氯乙烯/纳米CaCO_3原位聚合PVC树脂的加工性能研究

采用纳米CaCO3的微乳化分散技术制得了一种新型氯乙烯/纳米CaCO3原位聚合PVC树脂。对该PVC树脂的流变性能、热性能和微观结构等进行了研究。实验结果表明:这种新型PVC树脂在较高剪切应变下,熔体扭矩的下降幅度比通用PVC树脂增加了近一个数量级,在Haake流变仪上测得塑化熔融时间从通用PVC树脂的6 min缩短到2.5 min。这种新型PVC树脂的微商热失重曲线(DTG)的失重速率变化最大温度从299℃上升到320℃,维卡软化点上升了9℃。此外电子显微镜测试结果表明,纳米CaCO3在PVC树脂基体内呈现了小于100 nm颗粒的均匀分散。     

高耐热性的纳米CaCO3原位聚合PVC树脂新产品

在工业化反应装置上开发成功了氯乙烯原位悬浮聚合技术,得到了新品种的高耐热性的纳米CaCO3原位聚合PVC树脂。185℃刚果红试纸变色时间试验证明,纳米复合PVC树脂热分解时间比传统产品延长了近10倍。提出的机理模型是部分纳米CaCO3粒子在原位聚合过程中发生了崩解,界面上会出现具有很高化学活性的不饱和键态结构,这使得纳米CaCO3同时具有了中和PVC分子降解过程放出的HCl、取代PVC链上不稳定氯原子、加成大分子中不饱和双键等三大热稳定功能。介绍了用傅立叶变换红外光谱(FTIR)、差示扫描量热(DSC)和透射式电镜(TEM)等手段对以上机理的验证结果。     

氯乙烯／纳米CaCO3原位聚合

阐述了纳米CaCO3与氯乙烯原位聚合对PVC树脂的改性，并讨论了马来酸酐接枝作为对聚氯乙烯的表面改性，改善聚氯乙烯大分子与无机填料之间相容性的优越性与可能性。     

纳米CaCO3原位聚合PVC树脂的生产及加工应用

研究了纳米CaCO3的加入对氯乙烯原位悬浮聚合体系温度、压力及树脂性能的影响。结果显示：纳米CaCO3的加入,加剧了体系的聚合反应,压降提前出现;随着纳米CaCO3加入量的增大,树脂白度(按GB/T15595测定)由83％增加到86％,其它指标变化不大。将所得树脂用于PVC制品的加工应用,考察了其物理性能,结果显示：与同型号未改性PVC树脂相比,该树脂扭矩、物料熔融温度、产率、动态热稳定性等指标均有提高;随着纳米CaCO3加入量的增加,测试样冲击强度由3．68kJ／m^2增加到7．09kJ／m^2,拉伸强度由40．4MVa降低到37．2MVa,其它指标变化不大。     

原位聚合PVC／CaCO3纳米复合树脂剪切变稀现象的加剧与加工节能效应

简述了原位聚合PVC／CaCO3纳米复合树脂的制备方法与性能,通过毛细管流变仪考察了不同纳米CaCO3用量下PVC纳米树脂剪切速率对剪切黏度的影响,探讨了加工过程中PVC纳米树脂剪切变稀的机制并给出了加工应用实例,展望了PVC纳米树脂的发展前景。结果表明：加工过程中采用PVC纳米树脂可降低设备的能耗,具有很好的发展前景。     

原位聚合法制备PVC/纳米CaCO_3复合建材专用树脂

在 5L高压釜中采用悬浮法进行氯乙烯 /纳米 Ca CO3粒子原位聚合 ,研究了纳米 Ca CO3对聚合过程和产物性能的影响。结果表明 :纳米填料的加入使降压时间提前、树脂的相对分子质量及分布均略有增加 ;玻璃化温度变化不大 ,但热稳定性增加 ;树脂的粒径及分布变化较小 ,但吸油率上升 ;其制品的抗冲击性能约是纯 PVC树脂的 2倍 ,且拉伸强度、断裂伸长率均略好于共混树脂     

纳米CaCO3/PVC复合材料结构形态与冲击性能

对改性纳米CaCO3/PVC复合材料进行冲击强度的测试。结果表明，改性纳米CaCO3可提高PVC复合材料的裂缝引发能和裂缝增长能，其中裂缝增长能的提高尤为明显。复合材料的单缺口冲击强度达到81.1kJ.m^-2。用透射电子显微镜及扫描电子显微镜观察了纲米纳米CaCO3/PVC复合材料的微观结构及断面形态，发现表面改性后纳米CaCO3在PVC基体中达到了纳米级的分散，复合材料的断面产生了大量的网丝状结构。复合材料的微观结构进一步证实了纳米纳米CaCO3对PVC基体的显著增韧作用。     

