Determination of solid products from the de-polymerization of poly(trimethylene terephthalate) in supercritical methanol

A method based on high-resolution size-exclusion chromatography (SEC) was established to analyze the solid products from the depolymerization of poly(trimethylene terephthalate) (PTT) in supercritical methanol. In the qualitative analysis, four factors (chromatographic retention time, qualitative multi-wavelength ultraviolet spectra, linear internal-insert SEC and qualitative IR spectra) were considered. The main solid products from the process were dimethyl terephthalate (DMT), methyl-(2-hydroxypropyl) terephthalate (MHPT), bis(2-hydroxypropyl) terephthalate (BHPT), methyl-(2-hydroxyethyl) terephthalate (MHET), bis(2-hydroxyethyl) terephthalate (BHET), and hydroxyethyl-(2-hydroxypropyl) terephthalate (HEHPT). It is found that the method is of a high resolution among the solid products and has a fine repeatability. In addition, the solid products from the de-polymerization of poly(ethylene terephthalate) (PET) in similar process were also analyzed by this method. Furthermore, the effects of supercritical conditions on the distribution of the products were also discussed.     

Oxidative crosslinking in poly(ethylene terephthalate) at elevated temperatures

Poly(ethylene terephthalate) oxidizes on being heated in air at elevated temperatures to form a crosslinked structure. The crosslinking occurs through a reaction which causes arylation of terephthalate rings to form a biphenyltricarboxylic acid derivative. This reaction is interpreted as a free-radical cleavage generating a substituted phenyl radical which selectively attaches to a terephthalate residue via substitution.     

Miscibility and Crystallization in Binary Crystalline Blends of Poly(butylene terephthalate) with Poly(butylene terephthalate-e-caprolactone)

Poly(butylene terephthalate)/poly(butylene terephthalate-e-caprolactone) is a new A/AxB1-x binary crystalline blend with intra-molecular repulsion interaction. Using the mean-field binary interaction model, the value of interaction parameter between the butylene terephthalate and caprolactone structural unit was first reported to be 0.305. This blend exhibited different crystallization behavior from a typical homopolymer/copolymer blend, which was carefully investigated by di?erential scanning calorimetry. It was found that poly(butylene terephthalate-e-caprolactone) copolymers have a great effect on the pure poly(butylene terephthalate) chain mobility and poly(butylene terephthalate) crystalline lattice packing. In the meantime, the crystallization of butylene terephthalate segments in copolymers was restricted by the previously formed poly(butylene terephthalate) crystallites. The two constituents for blending can not form a co-crystal in the range of composition even if they have the same butylene terephthalate unit. It can be concluded that longersegments in a copolymer would be beneficial for the formation of a co-crystal in blends.     

Sequential analysis of polyesters by stepwise chemical degradation: Preparation of degradation products

Model reactions for the sequential analysis of polyesters, especially those of the poly(ethylene terephthalate) and poly(butylene terephthalate) type, by stepwise chemical degradation were performed. The cyclic degradation products, containing the reagent and an ethylene terephthalate or butylene terephthalate unit, terephthalic acid mono(2-{o{N-<N′-[4-(iminomethyl-) benzoyl-]> 2′-(imino)ethoxycarbonyl-}iminobenzoyl-} oxyalkyl) ester N″-lactams, were deliberately synthesized.     

Vibrational analysis of polyethylene terephthalate and its deuterated derivatives

The Vibrational analysis of polyethylene terephthalate, polyethylene-d₄ terephthalate, and polyethylene terephthalate-d₄ has been carried out using a valence force field calculated from the infrared and Raman spectra of a series of low molecular weight aromatic esters. The Raman spectra for polyethylene-d₄ terephthalate and polyethylene terephthalate-d₄ are presented and band assignments for these compounds and polyethylene terephthalate are discussed.     

Direct fluorination of polyester and related compounds

Polyethylene terephthalate and model compounds representing various aspects of polyethylene terephthalate have been treated with elemental fluorine. Polyester was found to react in a manner more resembling ethylene glycol dibenzoate than diethyl terephthalate or terephthalic acid. The degree of fluorine incorporation increases as the aliphatic character of the substrate is increased. The reaction was studied using fluorine incorporation, ir, ESCA and esr techniques.     

