Two series of terpoly(methoxy-cyanurate-thiocyanurate)s based on thiodiphenol and dithiodiphenyl sulfide and on dihydroxydiphenyl ether and dithiodiphenyl ether, were prepared in good yield and purity and fully characterized. Most of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and thermal stability (some examples suffer practically no mass loss when held isothermally at 190 degrees C and only display appreciable losses when held continuously at 225 degrees C). Char yields of 53%-61% are achieved in nitrogen depending on backbone structure. Some problems were encountered with solubility, particularly with copolymers, which limited molecular weight analysis, but values of M-n = 8000-13000 g mol(-1) were obtained for the polymers based on thiodiphenol and dithiodiphenyl sulfide, and M-n = 5000-13000 g mol(-1) for the polymers based on dihydroxydiphenyl ether and dithiodiphenyl ether. DSC reveals polymerization exotherms with maxima at 184-207 degrees C (H-p = 43-59 kJ mol(-1)), which are believed to be due to isomerization of the cyanurate to the isocyanurate (activation energies span 159-195 kJ mol(-1)). Molecular simulation shows that diphenylether and diphenylsulfide display very similar conformational energy surfaces and would therefore be expected to adopt similar conformations, but the diphenylsulfide offers less resistance to deformations that increase the proximity of the two phenyl rings and results in more resilient films. (c) 2013 Society of Chemical Industry

A series of copoly(methoxy-thiocyanurate)s is prepared in good yield and purity, and fully characterised. Many of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and thermal stability (some examples suffer practically no mass loss when held isothermally at 190 degrees C and only display appreciable losses when held continuously at 225 degrees C). Char yields of 61-64% are achieved in nitrogen depending on backbone structure. Some problems were encountered with solubility, particularly with copolymers, which limited molecular weights analysis, but values of M-n = 7000-10,000 g mol(-1) were obtained for the polycyanurate and polythiocyanurate homopolymers. DSC reveals polymerisation exotherms with maxima at 197-207 degrees C (Delta H-p = 39-48 kJ/mol), which are believed to be due to isomerisation of the (activation energies span 172-205 kJ/mol), since X-ray powder diffraction measurements reveal no evidence of crystalline structure in the resulting product. (C) 2013 Published by Elsevier Ltd.

Three series of halogenated and non-halogenated polycyanurates are prepared in good yield and purity, and fully characterised. Many of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and high thermal stability (some examples suffer no mass loss when held isothermally at 190 °C and only display appreciable losses when held continuously at 300 °C). Char yields of 35–65% are achieved in nitrogen depending on backbone structure. Some problems were encountered with solubility, particularly with heavily halogenated dichlorotriazines, which limited molecular weights ( M n = 2000–4000 g mol −1 depending on backbone structure) although when the phase volume ratio was altered to 0.25 higher molecular weights ( M n = 10,000–30,000 g mol −1 ) were possible. Best solubility was achieved by using aromatic diols with at least two equivalent phenylene units per dichlorotriazine unit. DSC reveals polymerisation exotherms with maxima at 190–260 °C (Δ H p = 35–57 kJ/mol) followed by embrittlement and shrinkage (when heated to 300 °C). These phenomena may be due to the formation of poorly formed crystallites (activation energies span 155–380 kJ/mol) combined with thermal isomerisation.

ABSTRACTThe characterization by DMA and compressive stress‐strain behavior of an epoxy resin cured with a number of liquid amines is studied in this work along with predictions of the associated properties using Group Interaction Modeling (GIM). A number of different methods are used to assign two of the input parameters for GIM, and the effect on the predictions is investigated. Excellent predictions are made for the glass transition temperature, along with good predictions for the beta transition temperature and modulus for the majority of resins tested. Predictions for the compressive yield stress and strain are less accurate, due to a number of factors, but still show reasonable correlation with the experimental data. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3130–3141, 2013

Two simple simulation methods, which will be useful for the prediction of the infrared (IR) spectral features of polymers, are reported. This paper focusses on simple aromatic models of the main aromatic backbones of structural polymeric resins. These methods were normal coordinate analysis (NCA) using the PM3 Hamiltonian implemented under MOPAC6 and a dipole autocorrelation function (DACF) calculated using coordinates and velocities from a series of molecular dynamics runs performed using the universal force-field (UFF) as implemented in the Cerius2 modelling package. The semi-empirical NCA approach yielded useful information about the fundamental modes of vibration of the molecules but, as expected, could not be used to predict combination modes for anything but the simplest of molecules. The DACF approach showed potential for the prediction of combination bands but thorough evaluation of the method was found to be extremely difficult, owing to problems with band assignment for all but the simplest of molecules. An estimate of the accuracy of prediction for the different types of vibrational mode is included for each method.

The advent of open systems standards, while beneficial, has not eliminated the diffi-culty of maintaining transporting large scale software systems across many varying platforms. this paper we discuss the need criteria for a effective porting strategy, one that allows the rapid inexpensive retargeting of large scale software systems to mâny widely varying platforms while not compromising the integrity of that software on any pieviously supported platform. Getting Tigger down, said Eeyore, and not hurting anybody, Keep those two ideas in your head, Piglet, you'll be all right.,' A. A. Milne, The World of Pooh, 1957, pp2L6, McCeltand & Stewart Ltd. A key component of any porting strategy is the methodology used to determine, represent, use, validate specifications of the target system's characteristics site or system dependent build run time controls. The standards efforts (e.g., pOSIX, ANSI C) are attempting to eliminate the large number of discrepancies that exist among systems today. However, the problem will always exist, for ieasons that are discussed. Hence, the main objective of this paper is to present justify the methodology that we use. _ Ihis methodology is in production use on several commercial products in Sietec. Its benefits include relieving the programmer from the burden of needing detailed knowledge of all the idiosyncrasies of the various target environments. It is suffi-ciently powerful tnat it accommodates many flavours of BSD, System V, DOS.

Pink ring is a ubiquitous problem arising during the manufacture of multilayer PCBs, being the manifestation of local delamination at the inner‐layer oxide interfaces around drilled holes and subsequent dissolution of the oxide during plating processes. Except in extreme cases, there is no evidence that the occurrence of pink ring identifies any in‐service reliability problem, but it is nevertheless a clear process indicator and is strictly monitored in statistical process control. The UK Printed Circuit Industry has carried out a collaborative research programme aimed at providing an understanding and a quantitative analysis of the pink ring condition. The research has advanced on two fronts: (i) an investigation into the micro‐mechanisms of the delamination and stress relief around drilled holes and subsequent rôles of the desmear and plating chemicals, and (ii) a statistical analysis of boards manufactured in a variety of ways, analysing the quantitative measurements of pink ring in terms of, for example, panel source, drill supplier, drill quality, drilling backing material, drilling chip rate, stack position, and panel entry/exit side.

There is a reliability concern in the larger plastic surface mounting packages which can exhibit cracks from internal stresses during soldering. A lot of ad hoc information has been given to users of such packages about the origins of the problem and its alleviation. The phenomenon is the result of a combination of moisture absorbed in the plastic and the thermal stresses caused by the different expansions of the metal leadframe and the plastic. The work reported here gives quantitative data regarding the amount of moisture absorption critical to cracking, the range of baking procedures available to reduce this moisture below the critical level, and the acceptable floor life after baking for a wide range of storage temperatures and humidities.