weeks; rheological studies show that lignin promotes the formation of heterogeneous network structures in polypropylene, and its melt is characterized by long‐chain branching. Phase angle‐complex modulus, complex viscosity‐complex modulus, Han's, and Cole–Cole curves are used to analyze the liquid–solid transformation, and the results indicate that the enhanced interfacial action is due to the formation of the heterogeneous network structures. The mechanical properties show that the impact strength is increased by 1.8 times due to the synergistic effect of lignin and acrylamide. SEM shows the formation of a fibrous network structure around the lignin, which undergoes interfacial yielding, improving the interfacial interaction between the components.

Pharmaceutical wastewater treatment using polypropylene membranes incorporated with carboxylated and PEG‐grafted nanodiamond in membrane bioreactor (MBR)

AbstractThe aim of this work is to prepare polypropylene (PP) membrane by embedding carboxylated(‐COOH) and also polyethylene glycol(‐PEG) functionalized nanodiamond to improve membrane hydrophilicity and decline membrane fouling in pharmaceutical wastewater treatment. Porosity, contact angle, mechanical strength, field emission scanning electron microscopy (FESEM) and membrane pure water permeation analysis were performed for the characterization of the membranes. The membranes with 0.75 wt.% of nanoparticles introduced the highest water flux, porosity and mechanical strength. The performance of PP, PP/ND‐COOH (0.75 wt.%) and PP/ND‐PEG (0.75 wt.%) membranes was studied in a lab‐scale membrane bioreactor (MBR). COD removal was more than 91% in all cases. It was found that antifouling characteristics, membrane resistance (Rm) and specific cake layer resistance (α) of nanocomposite membranes were better than of neat PP membrane. PP/ND‐PEG (0.75 wt.%) membrane exposed highest hydrophilicity and maximum critical flux and anti‐fouling characteristics. The results indicated that embedding nanodiamond in PP membrane can reduce membrane fouling in MBR.

Compatibilized polypropylene nanocomposites containing expanded graphite and graphene nanoplatelets

AbstractWe present a non‐covalent compatibilization approach to prepare polypropylene (PP) composites containing expanded graphite (EG) and graphene nanoplatelets (GNPs) by melt compounding. This method involves PP matrix functionalization with pyridine (Py) moieties, which are capable of engaging in π‐π interactions with the surface of the EG and GNPs. The addition of 10 wt% of PP grafted with amino‐pyridine (PP‐g‐Py) to neat PP facilitated the break‐up of EG particles, by intercalating between their layers and facilitating their separation into smaller tactoids. GNPs were prepared starting from EG through a thermomechanical exfoliation method. Addition of GNPs to PP resulted in well‐dispersed platelets having aspect ratios as high as 40, whereas in the presence of the PP‐g‐Py compatibilizer the matrix contained sub‐micron scale platelets. The electrical percolation thresholds were in the vicinity of 6 and 10 vol% in the compatibilized PP‐EG and PP‐GNP composites, respectively, and the maximum value of the electrical conductivity achieved was 10−1 S/m for the compatibilized GNP composites. Addition of GNPs resulted in increases in the flexural moduli by as much as 95% compared to the unfilled PP, whereas the impact strength remained unaffected up to 10 wt% GNP content.

Improving the mechanical properties of polypropylene composites with coconut shell particles

Conventional inorganic fillers are widely used as fillers for polymer-based composites. Though, their processing difficulties and cost have demanded the quest for credible alternatives of organic origin like coconut shell fillers. Dried shells of coconut were burnt, ground, and sifted to sizes of 63, 150, 300, and 425 µm. The ground coconut shell particles (CSP) were used as a filler to prepare polypropylene (PP) composites at filler contents of 0% to 40% via injection melt blending process to produce PP composite sheets. The effect of the filler particle size on the mechanical properties was investigated. The decrease in the size of filler (CSP) was found to improve the yield strength, tensile strength, tensile modulus, flexural strength, flexural modulus, and hardness of PP by 8.5 MPa, 15.75 MPa, 1.72 GPa, 7.5 MPa, 100 MPa, and 10.5 HR for 63 µm at 40%, respectively. However, the elongation at break and modulus of resilience of the PP composites were seen to increase with increase in the filler size. Scanning electron microscope analysis showed that fillers with 63 µm particle size had the best distribution and interaction with the PP matrix resulting in enhanced properties.

Non-Isothermal Decomposition Kinetic of Polypropylene/Hydrotalcite Composite.

P₃O5-10 pillared Mg/Al hydrotalcite (HTs) as a functional fire-retarding filler was successfully prepared by impregnation-reconstruction, where the HTs was used to prepare polypropylene (PP) and HTs composite (PP/HTs). Thermal decomposition was crucial for correctly identifying the thermal behavior for the PP/HTs, and studied using thermogravimetry (TG) at different heating rates. Based on single TG curves and Málek method, as well as 41 mechanism functions, the thermal decompositions of the PP/HTs composite and PP in nitrogen atmosphere were studied under non-isothermal conditions. The mechanism functions of the thermal decomposition reactions for the PP/HTs composite and PP were separately "chemical reaction F₃" and "phase boundary reaction R₂," which were also in good agreement with corresponding experimental data. It was found that the addition of the HTs increased the apparent activation energy Ea of the PP/HTs comparing to the PP, which improved the thermal stability of the polypropylene. A difference in the set of kinetic and thermodynamic parameters was also observed between the PP/HTs and PP, particularly with respect to lower ΔS≠ value assigned to higher thermal stability of the PP/HTs composite.

