最新刊期
卷 ， 期 8 ， 2008
- 摘要：Poly(acrylonitrile-butadiene-styrene)(ABS) composites containing (i) hindered amine light stabilizer(HALS);(ii) nano-scale rutile titanium dioxide (n-TiO2); and (iii) both HALS and n-TiO2 were prepared by meltblending process.To prevent agglomeration of nanoparticles,the surface of the n-TiO2 nanoparticles were modified to ensure a good dispersion.The pure ABS and ABS composite samples were under accelerated aging test for 28 days with a laboratory xenon arc lamp (GB/T16422.2-1999),and their ageing resistant properties were investigated by Izod unnotched impact,Izod notched impact properties measurements and fracture surface analysis.The morphologies of the unnotched impact fractured surface of pure ABS and ABS composites samples at different irradiation time were characterized by scanning electron microscope (SEM) and optical microscope.According to the SEM photos of brittle fracture (liquid nitrogen immersion) and impact fracture,it can be seen that cavities and knobs on fracture surface were formed by rupture of rubber phases dispersed in ABS when it was under lateral impact.On the other hand,the n-TiO2 less than 100 nm dispersed uniformly in ABS with no evident large agglomerated particles was helpful to its function as ultraviolet screen agents.With the UV shielding capability of nano-scale rutile TiO2 and HALS,the ageing resistance of ABS samples was improved.Moreover,the ageing resistance of ABS/n-TiO2/HALS composites samples is better than that of ABS/n-TiO2 and ABS/HALS composites samples,suggesting a synergistic effect between HALS and n-TiO2.After 28 days exposure to xenon arc lamp the retained percentage of Izod unnotched impact strength of ABS/2.0 wt% n-TiO2/0.6 wt% HALS composites samples was 47.9%,which was more than 2.5 times as high as that of pure ABS.At the same time the retained percentage of unnotched impact strength of ABS/0.6 wt% HALS composites samples was 29.2% after 28 days exposure to xenon arc lamp,which is attributed to diffusion n-controlled oxidation.The retained percentage of Izod unnotched impact strength of ABS/0.5 wt% n-TiO2 composites was only 23.8% after 28 days exposure to xenon arc lamp.The presence of n-TiO2 could confine degradation in a thin region close to the exposed surface.It is obvious that n-TiO2 could not only shield the ultraviolet irradiated on ABS but also prevent impurity and HALS in ABS from being destroyed by ultraviolet.ABS/05 wt% n-TiO2/HALS composite samples had a higher unnotched impact strength,which was increased by 15.3% compared to pure ABS samples,and the tougheness of ABS was increased to a great extent.By impact fracture surface morphology analysis it was found that for unstabilized ABS specimens,there was a bigger smooth zone on fracture surface with very little impact strength retained only after four days laboratory weathering exposures.There is a correlative relation between proportion of smooth zone and retained percentage of unnotched impact strength of pure ABS samples after accelerated aging.The whole unnotched impact fractures surface of exposed and unexposed ABS/2.0 wt% n-TiO2/0.6 wt% HALS composites were white or gray,just as unnotched impact section of unexposed pure ABS,and there were few rubber particles and cavitation left by the pull-off of them exposed on the section.
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发布时间：2021-03-19 - 摘要：The effect of viscoelasticity on the drop deformation,breakup and coalescence is a challenging topic in polymer processing as well as in drop dynamics which is still mainly based on the analysis of Newtonian fluids.In this study,the viscoelastic liquids used for drops were mainly low molecular weight polyisobutylene (PIB) containing high molecular weight polyisobutylene (HPIB).The mass fractions of HPIB were 0.1%,0.5% and 1% covering polymer concentrations from dilute to entanglement.The matrix was made of polydimethyl siloxane (PDMS),a Newtonian liquid and the viscoelastic fluid of PDMS with 5% silicone rubber (HPDMS).After iterative elongation and relaxation in a four-roll mill rheometer,a meso-scale viscoelastic drop turned into dumbbell like structure,two beads connected by one string,which was called BSB (bead-string-bead) according to its shape.It is found that the string does not break for a long time and its length decrease exponentially,the two beads at string ends coalescence eventually.During the coalescence process,the string diameter nearly keeps constant below a critical value.This phenomenon is unlike the existing coalescence of Newtonian drops through stages of matrix film formation,drainage,rupture and drop merge.Moreover,BSB coalescence is different from the known phenomenon of beads-on-string in which the viscoelastic string reduces several orders of magnitude and breaks ultimately.A model is provided based on the force balance of BSB.The elastic force from stretched molecules in the string pulls the two beads approach overcoming the viscous drag of matrix,the string is drained into beads under the Laplace force.In case of the string diameter is a fixed value,the model predictions agree with experiments reasonably.Only in this ideal condition,the relaxation time of material in string matches with the time of string length change keeping the string diameter stable.The critical string diameter is related to both microscopic material parameter (the initial stress in string and the relaxation time of fluid) and macroscopic process parameter (viscosity of matrix,droplets diameters,string length) in the model.If the stress in string is too large,the string diameter will increase; if the viscosity of matrix is too high,BSB phenomenon will transfer to unstable beads-on-string.When the viscosity of matrix is infinity,BSB structure can be reduced to the case of filament stretching rheometer.Indeed,both phenomena are dominated by stretched viscoelastic stress relaxation and interfacial tension.BSB phenomenon is inspiring for the basic understanding of the orientation and entanglement state of polymers and the nonlinear drop dynamic in multiphase systems.
