Glass transition temperatures of poly N — (N — alkyl)—maleimides

The glass transition temperatures (T_gs) of a series of poly N-(n-alkyl) maleimides covering only the even members with side chains ranging in length from ethyl to n-octadecyl have been studied from room temperature to above T_g. T_gs and thermal quantities have been determined from the specific volume-temperature relations only for the higher (n=8, 10, 12, 14, 16 and 18, where n = no of CH₂) members of the series. However for the lower ones (n = 2, 4, 6, 8 and 10) T_gs have been detected from heat capacity-temperature traces of differential scanning calorimetry diagrams by extrapolation to zero rate of heating. Accurate consistency was found in the values (n = 8 and 10) determined by both experimental methods. T_gS of these polymers continuously decrease as the number of methylene groups in the side chain is increased, and they have been correlated with the size of the n-alkyl group in the side chain. The results are in accord with a previously studied series concerning the effect of a long side chain on the T_g of a comb-like polymer in the amorphous state. T_gs of poly N-(n-alkyl) maleimides encompassing a wide range of methylene group content (n = 2, 4, 6, 8, 10 and 12) have been examined according to the Gordon-Taylor-Wood extrapolation with the objective of ascertaining the T_g of polyethylene (PE). Our approach of ignoring higher members of the homologous series in this extrapolation appears to be old and well known and it has been variously ascribed to different authors. Extrapolation of T_g values to 100% amorphous PE gives a T_g of 200/pm 10 °K in complete agreement with recent predictions made by Boyer from different sources of data. The Simha-Boyer free volume quantity Δa. T_g decreases slowly with the methylene group content in the longer terms (n = 8, 10, 12, 14, 16 and 18) of the series presumably because of a reduction in the polarity or an in-chain crankshaft loss mechanism which generates free volume in the glassy state, as stated by Boyer. T_gs do not correlate very well with the contributions of the atomic groups to the cohesive energy density (c.e.d.) so it can be concluded that c.e.d. is not the only factor determining T_g. However, a somewhat improved relationship might be obtained by taking into account the steric hindrance effect according to an approach made by Hayes.     

Diamond — an adsorbent of a new type

Carbon-containing adsorbents are widely used in various industries, medicine, and pharmacology. The most abundant of them are activated coals, graphitized thermal carbon black, molecular sieves, etc. [Active Coals and their Industrial Applications (1984), 214]. Synthetic diamond presents a new class of carbon containing adsorbents. Diamond is a universal adsorbent that is characterized by chemical inertness and high strength. Another welcome effect is the possibility to modify and recover the diamond surface and, hence, to use the adsorbent repeatedly.     

Cyclodextrin-assisted polymerization—a new way to synthesize powder coat resins

Solid acrylic resins for powder clear coats are usually produced by solution polymerization. Much energy is consumed by distillation of organic solvents and grinding of the solidified polymer which are inevitable steps in this process. In our contribution we present a new way to synthesize powder clear coat resins by polymerization in aqueous solutions containing the renewable resource cyclodextrin. This process avoids both the distillation and the grinding step, because the product precipitates as a powder and can be filtered off.     

Reaction products of polyacrylonitrile with dicyandiamide — new flocculation agents —

A new flocculation agent is prepared by reaction of polyacrylonitrile with dicyandiamide in alkaline solution, followed by acid hydrolysis. The polymer contains guanamine-, N-carbimidoyl-N′-cyanoguanidine-, amido-, hydronaphthiridine-, and carboxylic-groups. In consequence of the alkaline and acidic groups present, the polymer shows polyampholytic properties and can be used as a primary flocculation agent. Fields of application are removal of contaminants dispersed in water, like waste, algae, bacteria and also in some cases dissolved substances like dyes, etc. Concepts of the flocculation activity and suggestions of application are discussed.     

Rubbery products from castor oil tris(thioglycolate)—A new polythiol

Castor oil tris(thioglycolate), a new trithiol, was synthesized from castor oil and thioglycolic acid. This thiol, which showed an inherent propensity to form a solid, insoluble film on exposure to air, was cured with lead peroxide and p-quinone dioxime, using various fillers. Mechanical properties of the cured products as well as their solvent resistance were determined.     

