最新刊期
卷 ， 期 5 ， 1991
- 摘要：The copolymerization of polystyrene macromers with vinyl acetate was studied. The results show that the grafting efficiency increases with amount of initiator, polymerization temperature and charging ratio of vinyl acetate to the macromer, and decreases with increasing average molecular weight of the macromers. There exists a maximum value in the relationship between the grafting efficiency and the total monomers concentration. During copolymerization the conversion rate of the polystyrene macromer is faster than that of vinyl acetate at the beginning while slower at the later stage. The graft copolymers were purified by extractions and charac-terized by GPC,IR,1H-NMR,PGC and TEM.The last indicates a microphase separation in the graft copolymer.
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发布时间：2021-03-19 - 摘要：The blends of poly(vinylidene fluoride) (PVF2) and methyl methacrylate-styrene radom copolymer (MS) of different styrene (St) mol％ were investigated．This paper deals with the crystallization behaviors and mechanical properties of PVF2/MS blends．It was found that while the MS content increases in the blends．the crystallization of PVF2，their melting points and the rates of crystallization decreases，the spherulites and their sizes become imperfect and smaller．The influence of MS-90 (St mol％ is 10) is grea+er than that of MS-80 (St mol％ is 20)． The mechanical properties of PVF2／MS-90 and PVF,／MS-80 are vastly different due to their miscibility．For the miscible system of PVF,／MS-90 as the PVF2 increases to 50％(Wt)，the blends go through the transition from the amorphous to the semi-crystalline and their me-cbanical properties accordingly display discontinuous．For the semi-miscible system of PVF2/MS-80，the blends are brittle when PVF2 is less than 50％，whereas when the content is over 60％，a concerted effect can be observed that heir elongation is vastly greater than that of pure PVF2 while the strength of the blends are much the same as pure PVF2．
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发布时间：2021-03-19 - 摘要：The mechanism of interfacial interaction of nylon-polyethylene blends were studied by the SEM, Molau Test, DSC, IR and ESCA. As a result, the chemical coupling of compatible agent plays an important part in the amelioration of interface combination between two phases and micro-structure morphology of blands.
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发布时间：2021-03-19 - 摘要：The effects of different electron donors such as ethyl benzoate(EB) diisobutyl phthalate (DIBP), 2,2,6,6-tetramethyl piperidine(TMP) and various silanes as internal donor (Din) and external donor(Dex) respectively were investigated.The possible synergistic effect of Din and Dex was discussed.It was found that EB, DIBP, TMP and alkoxysilanes used as Dex could evidently improve the stereospecificity accompanied with a decrease of the activity, while the effects of EB, DIBP and TEM used as Din are quite differet from each other. The effects of increasing the stereospecilicity is due to deactivation of different selectivity for both atactic and isotatic active centers and the deactivation of atacitic active centers is much greater than that of isotactic active centers. Cooperation of appropriate Din and Dex would give good catalytic performance with high activity andhigh stereospectifity.
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发布时间：2021-03-19 - 摘要：The oligomer of poly-4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-l-oxide (PMTMPO.) has been prepared by ester exchange reaction of its precursor oligomer (Mn range from 108-5×103) with 2,2,6,6-tetramethyl-4-hydroxylpiperidine-1-oxide (TMHPO) in presence of megne-sium meth -oxide. Other kind of PMTMPO. was also obtained by controlling polymerization of 4-methacryloyloxy-2, 2, 6, 6-tetramethylpiperidine(MTMP) in petroleum ether and acetic acid. The structure of the resultant stable radical oligomer was characterized by IR.EPR and TGA techniques. The inhibiting effect of PMTMPO for bulk polymerization of acrylic acid,initia-ted by AIBN,at 90℃ has been Studied. The results show that the efficiency of inhibition was found to depend on the concentrations of the nitroxyl radical in PMTMPO.
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发布时间：2021-03-19 - 摘要：Aqueous polymerization of methyl methacrylate initiated by copper chloride-sodium sulfite redox pair was investigated under the close air atmosphere and without shaking. The overall rate of polymerization (RP) isThe covering atmosphere affects the polymerization process markedly. Oxygen retards the polymerization, but it is able to oxidize Cu+ to Cu2+.As a result, it shows the lower overall rate of polymerization, higher collision frequency factor and overall activation energy of polymerization. Mechanism of initiation was proposed and discussed.
