bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal degradation of polyepichlorhydrin elastomers
Authors: Day John , Wright Walter W. 
Published: March 2007

AbstractThe thermal degradation of polyepichlorhydrin and of the copolymer of epichlorhydrin with ethylene oxide, both in the uncompounded and compounded form, has been studied in air and inert atmosphere by thermogravimetry. A detailed examination has also been made of the evolution of hydrogen chloride from the homopolymer as a function of temperature and compounding formulation, specific attention being given to the efficiency of the acid acceptor. It is concluded that with suitable formulationohydrogen chloride evolution should not be a problem at temperatures at least up to 175°C.
On the effect of a secondary process on the course of polymer crystallisation. Part 3
Authors: Hay James N. 
Published: March 2007

AbstractA crystallisation rate equation which allows for a secondary process involving an increase in crystallinity with logarithmic time has been derived. The model involves volume relaxation of the amorphous material constrained between crystalline regions and considered to relax as a glass. In general the equation predicts values of the Avrami exponent which are fractional, but in practice the equation cannot account for the range of values observed experimentally with polyethylene.
The contribution of neutron scattering to polymer science
Authors: Allen Geoffrey , Maconnachie Ann 
Published: March 2007

AbstractThe contribution of neutron scattering to polymer science is reviewed. A summary is given of the theory of neutron scattering followed by a review of the literature. Particular emphasis is placed on the use of small angle neutron scattering to observe the conformation of polymer chains in bulk polymers and concentrated polymer solutions and on quasi elastic neutron scattering to measure the dynamics of polymer chains.
The thermodynamic properties of liquids, including solutions. XIV. Solutions of normal alkanes: Models for oligomer solutions
Authors: Huggins Maurice L. 
Published: March 2007

AbstractFrom published HE data for 10 n‐alkane solutions in benzene at 25°C, the three parameters of the author's solution theory have been calculated. The values obtained agree quite well with εΔ = 3068 J/mole, K = 1, and rσ = 0.2 + 0.2 nc = 0.1 nH. The problems involved in the extension of these results to higher oligomers of polymethylene and to other solutions of chain molecules are briefly discussed.
A study on preferential solvation on styrene‐methyl methacrylate copolymers of varying architecture and composition by conventional and density gradient sedimentation equilibrium methods
Authors: Nakazawa Atsushi , Donkai Nobuo , Kotaka Tadao , Inagaki Hiroshi 
Published: March 2007

AbstractPreferential solvation in quasiternary systems composed of p‐xylene (pXY), 1,2‐dibromo‐1, 1‐difluoroethane (DBFE) and styrene (ST)‐methyl methacrylate (MMA) copolymers of varying architecture and composition was studied by two ultracentrifugation methods: sedimentation equilibrium in a density gradient and conventional sedimentation equilibrium. The preferential solvation parameters were estimated for the systems containing alternating, statistical and block copolymers as well as polymethyl methacrylate (PMMA) and polystyrene (PST). Virtually no solvation was observed by PST, while significant solvation of DBFE to MMA units took place. For alternating and statistical copolymers the solvation parameter is approximately the composition average of those of PST and PMMA, although a slight but distinct difference between those of the alternating and statistical copolymers was observed. However, in block copolymers of either PST‐PMMA or PMMA‐PST‐PMMA type of high PST content, it appears that the solvation of DBFE to PMMA‐blocks is suppressed by the presence of PST‐blocks.
Differential Scanning Calorimetry of Stressed Polymers
Authors: Shanks Robert A. , Smith Christine N. 
Published: April 2007

AbstractStresses which have been frozen into a polymer by cooling to below its glass transition temperature (Tg) are relieved when the polymer is reheated above its Tg. Polymers which have been elongated will contract above Tg. This sudden contraction just above Tg is detected as a sharp drop in the differential scanning calorimetric curve. This is the reverse of the well known superheating endotherm accompanying the expansion of annealed polymers. The decrease in the differential scanning calorimetric curve immediately after the Tg inflection can be quantitatively related to the residual strain in poly(vinyl chloride) and polycarbonate.
Thermal Ageing of Filled Polymers
Authors: Shanks Robert A. 
Published: April 2007

