最新刊期
卷 ， 期 1 ， 2013
- 摘要：The higher price of raw materials and the well-recognized shortcomings of gelatin capsules,such as animal-derived ingredients,lower soft temperature and the instability of moisture in gelatin,have led to attempts to develop replacement substances,such as various vegetable gums,hydroxypropyl methylcellulose cellulose and modified starch.Although there are many patents and publications on the developing various substances for capsules,only a few non-gelatin capsule products have recently entered the market.The reasons for the lower commercial success include the higher price of these new products due to requirements for new processing facilities,and/or more complex processing conditions.This paper discusses the development of capsules made from various natural plant polymers,including both fundamental science such as microstructure,phase transition and rheology,as well as processing techniques and formulations.As one of the most popular food ingredients and has good film-forming behavior,starch has shown great potential.The achievements in this area have increased our knowledge of polymer science,in particular that of natural polymers.Application of extrusion technique in capsule manufacture is a significant achievement.关键词：Starch;HPMC;Gelatin;Edible gums;Natural polymer;Capsule
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发布时间：2021-03-19
Feature Articles
- 摘要：A study on rheological behavior of multi-walled carbon nanotubes (MWCNTs) filled polystyrene (PS) melts submitted to isothermal annealing at temperatures from 170℃ to 190℃ was carried out.It is found that the filled PS melts with different volume fractions () of MWCNTs from 0 to 0.05 underwent dynamic modulus percolation (DMP) during isothermal annealing and the DMP behaviors followed time-temperature superposition (TTS) principle disclosed for the first time.The filled melts with below percolation threshold exhibited liquid-like viscoelasticity during annealing,and the activation energies (EG' and EG) of the dynamic storage modulus (G') and loss modulus (G) were higher and lower than that of viscous flow (E) of pure PS melt,respectively,but were in agreement with the dynamic modulus activation energies of dynamic moduli of PS melt at the same frequency as that used in DMP test,the dynamic moduli were obtained through the dynamic frequency experiment.Annealing the melts having above percolation threshold caused MWCNTs to aggregate further so much as that the melts changed from the liquid-like to the solid-like.In this case,both EG' and EG were smaller than E while energies (Et' and Et) of liquid-like to solid-like transition were significantly higher than E.Moreover,the activation energies of dynamic modulus exhibited a sharp decrease in the percolation transition region.It was suggested that the isothermal time-dependent DMP was closely related to the formation of the MWCNTs aggregation-induced construction of three-dimensional elastic network while the terminal relaxation of PS macromolecules was not the determinant factor for DMP.关键词：Multi-walled carbon nanotubes;Polystyrene;Dynamic modulus percolation
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发布时间：2021-03-19 - 摘要：The crystallization behaviors and crystallization kinetics of iPP in pressure field were investigated by confining-fluid pressure-volume-temperature (PVT) measurement technique.The absolute specific volume of the polymer can be obtained by correcting the relative volume difference with the specific volume of the confining fluid.So it was an effective method by confining-fluid pressure-volume-temperature (PVT) measurement to catch information of crystallization of semicrystalline polymers.The results revealed that molecular chain of iPP was introduced more easily into crystal lattice with powerful free energy of molecular chain improved by pressure field so as to improve the crystallization temperature and crystallization speed.Formula of crystallization temperature with pressure was found by means of data fitting.It was attempted to build a crystallization kinetics model by improving Jeziorny equation which can forecast the crystallization process of the iPP in pressure environment.The results showed that crystallization curves can be suitable for explaining some changes of the crystallization of iPP when crystallinity exceeded 0.08.Growth pattern of crystallization accorded with the behavior of 2-dimensional crystallites.Decrease of free volume was one of the main causes for the increase of crystallization rate.关键词：Confining-fluid PVT measurement technique;Pressure field;Crystallization behavior;Crystallization kinetics
