Empirical correction of kinetic model for polymer thermal reaction process based on first order reaction kinetics

Based on the theory of first-order reaction kinetics,a thermal reaction kinetic model in integral form has been derive.To make the model more applicable,the effects of time and the conversion degree on the reaction rate parameters were considered.Two types of undetermined functions were used to compensate for the intrinsic variation of the reaction rate,and two types of correction methods are provided.The model was explained and verified using published experimental data of different polymer thermal reaction systems,and its effectiveness and wide adaptability were confirmed.For the given kinetic model,only one parameter needs to be determined.The proposed empirical model is expected to be used in the numerical simulation of polymer thermal reaction process.

Impact of Die Materials on the Effect of New Polymer Processing Aids for Sharkskin Properties

Flows of polymeric liquids undergo instabilities whose origins are quite different from those of Newtonian flows, due to their elastic character and the complexity of the fluid/solid boundary condition. One of these instabilities is well known as “shark-skin” which damages the surface appearance and properties of polymer extrudate while processing in blowmolding or piping, while it can be suppressed by employing various methods including coating the die surface and/or adding Polymer Processing Aid’s (PPA) to the polymer. In this article, the effect of various die materials on the properties of Polyethylene glycol (PEG) as a new type of PPA for suppressing the sharkskin phenomenon has been studied.

Viscosity reduction of tapioca starch by incorporating with molasses hydrocolloids

As a low cost non-staple food resource,the high-viscosity paste and poor gel-forming ability of tapioca starch limit its industrial application.Herein,molasses hydrocolloids that is a by-product of the sugar refining process was applied as a blending modifier to reduce the viscosity of tapioca starch paste.The test results of paste and rheological properties show that molasses hydrocolloids exhibited a good physical viscosity-reducing effect on tapioca starch paste.The irregular network structure and high K^(+)/Ca^(2+)ion contents of molasses hydrocolloids exerted wrapping,adhesion,barrier,and hydration effects on starch,leading to the reduction of viscosity.The scanning electron microscope images and textural analysis demonstrated that this strategy also improve the structure of tapioca starch gel and enhanced its puncture strength by 75.46%.This work shows the great potential of molasses hydrocolloids as a lowcost and desirable material for the viscosity reduction of tapioca starch.

Chlorinated butyl rubber/two-step modified montmorillonite nanocomposites:Mechanical and damping properties

Montmorillonite(MMT) was modified by ultrasound and castor oil quaternary ammonium salt intercalation method to prepare a new type of organic montmorillonite(OMMT). The surface structure, particle morphology, interlayer distance, and thermal behavior of the samples obtained were characterized. The modified OMMT was then added to chlorinated butyl rubber(CIIR) by mechanical blending, and a composite material with excellent damping properties was obtained. The mechanical experiment results of CIIR nanocomposites showed that the addition of OMMT improved their tensile strength, hardness,and stress relaxation rate. Compared with pure CIIR, when the content of OMMT was 5 phr(part per hundred of rubber), the tensile strength of the nanocomposite was increased by 677% and the elongation at break was also increased by 105.4%. The enhancement of this performance was mainly due to the dispersion of the nanosheets in CIIR rubber and the chemical interaction between the organoclay and the polymer matrix, which was confirmed by morphology and spectral analysis. OMMT also endowed a positive effect on the damping properties of CIIR nanocomposites. After adding 5 phr of OMMT, the nanocomposite owned the best damping performance, and the damping factor, tanδmax, was 37.9% higher than that of pure CIIR. Therefore, the good damping and mechanical properties of these CIIR nanocomposites provided some novel and promising methods for preparing high-damping rubber in a wide temperature range.

Morphology Dynamical Mechanical and Flame Retardant Properties of Nylon 1212/Organic Montmorillonite Nanocomposites Prepared by Melt Compounding

Nylon 1212/organic montmorillonite(OMMT)nanocomposites were prepared using the melt compounding method.The morphology and dynamical mechanical properties of the nanocomposites were investigated using transmission electron microscope(TEM)and dynamic mechanical analysis(DMA).The storage modulus of nylon 1212/OMMT nanocomposites was increased with increasing OMMT.The flame retardant properties were characterized by cone calorimetry,scanning electron microscope(SEM)and X-ray photoelectron spectroscopy(XPS).The flame retardant properties were characterized using cone calorimetry,whereby nylon 1212/OMMT nanocomposites were improved compared with pure nylon 1212 because of the carbonaceous-silicate granular materials which were formed during combustion,thus proposing the flame retardant mechanism.

Simultaneously enhanced energy storage performance and luminance resistance in (K_(0.5)Na_(0.5))NbO_(3) -based ceramics via synergistic optimization strategy

The rapidly advancing energy storage performance of dielectric ceramics capacitors has garnered significant interest for applications in fast charge/discharge and high-power electronic techniques.Exploring the exceptional electrical properties in harsh environments can further promote their practical applications.Defect carriers can be excited under luminance irradiation,thereby leading to degradation of energy storage performance.Herein,a synergic optimization strategy is proposed to enhance energy storage properties and luminance resistance of(K_(0.5)Na_(0.5))NbO_(3)-base(KNN)ceramics.First,the introduction of Bi(Zn0.5Ti0.5)O_(3) solid solution and La3+ions disrupts the long-range polar orders and enhances super paraelectric relaxation characteristics.Additionally,doping La3+ions can increase the band gap and reduce oxygen vacancy concentration,resulting in excellent luminance resistance.Finally,the viscous polymer process is employed to suppress the grain growth and promote chemical homogeneity.As a result,ultrahigh recoverable energy storage density(Wrec)of 8.11 J/cm3 and high efficiency(η)of 80.98%are achieved under an electric field of 568 kV/cm.Moreover,the variations in Wrec andηare only 12.45%and 1.75%,respectively,under 500 W xenon lamp irradiation compared to the performance under a dark environment.These findings hold great potential in facilitating the practical application of dielectric ceramic capacitors in luminance irradiation environments.

