Dynamics of intumescence of fire-retardant polymeric materials

A new numerical method allowing one to estimate a temperature field in an intumescent fire-retardant coating is proposed. The data on heat conductivity of the material, on kinetics of its decomposition, and on kinetics of change of its rheological properties serve for calculation of input parameters. On the basis of experimental information about curing kinetics, the algorithm computes a viscosity of the material in each elementary layer of the coating. It is assumed that the local change of viscosity, in turn, predetermines a local expansion coefficient of the coating. The results of the calculations are compared with the experimental data obtained for the coating on the basis of phenol–formaldehyde resin and boron oxide. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1523–1542, 1998     

超临界流体技术在聚合物加工中的应用

简要介绍了超临界二氧化碳的性质及其在聚合物科学中的应用优势，结合目前国内外超临界流体技术在聚合物加工中应用的最新进展，重点介绍了超临界流体技术在聚合物结晶，发泡聚合物的制备，共混聚合物的加工和共混聚合物膜的相分离中的应用。     

高固含量水性聚氨酯的合成及其成膜性能的研究

采用预聚体分散法制备出50%以上固含量的水性聚氨酯,考察了软链段分子链长及硬链段含量对聚氨酯相分离行为、热性能及力学性能等的影响。研究表明:硬链段含量、软链段链长的提高和离子基团的增加均有利于拉伸强度的提高。     

Role of thermodynamic miscibility gaps in phase selection in sol-gel synthesis of yttrium silicates

Yttrium monosilicate and disilicate are important materials for environmental barrier coatings. The two silicates were synthesized by sol-gel route and their phase selection upon calcination and thermal exposure was studied. First products of crystallization were the monosilicate and yttria. Amorphous silica precipitated out at 1300 °C as apatite phase. During prolonged high temperature treatment, up to 100 h at 1400 °C, the apatite disappeared and the disilicate appeared, only to disappear itself as the system approached equilibrium. Thermodynamic calculations performed using Thermo-Calc software show the presence of a metastable miscibility gaps in the amorphous (liquid) phase field. As a consequence, phase separation in the amorphous phase prior to crystallization is responsible for the formation of yttria-rich and silica-rich phases during crystallization. Multiple phase formation during both, yttrium monosilicate and disilicate synthesis is consistent with the presence of the amorphous phase miscibility gaps around the silicate compositions.     

新型反应型P-N膨胀型阻燃剂的合成及其在棉织物中的应用

以三聚氯氰、亚磷酸三乙酯和丙三醇为原料合成了一种新型结构的反应型P-N膨胀型阻燃剂三氧代(3-亚磷酸乙酯-5-氯-1-三嗪)丙三醇(TTCTG),并通过红外光谱(FTIR)、核磁共振氢谱和磷谱分析对其进行了结构表征,热重分析(TGA)表明TTCTG有优良的热稳定性能。以TTCTG为原料对棉纤维进行了阻燃改性,通过极限氧指数(LOI)和垂直燃烧实验测试表明当阻燃整理液中TTCTG的质量浓度为20%时,阻燃整理后棉织物(20%TTCTG-CF)的氧指数为27.3,阻燃等级可达国家标准B1级,TGA分析表明TTCTG在284℃便能促进棉织物快速分解成炭,700℃下的残炭率高达为35.7%,扫描电镜(SEM)分析发现20%TTCTG-CF燃烧后,其表面形成了致密的膨胀炭层,TTCTG阻燃整理后的棉纤维表现出了优异的阻燃性能。耐水性研究表明水洗20次后的20%TTCTG-CF的阻燃等级仍可达B1级,极限氧指数可达26.4,通过SEM和FTIR对水洗20次后20%TTCTG-CF进行结构分析,研究表明TTCTG与棉纤维通过共价键相连而融为一体,赋予棉纤维优良持久的阻燃性能。     

Thermodynamic Modeling of Phase Diagrams in Binary Alkali Silicate Systems

A thermodynamic modeling of phase diagrams in binary alkali silicate systems is described by using the Gibbs free energy of the phases. Simple models employing regular, quasi-regular, and subregular solution models were applied to describe the liquid phase. The interaction parameters of the liquid phases were obtained by using the liquidus curves of silica (and subliquidus data) through a multiple linear regression method. The present calculated liquidus curves agree very well with Cs₂O—SiO₂ and Rb₂O—SiO₂ systems. In the K₂O—, Na₂O—, and Li₂O—SiO₂ systems, the calculations permitted discrimination between sets of data and, based upon the calculation choices, could be correctly made to select the most appropriate phase diagram. Also, the spinodals were calculated where phase separation can occur by a spinodal decomposition process.     