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发布时间：2021-03-19 - 摘要：Poly(ethylene 2,5-furandicarboxylate) (PEF) was synthesized via direct esterification method based on 2,5-furanicarboxylica acid and ethylene glycol.Stannous oxalate was used as catalyst.The results showed that the direct esterification method was a straightforward and convenient effective way for preparing PEF.The results of Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (1H-NMR) confirmed the expected PEF structure.The results of Ubbelohde viscosity method and gel permeation chromatography (GPC) declared the relationship between intrinsic viscosities and weight-average molecular weight was ［］=2.8210-6 Mw0.99 ［dL/g,25℃,phenol-tetrachloroethane (1∶1,W/W)］; The results of differential scanning calorimeter (DSC) displayed that the glass transition (Tg) of PEF was 84℃ which was 16 K higher than that of poly(ethylene terephthalate) (PET) and the melting temperature (Tm) of PEF was 211℃ which was 43 K lower than that of PET.The results of thermogravimetric analysis (TGA) showed that the PEF was thermally stable up to 373℃.PEF had good thermal properties and was similar to that of PET.The results of coaxial cylinder viscometer showed that the PEF melt was a pseudoplastic Newtonian fluid and its Non-Newtonian index increased with decreasing of relative molecular weight and increasing of temperature.Non-Newtonian index was about 0.85 (melting temperature=230~250℃,rate of shear=2.1710-2~1.14102 s-1).关键词：2,5-Furandicarboxylic acid;Poly(ethylene 2,5-furandicarboxylate);Direct esterification method;Synthesis and characterization
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发布时间：2021-03-19 - 摘要：The purpose of this study was to measure and compare the biodegradability of the four cellulose fabrics (cotton,modal,bamboo and tencel) in laboratory and large scale composting environments.Three methods:ASTMD 5988-03,enzymatic hydrolysis and composting were used.Under controlled laboratory conditions,the carbon dioxide produced was monitored and integrated to determine the biodegradation rate by ASTM D 5988-03 method in natural soil,and the weight losses were measured after biodegradation in enzyme solutions.The same set of fabrics was buried in the composting facility for 90 days.The weight losses and the fabric morphology changes after degradation were used to assess and compare the biodegradability with the results obtained under laboratory conditions.IR spectra were used to analysis the structure of the cellulose fabrics before and after biodegradation in different methods.The morphologies of the cellulose fabrics before and after degradation were observed by SEM.The results showed that all competing man-made cellulose fabrics (modal,bamboo and tencel) showed faster degradation rates than the natural cotton fabric.Bamboo fabric showed a significantly faster degradation rate than other cellulose fabrics in the three degradation methods,especially in composting method the bamboo fabric completely destroyed.Combining with IR analysis,it was confirmed that all the cellulose samples had an accelerated degradation rate in the compost environment which contained more multiple organisms and enzymes than under the laboratory conditions.关键词：Biodegradation;Cellulose;Enzyme hydrolysis;Composting
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发布时间：2021-03-19 - 摘要：By using the neodymium chloride compounds(［Nd］)［NdCl34L,L:TBP (tributyl phosphate),TPP(triphenyl phosphate),P204(di(2-ethylhexly)phosphoric acid)］ as the catalyst while the methylaluminoxane (［Al］) as the cocatalyst,the polymerization of 1,3-butadiene could be carried out in cyclohexane to obtain high cis-content and narrow molecular weight distribution polybutadienes.In this article,the polymerization activities,and the molecular weight,the molecular weight distribution and the microstructure of the products were examined on the basis of the the effects of the ligands,the amounts of the methylaluminoxane,the aging time and the solvents on the 1,3-butadiene polymerization.It was considered that the polymerization activities of the ligands were in the order of TBP P204 TPP,which was attribute to the differences among the electron donor group inductive effect of the ligands; when the ［Al］/［Nd］ was 30,the GPC curve was unimodal,indicating the single-active-site in the polymerization process,which revealed that the molecular weight distribution was narrow (1.20).By means of aging at 30℃,the cis-content of polybutadienes were over 97.2% which was determined by IR and confirmed by NMR.Compared with toluene and hexane,by using cyclohexane as the polymerizing solvents,high cis-content and narrow molecular weight distribution polybutadienes were obtained and the catalyst system was at the highest polymerization activity,which revealed that the cyclohexane was the proper solvent for the polymerization.关键词：Neodymium chloride compounds;Methylaluminoxane;High cis-content polybutadienes;Narrow molecular weight distribution
