Solid‐phase thermal polymerization of macrocyclic ethylene terephthalate dimer using various transesterification catalysts

Thermal ring‐opening polymerization of a uniform macrocyclic ethylene terephthalate dimer with and without catalyst was investigated for the first time. Although polymerization progressed without a catalyst, the reaction was extremely slow and all the products were colored. Various transesterification catalysts were tested for their activity toward this ring‐opening polymerization. Among the various catalysts, 1,3‐dichloro‐1,1,3,3‐tetrabutyldistannoxane exhibited the highest catalytic activity, and a colorless polymer with a weight‐average molecular weight of 36,100 was obtained in 100% yield by heating for 3 min at 200 °C. It is noteworthy that our method does not need a vacuum because no side products are formed during the process. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3360–3368, 2000     

以三嗪衍生物及对苯二甲酸为配体的四个配合物的合成、表征及性质研究

通过水热合成法,合成了4个配位聚合物:[Mn(H2O)(PTZDA)(BDC)]n(1)、[Co(H2O)(PTZDA)(BDC)]n(2)、[Zn(H2O)(PTZDA)(BDC)]n(3)、[Cd(H2O)(PTZDA)(BDC)]n(4)(PTZDA=2,4-二氨基-6-(2′-吡啶)-均三嗪,H2BDC=对苯二甲酸),并分别用X射线单晶衍射、元素分析、红外光谱、差热分析和X-射线粉末衍射表征了这4个配合物。晶体结构分析表明,在配合物1~4中,配体PTZDA与中心金属离子螯合配位,金属离子通过配体BDC2-连结成一维链状结构,一维链之间通过氢键作用连接成三维超分子结构。磁性和荧光分析表明,配合物1和2具有非常弱的反铁磁作用;配合物3和4的荧光均为配体发光。     

Discrimination of Thermoplastic Polyesters by MALDI-TOF MS and Py-GC/MS

The aim of this work is to discriminate thermoplastic polyester-polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polytrimethylene terephthalate (PTT), which cannot be easily identified by many methods. Both matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) and pyrolysis gas chromatography/mass spectrometry (Py-GC/MS) were applied to identify these polyesters owing to their analytical ability to determining polymers' chemical structure. The three thermoplastic polyesters can be easily distinguished by MALDI-TOF MS according to their different repeated units. Py-GC/MS was used to analyze their specific pyrolyzates. The three polyesters can be identified through their characteristic pyrolysis products as well.     

Investigation of Hydrolysis in Poly（ethylene terephthalate） by FTIR-ATR

The hydrothermal aging of poly(ethylene terephthalate)(PET) was investigated at 70 95 °C. A new method to investigate the hydrolysis degree of PET by Fourier transform infrared spectroscopy(FTIR) was proposed. The spectra during the hydrothermal aging were measured using attenuated total reflection accessory(ATR). Peak resolving of carbonyl regions was performed, and the ratio of two groups of bands representing carboxylic acids and esters respectively were calculated to show the hydrolysis degree of ester groups in PET. The acid/ester ratio shows exactly the same trend as the average chain scission number per unit mass at various temperatures and thus can be used as a parameter to characterize the hydrolysis and random chain scission of PET. This method related to the hydrolysis mechanism directly, is simple, fast and convenient compared to the traditional methods such as viscometry, end-group titration and size exclusion chromatography(SEC). It may also be useful in hydrolysis characterization of other polyesters.     

193 nm激光引发PET表面的化学接枝

将聚对苯二甲酸乙二醇酯[Poly(ethylene terephthalate), PET]材料置于氨气气氛中, 利用激光光子同时激发材料表面及氨气形成自由基, 用激光引发反应并促进氨基在材料表面的接枝. 改性后的测试结果表明, 材料表面粗糙度没有显著变化, 但水接触角的减小表明表面化学结构发生了某种变化. 傅里叶变换红外光谱(FTIR/ATR)图谱在3352和1613 cm-1处出现了新的氨基吸收峰, 证实了表面接枝了氨基. 同时X射线光电子能谱(XPS)也证明了材料表面C—N键的存在, 其C1s结合能为285.5 eV, N1s为398.9 eV. 飞行时间二次离子质谱(Tof-SIMS)也检测到含氨基的分子碎片, 其碎片成像图显示接枝仅发生在激光辐照部位. 实验结果表明, 激光能在生物材料表面进行局部区域的选择性接枝.     

