最新刊期
卷 ， 期 4 ， 1981
- 摘要：A mechanism of grain formation in vinyl chloride suspension polymerization is proposed. By agitation, the liquid vinyl chloride is suspended in water as small droplets (the diameters of the small droplets are about 1 μ) in which the polymerization takes place. The small droplets agglomerated to the grains (the dianeters of the grains are about 100 μ) at about 25% conversion.Correctness of the mechanism is proved by using electron micrograph and by adopting reference data of specific surface of the resin.
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发布时间：2021-03-19 - 摘要：In addition to the aa and β relaxation amorphous samples show a dielectric maximum at 120-130℃ due to the crystallization of the sample during temperature scanning. A dielectric method of characterizing the process of isothermal crystallization of PET in the temperature range of 97-113℃ has been demonstrated. During the primary stage of crystallization the change of e' with time obeys the Avrami equation, that is, ε'(t)- ε'(∞)/ε'(0)-ε'(∞) =" exp(-Ktn) with n - 2 in the temperature range studied. During secondary stage of crystallization the dielectric relaxation strength △ε determined from the Cole-Cole plote decreases while the Cole-Cole β parameter increases in the course of crystallization.
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发布时间：2021-03-19 - 摘要：The elastic recovery of polyester-polyether fiber at lower temperature was studied. It was found that due to the stress-induced crystallization of soft segments the fiber has a relative low elastic recovery at lower temperature but higher extention ratio. The probable routes of improvements have also been discussed.
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发布时间：2021-03-19 - 摘要：The emulsion polymerization of octamethylcyclotetrasiloxane in the presence of do-decyldimethylbenzyl ammonium halide and various alkalies were studied. The polymerization proceeds in two steps, the openning of D4 with formation of OH-ended poly-dimethylsiloxanes and the condensation of the latter. At the end of the reactions equilibriums are established between OH-ended-polydimethylsioxanes of various molecular weights, and also between OH-ended polysiloxanes and cyclosiloxanes. In equilibrium the OH-ended polysiloxanes amouts to about 87%.
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发布时间：2021-03-19 - 摘要：The tonelli's r effect and Flory's rotational isomeric state model of polypropylene is employed to calculate the 13C-NMR chemical shifts of methyl carbon in the various ste-reoisomers of atactic polypropylene. The correspondence between calculated and observed chemical shifts difference is close. Some controversial assignments of resonance peaks in literature are discussed.
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发布时间：2021-03-19 - 摘要：The polydimethyisiloxane with a very narrow molecular weight distribution and free of macrocyclics was synthesized by polymerization of hexamethyleyclotrisloxane (D3) in toluene with benzyltrimethylammonium bis (o-phenylenedioxy) phenylsiliconate as a catalyst and dlmethyl sulfoxide (DMSO) as a promoter．Oxygen must be excluded，otherwise it WOuld lower the reactivity of the catalyst．As oxygen is removed from the reaction system，the rate of the polymerization is obviously increased and D3 can be con-verted to polymer approximately to 100 percent．The polydlmethylsiloxane thus obtain-ed is a living polymer．Characteristics of the nonequilibrium polymerization of D3 in the absence of oxygen were investigated．
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发布时间：2021-03-19 - 摘要：The compositions and the microstructures of styrene (S)-4-Methacryloyloxy-2.2.6.6-tetramethylpiperine (M) copolymers initiated with free radical have been studied by 250 MHz1H-NMR spectra and M-centred triad distributions were quantitatively measured. It is confirmed from the above results that this copolymerization system belongs to the first order Markov chain model. The corresponding reactivity ratios established are rM=0.32, rs=0.60, respectively. The S-centred triad distrbutions for the copolymers rich in styrene were also quantitatively estimated. The observed S-centred triad fractions agree very well with those calculated theoretically.
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发布时间：2021-03-19 - 摘要：A novel vulcanization system for curing silicone rubber by Diels-Alder reaction has been suggested. Some cyclopentadienyl silanes or siloxanes such as were used as efficient crosslinking agent for vulcanization of polysiloxanes having vinyl groups. Compounds III IV could also be used as hardening agents though each had only one cyclopentadienyl group. It might, probably be that the alkoxysilanes first reacted with the silanols on the surface of the filler (SiOs) to form polycyclopentadienyl compounds the latters then crosslinked with the vinyl groups leading to vulcanization of polysilo-xanes. The resulting elastomers possessed higher tensile strength,tear strength and elongation Attempts to cure silicome rubber with compounds.
