Abstract: The microstructure and shape-memory properties of norbornyl-POSS hybrid copolymers having either cyclohexyl corner groups (CyPOSS) or cyclopentyl corner groups (CpPOSS) were investigated by transmission electron microscopy and thermomechanical analysis. Here, POSS refers to the polyhedral oligomeric silsesquioxane macromer. Samples containing 50wt% of POSS macromer have been mechanically drawn at temperatures above their glass transition temperatures, followed by rapid quenching in LN2 . Shape-memory properties of such drawn samples were explored by measuring recovered strain while heating above the T g using thermomechanical analysis. Incorporation of POSS comonomers within PN is found to slightly reduce the percentage recovery, while improving thermal stability significantly. Interestingly, the types of corner groups in the POSS macromer affect the shape-memory behaviour, with the CyPOSS copolymer showing lower percentage recovery than the CpPOSS copolymer due to enhanced aggregation of CyPOSS macromers. # 2000 Society of Chemical Industry

Abstract: Nanocomposites of polystyrene and several organophilic clays have been prepared by a bulk polymerization technique. The resulting polymers have an intercalated structure and show enhanced thermal stability, as measured by thermogravimetric analysis and cone calorimetry, relative to virgin polystyrene, even when as little as 0.1% of clay has been added.

Abstract: This paper reports the measured values of dielectric permittivity e′ and dielectric loss e″ of ethylene glycol, diethylene glycol and poly(ethylene glycol)s of average molecular weight 200, 300, 400 and 600 g mol−1 in the pure liquid state. The measurements have been carried out in the frequency range 200 MHz to 20 GHz at four different temperatures of 25, 35, 45 and 55 °C. The complex plane plots (e″ versus e′) of these molecules are Cole–Cole arcs. The static dielectric constant e0, high-frequency limiting dielectric constant e∞, average relaxation time τ0 and distribution parameter α have been determined from these plots. The value of the Kirkwood correlation factor g and the dielectric rate free energy of activation ΔF have also been evaluated. The dependence of relaxation time on molecular size and viscosity has been discussed. A comparison has also been made with the dielectric behaviour of these molecules in dilute solutions of non-polar solvents, which were carried out earlier in this laboratory. The influences of intermolecular hydrogen bonding and molecular chain coiling on the dielectric relaxation of these molecules have been recognized. © 2000 Society of Chemical Industry

Abstract: The overview of the literature for a 25-year period on the combustion and fire-retardant performance of major commercial aliphatic nylons is presented. It is shown that aliphatic nylons are relatively easily ignitable materials which support combustion and are therefore required to be fire retarded for some applications. Nylons do not produce vision-obscuring smoke during combustion, and the toxicity of their combustion products is similar to or lower than that of many other man-made materials. Patent literature and technical publications on the fire retardancy of aliphatic nylons with halogenated products, phosphorus-containing compounds, nitrogen-rich compounds, sulfur-containing, boron-containing and silicon-containing products are discussed. Miscellaneous inorganic additives and char-forming organic products are also discussed. It is concluded that, in spite of significant attempts, no commercial solution of fire retardancy of aliphatic nylons without loss of mechanical properties is available.

Abstract: A review of recent developments in the applications and actions of intumescent fire-retardance is given. An attempt has been made to classify the main systems of importance such as melamine, ammonium polyphosphate, melamine phosphate, pentaerythritol phosphate, sodium silicate, vermiculite, expandable graphite and microbeads. They are defined in terms of the Berthelot number which is the product of heat of vaporization or decomposition and volume of gases evolved. In principle, only two kinds of gases are produced from this group, namely water vapour and ammonia (from melamine). The heats of decomposition are readily calculated from heats of formation. An important aspect which is not included in the Berthelot number is the ignition residue in the shape of glassy foam or a cellular enamel.