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发布时间：2021-03-19 - 摘要：The effect of hydrolysis derivatives of hexachlorocyclotriphosphazene (HCCP) on its thermal vacuum polymerization was investigated.FTIR and 31P-NMR spectra were used to analyze the impurities in HCCP.The impurity removing effectiveness of different purification methods and the influence of residual impurities on thermal vacuum ring-open polymerization reaction of HCCP were studied.Poly(bistrifloroethoxy)phosphazene (PTFEP) was synthesized according Allock’s method by using HCCP which was purified with different methods.FTIR, 31P-NMR,WAXR,DSC and GPC were used to analyze the characteristic properties of PTFEP.The results showed that HCCP with chloroattached rings could be hydrolyzed by water vapor in the atmosphere and generated impurities such as Trimer-1,Gem-2,Dimmer-3,et al.Recrystallization can remove Gem-2,Dimmer-3 and some Trimer-1.There were still some Trimer-1 remaining in HCCP purified only by recrystallization.Sublimation can remove trimer-1 well.In the process of thermal vacuum ringopen polymerization of unpurified HCCP (250℃,10 Pa),with unpurified monomers,which contained impurities of Trimer-1,Gem-2 and Dimmer-3,the soluble polydichlorophosphazene (PDCP) could be got only when the polymerization time was within range of 8 h and the monomer conversion was 6.8%. When the polymerization time exceeded 10 h crosslinking polymer appeared.When HCCP purified by twice recrystallization or by one recrystallization plus one sublimation was used as polymerization monomer,the conversion of the former were 21.4% (64 h) and 32.6% (78 h),that of the latter were 60.0% (64 h) and 70.6% (78 h),and no crosslinking polymer appeared.For the polymer PTFEP made from HCCP purified by recrystallization or by recrystallization plus sublimation,its crystalline state,crystallinity,glass temperature,crystalline state conversion temperature and the melting temperature also changed.The FTIR spectra showed that there were phosphinyl (1621 cm-1) and imino (2971 cm-1) groups existed in PTFEP systhesized with HCCP purified only by recrystallization.It was considered that the hydroxy groups in Gem-2 and Dimmer-3 resulted in crosslinking of PDCP and unsoluble polymerization.The inpurity of Trimer-1 reduced the polymerization rate,brought in the phosphinyl and imino groups in the polymer and then influences its characteristic properties.It’s the reason that the yield of soluble polydichlorophosphazen produced from HCCP purified just by recrystallization was smaller than that from HCCP purified by recrystallization and sublimation.FTIR or 31P-NMR analysis were advised to validate the purified effect of HCCP and assure the polymerization.
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发布时间：2021-03-19 - 摘要：The goal of this work is to explore new polyimide materials that exhibit both a high permeability and a high selectivity for specific gases.Copolyimides offer the possibility of preparing membranes with gas permeabilities and selectivities not obtainable with homopolyimides.A series novel fluorinated copolyimides were synthesized with various diamine compositions by chemical imidization in a two-pot procedure.Polyamic acids were prepared by stoichiometric addition of solid dianhydride in portion wise to the diamine (s).The gas permeation behavior of 2,2′-bis(3,4′-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA)-2,6-diamine toluene(DAT)/1,3-phenylenediamine(mPDA) polyimides were investigated.The physical properties of the copolyimides were characterized by IR,DSC,and TGA.Glass transition temperature increased with increase in DAT content.All the copolyimides were soluble in most of the common solvents.The gas permeabilities coefficients decreased with increasing mPDA content; however,the permselectivity of gas pairs such as H2/N2,O2/N2,and CO2/CH4 was enhanced with the incorporation of mPDA moiety.The permeability coefficients of H2,O2,N2,CO2 and CH4 were found to decrease with the increasing order of kinetic diameters of the penetrant gases.6FDA-2,6-DAT/mPDA (3∶1) copolyimide and 6FDA2,6DAT polyimide had high separation properties for H2/N2,O2/N2,CO2/CH4.The H2,O2 and CO2 permeabilities were 64.99 Barrer,5.22 Barrer,23.87 Barrer and 81.96 Barrer,8.83 Barrer,39.59 Barrer respectively at 35℃ and 0.2 MPa (1 Barrer=7.5×10-14 cm3 (STP.cm.cm-2.s-1.Pa-1); and the ideal selectivities of H2/N2,O2/N2 and CO2/CH4 were 69.61,6.09,63.92 and 53.45,5.76,57.41,respectively.Moreover,all of the copolyimides studied in this work exhibited performance near,lying on or above the existing upper bound trade-off line between permselectivity and permeability.It may be utilized as commercial gas separation membrane material.