Prediction of vapor — liquid equilibria: Derivation of a new expression for vapor — liquid equilibrium correlations

To replace the interchange energy between two different types of molecules, two types of local energy parameters derived from Scott's two liquid concept are defined. When this definition is introduced into the quasichemical approximation, a new expression for correlating vapor-liquid equilibria in binary systems results. The new expression is semi-empirical in nature and for a binary system, it contains two adjustable parameters and a binary constant which are obtained from binary experimental data. It has been shown that the new expression can be used as a two-parameter equation. Its application was tested with thirty-four examples of highly non-ideal systems, including twenty-two systems at isobaric and twelve systems at isothermal conditions. Application to partially miscible systems is also examined. The results, correlated through the new expression, are compared with those obtained using the equations of Wilson and of Renon. The significance of the parameters of the new expression is discussed.     

Poly(fluoroalkoxyphosphazenes)—versatile seal materials

Poly(fluoroalkoxyphosphazene) fluoroelastomers are members of a new family of polymers based on a phosphorous–nitrogen backbone. Physical property evaluation tests have demonstrated that these fluorelastomers possess excellent stress–strain properties, low-temperature flexibility, thermal stability, and resistance to a variety of demanding environments including synthetic lubricants, hydrocarbon fuels, and aqueous caustics. Their service temperature range is about ?60° ?200°C. Poly(fluoroalkoxyphosphazene) fluoroelastomers have shown the capability to function in severe dynamic applications; i.e., lip seals (1? in. I.D.) performed for >1000 hr at 5500 rpm in MIL L-7808G lubricant at 115°C. Also, O-ring seals successfully completed a 1000-hr dynamic qualification test over a temperature range of ?54°–163°C in a rod seal test apparatus. These elastomers can be used for seals, O-rings, gaskets, diaphragms, hose, and protective coatings.     

(CH3) 4NHgBrI2—A new polar organic-inorganic double halide

(CH₃)₄NHgBrI₂ exhibits at room temperature a polar columnar structure based on edge-sharing anion tetrahedra with a double anion occupancy. Its orthorhombic space group is Pb2_lm. An unusual multiple phase transition sequence revealed by differential scanning calorimetry, dilatometry and permittivity vs. temperature measurements leads to a non-polar high temperature phase with a trigonal mercury coordination and the monoclinic space group P2_l/n.     

Polylactide (PLA)-Based Electrospun Fibrous Materials Containing Ionic Drugs as Wound Dressing Materials: A Review

The effect of the electrospinning process parameters on the morphology, alignment, and self-organization of the fibers into bundles and/or yarns are outlined. The fabrication of polylactide materials containing ionic drugs by electrospinning is emphasized. The main approaches used for the preparation of electrospun drug-loaded materials: electrospinning of a mixed solution containing the polymer(s) and the drug(s) or dual spinneret electrospinning of separate drug-containing solutions are compared. The latter approach allows the obtaining of drug-loaded fibrous materials while avoiding the drug interaction. The potential application of the obtained materials containing ionic drugs as wound dressings is outlined.     

Phase separation temperatures in the polystyrene—poly(α-methyl styrene)—methylcyclohexane system

The phase separation temperatures (PST) in the ternary system polystyrene (PS) (M_w = 1.75 × 10⁴ g mol⁻¹ — poly(α-methyl styrene) (PαMS) (M_w = 6.0 × 10⁴) — methylcyclohexane (MCH) and the binary systems PS-MCH and PαMS-MCH have been determined by using a He---Ne laser light-scattering apparatus over the total polymer weight fraction (W_{PS + PαMS}) range of 0.018 to 0.80 and various polymer blend ratios. The PST determined at a scattering angle of 0° agreed with those at 90° for the binary systems over polymer concentrations of 0.1 to 0.7 and for the ternary over W_{PS + PαMS} of higher than 0.3. Deviations of the PST determined at an angle of 90° from those at 0° were observed in the ternary system when W_{PS + PαMS} was lower than 0.3. Two phase separation temperatures, at which the intensity scattered from zero angle changed discontinuously, are observed at concentrations lower than W_{PS + PαMS} = 0.042 in the ternary system. The PST in the ternary system decreases monotonically with increasing W_{PS + PαMS} over 0.3 to 0.7. The phase diagram for the PS-PαMS-MCH system at W_{PS + PαMS} = 0.8 is characterized by a maximum PST around − 14°C.     