Abstract: This work deals in the first part, with the fire retardancy of polypropylene (PP)/ thermoplastic polyurethane (TPU)/ammonium polyphosphate (APP) intumescent blends, using TPU with different chemical compositions. The influence of the chemical nature of the polyol used in the synthesis of the TPU on the fire resistance (FR) of materials is discussed. Moreover, mechanical properties (elongation/stress relationship) of the polymeric materials are studied and related to the morphologies of the blends. Improved FR materials with very different mechanical properties are formulated. The second part deals with the evaluation of the dynamic properties of a particular FR PP/TPU/APP formulation. The experiments have been carried out using a thermal scanning rheometer as a fire reactor. First, the expansion of intumescent material under normal force is studied. Then, the study shows that the different steps of intumescent formation and degradation can be well evaluated from the measurement of viscosity. The loss of the protective character, ie reduction of heat and mass transfers related to the superficial foam morphology, may be explained by change of the viscosity of the charred material under stress. The influence of an external stress on the surface morphology of the char is then proposed.

Abstract: This paper is concerned with the processes of thermal degradation of nylon 6 and nylon 6,6, which lead to crosslinking and the production of involatile char. The techniques used in this study include thermogravimetric analysis (TG), differential scanning calorimetry (DSC), hot-stage Fourier transform infrared spectroscopy (hot-stage FTIR) and solution viscosity. TG results showed that nylon 6 and nylon 6,6 produce involatile char during thermal degradation. The formation of char lead to a deviation from first order kinetics of thermal degradation, and the amount of char yielded decreased with increasing temperature. Thermal degradation lead to a decrease in the amount of crystallinity attainable on cooling from the melt, which was considered to be due to crosslinking, and was accompanied by an increase in molecular weight and formation of colour. Hot-stage FTIR results showed that thermal degradation lead to the formation of an aromatic-conjugated structure, which may contain keteneimine groups.

Abstract: Polypropylene (PP)/montmorillonite (MMT) nanocomposites have been prepared by melt intercalation using organomontmorillonite and conventional twin screw extrusion. The dispersibility of silicate layers of the montmorillonite in the composites was investigated by using X-ray diffractometer and transmission electron microscopy (TEM). The silicate layers of montmorillonite are dispersed at the nanometer level in the PP matrix, as revealed by X-ray and TEM results. The tensile strength of PP/MMT is not much improved compared with pure PP or conventional filled composites. However, the impact strength is greatly improved at lower content of MMT. © 2000 Society of Chemical Industry

Abstract: By employing Fourier transform infrared spectroscopy (FTIR) and curve–fitting techniques, the degree of crystallinity of poly(e-caprolactone) (PCL) aged at room temperature for 1 month was estimated to be 49 ± 2 %. The degree of crystallinity determined by FTIR in this work is comparable with those found by other conventional techniques. It is suggested that the FTIR procedure established here for the crystallinity determination of PCL should also be suitable for the quantitative analysis of solid-state morphology of polymers containing carbonyl or other functional groups. © 2000 Society of Chemical Industry

Abstract: The adhesive and mechanical properties of epoxy resins modified with carboxyl terminated poly(2-ethylhexyl acrylate) (CTPEHA) liquid rubber have been investigated as a function of the concentration of liquid rubber. CTPEHA was synthesized by the bulk polymerization technique. CTPEHA oligomer was prereacted with the epoxy and the modified epoxy networks were made by curing with an ambient temperature curing agent. The modified epoxy networks were evaluated with respect to their adhesive and mechanical properties. The optimum properties were obtained at about 10–15 phr (phr stands for parts per hundred parts of epoxy resin) concentration of modifier. Fracture surface analysis by optical microscopy (OM) indicates the presence of two phase microstructures. © 2000 Society of Chemical Industry

