ZnO与Mg(OH)_2在软PVC中的协同阻燃消烟作用

用热分析的方法研究了ZnO和Mg(OH)2复合阻燃剂对软PVC的协同阻燃消烟作用,考察了经阻燃处理的软PVC从室温到800℃的热降解过程,用Kissinger方程给出了热降解反应的活化能。通过极限氧指数(LOI)、剩炭率、烟密度等级(SDR)和最大烟密度(MSD)的测定以及用电子扫描显微镜(SEM)对燃烧后所生成炭层的观察,探讨了协同体系阻燃抑烟的机理。结果表明:经阻燃处理的样品尤其是加入适量ZnO和Mg(OH)2复合阻燃剂的样品具有较高的极限氧指数(LOI)和剩炭率、较低的烟密度等级(SDR)和最大烟密度(MSD),与未处理的样品相比具有较好的阻燃和消烟性能。ZnO的加入可改变PVC的热降解过程,使起始降解温度降低,并且使反应的活化能增大,可能属于固相Lewis酸催化机理。     

SnO2与氢氧化物复合阻燃剂对软PVC的阻燃消烟作用

研究了SnO2和无机氢氧化物阻燃剂对软PVC的阻燃消烟作用。通过热分析的方法研究了阻燃处理后的软PVC从室温到800℃的热降解过程,通过剩炭率的测定以及用电子扫描显微镜(SEM)对燃烧后所生成炭层的观察探讨了不同体系的阻燃抑烟的机理。结果表明:经SnO2和氢氧化物复合阻燃处理的样品具有较高的极限氧指数(LOI)和剩炭率,烟密度等级(SDR)和最大烟密度(MSD)明显降低,与未处理的样品相比具有较好的阻燃和消烟性能。SnO2的加入可改变PVC的热降解过程,使起始降解温度降低,SnO2可能是在凝聚相和气相同时起作用,但主要是在凝聚相起Lewis酸催化作用。     

系列羟基锡酸盐对半硬质PVC的阻燃消烟作用

研究了系列羟基锡酸盐阻燃剂对半硬质PVC的阻燃消烟作用。通过对样品燃烧后剩炭含量及扫描电镜(SEM)分析,探讨了锡酸盐体系阻燃抑烟的机理。结果表明:经阻燃处理的样品具有较高的极限氧指数(LOI)和剩炭率,较低的烟密度等级(SDR)和最大烟密度(MSD),与未处理的样品相比具有较好的阻燃和消烟性能。由于阻燃剂的添加量较少,对材料力学性能影响不大。     

金属配合物对软聚氯乙烯的阻燃消烟作用

利用热分析的方法研究了以Al(OH)3和Mg(OH)2为基础，含有Fe、Co、Ni或Cu的金属配合物的复合阻燃剂对软聚氯乙烯(PVC)的阻燃消烟作用。研究了软PVC从室温到1073K的热降解过程。利用Kissinger方程给出了其动力学参数。结果表明：阻燃处理过的软PVC具有较好的阻燃消烟性能，如较高的氧指数和剩炭率，较低的烟密度等级和最大烟密度，力学性能有所降低。     

羟基锡酸锌包覆硫酸钡的制备以及在软PVC中的阻燃应用

通过均匀沉淀法制备了羟基锡酸锌包覆硫酸钡(ZHSCB)样品,并与硫酸钡(BaSO4)对比应用于软PVC的阻燃消烟处理。利用X-射线衍射(XRD)及扫描电子显微镜(SEM)等手段对ZHSCB进行了表征,并通过极限氧指数(LOI)和烟密度等级(SDR测试)研究了ZHSCB对PVC的阻燃消烟作用。通过热分析的方法研究了阻燃PVC从室温到800℃的热降解过程。通过拉伸强度和断裂伸长率测定了ZHSCB对PVC的力学性能的影响。结果表明:ZHSCB对PVC有优异的阻燃消烟作用,能够有效促进PVC第一降解阶段的脱HCl反应,促进交联成炭反应的进行以及剩炭稳定性的提高,并且对于PVC的力学性能影响较小。     

