NaHSO_3-(NH_4)_2S_2O_8引发体系制备低相对分子质量聚丙烯酸钠

以丙烯酸和氢氧化钠为原料,NaHSO3-(NH4)2S2O8为氧化还原引发剂体系,NaHSO3为链转移剂合成低相对分子质量聚丙烯酸钠。研究了单体、引发剂及链转移剂的用量、反应温度和反应时间等对产物相对分子质量的影响。结果表明,反应温度为60℃、w(单体)=25%、w(引发剂)=0.6%、w(链转移剂)=2.0%、反应时间2h,可制得聚丙烯酸钠的粘均相对分子质量在2 000~3 000,单体转化率在98%以上。     

减少DMC催化合成聚醚多元醇中高相对分子质量拖尾部分的研究

以双金属氰化物络合物(DMC)为催化剂,采用间歇法合成了聚醚多元醇,讨论了催化剂用量、反应温度、反应压力等因素对聚醚多元醇相对分子质量分布的影响。结果表明,硫酸质量分数为总量的0.004%、环氧丙烷预投量为起始聚醚质量分数的16%、DMC催化剂质量分数为总量的0.006%、反应温度在120～130℃和反应压力为0.1 MPa时,所制备的聚醚多元醇中高相对分子质量拖尾部分减少,相对分子质量分布窄,且其它物理性能也较好。     

干法纺丝用UHMWPE的性能剖析

从相对分子质量、颗粒分布、热分析和溶胀溶解等方面对干法纺丝用超高相对分子质量聚乙烯(UHMWPE)的性能进行分析,探讨了各因素对干法纺丝UHMWPE纤维的影响。结果表明:相对分子质量是决定UHMWPE纤维质量的关键因素,应控制在(4~5)×106;UHMWPE粒径小及分布窄,可加快纺丝溶解溶胀;当UHMWPE的相对分子质量接近时,其初始结晶度越高,纤维性能越好。     

均相钕系催化剂合成窄相对分子质量分布的高顺式-1，4-聚丁二烯

考察了由Nd(vers),(简称Nd)、Al(i-Bu)2H(简称Al)争Al(i-Bu)2Cl(简称Cl)组成的均相催化剂体系在5L釜中于70℃聚合丁二烯的反应规律,并在2m3装置上进行了放大试验.结果表明,该均相钕系催化剂具有高的稳定性;Al/Nd(摩尔比)是影响相对分子质量分布的重要因素,当Al/Nd低于20时,产物的相对分子质量分布在3.00以下;改变Nd/Bd(摩尔比)或使用不同组成的Al,可改变聚合产物的门尼黏度,但对相对分子质量分布无明显影响.在2m3装置上,采用均相钕系催化荆可以得到收率大于90%、相对分子质量分布小于3.00和顺式-1,4-结构摩尔分敷大于97.0%的聚丁二烯.     

正性光致抗蚀剂用酚醛树脂的制备

采用4-甲基苯酚、3-甲基苯酚与甲醛,经两步法反应制备了一系列正性光致抗蚀剂用酚醛树脂。制备的酚醛树脂的重均相对分子质量及相对分子质量分布分别在(5～17)×10~3和2.75～11.67范围内。探讨了甲醛用量、反应时间、催化剂用量、水选对相对分子质量及相对分子质量分布的影响。增加甲醛和催化剂用量将使相对分子质量增大、相对分子质量分布变宽。延长反应时间也将使相对分子质量分布变宽。但增加水洗次数将使相对分子质量减小、相对分子质量分布变窄。结果表明,通过改变反应条件可有效地控制酚醛树脂的相对分子质量及相对分子质量分布。     

聚己内酯多元醇的合成与表征

分别以乙二醇、三羟甲基丙烷和季戊四醇为起始剂,经ε-己内酯开环聚合制备了一系列聚己内酯多元醇。探讨了反应温度、时间和催化剂等因素对合成反应的影响,并采用红外光谱(FTIR)、羟值滴定、凝胶渗透色谱(GPC)对聚己内酯多元醇进行了表征。结果表明,以无水乙酸锌为催化剂,且用量为己内酯单体摩尔分数的0.2%,在温度120℃条件下反应3~4 h,制备的多元醇为理想的聚己内酯多元醇,相对分子质量与设计值一致,而且具有相对分子质量分布窄、成本低的特点。     

