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研制不同组分的载体钛系高效催化剂,考察在不同聚合条件及外加芳酯的情况下对1-丁烯聚合的影响。用催化剂TiCl_4,Ti(OBu)_4/φ_2SiCI_2/苯甲酸乙酯(EB)/MSCl_2/AlEt_3进行1-丁烯聚合具有高的催化活性(3.2×10~4g·PB/g·Ti·h),外加对-甲基苯甲酸乙酯时可提高聚合物等规度(Ⅰ.Ⅰ%=93.3),分子量可用H_2调节。衰减聚合反应的动力学方程为R_1=R_5+(R_0-R_5)e~(βt)。用DSC、WAXD和~(13)C-NMR等方法表征聚合物。 相似文献
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研究了笼形聚羧酸钒(PV)-硫脲(TU)体系在硝酸溶液中引发丙烯腈(AN)聚合动力学。表观聚合速度(R_p)是 R_p=9.7×10~5e~(-10500)/RT[AN]~1.0[PV]~0.50[TU]~0.76[HNO_3]~1.5聚合诱导期(τ)随反应条件而变化,聚合温度越高,引发种浓度越大,聚合诱导期越短,但与单体浓度的变化无关。 1/τ=4.6×10~(12)e~(-13500)/RT[AN]~0[PV][TU]~(-3/2)[HNO_3]~3=K_τ·R_i聚合物分子量随单体浓度增大而提高,但随聚合温度及引发种浓度增大而下降,即 笼形聚羧酸钒—硫脲体系引发丙烯腈聚合的动力学参数和引发机理与杨梅型聚羧酸钒—硫脲体系在相同的条件下引发聚合的行为有明显的区别,认为是和两种树脂大分子链的空间结构所引起的传质阻力有关。 相似文献
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聚(苯乙烯-丙烯酸)-氯化铜配合物催化引发丙烯腈聚合的研究 总被引:1,自引:2,他引:1
将聚(苯乙烯-丙烯酸)(PSAA)(Mw=3500)与氯化铜在异丙醇溶液中反应得到一种配位聚合物膜聚(苯乙烯-丙烯酸)-氯化铜(PSAA-Cu(Ⅱ)).研究丙烯腈(AN)在该配位聚合物膜、HSO3-和水体系(温度为55℃)催化引发作用下的聚合反应历程.AN在上述的催化引发体系中是按照自由基加聚反应历程进行聚合的,PSAA-Cu(Ⅱ)在催化引发体系中起着催化剂的配位催化作用.讨论了温度、Na2SO3浓度、AN浓度和PSAA-Cu(Ⅱ)膜用量对聚合速率、诱导时间的影响.实验结果表明,配合物PSAA-Cu(Ⅱ)膜催化引发AN聚合的诱导期为128s,反应24h后PAN产率为75.6%,Mw=2.18×104和Mn=1.12×104,多分散性系数为1.95. 相似文献
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在1-丁基-3-甲基咪唑四氟硼酸盐离子液体中以氯化苄为引发剂,氯化亚铜/2,2’-联吡啶为催化剂成功实现了丙烯酰胺的原子转移自由基聚合(ATRP)。用IR对聚合物的结构进行了表征,证实聚合物链端具有-Cl端基。考察了引发剂用量、催化剂和配体用量、单体用量和反应时间等因素对丙烯酰胺在离子液体中的原子转移自由基聚合的影响,结果表明,反应时间为1.5 h时转化率达到31.43%,MnGPC=4451,Mw/Mn=1.38。且80 ℃下丙烯酰胺在离子液体中的最佳聚合工艺条件为:单体浓度3 mol/L,引发剂浓度0.010 mol/L,催化剂浓度0.015 mol/L,反应时间1 h。 相似文献
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Cu~(2+)-Na_2SO_3体系引发甲基丙烯酸甲酯聚合动力学 总被引:3,自引:1,他引:3
研究了Gu~(2+)-Na_2SO_3氧化还原体系在静置的密闭空气气氛下引发甲基丙烯酸甲酯水溶液聚合。表观聚合速度(R_p)是 R_p=1.86×10~(15)e~(-24,200/RT)[MMA]~(1·0)[Cu~(2+)]~0[Na_2SO_]~(0·50)覆盖气氛对聚合有显著影响。氧抑制聚合反应,但可使Gu~(2+)离子氧化再生。表现为低的表观聚合速度和高的碰撞频率因子与表现聚合活化能。 本文讨论了引发聚合机理。 相似文献
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研究了聚丙烯基聚肟偕氮合铜(Ⅱ)(PPAO—Cu)—亚硫酸钠体系引发甲基丙烯酸甲酯(MMA)水溶液聚合。表观聚合速度(Rp)是 Rp=9.7×10~(12)e~(88.8kJ/RT) c(MMA)~(0.88) c(Na_2SO_3)~(0.50) 聚合诱导期(τ)与亚硫酸钠浓度成反比,与PPAO—Cu用量和单体浓度无关。可表示为 1/τ=1.2×10~(12)e~(-55.3KJ/R) c(Na_2SO_3)=K_τ·R_ 聚合是由PPAO—Cu/Na_2SO_3氧化还原反应产生的初级自由基所引发。 相似文献
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应用稀土化合物:环烷酸钕Nd(naph)_3和二(2-乙基己基)磷酸钕Nd·(P_(204)_3分别与三异丁基铝Al(i-Bu)_3组成络合催化剂引发苯乙烯均聚及其与二乙烯苯共聚。适宜的聚合温度为50℃:[Nd]=3×10~(-5)mol/ml;[M]=3×10~(-3)mol/ml;Al/Nd=10(摩尔比),并且催化剂按以下次序配制:钕化合物→溶剂→苯乙烯→三异丁基铝,苯乙烯的转化率在90%以上。溶剂种类及聚合条件不同,制得的聚苯乙烯可为白色或黄色粉末状无定形聚合物,分子量几百至上万。聚合体系中添加PeCl_3能抑制黄色产生。在共聚反应中,二乙烯苯比苯乙烯显示较高的反应活性。 相似文献
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SiO2负载的后过渡金属配合物/三乙基铝催化乙烯聚合研究 总被引:5,自引:0,他引:5
