Allylic monomers as reactive plasticizers of polyphenylene oxide. Part II: Cure kinetics

As part of an investigation of the processing of polyphenylene oxide (PPO) with polymerisable plasticizers, the curing kinetics of various diallylic monomers – diallyl ortho phthalate (DAOP), diallyl terephthalate, triethylene glycol diallyl ether and diethylene glycol diallyl carbonate) – and triallylic – triallyl cyanurate and triallyl isocyanurate – with radical initiators of differing activity were studied. All the monomers exhibited similar cure kinetics with each initiator and the exotherm peak temperatures correlated well with the reactivity of the initiators as measured by the 1 h half-life temperatures. Multiple scan-rate dynamic DSC studies gave similar activation energies to those obtained from isothermal rheology studies of gelation. The effects of the presence of PPO on the curing of diallyl ortho phthalate (DAOP) were studied using dicumyl peroxide (DCP) and tert-butyl hydroperoxide (TBHP) as initiators and differing behaviour was observed. In the PPO:DAOP/DCP system, the reaction rate was reduced with increasing PPO due to a dilution effect but the heat of reaction was generally unaffected. However, in the PPO:DAOP/TBHP system, a significant increase of cure rate was observed in the presence of 20 wt.% PPO due to the catalysis of TBHP by Cu²⁺ and Co³⁺ impurities in the PPO, but the cure rate was slightly reduced with increasing PPO content. In addition, the heat of polymerisation for the PPO:DAOP/TBHP blends were usually less than that for the pure monomer. This information can be used in the processing of PPO with DAOP as a polymerisable plasticizer.     

Diallyl orthophthalate as a reactive plasticizer for polycarbonate. Part 1: Uncured system

Diallyl orthophthalate (DAOP) has been used as a reactive plasticizer for polycarbonate (PC) due to the low reactivity and high conversion at the gel point of DAOP and its high solubility in PC. Miscible blends of PC with various ratios of DAOP have been investigated using gel permeation chromatography, differential scanning calorimetry, rheometry, dynamic mechanical thermal analysis and optical microscopy (with and without polarised light), and the experimental results have shown that DAOP can act as an effective plasticizer in PC processing by lowering the melt viscosity, the melting and the crystallisation temperatures, and by reducing the glass transition temperature of the blend. However, the molecular mobility provided to the PC chains by DAOP causes crystallisation of the PC as shown by optical microscopy and DSC and this places limits on the potential reduction in the processing temperature of the blend.     

Dynamic mechanical properties of immiscible polymer systems with and without compatibilizer

Blends of polyamide12 (PA12) and isotactic polypropylene (PP) were prepared by melt mixing, in an internal mixer, in the presence and absence of compatibiliser. The compatibiliser used was maleic anhydride grafted PP (PP-g-MA). The dynamic mechanical properties of the blends with and without compatibiliser were studied. Although compatibilization shifted the glass transition temperatures (T_g's) of component polymers only marginally, it significantly enhanced the storage modulus of the blends. The storage moduli of the uncompatibilised blends were compared with those predicted by theoretical models. Correlation between the dynamic mechanical properties of both compatibilised and uncompatibilised blends and their phase morphology was made.     

Phase equilibria and excess properties for binary systems in reactive distillation processes Part I. Methyl acetate synthesis

Isothermal vapor–liquid equilibrium (VLE) and excess enthalpy (H^E) data were measured for binary systems required for the design of reactive distillation processes for the methyl acetate production. The isothermal P–x data were measured with the help of a computer-operated static apparatus. A commercial isothermal flow calorimeter was used for the determination of the heats of mixing. Temperature-dependent interaction parameters for the UNIQUAC model were fitted simultaneously to the experimental data from this work and other authors.     

Obtaining thin films of “reactive polymers” on metal surfaces by electrochemical polymerization: Part II. Alcohol substituted polyphenylene oxide films

The selective electrochemical oxidation of the phenol function in the case of hydroxymethyl phenol derivatives (o^?, m^?, p-hydroxybenzyl alcohol) leads to “reactive polymer” films of polyphenylene oxide substituted by CH₂OH groups. The transformation of the hydroxyl function into an ester function by acetyl chloride indicates the reactivity of the CH₂OH group. As for the family of carbonylated polyphenylene oxide films, reactivity is limited to the superficial layers of film. Average film thickness is between 50–100 nm; however with the ferrocene-ferricinium system acting as a redox catalyst, it can reach about 300 nm. This catalytic mechanism intervenes only when the oxidation potential of the ferrocene-ferricinium couple is very similar to that of the phenol derivative.     

Characterisation of eco-friendly processing aids for rubber compound: Part II

According to the KEMI report, products with polycyclic aromatic compounds, PCA, levels exceeding 3% by weight must be labelled. The report pointed out that worn tyre tread material was being spread on the roadsides, introducing high amounts of PCA into the environment. PCA is having toxic effects on aquatic organisms. Polyaromatic-hydrocarbon-rich extender oils are to be banned by December 2009, which gives rise to challenges for the oil and rubber industries. In the present work, 10 types of naturally occurring oils and six types of petroleum-based oils were characterised in natural-rubber-based truck tyre tread cap compound. Compounds made with some of the naturally occurring oils showed better mechanical and dynamic mechanical properties.     

