Studies on some properties of pristine and iodine-doped poly(phenylene sulphide)

Some properties of poly(phenylene sulphide) prepared by direct synthesis from benzene and sulphur are discussed in the light of thermal analysis, X-ray, SEM, and infrared data. Pristine poly(phenylene sulphide) is characterized by great thermal stability; it loses only 22.5% of its mass during dynamic heating to 873 K. Mass loss for iodine-doped samples increases to 41% depending on the iodine content. Doping with iodine also changes crystallinity, morphology and brings about a rise of electrical conductivity by several orders of magnitude. A conductivity of 1.45 × 10^–2 S m^–1 was obtained in air at room temperature for the poly(phenylene sulphide) sample containing 22.6% iodine.     

Effects of thermal history on crystal structure of poly(phenylene sulphide)

The lattice parameters of film-grade poly(phenylene sulphide), PPS, have been studied at room temperature as a function of thermal history. Effects of crystallization temperature and annealing time for films crystallized from the rubbery amorphous state were investigated using wide- and small-angle X-ray diffraction, bulk density and thermal analysis techniques. The dimensions of the crystal lattice are found to depend upon prior thermal treatment conditions. As the cold crystallization temperature, T _c, increases, or the annealing time at fixed temperature increases, the bulk density, degree of crystallinity, and crystal perfection increase. With an increase in annealing time at fixed temperature, lattice a, b, and c decrease leading to an increase in lattice density. As the cold crystallization temperature increases, lattice density also increases as a result of a systematic decrease in lattice parameters a and b.     

Characterization of a water-dispersible metal protective coating with Fourier transform infrared spectroscopy, modulated differential scanning calorimetry, and ellipsometry

An ethylene-methacrylic acid copolymer, formulated by BASF as a waterborne suspension of its alkylammonium salt and used, among other applications, in art conservation as a temporary protective coating was characterized using Fourier transform infrared (FT-IR) spectroscopy aided by modulated differential scanning calorimetry (MDSC) and ellipsometry. The thermal conversion of thin copolymer films from the freshly applied state, where carboxylic acid and carboxylate ion functional groups co-exist, to a purely acidic working state was spectroscopically followed. Transmission mid-infrared data of the working state showed a 1 : 12 ratio of methacrylic acid towards ethylene units. The glass transition temperature (T(g)) in the same state was found at 45 °C. Copolymer films spin-coated on mechanically polished bronze and iron coupons were characterized with transflection infrared spectroscopy and compared to corresponding transmission mid-infrared spectra of copolymer films spin-coated on silicon wafers. In the case of bronze coupons, evidence for interaction of the carboxylate ion with the copper substrate was obtained. The chemical structure and the thermal behavior of the coating, as well as some implications on its protective capability towards iron and copper alloys, is discussed as this material has received considerable attention in the field of metal conservation and coatings.     

Use of modulated differential scanning calorimetry to observe vitrification during epoxy resin cure

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Mechanical and electrical properties of carbon nanotube/poly(phenylene sulphide) composites incorporating polyetherimide and inorganic fullerene-like nanoparticles

The mechanical and electrical properties of single-walled carbon nanotube (SWCNT) reinforced poly(phenylene sulphide) (PPS) composites prepared by melt-extrusion have been evaluated. The wrapping of SWCNTs in polyetherimide (PEI) and the addition of inorganic fullerene-like tungsten disulfide (IF-WS₂) nanoparticles provided an effective method for dispersing the SWCNTs, leading to enhanced properties of the resulting hybrid composites. Mechanical tests demonstrated significant enhancements in stiffness, strength and toughness by the addition of both nanofillers, and the Young’s modulus of the hybrid composites was fairly well predicted by two-phase modelling. The electrical conductivity of PPS improved dramatically at low SWCNT content (0.1-0.5 wt%). At higher concentrations, the replacement of part of the SWCNTs with IF-WS₂ maintained the level of conductivity of the composites. Overall, the hybrids possess superior performance than composites reinforced solely with wrapped or non-wrapped SWCNTs, and their properties can be tailored by modifying the SWCNT/IF-WS₂ ratio.     

