Commercial Polypropylene Research Articles

Multivariable Rheological Models for Commercial Polypropylene with High Molar Masses

AbstractThis work investigates the fitting performance of conventional rheological models and the development of multivariable rheological models to reproduce experimental rheological data of different industrial grades of linear isotactic polypropylene (iPP) having high mass average molar masses, Mm (164–404 kg mol−1), at three temperature values (180–220 °C) over a wide range of shear rates (10−1–104 s−1). A shear thinning behavior is found in all investigated conditions. However, a low shear rate primary Newtonian plateau for a short shear rate range is only identified for the smallest Mm among those investigated, and for higher Mm such primary plateaus are even found at shorter shear rate range. Among the investigated models, only Cross and Carreau–Yasuda models are effective to reproduce the data for a specific PP grade. Two modified models are proposed that incorporate three variables. In the modified Cross Model, it has been shown that the characteristic time (λ) between the Newtonian plateau at the low shear rates and the shear‐rate range with shear‐thinning behavior depends exponentially on the Mm, and it does not depend on the temperature. Both proposed models fit very well with the experimental data with shear thinning behavior for a wide range of Mm.

Electrospun Cellulose Nanofiber Membranes as Multifunctional Separators for High Energy and Stable Lithium-Sulfur Batteries

Although Li–S batteries (LSB) are one of the most promising electrochemical energy storage technologies, their practical applications are limited by their rapid capacity decay and uncontrolled lithium dendrite formation. In addition to the well-known role of a separator in lithium-ion batteries, LSB separators must perform additional functions. Using a facile electrospinning method, we developed an eco-friendly separator prepared from natural cellulose with an interconnected fibrous and porous structure rich in polar oxygen-containing functional groups. These polar functional groups enhance electrolyte wettability, polysulfide adsorption, and lithiophilicity, thus boosting LSB performance. A cellulose separator with a thickness (22 μm) comparable to that of a commercial polypropylene (Celgard) separator delivers an initial discharge capacity of 1458 mAh·g−1 at 0.1C with a high sulfur utilization of 87%, including a high reversible discharge capacity of 1091 mAh·g−1 for 100 cycles, exhibiting a 1.8-times greater capacity retention than those of Celgard-containing LSBs. In addition, an excellent rate capability of 908 mAh·g−1 can be achieved at a high rate of 1C. These intriguing characteristics indicate that these separators could replace conventional synthetic polymer-based separators for commercial LSBs.

Additive Manufacturing of Carbon Using Commodity Polypropylene.

Carbon materials are essential to the development of modern society with indispensable use in various applications, such as energy storage and high-performance composites. Despite great progress, on-demand carbon manufacturing with control over 3Dmacroscopic configuration is still an intractable challenge, hindering their direct use in many areas requiring structured materials and products. This work introduces a simple and scalable method to generate complex, large-scale carbon structures using easily accessible materials and technologies. 3D-printed, commercial polypropylene (PP) parts can be thermally stabilized through cracking-facilitated diffusion and crosslinking. The newly elucidated mechanism from this work allows thick PP parts to yield carbonaceous products with complex structures through a subsequent pyrolysis step. The approach for enabling PP-to-carbon conversion has consistent product yield and controlled dimensional shrinkage. Under optimized processing conditions, these PP-derived carbons exhibit robust mechanical properties and excellent joule heating performance, demonstrated by their versatile use as heating elements. Furthermore, this process can be extended to recycled PP, enabling the conversion of waste plastic materials to value-added products. This work provides an innovative approach to create structured carbon materials with direct access to complex geometry, which can be transformative to, and broadly benefit, many important technological applications.

Ion Transport Regulated Lithium Metal Batteries Achieved by Electrospun ZIF/PAN Composite Separator with Suitable Electrolyte Wettability

