高分子材料烧结成型研究进展

高分子材料烧结成型是借鉴粉末冶金技术而形成的一种特殊的成型加工方法,特别适合熔体粘度极大、高温易分解的高分子材料的成型加工。传统高分子材料的烧结成型温度在熔点以上,通过粉末的熔融和界面扩散将粉末烧结在一起。本文首先对聚四氟乙烯和超高分子量聚乙烯这两种常用于烧结成型的高分子材料的烧结成型工艺条件、成型机理及其多功能材料的制备等方面进行了系统的介绍;最后,重点分析了我们组最近针对立构复合型聚乳酸熔融稳定性差、熔融加工易降解的问题而提出的一种低温(低于立构复合晶体熔点)烧结成型新方法,即通过在粉末表面形成新立构复合晶体将粉末烧结在一起,并对其研究进展进行了综述。     

低温等离子体处理天然纤维的ESR研究

低温等离子体表面改质技术,近年来在纤维加工领域的应用引起广泛注目。纤维、高分子材料经低温等离子体处理,在纤维基质中生成自由基。这些自由基同活性原子团一样,其中不稳定的自由基迅速重新结合,而稳定的自由基就残留在纤维基质中。本文研究了天然纤维棉、麻、羊毛和蚕丝分别在O_2、N_2、Ar、CO及CF_4气体中的低温等离子体表面改质处理,用ESR光谱测定了纤维基质中生成的自由基的相对强度,并讨论了热处理对自由基稳定性的影响。     

《高分子材料成型加工》课程教学创新探索

《高分子材料成型加工》作为高分子材料学科的必修课程,是培养具备高分子材料与工程知识,从事高分子材料研究、开发和加工应用的工程技术人员的核心课程。课程内容丰富、实践性强,具有自己独特的理论体系和技术方法。近代科学技术与工业的进步,为高分子材料学科的发展开拓了更广泛的前景,同时对《高分子材料成型加工》课程教学也提出了更高更新的要求,为此传统的教学资源和方法急待改革和完善。本文从优化教学内容、开拓教学模式、增加学科融合和交叉等方面对高分子材料成型加工课程的教学进行了创新性探索,通过深入优化教学方案,提高教学质量和人才培养质量,为学生今后从事高分子材料方面的工作奠定良好的理论和实践基础。     

高分子材料支化结构与流变性的联系串讲北大核心CSCD

高分子链结构为直链型或支化型以及高分子支链的形态、多寡和长度对材料的剪切黏度、黏流活化能、熔体破裂现象等流变性能有显著影响,且与高分子材料成型加工行为密不可分。本文以串讲方式讨论了高分子材料支化结构与流变性能之间的联系。理解、串并、归纳和总结高分子支化结构与流变性之间的联系有利于使学生更加深刻领会《聚合物流变学》课程中高分子材料结构与性能间的关系,串联高分子物理、聚合物流变学、高分子材料成型加工系列专业课程知识。     

高分子材料支化结构与流变性的联系串讲

高分子链结构为直链型或支化型以及高分子支链的形态、多寡和长度对材料的剪切黏度、黏流活化能、熔体破裂现象等流变性能有显著影响,且与高分子材料成型加工行为密不可分。本文以串讲方式讨论了高分子材料支化结构与流变性能之间的联系。理解、串并、归纳和总结高分子支化结构与流变性之间的联系有利于使学生更加深刻领会《聚合物流变学》课程中高分子材料结构与性能间的关系,串联高分子物理、聚合物流变学、高分子材料成型加工系列专业课程知识。     

《高分子材料成型加工新技术》课程教学改革探索

《高分子材料成型加工新技术》是在《聚合物加工机械》和《聚合物加工原理》两门本科专业课基础上发展形成的一门技术前沿性的新课程。该课程主要讲授当前高分子材料成型加工的新装备、新技术和新方法等,既可作为高分子材料与工程专业本科生拓宽专业知识面的专业选修课,也可作为材料加工工程专业硕士研究生的专业主干课。本文结合课程团队多年给研究生讲授《高分子材料成型加工新技术》专业主干课的经历,从教学目标、教学内容、教学方法和教学效果四个方面介绍了开设这门课程的经验和体会。     

高分子科学实验教学改革初探

设想将高分子化学、高分子物理和高分子成型加工三门实验课程有机地串联起来,组建成一门包括从高分子材料设计(用计算机软件进行分子设计、性能模拟)、聚合物合成、性能测试(物性表征)到加工成型(制作成高分子材料制品),能环环相扣、互动式的、柔性化的高分子科学实验课程;提出了初步的实践方案.     