原位聚合法制备纳米CaCO3/PVAc复合材料

将纳米CaCO3先分散在醋酸乙烯(VAc)中,再进行VAc溶液聚合,以原位聚合的方法制得纳米CaCO3/PVAc复合材料.主要研究了纳米CaCO3在VAc中的最佳分散条件和VAc溶液聚合的最佳条件参数,对不同纳米CaCO3含量的复合材料进行红外、透射电镜表征和断裂强度、断裂伸长率等性能的测试.结果显示:CaCO3与PVAc存在化学键的结合,CaCO3在PVAc中呈纳米级分散,当纳米CaCO3质量分数为0.2%～0.3%时,该复合材料力学性能最佳.     

表面改性纳米SiO_2原位聚合增强PVC树脂性能研究

采用原位聚合方法,利用表面经修饰带有不同基团的DNS-2、RNS-D两种型号纳米SiO2与氯乙烯聚合制备出纳米SiO2/PVC改性树脂。研究了DNS-2、RNS-D对树脂的力学性能、热稳定性的影响。研究结果表明,改性树脂的缺口冲击强度、热稳定性均提高,RNS-D参与了化学反应,RNS-D/PVC拉伸强度也提高,实现了同步增强与增韧。     

PVC／CPE／纳米CaCO3复合材料的性能研究

通过熔融共混的方法制备了PVC/纳米CaCO3、PVC/CPE和PVC/CPE/纳米CaCO3复合材料,然后对复合材料的性能进行分析,研究了纳米CaCO3与CPE的含量对复合材料的拉伸强度、冲击强度以及玻璃化转变温度等性能的影响规律,并对此影响规律进行合理的解释。     

原位悬浮聚合PVC/纳米CaCO3的制备及其性能

利用原位悬浮聚合法制备了聚氯乙烯(PVC)／纳米CaCO3复合树脂,并对其性能进行了研究。结果表明。与PVC相比,PVC／纳米CaCO3复合树脂的热稳定性、增塑剂吸收量及表观密度等有所提高;冲击强度Eh4．9kJ／m^2增加到13．0kJ／m^2：拉伸强度由58．2MPa增加到59．5MPa;断裂伸长率由57．8％增加到75．6％,达到了增韧增强的效果。     

表面改性纳米碳酸钙原位悬浮聚合PVC的制备与性能研究

采用湿法表面改性的纳米碳酸钙(nano-CaCO3)与VCM原位聚合,制备了nano-CaCO3原位聚合PVC树脂(简称原位PVC树脂),研究了其力学性能、加工性能、微观形貌和热稳定性等。结果表明:①nano-CaCO3能够很好地分散在PVC树脂中,对PVC基体产生很好的补强作用;与普通PVC试样相比,原位PVC试样缺口冲击强度提高到13.3 kJ/m2,效果显著;其加工性能也得到了提高。②试样冲击断面的扫描电子显微镜照片表明原位PVC试样为韧性断裂,普通PVC试样为脆性断裂。③DSC试验表明,原位PVC树脂的热稳定性优于纯PVC树脂。     

氯乙烯聚合和聚氯乙烯改性的研究

综述2008年CA报道的有关氯乙烯聚合和聚氯乙烯改性的主要文献和专利。     

纳米碳酸钙原位聚合聚氯乙烯树脂的性能及应用

介绍了纳米碳酸钙原位聚合聚氯乙烯的结构和性能,同时对该树脂进行了有关的应用试验,并对其发展前景作了科学展望。     

基于30m~3聚合釜的纳米CaCO_3原位聚合PVC树脂颗粒特性预测与优化

通过微乳化分散技术使CaCO3实现良好分散,通过氯乙烯原位悬浮聚合制得了纳米CaCO3微乳化法原位聚合PVC树脂(简称纳米PVC树脂)。为解决纳米PVC树脂的颗粒形态控制难题,提出了基于组合神经网络的软测量方法,建立了纳米PVC树脂颗粒特性的软测量预测模型,应用效果表明该软测量模型能较准确地预测纳米PVC树脂的平均粒径。利用该软测量预测模型在30 m3聚合釜上实现了纳米PVC树脂颗粒特性优化,制得具有较理想颗粒特性的纳米PVC树脂。     

