A combined CFD modeling and experimental study of pyrolytic carbon deposition

Understanding the chemical reaction mechanism and deposition kinetics is of great importance to guide the production of pyrolytic carbon (PC). A practical approach to mimic the commercial chemical vapor deposition (CVD) process and eventually predict the PC deposition rate is highly desired. In this work, a simplified two-step reaction mechanism was proposed for the CVD of PC, with the first step in the gas phase and the second step on the substrate surface. The kinetic parameters were determined by trial and error using a computational fluid dynamics simulation. The velocity, temperature, and concentration profiles in a cold-wall, forced-flow reactor were modeled based on the geometry and experimentally determined boundary conditions. The computed PC deposition rates for substrate temperatures between 700 and 3000 °C were in good accordance with experimental results. Rate limiting steps were observed for both the deposition experiments and simulations. Mass-transport-limited and reaction-limited regimes were identified in wide temperature and flow rate ranges. A higher deposition rate was found in a cold-wall reactor compared with those in an insulated reactor or a hot-wall reactor. Finally, the PC microstructure was characterized using optical microscopy, scanning electron microscopy, Raman spectroscopy, and X-ray diffraction, demonstrating progressive development of graphitization with increasing deposition temperature.     

基于APP平台的TDC-3000 DCS实时数据存取技术

探讨了基于Honeywell APP平台的TDC-3000 DCS实时数据采集方法,阐述了通讯系统的构成和软件的设计思路,并进一步研究了基于B/S结构的DCS实时数据在局域网上的存取和应用问题。此技术已获成功应用并具有通讯系统结构简单、技术可靠、实施成本低等特点。     

Solvent effects on esterification equilibria

Solvents are known to have strong impacts on the yields of equilibrium reactions. This work focuses on the thermodynamic investigation of these solvent effects on esterification reactions of acetic acid and propionic acid with ethanol. Esterification of acetic acid was performed in the solvents acetone, acetonitrile (ACN), dimethylformamide (DMF), and tetrahydrofurane as well as in mixtures thereof. ACN promotes the esterification of acetic acid, whereas it is strongly suppressed by DMF. The esterification of propionic acid was investigated with various reactant concentrations in acetone. The experimental equilibrium data in pure solvents and solvent mixtures were modeled using the thermodynamic equilibrium constant K_a and the reactant/product activity coefficients predicted by the perturbed chain‐statistical associating fluid theory (PC‐SAFT). For a given K_a, PC‐SAFT is able to predict the influence of the solvent and even solvent mixtures on the equilibrium concentrations of esterification in almost quantitative agreement with the experimental data. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3000–3011, 2015     

热氧老化对聚碳酸酯结构和性能的影响

分别在90～120℃环境下,对聚碳酸酯(PC)进行人工热氧加速老化实验.研究PC老化后的结构性能变化和热氧老化机理.结果表明:在低于120℃温度条件下,老化120 h后,PC仍显示强而韧的性能,但断裂伸长减小;在120℃温度条件下,老化24 h后,PC拉伸断裂伸长消失;PC的热氧降解过程主要是以热诱导氧化降解反应,降解反应引起端基、侧基从主链断裂脱落,导致内部缺陷,力学性能随之下降.     

聚烯烃弹性体增韧改性聚碳酸酯的研究

用四种聚烯烃弹性体对聚碳酸酯（PC）进行了增韧改性。探讨了不同种类和用量的增韧剂对聚合物共混物力学性能的影响。结果表明，EVA的加入使共混物韧性改善最明显，当其用量为15％时，材料的缺口冲击强度提高至38．7kJ／m^2，为纯PC的25倍，但材料的拉伸强度急剧下降。POE—g—MAH对PC的增韧效果仅次于EVA，但共混物的拉伸强度降低程度比EVA小，且共混物的断裂伸长率提高很多。其它两种共混体系PC／EAA、PC／LLDPE-g—MAH的性能介于EVA和POE—g—MAH之间。综合考虑材料的各种机械性能，添加20％的POE—g—MAH的PC共混物的性能较佳。     

