Biaxially Oriented Polypropylene Film Research Articles

Correlation between lifetime model of BOPP film and rise rate under nanosecond pulse voltage

This paper aims to study the effect of rise rate (dV/dt) on the cumulative breakdown characteristics of biaxially oriented polypropylene (BOPP) film under nanosecond pulse voltage. The lifetime (N L) of BOPP film under nanosecond pulse voltage with different pulse voltage amplitude and dV/dt were carried out, respectively. It is found that the N L decreases with the increase of the pulse voltage amplitude, and the N L decreases with the increase of the dV/dt. Meanwhile, the quantitative mathematical relationship between N L and dV/dt, and pulse voltage amplitude are established, respectively, and it is concluded that both the rise rate and pulse voltage amplitude on the lifetime of BOPP film by the inverse power model. The results of the study are expected to provide the experimental basis and mechanistic explanation for the evaluation of film capacitor lifetime under extreme conditions.

γ-Ray Irradiation Significantly Enhances Capacitive Energy Storage Performance of Polymer Dielectric Films.

Polymer dielectric capacitors are fundamental in advanced electronics and power grids but suffer from low energy density, hindering miniaturization of compact electrical systems. It is shown that high-energy and strong penetrating γ-irradiation significantly enhances capacitive energy storage performance of polymer dielectrics. γ-irradiated biaxially oriented polypropylene (BOPP) films exhibit an extraordinarily high energy density of 10.4 J cm-3 at 968 MV m-1 with an efficiency of 97.3%. In particular, an energy density of 4.06 J cm-3 with an ultrahigh efficiency of 98% is reliably maintained through 20000 charge-discharge cycles under 600 MV m-1 . At 125°C, the γ-irradiated BOPP film still delivers a high discharged energy density of 5.88 J cm-3 with an efficiency of 90% at 770 MV m-1 . Substantial improvements are also achieved for γ-irradiated cycloolefin copolymers at a high temperature of 150°C, verifying the strategy generalizability. Experimental and theoretical analyses reveal that the excellent performance should be related to the γ-irradiation induced polar functional groups with high electron affinity in the molecular chain, which offer deep energy traps to impede charge transport. This work provides a simple and generally applicable strategy for developing high-performance polymer dielectrics.

UV-Induced Thiol-Ene "Click" Surface Grafting Polymerization on BOPP Substrate and Its Postmodifying for Hydrophilic and Antibacterial Applications.

This paper proposed a novel and versatile surface modification route by integrating UV light-mediated thiol-ene "click" surface grafting polymerization and postmodification via the reactions of the surface thiol groups. At first, poly(thiol ether) layers with tunable thiol group density, up to 8.2 × 102 ea/nm3 for cross-linked grafting layers, were grafted from biaxially oriented polypropylene (BOPP) film. Then, the surface -SH groups reacted with epoxy compounds to introduce quaternary ammonium salt. With the immobilized quaternary ammonium salt and coordinated Zn2+ ions, the modified film demonstrated 99.98% antibacterial rate against Staphylococcus aureusafter soaking in DI water for 21 days and in a highly alkaline environment (0.1 M NaOH aqueous solution) for 3 days, and the surface water contact angle decreased to 39°. At last, the polymethacrylate chains were also successfully grafted from the surface thiol groups of the cross-linked poly(thiol ether) under visible light irradiation. With 2-(dimethyldodecylammonium) ethyl methacrylate as the grafting monomer, the modified BOPP film had shown a 99.99% antibacterial rate against both Escherichia coliand S. aureus. Meanwhile, with 2-methacryloxyethyl phosphoryl choline as grafting monomer, the modified surface showed an excellent antibioadhesion of living S. aureus, and the surface water contact angle was as low as 48°.

Microfabrication of Thermoplastic Polypropylene Surface Structures via Thermal Imprinting for Controlling the Adhesion of Easy Peel Package.

