Determination of Q and e Values by a Least Squares Technique

A more precise determination of Q and e values for vinyl monomers can be attained through the use of a linear least squares technique.     

(RS)-, (R)- and (S)-3-benzyl-3-ethyl 2-oxetanone polymerization with chiral and achiral initiators

The polymerization of 3-benzyl-3-ethyl 2-oxetanones leads to three types of polymers: polyRS (enantiomer excess,ee=0), polyR or polyS (Ree >See) and polyracemate. All these polymers are crystalline and the thermal properties (T _g, meltingT _M and H _M) depend mainly on theee of the polymer. The propagation of the polymerization is not stereospecific. The use of heating-cooling cycles leads to a pure crystalline form melting at the highest temperature. The polyracemate has the behaviour of a pure polymer which melts at a lower temperature, a prolonged heating in the melt induces a strong racemization.

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Zusammenfassung Die Polymerisation von 3-benzyl-3-ethyl 2-oxetanon führt zu drei Polymer Typen: PolyRS (überschuss des Enantiomers,EE=0), PolyR oder PolyS (REE > SEE) und Polyracemate. Alle Polymere sind kristallin und die thermischen Eigenschaften (T _g, SchmelzeT _M und H _M) hängen wesentlich vonEE des Polymers ab. Die Fortpflanzung der Polymerisation ist nicht stereospeeifisch. Die Verwendung von Aufheitzen Abkühl Zyklen führt zu einer reinen kristallinen Form, die bei der höchsten Temperatur schmilzt. Das Polyracemat verhält sich wie ein reines Polymer, das bei niedrigeren Temperatur schmilzt; es racemisiert im Laufe einer verlängerten Erhitzung im Schemlzfluss.

     

Morphology and performance of unsaturated polyester nanocomposites modified with organoclay and thermoplastic polyurethane

<正>Unsaturated polyester(UPR)/thermoplastic polyurethane(TPU)/organoclay nanocomposites were prepared by melt compounding of thermoplastic polyurethane and unsaturated polyester prepolymer,and then mixing with the hybrids of styrene monomers and organoclay at ambient temperature.The crosslinking reaction eventually occurred through the unsaturated polyester prepolymer and styrene monomer.The morphology of the composites was investigated by scanning electron microscopy(SEM) and transmission electron microscopy(TEM).The results show that the impact strength of UPR/TPU/organoclay nanocomposites increases obviously;the cure shrinkage decreases markedly,the glass transition temperature is enhanced and an elastic response to the deformation is prominent at the temperature above 10℃.     

基于单体的Q和e值绘制二元共聚双曲线*

采用Matlab中的Plot函数,首次以单体的Q、e值为中间变量,绘制出二元共聚双曲线。将二元共聚物组成曲线F1-f1和F2-f2同时呈现在一个图上,使隐含的第二单体的共聚行为可视化,有助于加深学习者对二元共聚的理解。     

An efficient synthesis of 5-aminoimidazol-2-ones via cyclization reactions of 2-aminoacetonitriles and isocyanates

The scope of a cyclization reaction between amino-acetonitriles and isocyanates was investigated. The study revealed that this reaction tolerates various functional groups leading to highly functionalized 5-amino-imidazole-2-ones, which are useful intermediates for purine synthesis.     

Oriented array of polyethylene-block-poly(ethylene oxide) nanoplatelets in unsaturated polyesters cross-linked coatings

Transparent coatings of cross-linked unsaturated polyester (UP) containing staggered platelets of polyethylene-block-poly(ethylene oxide) with their normal perpendicular to the substrate have been readily prepared by a solvent assisted spin-coating method. For this purpose, homogeneous liquid dispersions of block copolymer platelets in liquid UP resin have been prepared using a selective solvent, deposited onto flat substrates by spin-coating and converted into a transparent solid layer by photochemical cross-linking. Although such stratified morphology has been already reported for inorganic nanoplatelets (typically clay particles), we report for the fist time the formation of such stratified morphology in fully organic system. The shear-induced origin of this organization has been confirmed by the rheological properties of the uncured systems where a pronounced non-Newtonian behavior has been observed.     

Kinetics of Isothermal Crystallization of the Thermotropic Polyester Poly(ethylethylene-4,4-diphenoxyterephthalate)

Differential scanning calorimetry was used to study the isothermal kinetics of three-dimensional ordering formation from the mesophase of the thermotropic polyester poly(ethylethylene-4,4-diphenoxyterephthalate). An Avrami exponent of 4 was found and the measured rates of transformation were related with the efficiency of packing. A nucleation and growth process was assumed in the determination of the temperature coefficient, and the interfacial free energies are discussed in terms of the chain flexibility. This revised version was published online in July 2006 with corrections to the Cover Date.     