Internal motion in some aromatic polyesters and linear aromatic chains

Low-temperature internal motions of the following polyesters have been investigated by broad line nuclear magnetic resonance: poly(methylene terephthalates) (2–6 methylene groups), poly[1,4-(dimethylene)cyclohexylene terephthalate], poly(diethyleneglycol terephthalate), poly(1,2-propylene terephthalate), poly(1,4-phenylene terephthalate), poly(2,2,3,3,4,4-hexafluoropentamethylene terephthalate), poly[1,4-phenylenebis(dimethyl) siloxane], and poly(2,6-dimethylphenylene oxide). No complex line structure was found for any of the samples. Molecular motions in the polyesters appear to be restricted by polar forces arising from the ester groups. Above—196°C. the line width decreases smoothly with increasing temperatures for all polymers except poly[1,4-(dimethylene)cyclohexylene terephthalate] and poly[1,4-phenylenebis(dimethyl)siloxane]. These two show a definite transition in line width at ?20°C. and +12°C., respectively, caused by the onset of considerable internal motion. At ?196°C. the lattices are rigid except for polymers containing methyl groups: poly(1,2-propylene terephthalate), poly[1,4-phenylenebis(dimethyl) siloxane], and poly(2,6-dimethylphenylene oxide). Internal motion that can be ascribed to be a reorientation of the methyl groups is present at ?196°C. for these three polymers, as is demonstrated by comparison of experimental second moments and those calculated on the basis of various models.     

Sequential analysis of polyesters by stepwise chemical degradation: Application to oligo and poly(alkylene terephthalate)s

A specifically tailored reagent was used to label the hydroxyl end groups of poly(ethylene/butylene terephthalate), which is synthesized by transesterification of the corresponding homopolymers. The terminal monomeric unit was then eliminated, together with the attached label, as a low molecular-weight cyclic compound. Specially synthesized reference compounds containing ethylene terephthalate and butylene terephthalate units enabled the terminal monomeric unit to be identified as butylene terephthalate, although the copolymer showed an otherwise random distribution. Despite the practical and theoretical reasons that restrict this sequential degradation to the last monomeric unit for polymers, the principle can be used in a wider range of applications if combined with selective degradation and separation by means of HPLC, which results in chemically uniform oligomers. The ultimate and penultimate monomeric units of ethylene/butylene terephthalate type oligomers can be identified using the cyclodegradation procedure described here. © 1993 John Wiley & Sons, Inc.     

Engineering MIL-53(Al) flexibility by controlling amino tags

The flexibility of MIL-53(Al) can be tuned by adjusting the ratio of terephthalate and 2-amino terephthalate linkers incorporated into the framework during hydrothermal synthesis.     

Preparation and properties of poly(methylene terephthalates)

A systematic study of poly(methylene terephthalates) has been made. Melting points, second-order transition temperatures, and solubility temperatures are presented for the homologous series of terephthalate polyesters of ethylene glycol through 1,10-dodecanediol, and for terephthalate copolyesters of: (1) ethylene glycol/1,3-propanediol and (2) ethylene glycol/1,4-butanediol. Fiber properties of the terephthalate polyesters and the 70/30 ethylene glycol/1,3-propanediol copolyterephthalate ester are presented. Only the first three members of the poly(methylene terephthalate) series show promise for use in textile fibers.     

Branching and cross-linking of poly(ethylene terephthalate) and its foaming properties

The branching and cross-linking of poly(ethylene terephthalate) were investigated using two chain extenders: glycidyl methacrylate-styrene copolymer (GS) and poly(butylene terephthalate)-GS (PBT-GS) in order to improve the melt viscosity and melt strength of poly(ethylene terephthalate). An obvious increase in torque evolution associated with chain extending, branching and cross-linking was observed during the process. The properties of modified poly(ethylene terephthalate) were characterized by intrinsic viscosity and insoluble content measurements, rheological and thermal analysis. The intrinsic viscosity and rheological properties of modified PET were improved significantly when using PBT-GS, indicating that PBT-GS should be a better chain extender. Good foaming of poly(ethylene terephthalate) materials were obtained using supercritical CO₂ as blowing agent. The average cell diameter and cell density were 61 μm and 1.8 × 10⁸ cells/cm³, respectively.     

