PET/PEN/DBS共混体系结构与形貌的研究

共混是改善聚合物性能的一种简单而又行之有效的方法,PET和PEN均为结晶性聚酯,由于PEN合成原料的影响,致使PEN的价格较高,但性能比PET优良,通过二者的共混,既可以提高PET的性能,又可以降低PEN成本,有关PET／PEN共混体系的研究已引起人们的关注,而对于共混体系结晶形态和结晶条件的研究较少,由于成核剂能够提高结晶速率,减小球晶尺寸,因此本文对PET／PEN／DBS共混体系中,组分组成的影响及不同结晶条件下共混物的结晶形貌进行研究。     

聚丙烯—聚对苯二甲酸乙二酯共混物的扫描电镜观察(Ⅱ)

使用扫描电镜和化学蚀刻的方法研究了聚丙烯(PP)和聚对苯二甲酸乙二酯(PET)共混物(PP:PET:9:1)在不同温度结晶时的形态结构,并与在相应条件下结晶的纯PP样品作比较。结果表明:(1)纯PP在0℃结晶时没有观察到明显的球晶,部分区域呈树枝晶,在30℃以上结晶时呈三类不同形态球晶;在0—140℃范围结晶的PP—PET共混物中都没有观察到第三类球晶和树枝晶。(2)在0—140℃温度下结晶的共混物中两组份互不相溶,PET都是以直径为1—5μ的小球分散在PP连续相的球晶内和球晶之间;PET的加入使PP球晶的尺寸比在相应条件结晶的纯PP球晶小,同时球晶的大小也随结晶温度降低而变小;PET小球与PP连续相之间存在着易受蚀刻的界面层。     

PET/LCP反应性共混物的非等温结晶动力学

采用DSC方法研究了聚对苯二甲酸乙二酯 (PET)和热致性液晶共聚酯 6 0PHB PET (LCP)体系在少量扩链剂双 (2 唑啉 ) (BOZ)存在下形成的反应性共混物的非等温结晶动力学 .结果表明反应性共混物的Avrami指数均在 3 0～ 4 5之间 ,BOZ的加入使反应共混物中PET组分的结晶速率降低 ;表明BOZ对酯交换的促进作用 ,使所生成的共聚酯中PET嵌段的数均序列长度变短 ,而使结晶在某种程度上较为困难 ,但对体系的成核和结晶生长机理无明显影响 .结果还表明 ,随冷却速率的增大结晶峰向低温方向移动     

PET/PC共混体系的酯交换反应对其高压结晶行为的影响

利用转矩流变仪、DSC、SEM及WAXD等表征手段研究了PET/PC共混体系的酯交换反应对其高压结晶行为的影响.SEM观察表明,PET和PC熔混时的酯交换反应有利于PET/PC体系在高压结晶时生成厚度较大的伸直链晶体,且可以促进其高压下酯交换反应的发生.楔形伸直链晶体和弯曲伸直链晶体的存在证明链滑移扩散和酯交换反应两种机制对体系中聚酯伸直链晶体的增厚有贡献.拟合分峰法和War-ren-Averbach傅里叶分析法的计算结果表明,随PET/PC体系熔混时酯交换反应程度的增加,高压结晶共混物的结晶度降低,PET的平均微晶尺寸增大,点阵畸变平均值则减小,而微晶尺寸分布变宽.提出了在共聚物组分都具备结晶能力时,结晶诱导化学反应和化学反应诱导结晶两种过程在一定条件下可同时发生的观点.     