Micropatterns were fabricated on polypropylene (PP) surfaces using the hot embossing technique with various temperatures ranging from 160 to 175 °C and applying force conditions from 100 to 300 N. To evaluate the replication quality, an effective filling ratio of 1 indicates that the volume of the formed pattern is similar to the mold cavity volume. From the results, the filling ratio increased with increasing the embossing temperature. For instance, under a constant force of 100 N, the filling ratio of polypropylene (PP) with small square arrays (pattern SS) increased from 0.08 to 0.41 when the embossing temperature was raised from 160 to 175 °C, respectively. With the increase of applied force, the filling ratio also increased. At an imprinting temperature of 175 °C and an applied force of 300 N, the highest effective filling ratio that was achieved was approximately 0.99. Furthermore, the effect of PP with different melt flow indexes (MFIs) on the filling ratio was investigated. For food packaging applications, a micropatterned PP sheet was heat-sealed with a biaxially oriented polypropylene (BOPP) film. The micropatterned PP sheet demonstrated easy-opening properties by varying sealing contact areas and micropattern geometries between the sheet and the BOPP film. All micropatterned PP sheets with an MFI of 25 g/10 min exhibited an easy peel property with adhesive failure characteristics at a heat-sealing temperature of 150 °C and a dwell time of 3 s. There was no residue on the PP substrate surface. The overall findings are beneficial in understanding the hot embossing technology for fabricating micropatterns on polymer surfaces, and it can be applied in an easy peel property for packaging applications.

Low-Temperature Assembling Strategy of a Nacre-Inspired Lamellar Configuration to Upcycling Biaxially Oriented Polypropylene Film Waste.

The efficient recycling and utilization of plastic waste have become a hot topic of global concern, but conventional mechanical recycling not only deteriorates the performance of recycled plastic but also loses the intrinsic structure and properties of the original product. Herein, an upcycling strategy of a biaxially oriented polypropylene (BOPP) film was proposed by duplicating the lamellar configuration established in nature nacre. Especially the suspension of PP wax was deposited on the surface of the BOPP film by spray-coating, followed by layer-by-layer assembling and hot-pressing at 160 °C above the melting temperature of PP wax but below the initial melting temperature of the BOPP film. In this case, PP wax not only functioned as a binder to enable strong interfacial adhesion between the BOPP films via interfacial diffusion but also acted as a soft phase to insert between the rigid BOPP films, constructing a soft-hard alternatively aligned configuration similar to brick-and-mortar architecture in nature nacre. As a result, the mechanical properties of the lamellar sample markedly outperformed those of the conventional mechanically recycling sample, evidenced by 113 and 1141% increases in tensile strength and impact strength, respectively. This simple and effective method provides a new strategy for efficient upcycling of oriented packaging films, which is important to realize the sustainable recycling of plastic waste.

Influence of frequency on the partial discharge characteristics of biaxially oriented polypropylene film under nanosecond pulse voltage

Partial discharge (PD) is one of the key factors leading to premature insulation failure of film capacitors used in pulse power devices. To study the effect of frequency on the PD characteristics of biaxially oriented polypropylene (BOPP) film, a sphere-plate electrode was used to simulate defects of the air gap between the film layers. PD experiments of the BOPP film were carried out under 1, 10, 100, 500 Hz, and 1 kHz with a rising edge of 65 ns and a pulse width of 300 ns. The results show that the repetitive partial discharge inception voltage (RPDIV), the number of discharges, the rising stage discharge (RSD) amplitude, and the falling stage discharge (FSD) time-lag, all show an increase and then decrease with increasing pulse frequencies and reach a maximum value at a pulse frequency of 100 Hz. Moreover, the FSD discharge amplitude and the RSD discharge time-lag increase with an increasing pulse frequency. From the perspective of initial electron generation, the quantitative mathematical relationship between PD characteristics (RPDIV, PD amplitude, PD number, and PD time-lag) and frequency was established based on the Fowler–Nordheim field emission effect for the first time, which can reflect the influence of frequency on the memory effect and the development process of PD. The results can provide an experimental basis and a mechanistic explanation for the evaluation of PD characteristics for film capacitors under nanosecond pulse voltage.