Degradation of crosslinked unsaturated polyesters in sub-critical water

The degradation of unsaturated polyesters crosslinked with styrene was performed in sub-critical water (SCW) in the absence and presence of organic additives. The unsaturated polyesters were de-crosslinked by hydrolysis of ester chains to form polystyrene derivatives on SCW treatment at 300 °C. With an increase in treating time, carboxylic acid groups in the polystyrene derivatives were turned into carboxylic anhydride groups in SCW. The de-crosslinking rate was much enhanced on SCW treatment in the presence of hydroxy compounds with a long alkyl chain and alkylamines, while carboxylic acids, benzenesulfonate salts, and quaternary ammonium salts were ineffective even though they had a long alkyl chain. The degree of de-crosslinking was reduced in the presence of diamines and amino acids because re-crosslinking at both ends of the additive molecules proceeded.     

Synthesis of unsaturated polyester resins for large sized composites

A series of unsaturated polyesters based on phthalic anhydride (PHA), maleic anhydride (MA), ethylene glycol (EG), diethylene glycol (DG), triethylene glycol (TG), propylene glycol (PG), styrene (Sty) and acrylonitrile (AN) were prepared. The molecular weights of the prepared polyesters were determined by end-group analysis. The effect of the structure of the resin on its curing behavior has been investigated. On the basis of the experimental study, the following were concluded: (1) The maximum curing temperature (T_max) is related to the molecular weight of the glycol incorporated in these castings. In this context the T_max was found to decrease with increasing the molecular weight. Meanwhile the time to peak temperature t_max was increasing. (2) The higher the percentage of AN in the crosslinking monomer system, the slower a resin cures. (3) The values of T_max were found to be influenced to a large extent by the percentage of AN.     

Thermal degradation and fire behaviour of unsaturated polyesters filled with metallic oxides

Nano-alumina and submicron alumina trihydrate particles were incorporated into an unsaturated polyester resin at various loadings. The morphologies of composites showed that only nano-alumina was correctly dispersed. The thermal degradation behaviour of the composites was studied using thermogravimetric analysis and Py-GC/MS, while their fire behaviour was investigated using cone calorimeter and pyrolysis combustion flow microcalorimeter. Synergistic effects on thermal stability and heat release rate were observed for combinations between both submicron filler and nanofiller. The best result for fire behaviour was obtained for a global loading of 10wt% with an equal mass ratio for both kind of particles. Mass loss curves also showed increased char yield. The interest of combining particles with different sizes has been discussed as well as the role of water release, regarding activations energies of degradation processes.     

Linear unsaturated polyester + poly(?-caprolactone) blends: Calorimetric behaviour and morphology

Blends of a linear unsaturated polyester (LUP, commercially named Al100) with poly(?-caprolactone) (PCL) of different molecular weights have been studied. The miscibility and crystallinity have been analyzed through FT-IR spectroscopy, differential scanning calorimetry (DSC) and environmental scanning electronic microscopy (ESEM). All the blends were subjected to the same heat treatment consisting of crystallizing during 45 min at constant temperature (10, 20, 30 or 40 °C). The glass transition temperature, T_g, and fusion temperature, T_fus, have been determined in the whole composition range for each blend. The T_g-composition dependence and the high degree of crystallinity detected at intermediate blend compositions denote an anomalous behaviour that could indicate the lack of homogeneity (phase separation) in the different blends studied. The ESEM measurements confirm the lack of homogeneity of the amorphous region in blends with high content of LUP. The results have been discussed as a function of the crystallization temperature and the molecular weight of PCL.     