Direct usage of products of poly(ethylene terephthalate) glycolysis for manufacturing of glass-fibre-reinforced plastics

The paper reports on the possibility of direct use of some products of poly(ethylene terephthalate) glycolysis, bis(2-hydroxyethyl) terephthalate and ethylene glycol mainly, in the process of glass-fibre-reinforced plastics manufacturing. The addition of toluene diisocyanate as an intermediating agent was an important prerequisite for their incorporation into the resin composition. The composites containing products of poly(ethylene terephthalate) glycolysis up to 15% mass display improved mechanical properties in comparison with the unmodified samples.     

稀土催化聚酯和共聚酯的合成

研究Ｌｎ＾３＋化合物对聚对苯二甲酸乙二酯及其共聚酯合成反应的催化效果。发现Ｌｎ＾３＋档促进酯化反应的进行,并可在缩聚阶段作为Ｓｂ２Ｏ３的助催化剂使用,通过粘度降测试表明,添加Ｌｎ＾３＋不影响聚酯、共聚酯的热稳定性。对Ｌｎ＾３＋催化酯化和缩聚反应机制进行探讨。     

Green synthesis and properties of nickel terephthalate complex with 2,2&#x27;-bipyridine

Green synthesis of nickel terephthalate complex with 2,2′-bipyridine involves the preparation of intermediate nickel terephthalate followed by complexation with 2,2′-bipyridine. The resulting substance was tested as an adsorbent for solidphase extraction of technogenic pollutants.     

Gel permeation chromatography of poly(ethylene terephthalate-co-ethylene isophthalate)

Poly(ethylene terephthalate) and the copolyesters obtained by copolycondensation of ethylene glycol with dimethyl terephthalate and dimethyl isophthalate were fractionated by coacervate extraction and gel permeation chromatography. The results established the influence of chemical inhomogeneity of chains on the separation process.     

HPGPC和HPLC测定齐聚物的聚合度分布与平均聚合度

用高效凝胶色谱和反相高效液相色谱测定了聚对苯二甲酸乙二酯齐聚物、聚对苯二甲酸丁二酯齐聚物的聚合度分布与平均聚合度,获得了满意的结果。同时,比较了这两种分析测试方法的优缺点。     

对苯二甲酸单异辛酯的合成

以对苯二甲酸、氯化亚砜、异辛醇为原料，经过酰化、酯化两步合成了对苯二甲酸单异辛酯，收率40．4％,纯度99．0％。     

A chemical procedure for reprocessing of poly(ethylene terephthalate) waste

A procedure was developed for degradation of poly(ethylene terephthalate) waste with water to the starting monomers. The possibility of preparing diethyl terephthalate without a catalyst in a rocking cylindrical pressure vessel with the rocking axis passing through the geometric center was examined.     

Adhesive polymer. Fluorescence depolarizations of chromophores in adhesive agent on poly(ethylene terephthalate) base film

The fluorescence depolarizations of chromophores have been measured in adhesive agent on poly(ethylene terephthalate) film. The emission anisotropies of chromophores are influenced on increasing the thickness of the layer of adhesive polymer or poly(ethylene terephthalate) base film. These results are briefly discussed.     

Preparation and characterization novel dioctyl terephthalate blended polyvinyl alcohol-composite films incorporated with the graphene oxide and silver nanoparticles

Dioctyl terephthalate is of great interest as a replacement for the phthalate plasticizers such as dioctyl phthalate and diisononyl phthalate due to its orthophthalate-free and non-carcinogenic properties. This study focused on the production, characterization and optimization of the quality characteristics of its film properties, such as the mechanical, hydrophilic and thermal properties of dioctyl terephthalate-blended polyvinyl alcohol composites modified with graphene oxide and silver nanoparticles using TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) based Taguchi Method. Dioctyl terephthalate has brought remarkable features, such as high elastic modulus, and hydrophilic and thermal stability to the polyvinyl alcohol matrix. The optimum Dioctyl terephthalate -blended polyvinyl alcohol films have a 2.26 times lower contact angle and a 13.41 times higher elastic modulus than the reference polyvinyl alcohol film. Dioctyl terephthalate should be preferentially used to manufacture more durable and hydrophilic composite films such as fibers, disposable underpad or industrial swab, instead of toxic phthalate plasticizers.