《高分子材料成型加工原理》课程教学方法探究

《高分子材料成型加工原理》是高分子材料与工程专业最重要的专业课程之一。但是仅凭课堂讲授很难让学生理解高分子材料加工工艺的过程及其原理,学生参与性差。针对学院的《高分子材料成型加工原理》课程特点,通过计算机在配方设计当中的应用、多媒体的应用、案例分析和学生互动交流相结合的教学方法加深学生对高分子材料加工过程及其原理等抽象概念的理解。授课方式既有理论讲解、又有实例演示,使课程教学更具实用性,激发学生的学习兴趣,培养学生分析问题、解决问题的能力,提高了高分子专业这门课程的教学效果。     

针对工科专业的高分子材料流变学教学实践和体会

高分子材料流变学对高分子加工工艺、成型设备以及模具的设计具有至关重要的指导意义,是高分子材料相关专业的必修基础课程。本文简介了流变学的发展概况和在青岛科技大学的开课情况,并总结了作者在工科专业学生的教学实践中针对具体内容的教授技巧与经验,提出针对本科阶段的学生应该着重介绍流变学的基础知识和基本原理,并注重理论和实践的有机结合,通过流变测量仪器的原理分析和高聚物加工成型工艺的流变学剖析来进一步阐明流变学基本概念和原理。     

高分子成型加工创新性实验体系

针对目前高分子专业成型加工实验课程各环节缺乏相互联系,无法实现对学生专业素质综合培养的不足,将原本各自独立的实验内容加以整合,建立综合性、系统性的创新性实验体系.高分子成型加工创新性实验体系参照高分子材料加工企业的生产模式,划分为配方设计和成型加工工艺两个紧密联系的实践教学环节.通过征集科研课题和企业难题、学生自己制定...     

Low‐temperature processing of polymer nanoparticles for bioactive composites

Utilizing an ingenious control over the enhanced segmental mobility of polymer chains, we proposed a novel low‐temperature processing strategy for polymeric materials, where the materials were processed substantially below their normal glass transition temperature. This state of art was achieved by the combination of the confinement effects and the stress‐induced effects on polymer nanoparticles. This method proved to be universal for various polymer systems, that is, polystyrene, polyvinyl chloride, polycarbonate, and polyphenylene oxide. Compared with the traditional high‐temperature processing, the low‐temperature processing efficiently avoids thermal degradation, and the processed polymer maintains moderate mechanical properties. In addition, this approach provides a straightforward method for the preparation of heat‐labile bioactive polymer composites without biological surface modification. The prepared lysozyme/polystyrene composite exhibits excellent bactericidal activity and striking sustained release characteristics. This facile, universal and energy‐saving low‐temperature processing strategy is expected to open avenues toward expanding manufacturing methodology and the applications of polymeric materials, especially for bioactive composites, where conventional high‐temperature processing is not applicable. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2514–2520     

反应性挤出加工制备无卤阻燃高分子材料

聚合物反应性加工集聚合物加工与化学反应为一体,以聚合物加工装置为反应器,通过聚合物加工过程中的化学反应形成新物质和新结构,实现高分子材料的高性能化和功能化,是高分子材料科学的研究前沿之一.本文简要介绍了我们研究小组近年来采用反应性挤出加工制备高性能无卤阻燃高分子材料方面的研究进展.利用反应性挤出加工剪切力强、温度可控以及易于传质传热的特点实现了常规方法难以合成的高黏阻燃剂三聚氰胺磷酸盐季戊四醇酯（MPP）和三聚氰胺氰尿酸（MCA）的高效合成,制备了综合性能优良的聚丙烯/MPP、尼龙6/MCA等无卤阻燃高分子材料.研究所涉及的化学和物理方法,为聚合物无卤阻燃提供了高效、经济、环保和易于工业化的新技术,并拓宽了聚合物反应性加工的应用领域.     