Co-continuous polycarbonate/ABS blends

Co-continuous PC/ABS (50/50) blends were studied with a variable polybutadiene (PB) content (0-40%) in ABS. Polycarbonate (PC), styrene-acrylonitrile (SAN) and PB were blended in two steps using a twin screw extruder. Rectangular bars were injection moulded and notched Izod impact tested at different temperatures and in single edge notch tensile tests at 1 m/s and different temperatures. Co-continuous PC/ABS gave a brittle-to-ductile transition temperature lower than expected based on notched Izod results for dispersed ABS in PC. The brittle-to-ductile transition temperature, in the co-continuous PC/ABS blends, decreased with increasing rubber content in SAN. The fracture energies showed an optimum at 15% PB in SAN while at the same time a delamination was seen on the ductile fracture surface, due to failure of the PC/SAN interface. Delamination disappeared when the rubber content in SAN or the temperature was increased. Specimens containing a welding were injection moulded to study the influence of rubber and AN content in the SAN on the interface. Weldline strength of the blends was very poor compared to PC, but improved with increasing rubber content in SAN.     

无卤阻燃PC/ABS合金流变行为的研究

采用毛细管流变仪研究无卤阻燃聚碳酸酯/丙烯晴-丁二烯-苯乙烯共聚物（PC/ABS）的流变行为,得到了熔体表观黏度及切应力与剪切速率的关系。结果表明,无卤阻燃PC/ABS合金熔体为假塑性流体,表观黏度随剪切速率的增加而降低;在230 ℃时,合金的非牛顿指数随着阻燃剂含量的增加而增加;在剪切速率为20~3000 s-1时,合金黏度对温度不敏感,即实现黏度降低,采用升温法效果不佳。     

Hydrolysis of polycarbonate to yield BPA

Elevated temperatures and high humidity decrease the molecular weight and impact strength of polycarbonate. Hydrolysis of injection molded polycarbonate (PC) bars stored in glass containers at 85°C and 96% relative humidity (RH) produced brown surface crystals within 30 days. Aging of PC bars at 96% RH and temperatures of 70°C and lower for longer periods of time formed a brown liquid coating on the PC. X-ray, DSC, and GPC measurements indicated that about 70 wt% of the surface crystals were bisphenol A (BPA). The remaining portion of hydrolysis products appeared to be higher molecular weight oligomers of BPA. The brown liquid was composed of supercooled liquid BPA, BPA oligomers, and water. Initial growth of BPA on the surface of a PC bar took place at the interface between the PC and the glass wall of the container. Apparently a water soluble extract from the glass container accelerated the hydrolytic degradation of PC; nevertheless, hydrolysis of PC occurred in the absence of glass—although at a slower rate. Hydrolysis studies were carried out on several commercial PC formulations. The PC resin containing only a heat stabilizer was least affected. Of the fiame retardant grades, the brominated PC hydrolyzed less rapidly than these particular compositions containing alkali metal sulfonic acid salts. A glass fiber reinforced PC was less stable than its unfilled parent compound. A hydrolytic stabilizer was ineffective against the attack of water under these conditions.     

Rate-dependent large deformation behavior of PC/ABS

Rate-dependent large deformation behavior of the alloy of polycarbonate and acrylonitrile-butadiene-styrene (PC/ABS) is experimentally investigated over a crosshead speed range of 1-3000 mm/min. Three-dimensional non-contact digital image correlation (DIC) method is used to measure the large deformation of polymer specimens. Numerical simulation of geometry effect on the necking process of specimens is done for the specimen with two section sizes. It is found that the width contracts less than the thickness due to its larger size than the thickness for specimens with rectangular sections, and the relations between two lateral contraction ratios and engineering strains are geometry dependent, but independent of loading speeds. The influence of strain rates on local volume ratios of PC/ABS is also discussed. Based on the experimental results, a simple phenomenological constitutive model with six parameters is proposed for the glassy polymer, in which the effect of strain rate and its variation during constant crosshead speed loading tests is considered, and can be used in constant true strain rate or constant principal stretch rate loading condition.     

Electron beam irradiation of polycarbonate reinforced acrylonitrile butadiene rubber

The effects of electron beam irradiation and polycarbonate (PC) concentration on the properties of acrylonitrile butadiene rubber (NBR) were investigated. The electron beam irradiation doses were from 25 to 150 kGy, whereas the PC contents were from 10 to 30 phr. It was found that the mechanical properties of NBR such as tensile strength (TS), hardness and tear strength (Ts) were remarkably improved by the incorporation of PC, while elongation at break (E_b) and thermal properties were decreased. However, the improvement in TS of NBR/PC blends was strongly dependant on PC content, in which maximum improvements need higher doses. On the other hand, the maximum value of Ts for all the blend ratios was at 25 kGy, whereas the hardness increases with increasing irradiation dose. Moreover, it was observed that the fuel resistance of NBR/PC was higher than NBR and decreases by increasing the content of PC.     