Evolution Characteristics of DC Breakdown for Biaxially Oriented Polypropylene Films

Biaxially oriented polypropylene (BOPP) films are the preferred storage dielectric for dry-type film capacitors due to excellent dielectric properties. However, the evolution characteristics of DC Breakdown of BOPP film in air remain unclear. This study focuses on the influence of curvature, contact area and material of electrode on the DC breakdown in BOPP films. The on-line/off-line measurements of surface potential and characterizations of trap distribution are achieved. And the simulations of surface charge, electric field and energy injection are accomplished. The breakdown path and degradation traces in BOPP films are also analyzed. The experimental results show that the effective insulation distance is the key to determine the actual performance of the film, affected by the trap distribution and density. This paper has a reference for the optimization of insulation structure for dry-type film capacitors in the field of high-voltage direct current (HVDC).

2D Nanosheet Spray Coating for Scalable Processing of High‐Energy‐Density Dielectric Polymer Films

AbstractDielectric film capacitors with high power density and rapid charge–discharge capability are widely used as key components in modern electronic and electrical systems, and polymers are primary dielectric for film capacitors due to their low cost, flexibility, and ease of processing. Here, a surface engineering approach is reported to improve the energy storage properties of polymer films by directly spray coating 2D nanosheets on the polymer film surface. The spraying of 2D calcium niobate nanosheets on the surface of biaxially oriented polypropylene (BOPP) films leads to remarkably increased breakdown strength and dielectric constant, resulting in a maximum 64% enhancement of energy density compared to the pristine BOPP films. Ultraviolet irradiation is further employed to improve the adhesion of nanosheets to the BOPP film surface, leading to an ultrahigh energy density of 11.6 J cm−3 with a high energy efficiency of 90%, which is the highest energy density ever achieved in polypropylene‐based films. This work provides a universal, cost‐effective, and scalable approach to improve the energy density of dielectric polymer films, which is of great significance for the application of high‐energy‐density polymer films in compact and efficient power systems.

Degradation Behavior and Mechanism of Metalized Film Capacitor Under Ultrahigh Field

Metalized film capacitor degradation under ultrahigh electric fields is crucial for the reliability of voltage source converter (VSC)-HVDC systems. In the present study, systematic investigations were performed that metalized film capacitors were aged under the dc electric field ranging from 300 to 400 kV/mm. Results showed that under moderate electric field, the capacitance reduction of sample capacitors presented two stages with different decay rates. With the increase of the electric field, the rapid degradation occurred immediately on the starting of the aging process, suggesting a voltage threshold determining the capacitors’ stability. In addition, the degradation mechanisms of both metalized films and biaxial oriented polypropylene (BOPP) base films were investigated by statistical analysis and structural experiments. Below the voltage threshold, more shallow traps were generated and the activation energy of molecular motions was reduced due to PP molecules scissions, resulting in the decrease of breakdown strength (BDS) of BOPP films. While above the voltage threshold, the accelerated failure could be attributed to two main causes: the fast breakdown of originally formed weak points and the dramatically increased self-healing area. The study can contribute to the design and evaluation of dc-link capacitors both experimentally and theoretically.

Partial Discharge Characteristics of Biaxially Oriented Polypropylene Film Under Nanosecond Pulse Voltage With High Rise Rate

Film capacitors are used as the key energy storage device for high-power pulse generators, and partial discharge (PD) is an important factor leading to insulation degradation and the failure of film capacitors. To accurately evaluate the effect of the rise rate on PD under nanosecond pulse voltage, experiments on the PD characteristics of biaxially oriented polypropylene (BOPP) films under high rise rate (18.3–140 V/ns) nanosecond pulse voltages were carried out. The PDs were mostly concentrated in the rising and falling phases of the nanosecond pulse. Moreover, the repetitive PD inception voltage (RPDIV) first increased and then remained unchanged as the rise time increased, and the PD amplitude and the number of discharges in the rising phase of the nanosecond pulse increased as the rise rate increased, while the discharge time lag decreased gradually. The PD amplitude, the number of discharges, and the discharge time lag in the falling phase of the nanosecond pulse all increased as the rise rate increased. In addition, when the rise rate was less than 50 V/ns, the PD statistical characteristics changed rapidly as the rise rate increased, and when the rise rate was greater than 50 V/ns, the PD statistical characteristics gradually changed more slowly as the rise rate increased.