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发布时间：2021-03-19 - 摘要：Back potentiometric titration with addition of salt NaCl was used to determine the acid titratable percent in EHA／AA radiation emul sion copolymerized latex．It was found that,he carboxylic monomer concentration，its neutralized percent，its adding model，the emulsifier concentration，the molecular weight of copolymer have significant effects on the acid titra-table percent in polymer latex；while total adsorbed dose and dose rate have no obvious effects．In all cases investigated the acid titratable percent is above 75％，this means that most of the carboxyl groups accumulate in the latex shell of copolymer．Because the solubilitv EHA in water is very low，the micelle nucleation takes advan-rage in emulsion polymerization with EHA as main monomer．When AA concentration in water is high,the homophase nucleation becomes important．After the nucleation period，AA distributes in water and polymer-monomer par ticles by certain proportion．The AA in parti-cles copolymerizes with EHA and distributes homogeneously in polymer latex at last．While AA in water has two reaction routes：the first，diffusion into the particles，it results in that most of AA accumulates in the latex shell and the concentration of carboxyl group has a gra-client along the latex radius；the second，polymerization in water，the resulted polymer is soluble in water or is adsorbed at the latex surfac e．For unneutralized AA，the first mechanism dominates，while for partly preneutralized AA，the second mechanism takes advantage and will compete with the first mechanism for AA in water．
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发布时间：2021-03-19 - 摘要：A method is presented for measuring the composition and molecular weight of block copolymer simultaneously by size exclusion chromatography with a single detector. The method requires intrinsic viscosity and size exclusion chromatographic data on the whole sample and that the detector be responsive only to one of the two monomer units of the block polymer. The response constant and the molecular weight separation curve are first calibrated with homo-polymer standards. The chromatogram of the whole sample is resolved into two peaks cor-responding to homopolymer and block copolymer by peak resolution technique. The composi-tion and the molecular weight of the copolymer are calculated with the aid of the response constant and universal calibration principle. The utility of the method is illustrated using a series of styrene-dimethylsiloxane block copolymer samples on a conventional SEC unit with a differential refractometer as detector.
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发布时间：2021-03-19 - 摘要：Crystallization behavior of undrawn and hot drawm PET film with random orientation in chain segments and high orientation in the global sense has been compared using SAXS and WAXD. As compared with undrawn PET film, the hot drawn PET film showed shorter crystallization induction period, faster development of long period, anisotropic in SAXS and WAXD patterns, with considerable thermal contraction along the direction of drawing and small lengthening in the direction of drawing during crystallization.
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发布时间：2021-03-19 - 摘要：SBS molecules can micellize in methylethyl ketone (MEK) under certain conditions. But the behavior of micellization was found to be instable. In this paper, GPC,IR, ultracentrifuga-tion and viscometry were used to study the instability. It was pointed out that SBS molecules were degradated in MEK solvent when solution was stored in air for a long time. The reason is that ketone is easy to yield free radicals by ultra-violet ray and the free radicals accelerate oxidation and degradation of double bond C=C of PB block in the SBS molecules.
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发布时间：2021-03-19 - 摘要：Simulation of chain propagation process of binery polymerization reaction with Monte-Carlo method and statistical probability treatment of estimating kinetic parameters were made. From statistical point of view, this is a Bayesian one in which a posterior probability density surface(PPDS) is calculated for points on a grid in the parameter space. A smoothing function is fitted to the PPDS, then reactivity ratios (r1,r2) are calculated for confidence region. When this method was used to estimate reactivity ratios of styrene-butyl acrylate copolymer,it was in good agreement with that obtained by normal calculating kinetic parameter methed.
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发布时间：2021-03-19 - 摘要：Thread texture (including tight and coase thread), Schlieren texture, marble texture and so on, which were similar to those of small molecular nematic liquid crystallines, were all obtained from one aromatic copolyester B-N.Because the distribution of molecular director was not affected by lamellar decorating after quench, chemical etching and SEM technique were used to reveal disclination and director patterns. The results of electron and optical microscopy complemented each other, showing different trajectory of director between tight and coase th-read texture which were regarded as two completeoly different types of texture. The coasening process starred from the second melting peak temperature Some evidences of S= +/-- 1/2 and S= +1 disclinations and Neel domain wall were found in these nematic textures.