Enzymatic method of increasing phosphatidylcholine content of lecithin

An enzymatic method was established to increase the phosphatidylcholine (PC) contents of soybean and egg lecithins. Other phospholipids of lecithin were phosphatidylethanolamine (PE), phosphatidylinositol (PI) and phosphatidic acid (PA). Seven preparations of phospholipase D (PLD), PLD-1 to PLD-6 ofStreptomyces origin and PLD-7 of cabbage origin, were tested for their ability to increase PC by transphosphatidylation in the presence of choline chloride (CC). The reactions were carried out at 30 C in a biphasic system that consisted of an aqueous phase containing PLD along with a buffer (optimum pH) having desired concentration of CC and Ca²⁺ and an ethyl acetate phase containing lecithin phospholipids. Intermitttent samples were extracted and analyzed by HPLC. Four of six PLD’s ofStreptomyces origin showed good transphosphatidylation (increase of PC contents of soybean lecithin from approximately 35% to 60–70% on a phospholipid basis) at 2.5 M CC, but the other two microbial PLD’s completely hydrolyzed the phospholipids to PA. Cabbage PLD-7 showed poor transphosphatidylation. PLD-3 gave the highest PC contents (70%) at 1.75 M CC. One hundred percent transphosphatidylation of pure PE to PC was achieved with PLD-3. PI was inert to the attack of most PLD preparations examined with the exception that PLD-3 hydrolyzed PI significantly. Purified PI could not be transphosphatidylized to PC; 100% PA was formed. Soybean lecithin containing about 80% PC and purified egg yolk lecithin with 75% PC could be converted to products having 95% PC and almost 100% PC, respectively, by PLD-3 at 1.75M CC. Studies on Enzymatic Conversion of Phospholipids (v)     

FDM用PETG系列耗材的改性研究

对市售聚对苯二甲酸乙二醇酯-1,4-环己烷二甲醇酯（PETG）丝材及原材料进行研究,选用PETG 2012作为制备熔融堆积成型技术（FDM）用PETG丝材的基体树脂。选用聚碳酸酯（PC）对基体PETG进行增韧增强改性,并制成3D打印高分子丝材进行打印测试,探讨了PC含量对PETG耗材及制件性能的影响。结果表明,在低PC含量下,PETG与PC的相容性较好,PETG与PC制件未出现明显的分层,分布比较均匀;共混物的流动性随着PC含量的增加而降低,且打印件的维卡软化温度和热变形温度随着PC用量的增加而增加;此外,PC材料的加入使得PETG打印件的力学性能得到较大改善：打印件的拉伸强度随着PC用量的增加而增大,缺口冲击强度却随着PC用量的增加呈现先增加后减小的趋势; PETG/PC的配比为1∶1时,可制得力学性能优异的3D打印耗材。     

Hot embossing in microfabrication. Part I: Experimental

The relationship among processing conditions, material properties, and part quality in hot embossing was investigated for three optical polymers: polycarbonate (PC), polymethyl methacrylate (PMMA), and polyvinyl butyral (PVB). A series of systematic embossing experiments was conducted using mold inserts having either single or multiple feature depths. The feature dimensions varied from 90 to 3000 μm. The processing conditions studied include embossing pressure, thermal cycles, and heating methods. The displacement profile, replication accuracy and molded‐in stresses were measured experimentally. It was found that for isothermal embossing, both replication accuracy and birefringence pattern depend strongly on the processing conditions. For non‐isothermal embossing, the molded parts showed excellent replication as long as the feature transfer was completed. The flow pattern under isothermal embossing resembles a biaxial extensional flow. Under non‐isothermal embossing, the polymer deformation involves an upward flow along the wall of mold features, followed by downward compression and outward squeezing. Rheological characterization and hot embossing analysis are presented in Part II.     

