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 i...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.展开更多
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 temp...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 150C.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.展开更多
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 ra...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.展开更多
A series of polyurethane (PU)/vinyl ester resin (VER) simultaneous IPNs (interpenetrating polymer networks) with different component ratios and comonomers types introduced to VER were synthesized and the polymer...A series of polyurethane (PU)/vinyl ester resin (VER) simultaneous IPNs (interpenetrating polymer networks) with different component ratios and comonomers types introduced to VER were synthesized and the polymerization processes were traced by Fourier transform infrared spectroscopy (FTIR) to study the kinetics of IPNs and hydrogen bonding action within multi-component. Furthermore, the relationship of polymerization process with morphology was investigated in detail for the first time by the morphological information given by chemical action between two networks besides physical entanglement, atomic force microscope (AFM) observation and dynamic mechanical analysis (DMA). The results indicated that the degree of hydrogen bonding (Xb,UT,%), calculated from functional group conversional rate and fine structures gained from FT-IR spectra of two networks, were affected by PU/VER weight ratios and comonomer types of VER. The relationship of formation kinetics and morphology showed that the change of Xb,UT (%) values exhibited excellent consistency with that of phase sizes observed by AFM and detected by DMA.展开更多
The process of emulsifier-free copolymerization of the Styrene-Butyl Acrylate-K_sS_sO_s-water in the presence of Barium Sulfate(BS)powder was investigated under varied conditions within the range of BS powder quantity...The process of emulsifier-free copolymerization of the Styrene-Butyl Acrylate-K_sS_sO_s-water in the presence of Barium Sulfate(BS)powder was investigated under varied conditions within the range of BS powder quantity,initiator concentration and reaction temperature.Experimental results showed that the rate of polymerization is proportional to 0.3-power of the BS quantity and 1.3-power of the initiator concentration.There is a linear relationship of 2/3-power for the conversion and time.A process for the polymerization is propose to explain the experimental results.展开更多
In this paper, the near-critical and super-critical asymptotic behavior of a reversible Markov process as a chemical model for polymerization was studied. The results of the present paper, together with an analysis of...In this paper, the near-critical and super-critical asymptotic behavior of a reversible Markov process as a chemical model for polymerization was studied. The results of the present paper, together with an analysis of the sub-critical stage, establish the existence of three distinct stages (sub-critical, near-critical and super-critical stages) of polymerization (in the thermodynamic limit as N --> +infinity,),depending on the value of strength of the fragmentation reaction. These three stages correspond to the size of the largest length of polymers of size N to be itself of order log N, Nm/m+1 (m greater than or equal to 2, m not equal 4n, n greater than or equal to 1) and N, respectively.展开更多
We consider a modified Lnshnikov process as a model of a chemical polymer ization anf study the asymptotic behavior (in the thermodynamic limit;as N →∞)of a particular probability distribution on the set of N-dimens...We consider a modified Lnshnikov process as a model of a chemical polymer ization anf study the asymptotic behavior (in the thermodynamic limit;as N →∞)of a particular probability distribution on the set of N-dimensional vectors,tile kth component of which is the number of k-mers.The study study establisles the existence of three stages (subcritical,near-critical and supercritical stages)of polymerization,dependenting upon the ratio of association and dissociation rates of f polymers.The present paper concentrates on the analysis of tile subcritical stage.In the sibcritical.stages we show that tile size of the largest length of polymers of stize N is of the order.log N as N →+∞.展开更多
文摘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.
文摘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 150C.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.
基金supported by the National Key Research and Development Program of China(Grant No.2018YFB2001002)。
文摘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.
基金supported by the National Natural Science Foundation of China under grant No.50675045the State Key Lab of Advanced Welding Production Technology(Harbin Institute of Technology).
文摘A series of polyurethane (PU)/vinyl ester resin (VER) simultaneous IPNs (interpenetrating polymer networks) with different component ratios and comonomers types introduced to VER were synthesized and the polymerization processes were traced by Fourier transform infrared spectroscopy (FTIR) to study the kinetics of IPNs and hydrogen bonding action within multi-component. Furthermore, the relationship of polymerization process with morphology was investigated in detail for the first time by the morphological information given by chemical action between two networks besides physical entanglement, atomic force microscope (AFM) observation and dynamic mechanical analysis (DMA). The results indicated that the degree of hydrogen bonding (Xb,UT,%), calculated from functional group conversional rate and fine structures gained from FT-IR spectra of two networks, were affected by PU/VER weight ratios and comonomer types of VER. The relationship of formation kinetics and morphology showed that the change of Xb,UT (%) values exhibited excellent consistency with that of phase sizes observed by AFM and detected by DMA.
文摘The process of emulsifier-free copolymerization of the Styrene-Butyl Acrylate-K_sS_sO_s-water in the presence of Barium Sulfate(BS)powder was investigated under varied conditions within the range of BS powder quantity,initiator concentration and reaction temperature.Experimental results showed that the rate of polymerization is proportional to 0.3-power of the BS quantity and 1.3-power of the initiator concentration.There is a linear relationship of 2/3-power for the conversion and time.A process for the polymerization is propose to explain the experimental results.
基金supported in part by National NaturalScience Foundation of China!196610O3
文摘In this paper, the near-critical and super-critical asymptotic behavior of a reversible Markov process as a chemical model for polymerization was studied. The results of the present paper, together with an analysis of the sub-critical stage, establish the existence of three distinct stages (sub-critical, near-critical and super-critical stages) of polymerization (in the thermodynamic limit as N --> +infinity,),depending on the value of strength of the fragmentation reaction. These three stages correspond to the size of the largest length of polymers of size N to be itself of order log N, Nm/m+1 (m greater than or equal to 2, m not equal 4n, n greater than or equal to 1) and N, respectively.
文摘We consider a modified Lnshnikov process as a model of a chemical polymer ization anf study the asymptotic behavior (in the thermodynamic limit;as N →∞)of a particular probability distribution on the set of N-dimensional vectors,tile kth component of which is the number of k-mers.The study study establisles the existence of three stages (subcritical,near-critical and supercritical stages)of polymerization,dependenting upon the ratio of association and dissociation rates of f polymers.The present paper concentrates on the analysis of tile subcritical stage.In the sibcritical.stages we show that tile size of the largest length of polymers of stize N is of the order.log N as N →+∞.