Lithium metal battery (LMB) is a topic receiving growing attention due to the high theoretical capacity, while its practical application is seriously hindered by the lithium dendrites issue. As the physical barrier between two electrodes, the separator can achieve dendrite suppression by means of providing higher mechanical strength, regulating ion transport and facilitating homogeneous lithium deposition. Based on this, a composite separator is fabricated with zeolitic imidazolate framework (ZIF-8) and polyacrylonitrile (PAN) via electrospinning techniques, and its physical properties and electrochemical performances, together with its dendrite suppression mechanism, are investigated. The ZIF8-PAN separator possesses a unique 3D interconnected porous skeleton, displaying higher electrolyte uptake, preferable electrolyte wettability, and lower thermal shrinkage compared with the commercial polypropylene separator. In addition, a battery assembled with the ZIF8-PAN separator can effectively regulate ion transport and suppress dendrites growth, which exhibits an enhanced ionic conductivity (1.176 mS/cm), an increased lithium-ion transference number (0.306), a wider electrochemical stability window (5.04 V), and superior cycling stability (over 600 h with voltage hysteresis of 30 mV). This work offers a promising strategy to realize safe separator for dendrite suppression in LMB.

The Inducement and "Rejuvenation" of Li Dendrites by Space Confinement and Positive Fe/Co-Sites.

The high reactivity of Li metal and the inhomogeneous Li deposition leads to the formation of Li dendrites and "dead" Li, which impedes the performance of Li metal batteries (LMBs) with high energy density. The regulating and guiding the Li dendrite nucleation is a desirable tactic to realize concentrated distribution of Li dendrites instead of completely inhibiting dendrite formation. Here, a Fe-Co-based Prussian blue analog with hollow and open framework (H-PBA) is employed to modify the commercial polypropylene separator (PP@H-PBA). This functional PP@H-PBA can guide the lithium dendrite growth to form uniform lithium deposition and activate the inactive Li. In details, the H-PBA with macroporous structure and open framework can induce the growth of lithium dendrites via space confinement, while the positive Fe/Co-sites lowered by polar cyanide (-CN) of PBA can reactivate the inactive Li. Thus, the Li|PP@H-PBA|Li symmetric cells exhibit long-term stability at 1mA cm-2 for 1 mAh cm-2 over 500h. And the Li-S batteries with PP@H-PBA deliver favorable cycling performance at 500mA g-1 for 200 cycles.

Layer-by-layer printable nano-scale polypropylene for precise control of nanocomposite capacitor dielectric morphologies in metallised film capacitors

• A novel technique to fabricate capacitors with nano-scale layer-by-layer printing • Polypropylene gel inks were used to successively print layers as thin as 200 nm • Layer thickness is easily controllable, and the capacitance is highly predictable • Incorporation of BaTiO 3 nanoparticles was demonstrated in a structured dielectric • Presents pathway to the commercial printing of structured nanocomposite capacitors Nanocomposite dielectrics are an increasingly important area of innovation in capacitor research as an avenue to improve capacitive energy density, electrical breakdown strength, and temperature stability of devices. In such devices, morphology control is critical in order to optimise electrical field distribution in the device and to prevent the clustering of nanoparticles lowering breakdown voltages. However, this is difficult to achieve with large-scale fabrication techniques, such as melt extrusion and stretching, as melt processing can induce clustering and offers few possibilities for fine structure control of length scales below 1 µm. Layer-by-layer fabrication offers a potential bottom-up alternative whereby dielectrics are printed by successive depositions of ultra-thin layers of a room-temperature-stable polymer ink. This would allow fine thickness and morphology control and could easily be adapted to industrial-scale printing techniques, like roll-to-roll slot-die coating. This study explores this technique by developing two polypropylene-based inks in industry-friendly solvents that are then used to fabricate capacitor devices. A gel ink was able to be used to deposit ultrathin (sub-200 nm) layers of mostly amorphous polypropylene with high reproducibility. Capacitors based on these polypropylene layers perform commensurate with commercial devices, exhibiting excellent self-clearing and breakdown performance. Successive depositions of the ink were also demonstrated, allowing the fabrication of devices with finely tuned thicknesses and capacitances, as well as nanocomposite capacitors. This demonstrates the viability of layer-by-layer dielectric printing at large scale and paves the way for commercial ultra-thin conformable polypropylene capacitors, multi-component sandwich nanocomposite capacitors, and multilayer polypropylene capacitors, as well as brand new possibilities in dielectrics research.