Morphologies and tensile properties of elastomer-modified epoxy and polycarbonate blended systems

The morphologies and tensile properties of an elastomer-modified epoxy (EME)/polycarbonate (PC) binary system and an EME/diglycidyl ether of bisphenol A (DGEBA)/PC ternary system were examined. In the EME system, a continuous elastomer-rich phase formed, while in the EME/DGEBA systems (unblended with PC), a continuous epoxy-rich phase formed. In both of these systems, two-phase structures were observed. In contrast, a microdispersed structure was observed when the PC was blended with either the EME or with the EME/DGEBA systems. It is suggested that blending of the epoxy with PC caused an increased solubility of the former into the elastomer phase. The tensile strength and tensile elongation of both the EME and EME/DGEBA systems were improved by blending with PC. In the EME/PC blend, the tensile elongation reached its maximum value (60%) at a PC content of approximately 10 p.h.r. (parts per hundred resin by weight), with this maximum being approximately one and a half times higher than that of the unblended EME. Tensile strength was also clearly increased by blending with small amounts of PC, but soon reached a steady value. In the EME/DGEBA/PC blends, the tensile properties were dependent on the weight ratio of EME to DGEBA. In the absence of PC, as this ratio increased, the tensile elongation also increased, while at the same time the tensile strength decreased. The tensile properties were also improved in this system, by blending with PC. From the results obtained, it was clear that the improvement in tensile properties was closely related to the changes in morphology. Therefore, blending of the PC induced a microdispersed structure and improved the elongation of the epoxy resin.     

光盘回收PC改性ABS树脂研究

用光盘回收的聚碳酸酯（PC）树脂制备了丙烯腈-丁二烯-苯乙烯共聚物（ABS）/PC合金,探讨了回收PC含量、增容剂种类对合金力学性能的影响。结果表明,ABS/PC合金的拉伸强度随回收PC含量的增加而逐渐增大,冲击强度则呈先增长后下降的趋势,在回收PC含量为10 %（质量分数,下同）时达到最大值;增容剂甲基丙烯酸甲脂-丁二烯-苯乙烯共聚物（MBS）比甲基丙烯酸环氧丙酯接枝乙烯-辛烯共聚物（POE-g-GMA）更能改善ABS和PC的相容性,显著提高合金冲击强度,当回收PC含量为5 %时,用MBS增容的ABS/PC合金的冲击强度比纯ABS提高了42.8 %。     

ABS树脂中胶含量对PC/ABS合金性能及微观结构的影响

采用胶含量(质量分数,下同)为60％的丙烯腈-丁二烯-苯乙烯接枝共聚物(ABS)接枝粉料与苯乙烯-丙烯腈共聚物(SAN)以不同比例进行共混,制备了胶含量范围为10％～55％的ABS树脂.将胶含量不同的ABS树脂与聚碳酸酯(PC)以30/70、50/50、70/30的质量比利用熔融共混技术,制备了组成不同的PC/ABS共混物,考察了ABS树脂胶含量对不同组成的PC/ABS合金性能的影响.研究结果表明:随着ABS树脂中胶含量的增加,ABS树脂的冲击强度不断提高,屈服强度、模量及熔体流动速率逐渐降低.随着PC/ABS合金中ABS胶含量的增加,合金的冲击强度显著提高,ABS树脂中胶含量大于30％以后,合金的冲击强度变化不大,且3种组成的PC/ABS合金的冲击强度相差不大.合金的屈服强度、模量及熔体流动速率却随着ABS中胶含量的增加不断降低,其中组成为30/70的PC/ABS合金最低.利用扫描电镜观察了PC/ABS组成为70/30合金的微观结构,研究表明,ABS树脂形成连续相,PC为分散相,随ABS树脂胶含量的增加,合金的相形态变得更精细.     

In situ composites from blends of polycarbonate and a thermotropic liquid‐crystalline polymer: The influence of the processing temperature on the rheology,morphology, and mechanical properties of injection‐molded microcomposites