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发布时间：2021-03-19 -
SYNTHESIS AND CHARACTERIZATION OF BIODEGRADABLES POLYURETHANE CONTAINING LIGHT SENSITIVE SIDE GROUPS
摘要：2-Methyl-2-cinnamoyloxymethyl-1,3-propanediol (MCO) as a chain extender was prepared.Polylactide diol (PLA diol) as soft segment,isophorone diisocyanate (IPDI) and MCO as hard segment were used to synthesize biodegradable polyurethane (PU) containing light sensitive groups.The properties of the PUs obtained were characterized by nuclear magnetic resonance hydrogen spectrum (1H-NMR),Fourier transform infrared spectroscopy (FTIR),gel permeation chromatography (GPC),differential scanning calorimetry (DSC) and tensile testing.The results showed that MCO had high enough reactivity to obtain the PUs of high molecular weight,the number average molecular weight of PUs ranged from 41.9?103 to 79.0?103.Crosslinking of the PUs was realized by irradiating the PU solution with UV 365 nm light.The time for complete crosslinking of PU in solutions in the absence of light initiator (2-hydroxy-2-phenylacetophenone) was 25 min,but it was only 5 min in the presence of light initiator.The gel content increased with increasing MCO content in PUs when the PUs had the same soft segment; the gel content decreased with increasing soft segment molecular weight when the PUs had the same hard segment.Rational crosslinking contributed to the increase of tensile strength and shape recovery ratio,the shape recovery ratio of PU reached nearly 100%.关键词：Biodegradable polyurethane;Crosslinking;UV- 50
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发布时间：2021-03-19 - 摘要：The poly(phenylene-ethynylene-carbazole) (PPEC) with 4-vinylaniline pendant groups was synthesized through Pd-catalyzed Sonogashira coupling polymerization between 4-［2-(2,5-dibromophenyl)vinyl］ aniline ( M1 ),1,4-di-2,5-bis(pentyloxy) ( M2 ) and 3,6-dibromo-9- octylcarbazole ( M3 ).The ratio of aniline unit to ethynyl-benzene unit to carbazole unit at 0.54∶1∶0.46 was determined by1H NMR spectrum.When PPEC is aggregated by adding nonsolvents such as water,methanol and hexane into its THF solution,the fluorescence intensity and the maximum emission peak of PPEC changed drastically.The fluorescence intensity gradually decreased upon addition of water into PPEC THF solution before the ratio of THF to water arrived at 50∶50.The fluorescent intensity of PPEC increased in turn after water fraction is beyond 60% in the mixture of THF and water.When methanol was added into its THF solution,however,PPEC showed an aggregation-caused quenching (ACQ) characteristic.The emission of PPEC is only enhanced by aggregation when adding n-hexane into its THF solutions,exhibiting an aggregation-induced emission enhancement (AIEE) effect.The result indicates that amino groups can strengthen the inter-chain and intra-chain interactions in PPEC and restrict the non-radiative energy transition.This strategy thus provides a new concept for designing highly emissive conjugated polymers by adjusting side-group interaction.关键词：Poly(phenylene ethynylene);Carbazole;Amino group;Conjugated polymer;Aggregation-induced emission enhancement
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发布时间：2021-03-19 -
EFFECT OF ALKYLATION DEGREE ON THE STRUCTURE OF N-OCTADECYLATED POLYETHYLENEIMINE COMB-LIKE POLYMERS
摘要：N-octadecylated polyethyleneimine (PEI18C) comb-like polymers with different substitution degrees (DS) ranging from 47%~17.6% have been successfully fabricated through alkylation technique.The structure,crystallization behavior and thermal stability of PEI18C comb-like polymers with different DS had been systemically characterized by Fourier transform infrared spectroscopy (FTIR),differential scanning calorimetry (DSC),wide-angle X-ray diffraction (WAXD) and thermogravimetric analysis (TGA),and also the effect of DS on the side-chain crystallization and the critical crystallization phenomenon of C18 side groups grafted along PEI backbone were also deeply investigated.The results show that the degree of crystallinity and the number of crystallizable carbon atoms in the C18 side chains of PEI18C comb-like polymers decreased from 54% to 20.3%,and from 11.4 to 4.3,respectively,with the DS decreasing from 47% to 17.6%.In the meantime,the packing mode of confined C18 side groups along PEI molecules display the same manner regardless of the variation of DS,and C18 side groups also take the hexagonally packed structure.The results further demonstrated that the degree of substitution of side alkyl groups or the dispersion density of side groups along polymeric backbones also acts as an important role in the aspect of controlling the side-chain crystallization and the critical crystallization behavior of comb-like polymer,besides the lengthscale of side alkyl chains and the rigidity of polymeric main chains.And,the crystallization behavior and thermal stability of comb-like polymers with different DS are further discussed from the viewpoint of side-chain crystallization.关键词：Comb-like polymer;Polyethyleneimine;Crystallization;Side alkyl groups- 25
