聚合物微发泡材料制备技术应用研究进展

20世纪90年代末,超临界流体(SCF)制备聚合物微发泡材料实现了工业化,这种方法制备的微发泡材料具有非常多的优点,被誉为"21世纪的新型材料"。主要介绍了聚合物微发泡材料应用研究方面的进展,主要涉及聚合物微发泡材料的制备方法及其特点,工艺参数对成型过程的影响及成型设备的特点等方面,重点探讨了非连续方法和连续方法的提出及其发展过程。     

超临界流体制备聚合物微孔材料技术研究进展

上世纪90年代，超临界流体(SCF)制备聚合物微孔材料实现了工业化，这种方法制备的微孔材料具有非常多的优点，被誉为是“21世纪的新型材料”。本文首先介绍了SCF的概念、性质，以及其在相关领域的应用情况。然后对采用SCF制备聚合物微孔材料的理论研究进展进行了介绍，主要讨论了在聚合物中的溶解行为、微孔的形成和长大机理以及聚合物／SCF体系的流变行为等三个方面的研究内容。本文还介绍了采用SCF制备聚合物微孔材料的应用研究进展，探讨了非连续方法和连续方法的发展过程，并重点对连续成型方法的设备进行了介绍。     

微发泡聚合物材料的研究进展

微发泡聚合物材料是泡孔尺寸在微米级的一种新型高分子材料,因其独特的微孔结构能够改善制品的尺寸稳定性、收缩率等问题,已经成为近年来聚合物材料的研究热点。本文综述了微发泡成型研究机理,成型加工参数、纳米填料和发泡剂对微发泡聚合物材料结构与性能的影响,并对众多研究结果进行了分析,提出了未来微发泡聚合物材料的研究领域有待于进一步深入的研究方向,并对微发泡聚合物材料的研究及应用前景进行了展望,提出扩大工业应用的趋势是开发出微发泡聚合物母料来替代物理以及化学发泡。这些基础性的研究工作对于深入理解微发泡聚合物材料的形成机理及后续的应用研究具有非常重要的意义。     

开孔型聚合物微发泡材料研究进展

通过回顾目前几种微孔材料成型的主要方法,介绍了微发泡成型技术用于制备开孔型微孔材料的必要性。讨论了关于开孔型聚合物微发泡材料制备技术及研究方法的几种思路,分别是不相容聚合物共混、泡孔合并模型、熔融挤出发泡、开孔剂法和气体浓度阈(值)等方法,这些方法的微孔成型机理各不相同,所制备的材料微观结构也各有特点。文献分析表明:微发泡成型方法用于开孔型微孔材料的制备是一种非常有前景的技术。     

浅析超临界CO2在连续挤出微孔塑料中的应用

超临界流体（简称SCF）技术已广泛应用于分离、反应、材料加工、生物技术以及环境保护等领域，其中在材料加工中的应用包括塑料的分解回收，聚合物微粒制备，聚合物的增塑、改性及功能化等。而以SCF作发泡剂制备聚合物微孔材料也是SCF技术应用的一个重要方向。采用此方法制得的微孔塑料的冲击韧性、刚性及耐久性均比未发泡塑料及普通发泡塑料显著提高。     

纳米粒子在微孔发泡聚合物中应用的研究进展

微孔发泡聚合物是一种发展迅速的新型发泡材料,因其具有质量轻、环境友好、渗透性好等优点,具有极其广阔的应用领域。同时,纳米粒子对微孔发泡聚合物的气泡成核、气泡生长、气泡定型等影响非常显著。因此,纳米粒子对微孔发泡聚合物泡孔形貌调控机理的相关研究,成为近年来国内外学者研究的热点。介绍了聚合物纳米复合材料的制备方法,包括间歇式釜压发泡、连续挤出发泡和注塑成型发泡;然后分析了纳米粒子在微孔发泡聚合物中的添加方法,包括原位聚合法、插层法、直接混合法;综述了纳米粒子对微孔发泡聚合物体系的影响;最后对微孔发泡聚合物的研究方向和应用前景进行了展望。     

超临界工艺制备聚乳酸泡沫技术研究

超临界流体(SCF)是一种制备可降解聚合物泡沫的先进技术。利用超临界二氧化碳发泡成形技术,制备可降解高分子聚乳酸(PLA)泡沫材料,并通过条件试验确定了最适合的成形工艺参数,同时结合聚乳酸材料的物理性质,对控制泡沫形态的机理进行了研究。     

延时时间对PA6发泡行为及力学性能影响

采用"二次开模"注射成型工艺制备微发泡聚酰胺6(PA6)材料,研究了不同延时时间对PA6材料发泡行为及力学性能的影响.结果表明:延时时间能有效控制微发泡PA6材料的发泡过程,较短的延时时间内,模具型腔压力下降较大,压力降速率较快,有利于聚合物泡孔成核速率的提高.随着延时时间增加,微发泡PA6材料的泡孔平均直径增大,泡孔...     

