Optical Transmittance Thermal Analysis of the Poly(Ethylene Terephthalate) Foils

The optical transmittance of poly(ethylene terephthalate) foils has been investigated using the linear heating as well as the isothermal heating. It was found out that transmittance records obtained at linear heating show the crystallisation and melting processes distinctly. These results are in accordance with those achieved by DSC measurements. The isothermal heating was especially applied to investigate PET cold crystallisation. In its course the optical transmittance first decreases to a certain minimal value, regaining some of the transmittance in the final period of crystallisation (crystal growth). The used method is suitable for investigating crystallisation processes of polymers accomplished at very slow rates.This revised version was published online in November 2005 with corrections to the Cover Date.     

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。     

废旧聚酯（PET）的化学循环利用

废旧PET 聚酯可通过化学解聚来实现其循环利用。本文总结了废旧PET 聚酯化学循环利用领域的研究现状, 介绍了目前国内外开发的主要化学解聚工艺方法, 包括水解法、甲醇解聚法、乙二醇解聚法等, 同时对各种工艺过程的优缺点进行了综合比较。     

Modification of Poly(Ethylene Terephthalate) Track Membranes by Sorption of Poly(Ethylene Glycol)

Sorption of poly(ethylene glycol) on poly(ethylene terephthalate) track membranes was studied at different pH. The hydrophilic-hydrophobic properties of the intact membranes and those modified with poly(ethylene glycol) are compared. The membrane-aqueous human serum albumin and membrane-aqueous insulin adhesive tensions were determined for modified membranes. The competitive sorption of human serum albumin and poly(ethylene glycol) from aqueous solution on the track membranes is analyzed.     

o-Carborane-Containing Poly(siloxane-arylacetylene)s With Thermal and Thermo-Oxidative Stabilities

A series of poly(siloxane-arylacetylene)s with o-carborane in the backbone (CB-PSOA)s were prepared by the coupling reaction between poly(siloxane-arylacetylene) (PSOA) and decaborane (B₁₀H₁₄) in the presence of CH₃CN. CB-PSOAs were characterized by Fourier-transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS). The results show that the average amount of carborane units in a CB-PSOA chain could be raised when the molar ratio of B₁₀H₁₄ to PSOA is increased from 0.6 to 2.4. The crosslinking reaction could be carried on at above 140°C for CB-PSOAs. The CB-PSOA thermosets show excellent thermo oxidative stability with over 85% residue yield at 1000°C in air.     

Calorimetric study of Diepoxide Chain-Extended Poly(Ethylene Terephthalate)

A series of chain-extended PET samples were obtained by the use of different amounts of a diepoxide as chain extender, which was prepared for this purpose. These samples exhibited different intrinsic viscosities and degrees of branching or cross-linking. The effects of this differentiation on the thermal properties were studied by differential scanning calorimetry. The thermal parameters studied were the glass transition temperature (T_g), the cold-crystallization temperature (T_cc), the melting temperature (T_m), the enthalpy (ΔH_m) and the degree of crystallinity. The data revealed that, the higher the quantity of chain extender or the chain extension time, the higher T_gand T_cc, but the lower T_mand ΔH_m, i.e. the more amorphous the chain-extended samples, as also shown by density measurements. This revised version was published online in July 2006 with corrections to the Cover Date.     

Aspects of the Chemistry of Poly (Ethylene Terephthalate). IV. Hydrolysis of Poly(Ethylene Terephthalate) in the Melt Phase

The effect of water vapor pressure on the molecular weight of molten poly (ethylene terephthalate) has been followed by measurement of the changes which occur in the intrinsic viscosity and the end-group concentrations upon hydrolysis. It was found that phosphoric acid is highly effective as a stabilizer; the hydrolysis rate constant (K_h) decreasing from 7.6 × 10^?7 mol^?1s^?1 for nonstabilized to 2.5 × 10^?7 mol^?1s^?1 for the stabilized polyester at 290°C and water vapor pressure of 20 mmHg.     