苯乙烯—丙烯酸钠共聚物改性PET结晶行为的研究

本文用DSC和FT-IR方法研究了PET/苯乙烯-丙烯酸钠共聚物共混体系的相溶性、等温结晶动力学、组成、温度等因素对结晶速率、结晶度等结晶行为的影响,并初步探讨了离聚物对PET的作用。     

PC/PET/EPDM共混体系的结晶与熔融行为

本文用解偏振光法与DSC法分别测定并研究了PC/PET/EPDM共混体系的结晶速度、结晶度、Avrami指数(n)和熔融温度及其影响因素,共混物中PET的结晶速度、结晶度均随PC含量增加而下降;EPDM用量不超过10%时,可提高PET的结晶速度,但不影响结晶度和成核与增长方式,n值不变。当EPDM为5%时,结晶速度呈现极大值。经退火处理的共混物呈现熔融双峰,PC量增加,高温熔融峰略移向高温方向;热处理温度升高或时间延长,则低温熔融峰移向高温方向。     

聚对苯二甲酸乙二酯的结晶性能研究——V.合成树脂用的催化剂的影响

用酯交换法合成了二个不同催化剂系列的聚对苯二甲酸乙二酯(PET),并用DSC研究了催化剂对PET结晶性能的影响。以过冷程度、过热程度、熔体结晶峰等表征它们的结晶性能。结果表明:催化剂中金属元素的电负性(或lgβ_1)不仅与其催化活性有关,而且在一定程度上影响PET的结晶,可能是催化剂中金属离子的存在加速了结晶的成核速度。     

PET/PEN/DBS共混物非等温结晶动力学研究

采用DSC方法, 用修正的Avrami, Ozawa, Ziabicki宏观动力学模型描述PET/PEN/DBS[PET: 聚对苯二甲酸乙二醇酯; PEN: 聚2,6-萘二甲酸乙二醇酯; DBS: 1,3∶2,4-二(亚苄基)-D山梨醇]共混物的非等温熔融结晶过程, 研究结果表明, 修正的Avrami模型能很好地描述此共混物非等温结晶过程. 冷却速率在5-20 ℃/min范围内, Ozawa方程能很好地描述初期结晶过程, 但结晶后期由于忽略次级结晶而不适宜. 由Ziabicki结晶动力学参数可知, 该共混物的结晶随着成核剂DBS含量的增加而降低, 结晶速率随着成核剂DBS含量的增加而提高. 在非等温结晶条件下, 共混物结晶同时受到冷却速率和共混物组成的影响, 与共混物非等温结晶过程的有效能垒分析结果基本一致.     

PET和PBT在半熔态等温结晶形成单晶的研究

聚对苯二甲酸乙二醇酯(PET)和聚对苯二甲酸丁二醇酯(PBT)都是重要的工程塑料,有关PET和PBT的形态结构已研究了很多。一般认为,PET和PBT在玻璃化温度以上,熔点以下的温度范围内都可以结晶,且大部分都形成球晶结构。然而,PET和PBT     

用DSC研究阻燃PET的结晶性和结晶动力学

<正> 聚对苯二甲酸乙二酯(PET)是一种熔点较高的结晶性聚合物,其结晶性和结晶动力学已得到了广泛的研究。我们最近合成的一种含磷聚合物(或齐聚物)聚苯基磷酸二苯砜酯(PSPPP),可作为PET纺丝较为理想的阻燃剂。当PET中添加5wt％的这种阻燃剂时,其极限氧指数可达到30。然而,有关这种阻燃剂的加入对PET结晶特性的影响方面的研究鲜见报道。本文用DSC方法研究了阻燃剂添加量的多少对PET结晶程度的影响,并且对纺制阻燃PET纤维的实用添加量5wt％的试样进行了结晶动力学研究。     

Liquid crystal fibers produced by using electrospinning technique

This paper investigates the electrospinning process of liquid crystalline polysiloxane with cholesterol as side chain (LCPC) and the influence on the morphology of the formed fibers by mixing LCPC solution with small-molecule liquid crystal, triethylamine, and poly(ethylene oxide)(PEO). The mechanical properties of single fibers were characterized by a novel approach. The results indicate that, under appropriate conditions, fine liquid crystal fibers can be obtained and the preferable mechanical properties can be achieved, especially after annealing. WXRD was used to investigate the orientation of polymer molecules in the formed fibers, suggesting that strong interaction exists between LCPC and PEO molecule in the resulting composite fibers, and polymer molecular tends to arrange regularly during electrospinning processing. This research work provides a new and facile method of using electrospinning to prepare liquid crystal fibers, which would be useful for designing the related high-performance materials.     