AbstractThe rate of thermal ageing has been found to decrease when a polymer is adsorbed onto a filler. The retardation of this glassy state relaxation has been found to be dependent on the type and amount of filler present. Comparison with values for the glass transition temperature and melt rheology parameters shows that the same factors are determining each of these properties. Each of these properties is determined by the mobility of the polymer molecules and this is restricted by adsorption onto a filler.
Multiple Exothermic Oxidation Behaviour of Polyethylene
Authors: Lee Yew‐Wing 
Published: April 2007

AbstractThe change of shape patterns of the oxidation peak on differential thermal analysis curves of a series of formulations of polyethylene has been investigated. The unstabilised sample exhibits two oxidation peaks. When a chain‐terminating antioxidant and dilaurylthiodipropionate were added to polyethylene, it was found that as the concentration of dilaurylthiodipropionate increases, the second oxidation peak reduces in size. In many instances when the amount of dilaurylthiodipropionate reaches 0.3% (by weight), the second oxidation peak disappears. The influences of processing method and outdoor exposure on the peak shape have also been examined. The effectiveness and consumption of antioxidants during weathering is clearly shown by the shape change of the oxidation peak on the differential thermal analysis curves.
Approaches to Terminal Diacetylenes, Precursors to New Substituted Polyacetylenes
Authors: Gibson Harry W. , Weagley Ronald J. 
Published: April 2007

AbstractA number of synthetic routes to substituted 1,6‐heptadiynes, specifically 3,3,5,5‐tetramethyl‐1,6‐heptadiyne (5), cis‐1,3‐dimethyl‐1,3‐diethynylcyclopentane (3, R=CH3) and cis‐1,3‐diethynylcyclopentane (3, R=H), have been examined. These diacetylenes are precursors to new substituted polyacetylenes via cyclopolymerisation. Two major synthetic difficulties were encountered: (1) low reactivity of neopentyl systems to nucleophilic displacement in the cases of 3, R=CH3 and 5, and, conversely, (2) lability of isoalkyl type structures such as the intermediates for 3, R=H toward elimination during nucleophilic displacement reactions. These fundamental problems were compounded by the fact that all the intermediates are difunctional, giving rise to the statistical problem of mixed functionalities. While none of the desired diacetylenes was prepared in a pure state, a number of new intermediate compounds were synthesised. Furthermore, an impure sample of 3, R=H did yield a polymer film in preliminary experiments.
1H Nuclear Magnetic Resonance Study of Melt Polycondensation of 4,4′‐Sulphonyldiphenol with Methyl‐ and Chloromethylphosphonic Dichloride
Authors: Natansohn Almeria 
Published: April 2007

AbstractMelt polycondensation of 4,4′‐sulphonyldiphenol with methylphosphonic dichloride and chloromethylphosphonic dichloride, respectively, was studied by taking samples from time to time and recording their 1H n.m.r. spectra. Analysis of the spectra provided identification of the intermediate structures present during the reaction. Complete spectral assignments were made, and the effect of the substitution on the chemical shifts was measured. No kinetic calculations were made, owing to the inhomogeneity of the reaction mixtures.
The Technology of Phenol‐Formaldehyde Moulding Powders 1 ‐ Characterisation of Novolak Resins and Derived Moulding Powders
Authors: Birley Arthur W. , Blinkhorn Arthur 
Published: April 2007

AbstractThis research programme has been concerned with the technology of phenol‐formaldehyde resins and of moulding powders based on them. This paper reports the characterisation of the prepolymer (Novolak) and concentrates on the results obtained by gel permeation chromatography with an infrared detector. A variety of frequencies have been employed, corresponding to different components in the resin, and the best separation was obtained by monitoring the phenolic hydroxyl at 3400 cm−1. It has been concluded that both commercial Novolak and prepolymer extracted from moulding powder contain a substantial fraction of high molecular weight material.
A Comparative Study of the Thermal Stability and Mechanism of Degradation of Poly(arylene sulphones)
Authors: Crossland B. , Knight G. J. , Wright W. W. 
Published: April 2007

AbstractThree poly(arylene sulphones) have been studied by thermogravimetry to ascertain their relative thermal stabilities in both inert and oxidising atmospheres. Experiments have been carried out at a rate of temperature rise of 2°C min−1 and isothermally at a number of temperatures. The level of stability found compared favourably with that of other heat‐resistant materials, for example the addition type polyimides. The polymers have also been examined by pyrolysis gas chromatography mass spectrometry using two different procedures. In the first, fresh samples were pyrolysed at a number of increasing temperatures, whereas in the second, the sample was subjected to successive pyrolyses at the same temperature intervals.
Synthesis of Poly(4,5‐bis‐hydroxy‐1,3‐cyclopentadienylene vinylene) from Poly(6,8‐(1,5‐dichloro‐2,4‐dioxa‐3‐keto)‐bicyclo[3.3.0]octylene vinylene). Generation of a Conjugated Polymer by Hydrolysis of a Precursor Polymer
Authors: James Feast W. , Harper Kevin 
Published: April 2007

