乙烯-甲基丙烯酸共聚物离聚体在聚对苯二甲酸乙二酯中的相分离行为

聚对苯二甲酸乙二酯(PET)结晶速度很慢,通常加入成核剂来提高结晶速度。从专利文献来看,以离子聚合物为成核剂的例子也是很多的。离子聚合物与小分子成核剂的显著差别是:离子聚合物有一个很长的碳氢主链,其侧基为酸基,酸基被部分或全部地中和成盐。很明显,离子聚合物不象小分子成核剂那样能很好地分散在PET基体中,而是以独立的相存在。作为PET体系系列研究的继续,本文报道了离子聚合物Surlyn在PET中的相分离行为。     

聚酯／改性共聚酯共混体系的相分离及其共混纤维的结构和性能

本文研究聚酯(PET)和含3.5-二甲酸苯磺酸钠(SIPM)结构单元的改性共聚酯(PEI)的共混体系。差示扫描量热分析,X射线衍射分析,染色后的透射和扫描电镜照片等均表明该体系是一个热力学不相溶的体系。在加工成形过程中,特别是在结晶过程中,富PEI相中的SIPM结构单元被排斥在晶格之外形成集簇形态,利用这种相分离的结构形态以及改性共聚酯优先水解的机理,PET/PEI共混纤维经碱水解处理后可制得微孔型的高吸水吸湿纤维。本文讨论了相分离结构对该微孔型纤维的微孔尺寸分布,吸湿保水性能以及纤维力学性能的影响。     

In‐situ microfibrillar PET/iPP blend via slit die extrusion,hot stretching,and quenching: Influence of hot stretch ratio on morphology,crystallization, and crystal structure of iPP at a fixed PET concentration

The in situ microfibrillar blend of poly(ethylene terephthalate) (PET)/isotactic polypropylene (iPP) was fabricated through a slit die extrusion, hot stretch, and quenching process. The morphological observation indicates that while the unstretched blend appears to be a common incompatible morphology, the hot stretched blends present PET in situ fibers whose characteristics, such as diameter and aspect ratio, are dependent on the hot stretching ratio (HSR). When the HSR is low, the elongated dispersed phase particles are not uniform at all. As the HSR is increased to 16.1, well‐defined PET microfibers were generated in situ, whose diameter is rather uniform and is around 0.6 ～ 0.9 μm. The presence of the PET phase shows significant nucleation ability for crystallization of iPP. Higher HSR corresponds to faster crystallization of the iPP matrix, while as HSR is high up to a certain level, its variation has little influence on the onset and maximum crystallization temperatures of the iPP matrix during cooling from melt. Optical microscopy observation reveals that transcrystalline layers form in the microfibrillar blend, in which the PET microfibers play as the center row nuclei. In the as‐stretched microfibrillar blends, small‐angle X‐ray scattering measurements show that matrix iPP lamellar crystals have the same orientation as PET lamella. The long period of lamellar crystals of iPP is not affected by the presence of PET micofibers. Wide‐angle X‐ray scattering reveals that the β phase of iPP is obtained in the as‐stretched blends, whose concentration increases with the increase of the HSR. This suggests that finer PET microfibers can promote the occurrence of the β phase. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4095–4106, 2004     

Morphology and properties of isotactic polypropylene/poly(ethylene terephthalate) in situ microfibrillar reinforced blends: Influence of viscosity ratio

In situ microfibrillar reinforced blends based on blends of isotactic polypropylene (iPP) and poly(ethylene terephthalate) (PET) were successfully prepared by a “slit extrusion-hot stretching-quenching” process. Four types of iPP with different apparent viscosity were utilized to investigate the effect of viscosity ratio on the morphology and mechanical properties of PET/iPP microfibrillar blend. The morphological observation shows that the viscosity ratio is closely associated to the size of dispersed phase droplets in the original blends, and accordingly greatly affects the microfibrillation of PET. Lower viscosity ratio is favorable to formation of smaller and more uniform dispersed phase particles, thus leading to finer microfibrils with narrower diameter distribution. Addition of a compatibilizer, poly propylene-grafted-glycidyl methacrylate (PP-g-GMA), can increase the viscosity ratio and decrease the interfacial tension between PET and iPP, which tends to decrease the size of PET phase in the unstretched blends. After stretched, the aspect ratio of PET microfibrils in the compatibilized blends is considerably reduced compared to the uncompatibilized ones. The lower viscosity ratio brought out higher mechanical properties of the microfibrillar blends. Compared to the uncompatibilized microfibrillar blends, the tensile, flexural strength and impact toughness of the compatibilized ones are all improved.     

PET/LDPE REACTIVE COMPATIBILIZATION THROUGH THE CARBAMATE FUNCTIONALIZED EPM

ABSTRACT

To investigate the effect of reactive compatibilization in the immiscible poly(ethylene terephthalate) (PET)/low-density polyethylene (LDPE) blend, ethylene-propylene copolymer-g-methacryloyl carbamate (MEPM) was prepared and used as a reactive compatibilizer. The inter-facial reaction of carbamate group in MEPM with OH/COOH in PET was confirmed by measuring the interfacial tension between the PET and LDPE using the breaking thread method. The two-step blending process strongly influenced the blend morphology at high concentration of the dispersed phase in the blend. The MEPM showed a discrepancy in the reactive compatibilization ability with a blend sequence in the blends of different dispersed phase concentration.     