Poly(Ionic Liquid) as an Anion Exchange Membrane for a 3.3 V Copper–Lithium Battery

Metal–metal battery bears great potential for next‐generation large‐scale energy storage system because of its simple manufacture process and low production cost. However, the cross‐over of metal cations from the cathode to the anode causes a loss in capacity and influences battery stability. Herein, a coating of poly (ionic liquid) (PIL) with poly(diallyldimethylammonium bis(trifluoromethanesulfonyl)imide) (PDADMA+TFSI−) on a commercial polypropylene (PP) separator serves as an anion exchange membrane for a 3.3 V copper–lithium battery. The PIL has a positively charged polymer backbone that can block the migration of copper ions, thus improving Coulombic efficiency, long‐term cycling stability and inhibiting self‐discharge of the battery. It can also facilitate the conduction of anions through the membrane and reduce polarization, especially for fast charging/discharging. Bruce‐Vincent method gives the transport number in the electrolyte to be 0.25 and 0.04 for PP separator without and with PIL coating, respectively. This suggests that the PIL layer reduces the contribution of the internal current due to cation transport. The use of PIL as a coating layer for commercial PP separator is a cost‐effective way to improve overall electrochemical performance of copper–lithium batteries. Compared to PP and polyacrylic acid(PAA)/PP separators, the PIL/PP membrane raises the Coulombic efficiency to 99% and decreases the average discharge voltage drop to about 0.09 V when the current density is increased from 0.1 to 1 mA cm−2.

Pervaporation of the low ethanol content extracting stream generated from the dealcoholization of red wine by membrane osmotic distillation

This paper presents as main contribution the combination of membrane osmotic distillation (OD) to dealcoholize red wine with hydrophobic-hydrophilic pervaporation (PV) carried out to add value to the wastewater (extracting water) produced in OD, recycling water and generating bioethanol. Membrane OD with a commercial polypropylene hollow fiber module was applied to partially dealcoholize red wine from 14.0 to 11.0 v/v% ethanol. The OD extracting water, containing only ca. 5.3 wt% ethanol, was treated by sequential PV with both hydrophobic (PDMS or zeolite silicalite-1) and hydrophilic (zeolites mordenite or faujasite) membranes. This hydrophobic-hydrophilic PV produced two main products: bioethanol (recovering 88% of the ethanol removed from the wine) and a 99.4 wt% water-rich product. This water-rich product, with a very low ethanol content, was used as extracting water in the OD, giving rise to an analogous partially dealcoholized wine, in terms of aroma contents (as determined by gas chromatography for 25 compounds), to that achieved when using fresh water.

A high‐safety, flame‐retardant cellulose‐based separator with encapsulation structure for lithium‐ion battery

AbstractThe safety issues of lithium‐ion batteries have received attention because flammable organic electrolytes are used. Also, the commercial polyolefin separator will undergo severe thermal shrinkage when the internal temperature of the battery increases to 130–160°C, which increases the risk. Therefore, the development of a high thermal stability and high‐safety separator is an effective strategy to improve battery safety. Herein, we design a green, cellulose‐based separator (Cel@DBDPE) with a unique encapsulation structure for lithium‐ion batteries, in which functional flame retardants (DBDPE) are wrapped in microscrolls formed by the self‐rolling of 2D cellulose nanosheets upon freeze‐drying. This structure can firmly anchor DBDPE particles in the separator to prevent them from undergoing exfoliation and does not affect the properties of the separator, such as the thickness and the pore structure. Compared with commercial polypropylene, Cel@DBDPE has excellent thermal stability and flame retardancy. The former makes it less prone to thermal shrinkage and the latter can effectively prevent the combustion of the electrolyte, showing an efficient self‐extinguishing ability. Moreover, the Cel@DBDPE is only 15 μm in size and has competitive properties comparable to polypropylene. Thus, there is no sacrifice in the electrochemical performance of battery when the Cel@DBDPE is used as separator. This study provides a new structural design for the construction of a high‐safety separator.