A Study on Improving the Crystallization Rate of Poly (Ethylene Terephthalate)

In this study, sodium benzoate was selected as the nucleating agent to improve the crystallization rate of Poly (Ethylene Terephthalate) (PET). A new polyester, PEAT, which was systhesized from Bis Hydroxy-Ethyl Terephthalate (BHET) and adipic acid, was blended with PET to improve the (crystallization) rate of PET at lower temperatures. The crystallization rate of the PET blends was measured with a DSC and the kinetics of crystallization were studied. It was found that the range of the crystallization temperatures for the PET/sodium benzoate blends was wider than that for the PET/PEAT blends which shifted to a lower temperature region. PEAT showed a pronounced effect on the crystallization rate at lower temperatures, while sodium benzoate effected the crystallization rate within the entire range of crystallization temperatures.     

Base Hydrolysis of Poly(Ethylene Terephthalate) in Methanolic and Aqueous Solutions

Abstract

Hydrolysis of poly(ethylene terephthalate) fibers (intrinsic viscosity: 0.819 dL/g) using methanolic sodium methoxide was compared to that using aqueous sodium hydroxide. Weight and tenacity loss occurred more rapidly with methanolic NaOCH₃. After the methanolic NaOCH₃ treatment, the surface appeared far rougher, much of which was due to low molecular weight material present on the fibers. Intrinsic viscosity measurements indicated virtually no difference between the two treatments in the small amount of chain cleavage obtained at a given weight loss. Fiber density increased after the reaction with methanolic NaOCH₃, probably due to the presence of the methyl ester end groups formed during the ester interchange reaction, while fiber density was essentially unaffected by treatment in aqueous NaOH. Density decreased after the methanolic NaOCH₃-treated fiber was hydrolyzed with aqueous NaOH. Thermal analysis revealed a small increase in the melting temperature after methanolic NaOCH₃ treatment. The shoulder present in the melting region of this sample was markedly affected by chloroform extraction of low molecular weight products resulting from the reaction. While hydrolysis using methanolic NaOCH₃ was more severe than that using aqueous NaOH, both reactions appeared to be confined to the fiber surface.     

Kinetics of Mass Transfer in the Melt Polycondensation of Poly(Ethylene Terephthalate)

For a four-parameter reaction-mass transport model of melt polycondensation, the constants of polycondensation, thermolysis, and diffusion were determined by means of experiments in thin-layer polycondensation. Based on these constants, the convectional mass transport and efficient melt thickness in polycondensation systems under conditions of compelled mixing can be estimated. However, for stirred polycondensation systems a reaction-mass transfer model proves more suitable. The constants of polycondensation and thermolysis obtained by the diffusion model can be transferred to the reaction-mass transfer model. Thus, only the mass transfer coefficient has to be determined.     

红外光谱在聚对苯二甲酸乙二醇酯纤维结构研究中的应用

回顾了近年来红外光谱在聚对苯二甲酸乙二醇酯(PET)纤维结构研究中的应用,介绍了纤维制样技术,归纳了构象含量、取向、折叠链含量等结构参数的表征方法及其应用,以及这些结构参数与纤维性能间的联系。     

Graft Copolymerization of Methyl Methacrylate onto Poly(Ethylene Terephthalate) Fibers Using Benzoyl Peroxide

Abstract

The graft copolymerization of methyl methacrylate onto poly(ethylene terephthalate) fibers has been studied using benzoyl peroxide as initiator. The grafting reactions were carried out within the 70 to 90°C temperature range, and the variations of graft yield with monomer and initiator concentrations were also investigated. The overall activation energy for grafting was calculated as 34.1 kcal/mol. The results of dyeability with the disperse dye suggested that diffusion into the fiber structure was moderately difficult when the graft yield reached 14?15%. The maximum graft yield was obtained at a benzoyl peroxide concentration of 4.00 × 10^?3 M. The decomposition temperature values obtained from thermogravimetric analysis show that the thermal stability of poly(ethylene terephthalate) fibers decreased as a result of grafting. Further, such change in the properties of methyl methacrylate grafted fibers as density, diameter, and moisture regain were also determined.     