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发布时间：2021-03-19 - 摘要：Amino-terminated polydimethylsiloane (SN2) was synthesized by using hydroxyl-terminated polydimethylsiloxane (PDMS) and aminopropyl siloxane coupling agent (DB-912).And the silicone-polyurethane (Si-PU) block copolymer was synthesized by using SN2 as a chain extender and polyurethane prepolymer.The effects of the SN2 and prepolymer of polyurethane feed ratio on the rheological behavior of the copolymer solution in isopropanol (IPA) and the properties of its film were studied in detail.It was found that the Si-PU block copolymer IPA solution with a concentration of 25 wt% exhibited low apparent viscosity and the characteristics of Newtonian fluid within the measuring shear rate scope.During film casting,the SN2 blocks may migrate toward the surface,which led to a surface contact angle to water over 110.With the increasing of SN2 block content,the surface contact angles of films to water increased slightly.When the films were soaked in the water for 24 h,the water absorptions were very low,and the water-repellence was pretty good.The copolymer film showed water absorption lower than 1.5 wt%.With the increasing of SN2 block content,the water absorptions were very low and did not change a lot.However,if the content of SN2 block was too high,the water absorption of films increased obviously owing to the increase of hydrophilic groups (NH2) which possessed good attraction for water molecules.关键词：Polyurethane;Silicone;Block copolymer;Water-repellent
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发布时间：2021-03-19 - 摘要：A novel AB2-type monomer with one azide group and two alkyne groups and two quaternary ammonium salt units was synthesized via highly efficient thiol-yne click chemistry and Menschutkin reaction.The synthetic protocol includes three steps:(1) 4-oxo-4-(prop-2-ynyloxy)butanoic acid 1 reacts with 3-(dimethylamino)-1-propanethiol via thiol-yne click chemistry to obtain intermediate 2 containing one carboxyl group and two dimethyamino groups with high yield (~97.5%),(2) esterification between carboxyl group of 2 and 2-azidoethanol to afford intermediate 3 ,(3) fast click-like Menschutkin quaterization of the two dimethylamino groups of 3 with propargyl bromide to give the final AB2-type monomer 4 possessing one azide group,two alkyne groups and two quaternary ammonium salt units.The monomer structure was confirmed by NMR,FT-IR and MS.The subsequent click polymerization of 4 gave rise to quaternary ammonium salt-type hyperbranched polymers.End-capping the polymers with azide-terminated alkyl long chains resulted in amphiphilic hyperbranched polymers (AHPs) with hydrophilic quaternary ammonium salt core and hydrophobic alkyl shell.The AHPs were characterized by 1H-NMR,FTIR,and gel permeation chromatography (GPC) measurements.The AHPs have number-average molecular weights (Mn) of 3800~5300 and narrow polydispersity index (PDI,1.17~1.27).The host-guest dye-encapsulation property of AHPs was investigated using congo red (CR),methyl orange (MO),methyl violet (MV),methyl blue (MB),eosin Y (EY),fluorescein sodium (FS) and rose Bengal (RB) as guests with UV-Vis spectrometer.The AHPs exhibited high capabilities to load water-soluble dyes due to their polarity difference between core and shell,and the dye-transfer percentage from water to chloroform phase reached 93%~99% for MO,MV,FS,and EY,and 71%~76% for RB and CR.The average numbers of dye molecules trapped per macromolecule achieved 0.5~0.6 for MO,MV,FS,EY and RB,and 4.8 for RB.The polymer-dye complexes were used as additives for coloring common polymers such as SBS and PMMA.The complexes showed excellent dyeing and dispersing effects for both SBS and PMMA membranes because the long aliphatic chains of AHPs could be well compatible with polymer matrix,and the membranes displayed much better transparency as compared with the control samples of dye-coloring resins without AHPs.The color of the membranes with AHPs is very uniform and stable,almost without any dyes releasing from the membranes into water after being immersed in water for a long time (up to several weeks).On the contrary,the control samples released dyes seriously when they are immersed in water for a short time.Our work casts a light for the design of novel,efficient dye-coloring additives,and opens the avenue for the applications of hyperbranched polymers in the field of polymer coloring.关键词：Click polymerization;Hyperbranched polymers;Quaternary ammonium salt;Amphiphilic;Dye-loading;Coloring