Atomic mobility in strained glassy polymers: The role of fold catastrophes on the potential energy surface

Deformation is known to enhance the atomic mobility in disordered systems such as polymer materials. To elucidate the origin of this phenomenon, we carry out two types of simulations: molecular dynamics (MD) simulations, which determine the atomic trajectories at finite temperature, and quasi-static simulations, which determine the atomic trajectories in the limit of zero temperature (and in the limit of zero shear rate). The quasi-static simulations show discontinuous changes in properties, such as system energy and atomic mobility. We use a normal mode analysis to show that these discontinuous changes arise from fold catastrophes of the potential energy landscape, in which energy minima flatten out and the heights of energy barriers decrease to zero; this was demonstrated by normal mode frequencies following a power law with an exponent of 0.5 as the discontinuous change is approached. After the fold catastrophe, the system relaxes to a different energy minimum, giving rise to atomic displacements. These fold catastrophes are the only mechanism for diffusive atomic displacements in the quasi-static simulations, where there is no thermal energy. We compared the mean-squared displacements as a function of strain from the quasi-static simulations to those from MD simulations (which do include thermal effects)—the similarity of the values of the mean-squared displacements in these two types of simulations demonstrates that the fold catastrophes underlie the enhanced dynamics in strained polymer systems even at finite temperature. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Effect of orientation and mobility of polymer molecules at surfaces on contact angle and its hysteresis

The contact angle of a water droplet on the surface of a solid polymer or hydrogel (water-swollen three-dimensional network) depends on whether a hydrophilic moiety of the polymer molecule is oriented towards the air interface or towards the bulk of the solid, but not on the hydrophilicity of the molecule. Therefore, the short-range rotational mobility of a polymer molecule has a major influence on the apparent hydrophilicity of a polymer surface as measured by the contact angle of water. By the came principle, the abnormally large hysteresis effect observed in advancing and receding contact angles of water on some polymer surfaces can be attributed to the reorientation of hydrophilic moieties of polymer molecules at the surface. These factors are demonstrated by selected polymer surfaces with different degrees of mobility at the polymer-air interface.     

Molecular dynamics simulations of polymer transport in nanocomposites

Molecular dynamics simulations on the Kremer-Grest bead-spring model of polymer melts are used to study the effect of spherical nanoparticles on chain diffusion. We find that chain diffusivity is enhanced relative to its bulk value when polymer-particle interactions are repulsive and is reduced when polymer-particle interactions are strongly attractive. In both cases chain diffusivity assumes its bulk value when the chain center of mass is about one radius of gyration R(g) away from the particle surface. This behavior echoes the behavior of polymer melts confined between two flat surfaces, except in the limit of severe confinement where the surface influence on polymer mobility is more pronounced for flat surfaces. A particularly interesting fact is that, even though chain motion is strongly speeded up in the presence of repulsive boundaries, this effect can be reversed by pinning one isolated monomer onto the surface. This result strongly stresses the importance of properly specifying boundary conditions when the near surface dynamics of chains are studied.     

原位探测防污高分子材料与液体界面的分子结构

Marine organisms such as plants, algae or small animals can adhere to surfaces of materials that are submerged in ocean. The accumulation of these organisms on surfaces is a marine biofouling process that has considerable adverse effects. Marine biofouling on ship hulls can cause severe fuel consumption increase. Investigations on antifouling polymers are therefore becoming important research topics for marine vessel operations. Antifouling polymers can be applied as coating layers on the ship hull, protecting it against the settlement and growth of sea organisms. Polyethylene glycol (PEG) is a hydrophilic polymer that can effectively resist the accumulation of marine organisms. PEG-based antifouling coatings have therefore been extensively researched and developed. However, the inferior stability of PEG makes it subject to degradation, rendering it ineffective for long-term services. Zwitterionic polymers have also emerged as promising antifouling materials in recent years. These polymers consist of both positively charged and negatively charged functional groups. Various zwitterionic polymers have been demonstrated to exhibit exceptional antifouling properties. Previously, surface characterizations of zwitterionic polymers have revealed that strong surface hydration is critical for their antifouling properties. In addition to these hydrophilic polymers, amphiphilic materials have also been developed as potential antifouling coatings. Both hydrophobic and hydrophilic functional groups are incorporated into the backbones or sidechains of these polymers. It has been demonstrated that the antifouling performance can be enhanced by precisely controlling the sequence of the hydrophobic-hydrophilic functionalities. Since biofouling generally occurs at the outer surface of the coatings, the antifouling properties of these coatings are closely related to their surface characteristics in water. Therefore, understanding of the surface molecular structures of antifouling materials is imperative for their future developments. In this review, we will summarize our recent advancements of antifouling material surface analysis using sum frequency generation (SFG) vibrational spectroscopy. SFG is a surface-sensitive technique which can provide molecular information of water and polymer structures at interfaces in situ in real time. The antifouling polymers we will review include zwitterionic polymer brushes, mixed charged polymers, and amphiphilic polypeptoids. Interfacial hydration studies of these polymers by SFG will be presented. The salt effect on antifouling polymer surface hydration will also be discussed. In addition, the interactions between antifouling materials and protein molecules as well as algae will be reviewed. The above research clearly established strong correlations between strong surface hydration and good antifouling properties. It also demonstrated that SFG is a powerful technique to provide molecular level understanding of polymer antifouling mechanisms.     

