Morphology studies of poly(ethylene terephthalate)/silica nanocomposites

Poly(ethylene terephthalate)/silica nanocomposites have been prepared through in situ polymerization. The morphology was investigated by atomic force microscopy in the tapping mode and scanning electron microscope. The interface morphological structure of the poly(ethylene terephthalate)/silica nanocomposites strongly depends on the ratio of silica in the matrix. When silica weight fraction is lower than 3 wt%, the system consists of aggregated silica particles dispersed in the organic matrix; beyond this concentration, the structure is co-continuous with that of the organic matrix. Surface of poly(ethylene terephthalate) was smooth; while nanocomposites were rough, there are good interfacial adhesion and compatibility between the polymer matrix and the nanofillers.     

Preparation and characterization of poly(methyl methacrylate) beads

The phase behavior of Poly(ethylene terephthalate)/Poly(ethylene‐2,6‐naphthalate)/Poly(ethylene terephthalate‐co‐ethylene‐2,6‐naphthalate) (PET/PEN/P(ET‐co‐EN)) ternary blends in molten state was evaluated from differential scanning calorimetry (DSC) and NMR results as well as optical microscopic observations. Copolymer of ethylene terephthalate and ethylene‐2,6‐naphthalate was prepared by a condensation polymerization, which was a random copolymer with an intrinsic viscosity (IV) of 0.3 dL/g. The phase diagram of the ternary blends revealed that the miscibility of ternary blends in molten state was dependent on the fraction of P(ET‐co‐EN) in the blends and holding time of the blends at high temperatures above 280°C. With increase in the holding time, the fraction of copolymer in the blends necessary to induce the immiscible to miscible transition decreased. For the blends with longer holding time at 280°C, the phase diagram in molten state was irreversible against the temperature, although a reversibility was found for the blends with short holding time of 1 min at 280°C. The irreversibility of phase behavior was not explained simply by the increase of copolymer content produced during heat treatment. Complex irreversible physical and chemical interactions between components and change of phase structure of the blend in the molten state might influence on the irreversibility. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Toughening and Compatibilization of Acrylonitrile–Butadiene–Styrene/Poly (Ethylene Terephthalate) Blends Using an Oxazoline-Functionalized Impact Modifier

An oxazoline-functionalized core–shell impact modifier was synthesized between aminoethanol and acrylonitrile/butadiene/styrene high rubber powder. According to the Fourier transform infrared spectroscopy test, the nitrile groups were partially converted into oxazoline groups successfully. The oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was used as an impact modifier for acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends. The differential scanning calorimeter and rheological tests demonstrated that poly(ethylene terephthalate) was partially miscible with acrylonitrile–butadiene–styrene, because the oxazoline groups of oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder reacted with the end groups of poly(ethylene terephthalate). The results of scanning electron microscopy indicated that the morphology of acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends with proper oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder content was improved significantly. The best mechanical properties were achieved, When 6 wt% oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was added into acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends.     

Chemical structure change of a KRF‐laser irradiated PET fiber surface

Laser ablation of a poly(ethylene terephthalate) fabric with an excimer laser beam (248 nm) was analyzed by color tests, and the chemical structure change of the surface was studied. This analysis suggests the possibility of the formation of both OH and CHO groups on the poly(ethylene terephthalate) surface. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2027–2031, 1999     

Influence of short glass fiber reinforcement on the morphology development and mechanical properties of PET/HDPE blends

Poly(ethylene‐terephthalate) (PET)—high density polyethylene (HDPE) blends with varying component ratios and with or without short glass fiber reinforcement (10 gv%) were prepared. The morphology of the blends was studied by scanning electron microscopy (SEM) and optical microscopy. The interfacial shear strength between PET and HDPE as well as between the polymers and the glass fiber was determined with microbond testing. The static mechanical properties were defined with tensile tests and Charpy impact tests, while the dynamic mechanical properties with DMTA. In blends that do not contain glass fibers, the co‐continuous structure formed in the vicinity of phase inversion increased both the static tensile modulus as well as the impact strength compared to the mechanical properties of polymers. Based on the observations simple morphological models were set up, with the help of which the change in the mechanical properties of blends of different composition can be explained. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

The role of specific interactions and transreactions on the compatibility of polyester ionomers with poly(ethylene terephthalate) and nylon 6,6

The compatibility of polyester ionomers with polar polymers (i.e., poly(ethylene terephthalate) and nylon 6,6) is under investigation for their potential use as minor component compatibilizers. Binary blends have been prepared by both solution and melt-mixed methods to determine the effect of melt-processing on blend compatibility. The effect of the sulfonate group and counterion type on compatibility was evaluated by blending sulfonated and nonsulfonated forms of the amorphous polyester ionomer with both nylon 6,6 and poly(ethylene terephthalate). The melting point and phase behavior of the blends were determined by differential scanning calorimetry (DSC) and environmental scanning electron microscopy (ESEM), respectively. A comparison of the melting behavior between the melt and solution blends suggests compatibility due to specific interactions for the ionomer/nylon 6,6 blends, and transesterification for the ionomer/poly(ethylene terephthalate) blends. The phase morphology of the melt blends is consistent with the results obtained by DSC analysis.     