羟基锡酸三聚氰胺盐及羟基锡酸金属盐复合物阻燃PVC的阻燃性能及热性能研究

合成了四种羟基锡酸三聚氰胺盐及羟基锡酸金属盐复合物,并作为新型膨胀阻燃剂应用于软聚氯乙烯(PVC)的阻燃消烟处理。极限氧指数(LOI)及烟密度等级(SDR)测试表明,这些复合物是软PVC有效的阻燃消烟剂。利用热重分析(TGA)、差热分析(DTA)并结合扫描电子显微镜(SEM)研究了阻燃PVC的热降解过程。结果表明:这些复合物不但能够在降解第一阶段降低PVC的起始分解温度,提高失重速率,而且能够促进PVC在第二阶段生成膨胀型的炭层。     

SnO2和SiO2用于PVC的阻燃消烟及协同作用

研究了二氧化锡和二氧化硅对软PVC阻燃消烟性的影响。通过对极限氧指数、剩炭率、烟密度的测定和DTATG曲线的分析证明,添加8g二氧化锡/二氧化硅复合阻燃剂的PVC的氧指数和剩炭率比未添加的分别增高5.5个单位和4.1%,烟密度降低16.4%,降解活化能分别降低38kJ/mol和23.1kJ/mol,从而证明二氧化锡/二氧化硅复合阻燃剂对于PVC是一种很好的阻燃消烟剂,二氧化锡和二氧化硅有很好的协同作用。同时证明这种复合阻燃剂能代替三氧化二锑,使产品的成本进一步降低。     

高分子粘结膜与金属化合物对PVC树脂的协同阻燃消烟作用

研究了铝塑复合板中高分子粘结膜与Mg(OH)_2和CaCO_3复合阻燃剂对PVC树脂的协同阻燃消烟作用。通过NBS烟箱等仪器测试的有关参数对PVC体系中的金属化合物及填料的抑烟、阻燃效果进行了分析和研究。结果表明：在高分子粘结膜和金属化合物协同作用下能使烟密度(MSD)和生烟速率显著降低,而且有效地推迟了发烟时间。各种金属化合物对PVC体系的氧指数(LOI)影响不大,对烟密度的影响差异很大。     

模板法合成锡酸钴及其对PVC的阻燃应用

以活性炭为模板、五水四氯化锡和六水硝酸钴为原料,制备纯相的多孔锡酸钴（CoSnO3）阻燃剂,通过X射线衍射（XRD）和扫描电镜（SEM）对其结构、形貌进行表征,并将其应用于PVC的阻燃研究中。当CoSnO3的添加量为15份时,其极限氧指数（LOI）达到35.6％、烟密度等级（SDR）为75.2％、断裂伸长率为168.32%、拉伸强度为 22.50 MPa。通过热重分析（TGA）对阻燃前后PVC的热降解行为进行了初步探讨,研究发现： 经CoSnO3阻燃处理后,PVC样品的初始降解温度降低,高温时的剩炭量增加,表明CoSnO3对PVC材料具有较好的阻燃消烟性能。     

LaFeO_3的合成及其在软质PVC中的阻燃应用

采用高温煅烧法合成了钙钛矿型铁酸镧(LaFeO3)。探讨了煅烧温度及时间对反应产物的影响,通过X射线衍射(XRD)对LaFeO3进行了表征,确定高温煅烧的最佳条件为800℃下煅烧4 h。通过极限氧指数(LOI)、烟密度等级(SDR)及锥形量热(CONE)测试研究了LaFeO3对软质PVC阻燃及消烟性能的影响,使用热重分析(TGA)考察了LaFeO3对PVC热降解过程的影响。结果表明:LaFeO3能有效地降低PVC燃烧过程中的发烟量,使样品燃烧的热释放速率(HRR)、烟释放速率(SPR)以及总烟释放量(TSP)等明显降低;LaFeO3主要在PVC降解的第二阶段发挥阻燃消烟作用,大量稳定的残炭的生成是LaFeO3具有优异消烟性能的主要原因。     

Victrex® poly(ethersulfone) (PES) and Victrex® poly(etheretherketone) (PEEK)

Properties of two high performance engineering thermoplastics, amorphous polyethersulfone (PES) and semicrystalline polyetheretherketone (PEEK), are discussed. Both resins can be processed by conventional techniques, compounded with high performance fibers, and have high service temperature (up to 300°C). Due to the amorphous character PES can be dissolved and spray coated into metals.     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(styrene-co-acrylonitrile) and poly(p-methylstyrene-co-acrylonitrile)