Abstract: Progress in the structure control of polymethacrylates and polyacrylates through stereospecific living polymerization are described. Three types of stereospecific living polymerizations have been developed for methacrylate polymerization: isotactic with t-C4H9MgBr, syndiotactic with ­t-C4H9Li/R3Al, and heterotactic with t-C4H9Li/bis(2,6-di-t-butylphenoxy)methylaluminium [MeAl(ODBP)2]. The last initiator system has been proved effective for monomer-selective living copolymerization of methacrylates. The living nature of these polymerizations allows extensive use for the syntheses of stereoregular block polymers and copolymers, and end-functionalized polymers such as macromonomers. Through stereospecific polymerizations and copolymerizations of macromonomers, comb polymers and graft copolymers with defined stereoregularities in the main chain and side chains could be obtained. Some properties of these stereoregular polymers are also described, including stereocomplex formation and solution viscosity. Stereospecific polymerizations of crotonates leading to diisotactic, diheterotactic and disyndiotactic polymers are also discussed. Supercritical fluid chromatography (SFC) has been proven to be useful for isolating uniform polymers from stereoregular poly(methyl methacrylate)s (PMMAs) with narrow molecular weight distribution. Uniform end-functionalized polymers have been used to construct more elaborate uniform polymer architectures such as stereoblock, star, and comb polymers, and copolymers. The uniform polymers have been proven quite useful for the studies of the relationship between structures and properties such as glass transition temperature, melting temperature and solution viscosity. Particularly interesting is the use of isotactic and syndiotactic uniform PMMAs for the understanding of stereocomplex formation in certain solvents such as acetone. Furthermore, a uniform stereoblock PMMA was found to undergo intramolecular complexation in addition to intermolecular complexation in acetone. Uniform star and comb PMMAs were also prepared and found useful for discussing the effect of branching on the solution viscosity. © 2000 Society of Chemical Industry

Abstract: Oil palm empty fruit bunch–polypropylene (EFB-PP) composites have been produced using a twin-screw extruder as the compounding equipment. Two levels of EFB were employed, 40 % and 60 % of the total weight of the sample. Three types of coupling agent, maleic anhydride-modified polypropylene (commercial name Epolene E-43), polymethylene(polyphenyl isocyanate) (PMPPIC) and 3-(trimethoxysilyl)-propylmethacrylate (TPM), were used. Overall, all coupling agents imparted considerable improvements in the flexural properties, E-43 showing the highest enhancement. However, only E-43 was observed to improve impact strength and tensile properties of the composites. All composites with coupling agents showed lower water absorption and thickness swelling. The absorption and swelling decreased as the loading of the coupling agents was increased. © 2000 Society of Chemical Industry

Abstract: Radiation-induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films was studied by a simultaneous irradiation technique. Grafting was carried out using g-radiation from a 60 Co source at dose rates of 1.32-15.0 kGy h ˇ1 at room temperature. The effects of type of diluent, dose rate, irradiation dose, and the initial monomer concentration in the grafting solution on the degree of grafting were investigated. The degree of grafting was found to be strongly dependent upon the grafting conditions. The dependence of the initial rate of grafting on the dose rate and the initial monomer concentration in the grafting solution was found to be in the order of 0.6 and 1.7, respectively. The chemical structure and the crystallinity of the grafted PTFE films were studied by means of Fourier- transform infrared, (FTIR), electron spectroscopy for chemical analysis (ESCA) and X-ray diffractometry (XRD). # 2000 Society of Chemical Industry

Abstract: Hexakis(phenylamino)cyclotriphosphazene, hexakis(phenoxy)cyclotriphosphazene, tris(o-phenylenediamino)cyclotriphosphazene, tris(phenylene-1,2-dioxy)cyclotriphosphazene and tris (phenylene-1-amino-2-oxy)cyclotriphosphazene have been prepared and characterized by IR and NMR spectroscopy. Phospham, a crosslinked phosphazene imide (PN 2 H) n , was prepared by heating hexaminotricyclophosphazene under vacuum. Phosphorus oxynitride (PON) m which is likely to be a crosslinked oxyphosphazene was prepared by intense heating of urea, melamine and phosphoric acid. These phosphorus-nitrogen containing compounds added to poly(butylene terephthalate) (PBT) at 10-20wt% provided increase of oxygen index (OI) from 22 to 29. In spite of relatively high OI only the V-2 rating was observed in the UL94 test because of the flaming drip phenomenon. Phosphorus oxynitride was found to be an efficient char promoter for PBT.