Significantly Improved High‐Temperature Energy Storage Performance of BOPP Films by Coating Nanoscale Inorganic Layer

Biaxially oriented polypropylene (BOPP) is one of the most commonly used commercial capacitor films, but its upper operating temperature is below 105 °C due to the sharply increased electrical conduction loss at high temperature. In this study, growing an inorganic nanoscale coating layer onto the BOPP film's surface is proposed to suppress electrical conduction loss at high temperature, as well as increase its upper operating temperature. Four kinds of inorganic coating layers that have different energy band structure and dielectric property are grown onto the both surface of BOPP films, respectively. The effect of inorganic coating layer on the high‐temperature energy storage performance has been systematically investigated. The favorable coating layer materials and appropriate thickness enable the BOPP films to have a significant improvement in high‐temperature energy storage performance. Specifically, when the aluminum nitride (AlN) acts as a coating layer, the AlN‐BOPP‐AlN sandwich‐structured films possess a discharged energy density of 1.5 J cm−3 with an efficiency of 90% at 125 °C, accompanying an outstandingly cyclic property. Both the discharged energy density and operation temperature are significantly enhanced, indicating that this efficient and facile method provides an important reference to improve the high‐temperature energy storage performance of polymer‐based dielectric films.

The Effect of Annealing on the Structure and Electric Performance of Polypropylene Films

Biaxially oriented polypropylene (BOPP) and uniaxially oriented polypropylene (UOPP) films were annealed. The effect of annealing temperature (Ta) on dielectric strength was studied. The electric breakdown strength (Eb) of BOPP and UOPP films changes in a quite different trend with the annealing process. Eb of BOPP films decreases with the increase in Ta, whereas Eb of UOPP films increases first and then decreases with Ta. The structural changes during annealing were investigated. The crystallinity rises with Ta, while the orientation degree and Eb show a similar trend with Ta. Although the crystallinity and crystal structure can affect Eb of polypropylene films, the orientation of chain segments has a much larger correlation with Eb. Our results indicate that the deterioration of the metallized BOPP film capacitor may originate from the orientation degree decrease of chain segments after experiencing high temperature.

Significantly improved high-temperature energy storage performance of commercial BOPP films by utilizing ultraviolet grafting modification

Commercial biaxially oriented polypropylene (BOPP) film capacitors have been widely applied in the fields of electrical and electronic engineering. However, due to the sharp increase in electrical conduction loss as the temperature rises, the energy storage performance of BOPP films seriously degrades at elevated temperatures. In this study, the grafting modification method is facile and suitable for large-scale industrial manufacturing and has been proposed to increase the high-temperature energy storage performance of commercial BOPP films for the first time. Specifically, acrylic acid (AA) as a polar organic molecular is used to graft onto the surface of commercial BOPP films by using ultraviolet irradiation (abbreviated as BOPP-AA). The results demonstrate that the AA grafting modification not only slightly increases the dielectric constant, but also significantly reduces the leakage current density at high-temperature, greatly improving the high-temperature energy storage performance. The modified BOPP-AA films display a discharged energy density of 1.32 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> with an efficiency of >90% at 370 kV/mm and 125 °C, which is 474% higher than that of the pristine BOPP films. This work manifests that utilizing ultraviolet grafting modification is a very efficient way to improve the high-temperature energy storage performance of commercial BOPP films as well as provides a hitherto unexplored opportunity for large-scalable production applications.

Controllable synthesis and structural design of novel all-organic polymers toward high energy storage dielectrics.