低相对分子质量聚丙烯酸钠的合成研究

以过硫酸铵-亚硫酸氢钠为氧化还原引发体系、亚硫酸氢钠同时作链转移剂合成低相对分子质量的聚丙烯酸钠。研究了单体、引发剂及连转移剂的用量、反应温度和反应时间等对产物相对分子质量的影响。结果表明反应温度为75℃、单体用量25%～30%(质量分数,下同)、引发剂用量0.40%～0.60%、链转移剂用量4.0%～5.0%、反应时间6.0h时,可制得聚丙烯酸钠的粘均相对分子质量在2000～3000之间,单体转化率为95%以上。     

相对分子质量分布对静电纺丝PA6纤维直径的相关性研究

聚合物原料的相对分子质量及其分布直接影响其静电纺丝纤维直径的大小及分布。选用不同相对分子质量的PA6,通过共混获得不同相对分子质量分布的PA6溶液,通过静电纺丝得到PA6纤维毡,并研究了静电纺丝成形中所得PA6纤维直径及其分布与其相对分子质量及其分布的关系。结果表明:PA6的相对分子质量分布曲线和所获得纤维直径分布曲线相似,宽的相对分子质量分布导致静电纺丝纤维直径分布更宽;对于不同浓度的PA6溶液,PA6相对分子质量增大,纺丝溶液黏度增大,溶液浓度增大,其黏度也增大;PA6相对分子质量分布与其纤维直径分布有一定的相关性。     

阴离子淤浆聚合尼龙6的性能研究

通过阴离子淤浆聚合方法,以氢氧化钠为催化剂、异氰酸酯作活化剂,以惰性脂肪烃为分散剂,在不同的反应时间和140～150℃温度下,制得了不同相对分子质量的尼龙6,最高相对粘度17．5。通过熔融纺丝,获得了可纺性良好的纤维,其断裂强度5．0～6．9 cN／dtex。X衍射测试分析表明,同阴离子本体聚合尼龙6(MC尼龙6)和高粘度尼龙6比较,阴离子淤浆聚合尼龙6在二次成型中更易于生成轫性较好的γ晶型,具有更高的冲击强度。     

超临界CO_2中合成的聚丙烯腈的相对分子质量及其分布研究

用凝胶渗透色谱法测试了超临界CO_2下合成的聚丙烯腈的相对分子质量及其分布,并详细研究了各种反应条件如:单体浓度、引发剂浓度、时间及CO_2压力对聚丙烯腈的相对分子质量、相对分子质量分布及转化率的影响。     

聚砜酰胺的半连续化聚合研究

聚砜酰胺纤维是耐热性能优异的耐高温纤维。在间歇式聚合的基础上,选用双螺杆挤出机作为反应器,对聚砜酰胺进行了半连续化聚合的研究。研究表明:与间歇式聚合相比,采用双螺杆挤出机进行半连续化聚合可以大大加快反应完成的速度,同时还容易制得相对分子质量较高的聚合物。     

双螺杆反应器制备高分子量聚乳酸的研究

利用双螺杆挤出机将低分子量的乳酸预聚物在挤出机上进一步缩聚,制备出较高分子量的聚乳酸.研究了反应挤出温度、催化剂用量及螺杆转速等因素对该缩聚反应的影响.结果表明,当反应温度为160℃,催化剂用量为0.5％,螺杆转速为30 r/min时,聚乳酸的分子量能得到最大程度的提高.     

Evolution of peroxide‐induced thermomechanical degradation of polypropylene along the extruder

An experimental study of the peroxide‐induced degradation of polypropylene in a corotating twin‐screw extruder, operating under various conditions, was reported. Runs were performed without and with peroxide in different concentrations. The evolution of the chemical reactions along the extruder was characterized by on‐line rheological measurements and by determination of the molecular weight of samples collected at the same locations. The results evidenced the relationships between peroxide concentration and processing conditions with rheological properties and molecular structure of the modified materials. The concept of chain‐scission distribution function elucidated the mechanisms involved in the thermomechanical degradation of PP, which is by chain scission and is dependent on the level of stress imposed by the screw elements, temperature, and concentration of hydrogen‐abstracting agents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:2711–2720, 2004     

半连续化直接缩聚法制备聚对苯二甲酰对苯二胺浆粕

采用啮合同向旋转的双螺杆挤出机作为主反应器,半连续化直接缩聚法制备了聚对苯二甲酰对苯二胺（PPTA）浆粕.结果发现,较低的预缩聚反应温度有利于得到高相对分子质量的PPTA浆粕;而在双螺杆挤出机中主反应温度则应控制在70℃左右为宜;物料在双螺杆中的停留时间超过3 min,才满足制备PPTA浆粕的工艺要求.螺杆的转速对PPTA 浆粕的相对分子质量的提高不显著,若转速太快,使物料在双螺杆中的停留时间缩短,反而不利于得到性能较好的PPTA浆粕.本研究为直接缩聚法制备PPTA浆粕的进一步放大打下了基础.     