AbstractHydrolysis of poly(6,8‐(1,5‐dichloro‐2,4‐dioxa‐3‐keto)bicyclo[3.3.0]octylene vinylene) results in the formation of poly(4,5‐bis‐hydroxy‐1,3‐cyclopentadienylene vinylene), a new conjugated polymer. This new system can be generated as a surface layer on its precursor polymer. The conversion process has been studied with the aid of infrared and optical spectroscopy, elemental analysis, microscopy and conductivity measurements.
Molten State Transition in Thermoplastic Rubber
Authors: Canevarolo Sebastião V. , Birley Arthur W. , Hemsley Derek A. 
Published: April 2007

AbstractThe flow characteristics of styrene‐butadiene‐styrene thermoplastic rubbers have been studied and the results compared with earlier static measurements. Computer best‐fitting shift factors and inverse Melt Flow Index were plotted according to two mathematical models, Arrhenius and Vogel. Fulcher, Tamman and Hesse (VFTH). One transition was observed in both models, with appreciable reduction in the apparent activation energy of flow above this transition. This melt transition was associated with the temperature above which the PS chains can be removed from the PS rich phase by the rubbery chains. This allows rearrangement of the domain structure in a static condition or facilitates flow. Birefringence measurements support the model proposed.
‘Ordered’ Structure of Polyallylamine Hydrochloride in Dilute Solutions as Studied by Small Angle X‐ray Scattering
Authors: Yoshikawa Yukihiro , Matsuoka Hideki , Ise Norio 
Published: April 2007

AbstractAqueous solutions of polyallylamine hydrochloride were examined by small angle x‐ray scattering. When the polymer concentration of coexisting simple salt was low, a single, broad peak was observed. The peak was interpreted as indicating the presence of an ordered arrangement of macroions in the solutions. The intermacroion spacing was calculated by the Bragg equation and found to be much smaller than the average intermacroion spacing calculable from the polymer concentration, suggesting that there exist ordered regions and at the same time disordered regions in the solutions. The Bragg spacing decreased with increasing polymer concentration and increased with increasing salt concentration. Mixing of two samples of different molecular weights gave a new scattering peak in between the original peaks of the mother samples, which supports the intermolecular nature of the ordering. The peak height was lowered with increasing temperature. The scattering peak was found to stay unaffected for 21 days.
Behaviour of Composites Used in the Confinement of Nuclear Wastes 2 ‐ Water Absorption in Particle‐filled Epoxide Networks
Authors: Nicaise E. , Gandini A. , Cheradame H. 
Published: April 2007

AbstractThe diffusion of water into epoxide composites containing sand or glass beads has been studied as a function of temperature, type of filler and its surface treatment. This investigation falls within a broader context whose aim is to assess the possibility of embedding nuclear wastes into polymer matrices. The quality of polymer‐filler adhesion was checked by scanning electron microscopy. The best filler was found to be siliceous sand in particles of about 30 μm diameter, which could be added to epoxide networks in large proportions and provide a better material than the polymer alone.
Anionic Graft Polymerisation of Styrene from Polyisoprene. Dependence of Grafting Efficiency on Polyisoprene Structure
Authors: Al‐Jarrah Mustafa M. F. , Al‐Kafaji Jawad K. H. , Apikian Rita L. 
Published: April 2007

AbstractStyrene was grafted from polyisoprene forming poly(isoprene‐g‐styrene) graft polymers. N,N,N',N'‐Tetramethylene diamine and s‐butyllithium were used to create active centres on the polyisoprene backbone in cyclohexane under anionic living polymerisation conditions. The stereoregularity of polyisoprene is shown to influence the grafting efficiency. Addition of small amounts of tetrahydrofuran increased grafting efficiency and decreased polydispersity of the graft polymers obtained. Polystyrene branches are shown to be syndiotactic rich.
The Computer Simulation of the Continuous Vulcanisation of High Pressure Hose
Authors: Evans Colin W. , Manley Thomas R. 
Published: April 2007