Synthesis of fluoro-substituted monomers bearing a functionalised lateral chain: Part 2. Preparation of sulfoxides and sulfones containing monomers

The oxidation of ω-(ω-perfluoroalkylalkyl-sulfanyl)-alkyl acrylates to corresponding sulfoxides and sulfones is described in this paper.     

Aqueous biphasic systems formed by nonionic polymers I. Effects of inorganic salts on phase separation

The effect of salts KSCN, KI, KBr, KCl, KClO₄, KF, K₂SO₄ and NH₄Cl, LiCl, NaCl, KCl, CsCl on the binodials of the phase diagrams for aqueous biphasic dextranpolyvinylpyrrolidone, dextran-polyvinyl alcohol, dextran-ficoll and dextran-polyethylene glycol systems was studied. It is established that the K-salts present at the concentrations of 0.1 and 0.5 mol/kg alter the binodials of the phase diagrams for the above systems. The effect of a salt is found to be related to the lyotropy of the salt quantified by the salt molal surface tension increment. It is assumed that phase separation in an aqueous polymer biphasic system is affected by the presence of a salt mainly due to the effect of the salt on the structure and/or state of water in the system.     

Structure transfer from a polymeric melt to the solid state. Part I: The influence of chain entanglements in linear polyethylene

Melt-spinning experiments were carried out at high quenching rates. Mechanical properties (elongation at break, natural draw ratio, and elastic recovery) have been measured. Significant variations of these quantities were observed when extrusion conditions were changed. This has been attributed to different states of the entanglements within the melt, which are directly transferred into the solid state. This intercorrelation between melt and solid-state properties has been substantiated in the case of rapidly cooled samples, where a poor crystallization on one side and a simultaneous good conservation of melt history on the other side are provoked.     

Properties and treatments of pulps from recycled paper. Part I. Physical and chemical properties of pulps

The mechanical, physical, and chemical properties of recycled pulps were evaluated after a series of treatments designed to improve and/or modify the pulp characteristics. Tensile strength, bursting strength, and apparent density of the pulps decreased with recycling. However, the tear strength, in most cases, increased after the first recycle and then decreased after the second recycle. Carboxyl content and WRV of pulps also decreased with recycling. Chemical treatments did not increase the bonding ability of recycled pulps and, in most cases, decreased the physical properties of the pulps. Altering the physical state of the cellulose microstructure through additional swelling did not appear to be a significant factor for strength restoration. It may be that the hemicelluloses plan a greater role in recycling than originally thought.     

Relaxation of a viscoelastic gel bar: I. theory

When a rod of gel is deflected in 3-point bending, two types of relaxation process occur: hydrodynamic relaxation caused by flow of liquid within the gel network, and viscoelastic relaxation of the network itself. The kinetics of load relaxation have previously been analyzed for the case of hydrodynamic relaxation within a perfectly elastic network. That analysis describes, for example, the behavior of silica gel in a nonreactive solvent, such as acetone. When the liquid can attack the gel network, then true viscoelastic relaxation is superimposed on hydrodynamic relaxation, and that situation is examined in the present paper. To a very good degree of approximation, the total relaxation is equal to the product of the hydrodynamic and viscoelastic relaxation functions. In Part II, it will be shown that the present analysis describes the behavior of silica gel in an aqueous solvent and in an alcohol/amine solution.     

Interactions and partitioning of diluents/plasticizers in hydroxypropyl methylcellulose and polyvinyl alcohol homopolymers and blends. Part I: Diethylene glycol

The interactions and partitioning of diethylene glycol (DEG) in polyvinyl alcohol (PVA), hydroxypropyl methylcellulose (HPMC) and their blends has been studied. DEG acted as efficient plasticizer for both homopolymers, lowering theirT _g and relative rigidity. Kelly-Bueche-type equations were fitted successfully to the experimental data and yielded an interaction parameter,K , between DEG and each polymer. Incorporation of DEG into two-phase blends of PVA and HPMC with 40, 50 and 60% PVA did not change the significant incompatibility of the two components and plasticized both phases. Composition calculations based on Kelley-Bueche-type expressions fitted to the experimental data afforded determination of the partition coefficients of DEG into the two phases of the blends. In the case of the 5050 weight% system, it partitioned almost equally into both phases. The results are discussed in terms of the DEG affinity to interact with the two polymers by means of the dispersive, polar and hydrogen-bonding contribution to the solubility parameters.     

Chemical preparation of conductive elastomeric blends: Polypyrrole/EPDM. I. Oxidant particle-size effect

This work describes the preparation of polypyrrole and EPDM rubber blends, PPy/EPDM, by the sorption of pyrrole (vapor phase) in an EPDM matrix containing CuCl₂. We investigated the effect of the oxidant particle-size on the sorption and polymerization equilibrium, electrical conductivity, and mechanical properties of the blends. Independently of the CuCl₂ concentration and polymerization time, the polypyrrole weight fraction in the blend, X_ppy, increases when the oxidant particle-size in changed from 150–250 μm to smaller than 106 μm. For blends containing 50 phr of CuCl₂, obtained following 72 h of exposure to pyrrole, an increase in the Young's Modulus (from 2.2 ± 0.2 to 3.9 ± 0.6 MPa) and an increase in the electrical conductivity (from 10^?9 to 10^?7 S cm^?1) was observed when the oxidant particle-size was decreased. Infrared spectroscopy, thermogravimetric analysis, scanning differential calorimetry, and scanning electron microscopy were used in sample characterization. © 1994 John Wiley & Sons, Inc.     