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发布时间：2021-03-19 - 摘要：Cross-linked monodisperse polystyrene microspheres were synthesized using one-step method by combining dispersion polymerization with hydrothermal process using styrene as monomer,AIBN as initiator,PVA as stabilizer and ethanol and deionized water as solvent in this paper.The cross-linked monodisperse polystyrene microspheres could be prepared in a large alcohol-water range,even if the crosslinking agent was up to 2 wt%.We focused on the system that the ethanol/water ratio of solvent was fixed at 50/50,to study the effects of stabilizer type and content,organic phase content,initiator concentration and autoclave fill volume on the morphology of the microspheres and size distribution.It was found that the microspheres showed coalescence with decreasing the molecular weight and increasing content of stabilizer.Even without any stabilizers the monodisperse crosslinked PS microspheres could still be prepared when high content crosslink agent was used.The microspheres showed polydispersity gradually with the organic phase increasing.The content of the initiator and the fill volume in the autoclave have little effect on the morphology of the microspheres.And the cause and mechanism of the one-step preparation method of monodisperse crosslinked polystyrene microspheres were also discussed.关键词：Dispersion polymerization;Hydrothermal process;Monodisperse;PS microspheres
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发布时间：2021-03-19 - 摘要：Multi-walled carbon nanotubes (MWCNTs) and hydrophobic nanosilica (SiO2) were used as conductive and nonconductive fillers to fill immiscible poly(methylmethacrylate)/polystyrene (PMMA/PS) (1/1 in volume) blends to prepare (PMMA/SiO2)/(PS/MWCNTs) quaternary conductive polymer composites (CPCs).Conductive percolation at room temperature and melt dynamic rheology of the quaternary CPCs were investigated and were compared with PMMA/(PS/MWCNTs) ternary CPCs containing 5 vol% SiO2.The ternary and the quaternary CPC exhibited similar percolation behavior with percolation threshold of MWCNTs volume fractions much smaller than that of PS/MWCNTs binary CPC.SiO2 particles could reduce the phase size and improve the melt complex modulus without influence the time-dependent dynamic conductive percolation during melt annealing.MWCNTs and SiO2 have different effects on the time-dependent dynamic modulus percolation during annealing of quaternary CPCs.It is believed that MWCNTs and SiO2 accelerated and decelerated the onset time for phase coarsening,respectively,while both significantly extended the time interval of phase coarsening.Morphological observation revealed that degree of phase coarsening decreased with increasing volume fraction of MWCNTs in ternary CPC during melt annealing.The presence of SiO2 could greatly restrain the coarsening in quaternary CPC.关键词：Multi-walled carbon nanotubes;Hydrophobic nanosilica;PMMA/PS blends;Percolation;Dynamic modulus percolation
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发布时间：2021-03-19 - 摘要：Poly(lactid-glycolide acid)/hydroxyapatite (PLGA/HA) materials,as a class of composites,which have good bioactivity,absorbability and biodegradability,show promising applications in biomedical and tissue engineering fields.To improve the compatibility of HA and PLGA,the ring-opening polymerizations of L-lactic acid on three types of HA surfaces with different surface hydroxyl functionality:unmodified HA,HA modified with L-lactic acid,and HA modified with hexamethylene diisocyanate tethered ethylene glycol were carried out to produce poly(L-lactide acid) grafted hydroxyapatite (PLLA-g-HA).The results of FTIR,XPS,TEM and TGA show that PLLA was successfully grafted onto surface of HA by the above three methods.And the grafting rate of PLLA was dependent on the nature and steric environment of the hydroxyl groups on the HA surfaces,among which HA modified with (HMDI+EG) presented the best grafting percentage of 25%.The proportional change between inorganic and organic phase brought about little influence on PLLA grafting rate.The PLLA-g-HA can stably disperse in chloroform over 2 days without deposition.To investigate practicability of the composites used as bone guided regeneration membranes,tensile test after co-electrospinning shows that PLLA-g-HA/ PLAG nanofibrous membrane has better mechanical performance compared to HA/PLGA membrane,and its tensile force reaches maximum at 5% filling content.关键词：Hydroxyapatite;Surface modification;L-lactide;Grafting polymerization