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发布时间：2021-03-19 - 摘要：A kinetic study of copolymerization of styrene and ff-methylstyrene initiated by n-butylli-thium in cyclohexane with tetrahydrofuran as a polar additive has been carried out. Through the investigation of kinetics and mechanism of copolymerization in the presence of multiple active species accompanied with depropagation, the propagation rate constants and depropaga-tion rate constants of the two monomers with regard to different species as well as the cotn-plexation equilibrium constants between various type of active species were obtained.
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发布时间：2021-03-19 - 摘要：A kinetic approach to phase transition of liquid crystalline polymers was deduced. On the basis of physical chemistry, a kinetic equation concerned the phase transition of liquid crystalline polymers was established, and a new kinetic parameter of transition order was proposed. Hence the quantitative determination of the order of phase transition was obtained. In addition, the kinetic approach was applied to a new series of polymer systems, and the kinetic order of phase transition of the polymers was decid. It is concluded that the clearing transition is of first order,and the smectic-smectic tran-sition second order,while the order of melting and solid-solid transition varies with the poly-mer structure.
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发布时间：2021-03-19
Research Article
- 摘要：In this work,ESCA and SEM have been used to characterize the surface and bulk micro-phase morphology, surface chemical composition and the composition of polyether soft segment and TDI-HEMA hard segment based on two TDI-HEMA-PPO types of UV cured polyuretha-ne acrylates. The experimental results show that: (1) the microphase morphology of UV cured polyurethane acrylates strongly relies on the composition of soft and hard segments. Increasing the content of polyether soft segment, the extent of microphase seperation increased; (2) the sur-face elemenal composition is different from the bulk elemental composition; (3)
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发布时间：2021-03-19 - 摘要：The conjugative poly(1,4-butynediol) (PBD) was synthesized using Mods, Cd(NO3)2. 4H2O and (Ph3P)2PdCl2 catalysts respectively. The behaviours of copolymerization of pheny-lacetylene (PA) and butynediol (BD) were investigated by (Ph3P)2PdCl2 catalyst. When PA/ BD≥1 (mole ratio), the copolymers are soluble and fusible. When PA/BD=1, the copolymers obtained can be separated into two coponents, one is soluble and fusible, another insoluble and infusible. When PA/BD≤1, the copolymers are insoluble and infusible. According to IR spectra of homopolymers and copolymers,the metathesis catalysis mechanism was proposed.
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发布时间：2021-03-19 - 摘要：The kinetics of group transfer polymerization of methyl methacrylate with 1-trimethylsi-loxy cyclohexene (TSCH) as initiator and tetrabutylammonium bibenzoate(TBABB) as catalyst was investigated. The dependence of the polymerization on the catalyst initiator ratio has been investigated, the ultimate conversion decreased when the ratio > 0.3. The apparent activation energy of polymerization and polymerization rate equation were determined. It was shown that the propagation reaction is of first order with respect to catalyst concentration and 1.25 with respect to MMA concentration and 0.38 with respect to initiator concentration respectively.
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发布时间：2021-03-19 - 摘要：Benzoyl peroxide (BPO) was used for initiator in copolymerization of dibutyltin maleate (DBTM, M2) with methyl acrylate (MA, M1) in benzene and the reactivity ratios of copolymerization r1 and r2 were found to be 12.67 and 0.03, respectively. But in copolymerization of DBTM (M2) with butyl acrylate (BA, M1) r1 and r2 were 11.1 and 0> respectively. The cc-polymerization conditions, such as amount of initiator, ratios of monomers and addition method of initiator were examined. Copolymers were characterized by 1H-NMR,IR,elemental and TG analyses. MA-DBTM copolymer is a white and brittle solid, while BA-DBTM copolymer is a transparent elastomer at room temperature.
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发布时间：2021-03-19 - 摘要：[Li(2.5D)] [Y(π-C3H5)4] was used as a catalyst for isoprene polymerization giving 57.9% cis-1,4 polyisoprene with high activity. The result of 13C-NMR study on the polymer shows that the terminal chains are -CH2-CH = CH1 which indicates that the insertion reaction of monomer occured between belween yttrium and π-allyl. The result above is the first direct evidence for the π-alyl mechenism of diene polymerization with rare earth coordination catalysts.
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发布时间：2021-03-19 - 摘要：The thermal properties,crystallization characteristics and mechanical properties of blend of Nylon-6 with PPTA were investigated. It is indicated that the obvious effects on Tg and rate of crystallization of Nylon-6 were observed by the addition of small amount of PPTA, and some mechanical properties of Nylon-6 are also improved.
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发布时间：2021-03-19
Research Bulletin
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