Use of DTA-TG in the evaluation of autoclaved cement-based systems: Part I. Cement-brick waste blends

Fired-clay products such as bricks, tiles and pavers, are made in large volumes for use in a variety of construction applications throughout the world. A significant proportion of them ends up being a waste product either during their production process or the demolition of buildings. High pressure steam curing or autoclaving has proven extremely versatile for the manufacture of cement-based building products incorporating waste materials such as fly-ash and blast furnace slag. The nature of hydration products in an autoclaved cement based system incorporating different amounts of finely ground brick waste was investigated by means of thermal analysis and XRD, and is the subject of this paper.This revised version was published online in November 2005 with corrections to the Cover Date.     

Structure and microporous formation of cellulose/silk fibroin blend membranes: Part II. Effect of post-treatment by alkali

Blend membranes (RCF1) were prepared from mixture solution of cellulose and silk fibroin (SF) in cuoxam by coagulating with acetone–acetic acid (4:1 by volume). The blend membranes were subjected to post-treatment with 10% NaOH aqueous solution, and their structure and properties were characterized by FT-IR, X-ray diffraction, DSC, SEM and DMTA. In previous work, cellulose/SF blend membranes (RCF2) prepared by coagulating with 10% NaOH aqueous solution formed a microporous structure, in which the SF as a pore former was almost completely removed from the membrane. However, when the blend membranes RCF1 were immersed in 10% NaOH aqueous solution for post-treatment, a strong hydrogen bonding between cellulose and SF inhibited the removal of SF. Although alkali is a good solvent for SF, the blend membranes RCF1 such obtained from cellulose and SF were alkali resistant. The crystallinity and the mean pore size of the blend membranes slightly decreased with increasing post-treatment time. This work provided a cellulose/silk blend membrane, which can be used under alkaline medium.     

Surface modification strategies for multicomponent polymer systems,Part I: Use of diblock copolymers as surface modifiers of rutile

Various functional diblock copolymers have been used as surface modifiers for rutile pigment in an effort to condition the solid for eventual use in multicomponent polymer systems. Coated surfaces were analyzed by inverse gas chromatography at infinite and finite dilution of the vapor phase, and by XPS. At high coverages (about 10% by weight of the pigment), the diblocks were randomly oriented at the air interface, effectively masking the surface of the rutile. At low diblock concentrations acid/base interactions dominated the orientation of the adsorbed molecule at the rutile interface, thereby also affecting the orientational states at the air interface. In this condition, the performance of the pigment in specified host polymer systems may be expected to vary with the selection of the diblock copolymer modifier. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1793–1805, 1997     

X=Y-ZH systems as potential 1,3-dipoles. Part 61: Metal exchanged zeolites, silver(I) oxide, Ni(II) and Cu(I) complexes as catalysts for 1,3-dipolar cycloaddition reactions of imines generating proline derivatives

A range of regio- and stereo-selective 1,3-dipolar reactions of imines of α-amino esters, generating polysubstituted prolines, catalysed by silver(I) exchanged zeolites or silver(I) supported on titania, both in combination with DBU, are described. The use of a catalytic amount of silver(I) oxide, Ni(II) complexes and cuprous iodide as catalysts for the cycloaddition reactions are also disclosed.     

Porous membranes modified by hyperbranched polymers: I. Preparation and characterization of PVDF membrane using hyperbranched polyglycerol as additive

Porous membranes were prepared via phase inversion process from casting solution composed of poly(vinylidene fluoride) (PVDF), N,N-dimethylacetamide (DMAc), and hyperbranched polyglycerol (HPG). The membranes were characterized in terms of surface and bulk chemical compositions, morphology, water contact angle, porosity, and water flux. The effects of HPG content on membrane structures and properties were investigated. The effect of HPG addition on the hydrophilicity was discussed as well when the compositions of coagulation bath were changed. To better understand the special effects of HPG on the structures and properties of the membranes, PVDF membranes prepared using HPG as the additive were compared with those prepared using polyethylene glycol (PEG) as the additive.     

Efficient and Accurate Methods for the Computation of Thermodynamic and Transport Properties of Multitemperature Thermal Plasma. Part I: Thermodynamic and Heavy Particle Transport Properties

In this paper we present numerical efficient methods for the computation ofthermodynamic and transport properties of nonequilibrium thermalplasmas. Thermodynamic properties of mono- and diatomic speciesare calculated directly from partition functions. The evaluation oftransport properties is based on the kinetic theory using the classicalChapman–Enskog approach to solve the heavy particle Boltzmannequation. A multitemperature model is used to consider thermalnonequilibrium.