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发布时间：2021-03-19 - 摘要：The microstructure of copolymer chains,the system stability of miniemulsion copolymerization and the free radical copolymerization were influenced by the hydrolysis degree of miniemulsion copolymerization of γ-methacryloxypropyltrimethoxysilane (MPS) and styrene (St) was investigated in terms of the ratio of MPS and St,the pH value of medium,the surfactant amount,the type and amount of initiators.The hydrolysis degree was calculated from the methanol concentration during the process of reaction which could be followed by the gas chromatography.Because of the weak dependence on the type of initiators but strong dependence on the surfactant amount of the hydrolysis degree,the interfaces of mini-droplets and latexes were considered as the main locus of the hydrolysis reactions.The amount of hydrolyzed MPS increased with the increase of the ratio of MPS and St,but the final hydrolysis degree was independent of this ratio.The hydrolysis rate was accelerated by either decrease or increase of medium’s pH value.However,compared to the formation of gels under acidic condition in conventional emulsion polymerization,the reaction system was stable,and the final product was stable in the miniemulsion mode which was attributed to the partition of the most of hydrolyzed MPS molecules at the interface of the droplets or particles as a result of the large surface area of droplets or particles in the miniemulsion system.Consequently,the condensation reactions in aqueous phase which were regarded as the main reason of gel product formation decreased corresponding to the decrease of the amount of hydrolyzed MPS in aqueous phase.The hydrolysis degree increased with the increase of surfactant amount as a result of the decrease of the droplets size which in turn increased the surface area of droplets.In the system initiated by KPS,as the polymerization proceeded,the pH value of the medium would decrease because of the formation of acidic groups as a result of the decomposition of KPS.Therefore,with the increase of the amount of initiator the hydrolysis degree increased.The condensation reactions were followed by the 29Si solidstate NMR.Under neutral conditions,the condensation reactions were suppressed effectively even with 1∶1 ratio of MPS and St.The condensation reactions could not be avoided at an acidic pH values,but it could be minimized at a basic pH attested by the presence of a signal at δ =-43 corresponding to silicon atoms belonging to noncondensed MPS.Because the condensation reaction rate was slower under the acidic condition than that under the basic condition,the T2 species,the intermediate resultant of condensation,dominated in the final product under acidic condition,while the T3 species did in the final product under the basic condition.Compared to the emulsion polymerization,the hydrolysis and condensation reactions were more easily controlled in miniemulsion polymerization because of its droplet nucleation mechanism and little mass transfer between droplets which could reduce the contacting opportunity of MPS molecules and water.
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发布时间：2021-03-19 - 摘要：A series of main chain liquid crystalline copolyesters with X-shaped two-dimensional mesogenic units and crown ether cycles of cis-4,4′-bis(4-hydroxyphenylazo) dibenzo-18-crown-6 was synthesized via solution cocondensation polymerizations from 4,4′-(α,ω-octanedioyloxy) dibenzoyl dichloride(M1),2,5-bis(p-decyloxyphenylbenzoyloxy)hydroquinone (M2) and cis-4,4′-bis(4-hydroxyphenylazo) dibenzo-18-crown-6 (M3) as the monomers.Monomer M1 was synthesized by esterification and substitution reactions of p-hydroxybenzoic acid and octanedioyl chloride.Monomer M2 was synthesized by esterfication and reduction reactions of 2,5-dihydroxybenzoquinone and p-decyloxyphenylbenzoyl chloride.Monomer M3 was synthesized by diazotization and coupling reactions of cis-diaminodibenzo-18-crown-6 and phenol.The molecular weights of copolyesters were not high,and the ［η］ of the copolyesters was in the range the of 0.39～0.30 dL/g.The monomer structures were identified by using elementary analysis,IR,UV,1H-NMR and MS etc.All the copolyester samples were yellowish powders and insoluble at room temperature in THF and CHCl3 except the sample CP9. The properties of copolyesters were investigated by using GPC,［η］,DSC,TG,WAXD and POM.It was found that all the copolyesters went into liquid crystal phase when they were heated over their melting temperature (Tm).CP2～CP8 can exhibit both smectic and nematic phases, and the typical liquid crystal textures of smectic and nematic phases can be observed. CP1 and CP9 only have nematic phase. The melting temperature and isotropic temperature (Ti) of all copolyesters increased regularly with increasing the cis-4,4′-bis(4-hydroxyphenylazo) dibenzo-18-crown-6 unit content in the copolyesters for the reason that the flexibility of —OCH2OCH2— chains in comonomer M3 rendered the copolymer to build up regular structure easily and increase its degree of ordered arrangement. The temperatures of 5% weight loss, (Td) in TG experiments were in the range of 318.5～366.3℃ and increased with an increase of the content of T-shaped mesogenic units in the copolyesters. The reason is that the T-shaped two-dimensional mesogenic unit has a very rigid structure and high thermal stability. Increasing the content of T-shaped two-dimensional mesogenic units will improve the thermal stability of the copolyesters. The WAXD studies illustrated that the copolyesters were liquid crystalline with a nematic phase. A dispersive peak at 2θ near 20° appeared in their WAXD patterns, which is a typical character for quenched nematic liquid crystal copolyesters.