Selective protein adsorption on a phase-separated solvent-cast polymer blend

Polymer-based biomedical devices are growing increasingly sophisticated as compositions evolve toward copolymers and blends in order to satisfy complex design criteria. Such polymers afford opportunities for both micro- and macrophase separation at nano- and micro-length scales and raise questions concerning the role of heterogeneous surface morphology on protein adsorption. Adsorbed protein layers play a critical role in mediating the interaction of cells with polymer surfaces, and both understanding and controlling protein adsorption is assuming greater significance in the development of surfaces with enhanced physiological compatibility. Here we study the short-time adsorption of ferritin, a model protein highly resistant to denaturation and easily imaged in the transmission electron microscope (TEM), onto a phase-separated homopolymer blend of polycaprolactone (PCL) and a polycarbonate derived from desaminotyrosyl-tyrosine dodecyl ester (PDTD). At physiological pH, ferritin selectively adsorbs onto the PDTD phase at a surface density approximately three times greater than that on the PCL phase. By decreasing the pH below ferritin's isoelectric point so its average charge becomes positive, the selective adsorption disappears and the surface density of adsorbed ferritin becomes independent of the phase separation. We attribute the selectivity to the electrostatic repulsion between ferritin and hydrolytically charged PCL, both of which will have a net negative charge at physiological pH. To perform these experiments, we solvent-cast ultrathin polymer films onto dissolvable salt substrates, and we characterize the morphology by TEM imaging and quantitative spatially resolved electron energy-loss spectroscopy (EELS). We find that the film morphology depends strongly on such processing-related variables as the solvent evaporation rate and the nature of the surface in contact with the polymer film during casting. The adsorption of ferritin depends on whether the film is phase-separated as well as to which surface of the film the protein solution is exposed, and these findings suggest that seemingly small variations in polymer processing that influence both the bulk and surface morphology can have a profound effect on the short-time protein adsorption.     

Surface characteristics of a self-polymerized dopamine coating deposited on hydrophobic polymer films

This study aims to explore the fundamental surface characteristics of polydopamine (pDA)-coated hydrophobic polymer films. A poly(vinylidene fluoride) (PVDF) film was surface modified by dip coating in an aqueous solution of dopamine on the basis of its self-polymerization and strong adhesion feature. The self-polymerization and deposition rates of dopamine on film surfaces increased with increasing temperature as evaluated by both spectroscopic ellipsometry and scanning electronic microscopy (SEM). Changes in the surface morphologies of pDA-coated films as well as the size and shape of pDA particles in the solution were also investigated by SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM). The surface roughness and surface free energy of pDA-modified films were mainly affected by the reaction temperature and showed only a slight dependence on the reaction time and concentration of the dopamine solution. Additionally, three other typical hydrophobic polymer films of polytetrafluoroethylene (PTFE), poly(ethylene terephthalate) (PET), and polyimide (PI) were also modified by the same procedure. The lyophilicity (liquid affinity) and surface free energy of these polymer films were enhanced significantly after being coated with pDA, as were those of PVDF films. It is indicated that the deposition behavior of pDA is not strongly dependent on the nature of the substrates. This information provides us with not only a better understanding of biologically inspired surface chemistry for pDA coatings but also effective strategies for exploiting the properties of dopamine to create novel functional polymer materials.     

Electrophoretic mobility of poly(acrylic acid)-coated alumina particles

The effect of poly (acrylic acid) (PAA) adsorption on the electrokinetic behavior of alumina dispersions under high pH conditions was investigated as a function of polymer concentration and molecular weight as well as the presence, concentration and ion type of background electrolyte. Systems of this type are relevant to nuclear waste treatment, in which PAA is known to be an effective rheology modifier. The presence of all but the lowest molecular weight PAA studied (1800) led to decreases in dynamic electrophoretic mobility at low polymer concentrations, attributable to bridging flocculation, as verified by measurements of particle size distribution. Bridging effects increased with polymer molecular weight, and decreased with polymer concentration. Increases in background electrolyte concentration enhanced dynamic electrophoretic mobility as the polymer layers were compressed and bridging was reduced. Such enhancements were reduced as the cation was changed from K(+) to Na(+) to Cs(+).