BaTiO_(3)-based ceramics with high energy storage density

BaTiO_(3)ceramics are difficult to withstand high electric fields,so the energy storage density is relatively low,inhabiting their applications for miniaturized and lightweight power electronic devices.To address this issue,we added Sr_(0.7)Bi_(0.2)TiO_(3)(SBT)into BaTiO_(3)(BT)to destroy the long-range ferroelectric domains.Ca^(2+)was introduced into BT-SBT in the form of CaTiO_(3)(CT),which has the effect of inhibiting the movement of A-site defects to reduce dielectric loss and refining the grains to increase the breakdown field strength.In addition,we have increased the density and grain uniformity of ceramics by repeated rolling of the green samples through the viscous polymer processing(VPP),to further increase the breakdown electric field.The BT-SBT-CT ceramics exhibit the high recoverable energy storage density of 4.0 J·cm^(-3)under electric field of 480 kV·cm^(-1).Its recoverable energy storage density varies by less than 8%in the temperature range of 30-150℃,indicating good temperature stability of the energy storage performance.In this work,the energy storage performance of barium titanate-based ceramics was greatly improved by transforming ferroelectrics into relaxor ferroelectrics and VPP method,which can bring new inspiration for the research of energy storage ceramics.

Improved energy storage performance of bismuth sodium titanate-based lead-free relaxor ferroelectric ceramics via Bi-containing complex ions doping

Lead-free dielectric ceramics can be used to make quick charge-discharge capacitor devices due to their high power density.Their use in advanced electronic systems,however,has been hampered by their poor energy storage performance(ESP),which includes low energy storage efficiency and recoverable energy storage density(Wrec).In this work,we adopted a combinatorial optimization strategy to improve the ESP in(Bi_(0.5)Na_(0.5))TiO_(3)(BNT)-based relaxor ferroelectric ceramics.To begin,the Bi-containing complex ions Bi(Mg_(2/3)Nb_(1/3))O_(3)(BMN)were introduced into a BNT-based matrix in order to improve the diffuse phase transition,increase Bi-O bond coupling,avoid macro domain development,and limit polarization response hysteresis.Second,the viscous polymer process was employed to reduce sample thickness and porosity,resulting in an apparent increase in breakdown strength in(1-x)[0.7(Bi_(1/2)Na_(1/2))TiO_(3)]-0.3SrTiO_(3)-xBi(Mg_(2/3)Nb_(1/3))O_(3)(BS-xBMN)ceramics.Finally,in x=0.20 composition,an amazing Wrecof 5.62 J·cm^(-3)and an ultra-high efficiency of 91.4%were simultaneously achieved at a relatively low field of 330 kV·cm^(-1),together with remarkable temperature stability in the temperature range of 30-140℃(3.5 J·cm^(-3)±5%variation).This research presents a new lead-free dielectric material with superior ESP for use in pulsed power capacitors.

Achieving high dielectric energy-storage properties through a phase coexistence design and viscous polymer process in BNT-based ceramics

In the last few decades,dielectric capacitors have gotten a lot of attention because they can store more power and charge and discharge very quickly.But it has a low energy-storage density(Wrec),efficiency(h),and temperature stability.By adding Pb(Mg1/3Nb2/3)O3(PMN)and(Bi0$1Sr0.85)TiO3(BST)to a nonstoichiometric(Bi0$51Na0.5)TiO3(BNT)matrix,the goal is to change the phase transition properties and make the material more relaxor ferroelectric(RFE)by lowering the remnant polarization Pr and keeping the maximum polarization Pmax.A viscous polymer process(VPP)is used to improve the electric breakdown strength,which is also a key part of being able to store energy.By working together,ceramics with the formula 0.79[0.85BNT-0.15PMN]-0.21BST(BP-0.21BST)are made.The phase structure has been changed from a rhombohedral phase to a rhombohedral-tetragonal coexisted phase.This is beneficial for RFE properties and gives a Wrec of 6.45 J/cm^(3) and a h of 90%at 400 kV/cm.Also,the energy-storage property is very temperature stable between 30 and 150
C.These results show that process optimization and composition design can be used to improve the energy storage properties,and that the dielectric ceramic materials made can be used in high-powder pulse dielectric capacitors.

Current advances and future perspectives of additive manufacturing for functional polymeric materials and devices

Three-dimensional(3D)printing has received extensive attention due to its unique multidimensional functionality and customizability and has been recognized as one of the most revolutionary manufacturing technologies.Functional 3D printed products represent an important orientation for next-generationmanufacturing and attract a great spotlight for the application in sensors,actuators,robots,electronics,and medical devices.However,the lack of functions of printing polymeric materials dramatically limits the development of functional 3D printing.Different from traditional processing,the physical properties,such as geometry and rheological behavior,of the polymericmaterialsmust match the printing process,making the selection of printable materials limited.More importantly,challenges in large-scale production of such materials further stifle the development of functional 3D printing industry.In this review,we aim to outline recent advances in polymeric materials and methodologies for the functional 3D printing technology.The reports are classified based on functionalities,including electronic conductive,thermally conductive,electromagnetic interference shielding,energy storage,and energy harvesting materials.This study attempts to provide a comprehensive overview of the challenges and opportunities for 3D printing functional polymeric materials/devices,also seeks to enlighten the orientation of future research in this field.