As the core unit of energy storage equipment, high voltage pulse capacitor plays an indispensable role in the field of electric power system and electromagnetic energy related equipment. The mostly utilized polymer materials are metallized polymer thin films, which are represented by biaxially oriented polypropylene (BOPP) films, possessing the advantages including low cost, high breakdown strength, excellent processing ability, and self-healing performance. However, the low dielectric constant (ε r < 3) of traditional BOPP films makes it impossible to meet the demand for increased high energy density. Controlled/living radical polymerization (CRP) and related techniques have become a powerful approach to tailor the chemical and physical properties of materials and have given rise to great advances in tuning the properties of polymer dielectrics. Although organic-inorganic composite dielectrics have received much attention in previous studies, all-organic polymer dielectrics have been proven to be the most promising choice because of its light weight and easy large-scale continuous processing. In this short review, we begin with some basic theory of polymer dielectrics and some theoretical considerations for the rational design of dielectric polymers with high performance. In the guidance of these theoretical considerations, we review recent progress toward all-organic polymer dielectrics based on two major approaches, one is to control the polymer chain structure, containing microscopic main-chain and side-chain structures, by the method of CRP and the other is macroscopic structure design of all-organic polymer dielectric films. And various chemistry and compositions are discussed within each approach.

Layer-by-layer stacking, low-temperature welding strategy to effectively recycle biaxially-oriented polypropylene film waste

High-value recycling and reuse of plastic products is very important to solve global plastic pollution in the era of green development and low-carbon economy. Giving that the mainstream of processing plastic waste is still direct mechanical recycling, the unexpected degradation on mechanical properties betrays the intention to recycle plastic waste. Here, based on the temperature sensitivity of interfacial diffusion and orientation retention, we proposed an innovative protocol of recycling biaxially oriented polypropylene (BOPP) film waste in high value and efficient manner. Specially, a lamellar assembly of the biaxially-oriented film wastes was constructed layer by layer and then compressed into a sheet near the melting temperature. The temperature effects on interfacial fusion and orientation retention were investigated comprehensively. When the welding temperature approached the end melting temperature, the low-temperature laminated processing technology not only enabled strong interfacial adhesion, but also retained most of intrinsic orientation structure, conferring the as-prepared sheet with unprecedented combination of strength and toughness, as evidenced by a dramatic increase in ∼200% of mechanical strength and ∼650% of toughness to that of mechanically-recycled convention polypropylene (PP) products without orientation. The enhancement mechanism, in essence, stemmed from high strength endowed with orientation order and the laminar structure with strong ability to inhibit the crack propagation. Finally, supercritical CO 2 foaming technology was utilized to transform the high-performance fused PP sample into more valuable lightweight and rigid foam. This simple, scalable, economical and highly effective method without any interfacial additives is easily applied to the other biaxially-oriented films and sets a good example for the recycling application of biaxially-oriented film wastes to achieve the goal of green and low-carbon life. • The strategy of low-temperature welding with orientation retention method was firstly proposed. • Orientation structure endowed the high strength of welded samples accompanying the substantial ductility and toughness. • A lightweight foam with high-strength and excellent thermal insulation was prepared based on the welded samples. • This strategy is scalable and universal for biaxially-oriented films.

A unified model for conductivity, electric breakdown, energy storage, and discharge efficiency of linear polymer dielectrics

Polymer dielectric capacitors are widely used as high-power-density energy storage devices. However, their energy storage density is relatively low and they cannot meet the requirements for high temperature resistant and high energy density dielectric capacitors. In order to clarify the key factors affecting the energy storage performance and improve the energy storage density and energy efficiency synergistically, it is urgent to establish a unified model to simultaneously study the volt−ampere characteristics, space charge distribution, breakdown strength, discharged energy density, and charge–discharge efficiency of linear dielectrics. Based on the bipolar charge transport (BCT) model, we establish a unified model by a comprehensive consideration of charge injections from electrodes, carrier migration, trapping effects of exponentially distributed deep traps, and damage caused by energy gain. The BCT unified model is first used to simulate the breakdown strengths at different temperatures, the discharged energy densities, and charge–discharge efficiencies at different voltages and temperatures for biaxially oriented polypropylene (BOPP) film and SiO2-coated BOPP multilayer film. The simulation results are consistent with the experiments. They show that carrier injection and transport are key factors to determine the conductivity, electric breakdown, and energy storage performance for linear dielectrics. Coating a layer of SiO2 on BOPP film can increase the injection barrier and reduce the charge injection, which can reduce the conductivity and Joule heat, and can alleviate the electric field distortion, resulting in the improvement of the breakdown strength. Meanwhile, reducing the space charge accumulation during the charging process by suppressing the charge injection can elevate the voltage at the beginning of the discharging process, which can improve the discharged energy density and the charge–discharge efficiency of linear dielectric capacitors.