Continuous dosing of fast initiator during vinyl chloride suspension polymerization: Thermal stability of PVC resin

Thermal stability of poly(vinyl chloride) (PVC) produced using continuous dosages of a fast initiator method was investigated in terms of morphological and microstructural characteristics. The results were compared with the properties of the PVC prepared by conventional polymerization method. The Brabender^® Plastograph and DSC results showed a lower fusion time, higher stable time, and greater degree of fusion for PVC obtained by polymerization using initiator continuous dosage method. Also, chemical analysis indicated that the PVC produced under an initiator continuous dosage system have lower structural defects, that is, branch numbers, internal double bonds, labile chlorine, and tacticity index, thereby improving the thermal stability of PVC resin. The results obtained from dehydrochlorination and thermogravimetry analysis confirm the improvement of thermal stability of PVC chains synthesized with continuous dosages of a fast initiator. Moreover, it was found that the concentration of microstructural defects and the dehydrochlorination rates of the PVC samples prepared by both processes increase with monomer conversion, particularly after critical conversion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44480.     

Effect of degree of polymerization on gelation and flow processability of poly(vinyl chloride)

The effect of degree of polymerization (DP) on the gelation and flow processability of poly(vinyl chloride) (PVC) was studied. Sheets with adjusted degree of gelation were prepared by rolling rigid pipe formulation suspension PVC compounds with DPs of 800, 1050 and 1300 by changing the milling temperature. Their degrees of gelation were measured with DSC and their capillary flow properties were measured with a capillary rheometer at 150, 170 and 190°C and the effect of DP on the relation between gelation and flow processabilities was studied. Because of the higher shearing heat during milling, the sample with the higher DP had a higher history temperature and thus tended to show a higher degree of gelation. The viscosity increased as the gelation increased. The dependency of viscosity on DP was higher at higher milling and extrusion temperatures and thus at a higher degree of gelation and a lower shear rate. This was assumed to be attributed to the more prominent uniform molecular flow as against the particle flow. The die swell increased with increasing the milling and extrusion temperatures and hence with increasing the gelation. A sample with a lower DP tended to show a larger die swell and this tendency was even more pronounced at the higher extrusion temperature. The melt fracture easily occurred when a sample with advanced gelation was extruded at low temperature. Whereas at low milling temperatures a sample with the lower DP showed a lower critical shear rate at onset of melt fracture, and thus easily generating melt fracture, at high milling temperatures it showed a higher critical shear rate and hence scarcely generated melt fracture. These experimental results were explained by the fact and concept that a sample with a lower DP shows a higher increase in the gelation during extrusion and/or the slighter feature of particle flow as against the uniform molecular flow at the same gelation level. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1915–1938, 2004     

微悬浮法PVC糊树脂的合成研究

采用三氯乙烯作为氯乙烯模拟液,研究主/助乳化剂结构、用量和比例等对分散液滴粒径及粒度分布的影响。采用5 L高压夹套釜进行氯乙烯微悬浮聚合,研究主/助乳化剂结构、用量、比例和水油比对PVC初级粒子平均粒径和粒度分布的影响。发现以十二烷基硫酸钠(SDS)为主乳化剂时分散液滴的尺寸最小,PVC胶乳稳定,粒度分布窄;随着脂肪醇助乳化剂链长的增加,分散液滴尺寸明显减小,十六醇、十八醇或两者的混合醇是氯乙烯微悬浮聚合适宜的助乳化剂;随着十六醇或十六~十八混合醇与SDS用量比的增加,分散液滴和PVC胶乳粒子的尺寸逐渐减小,粒度分布趋窄。微悬浮聚合PVC糊树脂包含粒径范围较宽但呈连续分布的初级粒子,通过主/助乳化剂用量比的改变,可调节PVC初级粒子的平均粒径及粒度分布。     

悬浮聚合型聚氯乙烯树脂的研究进展

悬浮聚合法是制备聚氯乙烯树脂的最主要方法,然而其制备的产品存在表观密度低、球形率不足、吸塑性能差、"鱼眼"数多、透明性低等缺陷;在悬浮聚合过程中还存在因聚合反应釜结垢、引发剂半衰期过长等因素而造成生产效率低下的问题。统计分析了目前国内外悬浮聚合生产聚氯乙烯专利的申请情况,对解决上述技术问题的手段进行了归纳,并对悬浮聚合技术的发展趋势进行了总结和展望。