甲醇制烯烃(MTO)反应器分布管堵塞原因分析及措施

为解决反应器分布管堵塞导致分布管压差上涨问题,寻求解决方法。对影响反应器分布管堵塞的因素,如MTO装置急冷水、水洗水、浓缩水、废甲醇水、压缩机段间凝液等进行试验和对分布管堵塞原因进行分析。通过优化污水汽提塔操作,控制污水汽提塔塔顶出料冷后温度高于120℃,将污水汽提塔塔顶的低温冷却器切换至高温冷却器和控制较低的pH值(8.0),减少了堵塞物的生成;对不凝气及浓缩水进行工艺改造优化了污水汽提塔的操作,解决了反应器分布管的堵塞问题。含有一定浓度醛酮类物质的浓缩水,在碱性环境中可以发生缩聚反应,在污水汽提塔系统内生成交联物,导致反应器分布管的堵塞。     

Accelerated photo-aging of organic coatings used as protective layers for Blu-ray Discs

This article aims to evaluate the impact of UV-light irradiation on the chemical structure and functional properties of organic coatings used to protect the surface and the stored data of Blu-ray Discs. In order to provide a methodology that can make a direct relation between the modification of the chemical structure and the functional properties, a cross-linked aromatic polyester resin with a well-known chemical structure was first studied in photolysis and photooxidation conditions. Characterization of the aging of this material by spectroscopic, calorimetric and thermo-mechanical analyses highlighted chemical and molecular changes linked to the well-known photo-reactivity of the ester functional group (Norrish types I and II reactions, photooxidation, etc.). The photochemical behavior of a real acrylic-based Blu-ray Disc coating was then investigated in the same conditions. Focusing on the influence of photo-aging on the functional properties of the coating, this work showed that on the one hand, the optical and mechanical changes had dramatic effects on the reading of the Blu-ray Disc, but on the other hand, a positive impact of aging was revealed with a significant decrease in the permeability of the coating due to post-cure reactions.     

Effect of aldehydes on thermomechanical properties of gluten-based bioplastics

Protein–protein crosslinks play an important role in the design of biodegradable polymeric materials requiring suitable rheological and mechanical properties. The addition of aldehydes to the bioplastic formulation may result in their involvement in some form of protein cross-linking. The objective of this contribution is to evaluate the effect of adding some aldehydes (formaldehyde, glutaraldehyde and glyoxal) on the thermomechanical properties of gluten-based biodegradable polymeric materials processed by a mixing stage followed by compression moulding at 9 MPa and 130 °C. Different bioplastic probes were evaluated by means of DMA measurements, recording the elastic and loss moduli as a function of temperature and uniaxial tensile strength tests. Water absorption capacity and solubility under different extraction media of bioplastic specimens, were also evaluated. Solubility measurements were carried out in order to analyse the effect of the aldehyde on the nature of the interactions taking place in the system, being compared to those performed on blends previous to the moulding process. Glyoxal is the aldehyde that seems to produce bioplastics with best thermal and mechanical properties. This study would contribute to evaluate the potentials of adding aldehyde to gluten/plasticiser systems to control the microstructure and properties of the final bioplastics.     

The impact of baking conditions on physico-chemical characteristics influencing topography and appearance aspects of polyurethane coatings

The appearance aspects of an electrodeposited polyurethane-based coating as a function of baking condition were investigated. Specular gloss and color was measured as a mean to trace the changes of the surface topography due to baking conditions. Atomic force microscopy combined with FTIR spectroscopic investigations showed that the shrinkage occurred due to the high baking temperature results in surface roughness. Films baked at higher temperature form higher-T_g networks. The color was changed to yellow as the baking temperature was raised.     

Development of new high-throughput screening method to compare and to detect efficient catalysts for adhesive materials

Organotin compounds particularly dibutyltin dilaurate, are commonly used as catalysts in coatings or adhesive materials to crosslink silyl modified polymers. However, environmental concerns should lead before 2020 to ban organotin compounds due to their high toxicity. Thus new catalysts must be developed. According to the different types of catalytic systems, i.e. acid, basic or metal containing catalysts, a large variety of candidates should be tested. Thus a high-throughput screening (HTS) method could be an interesting tool for the detection of new efficient catalysts to substitute organotin compounds. We report a global HTS method, compatible with organic amino or acid catalysts libraries, as well as with metal-containing libraries.     