Improved Working Temperature and Capacitive Energy Density of Biaxially Oriented Polypropylene Films with Alumina Coating Layers

Improved Working Temperature and Capacitive Energy Density of Biaxially Oriented Polypropylene Films with Alumina Coating Layers

Influence of Surface Fluorination Treatment on Properties of Polypropylene Film

Biaxially-oriented polypropylene (BOPP) film is currently an indispensable material for pulse capacitor production. The breakdown field strength and leakage current are the key indicators of the metallized film, which affect the energy storage density and voltage holding performance of the capacitor. In this paper, BOPP film is subjected to surface treatment with different fluorination time and different fluoride concentration. The changes in material properties, such as the chemical bond, element content and crystallinity of the film after the fluorination treatment, are studied and analyzed. Then, the electrical properties, such as breakdown field strength, dielectric loss and leakage current of the film after the fluorination treatment, are studied. It is found that the fluorination treatment can increase the breakdown field strength of the dielectric film by 8.7%, increasing the energy storage density by 18%. It has little effect on the loss and leakage current of the film.

Study on ethanol resistance stability and adhesion properties of polyacrylate latex for PE or BOPP film inks

AbstractWaterborne inks based on the polyacrylate latex typically suffer from poor ethanol resistance and low adhesion on the PE or BOPP films. In this contribution, self‐crosslinkable polyacrylate latex binders with core‐shell structure and diacetone acrylamide (DAAM)/adipic acid dihydrazide (ADH) crosslinking agent for the application in the PE (polyethylene) or BOPP (Biaxially oriented polypropylene) film inks were synthesized. The effect of DAAM distribution in latex particles on ethanol resistance stability and the adhesion on the PE and BOPP thin films of the latexes and the corresponding inks was studied. Also, two functional monomers, isobornyl acrylate (IBOA) and acrylamide (AM) were introduced into the polyacrylate, respectively, to investigate their effect on the adhesion of the latexes and the inks on the PE and BOPP films. The results demonstrated that the more DAAM distributed in the core layer of the latex particles, the better the ethanol resistance, but the weaker the initial adhesion on the BOPP and PE thin films and the lower crosslinking degree of the latexes and the relative inks. However, the difference in cross‐linking degree and adhesion between the latex film with DAAM located within the shell part and that of DAAM located in the shell part keeps reducing with the prolongation of film‐forming time. Thus, when half of the DAAM is in the shell layer of latex particles, the latexes and the corresponding inks possess a balanced comprehensive property. The introduction of IBOA into polyacrylate is beneficial for improving the adhesion on both the BOPP and PE films of the inks due to the reduced surface tension of the latex. However, AM is only effective on the PE film, which may be due to the structural similarity of AM to erucate amide and oleate amide contained in the PE film, improving interaction between ink and the PE film.

Improved Energy Density and Charge Discharge Efficiency of Polypropylene Capacitor Film Based on Surface Grafting

In this paper, an advanced surface-grafting method is reported to improve the high-temperature performance of biaxially oriented polypropylene (BOPP) membranes. The leakage conductivity of the surface-grafted films decreases by 98% at 85 °C. The decline in the leakage loss contributes to the 99% charge-efficiency at 85 °C. The dielectric constant increases by 7%. The DC breakdown strength grows by 43% at 85 °C. The maximum energy storage density goes up from 1.45 to 2.77 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 85 °C. The surface-grafted BOPP film exhibits outstanding energy density and charge-discharge efficiency characteristics. This research provides a theoretical reference for improving the performance of capacitor film based on surface modification.