Airbrush Formation of Liquid Crystal/Polymer Fibers

A homogeneous solution of a low‐molecular‐weight liquid crystal and a polymer spontaneously phase separates during airbrushing to form uniform fibers with a fluid liquid‐crystal core surrounded by a solid polymer sheath. This structure forms because it effectively minimizes the interfacial energy of the phase‐separated components while minimizing the elastic energy of the liquid‐crystal core. These fibers incorporate the sensitive stimuli response of liquid crystals while maintaining the structural integrity, flexibility, and large surface‐area‐to‐volume ratios inherent in fibers. We demonstrate the electro‐ and thermo‐optical response of the resulting fibers. They may find use as biological and chemical sensors. The resulting fibers have the potential to shape the future of flexible/wearable electronics and sensors.     

Morphology Tuning of Electrospun Liquid Crystal/Polymer Fibers

This paper elucidates the means to control precisely the morphology of electrospun liquid crystal/polymer fibers formed by phase separation. The relative humidity, solution parameters (concentration, solvent), and the process parameter (feed rate) were varied systematically. We show that the morphology of the phase‐separated liquid crystal can be continuously tuned from capsules to uniform fibers with systematic formation of beads‐on‐a‐string structured fibers in the intermediate ranges. In all cases, the polymer forms a sheath around a liquid‐crystal (LC) core. The width of the polymer sheath and the diameter of the LC core increase with increasing feed rates. This is similar to the results obtained by coaxial electrospinning. Because these fibers retain the responsive properties of liquid crystals and because of their large surface area, they have potential applications as thermo‐, chemo‐, and biosensors. Because the size and shape of the liquid‐crystal domains will have a profound effect on the performance of the fibers, our ability to precisely control morphology will be crucial in developing these applications.     

Mechanochromic Photonic‐Crystal Fibers Based on Continuous Sheets of Aligned Carbon Nanotubes

A new family of mechanochromic photonic‐crystal fibers exhibits tunable structural colors under stretching. This novel mechanochromic fiber is prepared by depositing polymer microspheres onto a continuous aligned‐carbon‐nanotube sheet that has been wound on an elastic poly(dimethylsiloxane) fiber, followed by further embedding in poly(dimethylsiloxane). The color of the fiber can be tuned by varying the size and the center‐to‐center distance of the polymer spheres. It further experiences reversible and rapid multicolor changes during the stretch and release processes, for example, between red, green, and blue. Both the high sensitivity and stability were maintained after 1000 deformation cycles. These elastic photonic‐crystal fibers were woven into patterns and smart fabrics for various display and sensing applications.     

Colloid-templated multisectional porous polymeric fibers

A fabrication method for porous polymeric fibers (PPFs) is reported. We show that a multisectional colloidal crystal can be assembled within a microcapillary by alternating dipping into colloidal solutions of varying size. Subsequent infiltration with curable polymer and washing with suitable solvents results in porous fibers with a cylindrical cross section. Along the length of the fiber, alternating sections of controlled length, pore size, and pore size distribution exist. These fibers present interesting materials for neural scaffolding, catalysis, and possibly photonics if produced with a high degree of crystallinity. The surface pores and bulk porosity of the fibers are characterized by variable-pressure scanning electron microscopy (vp-SEM). Careful analysis shows that the surface pores vary with the colloidal template diameter and polymer infiltration time.     