A modulated dsc study on the in situ polymerization of cyclic butylene terephthalate oligomers

The polymerization of a cyclic butylene terephthalate (CBT) oligomer was studied as a function of temperature (T=200 and 260°C, respectively) by modulated DSC (MDSC). The first heating was followed by cooling after various holding times (5, 15 and 30 min) prior to the second heating which ended always at T=260°C. This allowed us to study the crystallization and melting behavior of the resulting polybutylene terephthalate (PBT), as well. In contrary to the usual belief, the CBT polymerization is exothermic and the related process is superimposed to that of the CBT melting. The melting behavior of the PBT was affected by the polymerization mode (performed below or above the melting temperature of the PBT product) of the CBT. Annealing above the melting temperature of PBT yielded a product featuring double melting. This was attributed to the presence of crystallites with different degrees of perfection. The crystals perfection which occurred via recrystallization/remelting was manifested by a pronounced exothermic peak in the non-reversing trace.     

Effect of adding new phosphazene compounds to poly(butylene terephthalate)/polyamide blends. II: Effect of different polyamides on the properties of extruded samples

Poly(butylene terephthalate) (PBT) and a sample of polyamide have been melt processed in the presence of two new phosphazene compounds, namely 2,2-dichloro-4,4,6,6-bis[spyro(2′,2″-dioxy-1′,1″-biphenyl)]cyclotriphosphazene (2Cl-CP) and 2,2-bis(2-methoxy-4-methyleneoxy-phenoxy)-4,4,6,6-bis[spyro(2′,2″-dioxy-1′,1″-biphenyl)]cyclophosphazene (CP-2EPOX).The blends were prepared by using polyamide 6 (PA6) and polyamide 6,6 (PA66) in 25/75 and 75/25 w/w compositions by using a co-rotating twin-screw extruder.The materials have been completely characterized from a mechanical, rheological, and morphological point of view. The results indicate that the additives used cause an increase of the rupture properties and of the viscosity, especially in the PA6 rich blends containing CP-2EPOX. This result can be not only attributed to a chain extension effect on the PA phase but also to in situ formation of PA/PBT copolymers promoted by the presence of the CP compound as confirmed by NMR and MALDI-TOF analyses. The compatibilization effect fades in blends containing PA66, probably due to a thermal deactivation of the additives at higher temperature required to process this polymer.     

Non-isothermal crystallization kinetics of poly(trimethylene terephthalate)/poly(ethylene 2,6-naphthalate) blends

The glass-transition temperature and non-isothermal crystallization of poly(trimethylene terephthalate)/poly(ethylene 2,6-naphthalate) (PTT/PEN) blends were investigated by using differential scanning calorimeter (DSC). The results suggested that the binary blends showed different crystallization and melting behaviors due to their different component of PTT and PEN. All of the samples exhibited a single glass-transition temperature, indicating that the component PTT and PEN were miscible in amorphous phase. The value of T_g predicted well by Gordon-Taylor equation decreased gradually with increasing of PTT content. The commonly used Avrami equation modified by Jeziorny, Ozawa theory and the method developed by Mo were used, respectively, to fit the primary stage of non-isothermal crystallization. The kinetic parameters suggested that the PTT content improved the crystallization of PEN in the binary blend. The crystallization growth dimension, crystallization rate and the degree of crystallinity of the blends were increased with the increasing content of PTT. The effective activation energy calculated by the advanced iso-conversional method developed by Vyazovkin also concluded that the value of E_a depended not only on the system but also on temperature, that is, the binary blend with more PTT component had higher crystallization ability and the crystallization ability is increased with increasing temperature. The kinetic parameters U^* and K_g were also determined, respectively, by the Hoffman-Lauritzen theory.     

Effect of a novel phosphorous-nitrogen containing intumescent flame retardant on the fire retardancy and the thermal behaviour of poly(butylene terephthalate)

A novel phosphorus-nitrogen containing intumescent flame retardant (P-N IFR) was prepared via the reaction of a caged bicyclic phosphorus (PEPA) compound and 4,4′-diamino diphenyl methane (DDM) in two steps. The product was added to poly(butylene terephthalate) (PBT) to obtain halogen-free flame retarded polyester. UL-94 test, thermogravimetry and in situ infrared spectroscopy were used to characterize the flammability, thermal degradation properties and the char-forming process. It was shown that the phosphorus-nitrogen containing compound could improve both the flame retardancy and thermal stability more effectively than other P-N flame retardants. Furthermore, it was a good char-forming agent incorporated with the co-addition of polyurethane (PU) when the combustion occurred. The formation of P-N structure was incorporated in the char layer.     

Surface treatment of PET fiber by EB-irradiation-induced graft polymerization and its effect on adhesion in natural rubber matrix

Aiming to develop a high performance fiber-reinforced natural rubber (NR) without using resorcinol formaldehyde latex (RFL) adhesives of environmental load substances, a special technique using electron beam (EB) irradiation-induced graft polymerization was applied to high-modulus polyethylene terephthalate (PET) fibers. Although PET is chemically inert, acrylate functional silane could be graft-polymerized onto the PET fiber surface by this special technique. The composite of NR and grafted PET fibers indicated a linear increase in the initial modulus with the fiber content. The fiber reinforced rubber with a good performance was obtained in the system of NR and grafted PET fibers.