Abstract: Hydroxy phenyl-substituted cyclotriphosphazenes were synthesized by reacting hexachlorocyclotriphosphazene with sodium phenolate and monosodium bisphenolate. The derivatives, consisting of a mixture of multi-substituted and partly chain-extended cyclophosphazenes, with overall functionality close to the targeted values, were transformed into the cyanatophenyl derivative. Thermal curing of the latter gave phosphazene–triazine cyclomatrix network polymers with varying ratios of phosphazene and triazine rings in the matrix. Although they manifested diminished Tg, the cured polymers were more thermally stable and provided higher char residue in comparison to the polycyanurate derived from bisphenol-A dicyanate. The activation energies for thermal decomposition of the cyclomatrix networks increased with both phosphazene content and crosslink density, and showed a direct relationship with their thermal stability. The presence of phosphazene was conducive for enhancing the flame retardancy of the network. The flame retardancy improved with increase in crosslink density and char-yielding property of the polymer, which implied that the flame-retardant action was operative in the condensed phase. © 2000 Society of Chemical Industry

Abstract: Selected phosphorus-containing flame retardants, including some intumescents, have been formulated with selected resins and applied as back-coatings to both cotton and cotton-polyester (35:65) blended fabrics. While all formulations raise the limiting oxygen index, only those based on ammonium polyphosphate and a cyclic phosphonate enable samples to pass a small-scale version of the simulated match test, BS5852: 1979, Source 1. As expected, the back-coatings containing intumescents promoted higher levels of char formation, but these did not reflect in their performance to the match test where most incurred failures. Thermogravimetric analysis suggests that the more effective flame retardants as exemplified by ammonium polyphosphate, are those which liquefy by melting and/or decomposition well below 300 °C. It is proposed that this enables wetting by these products of the back face of the fabric and their diffusion to the front face where, as the temperature rises towards 300 °C, char formation occurs before ignition of surface fibres can take place.

Abstract: Spherical crosslinked beads using chitosan, glycine and glutaraldehyde were prepared for controlled release formulations. Structural investigation of the beads was made with IR analysis. Morphological study of the beads was carried out by scanning electron microscopy. The swelling behaviour of the beads was monitored as a function of time in solutions of different pH. The release experiments were performed using thiamine hydrochloride (Thi-HCl) as a model drug. These preliminary results suggest the possibility of modifying the formulations to obtain the desired controlled release of drug in an oral sustained delivery system. © 2000 Society of Chemical Industry

Abstract: This paper presents a review of the current state of the art of transport models for charring solid degradation. Both cellulosics and synthetics are examined. Advanced solid-phase models, taking into account multi-step primary and secondary reactions and transport phenomena, are available for the first class of materials. Extensive applications have enabled the effects of model and physical parameters to be investigated on pyrolysis regimes and characteristics. Further work is needed to improve quantitative predictions, especially in relation to wood and flame-retardant effects. Advanced models are also available for the thermal response of glass-filled (composite) polymers. However, the literature still lacks comprehensive formulation of the main chemical and physical processes for both charring plastics and intumescent systems.