The miscibility of poly(methoxymethyl methacrylate) (PMOMA) and poly(methylthiomethyl methacrylate) (PMTMA) with poly(styrene-co-acrylonitrile) (SAN) and poly(p-methylstyrene-co-acrylonitrile) (pMSAN) was studied by differential scanning calorimetry. PMOMA is miscible with SAN having an acrylonitrile (AN) content around 30 wt %. However, PMOMA is immiscible with any of the pMSAN having AN contents between 9 and 36 wt % and with pMSAN having AN contents between 19 and 34 wt %. The miscibility of the blends enables the evaluation of various segmental interaction parameters.     

Photo-Initiated Lamination of Polyethylene (PE) and Poly(ethylene terephthalate) (PET)

Besides plasma-based processes, photo-initiated surface modifications have an interesting potential for adhesion promotion. This is of special interest with applications ranging from classical finishing to composites. Photo-chemical processes using continuous UV sources — monochromatic as well as broad band — are based on radical activation and ensuing reaction with the atmosphere. Achievable effects are addition of atoms — e.g., introduction of oxygen (photo-oxidation) resulting in increased surface energy — or grafting of functional groups. Both have certain potentials for adhesion promotion in a physico-chemical way. Based on the fundamental scheme of these processes — i.e., a photon-initiated radical reaction at the substrate-atmosphere interface — a direct 'inter-linking' of coating polymer and substrate is presented in this paper. The principal idea is to apply a thin layer of coating polymer on the substrate and irradiate this composite system at certain UV wavelengths. Given a low absorption of the radiation by the thin coating and — at the same time — a high absorption by the substrate, the radiation will penetrate the coating layer and generate radicals at the interface, which will induce cross-linking between the coating polymer and substrate. It is shown that for the example of laminates of polyethylene (PE) film on fabrics made of poly(ethylene terephthalate) (PET), extremely high adhesion strenghths are achieved without any use of additional adhesion promoters.     

Photooxidative stability of substituted poly(phenylene vinylene) (PPV) and poly(phenylene acetylene) (PPA)

The addition of side groups to improve the photooxidative stability of polymers used in polymer-based light-emitting diodes (LEDs) is explored. Infrared spectroscopy and computational chemistry techniques are used to study the effects of chemical substitution of the reactive vinylene moiety in poly(phenylene vinylene) (PPV). The bond order of the vinylene group in small oligomers is calculated using semiempirical techniques to assess the improvement in stability toward oxidants such as singlet oxygen. We find that PPV dimers allow relative comparisons across a range of possible substitutions. Experimental results correlate well with these calculations. The addition of electron-withdrawing substituents, such as nitrile groups, to the vinylene moiety is found to be particularly effective in reducing the reactivity of alkoxy-substituted PPV toward singlet oxygen. The photooxidative stability of a poly(phenylene acetylene) (PPA) derivative is also studied. It appears that this family of polymers is more stable toward photooxidation than are its PPV analogs. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2451–2458, 1998     

Co(II) and Ni(II) Concentration,and Co(II) Purification with Microbiological Collectors (Saccharomyces cerevisiae)

Abstract

Co(II) and Ni(II) can be concentrated quantitatively using a microbiological collector consisting of a Saccharomyces cerevisiae strain suspended in a glucose containing phosphate buffer. Optimal conditions for such accumulation as regards pH, time, and concentration have been studied. The influence of some complexing agents on the accumulation of a mixture of Co(II) and Ni(II) has also been investigated. By adapting the Saccharomyces cerevisiae strain to Co(II), separation of Co(II) from Ni(II) in dilute solution has been achieved.     

Finite strain behavior of poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate)-glycol (PETG)