Electrical conductivities of carbon nanotube-filled polycarbonate/polyester blends

Carbon nanotube (CNT)-filled polycarbonate (PC)/poly(butylene terephthalate) (PBT) and polycarbonate (PC)/poly(ethylene terephthalate) (PET) blends containing 1 wt% CNTs over a wide range of blend compositions were prepared by melt mixing in a torque rheometer to investigate the structure-electrical conductivity relationship. Field emission scanning electron microscopy was used to observe the blend morphology and the distribution of CNTs. The latter was compared with the thermodynamic predictions through the calculation of wetting coefficients. It was found that CNTs are selectively localized in the polyester phase and conductive blends can be obtained over the whole composition range (20 wt%, 50 wt% and 80 wt% PBT) for CNT-filled PC/PBT blends, while conductive CNT-filled PC/PET blends can only be obtained when PET is the continuous phase (50 wt%, 80 wt% PET). The dramatic difference in the electrical conductivity between the two types of CNT-filled PC/polyester blends at a low polyester content (20 wt%) was explained by the size difference of the dispersed phases on the basis of the transmission electron microscope micrographs.     

The effect of annealing on the crystallization of poly(ethylene terephthalate)/polycarbonate blends

The effect of annealing on the morphology and subsequent crystallization kinetics of poly (ethylene terephthalate)/polycarbonate blends have been investigated using differential scanning calorimetry (DSC), polarized light microscopy, and scanning electron microscopy (SEM). During annealing transesterification and phase coarsening occurred, and the final properties were compromizes between these two competing effects. Initially, the effect of phase separation dominated and the rate of cold crystallization of PET increased. Transesterification, however, became increasingly important and the rate of crystallization decreased progressively until finally the blend completely lost the ability to crystallize. At this stage in the reaction a single glass transition was observed and uniform glassy material observed in the SEM. The maximum crystallinity of the blend achieved on heating showed the same trend in first increasing and then decreasing with annealing time. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2129–2136, 2004     

Intimate blend of poly(ethylene terephthalate) and poly(ethylene 2,6‐naphthalate) via formation with and coalescence from their common inclusion compound with γ‐cyclodextrin

The experimental procedures to place poly(ethylene 2,6‐naphthalate) (PEN) guest molecules within γ‐cyclodextrin (γ‐CD) host molecules are described along with the subsequent verification of inclusion‐compound (IC) formation. In addition, the simultaneous complexing of PEN and poly(ethylene terephthalate) (PET) with γ‐CD to form their common IC is documented. Coalescence from their common γ‐CD IC generates an intimate blend of the PET and PEN polymers contained therein. Thermal analysis via differential scanning calorimetry reveals thermal behavior indicative of an intimate blend of PET and PEN. ¹H NMR analysis confirms that the intimate blending of PET and PEN achieved by coalescence from their common γ‐CD IC is not due to transesterification into a PET/PEN copolymer during thermal analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 139–148, 2003     

TRANSESTERIFICATION OF POLY(ETHYLENE TEREPHTHALATE) WITH POLY(ε-CAPROLACTONE)*

Transesterification of poly(ethylene terephthalate) (PET) with poly(ε-caprolactone) (PCL) was investigated bymeans of NMR spectroscopy, extraction experiments, differential scanning calorimetry (DSC) and phase contrast microscopy(PCM). The ~1H-NMR results show that transesterification takes place in the melt blends and leads to the formation of thePET-PCL copolyester with a chemical structure similar to ethylene terephthalate-ε-caprolactonc copolycster (TCL)synthesized directly from monomers. However, even in the blend that has been transesterified for 8 h, the random PET-PCLcopolyester, PET-PCL copolyester with long PET or long PCL segments and the unreacted PET and PCL homopolymersmay coexist. Due to the low mobility of PET and PCL chains and the high viscosity of the two macromolecules, thetransesterification proceeds with difficulty. Furthermore, PET is incompatible with PCL, the transesterification can onlyoccur at the interface or in the interfacial region between two phases, and finally the reaction can only reach a localequilibrium. These results indicate that in fact the transesterification in the melt blend between two incompatiblehomopolymers could not lead to the formation of completely random or typical block copolyesters.     

Solid state blending of poly(ethylene terephthalate) with polystyrene: Extent of PET amorphization and compositional effects on crystallizability

Polystyrene (PS) and poly(ethylene terephthalate) (PET) were blended together in the solid state via cryogenic mechanical attrition (CMA) and in the melt through conventional twin‐screw extrusion. CMA PS/PET blend morphologies were characterized both qualitatively and quantitatively through microscopy and thermal analysis. Specifically, CMA reduced the dispersed‐phase domain size and its distribution relative to simple melt extrusion, although not to the extent attained with added chemical compatibilizers. CMA also amorphized the PET phase and depressed the PET cold crystallization rate, which was measured by post‐CMA nonisothermal MDSC analysis. The PET amorphization efficiency and crystallizability for CMA PS/PET blends were the highest and lowest, respectively, at the PS/PET phase inversion. These concomitant phenomena are known to be caused by CMA‐induced PET crystal defect formation and subsequent entropic stabilization. Such behaviors are linked to the enhanced presence of an uncrystallizable rigid amorphous PET phase, and the weight fraction of this rigid amorphous fraction (RAF PET) was quantified and also maximized near the PS/PET phase inversion. Moreover, the increased compatibilization and amorphization efficiencies and reduced PET crystallizability were determined to be interdependent. These studies have verified that CMA of PET with PS is more efficient than extrusion due to the formation of nonequilibrium, metastable morphologies that can be more precisely controlled and better stabilized with an interesting, composition‐dependent interplay between PET crystallizability and the extent of PS/PET compatibilization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1348–1359, 2008