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发布时间：2021-03-19 - 摘要：A poly [4一(4’-octamethyltctrasiloxanyl) diphynylether] alternating eopolymer prepared by bulk polymerization，has been fraetionated by repeated precipitation method．All fractions together with unfractionated sample have been characterized by viseometry，dynamic osmometry，light scattering and GPC．After correction for polydispersity，a monodispersed [n]～M relationship has been obtained：For the copolymer in THF，The second virial coefficient A2 decreases as the mole-cular weight increases．The relationship is：We found that degradation oceured to some extent when the eopolymer was heated then kept for a few days in water．The results of investigation by UV and IR have shown that the chemical composition of the copolymer has not changed noticeably during deg-radation．
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发布时间：2021-03-19 - 摘要：The moleeuar motions of eopolymers of tetrafluoroethylene and perfluoro-4-methyl-3.6-oxa-△7-octyl．sulfonyl fluoride have been determined from --150℃ --80℃ using vibrating reed device．The materials are partly crystalline perfluorinated copolymers containing different amount of side ehains．Four relaxations are observed，labeled a，y1，γ2，and γ3 in order of decreasing temperature．The α-relaxation (room temperature) is assigned to the glass transition，γ1-relaxation (--50℃，215Hz) to hindered motion of main chains，γ2-relaxation( --60℃，230Hz) to side chain motions．The γ3-relaxation (--77℃，260Hz) is assigned to short segments of main chains (CF2)x motions and its intensity increases with annealing．
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发布时间：2021-03-19
Research Article
- 摘要：The Kinetics of solution polymerization of acrylamide with K2S2O3-Na2SO3, (NH4)2S2O3-Na2SO3, and K2S2O3-NaHSO3 redox initiator systems were studied. It was found that the initial polymerization rates were influenced enormously by the pH values of the solution and the maximum values of the rates of polymerization initiated by K2S2O3-Na2SO3, and K2S2O3-NaHSO3 appeard at pH-3 or pH-6.7 respectively. It was believed that the HSO3- ion must be the main form of the reducing agent used in the above-mentioned redox initiator systems that takes part in the reaction.
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发布时间：2021-03-19 - 摘要：This paper presents a study on the effect of segment compatibility on the compositional homogeneity of polyester-polyether block copolymers. A series of such block co-polymers with various segment structures were synthesized. A transparency point determination was developed as a relative semi-quantitative comparison of segment compatibility in the melt copolyeondensation.
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发布时间：2021-03-19 - 摘要：The radical polymerization of a well known functional monomer with hydroxy group such as 2-hydroxyethyl methacrylate (HEMA) in aqueous solution initiated with potas-sium persulfate (KPS) was studied．The polymerization rate and percentage of conver-sion increased as the concentration of KPS increased．Kinetic studies of aqueous solution polmerization of HEMA using [KPS]=2.4×10-3 mol/l was made under different tern-peratures within the range of 35—50℃．and the overall activation energy of polymeriza-tion E．of HEMA using KPS as initiator was evaluated to be 33 Keal／mol (138 KJ／mol)．It was found that the amount of NaSCN played an important role on the peroxide ini．tiated aqueous solution polymerization of HEMA．When the concentration of KPS and H2O2 were equal to 2.4×10-3 and 3.0×10-2 mol/l respectively，NaSCN would act as activator within the range of [NaSCN]/[KPS]=1—10，or [NaSCN]/[H2O2]：0.007—0.7，when these molar ratios increased then NaSCN WOuld always show its inhibition or re-tardation effect and would lower the percentage of conversion． In the case of TBH．NaSCN would act as activator and increase the percentage of conversion．
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发布时间：2021-03-19 - 摘要：By comparison of the activity of several lanthanide catalysts for stereospecific polymerization of isoprene it was found that NdCl3EtOH-AlR3 system is the most active one. Its polymerization activation energy for butadiene is the least.. The result was explained.
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发布时间：2021-03-19
Research Bulletin
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