Quantitative estimation of the reinforcing effect of layered silicates in PP nanocomposites

Various polypropylene/layered silicate composites were prepared with different silicate contents. Montmorillonites with and without organophilization as well as three maleinated polypropylenes were used to change the extent of exfoliation and hence the properties of the composites. Structure was characterized by X-ray diffraction (XRD), scanning (SEM) as well as transmission electron microscopy (TEM) and tensile properties were also measured. The analysis of the tensile yield stress values of a large number of composites showed a broad range of variation in mechanical properties. XRD and TEM results do not reflect the differences in properties and they usually do not give quantitative information about the extent of exfoliation either. PP/clay composites containing maleinated PP, which do not exhibit a silicate reflection in XRD, may have very poor mechanical properties indicating small extent of exfoliation. The composition dependence of tensile yield stress of these composites may be described and evaluated quantitatively by a simple model developed earlier for particulate filled polymers. The use of a few simple assumptions most of which are supported by previous results allows us to estimate the extent of exfoliation quantitatively. The tensile yield stress of about 40 composites was analyzed with the model. Some of the composites were prepared by us, while results on others were taken from papers published in the literature. The analysis indicated that the extent of exfoliation is very low in most composites; it reaches maximum 8% of the theoretically possible value in the best case. This result is in agreement with our observation that complete exfoliation can be seldom reached in thermoplastic/clay composites; the structure is complex and hierarchical including large particles and individual silicate layers. The results prove that further efforts must be done to increase the extent of exfoliation in order to achieve reinforcement levels forecasted earlier.     

Morphology development and crystallization behavior of a poly(ethylene terephthalate)/polycarbonate blend

The morphology development and crystallization behavior of an extruded poly(ethylene terephthalate)/polycarbonate blend were studied with optical microscopy, light scattering, and differential scanning calorimetry (DSC). During annealing at 280°C, liquid–liquid phase separation via spinodal decomposition proceeded in a melt‐extruded specimen. After the formation of the domain structure, the blend slowly underwent phase homogenization by transesterification between the two polymers. The specimen, annealed for various times (t_s's) at 280°C, was subjected to a temperature drop to 180°C for the isothermal crystallization, and then the effects of liquid‐phase changes on crystallization were investigated. The crystal growth rate decreased with t_s. The slow crystallization with a large t_s value was associated with the composition change of the separated phases and the change of the sequence distribution in the polymer chains during annealing. The influence of t_s on the endothermic behavior of the samples was examined. As t_s increased, the recrystallization rate was retarded during the DSC scan, displaying multiendothermic behavior. The DSC data also suggested that the increased level of transesterification would give rise to a higher number of species being rejected from the primary crystals, leading to enhanced secondary crystallization. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Phase separation in semicrystalline polymer blends and copolymers studied via thermal segregation and crystallization kinetics

The miscibility versus immiscibility in a crystalline two component system is discussed, based on phase separation and crystallization kinetics considerations. The thermal segregation was used to create or enhance the phase separation in crystalline two component systems. By comparing the crystallization kinetics before and after thermal segregation, one can distinguish two types of phase separation: (1) intrinsic phase separation in the melt for an immiscible system, or (2) phase separation induced via crystallization for a miscible system. Metallocene short‐chain branching polyethylene (SCBPE) and nylon 6/polyimide triblock copolymer systems were taken as examples, and the phase behaviour determined via this thermal segregation and crystallization kinetics method. It is evident that the crystallization kinetics after thermal segregation are substantially faster than that before thermal segregation, and become much faster after keeping the sample in the melt for some time for the SCBPE system. Our results suggest that the molecules with different SCB contents in the SCBPE system may exhibit liquid–liquid phase separation in the melt. In contrast, studies on the crystallization kinetics of the nylon 6/polyimide system showed that nylon 6/polyimide triblock copolymer exhibits lower phase separation compared with in situ or solution blends. Thermal segregation and crystallization kinetics may serve as a very useful method to study the phase behaviour in semicrystalline blends and copolymers. © 2000 Society of Chemical Industry     

TiO2对硫铁尾矿玻璃晶核作用的影响研究

运用差热分析(DTA),X射线衍射分析(XRD)和扫描电镜(SEM)等分析手段研究了以TiO2作晶核剂时CaO-MgO-SiO2-Al2O3系统尾矿微晶玻璃析晶特征.结果表明:TiO2作为晶核剂的核化机理是首先促进玻璃的分相,然后析出金红石晶体来诱导异相成核.它能使在相图中确定的组成点向高Al2O3方向偏移.合理控制热处理条件可获得性能良好的主晶相为透辉石的矿渣微晶玻璃.     