The influence of oxidizing agents on water extracts of rye flour

The main constituents of rye flour extracts are proteins and pentosans. After cross-linking under the action of oxidizing agents those components are able to bind much more water than in their native (prior to modifications) state. As a consequence rheological properties of extract are changed.It was observed that kinematic viscosity of water extract of rye flour decreases rapidly with time. The reason for this behavior could be high enzymatic activity of flour extract.It was also found that the addition of hydrogen peroxide in the absence of additional peroxidase (which is naturally present in 1:9 or 1:1 water extracts of flour) causes the greatest increase in viscosity, due to the cross-linking of soluble polymers. Moreover after the addition of H₂O₂ to water extracts strong gels were obtained, which were characterized by tan δ = 0.5 (tan δ < 1). Moreover G′ was independent of frequency, which also suggests cross-linking of the pentosans.The addition of ascorbic acid, which is known to act preferably on gluten proteins, to 1:9 or 1:1 flour extracts had only a little effect on viscosity. In this case the values of tan δ = 0.9 were close to 1, which is typical for a weak gel.The application of inactivated rye flour extract, containing mainly proteins and pentosans, proved stronger effect of H₂O₂ in comparison to ascorbic acid on polymer cross-linking, but only after the addition of peroxidase. The gel obtained with H₂O₂ and peroxidase was also characterized by low tan δ = 0.4.The results indicate, that pentosans are the main subject of cross-linking reactions in rye flour water extracts.     

Cross-linked soy protein as material for biodegradable films: Synthesis, characterization and biodegradation

The modification of soy protein isolate (SPI) with different amounts of a naturally occurring cross-linking agent (genipin, Gen) and glycerol used as plasticizer was carried out in this work. The films yielded were cast from heated and alkaline aqueous solution of SPI, glycerol and Gen and then dried in an oven. Total soluble matter, water vapor permeability and mechanical properties were improved by adding small amounts of Gen. These properties were not significantly affected (P ? 0.05) by additions exceeding 2.5% (w/w of SPI). The opacity and cross-linking degree were linearly increased with the addition of Gen, whereas the swelling ratios in water were decreased. All the films were submitted to degradation under indoor soil burial conditions and the weight loss of the films was measured at different times. This study revealed that the film biodegradation time can be controlled or modified from at least 14 to 33 days. The tests performed showed the potential of Gen to improve the SPI film properties, in which the possibility of employing such new films as biodegradable food packaging was raised.     

Cycling performance of a lithium-ion polymer cell assembled by in-situ chemical cross-linking with fluorinated phosphorous-based cross-linking agent

Lithium-ion polymer cells composed of a carbon anode and a LiCoO₂ cathode are assembled with a gel polymer electrolyte cured by in-situ chemical cross-linking with novel cross-linking agents. The strong interfacial adhesion between the electrodes and the porous polyethylene membrane by the chemical cross-linking results in the stable capacity retention of the cell. However, a reduction in the ionic mobility in both the electrolyte and the electrodes adversely affects the high rate performance of the cell. These results imply that proper control of the cross-linking density in the cell is imperative for achieving good capacity retention and high rate performance of the cell.     

Preparation and Mechanical Properties of Cross-Linked Polyphosphazene Elastomers Based on Urethane Oligomers

Linear poly [bis-(phenoxy)_1.8 (4-hydroxybutaneoxy)_0.2 phosphazene] (PPHBP) was synthesized and characterized by FTIR, NMR and GPC. Then, PPHBP was cross-linked by different ratio of toluene diisocyanate and 1, 4-butanediol mixtures at mild temperature to prepare PPHBP elastomers. The FTIR spectral analysis demonstrated that the elastomers' chemical composition was the same with our expectations. Tensile testing results indicated that the tensile strength increased from 0.053 to 7.9 MPa and the break elongation approached from 1.82 to 68.7%. The novel cross-linked method might open a simple and economic route to preparing polyphosphazene elastomers.     

Preparation of Silane-Grafted and Moisture Cross-Linked Low Density Polyethylene: Part I: Factors Affecting Performance of Grafting and Cross-Linking

In the present work, the silane grafting and water cross-linking of low density polyethylene (LDPE) were investigated. The grafting reaction was carried out in an internal mixer and polyethylene cross-linking was done in hot water. The effect of silane, peroxide, catalyst, carbon black, cross-linking time, and cross-linking temperature on the grafting and cross-linking processes are reported. Vinyl trimethoxy silane (VTMO) and di-cumyl peroxide (DCP) were selected as grafting agent and initiator respectively. Silane grafting on polyethylene was determined using Fourier transform infrared (FTIR) spectroscopy and torque monitoring of the mixer. Absorption peak due to –Si–OCH₃ groups in FTIR and torque increasing due to silane grafting in the mixer illustrated that silane-grafting reactions occurred. The FTIR data demonstrated that the extent of silane grafting was increased as the concentration of silane and peroxide was increased. Thermogravimetry analysis (TGA) determined that the thermal stability of LDPE increased by increasing the amount of silane grafting. Gel fraction increased with silane and peroxide concentration. As the percent of of catalyst increase the time scale for specified gel content shifted to shorter times. Incorporation of carbon black into LDPE decreased the extent of silane grafting and gel fraction. Water temperature increasing in cross-linking stage reduced the time to maximum degree of cross-linking.