Characterization of molecular orientation by differential scanning calorimetry

Differential scanning calorimetry was used to study relaxations occurring above the glass transition, T _g for a number of characterized and fabricated polystyrenes. Part 1 of this study examines the liquid-liquid relaxation temperature, T _LL; Part 2 the effects of injection moulding and biaxial orientation of polystyrene; and Part 3 deals with the effects of injection blow moulding.The rubbery plateau region was found to be bounded by the glass transition, T _g, and a weak transition or relaxation, T _LL, found above T _g as an endothermic slope change in the base line. In some cases, this transition could be enhanced as a step change when molten samples were quenched in liquid nitrogen.The effect of molecular weight on T _g and T _LL was similar, and had the relationships T _LL/T _g=1.07+0.03 forM _inw/M _n 1, and T _LL/T _g=1.15 ± 0.01 for ¯M _w/¯M _n > 1.     

Enhancing the thermomechanical behaviour of poly(phenylene sulphide) based composites via incorporation of covalently grafted carbon nanotubes

The thermal and thermomechanical properties of poly(phenylene sulphide) (PPS) based nanocomposites incorporating a polymer derivative covalently anchored onto single-walled carbon nanotubes (SWCNTs) were investigated. The grafted fillers acted as nucleating agents, increasing the crystallization temperature and degree of crystallinity of the matrix. They also enhanced its thermal stability, flame retardancy, glass transition (T_g) and heat deflection temperatures while reduced the coefficient of thermal expansion at temperatures below T_g. A strong rise in the thermal conductivity, Young’s modulus and tensile strength was found with increasing filler loading both in the glassy and rubbery states. All these outstanding improvements are ascribed to strong matrix-filler interfacial interactions combined with a compatibilization effect that results in very homogeneous SWCNT dispersion. The results herein offer useful insights towards the development of engineering thermoplastic/CNT nanocomposites for high-temperature applications.     

Microindentation and differential scanning calorimetry of “liquid wood”

Lignin was used only as a fuel until not so long ago, but the research done in the last few years has shown that it is a substance that confers wood its strength and takes the form of granules that may be melted. Thus, lignin was used to produce a material out of which almost anything can be manufactured, from furniture, accessories, toys, plastic cases for electronic devices, and food containers of any shape, to car bodies, and which is known as “liquid wood”. Its properties recommend “liquid wood” as an alternative to all plastic products in the near future, as it is biodegradable and reusable several times, and its properties remain intact. Three types of “liquid wood” are known: Arbofill, Arboblend and Arboform. Whereas Arboform is 100% biodegradable, the other two materials are only partially biodegradable. The following types of “liquid wood” were used: Arbofill Fitchie, Arboblend V2 Nature and Arboform L, V3 Nature. The research described in this paper focuses on the study of microindentation and differential calorimetry. Also, the software package we used enabled us to read both the microhardness values, and the reduced indentation modulus and Young’s modulus.The studied test samples showed the following mean recovery values: 45.9170 μm for Arbofill Fitchie, 22.2783 μm for Arboblend V2 Nature and 17.7430 μm for Arboform L, V3 Nature. These values are in agreement with the microhardness and modulus of elasticity values. Differential calorimetry research has shown that Arboblend V2 Nature and Arboform L, V3 Nature suffered two transformations each, one endothermal and the other exothermal, during which we measured the transformation onset and completion temperatures, as well as the temperature in the middle of the transformation process. We also measured the amount of absorbed and dissipated heat, respectively. As far as Arbofill Fitchie is concerned, the DSC diagram showed no temperature-dependent heat flow variation that could suggest a solid state transformation. We could safely state that the Arbofill Fitchie sample is thermally stable up to a temperature of 423 K.     

Studies of RbF-BeF2 glasses by differential scanning calorimetry

The heat capacity, softening temperature, and crystallization temperature of RbF-BeF₂ (10, 15, 18, 22, and 27 mol % RbF) glasses were measured by differential scanning calorimetry. The results lend support to the view that RbF-BeF₂ glasses are diphasic. The glasses studied are shown to contain fragments of (BeF₃) _n ^-n fluoroberyllate chains and to be close in many aspects to KF-BeF₂ glasses.     

