Polymer
The extent of phase mixing during ageing of semi-interpenetrating polymer networks of poly(ethylene glycol)(PEG) and poly(trimethylolpropane triacrylate)(TMPTA) was determined using differential scanning calorimetry. Twelve-month-old networks containing PEG with molecular weights of 8000–20000 g mol −1 were more phase-separated following ageing than freshly prepared networks, while other PEG...
The formation kinetics of scleroglucan-zirconium gels was studied using rheological measurements. It was possible to determine such kinetics by following the change in solution elastic modulus as a function of time. Gelation kinetics was found to increase vs. polymer concentration according to a power law function. In contrast, when zirconium concentration was increased, gelation kinetics was found...
The α- and β-spherulites in polypropylene (PP) were identified by direct observation in the scanning electron microscope after appropriate etching. The α-phase has a dark contrast while the β-phase is brighter. Results concerning the individual behaviour of α- and β-spherulites in polypropylene samples which have been subjected to tensile and shear loading are reported. Under tensile loading, the...
This paper presents a measurement of the photocurrent of a poled blend of 80 wt% poly(vinylidene fluoride) (PVDF) and 20 wt% poly(methyl methacrylate) (PMMA) containing 5 wt% N-phenylcarbazole (PhCz) and 1 wt% 2,4,7-trinitro-9-fluorenone (TNF) molecules and a discussion of the photoionization of the PhCz-TNF complex by the internal electric field. The high internal electric field, of the order of...
N-isopropylacrylamide (NIPA)/N-n-propylacrylamide (NNPA) copolymer gels of various molar ratios were prepared by radical polymerization and the relationship between the swelling behaviour of the gels and the copolymerization ratio was studied experimentally. The effect of a crosslinking point on the swelling behaviour of the NIPA gels was investigated by preparing the gels with various crosslinking...
The present part of this series on the temperature window of reduced flow resistance in polyethylene confirms and consolidates the inference from the first paper in this series that the source of the rheological singularity resides in the capillary, specifically at the capillary wall, in contrast to the previously held view that the elongational flow at the entrance is responsible for the effect....
The alcoholytic destruction of poly(ethylene terephthalate) (PET) with diethylene glycol (DEG) is studied. The influence of the DEG amount on the structure of the obtained oligoesters is investigated. On the basis of the experimental results, a probable mechanism is proposed for the alcoholysis of PET at large excess of DEG. The molecular weight characteristics of the obtained oligomers are studied...
The mechanical properties and fracture behaviour of polyurethanes with two hardness levels have been measured. The polyurethanes were based on polytetramethylene ether glycol (PTMEG) and toluene diisocyanate (TDI) and two different curatives, or chain extenders - methylene-bis-orthochloroaniline (MBOCA) and dimethylthiotoluene diamine (Ethacure E300). The polyurethanes made using MBOCA as the curative...
Static secondary ion mass spectrometry has been used to investigate orientation effects at the surfaces of segmented polyetherurethanes. The presence of hard segments at the polymer surface was found to be dependent upon the sample preparation method. Spin casting can produce a larger hard segment content than straightforward solvent evaporation, and films produced by spin casting slowly reorganize...
An analysis of the conformation of a stiff-chain polyimide in solution is given. It is shown that these polyimides exhibit the rather low persistence length of 13 nm despite the fact that the repeating unit consists of stiff and fully linear building blocks. A comparison with recent experimental and theoretical findings on similar systems corroborates the present analysis and suggests the bending...
Structural changes in poly(ethylene terephthalate) (PET) induced by annealing under dry nitrogen gas flow (dry annealing) and in water (wet annealing) were investigated using small- and wide-angle X-ray diffraction methods, density measurements, differential scanning calorimetry and dynamic viscoelastic measurements. The degree of crystallinity of PET was evaluated by wide-angle X-ray diffraction...
We have replaced the five Cl atoms in dichlorophosphinylphosphorimidic trichloride with oxyethylene acrylate groups. The monomers obtained were polymerized by taking advantage of the double bonds of the acrylic groups. This was done by ultraviolet irradiation in the presence of a sensitizer. It is found from Fourier transform infra-red, 1 H and 31 P nuclear magnetic resonance spectroscopy...
Poly(ethylene oxide)α,ω-dicarboxylic acid alkali metal salts were prepared as inherently ion-conductive salts. Since the average molecular weight of the poly(ethylene oxide) matrix is about 300, the salts are totally amorphous and show ionic conductivity of 10 −4 −10 −6 S cm −1 at 50°C. An upwardly convex curve was seen in the Arrhenius plots of the ionic conductivity, reflecting...
Two series of novel oligo(ester amide)s based on sebacic acid/1,6-hexanediamine/ɛ-caprolactone and octadecanedioic acid/1,6-hexanediamine/ɛ-caprolactone were synthesized. The determination of the molecular weights with both gel permeation chromatography and 1 H nuclear magnetic resonance (n.m.r.) showed that they vary from 1000 to 6000. Differential scanning calorimetry and thermogravimetric...
An emulsion freeze-drying method for processing porous biodegradable copolymers of polylactic and polyglycolic acid (PLGA) scaffolds was developed. Scaffold porosity and pore sizes were measured using mercury porosimetry. Foams with porosity in the range 91–95%, median pore diameters ranging from 13 to 35 μm (with larger pore diameters greater than 200 μm), and specific pore area in the range 58–102...
A phase transfer technique was used to characterize the surface of a γ-radiation-vulcanized natural rubber latex (RVNRL). This technique involves titration of the negatively charged natural latex with cationic surfactants in the presence of an organic phase. The surface charge of the RVNRL was calculated from the amount of surfactant required to cause transfer of the rubber to the organic phase (critical...
The impact strength of blends consisting of polystyrene (PS) and ethylene-propylene-diene rubber (EPDM) could be increased by adding a poly(styrene/ethylene-propylene) (SEP) compatibilizer and an organic peroxide during reactive extrusion. The increased impact strength could be related to an enhanced adhesion between the dispersed EPDM phase and the PS matrix, as a consequence of radical graftlink...
Biphenyl compounds having diene groups were synthesized. In the first class of compounds, the diene groups were directly attached to one end or both ends of the biphenyl through ester bonding. In the second class of compounds, the diene groups were attached to one end or both ends of the biphenyl through methylene spacers. Only the first class of compounds were found to show a liquid-crystalline phase...
Poly(ethylene terephthalate) (PET)/poly(butylene terephthalate) (PBT) blends (xPET/(1 - x)PBT) characterized by amorphous initial structure are prepared by ultraquenching of the melt between two metal rolls rotating in a liquid nitrogen bath. The thermal behaviour, miscibility, crystallization and mechanical properties of PET/PBT blends are investigated after three years of storage at − 15°C. The...