Urushi (oriental lacquer) — a natural aesthetic durable and future-promising coating

What is oriental lacquer? This article attempts an answer to this question from the viewpoint of materials chemistry and coatings technology of the lacquer in Japan and also describes a strategy for developing oriental lacquers in harmony with the natural environment.     

SYNTHESIS OF POLY(METHYL METHACRYLATE)—CLAY NANOCOMPOSITES

Poly(methyl methacrylate)/clay nanocomposites were synthesized via in situ free radical polymerization of methyl methacrylate (MMA) in the presence of functionalized clay. Montmoril-lonite (MMT), a smectic type of clay, was treated with a commercial cationic surfactant, benzalkonium chloride (BAC), and a synthesized zwitterionic surfactant, octadecyldimethyl betaine (CI8DMB) Functionalized MMT was prepared via an ion exchange between Na,ions in the clay and the surfactant cations in aqueous medium. The intercalation of the surfactant in the clay galleries was determined using X-ray diffraction (XRD). The interlayer spacing for C18DMB was 2.03nm, higher than 1.86nm observed for BAC. This is due to longer chain length of C18DMB. Both organophilic clays formed a viscous gel when dispersed in the monomer, MMA. Poly(methyl methacrylate) (PMMA) nanocomposites were obtained by polymerizing the dispersions. XRD and transmission electron microscopy (TEM) indicate predominant exfoliation of the silicate layers in the polymer matrix for MMT treated with C18DMB, and partial exfoliation for MMT treated with BAC     

Print-Batch(Cold)—A New Process for Wool

A cold printing process has been developed from the IWS pad-batch(cold) method for the dyeing of wool cloth. The chemical aspects of the technique are discussed with particular reference to the role of sodium bisulphite in promoting dye fixation and increasing the colour yield. The system used for the selection of reactive dyes for application to wool in the cold is described. Typical printing procedures are outlined.     

Tetramethylammonium 3-aminopropyl dimethylsilanolate—aminopropyl dimethylsilanolate—a new catalyst for the synthesis of high purity,high molecular weight α,ω-bis(aminopropyl) polydimethylsiloxanes

Tetramethylammonium 3-aminopropyl dimethylsilanolate, readily prepared from bis(3-aminopropyl) tetramethyldisiloxane and tetramethyl-ammonium hydroxide pentahydrate, has been found to serve as a highly effective catalyst for the ring opening polymerization of cyclic siloxanes with an end blocker such as bis(3-aminopropyl) tetramethyldisiloxane to give aminopropyl terminated linear polydimethylsiloxanes. By following a novel two stage procedure, even high molecular weight (5,000–55,000 g/mol) silicone diamines were able to be prepared in a high state of purity; chain extension reactions of these diamines with diisocyanates gave a series of high molecular weight silicone polyureas with good elastomeric properties.     

Nanocomposite fire retardants — a review

Most fire retardant nanocomposites are made from layered silicates and organic polymers, a variety of methods are used in their synthesis. The mechanism for the fire retardancy of these composites is generally considered to be due to the structure of the char formed during combustion, which enables the char to thermally insulate the polymer and inhibit the formation and escape of volatiles during combustion. Fire retardant nanocomposites require relatively low concentrations of silicates for activity, resulting in low additional costs and weight. Improvements in the bulk physical properties of the polymer can be additional advantages over traditional fire retardants. Copyright © 2000 John Wiley & Sons, Ltd.