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发布时间：2021-03-19 - 摘要：A new series of amphiphilic diblock liquid crystalline copolymers denoted as PMA6Chol-block-PHEMA were prepared by sequential reversible addition-fragmentation chain transfer polymerization (RAFT) and successive removal of TMS protection groups,and their chemical structures were further characterized by 1H-NMR and GPC.By means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA),thermal properties and liquid crystal phase transitions were characterized for the resultant diblock copolymers,and the presence of hydrophilic PHEMA hydrogen-bond network may be one possible reason of higher TLC-I of diblock copolymers than those of PMA6Chol homopolymers.Through nanoprecipitation in THF/water mixed solutions,the synthesized LC diblock copolymers PMA6Chol-block-PHEMA were found to self-assemble into micron-scale core-shell spherical aggregates,and the rapid kinetically trapping rigid LC PMA6Chol chains may be the reason for self-assembling microscopic spheres at ambient temperatures in THF/water mixed solutions.关键词：Amphiphilic;LC copolymers;Reversible addition fragmentation chain transfer (RAFT);Self-assembly;Nano-precipitation
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发布时间：2021-03-19 - 摘要：The methods of measuring the closed cell content of phenolic foams were studied by densimeter.The system balance times were recorded under different pressures during the measuring processes,and the structural changes were analysed after the measuring processes combined with scanning electron microscopy in order to optimize the measuring pressure.The microstructure of different phenolic foams was characterized by scanning electron microscopy and the relationship between the closed cell content and microstructure of phenolic foams was further discussed.The samples after storing for different time periods underwent constant temperature treatment, and the closed cell content and microstructure of samples before and after treatmeat were compared and analyzed.The results demonstrated that the first prerequisite for obtaining the accurate results was to optimize the measuring condition and pressure for measuring the closed cell content of phenolic foams,the low closed cell content of phenolic foams was resulted from the flaw of foam microstructure (e.g. pinhole and fissure),and the primary cause for the long measuring time due to the balance difficulty was the inhomogeneous cells in the microstructure and different aftertreatment procedures.关键词：Phenolic foam;Closed cell content;Microstructure;Scanning electron microscope (SEM)
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发布时间：2021-03-19 - 摘要：All species in this reaction system were fully optimized at B3LYP/6-31G(d,p) basis set level by using density functional theory,and then single point energy calculations were performed.In succession the hydrolysis and oligomerization mechanisms of Si(OCH3)4 in acidic solutions were investigated systematically to elucidate the competitiveness between hydrolysis and oligomerization.This theoretical model show that:(1) H2O is bonded to precursors via hydrogen bonds or coordination bonds to facilitate hydrolysis;(2) H2O attacks precursors from the opposite side of protonated alkoxy groups;(3) for the fourth-order hydrolysis,H2O expels protonated alkoxy groups from the opposite side,but the precursor does not hydrolyze completely;(4) the hydrolysis products condense via the ring mode,viz. the hydrolysis products are linked together via hydrogen bonds to form polyatomic rings to oligomerize via hydrogen transfer;(5) the precursor Si(OCH3)4 is inclined to hydrolyze than to condense;(6) proton blocks the cationic dimers to cyclize;(7) silicon cation can solicit non-barrier oligomerization,but the ionic reaction channels are energetically unfavorable.关键词：Silicon alkoxides;Hydrolysis;Oligomerization;DFT
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发布时间：2021-03-19 - 摘要：In the present paper cross-linked polyethylene/organic montmorillonite (XLPE/O-MMT) nanocomposites,in which organic montmorillonite (O-MMT) treated by octadecyl ammonium chloride as the inorganic nanophase,low density polyethylene(LDPE) as the matrix polymer,maleic anhydride grafted polyethylene (PEMA) as the compatibilizer and bis(1-(tert-butylperoxy)-1-methylethyl)-benzene (BIPB) as the crosslinking agent,are prepared by means of the two-step method,i.e.after melting intercalation process the cross-linking reaction is carried out chemically.The space charge properties of XLPE/O-MMT nanocomposites with different proportions of O-MMT are investigated