AbstractThe use of molten salt in the pressurised liquid continuous vulcanisation system enables most of the disadvantages of steam continuous vulcanisation to be overcome. To reduce the time needed to introduce this novel process into production a computer was used to simulate the pressurised liquid continuous vulcanisation system. Computer simulation can greatly reduce the costs of introducing new processes.
The Cure of Carboxy‐terminated Diene Polymers and the Role of a Polymer‐supported Catalyst
Authors: Willoughby Bryan G. 
Published: April 2007

AbstractBoth infrared spectroscopy and wet chemical techniques reveal that the terminal acid groups of carboxyl‐terminated polybutadiene behave in the same manner as in representative low molecular weight dilute solution systems. Contrary to previous expectations the chromium(III)‐catalysed epoxy chain extension shows third‐order character, and the slow progress of reaction at high conversions can be rationalised on simple kinetic grounds and without recourse to considerations of limited functional group accessibility. The parallels between bulk polymer and classical solution reactions anticipate the effectiveness of a system in which the catalyst is also a polymer: the synthesis and evaluation of two such catalysts are described. Whilst gel times are no slower for the polymer‐catalysed cures, product properties may be actually improved, thus, the unreinforced product of a liquid nitrile rubber cure may achieve a tensile strength of 4.5 MPa when the initial catalyst is chromium(III) supported on the same polymer, an improvement which can be rationalised in terms of classical concepts of polymer reactivity and step growth processes.
Investigation and Development of Epoxy Foams
Authors: Hajimichael Michael , Lewis Annette , Scholey Dave , Simmonds Clive 
Published: April 2007

AbstractThe development of low toxicity rigid epoxy foams as an alternative to polyurethane foams for electronics encapsulation is described. The basic foam components ‐ epoxy resin, hardener, accelerator, blowing agent and surfactant ‐ are blended to form a two part system which is mixed and foamed when required. Each foam component is selected for its contribution to the foaming reaction and the final foam properties. The balance of component miscibility, viscosity, reaction rate and exotherm determine foam quality. Foam properties are affected by (1) density (2) cell structure and (3) the molecular structure of the reactants. Initial foam development utilised epoxy/amine chemistry and produced two foams, Feldex F3 and F4. Subsequently, use of a more reactive polymercaptan hardener improved foam strength and process times, resulting in Feldex F5 and F6 which have been used successfully to prepare quality mouldings and encapsulated electronics. Recently, development has been extended to new areas of application, e.g. high temperature foams. The mechanical, electrical, thermal and chemical properties of the best epoxy foams have been evaluated; selected results are reported. The epoxy foams developed offer low density, high strength, low dielectric constant and loss tangent, high volume resistivity, good thermal insulation, low corrosivity and low toxicity. In addition, epoxy foams soften in acetone, an advantage over their polyurethane counterparts since encapsulated electronics may be retrieved without employing corrosive solvents. (Feldex is a registered trade mark of THORN EMI Electronics.)
Structure and Properties Relationships of Epoxy Resins Part 1: Crosslink Density of Cured Resin: (II) Model Networks Properties
Authors: Lau Chung H. , Hodd Kenneth A. , Wright William W. 
Published: April 2007

AbstractCarefully designed resin precursors of high purity, viz. N,N‐bis‐(2,3‐epoxypropyl)‐N',N‐dimethyl‐4,4′‐diaminodiphenylenemethane (G2A) and N,N‐bis‐(2,3‐epoxypropyl)‐N,N‐dimethyl‐4,4′‐diamino‐diphenylenemethane (G2S) were used in combination with N,N,N',N‐tetrakis‐(2,3‐epoxypropyl)‐4,4′‐diaminodiphenylene methane, TGDDM, and cured with stoichiometric amounts of 4,4′‐diamino‐diphenylene methane (DDM) to produce networks with a range of controlled crosslink density. The tensile moduli E of the networks in the rubbery state, at Tg+30°C, Tg+45°C and Tg+60°C, were measured using a thermal mechanical analyser. Using the statistical theory of rubber elasticity and the observed values of E, the number average molecular weights between crosslink points Mc for the cured resins were deduced. The experimental Mc values were then compared with those derived by calculations based on a probabilistic model of the network proposed by Chu and Seferis.1 The experimental Mc values were 2.5 to 5.5 times larger than the calculated ones. The differences were attributable to a consumption of only 40% of the available secondary amino hydrogen via epoxy‐amine reaction. A direct relationship was established between the glass transition temperature and the crosslink density 1/Mc for the resins, and the dynamic mechanical properties were studied. The thermal stability of cured resins studied by thermo‐gravimetric analysis indicated an enhancement of stability as 1/Mc was reduced. The amount of water absorbed by cured resin was directly proportional to 1/Mc.
Modelling of the Hydrolysis of Benzylpenicillin to 6‐Aminopenicillanic Acid and Phenyl Acetic Acid by an Immobilised Penicillin Amidase in a Small Pilot Plant Batch Recirculated Reactor
Authors: Cardoso Joaquim Pereira , Da Costa Manuel Bento Correia 
Published: April 2007