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发布时间：2021-03-19 - 摘要：The crystallization of semi-crystalline polymers is often influenced by processing,and their crystallization may also influence the processing simultaneously.The present study is an attempt to simulate the two aspects of the injection moldings of semi-crystalline polymers.Firstly,by assuming that the effect of flow on crystallization is only in terms of increasing the crystallization rate constant,an approach based on the quiescent-state crystallization equation is proposed to develop the qualitative description of crystallization phenomena under non-isothermal flow occurring in injection molding processing.The energy of dissipation,the work of stress occurring in the injection molding operations,is regarded as the main parameter of the equation of the crystallization rate.Secondly,the proposed modeling of the flow-induced crystallization kinetics is directly applied to predict the development of the crystallinity during the injection moldings of two semi-crystalline polymers:fast-crystallizing polymer isotactic polypropylene (iPP) and slow-crystallizing polymer polyethylene terephthalate (PET).In the prediction,the kinetics of crystallization is considered in the simulateion of three stages:filling,packing and cooling of injection molding,and the parameter reflected the effect of crystallization is included in the equation of the relationship of stress and strain,along with the equations of continuity,momentum and energy conservation,the equation of state and other parameters of materials;the flow-induced effect is also considered and the energy of dissipation is regarded as the main parameter in computing the kinetics of crystallization.Finally,the conclusion can be drawn after the simulated data for the development of crystallinity and the distribution of temperature and pressure field in the moldings are compared and analyzed.Although the results show the kinetics of flow-induced crystallization has little influence during the process of computing the distribution of the pressure field,it is obvious that the processing can expedite crystallizing,and the crystallization also influences the processing of materials especially the temperature field distribution for the packing and cooling stages of injection molding of the iPP and PET.The result shows also that the proposed kinetics model has a minimum of unknown material constants and predicts the most prominent features of flow-induced crystallization.In addition,comparison is also made between PET and iPP,and it demonstrates that the mutual influence of flow and crystallization kinetics is different during the injection molding process for materials with different crystallization properties.For the fastcrystallizing polymer iPP,flow has little effect on the final crystallinity but relatively higher heat release and large influence of the distribution of the temperature field in the injection molded parts,and the situation for PET is opposite.