聚对苯二甲酸丙二醇酯(PTT)的研究

新型聚酯材料聚对苯二甲酸丙二醇酯(PTT)是一种极有应用潜力的聚合物，但在非纤维领域的研究与应用才刚开始。本文简要概述了其发展状况；详述其结构、性能特点；重点介绍PTT目前在非纤维领域的应用与研究进展。     

Synthesis of Poly(lactide)s with Modified Thermal and Mechanical Properties

The use of poly(lactide)‐based materials is, in part, limited by their physical and mechanical properties. This article reviews the methods that have been employed to enable enhancement of the materials properties through synthetic manipulation of the polymer structure including block copolymer synthesis and modification of the lactide monomer structure, focusing on the application of ring‐opening polymerization. In turn the effect of these structural modifications on the properties of the resultant materials are reported.

     

Innovative Poly(Butylene Terephthalate) Based Nanocomposites: a Preliminary Investigation

A polymer-clay nanocomposite based on Poly(butyleneterephthalate) (PBT) and an innovative organoclay has been synthesized via intercalation of Bis(hydroxyethyl terephthalate) (BHET) in Na-Montmorillonite layers. Chemical and physical properties of this nanocomposite have been studied in comparison to other PBT/nanocomposites based on two commercial organoclay: Cloisite 25A and Somasif MEE. Nanocomposites have been prepared via melt compounding using a twin-screw extruder, with extrusion rate of 150 rpm. Samples were characterized by using wide-angle X-ray diffraction, TEM, thermal and mechanical analysis.     

Analysis of the Molecular Weight Distributions of Aminolyzed Poly(Ethylene Terephthalate) by Using Gel Permeation Chromatography

The molecular weight distributions of poly(ethylene terephthalate) fibers aminolyzed with selected primary amines (namely, methylamine, ethylamine, n-butylamine, and ethanolamine) were determined by using gel permeation chromatography. Initially the shape of the differential molecular weight distribution (DMWD) curve did not change although its peak shifted to lower molecular weights. As aminolysis continued, a shoulder appeared on the DMWD curve. Its appearance seemed to coincide with an increase in the density of the product. Ultimately, distinct molecular populations could be identified in the treated polymer depending on the severity of the aminolysis and the selectivity of the particular amine. The lowest is thought to represent primarily crystalline residues and has a peak molecular weight of 3400. The relations between M _n and ultimate tenacity and breaking strain for the aminolyzed products were linear.     

Functionalization of Poly[Ethylene Terephthalate) by Means of Glow-Discharge-Initiated Polymerization of Acrylic Acid

Glow-discharge-initiated polymerization of acrylic acid incorporated in poly(ethylene terephthalate) (PET) films was investigated. An increase in polymerization yield with plasma treatment duration and power was found. Polymerization was not confined to the film surface. At high power and long treatment time, polymerization in the bulk of the PET also took place. Water regain and contact angle of the PET-treated films were affected by the presence of poly(acrylic acid) (PAA). The carboxyl groups of the PAA chains incorporated in the PET matrix were utilized for further chemical modification of the PET film. Poly(ethylene glycol) (PEG) was grafted onto PAA by esterification. DSC studies showed the presence of both PAA and PEG in the PET matrix and shed light on the morphology of the multicomponent polymeric system. Free isocyanate groups were introduced into the PET matrix by reacting PAA carboxyl groups with hexamethylene diisocyanate.     

FTIR Study of the Thermal Degradation of Poly(vinyl Alcohol)

The degradation of poly(vinyl alcohol) was investigated using TG analysis and Fourier transform infrared spectroscopy to determine the effect of atmosphere on the process of degradation. In the spectra, four vibrational modes were identified that characterised the major steps of the degradation process. These were the O-H, C-H, C=O and C=C stretching modes. The mechanism observed for degradation in an inert atmosphere was in accordance with the accepted mechanism of elimination followed by pyrolisation. Evidence of conjugated polyenes, however, was not observed. For the air atmosphere, oxidation in both steps of the degradation process was observed. This revised version was published online in July 2006 with corrections to the Cover Date.