聚合物发泡材料研究中心

正聚合物发泡材料研究中心(简称CPFOAM)成立于2006年,研究团队由材料学、材料加工工程专业的多名教授、副教授、高级工程师、博士、硕士和本科生组成,设在北京工商大学轻工业塑料加工应用研究所(材料科学与工程系)。自成立以来,相继承担了多项有关聚合物发泡的省部级科研项目,参与制、修订泡沫塑料行业的多项国家标准和行业标准,并与泡沫塑料行业的企业建立了广泛合作和联系。研究中心具有自行设计的挤出发泡试验机组2(台)套,可以方便地开展热塑性聚合物的物理发泡和化学发泡试验研究;同时,研究中心具有比较齐全的发泡材料结构表征和性能检测仪器及设备,能够开展发泡体系的流变行为和结晶行为研究、聚合物的发泡机理研究以及发泡材料泡体结构的微观表征和发泡材料的物理性能、力学性能、热性能、耐温性、耐候性、耐化学性、燃烧性能等的评价。聚合物发泡材料研究中心(CPFOAM)在以下领域开展研究:     

微孔及纳米孔发泡材料研究进展

对聚合物微孔发泡基本过程、机理、聚合物微孔发泡的实施等进行了介绍,同时指出通过嵌段共聚物为载体可以制备纳米孔发泡材料。     

Separating polymer solutions using high pressure lower critical solution temperature (LCST) phenomena

A lower critical solution temperature (LCST) phase split can be used as an alternative to steam stripping for separating polymer solutions, By adding a supercritical fluid (SCF) additive to the polymer solution, the LCST can be lowered, thus minimizing the possibility of polymer degradation and also reducing the thermal energy requirements for the process. Experimental results for the poly(ethylene-co-propylene)-hexane-SCF ethylene system are shown as an example of the type of phase behavior observed with polymer-solvent-SCF additive solutions. Adding 20 percent (w/w) ethylene to the polymer solution lowers the temperature of the LCST by 109°C. The addition of 30 percent (w/w) ethylene to the polymer solution lowers the temperature of the LCST curve sufficiently to merge this curve with the upper critical solution temperature (UCST) curve. When the lower critical end point (LCEP) is plotted against the critical temperature of the solvent the data for poly(ethylenie-co-propylene)-solvent systems are well represented by a single curve. A more fundamental modeling approach is needed to estimate the pressure of the LCEP and the concentration of SCF additive necessary to merge the LCST and the UCST curves. Patterson's theory of corresponding states can be used for these calculations.     

PPTA纤维原纤化的研究进展

阐述了聚对苯二甲酰对苯二胺(PPTA)纤维的结晶结构及其原纤化的机理,综述了国内外PPTA纤维原纤化的研究进展。PPTA纤维具有皮芯结构,芯层含有高度取向的多重原纤。PPTA浆粕的制备方法主要分为机械法以及直接成型法,其关键技术在于控制纤维原纤化程度,保持纤维强度以及解决分散性能。机械法制备浆粕的方法包括磨浆设备的改进,在聚合体系中添加其他聚合物改善纤维的磨浆性能以及混合其他易原纤化纤维磨浆等。直接成型法包括沉析法和凝胶法,相对于机械法制浆,直接成型法具有工艺流程简单的优点,但是使用此方法制备浆粕,难以控制原纤的形状,纤维强度低。     

碳纤维增强PBT/ABS-g-MAH复合材料的力学性能和流变行为

利用扫描电子显微镜、电子万能试验机、冲击试验机、旋转流变仪和差示扫描量热仪分别研究了聚对苯二甲酸丁二醇酯（PBT）/马来酸酐接枝丙烯腈丁二烯苯乙烯共聚物（ABS-g-MAH）/短切碳纤维（SCF）复合材料的相形态、力学性能、流变和结晶行为。结果表明,复合材料断面上纤维的分布较为均匀,SCF与PBT之间有较好的界面结合性能;当SCF含量为5 %~10 ％时,复合材料的力学性能得到明显提高;随着SCF含量的增加,复合材料熔体的复数黏度呈现先降低后升高的趋势;在体系中添加适量的SCF可以起到成核剂的作用,由于结晶变得相对容易,从而使结晶温度升高,然而过量的SCF会在一定范围内阻碍PBT的结晶。     

The application of a supercritical antisolvent process for sustained drug delivery