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发布时间：2021-03-19 - 摘要：A series of gelatin microspheres (GMs) were prepared through emulsificationcoacervation method in water-in-oil (w/o) emulsions.The influence of preparation parameters on particle size,surface morphology and dispersity of GMs was examined.The studied preparation parameters include concentration of gelatin solutions,concentration of the emulsifier,water/oil ratio,emulsifying time,stirring speed and so on.The surface morphology,dispersity and particle sizes of GMs were determined by the scanning electron microscopy (SEM),SemAfore 4 Demo software and particle size distribution graphic charts.The experimental results indicated that increasing the concentration of gelatin solution would increase the particle size of GMs.When the solution concentration increasing from 0.050 g/mL to 0.200 g/mL gradually,the particle size increased correspondingly.The relationship between the two quantities was linear.On the contrary,increasing the concentration of the emulsifier would decrease the particle size of GMs.Furthermore,the particle size reduced quickly at initial time and slowed down latterly.With the increase of emulsifier concentration from 0 to 0.020 g/mL,the mean diameters of GMs decreased from 17.32 μm to 5.38 μm.However,the particle size dwindled slowly when emulsifier concentration was higher than 0.020 g/mL.The excellent result was obtained with the condition:0.050 g/mL of emulsifier concentration,0.100 g/mL of gelatin solution concentration,1/5 of water/oil ratio,10 min of emulsifying time and 900 r/min of the stirring speed.The GMs prepared at this condition had the smallest sizes,the narrowest size distribution,the best sphericity and fluidity.The water/oil ratio has the same influence on particle size of GMs as that of gelatin solution concentration.With the increase of water/oil ratio the average particle size increased linearly,and the surface of microspheres became smoother as well.It is supposed that water/oil ratio can be used to change the diameters and surface morphologies of GMs.The emulsifying time had little influence on the mean diameters of GMs,but it affected the dispersity of GMs apparently.When the emulsifying time was shorter than 5 min,the GMs had bad dispersity;after increasing the emulsifying time to 13 min,the dispersity of GMs changed greatly;whereas the dispersity of GMs became bad again when the emulsifying time was longer than 13 min.According to the experimental results,13 min was considered to be the best emulsifying time.The stirring speed had the similar influence on GMs’ morphologies as that of emulsifying time.Slow stirring rate made large size distribution and bad sphericity of GMs;excessive stirring speed resulted in aggregation among GMs likewise.The smaller size distribution and better sphericity of GMs were observed under the stirring rate between 500 r/min to 1500 r/min by SEM.In conclusion,increasing the concentration of gelatin solution or w/o ratio would increase the particle sizes of GMs,increasing the concentration of the emulsifier would decrease the sizes of GMs,proper emulsifying time and stirring speed would resultin in the best sphericity of GMs.
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发布时间：2021-03-19 - 摘要：Hybrid calcium carbonate particles,synthesized in the presence of block copolymer polystyrene-b-poly-(acrylic acid) (PS-b-PAA),were used to fabricate polyelectrolyte (PE) such as polylallyamine hydrochloride)/poly(strene-sulfonate sodium)(PAH/PSS) and poly(diallyldimethyl ammonium chloride)/poly(styrene sulforate sodium)(PADH/PSS) capsules by layer-by-layer(LbL) technique.Novel micelle-enhanced polyelectrolyte (PE) capsules were thus obtained.The structure of the micelle-enhanced PE microcapsules was studied in this article.Due to the presence of a large amount of negatively charged micelles inside PE capsule interior,which were liberated from templates,the capsule wall was tightly re-constructed.Different from the wall properties of the conventional PE capsules,the wall of the micelle-enhanced PE capsules showed stability under an extensive pH range from 1 to 14,but the micelled enhanced capsules showed dented morpholog in solutions with high NaCl concentration such as 0.5 mol/L and 1 mol/L.The state of the block copolymer in the capsules was investigated in dialysis bag by simulating the solution condition of the capsule interior after the template being removed.It was found that the micelle size of the block copolymer in solution of templates dissolution was tens of nanometers after the solution was dialyzed for 24 h.With the dialysis time increasing up to at least 72 h,the block copolymer began to precipitate onto the dialysis bag from the solution.The interaction between the 2-D polyelectrolyte multilayer film and micelles formed by block copolymer in templates solution was studied by UV-Vis measurements as well.It was found that PE multilayer could interact with micelles via electrostatic force.At the same time,the block copolymer remained in the capsules interior could be precipitated onto the PE multilayer via dialyzing in deionized water for a long time (pH～6).A micelle-related layer was formed which was stabilized by the “bridge effect" of calcium ions.That is,the wall of the micelle-enhanced PE capsules had a bilayer structure and was formed by the polyelectrolyte multilayer and micelle-related layer.It seemed that the two layers with different properties clung to each other via electrostatic force.The formation mechanism of the bilayer structure was well illuminated on the aforementioned studies.This is a key property of the micelle-enhanced PE capsules with which all the properties of the capsules were linked.Based on the bilayer structure of the capsules,the morphology changes of the capsules in solutions with different conditions such as high NaCl concentrations could be elucidated well.However,more direct proofs and further studies were needed to completely resolve the fine structure of the micelle-enhanced PE capsules.