This work was aimed at understanding how the injection‐molding temperature affected the final mechanical properties of in situ composite materials based on polycarbonate (PC) reinforced with a liquid‐crystalline polymer (LCP). To that end, the LCP was a copolyester, called Vectra A950 (VA), made of 73 mol % 4‐hydroxybenzoic acid and 27 mol % 6‐hydroxy‐2 naphthoic acid. The injection‐molded PC/VA composites were produced with loadings of 5, 10, and 20 wt % VA at three different processing barrel temperatures (280, 290, and 300°C). When the composite was processed at barrel temperatures of 280 and 290°C, VA provided reinforcement to PC. The resulting injection‐molded structure had a distinct skin–core morphology with unoriented VA in the core. At these barrel temperatures, the viscosity of VA was lower than that of PC. However, when they were processed at 300°C, the VA domains were dispersed mainly in spherical droplets in the PC/VA composites and thus were unable to reinforce the material. The rheological measurements showed that now the viscosity of VA was higher than that of PC at 300°C. This structure development during the injection molding of these composites was manifested in the mechanical properties. The tensile modulus and tensile strength of the PC/VA composites were dependent on the processing temperature and on the VA concentrations. The modulus was maximum in the PC/VA blend with 20 wt % VA processed at 290°C. The Izod impact strength of the composites tended to markedly decrease with increasing VA content. The magnitude of the loss modulus decreased with increasing VA content at a given processing temperature. This was attributed to the anisotropic reinforcement of VA. Similarly, as the VA content increased, the modulus and thus the reinforcing effect were improved comparatively with the processing temperature increasing from 280 to 290°C; this, however, dropped in the case of composites processed at 300°C, at which the modulus anisotropy was reduced. Dynamic oscillatory shear measurements revealed that the viscoelastic properties, that is, the shear storage modulus and shear loss modulus, improved with decreasing processing temperatures and increasing VA contents in the composites. Also, the viscoelastic melt behavior (shear storage modulus and shear loss modulus) indicated that the addition of VA changed the distribution of the longer relaxation times of PC in the PC/VA composites. Thus, the injection‐molding processing temperature played a vital role in optimizing the morphology‐dependent mechanical properties of the polymer/LCP composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

The effects of PC‐PMMA block copolymer on the compatibility and interfacial properties of PC/SAN blends

Block copolymers of polycarbonate (PC) and polymethylmethacrylate (PMMA), PCb‐PMMA, were examined as compatibilizers for blends of PC with styrene‐co‐acrylonitrile (SAN) copolymer. PC‐b‐PMMA was added to blends of PC with SAN containing various amounts of AN. The average diameter of the dispersed particles was measured with an image analyzer, and the interfacial properties of the blends were analyzed with an imbedded fiber retraction (IFR) test and an asymmetric double cantilever beam fracture test. The average particle size and interfacial tension of the PC/SAN blends reached a minimum value when the SAN copolymer contained about 24 wt% AN. A maximum in the adhesion energy was also observed at the same AN content. Interfacial tension and particle size were further reduced by adding PC‐b‐PMMA to the PC/SAN blends. Fracture toughness of the blends was also improved by enhancing the interfacial adhesion by the addition of PC‐b‐PMMA. The addition of PC‐b‐PMMA copolymer was more effective at improving the interfacial properties of PC/SAN blends than was varying the AN content of the SAN copolymers. The interfacial properties of the PC/SAN blends were optimized by adding a block copolymer and using an SAN copolymer that had minimum interaction energy with PC.     

Properties of polycarbonate/acrylonitrile‐butadiene‐styrene/talc composites

The morphology, tensile, impact properties, and thermal expansion behavior of polycarbonate (PC)/acrylonitrile‐styrene‐butadiene (ABS)/talc composites with different compositions and mixing sequences were investigated. From the studies of morphology of the PC/ABS/talc composites, it was observed that some talc particles were located in both the PC and the ABS phases of the blend but most were at the interface between the PC and ABS phases for every mixing sequence. Aspect ratios of the talc particles determined by TEM image analysis reasonably matched values computed from tensile modulus using composite theory. The thermal expansion behavior, or CTE values, was not significantly influenced by the mixing sequence. The impact strength of the PC/ABS/talc composites depended significantly on the mixing sequence; a premix with PC gave the poorest toughness. The molecular weight of the PC in PC/talc composites was found to be significantly decreased. It appears that the impact strength of the PC/ABS/talc composites is seriously compromised by the degradation of the PC caused by talc. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

水稻秸秆与煤粉混合燃烧特性及动力学

采用热重分析法研究了水稻秸秆(RS)、煤粉(PC)及两者不同掺混比的混合物在不同升温速率下(10, 20, 40℃/min)从室温升至1000℃的燃烧特性，用Kissinger?Akahira?Sunose (KAS)法和Flynn?Wall?Ozawa (FWO)法计算了燃烧过程中的活化能。结果表明，失重速率(DTG)曲线中RS比PC多一个失重峰，且残余质量低。随升温速率增加，所有样品DTG曲线均向高温偏移，产生热滞后现象。RS和PC在混合燃烧过程中存在协同效应，且高温区域内更显著。PC掺混比例为50wt%时，混合物平均活化能的计算值较低，仅为76.0 kJ/mol (KAS)和83.2 kJ/mol (FWO)。