Confocal Scanning Laser Microscope Image of Gradient Structure Formed in an Acrylate Copolymer/Fluoro-copolymer Blend

Thin films of poly(2-ethylhexyl acrylate-co-acrylic acid-co-vinyl acetate)/poly(vinylidene fluoride-co-hexafluoro acetone) [P(2EHA-AA-VAc)/P(VDF-HFA)] of 30/70 (by weight) blends without and with addition of 2 wt% fine silica gel were prepared on poly(ethylene terephthalate) (PET) from 20 wt% THF solution. Gradient domain morphology formed in the 30/70 blend was observed with a confocal scanning laser microscope (CSLM). Separate domains composed of P(2EHA-AA-VAc) phase were found in P(VDF-HFA) matrix at various levels of increasing depth with increasing domain size. Thus, CSLM is quite effective in morphological observation of the gradient structure formed in polymer blends, provided the blends are transparent.     

Enhanced dyeability of poly(ethylene terephthalate)/organoclay nanocomposite filaments

This study deals with the generation of poly(ethylene terephthalate)/organoclay nanocomposite filaments by the melt‐spinning method and with the investigation of their morphological and dyeing properties. Different montmorillonite types of clay (Resadiye and Rockwood) were modified using different intercalating agents, and poly(ethylene terephthalate) nanocomposite filaments containing 0.5 and 1 wt% organoclays were prepared. Afterwards, the filaments were dyed with two disperse dyes (Setapers Red P2G and Setapers Blue TFBL‐NEW) at different temperatures (100, 110, and 120 °C) in the absence/presence of a carrier. Organoclays and poly(ethylene terephthalate)/organoclay nanocomposites showed an increased d‐spacing between clay layers. Irrespective of clay and surfactant type, poly(ethylene terephthalate)/organoclay nanocomposite filaments dyed at 120 °C in the presence of only a very small amount of carrier showed appreciable dyeability in comparison with neat poly(ethylene terephthalate). The dyeability of the organoclay‐containing poly(ethylene terephthalate) samples was found to be better in spite of having increased degrees of crystallinity. Moreover, the colour fastness properties of the clay‐containing samples were not affected adversely.     

Liquid-induced crystallization of poly(ethylene terephthalate)

Amorphous unoriented poly(ethylene terephthalate) was crystallized at 25°C by various organic liquids. The crystalliznity induced in the amorphous polymer was measured by differential scanning calorimetry and infrared spectroscopy. The ability of liquids to interact with and induced crystallinity in the amorphous polymer was classified on the basis of their solubility parameters. Measurements of the density of liquid-crystallized 0.8-mil films of poly(ethylene terephthalate) indicated the presence of extensive internal voids in the semicrystalline polymer matrix. Comparison of differential scanning calorimetric thermograms and infared spectra of heat-crystalized and liquid-crystallized polymer indicated significant differences in the polymer morphologies induced by the two crystallization processes.     

Stress–relaxation properties of segmented polyurethane rubbers

Stress–relaxation behavior of polyurethane elastomers based on two hydroxyl-terminated polyesters: poly(ethylene adipate) and poly(ethylene maleate) was studied. In addition, a polyester-diol consisting of poly(ethylene adipate) and oligo(ethylene terephthalate) blocks, a number of low-molecular-weight diols as chain extenders, and 4,4′-diphenylmethane diisocyanate (MDI) were determined. The elastomers were crosslinked by an excess of MDI and had stiff segments of differing chemical structure and length. Stress–relaxation properties of the elastomers conformed with the three-component Maxwell model, with negligibly small contribution from the fastest relaxation process. The influence of crosslinking density, chemical structure, and stiff segment content on the relative relaxation speed and the parameters of the slow and fast relaxation processes, was examined. The elucidation of the results was based on the morphological models of segmented polyurethanes.     

Effect of alkali on filaments of poly(ethylene terephthalate) and its copolyesters

The alkali hydrolysis of poly(ethylene terephthalate), anionic copolymer of poly(ethylene terephthalate), and block copolymer of poly(ethylene terephthalate)–poly(ethylene glycol) is investigated under a variety of conditions of alkali concentration in aqueous bath, additives, time, and temperature. Measurements of loss in weight, linear density, breaking load, tenacity, elongation to break apart from intrinsic viscosity, fiber density, COOH-end group content, diameter of filaments, and scanning electron micrographs have been analyzed to identify the differences in the action of alkali on these polymer materials.     