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发布时间：2021-03-19 - 摘要：Fe3O4 magnetic nanoparticles with mean diameter of about 20 nm were first prepared by a precipitation method with ferric chloride as starting material,which was partially reduced to ferrous salts by Na2SO3 before alkalinizing with ammonia.Afterwards,C=C end groups were imported to the surface of Fe3O4 magnetic nanoparticles by silane coupling agent treatment,and then polyvinylpyrrolidone (PVP) with hydroxyl end groups was grafted on the surface by addition polymerization of N-vinylpyrrolidone (NVP) with the C=C bonds.The resultant magnetic initiator was further used to polymerize lactide (LA) to generate the designed PVP-b-PLA modified Fe3O4 magnetic nanoparticles.The characterization of the production was analyzed through XRD,GPC,FTIR,SEM,TG,DSC and laser particle size analyzer.The XRD spectra of PVP-b-PLA modified Fe3O4 magnetic nanoparticles were very similar to those of non-modified nanoparticles,suggesting that the crystal lattice did not change after surface polymerization,which was still the face centered cubic (fcc) structure.There appeared a new wide diffraction peek from 10° to 25° belonging to the surface coatings,which exhibited that the surface polymers were noncrystalline.According to the FTIR analyses,there were chemical bonds between Fe3O4 and PVP and between PVP and PLA.DSC studies indicated that PVP and PLA were linked in the form of block copolymer,and there were apparently micro-phase separations between the two blocks.The results of TG analyses indicated that the coating amount of PVP and PLA was about 15% and 20%,respectively.SEM and laser particle size analyses showed that the composite nanoparticles had a relatively uniform diameter of about 45 nm,and the thickness of the coated copolymer layer was about 13 nm.In addition,the specific saturation magnetization of PVP-b-PLA modified magnetic nanoprarticles was 53 emu/g,which declined by 25% compared to that of bare Fe3O4 nanoparticles.The graft of PVP-b-PLA on the surface of Fe3O4 magnetic nanoparticles on the one hand can endow the Fe3O4 nanoparticles with excellent degradation properties,on the other hand it can make the magnetic nanoparticles with good biocompatibility after degradation because of the covering of PVP,and further it can also endow the particles with more chemical selectivity for further surface functionalization due to the hydroxyl end groups,so these PVP-b-PLA modified Fe3O4 magnetic nanoparticles will provide a platform for potential applications in drug controlled release systems,magnetic targeting drug delivery systems and tumor hyperthermia treatments.
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发布时间：2021-03-19 - 摘要：Positively charged Poly[2-(methacryloyloxy)ethyltrimethylammonium chloride〕 (PMTC),which has been often used as cationic polymeric flocculants,was chosen to coacervate with acacia to form microcapsules.As a simulacrum of insect sex pheromone molecule,dodecanol was used as the core material in this study.PMTC was prepared by polymerizing monomer ［2-(methacryloyloxy)ethyltrimethylammonium chloride] (MTC) with 2,2′-azobis(2-methylpropionamide) dihydro-chloride as initiator at 70℃.Complex coacervation of PMTC and acacia was optimized by varying experimental conditions, i.e. PMTC to acacia ratio,total polymer concentration and ionic strength etc. It was observed that maximum complex coacervation yield of 90% could be achieved with polymer concentration of 4% and the acacia/PMTC mass ratio of 3.22.Coacervation temperature and the order of polyelectolite solution addition (i.e. acacia added into PMTC solution or inversely) had no important effect on coacervation yield.Complex coacervation was partially suppressed by addition of sodium chloride.The optimized system was used for the encapsulation of dodecanol with different wall/core ratios.The microcapsules of size around a few microns were prepared.Good agreement was observed between the capsule size determined by optical microscope and that by light scattering.It was found that increasing wall/core ratio would cause a reduced dodecanol loading in the capsules.With 4 wt% wall material concentration,this loading declined from 4.98% with wall/core ratio at 8/1 to 3.07% with wall/core ration 12/1; and a very similar variation in dodecanol loading was seen with 5 wt% wall material concentration.Whereas the encapsulation rate of dodecanol,being 38% and 41% with 4 wt% and 5 wt% wall material concentration,respectively,at low wall/core ratio (8/1 to 9/1); this rate was reduced to about 33% with increase in wall/core ration to 12/1 regardless of the wall material concentration. The release behavior of dodecanol from the capsules was also changed due to different dodecanol loading.With reducing the amount of dodecanol added in the preparation, i.e. with increasing the wall/core ratio,the rate of dodecanol release rate was regularly decreased,a minimum release rate was detected in capsules prepared with wall/core ration at 12/1. As a general observation,a relatively rapid release was observed during the first 20 days,followed by a slower release rate for all the samples.Regardless of the wall material concentration,capsules with dodecanol loading below 4 wt% reached their final release around 20 days when incubated at 30℃ with constant relative humidity (50%),while those with 5 wt% loading remained active even after 60 days under the same experimental conditions.