High Efficiency Antibacterial, Moisture Permeable, and Low Temperature Comfortable Janus Nanofiber Membranes for High Performance Air Filters and Respiration Monitoring Sensors

AbstractIn this work, high efficiency and multifunctional poly(vinyl alcohol‐co‐ethylene) nanofiber, Ag particle, and polypropylene (PP) meltblown nonwoven substrate composite (NF@Ag) air filters by a simple spray coating method and subsequent UV irradiation treatment are demonstrated. The water vapor transmission rate of the NF@Ag‐4 air filter is 4753.36 ± 316.75 g/(m2 d), which is higher than that of commercial PP nonwoven (4240.71 ± 354.36 g/(m2 d)). It is can be explained that the NF@Ag‐4 air filter is a Janus structure with asymmetric wettability, which enhances moisture permeability, thereby improving comfort while wearing. The NF@Ag‐2 air filter exhibits high filtration efficiency (95.80 ± 0.89%) and relatively low pressure drop (122.00 ± 1.73 Pa) without relying on the electrostatic adsorption effect. The resulting NF@Ag air filters display excellent antibacterial properties against Escherichia coli and Staphylococcus aureus, photothermal disinfection, and thermal insulation performance. Furthermore, the as‐prepared NF@Ag air filters can be simply patterned and designed as respiration monitoring sensors to precisely detect the respiratory activity and health of the human being. Therefore, it is believed that these multifunctional air filters will have good potential for applications in the removal of particular matters and breathable wearable electronic devices.

A Dual−Functional Cationic Covalent Organic Frameworks Modified Separator for High Energy Lithium Metal Batteries

AbstractSeparator modification is an efficient strategy to handle with the challenges of lithium metal batteries but its success is primarily subject to the modification of the materials. Herein, a cationic covalent organic framework (COF) composed of positively charged organic units and weakly bonded fluoride ions (F−) is introduced to modify the commercial polypropylene separator (COF−F@PP). It is found that the organic unit has abundant nanopores to homogenize the lithium ions (Li+) flux and can interact with electrolyte solvent molecules to form a desolvation structure of Li+. Meanwhile, the F− within the nanopores is proved to assist in building a robust LiF−riched solid electrolyte interphase to avoid the side reactions between lithium anode and electrolyte. Hence, the COF−F@PP delivers feasible practicality for the outstanding cycling stability, high Coulombic efficiency, and superior rate capability of Li//LFP coin cell at 5 C, low N/P ratio (2.19) full cell, and pouch cell at 1 C.

Toward Safe and High-Performance Lithium–Sulfur Batteries via Polyimide Nanosheets-Modified Separator

Lithium–sulfur batteries (LSBs) have broad application prospects in high density energy storage. Nevertheless, LSBs present serious safety concerns and rapid capacity decay due to the flammability and contractility of commercial separators at high temperatures and lithium polysulfide (LiPSs) dissolution. In view of this, a multifunctional modified separator is developed by combining a commercial polypropylene (PP) separator with a polyimide (PI)-Super P functional coating and a rigid nonflammable PI matrix. This PI/PP/PI-Super P separator provides multiple advantages: (i) strong physical blocking and chemical trapping/conversion ability for LiPSs, (ii) high flame-retardancy and dimensional stability, and (iii) superior electrolyte wettability and high efficiency lithium dendritic growth inhibition. As a result, the LSBs assembled with PI/PP/PI-Super P separators and pure sulfur cathodes exhibit an ultrahigh discharge specific capacity of 1611.8 mAh/g and excellent cycling performance (the average capacity attenuation within 100 cycles at 1 C is 0.469%) at 80 °C, which exceed the advanced results reported previously. More importantly, even when sulfur and organic electrolyte are adsorbed on PI/PP/PI-Super P, the modified separator still shows good flame retardancy. Additionally, this modified separator is also suitable for LSBs with high sulfur loading. This work offers an innovative design concept for safe and high-performance LSBs.

Complex Effects of Hemp Fibers and Impact Modifiers in Multiphase Polypropylene Systems

Natural fibers-reinforced polymer composites have progressed rapidly due to their undeniable advantages. Most of the commercial polypropylene (PP)-based materials are characterized by either high impact toughness or high stiffness, while the manufacture of PP composites with both good toughness and stiffness is challenging at present. In this work, poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) and poly(styrene-b-butadiene-b-styrene) (SBS) copolymers were used in different amounts as modifiers in PP/hemp fibers (HF) composites, with the aim to use them for electrical vehicle parts. The interface in these multiphase systems was controlled by the addition of maleated polypropylene (MAPP). SEBS and SBS showed different effects on the elongation at break of the blends and the corresponding composites due to the HF that stiffened the multiphase systems. Similarly, a different action of MAPP was observed in the composites containing SEBS or SBS: higher Young's and storage moduli were obtained for the composite containing SBS, while greater elongation at break and impact strength values were recorded for the SEBS-containing system. In addition, a remarkable dispersion in the MAPP-containing composite and two times smaller average particle size were revealed by the SEM analysis for the SEBS particles compared to the SBS ones. The higher affinity of SEBS for PP compared to that for SBS and the different morphological characteristics of the systems containing SEBS and SBS may explain the different effects of these impact modifiers on the mechanical properties of the composites. The composites developed in this work were designed as substitutes for the fully synthetic polymeric materials or metal components used in the manufacturing of automotive parts.