将后过渡金属配合物{[2,6-ArN=C(Me)2C5H3N]FeCl2} ( Ar=2,6-iPr2C6H3) Ⅰ负载于SiO2上, 并与三乙基铝(AlEt3)组成催化剂体系并催化乙烯聚合. 考察了Al/Fe比(AlEt3/催化剂摩尔比)、聚合温度对催化剂活性、聚乙烯(PE)分子量、熔融温度以及结晶度的影响. 在Al/Fe比为750、聚合温度为40 ℃时, 催化剂活性达到7.07×105g PE·(mol Fe·h)-1. 实验所得聚合物的分子量为1.05×105~2.33×105 g/mol, 熔融温度高达132 ℃左右,结晶度在44.2%~77.8%之间. 相似文献
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在浓硫酸或稀硫酸中聚合得到了高分子量P2VP,~(13)C-NMR谱确定其为无规聚合物。特性粘数(切变速度D=0)与分子量之间的关系为[η]_(D=0)=1.27×10~(-2)(?)_W~(0.70)(在DMF中,25℃,(?)_W=2.66×10~6—10.0×10~6)。在DMF中,25℃,不依赖于切变速度的最大特性粘数为260毫升·克~(-1),相应的分子量M_η=1.74×10~6左右。无扰尺寸(_0/M)=6.08×10~(-18)厘米~2·克~(-1),在DMF 中B参数为1.91×10~(-27)厘米~3。 相似文献
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研究了硝酸溶液中聚丙烯基聚偕氨肟(PPAO)—硫脲(TU)络合物引发丙烯腈(AN)聚合动力学。在[TU]/[PPAO]<0.5摩尔比的条件下,表观聚合速度(R_p)是R_p=9.1×10~4e~(-45.2k J/RT)[AN]~(2.0)[HNO_3]~(1.5)[TU]~(1.0)聚合物分子量随聚合温度升高而下降,并与硝酸浓度的1.5次方和硫脲浓度的1.0次方成反比,与丙烯腈浓度和 PPAO 浓度无关。可表示为_m=K·1/T·(1/[HNO_3]~(1.5)[TU]~(1.0))=K_M·1/T·(R_p/R_t)根据实验结果,提出了“络合—质子转移”引发机理。 相似文献
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Preparation of ultra high molecular weight amorphous poly(1‐hexene) by a Ziegler–Natta catalyst
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Saeid Ahmadjo 《先进技术聚合物》2016,27(11):1523-1529
High molecular weight polymers such as poly (α‐olefin)s play a key role as drag‐reducing agents which are commonly used in pipeline industry. Heterogeneous Ziegler–Natta catalyst system of MgCl2.nEtOH/TiCl4/donor was prepared using a spherical MgCl2 support and utilized in synthesis of poly(1‐hexene)s with a viscosity average molecular weight (Mv) up to 3.5 × 103 kDa. The influence of effective parameters including Al/Ti ratio, polymerization temperature, monomer concentration, effect of alkylaluminus type on the productivity, and molecular weight of the products was evaluated. It was suggested that the reactivity of the Al‐R group and the bulkiness of the cocatalyst were correlated to the performance of the Ziegler–Natta catalyst at different polymerization time and temperatures, affecting the catalyst activity and Mv of polymers. Moreover, bulk polymerization method leads to higher viscosity average molecular weights, revealing the remarkable effect of polymerization method on the chain microstructure. Fourier transform infrared, 13C Nuclear magnetic resonance spectra, and DSC thermogram of the prepared polymers confirmed the formation of poly(1‐hexene). The properties of the polymers measured by vortex test showed that these polymers could be used as a drag‐reducing agent. Drag‐reducing behaviors of the polymers exhibited a dependence on the Mv of the obtained polymers that was changed by variation in polymerization parameters. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Sasithorn Kongruang Myung Joo Han Claudia Isela Gil Breton Michael H. Penner 《Applied biochemistry and biotechnology》2004,113(1-3):213-231