Effects of Blending Conditions and Catalyst Concentration on the Structural,Thermal and Morphological Properties of Polycarbonate/Poly (Ethylene Terephthalate) Blends

The effects of mixing conditions and transesterification catalyst concentration on the structural, thermal and morphological properties of a 50/50 polycarbonate (PC)/poly (ethylene terephthalate) (PET) system were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and by solubility measurements. From the increase in the solubility of the blends in dichloromethane and the decrease of their degree of crystallinity, it was concluded that on increasing the mixing time and the catalyst concentration, transesterification becomes more important. Thermal analysis revealed also a noticeable increase of the crystallization temperature and a slight decrease of the melting temperature. These results suggest that when transesterification occurs extensively, the crystallization tendency declines progressively until finally a completely soluble material is obtained as revealed by solubility measurements.     

Poly(ethylene terephthalate)/polypropylene microfibrillar composites. III. Structural development of poly(ethylene terephthalate) microfibers

Poly(ethylene terephthalate) was extruded, solid‐state‐drawn, and annealed to simulate the structure of poly(ethylene terephthalate) microfibers in a poly(ethylene terephthalate)/polypropylene blend. Differential scanning calorimetry and wide‐angle X‐ray scattering analyses were conducted to study the structural development of the poly(ethylene terephthalate) extrudates at different processing stages. The as‐extruded extrudate had a low crystallinity (～ 10%) and a generally random texture. After cold drawing, the extrudate exhibited a strong molecular alignment along the drawing direction, and there was a crystallinity gain of about 25% that was generally independent of the strain rates used (0.0167–1.67 s^?1). 2θ scans showed that the strain‐induced crystals were less distinctive than those from melt crystallization. During drawing above the glass‐transition temperature, the structural development was more dependent on the strain rate. At low strain rates, the extrudate was in a state of flow drawing. The resultant crystallinity hardly changed, and the texture remained generally random. At high strain rates, strain‐induced crystallization occurred, and the crystallinity gain was similar to that in cold drawing. Thermally agitated short‐range diffusion of the oriented crystalline molecules was possible, and the resultant crystal structure became more comparable to that from melt crystallization. Annealing around 200°C further increased the crystallinity of the drawn extrudates but had little effect on the texture. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 137–146, 2007     

Radiation grafting of poly(ethylene terephthalate) (PET) fibre,II. Hydrolysis of grafted poly(vinyl acetate) to poly(vinyl alcohol)

Poly(ethylene terephthalate) fibres grafted with poly(vinyl acetate) by γ-radiation were hydrolysed under alkaline and acidic conditions in order to obtain poly(ethylene terephthalate)-graft-poly(vinyl alcohol) fibres. In alkaline media poly(ethylene terephthalate) degraded without appreciable conversion of acetate to hydroxyl groups. During acid hydrolysis no change in tensile properties of the fibres was observed up to an extent of 50% conversion of acetate to hydroxyl groups. Further change in the tensile strength and the elongation at break was attributed partly to the grafted poly(vinyl acetate)/poly(vinyl alcohol) balance and partly to the loss due to degradation of the fibres.     

Influence of the Addition of Tetrabutyl Orthotitanate on the Rheological,Mechanical, Thermal,and Morphological Properties of Polycarbonate/Poly(Ethylene terephthalate) Blends

The effects of the incorporation of tetrabutyl orthotitanate (TBOT) on the mechanical, thermal, rheological, and morphological properties of polycarbonate (PC)/ poly(ethylene terephthalate) PET blends were investigated. Blends were prepared using a screw extrusion with TBOT's rates varying from 0 to 0.25 phr. Rheological and mechanical investigations showed that the blends properties decreased by chain scissions induced by the degradation of PET and by volatile products release. Differential scanning calorimetry (DSC) revealed that the crystallinity of PET in PC/PET blends is affected by many parameters and does not depend only on PC and TBOT concentrations whereas dynamic mechanical analysis (DMA) and scanning electron microscopy (SEM) support the occurrence of a little compatibilization.     