Synthesis,characterization, biocompatibility,thermal and mechanical performances of sawdust reinforced composite

The work outlines the synthesis of a new and easy technique to develop sustainable composites of sawdusts reinforced polyester resin composites. For shaping a new approach we have found very rare approach for developing composites with sawdusts of Mahagoni wood (Swietenia mahagoni) reinforced polyester resin composites in open literatures. Due to this gap, a plan made to develop untreated and treated sawdusts (very common in Bangladesh and many other countries of the world) reinforced strong and durable composites with unsaturated polyester resins along with their biodegradability, thermal and mechnical properties where the material properties were revealed and corelations were elaborated in the subsequent sections. Specifically, the tensile strengths of virgin resin (VR), untreated sawdust reinforced composite (UTSDC) and 4% caustic soda treated sawdust reinforced composite (4TSDC) are 10.77, 15.83 and 21.64 N/mm², respectively. That means the observed reinforcement property for UTSDC and 4TSDC increased ~47% and 101%, respectively. Moreover, the binding phenomena were explained with the own schamatic presentation. The composite phenomena was explained sequentially by using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, etc. Between the developed composites 4TSDC was strong (25% as compared from tensile strength) and durable (8% as observed in biodegradability results) than the UTSDC of unsaturated polyester resin. The pattern of water uptake follows usual Fickian diffusion behavior. The observed properties of the developed convincible composites indicate that they can be considered for indoor to outdoor applications especially for using the fence, roof, furniture items like chair, table, park benches, etc.     

Effect of alcohols on the degradation of crosslinked unsaturated polyester in sub-critical water

The effect of alcohols on the degradation of unsaturated polyesters crosslinked with styrene was studied in sub-critical water at 300 °C. The de-crosslinked polymer was obtained by degradation of polyester chains in sub-critical water, and the de-crosslinking was enhanced by adding alcohols and phenols having a long alkyl chain such as 1-tetradecanol and 3-pentadecylphenol. However, the enhancement was not observed in the presence of diols even when they had a long alkyl chain. This finding suggests that transesterification enhanced the de-crosslinking of the polymer in sub-critical water.     

Unsaturated polyester resins modified with phosphorus-containing groups: Effects on thermal properties and flammability

A novel reactive phosphorus-containing monomer [1-oxo-2,6,7-trioxa-1- phosphabicyclo-[2.2.2]octane-methyl diallyl phosphate, PDAP] was synthesized, and various amounts of PDAP were combined with unsaturated polyester by radical bulk polymerization. The resulting flame-retardant unsaturated polyester resin (FR-UPR) samples were investigated by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and limiting oxygen index (LOI) tests. Due to the relatively high phosphorus content of PDAP (18.2 wt%), incorporation of this monomer into unsaturated polyester resin (UPR) led to a marked decrease in the heat release capacity (HRC), the total heat release (THR), an increase in the LOI and the char yield upon combustion. In order to elaborate the interactions between the UPR and PDAP in degradation, differences between the experimental and theoretical mass losses of a FR-UPR sample were evaluated. Furthermore, thermogravimetry-Fourier transform infrared (TG-FTIR) and real-time Fourier transform infrared (RTIR) spectroscopy were employed to investigate the degradation behavior of UPRs, providing insight into the degradation mechanism.     

A study of the combustion and fire-retardance behaviour of unsaturated polyester/phenolic resin blends

The thermal degradation and combustion behaviour of an interpenetrating network (IPN) structure of unsaturated polyester UP resin and a resole type of phenolic resin was studied. Thermal gravimetric analysis (TGA) was used to monitor the degree of thermal decomposition for the UP/phenol IPN structure and the change of the oxygen index (OI) was used to describe the variation of the combustion behaviour. The smoke density was measured via a non-flaming process to detect the amount of smoke generated during the combustion. A homemade cone calorimetric dynamic flammability evaluation system was assembled to analyse the gas evolved and to measure the heat release rate (HRR) during the combustion. Under simulated conditions of a burning field at the temperature of 757°C, the variation of the concentration of carbon monoxide (CO) and the HRR of the UP/phenol IPN structure were studied. The results show that modification of the essentially flammable UP resin by the phenol structure to form an IPN system cannot only remarkably improve the heat resistance but also help to suppress the smoke, toxic gas and heat release during the combustion.     

Thermal degradation and fire resistance of unsaturated polyester, modified acrylic resins and their composites with natural fibres

The thermal degradation and fire resistance of different natural fibre composites were studied. Unsaturated polyester (UP) and modified acrylic resins (Modar) were used as matrix composites. The smoke emission of the materials was also analysed, as well as, the performance against the fire of the biocomposites and glass reinforced composites was compared. Thermal degradation indicated that the Modar matrix composites were more resistant to temperature than the composites with UP matrix. Flax fibre, due to their low lignin content, exhibit the best thermal resistance among the natural fibres studied.From the results obtained about the thermal and fire resistance of the composites it is possible to conclude that the flax fibre seems to be the most adequate to be used, due to the long time to ignition and the long period prior to reach the flashover. On the other hand, the jute fibre composites showed a short duration but a quick growing fire with the lowest smoke emission. The low smoke is an important advantage, which reduces one of the main hazards of fire.     