Methods for the quantification of total and accessible reducing ends on traditional cellulose substrates have been evaluated
because of their relevance to enzyme-catalyzed cellulose saccharification. For example, quantification of accessible reducing
ends is likely to be the most direct measure of substrate concentration for the exo-acting, reducing end-preferring cellobiohydrolases.
Two colorimetric assays (dinitrosalicylic acid [DNS] and bicinchoninic acid [BCA] assay) and a radioisotope approach (NaB3H4 labeling) were evaluated for this application. Cellulose substrates included microcrystalline celluloses, bacterial celluloses,
and filter paper. Estimates of the number of reducing ends per unit mass cellulose were found to be dependent on the assay
system (i.e. the DNS and BCA assays gave strikingly different results). DNS-based values were several-fold higher than those
obtained using the BCA assay, with fold-differences being substrate specific. Sodium borohydride reduction of celluloses,
using cold or radiolabeled reagent under relatively mild conditions, was used to assess the number of surface (solvent-accessible)
reducing ends. The results indicate that 30–40% of the reducing ends on traditional cellulose substrates are not solvent accessible;
that is, they are buried in the interior of cellulose structures and thus not available to exo-acting enzymes. 相似文献
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碘是人体的必要元素 ,但碘的摄取量偏高或偏低同样对人体造成严重的伤害 [1]。现已查明 [1] ,我国山东、山西、河北、新疆等省 (区 )的十几个县均存在水源性高碘问题。以地处渤海岸边的山东无棣县为例 ,为了解决群众的吃水难问题 ,当地政府实施了“利民工程”,1 998年共打深机井 50多眼 ,但是 ,经检测 ,其中 90 %以上的机井水除了含氟量超标 (一般在 2 .0 mg/L左右 ,最高可达 3.8mg/L )外 ,含碘量也严重超标 ,一般均达到了1 0 0 0 μg/L左右 ,有的甚至高达 2 0 0 0 μg/L,大大超过国家建议的 1 0~ 1 2 5μg/L的标准含碘量。目前 ,有关高… 相似文献
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Zhi-Gang Feng 《Journal of Dispersion Science and Technology》2013,34(7):968-974
The hydrodynamics of a sphere with interface slip has been numerically investigated for flows of Reynolds number ranging 0 < Re ≤ 75. A simple correlation of the drag force coefficient in the present of interface slip has been derived based on our numerical simulations. The correlation takes the slip coefficient and Reynolds number as two input parameters. By comparing results found in the literature, we believe that the present correlation is more accurate; it provides a source for future experiment study and for numerical simulations of large multi-particle system where the interface slip is important. 相似文献
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