Abstract: Scanning force microscopy (SFM) was used to probe the micromechanical properties of polyisoprene rubbers, polyurethanes, polystyrene and polyvinylchloride. Applicability of the SFM cantilevers for microprobing is presented as a convenient method for materials selection. The Hertzian model of elastic contacts was used to obtain Young's modulus at contact frequencies range 0.05-367 Hz. The absolute values of the elastic modulus were correlated with the known properties of bulk materials, with no frequency dependence detected for glassy polyvinylchloride and polystyrene in air. The time dependence of the Young's modulus of rubber and polyurethanes followed the Williams-Landel-Ferry relationship, with parameters known for bulk materials. For PVC in water, a significant reduction of the elastic modulus and strong time-dependency were recorded. This behaviour can be related to the lower local glass transition temperature because of a plastification effect of solvent molecules on the uppermost polymer layer. # 2000 Society of Chemical Industry

Abstract: Poly(D,L-lactide-co-glycolide) samples with different glycolide contents, ie 85:15, 75:25 and 50:50 mole ratios of lactide to glycolide, and poly(L-lactide) were obtained from a commercial source. Polymer films of 15 µm thickness were prepared by a solvent-casting method. Degradation studies were conducted at 37 °C in pH 7.4 phosphate buffered saline and in bovine serum albumin solution. The degradation behaviour of the films was followed by UV and FTIR spectrophotometry and viscometric and gravimetric measurements. Spectroscopic investigations showed that during the first month of degradation, both the chain length and the chain chemical structure changed, especially in the presence of bovine serum albumin. The short chains are attributed to the formation of new ester groups; however, the end-groups may be aldehyde- or ketone-like structures. While the intrinsic viscosities of all polymers decreased continuously after being exposed to the degradation media, insignificant mass loss occurred during the experimental investigation. © 2000 Society of Chemical Industry

Abstract: In this work, zinc borate is used as synergistic agent in EVA-Mg(OH) 2 flame-retardant (FR) formulations. High zinc borate content leads to a significant improvement of flame retardancy during cone calorimeter experiments. Blowing measurements reveal significant modification of the structure due to the presence of zinc borate. To estimate the resistance of this structure under strength, blowing measurements were carried out under two different pressures. Viscosity measurements helped to elucidate the foamine process. Finally, zinc borate can he understood to be a hinder (flux agent).

Abstract: The thermal and mechanical properties of corn (maize) (CZ) films plasticized with poly(ethylene glycol) (PEG) of two different molar masses (400 and 1000 g mol−1) were studied using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), tensile strength, moisture absorption isotherms and water vapour transmission rate measurements. The glass transition temperature (Tg) of plasticized films is determined primarily by the amount of moisture contained in the film. DMTA data show contraction of films with loss of absorbed water during heating/cooling cycles. The moisture absorption behaviour of films plasticized with PEG400 and PEG1000 is similar at low relative humidities but significantly different at higher relative humidities. Incorporation of up to about 30 wt% PEG substantially enhances the tensile strength and the resistance to water vapour transmission of the protein film, and PEG1000 is more effective than PEG400. © 2000 Society of Chemical Industry

Abstract: The comparative performance in a three point bending test of syntactic foam comprising epoxy resin and glass microballoons with and without the inclusion of glass fibre in the form of chopped strands is reported. Test samples having a span-to-depth ratio of 16:1 were used. The data show that the glass fibre reinforced foam system had a higher strength compared to the unreinforced system. Resorting to light macroscopic and scanning electron microscopic examinations on mechanically tested samples expanded the scope of the work for a structure–property correlation to emerge. © 2000 Society of Chemical Industry

Abstract: Free-radical melt-grafting of the dual-monomer systems glycidyl methacrylate–styrene (GMA-St) and hydroxyethyl methacrylate–styrene (HEMA-St) onto polypropylene (PP) has been studied using a single-screw extruder. For single monomer grafting systems, degradation of PP was unavoidable and deterioration of the mechanical properties of the grafted PP subsequently occurred because of β-scission of PP chains during the free-radical melt-grafting process. However, for the dual-monomer systems, it is shown that the addition of styrene as a comonomer can significantly enhance the GMA or HEMA grafting levels on PP and reduce the extent of β-scission of PP backbone. It has been found that the grafting degree of dual-monomer melt-grafted PP, such as PP-g-(GMA-co-St) or PP-g-(HEMA-co-St), is about quadruple that of single-monomer grafted PP for the same monomer and dicumyl peroxide concentrations. Moreover, the melt flow rate of the dual-monomer grafted PP is smaller than that of the unmodified PP. Hence, PP not only was endowed with higher polarity, but also kept its good mechanical properties. © 2000 Society of Chemical Industry