A survey of the rheological properties,phase morphology,and crystallization behavior of PP-POSS materials with weak phase separation

Polypropylene (PP) compounds with varying amounts (0.4-8.2 vol%) of tailored allyl-isobutyl polyhedral oligomeric silsesquioxane (POSS) were prepared by melt-blending. The dependence of the crystallization behavior and crystalline structure of PP on the melt-state phase morphology of PP-POSS materials is addressed. PP-POSS systems were predicted to exhibit weak phase separation in both the molten and solid states based on Bagley plot using Hansen solubility parameters. Small-amplitude shear rheometry analysis suggested that the highest loaded (8.2 vol%) PP-POSS system behaves as a two-liquid emulsion, whereas the low-content POSS (0.4-4.0 vol%) systems deviate from this model, resembling a polymer nanocomposite. Based on these findings we hypothesized the formation of a heterogeneous phase morphology in the molten state comprised of nano-size “pseudo-solid” POSS clusters and micrometer-size “pseudo-liquid” POSS droplets dispersed within the PP matrix, depending on the POSS content. Upon cooling, POSS droplets comingle, forming cube-like micrometer-sized crystal domains. The nonisothermal crystallization of PP is enhanced by the presence of POSS clusters. Small-angle X-ray scattering analysis revealed the formation of thinner and more heterogeneous folded chain PP lamellae in the PP-POSS systems.     

以Fe2O3作晶核剂的尾矿玻璃陶瓷晶化研究

运用差热分析（ＤＴＡ）、扫描电镜（ＳＥＭ）、Ｘ射线衍射（ＸＲＤ）、能谱分析（ＥＤＡＸ）等测试手段,研究了以 Ｆｅ２Ｏ３作晶核剂时ＣａＯ－Ａｌ２Ｏ３－ＳｉＯ２系统尾矿玻璃陶瓷析晶特征。结果表明,Ｆｅ２Ｏ３降低了玻璃整体析晶温度,并在热处理时诱导玻璃分组,从而促进成核和晶相生长。合理控制热处理条件可获得性能良好的尾矿玻璃陶瓷材料。     

Thermal analysis of polymer–water interactions and their relation to gas hydrate inhibition

Gas hydrates formed in oil production pipelines are crystalline solids where hydrocarbon gas molecules such as methane, propane, and their mixtures are trapped in a cagelike structure by hydrogen‐bonded water molecules to form undesirable plugs. Methanol and glycol are currently used to prevent these plugs via thermodynamic inhibition. Small amounts of water‐soluble polymers may provide an alternate approach for preventing gas hydrates. In this study, we expand the fundamental understanding of water–polymer systems with differential scanning calorimetry. Nonfreezable bound water was used to quantify polymer–water interactions and relate them to the chemical structure for a series of polymers, including acrylamides, cyclic lactams, and n‐vinyl amides. For good interactions, the water structure needs to be stabilized through hydrophobic interactions. An increased hydrophobicity of the pendant group also appears to favor polymer performance as a gas hydrate inhibitor. Good inhibitors, such as poly(diethyl acrylamide) and poly(N‐vinyl caprolactam), also show higher heat capacities, which indicate higher hydrophobicity, than poor performers such as polyzwitterions, in which hydrophilicity dominated. The phase behavior and thermodynamic properties of dilute polymer solutions were also evaluated through measurements of the heat of demixing and lower critical solution temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2642–2653, 2007     

Preparation and characterization of poly(ethylene‐co‐vinyl alcohol) membranes via thermally induced liquid–liquid phase separation

Porous membranes were prepared through the thermally induced phase separation of poly(ethylene‐co‐vinyl alcohol) (EVOH)/glycerol mixtures. The binodal temperature and dynamic crystallization temperature were determined by optical microscopy and differential scanning calorimetry measurements, respectively. It was determined experimentally that the liquid–liquid phase boundaries were shifted to higher temperatures when the ethylene content in EVOH increased. For EVOHs with ethylene contents of 32–44 mol %, liquid–liquid phase separation occurred before crystallization. Cellular pores were formed in these membranes. However, only polymer crystallization (solid–liquid phase separation) occurred for EVOH with a 27 mol % ethylene content, and the membrane morphology was the particulate structure. Scanning electron microscopy showed that the sizes of the cellular pores and crystalline particles in the membranes depended on the ethylene content in EVOH, the polymer concentration, and the cooling rate. Furthermore, the tendency of the pore and particle sizes was examined in terms of the solution thermodynamics of the binary mixture and the crystallization kinetics. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 853–860, 2003     