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发布时间：2021-03-19 - 摘要：In order to improve the ambient conductivity of all-solid-state electrolytes as well as enhance the diffusion number of lithium ion,all-solid-state polyphosphazene electrolytes containing nanoSiO2 modified with poly(oxyethylene-co-oxypropylene) silane were prepared.The macromonomer of polyphosphazene was prepared through reaction of phosphazene with poly(oxyethylene-co-oxypropylene) monoacrylic ester and poly(ethylene glycol) monomethylether with the yield of 92.6%.Silane coupling agent with polyether was prepared by the hydrosiloxane addition reaction between trimethyloxyl siloxane and allyl poly(ethylene-co-propylene glycol) methyl ether.The silane coupling agent refluxed with SiO2 to form nanoSiO2 modified with poly(oxyethylene-co-oxypropylene) silane.The FT-IR spectrum and XPS together show that SiO2 has been successfully modified by the soft chain.The SEM images of composite electrolytes show that modified nano SiO2 could easily disperse among polymer electrolyte with only a little conglomeration.It is found that the nanoSiO2 content in electrolyte fixed at 10% could reach the best ambient conductivity of 3.14×10-4 S cm-1,which is 2.4 times higher than that of the noncomposite system.Differential scanning calorimetry of nanocomposite solid state electrolytes showed that the glass transition temperature of the electrolyte did not change with the variation of nanoSiO2 content from 2% to 10%,which indicated that nano SiO2 modified with polyether did not change the crosslinking density of nanocomposite system,and the polyether chain could maintain the original flexibility of the solid state electrolytes.The conductivity of electrolyte is increasing with the increase of temperature,which obeys the VTF equation.When the temperature rises up to 50℃,the electrolyte with 10% modified SiO2 shows the best conductivity of 10-3 S cm-1,the corresponding active energy is 4.07 kJ mol-1. The high conductivity can be explained on the one hand,the polyphophazene monomer has the side chain of oxyethylene,which is helpful to solve the lithium salt,the copolymerization of oxyethylene and oxypropylene reduces the glass transition temperature of the polymer and inhibits the crystallization of polyoxyethylene; on the other hand,the nanoparticles modified with soft polyether chains can uniformly disperse in the polymer electrolyte,and the polyether plays the role of plasticizer.The result of DSC also proves such explanation.With increasing the content of lithium salt,the ionic conductivity first increases,then shows a subsequent decline.The highest ambient conductivity of nanocomposite electrolyte is obtained when the concentration of lithium perchlorate is fixed at 8%.The addition of nanoSiO2 reduces the formation of ion cluster.Cyclic voltammogram gives the result of good electrochemical stability of nanocomposite electrolyte and an electrochemical window of more than 4.2 V.Alternating current impedance spectrum accounts for the good interfacial stability between electrolyte and electrode after 7 days of the assembling of the cell,which was explained by the composition of nanoparticles modified with flexible chains which may reduce the interfacial impedance and help the transfusion of ions.The diffusion number of lithium ion in the nanocomposite all-solid-state polymer electrolyte is realized through stable current method,the result indicates that the ion diffusion number increased from 0.25 to 0.34 due to the composite of nanoparticles.
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发布时间：2021-03-19
Research Article
- 摘要：Recently,polypropylene toughened and strengthened by ultrafine calcium carbonate (CaCO3) has become more and more popular.But for its high surface energy,the compatibility between CaCO3 and polypropylene is poor,so the surface of CaCO3 must be modified before use.In this article,CaCO3 whose surface was pretreated first by acrylic acid (AA) to introduce active double bond groups, was coated chemically by polypropylene wax (PPW) via solid-phase coating polymerization.Compared to traditional solid-phase grafting polymerization,this method has some differences.First,the reaction is not between monomers of small molecular weight and polymer,but between CaCO3 pretreated by AA and PPW; Second,the polymer is usually a solid phase mass under the reaction temperature in the traditional solidphase grafting polymerization,but in this method PPW is in the liquid phase, and the CaCO3 pretreated by AA in the solid phase.Third,in traditional method the reaction is the monomers grafting to the polymer’s surface,but in this method the coating reaction is PPW to the AA on the CaCO3’s surface.As this method can occur in high-speed mixer,it is more convenient and feasible comparing to the traditional grafting reaction which is usually in extruder or reactor.In this article,it is found that coated CaCO3 can stand the treatment of both methyl benzene and dilute hydrochloric acid.Combined the results of FTIR and TGA,the conclusion can be made that PPW has been coated successfully with polyacrylic acid on the surface of CaCO3After filling the coated CaCO3 into polypropylene (PP),it shows that the impact and tensile properties of PP are improved in somewhat degree.When the content of the coated CaCO3 is 15 phr,the notched impact strength of the PP composite is 1.68 times as high as that of PP.When the content is 10 phr,the tensile strength of PP filled with coated CaCO3 is 1.22 times higher than that of PP filled with uncoated CaCO3 at same contents
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发布时间：2021-03-19 - 摘要：A custommade dynamic injection molding machine was adopted to obtain PP specimens via changing the vibration frequency (5～25 MPa) and vibration stress (10～18 MPa).The specimens were characterized by tensile tests,notched Izod impact tests,dynamic mechanics analysis and creep measurements under a tensile load of 12 kg.For specimens prepared under a vibration frequency of 10 Hz their 24 h creep strain decreased from 7.4% to 4.5% with an increase of vibration stress from 10 MPa to 18 MPa.While for specimens prepared under a vibration stress of 12 MPa their 24 h creep strain increased with vibration frequency first,and after 10 Hz its variation became very slow.It was also found for these specimens that the Izod impact strength increased from 3.2 kJ/m2 to 4.2 kJ/m2,when the vibration stress changes from 10 MPa to 18 MPa,and,at the same time,the Izod impact strength decreased with increasing vibration frequency first and showed a minimum around 20 Hz.The influence of processing conditions on tensile elongation and dynamic mechanical properties were also observed.All the results indicated that within the experimental conditions used in this work increasing the vibration stress and decreasing the vibration frequency during processing could improve the long-term mechanical performance and impact ductility of PP specimens.