Supercritical processes for drug delivery system design have attracted considerable attention recently. This present work investigates the application of a supercritical antisolvent coating process for controlled drug release design. Hydrocortisone as the host drug particles and poly(lactide-co-glycolide) (PLGA) as the polymer carrier were selected as the model system for this purpose. In this research the drug particles were suspended in a polymer solution of dichloromethane. The suspension was then sprayed into supercritical CO₂ as an antisolvent. A parallel study of co-precipitation of the drug and polymer using the same supercritical antisolvent process at the same operating conditions was performed for comparison with the coating process. SEM images were used to characterize the drug particles before and after and the assay analysis was carried out using HPLC. The coated particles and co-precipitated particles were evaluated in terms of encapsulation efficiency and drug release profiles. The major advantage of this new approach is the ability to physically coat very fine (< 30 μm) particles without having to dissolve them in an organic solvent. It was found that higher polymer to drug ratios produced higher encapsulation efficiencies and the coated drug particles did show sustained release behavior. The co-precipitation of the drug and polymer (at the same operating conditions), however, did not exhibit any sustained release.     

Study on the Rheological Behavior of PP/Supercritical CO2 Mixture

The addition of supercritical fluid (SCF) constituent in polymer processing is effective in reducing the viscosity of polymer melt. The magnitude of viscosity reduction is related to operation temperature, SCF addition amount, and the shear rate. In this study, a conventional injection machine has been modified to investigate the rheological behavior of polypropylene(PP)/SCCO₂ mixture. The range of shear rate can be achieved as high as order of 1E4 (1/s) by this machinery. The result reveals that a negative extrapolated exit pressure is observed, and higher negative values result from higher shear rates. The viscosity of PP melt decreases significantly with the existence of SCF at low shear rates (<2500 l/s). However, the viscosity reduction observed diminishes as shear rates raise, and reaches 20% at shear rate 5000 l/s. As shear rates increase further, the intention of reduction tends to be more moderate.     

Heat melding of voided polyethylene microstructures

This paper is concerned with the fabrication of voided polyethylene microstructures by heat melding of plastic microcapillary films (MCFs) to form microcapillary monoliths (MCMs), which are consolidated layers of MCFs forming in two-dimensional arrays of microcapillaries. MCMs were manufactured by heat melding multiple layers of low-voidage MCFs or high-voidage MCFs. The optimal conditions for interface adhesion of the MCFs to create MCMs without compromising capillary integrity were investigated.The MCFs were processed from linear low-density polyethylene (LLDPE) and the melt rheology of the polymer was studied to provide rheological parameters that could be used both to gain an understanding of the character of the polymer and for modeling of the MCM forming process. In particular, the temperature dependent nature of the rheology was investigated at the transition from viscous-dominated behavior to elastic-dominated behavior. Modeling of the melding process provided some additional information and confirmed issues in relation to the thermal bonding temperatures and mechanisms.     

超临界丙烷分级聚苯乙烯

利用超临界流体的溶剂强度随温度、压力的变化而变化和超临界流体泄压至常压时溶质完全析出的特点,采用超临界丙烷取代常规溶剂对聚苯乙烯进行分级研究,以期柔性地调节操作温度和压力,获得分子量分布较窄的聚合物级分.结果表明,对多分散系数为4.225的聚苯乙烯进行等温超临界分级和等压超临界分级实验能够得到多分散系数分别为1.0～2.0和1.3～2.0的级分.并且发现,压力和温度越高,溶剂的溶解能力越大,分级得到的级分分子量越大.同时,从高聚物溶液理论出发,结合超临界溶液的溶解特性,建立了超临界流体分级高聚物的级分分子量的预测模型.利用实验数据对模型参数优化结果表明,当压力大于25 MPa时,超临界等温分级模型的平均相对误差为5.32％;当温度大于413.15 K时,超临界等压分级模型的平均相对误差为18.03%.     

Supercritical fluid technology parameters affecting size and behavior of stereocomplex polylactide particles and their composites

Polylactide (PLA) is a eco‐friendly and biodegradable material that can be synthesized from renewable resources. PLA features poly(d ‐lactic acid) (PDLA) and poly(l ‐lactic acid) (PLLA) enantiomers. Supercritical fluid (SCF) technology is a very promising method for the stereocomplexation between PDLA and PLLA enantiomers. This study acquires stereocomplex (sc‐)PLA particles with diverse sizes and behaviors by controlling the experimental conditions. Various parameters including polymer concentration, reaction temperature, stirring speed, pressure reducing speed, and final temperature were controlled to adjust size and behavior of sc‐PLA particles. Additionally, we analyzed the effect of subsequent processing following SCF (such as homogenization, mechanical stirring, and sonication) on the size and morphological behavior of sc‐PLA particles. Finally, the mechanical strengths of different PLA composites featuring different sc‐PLA filler sizes were determined. The mechanical strength of PLA composites was significantly improved when using smaller filler sizes. POLYM. ENG. SCI., 58:1193–1200, 2018. © 2017 Society of Plastics Engineers