Liquid crystal functionalization of electrospun polymer fibers

A recently introduced new branch of applied polymer science is the production of highly functional and responsive fiber mats by means of electrospinning polymers that include liquid crystals. The liquid crystal, which provides the responsiveness, is most often contained inside fibers of core‐sheath geometry, produced via coaxial electrospinning, but it may also be inherent to the polymer itself, for example, in case of liquid crystal elastomers. The first experiments served as proof of concept and to elucidate the basic behavior of the liquid crystal in the fibers, and the field is now ripe for more applied research targeting novel devices, in particular in the realm of wearable technology. In this perspective, we provide a bird's eye view of the current state of the art of liquid crystal electrospinning, as well as of some relevant recent developments in the general electrospinning and liquid crystal research areas, allowing us to sketch a picture of where this young research field and its applications may be heading in the next few years. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B Polym. Phys. 2013, 51, 855–867     

Orientation processes in cellulose acetate under the action of dimethyl sulfoxide vapor

Spontaneous variation of the linear size (elongation-contraction) of acetate fibers in a vapor of dimethyl sulfoxide, which is a mesophasogenic solvent, i.e., a solvent forming a liquid crystal phase with the polymer, is described. A mechanism of the interaction of the polymer with the solvent vapor is suggested.     

一缩二乙二醇二甲基丙烯酸酯接枝真丝的结构

通过电子扫描电镜 (SEM)、红外光谱 (IR)、双折射、X 射线衍射及氨基酸分析等手段 ,研究了真丝用一缩二乙二醇二甲基丙烯酸酯 (P 2 )接枝后其结构与接枝率之间的关系 .氨基酸分析结果表明P 2接枝主要在真丝大分子中酪氨酸、丝氨酸、组氨酸和精氨酸的NH2 、OH和—NH—活性基团上 .通过X 射线衍射分析 ,P 2接枝并不直接影响结晶区 ,但引起分子取向的下降 ,接枝后真丝双折射下降说明接枝后因大分子取向度下降 ,接枝真丝的红外光谱显示出真丝具有 β折迭结构和P 2高聚物的结构特征峰 ,从而说明P 2接枝在纤维的无定型区内部进行 .当接枝率大于 35 %时 ,纤维的表面覆盖了一层高聚物 (P 2 ) ,并且纤维的横截面表现出明显的分纤现象 ,接枝真丝的红外光谱表明了纤维与P 2重叠吸收峰 ,说明了P 2在丝纤维内部接枝聚合 .     

Study on the Effect of Uniaxial Elongational Flow on Polyamide Based Nanocomposites

This work focuses on the study of uniaxial elongational flow and its effects on morphology and stiffness of polyamide-6 based nanocomposites prepared by melt compounding. The elongational flow characterization was realized by converging flow method and fiber spinning technique. During the haul-off tests, fibers of the neat polyamide-6 and the hybrids (at 3 and 6 wt% of silicate) were collected at different draw ratios. Mechanical properties of the produced fibers were investigated and correlated to their nanostructure through analytical techniques sensitive to different aspects of morphology, such as DSC and TEM analysis. Rheological results, obtained with a capillary rheometer, indicate that the shear viscosity decreases with the silicate loading, while the extentional viscosity increases. Moreover, the presence of the silicate in polymer matrix leads to enhancements of draw-down force and reduction of the breaking draw ratio. In hybrid fibers an enhanced degree of exfoliation of the filler was observed upon drawing. Moreover, DSC analyses suggest that the crystalline structure of the fibers is the result of two opposite effects: the presence of the silicate which stabilizes the γ form and the drawing which promotes the α crystal phase. The degree of silicate exfoliation and the amount of the different crystal phases strongly affect the tensile properties of the fibers.     

Investigation of the Orientation in Composite Fibers of Polycarbonate with Multiwalled Carbon Nanotubes by Raman Microscopy

The superior association of the inherent good mechanical and electrical properties makes carbon nanotubes (CNT) exceptionally interesting for the production of composite fibers of thermoplastic polymers with CNT. Alignment of the CNT in the polymer fiber is important for improved mechanical properties. Especially the production of fibers makes it necessary to get a controlled orientation and/or alignment of the CNT. We applied transmission electron microscopy (TEM) and polarized Raman microscopy to quantify multiwalled carbon nanotubes (MWNT) orientation, alignment and crystallinity in polycarbonate (PC). The evaluation of the Raman measurements provided an improved alignment orientation of the MWNT in the fibers with increasing take-up velocity during melt spinning and that the crystal structure of the MWNT is not changed through melt spinning.