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发布时间：2021-03-19 - 摘要：A convenient method was developed to fabricate gold nanoparticles loaded microcapsules in one step and with high efficiency.First of all,the gold colloidal solution was prepared through reduction of AuCl-4 ions with NaBH4 under stirring,and poly(vinylpyrrolidone) (PVP) was added quickly under severe agitation to prevent the aggregation of the gold nanoparticles during the dialyses.The gold nanoparticles in the colloidal solution had a diameter of about 7 nm and had a maximum absorption at 516 nm.Next,template polymerization of acrylic acid (AA) in the presence of PVP and 3-(trimethoxysilyl) propyl methacrylate (MPS) modified silica particles was carried out in the gold colloidal solution.The polymerization was initiated by K2S2O8 and maintained for about 2 h under nitrogen atmosphere.After polymerization,the resulting composite particles were separated from the dispersion through centrifugation and were washed with triply-distilled water for several times.Finally,the gold nanoparticle-loaded microcapsules were obtained after core-removal with HF.In this process,the pre-adsorption of the complex of PVP/AA onto the gold nanoparticles made the nanoparticles polymerizable with free AA monomers during the template polymerization,and the gold nanoparticles doped PAA/PVP complex films were formed on the surfaces of the silica particles.After the core-removal process,the hollow nature and the integrity of the obtained microcapsules in both dry and wet states were demonstrated by scanning electron microscopy and confocal laser scanning microscopy,respectively.The entrapment of the gold nanoparticles in the capsules was confirmed by transmission electron microscopy.Electron diffraction pattern of the nanoparticles-loaded microcapsules showed the gold polycrystalline diffraction rings,from which the lattice constant of crystal plane {1 1 1} was calculated as 0.4174 nm,further confirming the existence of the gold nanoparticles.The gold nanoparticles were distributed uniformly in the microcapsule shells with no sign of aggregations.The amount of nanoparticles loaded in the microcapsule shells could be tuned by the concentration of the gold colloidal solution, i.e. higher concentration resulted in microcapsules with larger amount of gold nanoparticles in the shells.This process can be extended to other types of nanoparticles and polymers,thus can be widely applied to obtain composite microcapsules with desired functions.
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发布时间：2021-03-19
Research Bulletin
- 摘要：A novel series of polybenzazoles with rigid-rod benzobisoxazole cycles and methylene soft segments were designed and synthesized via solution condensation polymerizations from 2,4-diamino-1,5-benzenediol dihydrochloride,terephthalic acid and aliphatic dicarboxylic acids.The molecular structures of polymers were characterized by FT-IR, 1H-NMR,WAXD and so on.The polymers are yellowish amorphous powders or solids and own excellent thermal stabilities (Td470℃).All the polymers are soluble in strong protonic acid at room temperature, and the intrinsic viscosities ［］ are in a range of 0.8～0.9 dL/g.A spot of unclosed ring structure fragments in the polymer chain is found via FT-IR and 1H-NMR,and this is due to the obstacle effect of -H of the aliphatic dicarboxylic acid in the polymerization process.The photophysical properties of polymers in methanesulfonic acid (MSA) were investigated by UV-Vis absorption and photoluminescence spectra.The UVVis absorption spectra of polymers in MSA (4.410-4 g/dL) showed blueshift from 429 nm for PBO to 291 nm for PBOC7. The photoluminescence emission spectrum of PBO reveals two sharp and strong peaks while the spectra of PBOCx all show one featureless broad diffuse peak.The Stokes shifts enlarge from 7 nm for PBO to 145 nm for PBOC3.One possible reason is that the gap between conduction and forbidden bands increases with the introduction of soft non-conjugation methylene segment.Further study is under way.
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发布时间：2021-03-19
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