Sequence distribution and crystal structure of poly(ethylene/trimethylene terephthalate) copolyesters

The sequence distribution and the crystal structure of copolyesters synthesized from ethylene glycol, 1,3-propanediol, and dimethyl terephthalate with different molar volume ratios were investigated in this study. The triad sequence probabilities of ethylene/trimethylene terephthalate were characterized from the aromatic quaternary carbons by ¹³C NMR. The composition of the copolyesters was determined from the aromatic quaternary carbons by ¹³C NMR, and the methylene protons by ¹H NMR. Results show that 1,3-propanediol reacted faster with terephthalic acid in copolyester polymerization than ethylene glycol. The difference in monomer reactivity is significant in the polymerization. Although the constitutional units revealed a random distribution in the molecular chain by ¹³C NMR, crystallites formed across the full range of ethylene glycol/1,3-propanediol composition by use of differential scanning calorimetry, a hot stage polarizing microscope, and a wide angle X-ray diffraction method. The WAXD deconvolution results show that the major constitutional repeating unit in the molecular chain dominates the crystal structure as a host crystal. The crystal structure was examined by a scanning electron microscope after a solvent etching. Photomicrographs show that the random distribution of the third constitutional unit in the molecular chain of copolyester significantly disturbs the host crystal formation and lamellar orientation.     

液晶离聚物在ABS/PBT共混体系中的增容研究

合成了一种含有磺酸基的液晶离聚物（LCI）,并研究了LCI作为相容剂对丙烯腈-丁二烯-苯乙烯三元共聚物/聚对苯二甲酸丁二醇酯（ABS/PBT）共混体系力学性能的影响。采用扫描电镜（SEM）、差示扫描量热仪（DSC）和热失重（TGA）分析对ABS/PBT/LCI共混物的热性能、微观形态和相容性进行了研究。研究结果表明LCI的加入,改善了二者的相容性,从而提高了共混物的拉伸强度、断裂伸长率以及缺口冲击强度。     

Thermomechanical processing environment and morphology development of a thermotropic polymer liquid crystal

We have studied a longitudinal polymer liquid crystal consisting of poly(ethylene terephthalate) (PET) and p‐hydroxybenzoic acid, namely PET/0.6PHB, where 0.6 is the mole fraction of the second component. The material was injection molded with systematic variations of the melt and mold temperatures and injection flow rate using design of experiments based on a Taguchi orthogonal array. Thermomechanical environment defined by local melt temperatures and shear rates and stresses imposed during processing was estimated by computer simulations of the mold‐filling phase. The morphology of the moldings was characterized by optical and scanning electronic microscopy, wide‐ and small‐angle X‐ray scattering, and differential scanning calorimetry. An analysis of variance approach identified the significant processing variables and their contributions to variations of morphological parameters. The processing environment affects strongly the melt viscosity, and there is a strong thermo‐mechanical coupling. The result is a complex multilaminated and hierarchical microstructure, whose morphological features are very sensitive to the processing conditions. Relationships between local thermomechanical variables (rather than global ones) and the morphological parameters are established. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

In situ microfibrillar blends and composites of polypropylene and poly (ethylene terephthalate): Morphology and thermal properties

Microfibrillar blends were prepared from polypropylene and poly (ethylene terephthalate) by extrusion followed by cold drawing. The draw ratio employed had a prominent effect on the aspect ratio of the microfibrils produced, as revealed by scanning electron microscopy. The subsequent isotropization step between the T_m of the polymers created microfibrillar composites with randomly oriented short microfibrils of poly (ethylene terephthalate). The X ray diffraction patterns of the microfibrillar blends were different from those of corresponding composites although the polypropylene phase in both exhibited predominantly the presence of α crystallites. The crystallization of the polypropylene phase was affected by the orientation and diameter of the poly (ethylene terephthalate) microfibrils. The short microfibrils in the microfibrillar composites were not effectual in hastening the crystallization of polypropylene. The thermal decomposition studies revealed the capability of microfibrillar blends to delay the degradation better than the microfibrillar composites.     

Network formation in poly(ethylene terephthalate) by thermooxidative degradation

Gelation of poly(ethylene terephthalate) by heating at 263°–300°C was investigated. Under nitrogen flow, crosslinks were scarcely formed. However in air, degradation and crosslinking were common, and these were accelerated by purging gaseous and sublimable degradation products out of the system with a stream of air. The main component of the sublimate was terephthalic acid. Infusible and insoluble gel was treated with methanol at 260°C, and then the methanolysis products were separated into two parts. The methanol-insoluble part exhibited a polyene structure with ester groups, and the methanol-soluble part contained dimethyl terephthalate, ethylene glycol, and some 1,2,4-butanetriol. To clarify the relation between the crosslinking and the formation of vinyl ester groups, the degradation of vinyl methyl terephthalate was studied. Thermoxidative degradation of linear polyesters other than poly(ethylene terephthalate) was also studied. Poly(ethylene isophthalate) and poly(ethylene sebacate) were easily gelated. However, poly(trimethylene terephthalate) and poly(neopentyl terephthalate) were scarcely gelated. The primary reaction leading to crosslinking is assumed as follows. At first, the random scission of polyester chain may take place forming carboxylic acids, vinyl esters, aldehydes, etc. After accumulation of vinyl esters to some extent, vinyl polymerization of the esters takes place and network structures are formed.