Abstract: The miscibility, morphology and tensile properties of three blend systems of poly(e-caprolactone) (PCL) with poly(vinyl chloride) (PVC) and with two chlorinated PVCs (CPVCs) with different chlorine contents (63 wt% and 67 wt% of Cl) have been studied Based on the shifts of single glass transition temperature, the Gordon–Taylor K parameter is calculated as a measurement of interaction strength between PCL and (C)PVCs Higher K values are found for blends of (C)PVCs with higher chlorine content, together with the interaction χ parameters estimated from the melting point depression results The morphology observed with polarized light microscopy shows that spherulites exist in blends rich in PCL (≥50 wt%) only Wide angle X-ray diffraction studies indicate that the crystal structure of PCL is independent of the Cl content of (C)PVCs The tensile properties of various blends exhibit a minimum as the PCL content increases The elongation at break increases with increasing PCL content © 2000 Society of Chemical Industry

Abstract: Conventional thermogravimetric analysis (TGA) and a controlled atmosphere horizontal tube furnace have been used to study thermal degradation, in air and nitrogen, of ethylene-vinyl acetate copolymer (EVA) and low-density polyethylene (LDPE). The addition of aluminium oxide trihydrate (ATH) as a fire retardant was investigated. At 400 °C and at 450 °C, in both air and nitrogen, LDPE showed greater thermal stability in conventional TGA than the EVA copolymer. However, in the tube furnace experiments, at both temperatures, EVA showed comparable thermal stability to LDPE in nitrogen, and superior thermal stability to LDPE in air. This is thought to be the result of the formation of a protective layer, which is more effective at 400°C than at 450°C. In combination with approximately 55% ATH, the rate of mass loss of LDPE is significantly reduced at 400 °C, but the rate of mass loss of EVA is significantly increased. This may result from the evolution of water disrupting the protective layer. At 450 °C, ATH reduces the rate of mass loss of both LDPE and EVA to a similar extent in the absence of a coherent protective layer.

Abstract: The ignition and pyrolysis of some copolymers of methyl methacrylate (MMA) with diethyl(methacryloyloxymethyl)phosphonate (DEMMP) have been studied by a simple tube furnace and by isothermal and non-isothermal TGA The results indicate that copolymers containing DEMMP thermally degrade, under both air and nitrogen, by a mechanism which is more complex than that (simple depolymerization) for poly(methyl methacrylate) (PMMA) The copolymers containing 10 mol% or more of DEMMP are inherently flame retardant in that they fail to autoignite at 480 °C and take longer to autoignite at 490 °C than PMMA or MMA-DEMMP copolymers containing only 5 mol% DEMMP The formation of a carbonaceous residue or char on combustion of the MMA-DEMMP copolymers suggests that flame retardance is due mainly to reactions in the condensed phase

Abstract: The dielectric constant e′ and loss factor e″ of deionized water and poly(vinyl alcohol) in aqueous solutions are measured in the frequency region 200 MHz to 20 GHz at four different temperatures (25, 35, 45 and 55 °C). Complex plane plots (ie e″ vs e′) are drawn to obtain the static dielectric constant e0, high frequency dielectric constant e∞, distribution parameter α and average relaxation time τ0. The variations of dielectric constants with increasing solvent concentration and temperature are discussed in terms of solute–solvent and solute–solute interactions. The average relaxation time τ0 of poly(vinyl alcohol) aqueous solutions is found to the very short. It is also observed that the relaxation time is almost independent of the viscosity of the solution. The effect of water concentration on macromolecular size, shape and flexibility of the molecular chain are discussed using the observed values of dielectric relaxation times at different temperatures. The possibility of multiple dielectric dispersion is also discussed with concentration variation. © 2000 Society of Chemical Industry