H Magnetic resonance imaging of rigid polymeric solids

Implementation of the ¹H magnetic resonance single-point imaging technique has provided new opportunities for the direct imaging of rigid solids, particularly semicrystalline polymers with spin-spin relaxation times, T^*₂, of the order of 10 μs and greater. Potential applications of industrial relevance in the following areas are briefly discussed and illustrated: fabricated/processed parts, photochemical degradation, oxidation, and blend characterization.     

THERMAL BEHAVIOR OF THERMOTROPIC HYDROXYETHYL CELLULOSE ACETATE/POLYETHYLENE BLENDS

The thermal behavior of thermotropic hydroxythyl cellulose acetate (HECA)/polyethy-lene (PE) blends has been studied by DSC. It is found that the blends of HECA and PEare immiscible but the crystallization of PE is affected by HECA chains in the blends withmore than 50% HECA, which results in the subordinate crystallization of PE and the for-mation of imperfect structures in the PE crystals. The imperfection of PE crystals in theblends can be eliminated after annealing at 393K.     

Two-dimensional infrared correlation spectroscopic studies of polymer blends--specific interactions in polyethylene adipate/cholesteryl palmitate blends

Generalized two-dimensional infrared (2D IR) correlation spectroscopy has been applied to the study of the conformational changes and specific interactions in blends of polyethylene adipate (PEA) and cholesteryl palmitate (CP). IR spectra of CP, PEA, and their blends of different compositions: 10/90, 16/84, 32/68, 64/36, and 80/20 have been recorded. In order to apply 2D IR correlation analysis, the samples are divided into two sets: set A with high PEA content 0/100, 10/90, 16/84, 32/68 CP/PEA and set B with high CP content 64/36, 80/20 and 100/0 CP/PEA. The 2D IR synchronous correlation analysis separates the bands of PEA from those of CP. The cross-peaks in 2D IR asynchronous correlation analysis are indicative of the specific interaction or the conformational change in the blends. The bands of CO, OH and C-O vibrations of PEA, and CH(3) and C-O vibrations of CP that are very sensitive to the intermolecular hydrogen bonding effect and consequently the partial miscibility of components, have been assigned by 2D correlation analysis.     

Functionalization of Poly(Organophosphazenes). IX. Light-Induced Grafting Reactions of Maleates onto Aryloxy-Substituted Poly(Organophosphazenes)

Abstract

In this paper the light-induced grafting reaction of dimethyl maleate, diethyl maleate, dibutyl maleate and diethyl fumarate, onto aryloxysubstituted phosphazene polymers, to form polyphosphazene copolymers containing grafted succinate groups, is investigated by means of IR spectroscopy and the equilibrium swelling technique of polyphosphazene films. The importance of several different experimental factors that can influence the final succinate grafting yields is discussed, i.e. the type and concentration of the polyphosphazenes and of the unsaturated products, reaction time, the absence or presence of molecular oxygen or of the 1-vinyl-2-pyrrolidone monomer, and the concentration of the benzoin ethyl ether photoinitiator.

Furthermore, it is shown that the overall efficiency of the lightinduced grafting process is lower than that previously measured for the reaction initiated thermally using peroxide species, and that the photochemical grafting reaction always occurs with no degradation of the phosphazene macromolecules.

The possibility of exploiting these new phosphazene substrates in blend technology has been considered.     

Glow wire ignition temperature (GWIT) and comparative tracking index (CTI) of glass fibre filled engineering polymers, blends and flame retarded formulations

Engineering thermoplastic polymers such as polyamides, polycarbonates, semi-crystalline aromatic polyesters and their blends are widely used as insulating materials in electrical and electronic appliances. Flame retardants are often employed in the formulation of these materials, since good performance in terms of ignition and tracking resistance, evaluated by Glow Wire Tests (GWIT) and Comparative Tracking Index (CTI) are required in these applications. In this paper, a comparative evaluation of GWIT and CTI performances has been simultaneously performed for a wide set of glass fibre filled materials chosen among engineering thermoplastics and their blends. Some flame retarded formulations have been also tested, in order to screen the effects of various additives. Useful indications have been obtained on the effect of each polymer and additives on GWIT and CTI properties. In addition, interesting synergies have been observed, especially by blending polyesters and polyamides. Thermogravimetric measurements of char yields have been successfully related with CTI behaviour. The presence of additives changes the structure of the carbonaceous residue, hence the conductivity of the tracks. Neat polycarbonate passed the GWIT test but not CTI, while poly(butylene terephthalate) showed the best balance of GWIT and CTI performance among the pure resins tested. Blending polycarbonate with polyester did not improve significantly GWIT performance, but had a negative effect on tracking resistance. Polyesters/polyamide blends were dominated by polyester in GWIT, but they showed synergistic effects in CTI.