Chemical recycling of networked polystyrene derivatives using subcritical water in the presence of an aminoalcohol

Subcritical water is a benign and effective media for polymer degradation. On subcritical water treatment in the presence of an aminoalcohol, unsaturated polyesters crosslinked with styrene were decrosslinked, and a linear polystyrene derivative bearing hydroxy-terminated side-chains was recovered. After modification of the hydroxy groups with maleic anhydride, the polystyrene derivative was re-crosslinked with styrene to form a networked structure again. The resulting solid was degradable by subcritical water treatment in the presence of the aminoalcohol to give another polystyrene derivative bearing hydroxy groups. These processes could be repeated successfully, demonstrating the applicability as a novel recycling system of thermosetting resins. The polystyrene derivative was also re-crosslinked again on heating with an alternative copolymer of styrene and maleic anhydride due to the formation of linkage between the hydroxy groups and carboxylic anhydride moieties.     

DSC and TSDC Study of Unsaturated Polyester Resin. Influence of the promoter content

This work reports on the curing kinetics of unsaturated polymer resins (UPRs) cured with styrene, studied by differential scanning calorimetry and Fourier transform infrared spectroscopy. The data lead to determination of the experimental conditions with which to obtain a fully cured material and open the way for study of the relaxation phenomena by means of thermally stimulated depolarization current analysis (TSDC). In relaxation studies on fully cured resins, the TSDC spectra revealed important overlapping of the main relaxation peak with an extra upper peak. The importance of this extra peak a priori prevents further analysis of the main relaxation. To identify the origins of this peak (space charge or other), the purity of the resin was checked by X-ray fluorescence spectroscopy. The use of UPR specimens with different compositions (in terms of the resin/activator/initiator ratio) demonstrated that the bulk of the impurities Cl, K, Ca, Sr, Zr and Ba are due to the promoter. Decoupling of the mixed peaks (α-relaxation and extra) revealed that the a peak is independent of the proportion of the promoter in the resin and that the extra peak is principally due to the presence of these impurities. This revised version was published online in July 2006 with corrections to the Cover Date.     

Polyanhydride modified unsaturated polyesters as injectable drug carriers: Synthesis and antitumor efficacy in Sarcoma-180 mice bearing tumor

New polyanhydride modified unsaturated polyesters, poly(dodecanedioic acid-tetradecanedioic acid) [P(DDDA-TA)] modified poly(fumaric acid-glycol) [P(FA-GLY)] copolymers, were prepared by melt polycondensation with corresponding polyanhydride and unsaturated polyester synthesized beforehand. The polyanhydride was characterized by FT-IR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), the liquid poly(fumaric acid-glycol) [P(FA-GLY)] and polyanhydride modified unsaturated polyesters were characterized by FT-IR, gel permeation chromatography (GPC) and viscosity of the polymers was measured with a Ubbelohde viscometer. In vitro studies showed that some of the copolymers are degradable in phosphate buffer at 37 °C and have properly drug release rate as drug carriers. The biocompatibility of P(DDDA-TA)-P(FA-GLY) copolymers under mice skin was also evaluated; macroscopic observation and microscopic analysis demonstrated that the copolymer is biocompatible and well tolerated in vivo. Antitumor efficacy of P(DDDA-TA) [molar ratio M_DDDA:M_TA = 1.0:1.0, 20% weight ratio in polyanhydride modified unsaturated polyester]-P(FA-GLY) [molar ratio M_FA:M_GLY = 1.0:1.1] containing 5% adriamycin hydrochloride (ADM) in Sarcoma-180 mice bearing tumor exhibited increased volume doubling time (VDT) (21 ± 1.5 days) compared to plain subcutaneous injection of adriamycin hydrochloride (ADM) (7 ± 1.0 days), and the antitumor efficacy of injected preparation of P(DDDA-TA)-P(FA-GLY)-ADM inside tumor twice intervene 16 days exhibited an especially increased cytotoxic effect as revealed by increased volume doubling time (VDT) (32 ± 2.5 days). The studies suggested that P(DDDA-TA)-P(FA-GLY) copolymers as an effective and injectable carrier of antineoplastic drug like adriamycin hydrochloride have a very good foreground in treatment of noumenon tumor.