AbstractThis paper deals with the modelling of the hydrolysis of benzylpenicillin to 6‐aminopenicillanic acid (6‐APA) and phenyl acetic acid (PAA) in a small pilot plant batch recirculated reactor by an immobilised penicillin amidase preparation. By using the following linearised form for an integrated Michaelis‐Menten equation Et/V0X=α+β| In (1‐X)/X| where α and β are reaction kinetic parameters, good correlations are obtained of α and β with linear velocity across the reactor, substrate concentration and temperature of operation. A process to determine α and β from initial velocity measurements is outlined. The applicability of the above equation to published data is also analysed.
Crosslink Enhancement in Polypropylene Film by Gamma Irradiation in the Presence of Acetylene
Authors: Ken Busfield W. , Appleby Rodney W. 
Published: April 2007

AbstractThe effects of crosslink enhancement by the presence of acetylene during gamma irradiation, on the physical and mechanical properties of polypropylene film are reported. Gel contents show that crosslink enhancement is considerably greater if the sample is highly annealed (PPA) than if it is quenched (PPQ). For PPA, thermal analysis suggests only minor damage to the crystalline lamellae, but significant stabilisation of lamellae by crosslink formation in the lamellar surface regions. This is supported by an increased resistance to the yielding process observed in tensile stress/strain and creep tests. The effects in PPQ is less.
Size‐exclusion Chromatography of Urea‐Formaldehyde Resins
Authors: Hlaing Tin , Gilbert Adrian , Booth Colin 
Published: April 2007

AbstractSamples of urea‐formaldehyde resin have been investigated by means of size‐exclusion chromatography systems: (A) Zorbax PSM packing with either pure N,N‐dimethylacetamide (DMA) eluant or DMA+0.1 mol dm−3 LiNO3 eluant; (B) Styragel packing with DMA eluant. In addition to separation by size‐exclusion, adsorption/partition and hydrodynamic effects were observed. The influence of reaction time and conditions on the production of large soluble aggregates was investigated briefly.
Polymeric Routes to Silicon Carbide
Authors: Schilling Curtis L. 
Published: April 2007

AbstractSeveral classes of organosilicon polymers are effective precursors for silicon carbide ceramic compositions. These include polydimethylsilane (via a two‐step process), ‘polysilastyrene’, polycarbosilazanes or polysilazanes, and certain siloxanes, plus the branched polycarbosilanes, branched polysilahydrocarbons, and vinylic polysilanes developed at Union Carbide. The latter three classes are prepared by active metal dechlorinations of appropriate chlorosilane blends, leading to recognition of branching at backbone silicon atoms (either as prepared or during processing) as a prerequisite for obtaining useful ceramic yields. Fundamental reactivity differences between the active metals (potassium and sodium) allow the preparation of sodium‐derived vinylic polysilanes. The latter offer certain economic and performance advantages as ceramic precursors.
The Thermal Degradation of Some Polymers Based Upon p‐Hydroxybenzoic Acid
Authors: Crossland The Late Barbara , Knight Graham J. , Wright William W. 
Published: April 2007

AbstractThree polymers based upon p‐hydroxybenzoic acid have been studied by thermogravimetry to ascertain their relative thermal stabilities in both inert and oxidising atmospheres. Experiments have been carried out at a rate of temperature rise of 2°C min−1 and isothermally at a number of temperatures. The polymers have good thermal stability. They have also been examined by pyrolysis gas chromatography mass spectrometry using two different procedures. In the first, fresh samples were pyrolysed at a number of increasing temperatures, whereas in the second, the same sample was subjected to successive pyrolyses at the same temperature intervals. The results are compared with those of other authors derived using different techniques.