Crystallization-templated high-performance PVDF separator used in lithium-ion batteries

In this work, high-performance PVDF separators have been successfully fabricated for lithium-ion batteries (LIBs) based on crystallization template in PVDF/PBSU blends. The crystallization of PVDF produces co-continuous structures of crystalline phase and amorphous phase. On one hand, the continuous state of PBSU enables its removal via selective solvent extraction, yielding 3D interpenetrated nanochannels which have been confirmed with the help of X-ray imaging technology. On the other hand, the continuous PVDF crystal framework contributes to superior mechanical performance and heat resistance of resultant separator, playing crucial roles in the inhibition of Li dendrite growth and improvement of LIBs safety. The optimal specimen of PVDF-30 (from PVDF/PBSU 30/70) exhibits higher discharge capacity (135.5 mA h g−1), higher coulombic efficiency (∼99.9% after 200 cycles) and enhanced cycle stability relative to the reference (commercial polypropylene separator). Such a significant improvement can be attributed to the combination of excellent connectivity of diffusion channels, outstanding mechanical performance and higher electrolyte uptake resulting from stronger polarity of PVDF. Our results provide a novel strategy for fabricating PVDF separators with superior performances used in lithium-ion batteries.

EFFECTIVE POROSITY OF 3D PRINTED SURGICAL MESHES

Abstract Introduction According to previous studies, pore size and geometry are crucial factors to assure good clinical results for surgical meshes [refs]. Although commercial surgical meshes are commonly knitted, 3D printing has recently been used to provide additional properties to them [refs]. In general, the mechanical properties of 3D printed meshes are worse, but geometrical control is better than in knitted ones. In this study, a comparison of effective porosity between knitted and 3D printed surgical meshes was performed. Methods Pore size and geometry were characterized through optical brightfield microscopy (Nikon E100) and quantified using ImageJ v.1.53e. Several geometries of 3D printed meshes with polypropylene (Prusa i3 MK3 and Smartfil filament) and commercial polypropylene Assumesh meshes (Assut Europe) were evaluated. The 3D printed geometries were triangular and honeycomb while the commercial meshes were knitted. Results 32.38, 18.65 and 17.26% of the total area of the commercial, triangular and honeycomb meshes were porous, respectively. Although effective porosity was homogeneous on commercial meshes (2.71±0.07 mm2), pore size was smaller in honeycomb (0.088±0.071 mm2) and bigger in triangular (0.201±0.063 mm2) than in commercial meshes (0.105±0.030 mm2). Conclusions Some imperfections are generated during the extrusion of filaments that contributes to non-uniform pores in 3D printed meshes. Hence, a post-processing of meshes will be recommended to take advantage of the higher precision of 3D printing.

An evaluation of the suitability of a new polypropylene powder for powder bed fusion additive manufacturing

The intrinsic and extrinsic properties of a commercial polypropylene (PP) powder (BASF Ultrasint PP 1400) for use in powder bed fusion-based additive manufacturing were characterised and preliminary test parts were printed on an EOS P380 machine. The test specimens demonstrated relatively good dimensional accuracy (<3.6% part deviation), higher than normal elongation at break (127%), and moderate ultimate tensile strength (UTS) of 21.4 MPa.

Toward High-Performance Mg-S Batteries via a Copper Phosphide Modified Separator.