Influence of graphene oxide on the static and dynamic mechanical behavior of compatibilized polypropylene nanocomposites

Abstract Graphene oxide (GO) is a carbon-based filler which possesses superior properties for the preparation of polypropylene (PP) nanocomposites. The homogeneous dispersion of nanofiller in a polymer matrix involves a compatibility between base and matrix. This research work analyzes the behavior of GO and its distribution in PP as well as the morphological, physical and mechanical properties of prepared nanocomposites. Since PP is non-polar and GO is polar, there may be a compatibility mismatch between filler and matrix, which may not lead to homogeneous distribution due to poor chemical interaction. Maleic-anhydride grafted polypropylene (MA-g-PP) was selected as a suitable compatibilizer in order to disperse filler into the matrix. X-ray diffraction (XRD) reveals an increase in intergallery spacing which confirms the formation of GO. Scanning electron microscopy (SEM) shows the improved distribution of GO sheets in the PP matrix for the compatibilized system. Tensile strength and modulus of elasticity are improved for the compatibilized PP nanocomposites when compared to the uncompatibilized and to the pure system. Moreover, an enhancement of storage modulus was evidenced for compatibilized nanocomposites. Polar-polar interaction between GO and compatibilizer leads to the homogeneous distribution of filler into the matrix which is clearly responsible for an improvement in the technical properties of polymer.

Characterization of polypropylene composites using yerba mate fibers as reinforcing filler

This study presents the preparation of polypropylene (PP) composites filled with yerba mate (YM) stick particles. Neat and post-consumer PP are used as the polymer matrices with 20, 30 and 40 wt% (w/w) YM fiber. Mechanical properties, including tensile, flexural and impact resistance, are determined, in addition to chemical and morphological analyses. The main findings show that the addition of filler from YM fiber increased the tensile and flexural strength of the neat and post-consumer PP composites up to a 30 wt% fiber content. The neat PP composites show better results than those with recycled PP, with PP20YM and PP30YM composites showing the best results. There is a gradual reduction in impact resistance with increasing YM content. Scanning electron microscopy shows a better adhesion between the matrix and filler in composites with 20 and 30 wt% YM, corroborating the tensile and flexural strength results.

Synthesis of polypropylene functionalized with a trace amount of reactive functional groups and its utilization in graft-type nanocomposites

In the preparation of polypropylene (PP)-based nanocomposites, grafting end-functionalized PP to nano-sized fillers is a promising strategy to alleviate the compatibility and interfacial problems at once, while poor synthetic efficiency for the end-functionalized PP and its grafting has been a major issue to be addressed. Here, we synthesized functionalized PP with one or less silicon methoxy groups per chain by means of direct copolymerization using a Ziegler-Natta catalyst, and utilized it as a reactive matrix in melt-mixing with spherical SiO2 nanoparticles. In addition to its synthetic advantage, the introduction of a trace amount of reactive functional groups delivered several profitable consequences to the nanocomposites that are typical for end-functionalized PP, such as improved dispersion, dramatically accelerated crystallization, and mechanical reinforcements.

Effect of hybrid wollastonite with different nucleation and morphology on the crystallization and mechanical properties of polypropylene

In order to prepare polypropylene (PP) composites with balanceable stiffness and toughness, hybrid wollastonite with different nucleation and morphology as fillers were added into PP matrix. Nucleation efficiency (NE), crystallization behavior and melting characteristics, as well as the mechanical properties of hybrid wollastonite‐filled PP composites were systematically investigated using differential scanning calorimetry, wide‐angle X‐ray diffraction, mechanical testing, and scanning electron microscopy, respectively. The results indicated that the NE of wollastonite with β‐nucleation is much higher than that of acicular wollastonite and ultrafine wollastonite with α‐nucleation, and eventually hybrid wollastonite‐filled PP composites mainly form β‐phase PP. Furthermore, there exists cooperative effect between the reinforcement of wollastonite of different morphology and the toughening of β‐phase, which can be effectively controlled through regulating the nucleating ability, morphology, and mass ration of hybrid wollastonite. POLYM. COMPOS., 40:E638–E646, 2019. © 2018 Society of Plastics Engineers

Bridging the segregated structure in conductive polypropylene composites: An effective strategy to balance the sensitivity and stability of strain sensing performances

Conductive polymer composites (CPCs) based strain sensors have been studied intensively recently. For a desirable strain sensor, a high sensitivity, a nice recoverability together with a good stability are required synchronously. In this study, the design of a segregated carbon black (CB) conductive network was demonstrated to be crucial for preparing polypropylene (PP)-based strain sensors with fine recoverability and stability, but a low sensitivity. The incorporation of carbon fibers (CFs) with large aspect ratio into the segregated CB/PP was utilized to build a bridged-segregated structure, leading to a synergistic conductive network. As a result, an improved sensitivity as well as a good stability was both achieved for the CF/CB/PP composite. The origin of these results was further explained on the basis of the tunneling model proposed by Simmons and the synergetic effect. This work provides a strategy for improving the performance of strain sensor with balanced sensitivity and stability by introducing a bridged-segregated structure.