by the pulsed electro-acoustic (PEA) method.The test results indicate that XLPE/O-MMT nanocomposites with certain content of O-MMT reveal the ability inhibiting space charge in different degrees compared with XLPE.In XLPE/O-MMT nanocomposites there is the lowest space charge amount when O-MMT content is 0.5 wt%~1 wt% and the space charge amount increases with O-MMT content in the range of 3 wt%~7 wt%,but it is still lower than that of XLPE.It is proved by the thermally stimulated current (TSC) tests that the TSC peak of XLPE/O-MMT nanocomposites shifts to higher temperatures compared with that of XLPE,and it is suggested that the traps depth increases.The area under TSC curve of XLPE/O-MMT nanocomposite with 1 wt% O-MMT is the least,accordingly its traps density is also the lowest; and the areas under TSC curves of XLPE/O-MMT nanocomposites increase with O-MMT content increasing,it means traps density enhancing.The test results of insulation electrical conductivity support the above conceptions further.关键词：Cross-linked polyethylene/organic montmorillonite (XLPE/O-MMT) nanocomposites;Space charge;Thermally stimulated current (TSC);Insulation electrical conductivity
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发布时间：2021-03-19 - 摘要：The acrylic resins containing fluorine/silicone side chains were synthesized by solution copolymerization with 1H,1H,7H-dodecafluoroheptyl methacrylate (FMA),monomethacryloxyalkyl-terminated PDMS (SMA),methyl methacrylate (MMA),n-butyl acrylate (BA),n-butyl methacrylate (BMA) and ethyl acrylate (EA) as the comonomers.A solution of toluene and butyl acetate (weight ratio 1∶1) was initially charged to a 250 mL four-neck flask with a condenser,a nitrogen inlet and a mechanical stirrer.The mixture was then degassed for 15 min and immersed into an oil bath at 85℃ with a slow nitrogen purge.The mixture of FMA,SMA,MMA,BA,BMA,EA and 0.8% azobisisobutyronitrile (AIBN) ( based on the content of the comonomers)was slowly added dropwise over 2 h.0.4% AIBN was slowly added after the reaction was stirred over 1.5 h.The solution was heated to 110℃ and stirred for 2 h.The solid content of copolymer solution was 50%.The as-prepared copolymer was characterized by 1H-NMR,19F-NMR and FTIR.The effects of FMA and SMA content on the properties of polymer coatings were investigated by scanning electron microscopy (SEM) and contact angle analysis.The marine antifouling properties of the materials were evaluated by laboratory assays employing the fouling Sulfate-Reducing bacteria.The results showed the surface energy of fluorine modified acrylic resins and silicone modified acrylic resins were greater than 24 mJ/m2 and 29 mJ/m2,respectively.However,fluorine/silicone synergistically modified acrylic resins had lower surface energy (＜21 mJ/m2) and better anti-biofouling properties than fluorine or silicone-modified acrylic resins and a standard poly(dimethyl siloxane) (PDMS).关键词：Fluorine/silicone modified;Acrylic resin;Radical polymerization;Low surface energy;Anti-biofouling
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发布时间：2021-03-19 - 摘要：The reactive in situ compatibilization of polyvinyl chloride (PVC) and polystyrene (PS) was realized in melt blending through Friedel-Crafts reaction between PVC and PS with anhydrous aluminium chloride as catalyst.The melting temperature of blending PVC and PS decreased from 160℃ to 140℃; Impact toughness of the blends was improved through pre-milling and adding styrene monomer.PVC/PS alloy materials with favorable comprehensive mechanical performance were successfully prepared.The structure and properties of PVC/PS alloy materials were characterized by Fourier transform infrared spectroscopy (FTIR),differential scanning calorimetry (DSC),scanning electron microscopy (SEM) and tests of mechanical properties.The results show that the peaks of 1943 cm-1and 838 cm-1 in FTIR spectrum proves the substitution for para-position of benzene,the glass-transition temperature of the blend is 89℃ between 83℃ of PVC and 106℃ of PS.SEM photos show interface adhesion of PVC with PS became better and better with addition of anhydrous alluminium chloride and styrene in proper order.When the mass fraction of PS,anhydrous alluminium chloride and styrene is 6%,0.6% and 9%,strengthening and toughening of PVC were realized,the tensile strength increased from 49.35 MPa to 60.54 MPa,the notched impact strength of the blends material reached 5.3 kJ/m2,compare with 3.9 kJ/m2 of PVC,increased by 35.9%.关键词：Polyvinyl chloride;Polystyrene;Aluminium chloride;Friedel-Crafts reaction;Reactive in situ compatibilization
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发布时间：2021-03-19
Research Article
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