Rheological behavior of controlled‐rheology polypropylenes obtained by peroxide‐promoted degradation during extrusion: Comparison between homopolymer and copolymer

In the present work, experimental studies of the free‐radical‐initiated molecular weight degradation of polypropylene in a modular self‐wiping corotating twin‐screw extruder are investigated. The control of the molecular weight distribution of polypropylene resins by peroxide degradation is widely used in the polymer industry. It allows one to adjust the viscosity of these resins to the level required for processing applications. The purpose of this work was to characterize the influence of peroxide degradation on the rheological behavior of a polypropylene homopolymer and a block polypropylene/polyethylene copolymer, which includes an addition of a low percentage of polyethylene (around 7%). The homopolymer exhibits a classical behavior: When the peroxide amount is increased, we observe a decrease in the viscosity corresponding to a decreasing molecular weight and a pronounced shift toward more Newtonian behavior. The rheological behavior of the copolymer is influenced by the presence of the polyethylene phase which greatly modifies the viscoelastic properties and increases the viscosity when the polypropylene matrix is highly degraded. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1243–1252, 2001     

A study on the rheological properties and processability of polycarbonate

The transport theory for the solids conveying zone in a single‐screw extruder was applied to calculate the pressure distributions along the screw channel for several bisphenol A polycarbonate resins based on the screw revolution speed and the flow rate. The pressure distributions and the flow rates of the resins were related to the structural and rheological properties. When polymers have the same chemical structure and number‐average molecular weight and the same mechanical properties, the polymer having a broader molecular weight distribution showed a lower glass transition temperature. For the polymer with broader MWD a relatively low pressure was developed along the screw channel, and an increased flow rate was observed. A relatively short melting length was also observed for this polymer and, accordingly, it was concluded that the polymer with a broader MWD has a better processability. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2921–2929, 2002     

相对分子质量及其分布对烯烃共聚物动态流变性能的影响

通过对一系列具有不同相对分子质量和相对分子质量分布的乙烯/α-烯烃（丁烯和己烯）共聚物的动态流变行为测试,研究了相对分子质量及其分布（即多分散性）对储能模量与频率、损耗模量与频率以及储能模量与损耗模量在低频区的关系曲线斜率的影响规律。结果表明：储能模量、损耗模量与频率以及储能模量与损耗模量的关系曲线的斜率不仅均低于理想的单分散体系,而且均随着相对分子质量或相对分子质量分布的增加而降低。     

Non-Newtonian and non-isothermal analysis of flow during polymerization of methyl methacrylate in a model twin screw extruder. Part II

The flow analysis network (FAN) method was modified to analyze the flow during polymerization of methyl methacrylate (MMA) in a model counter-rotating nonintermeshing screw extruder. The shear viscosity of the reactive mixture in the twin screw extruder was considered as a mixture of polymer and monomer. Thus, the reaction viscosity of the mixture of polymer and monomer was taken to be an explicit function dependent on the shear rate, temperature, conversion, and molecular weight. A new flow path method was developed to calculate the residence time distribution, which related to the degree of conversion. The numerical prediction of the velocity, temperature, viscosity, and pressure profiles during reaction in the model twin screw extruder is described.     

苯乙烯反应挤出聚合过程的实验研究

在SHL-φ35型紧密啮合同向旋转双螺杆挤出反应器中采用活性聚合引发体系,进行了苯乙烯反应挤出合成聚苯乙烯的研究。用静态实验法对一组螺杆结构的填充度分布和粘均分子量沿螺杆轴向分布进行计算。同时对单体在挤出反应器中的聚合过程进行了研究,提出了在活性聚合体系下,反应挤出合成聚苯乙烯两段聚合过程机理。     

Evolution of the peroxide‐induced degradation of polypropylene along a twin‐screw extruder: Experimental data and theoretical predictions

This article reports an experimental and theoretical study of the peroxide‐induced degradation of polypropylene in a corotating twin‐screw extruder. Experiments were performed with different peroxide concentrations and different operating conditions. The evolution of the chemical reaction along the extruder was monitored with specific sampling devices. Material changes were characterized by rheological measurements and via the determination of the molecular weights of samples collected at the same locations. The theoretical results were obtained with a model that coupled the interactions between flow conditions encountered in the extruder, the kinetics of the reaction, and the changes in the viscosity induced by changes in the molecular weight. The experimental results evidenced the relationships between the process conditions (peroxide concentration and processing parameters) and material properties (rheological properties and molecular structure of the modified polypropylene). Good agreement between the theoretical and experimental results was obtained. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006