Uniaxial and plane strain compression experiments are conducted on amorphous poly(ethylene terephthalate) (PET) and poly(ethylene terephthalate)-glycol (PETG) over a wide range of temperatures (25-110 °C) and strain rates (.005-1.0 s⁻¹). The stress-strain behavior of each material is presented and the results for the two materials are found to be remarkably similar over the investigated range of rates, temperatures, and strain levels. Below the glass transition temperature (θ_g=80 °C), the materials exhibit a distinct yield stress, followed by strain softening then moderate strain hardening at moderate strain levels and dramatic strain hardening at large strains. Above the glass transition temperature, the stress-strain curves exhibit the classic trends of a rubbery material during loading, albeit with a strong temperature and time dependence. Instead of a distinct yield stress, the curve transitions gradually, or rolls over, to flow. As in the sub-θ_g range, this is followed by moderate strain hardening and stiffening, and subsequent dramatic hardening. The exhibition of dramatic hardening in PETG, a copolymer of PET which does not undergo strain-induced crystallization, indicates that crystallization may not be the source of the dramatic hardening and stiffening in PET and, instead molecular orientation is the primary hardening and stiffening mechanism in both PET and PETG. Indeed, it is only in cases of deformation which result in highly uniaxial network orientation that the stress-strain behavior of PET differs significantly from that of PETG, suggesting the influence of a meso-ordered structure or crystallization in these instances. During unloading, PETG exhibits extensive elastic recovery, whereas PET exhibits relatively little recovery, suggesting that crystallization occurs (or continues to develop) after active loading ceases and unloading has commenced, locking in much of the deformation in PET.     

Rheological behavior of blends of poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-stat-styrene)-graft-polybutadiene (ABS)

The rheological behavior of blends of poly(methyl methacrylate) (PMMA) and poly(acrylonitrile-stat-styrene)-graft-polybutadiene (ABS) was investigated using a cone-and-plate rheometer. The rheological properties measured were shear stress (σ₁₂), viscosity (η), and first normal stress difference (N₁) as functions of shear rate (\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma$ \end{document}) in steady shearing flow, and storage modulus (G′) and loss modulus (G″) as functions of frequency (ω) in oscillatory shearing flow. It has been found that the rheological behavior of blends of ABS and PMMA was very similar to that of blends of poly(styrene-stat-acrylonitrile) (SAN) and PMMA, in that N₁ in logarithmic plots of N₁ versus σ₁₂, and G′ in logarithmic plots of G′ versus G″, vary regularly with blend composition. This has led us to conclude that the rubber particles that are grafted on an SAN resinous matrix in ABS resin plays only a minor role in influencing the compatibility of ABS/PMMA blends, and that the SAN chains attached to the surface of rubber particles, and the SAN matrix phase, play a major role in compatibilizing ABS resin with PMMA.     

Synthesis and characterization of new poly(butadiene-co-acrylic acid(g) acrylic acid) and poly(butadiene(g) acrylic acid)

Synthetic crosslinked polymers from oligomers of butadiene-co-acrylic acid (Mw 5000) or oligomers of butadiene (Mw 6000) and acrylic acids were obtained after grafting reactions using varying reactant ratios. Characterization of the new crosslinked polymers were carried out by use of FTIR, H-NMR, and ¹³C-NMR in the solid state and also with the swollen products in D₂O, DMF D7, or DMSO D6. Determinations of swelling in distilled water for the different synthesized hydrogels showed increase in the V/Vo ratios as the concentrations of anions (carboxylate) became higher. These values were sensitive to different pH values and changes in the concentrations of electrolytes. Different behavior was observed for the polymers obtained from mass and from synthesis in benzene. SEM analysis of the surfaces of the polymers obtained in mass showed a fibrous structure (with lower contents of carboxylic groups, and more swellable and with greater capacity to retain albumin). A porous surface was observed for products obtained in benzene (with higher content of carboxyl groups and capacity to retain cations such as copper and malachite green).     

Polymerization and characterization of bis(trichlorophenolato)di(pyridine) nickel(II) and bis(tribromophenolato)di(pyridine) nickel(II) dihydrate complexes in solution in the presence of iodine

The syntheses of bis(trihalophenolato)di(pyridine) nickel(II) complexes were achieved in aqueous solution, and their characterizations were performed by Fourier transform infrared (FTIR) spectroscopy, ultraviolet‐visible analysis, differential scanning calorimetry, and elemental analysis. The thermal polymerization of these complexes was studied in toluene solution in the presence of iodine. The effect of time, temperature, and amount of iodine added on the percentage conversion, structure of polymers, and intrinsic viscosity ([η]) were investigated. Polymers were characterized by FTIR, ¹H‐NMR, and ¹³C‐NMR spectroscopic analyses, glass‐transition temperatures determined by differential thermal analysis, and [η] values determined by the viscometric method. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2232–2239, 2002