Phase separation in aqueous casein- guar gum systems

Summary Phase separation in aqueous mixtures of guar gum and casein, containing micellar casein, sodium caseinate or its β and k-fractions was investigated, and the effects of the state of casein [colloidal-dispersed (∼0.3 μm), molecular-dispersed associated, and dissociated] were established by the determination of the phase diagrams. Phase separation occurring in moderately concentrated mixtures was depended on ionic strength and was not depended on the state of protein. Passing from dissociated to molecular-dispersed associated and then to colloidal-dispersed casein result in a decrease of the total concentration in the threshold point (C^*_t) in accordance to C^*_t∝M_w^0.27, and in increasing asymmetry of phase diagrams. In the two-phase region, the degree of compatibility was dependent on pH and ionic strength of mixtures, varying according to the change of casein -solvent interaction.     

Phase Distribution and Transparency in Glass-Ceramics Based on a Study of the Sodium Niobate–Silica System

High transparency in the NaNbO₃ crystal–silica glass system at low silica content is attributed to maintenance of the glass-to-glass phase separation pattern in microstructure throughout the process of crystallization. Optical properties are explained by a characteristic of the phase-separated glass, internal connectivity, applicable in this case to both crystal and glass phases. This type of microstructure allows light propagation in each phase independently, without interference between phases. Deviation from this ideal behavior and light-scattering mechanisms which may apply to different phase distribution patterns here and in other glass-ceramic systems are discussed.     

Crystallization Behavior and Multiferroic Properties of Bi3.15Nd0.85Ti3O12/CoFe2O4 Powders Synthesized by Sol–Gel Method

Bi_3.15Nd_0.85Ti₃O₁₂ (BNdT)/CoFe₂O₄ (CFO) composite ceramic powders with embedded structures were successfully prepared by sol–gel processing. Their crystallization behavior was characterized by XRD, DTA, FT‐IR, and HRTEM. The magnetic and ferroelectric phases of these composite ceramic powders segregate during calcination. The CFO phase forms easily at ~300°C, thereafter the BNdT matrix phase nucleates with grain growth at the CFO grain boundaries at temperatures >500°C. The CFO phase acts as a heterogeneous nucleation point for formation of the ferroelectric BNdT phase. Furthermore, the 0.5BNdT–0.5CFO composite ceramic powders go through a ferroelectric–paraelectric phase transition at 259°C, and the magnetic CFO nanoparticles (50–100 nm, under calcination at 600°C) embedded in the ferroelectric matrix, show superior magnetic behavior (M_max = 16.50 emu/g), comparable to pure CFO nanoparticles.     

Adsorption of Hg(II) in aqueous solutions using mercapto‐functionalized alkali lignin

A novel adsorbent for Hg(II), mercapto‐functionalized alkali lignin (AL‐SH) was synthesized by Friedel–Crafts alkylation reaction and nucleophilic substitution reactions. The adsorbent was characterized by the techniques of Fourier transform‐infrared spectroscopy (FT‐IR), elementary analysis and thermogravimetric analysis, and N₂ adsorption techniques. The effect of various parameters on Hg(II) adsorption process such as initial pH, contact time, ionic strength, initial Hg(II) concentration, temperature, and adsorbent dosage were investigated in detail through batch static experiments. The results indicated that the adsorption process of Hg(II) on AL‐SH was mainly dependent on the pH and the optimal pH value was at pH ranging from 4.0 to 6.0. The adsorption process was found to follow pseudosecond‐order kinetics and the main process was chemical adsorption, which equilibrated at 8 h. The adsorption isotherm was better described by Langmuir and Temkin isotherm equations compared to Freundlich isotherm equation and the maximum adsorption capacity obtained was 101.2 mg g^?1 (pH = 4.0, 20°C, initial Hg(II) concentration was 200 mg L^?1). The thermodynamic parameters of and were positive while was negative, revealed that the adsorption of Hg(II) onto AL‐SH was a spontaneous and endothermic process with increased entropy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40749.