Magnesium-sulfur (Mg-S) batteries are emerging as a promising alternative to lithium-ion batteries, due to their high energy density and low cost. Unfortunately, current Mg-S batteries typically suffer from the shuttle effect that originates from the dissolution of magnesium polysulfide intermediates, leading to several issues such as rapid capacity fading, large overcharge, severe self-discharge, and potential safety concern. To address these issues, here we harness a copper phosphide (Cu3P) modified separator to realize the adsorption of magnesium polysulfides and catalyzation of the conversion reaction of S and Mg2+ toward stable cycling of Mg-S cells. The bifunctional layer with Cu3P confined in a carbon matrix is coated on a commercial polypropylene membrane to form a porous membrane with high electrolyte wettability and good thermal stability. Density functional theory (DFT) calculations, polysulfide permeability tests, and post-mortem analysis reveal that the catalytic layer can adsorb polysulfides, effectively restraining the shuttle effect and facilitating the reversibility of the Mg-S cells. As a result, the Mg-S cells can achieve a high specific capacity, fast rates (449 mAh g-1 at 0.1 C and 249 mAh g-1 at 1.0 C), and a long cycle life (up to 500 cycles at 0.5 C) and operate even at elevated temperatures.

A bacterial cellulose-based separator with tunable pore size for lithium-ion batteries

Bacterial cellulose (BC) lithium-ion batteries separators possess outstanding thermal dimensional stability and electrolyte wettability, but theirs nano diameter and high aspect ratio lead to poor porosity and pore size uniformity of dense BC separators, limiting the Li+ transmission in the separators. In this paper, chitosan (CS) with different molecular weight was grafted onto BC (named OBCS), and a high-performance OBCS separator with excellent pore structure and tunable pore size was prepared by simple suction filtration. The spacing and dispersion uniformity of OBCS were improved by the CS grafted on BC surface, thus improving the pore structure and porosity of OBCS separators. The results showed that the obtained OBCS separators not only have excellent physicochemical properties, but also exhibit higher electrochemical performances than the commercial polypropylene (PP) separator. This work provides a new feasible strategy for improving the pore structure and porosity of nanocellulose separators.

Manufacturing N,O-carboxymethyl chitosan-reduced graphene oxide under freeze-dying for performance improvement of Li-S battery

Lithium-sulfur (Li-S) batteries can provide far higher energy density than currently commercialized lithium ion batteries, but challenges remain before it they are used in practice. One of the challenges is the shuttle effect that originates from soluble intermediates, like lithium polysulfides. To address this issue, we report a novel laminar composite, N,O-carboxymethyl chitosan-reduced graphene oxide (CC-rGO), which is manufactured via the self-assembly of CC onto GO and subsequent reduction of GO under an extreme condition of 1 Pa and −50 °C. The synthesized laminar CC-rGO composite is mixed with acetylene black (AB) and coated on a commercial polypropylene (PP) membrane, resulting in a separator (CC-rGO/AB/PP) that can not only completely suppress the polysulfides penetration, but also can accelerate the lithium ion transportation, providing a Li-S battery with excellent cyclic stability and rate capability. As confirmed by theoretic simulations, this unique feature of CC-rGO is attributed to its strong repulsive interaction to polysulfide anions and its benefit for fast lithium ion transportation through the paths paved by the heteroatoms in CC.

Ultrafast and on-demand oil/water separation with vertically aligned cellulosic smart sponge

Slow oil sorption speed of commercial non-woven polypropylene (PP) sorbent remains a major challenge for efficient clean-up of oil spillage. Adsorption-based polymeric sponge oil removing offers an appealing way to solve this challenge by increasing surface area. However, the tortuous oil sorption path and plastic waste after oil uptake are two long-standing bottlenecks for realizing efficient oil spill removal. Here, we report a vertically aligned-biomass fiber junctioned sorbents (a-BFJS), by confining delignified biomass with carbon nanotube (CNT), polyvinyl alcohol (PVA), and methyltrimethoxysilane (MTMS). The sorbent shows an excellent performance towards xylene sorption capacity with uptake about 50 g g−1 within 10 s. This is due to the wide and short pathway of their aligned channels, which improves the capillary effect and fast oil transport in the oriented channels. Moreover, the sponge exhibits fast oil sorption-desorption kinetics enabled by simple mechanical squeezing. We further engineered a scalable rapid continuous oil skimming with simple peristaltic pump. The oil recovering using a-BFJS realized high oil selectivity from xylene/water emulsion. Our demonstration of the high-performance aligned channel sorbent and scalable oil removing sponge offers an eco-friendly and promising strategy for efficiently removing oil from oil spills from water.