Characterization of amorphous and nanostructured Si films by differential scanning calorimetry

Over the last 5 years, we have successfully applied differential scanning calorimetry (DSC) to study silicon thin films. The aim of this paper is to review our main results to give an overview of the possibilities offered by this technique, which is widely used to characterize solid state transformations. We will address some classical subjects related to the structure of pure and hydrogenated a-Si, such as the strength of the Si–H bond, hydrogen diffusion and the contribution of structural defects and strained bonds to the enthalpy of structural relaxation and crystallization. Special attention will be paid to the crystallization kinetics of films with structures ranging from pure amorphous to highly crystalline. Despite previous expectations, in films deposited at low temperature, the presence of nanocrystals embedded in the amorphous phase does not promote crystallization. In fact, the crystallization temperature is much higher than expected from a simple solid state epitaxy mechanism, which indicates low coupling between the amorphous and crystalline phases.     

差示扫描量热基线漂移补偿算法设计

差示扫描量热分析是测量材料热物性的重要方法,根据其测量原理,传感器上样品与参比端差式输出的基线漂移将严重降低测量精度和范围.在仪器实际制造过程中,由于加工工艺水平和材料纯度等因素的影响,基线漂移不可避免,因此必须对其进行补偿.我们利用FIR等波纹逼近的方法对基线信号进行低通滤波去除带外杂波,并基于热流传感器的数学模型提出了一种扣除热流传感器中样品端与参比端热阻和热容不平衡影响的基线漂移补偿算法.实验表明,该算法可将基线的漂移量由-99.03⁰.42μW降低到-1.320.42μW降低到-1.32¹.25μW,证明了算法的有效性.     

An evaluation of AA 7012 microstructure by differential scanning calorimetry

Results of a Differential Scanning Calorimetry (DSC) investigation on a AA 7012 AlZnMg(CuZr) alloy in four commercial tempers (namely T4, T6, T76 and T73), are reported here. The tempers have been characterized from a microstructural point of view by performing DSC scans at different scanning rates. Endothermic and exothermic effects detected during DSC tests have been interpreted in terms of precipitation and dissolution of metastable and/or stable products of decomposition of the α supersaturated solid solution, in the precipitation sequence: α_sss → G.P. zones → η′¹(MgZn₂)→ η(MgZn₂).Apparent activation energies have been calculated, for the thermally activated reactions, on the basis of the Ozawa method in non-isothermal conditions. DSC results are discussed with the aid of TEM analysis data.     

Fatigue crack-propagation in annealed poly(butylene terephthalate)

Samples with the same percentage crystallinity, supermolecular structure and lamellar thickness but different average molecular weight were prepared to distinguish the effect of tie chain density on fatigue crack propagation (FCP) behaviour. This alteration in molecular weight was accomplished by controlled chain degradation during thermal annealing. A significant decrease in FCP resistance was observed when samples were annealed at different temperatures for various amounts of time. In addition, an examination of the fracture surfaces of these specimens indicates a transition to a more brittle-type behaviour when annealed for longer periods of time at any specific annealing temperature. The decrease in FCP resistance is attributed to a decrease in the tie chain density.     

共聚物聚苯硫醚-聚苯硫醚酮的合成及表征

在聚苯硫醚(PPS)的合成体系中加入不同比例的第三单体4,4二氯二苯甲酮(DCBP)从而合成了共聚物PP/SK.主要通过加入不同量的DCBP来考察产品的熔点及分子量的变化.合成工艺条件:前期反应的最高温度为T1=190℃～230℃,反应时间为t1=3h～5h;后期的反应温度最高为T2=250℃～270℃,反应时间为t2=2h～4h.n(Na2S·9H2O):n(对二氯苯/4,4二氯二苯甲酮)=1.1mol:1mol,m(N甲基吡咯烷酮):n(Na2S·9H2O)=282g:0.1mol,m(催化剂):n(Na2S·9H2O) =2g:0.1mol.根据上述加料及反应条件合成了线性的高分子量的共聚物PPS/SK,其重均分子量接近55000g/mol,产品的平均收率达到91.32％.通过一步循环回收工艺就实现了溶剂和催化剂的循环.用红外、元素分析、X-RD及热分析对产品进行了表征.