Danuta Żuchowska

Influence of butadiene/styrene copolymers on the modification of polypropylene in electron beam irradiation

Radiation chemistry of the system: styrene/butadiene/styrene (SBS) copolymer with polypropylene, has been investigated in the full range of proportions from 0% SBS-100% PP to 100% SBS-0% PP. Ionizing energy deposition is distributed to absorbing moieties according to their contribution to the electron pool in the material. The participation of primary ionization acts in constituents of low concentration is negligible, but these compounds take part in secondary reactions. These are detected by specific techniques for determination of transients, e.g., byelectron paramagnetic resonance (EPR). Radiation generates alkyl radicals inthe pure PP, which change subsequently into peroxide radicals in the presence ofoxygen. At high concentration of SBS the transfer of paramagnetic centers SBS • →PP • is observed. Important product analysis methods, i.e., UV-Visabsorption spectrophotometry, can be applied in polymer chemistry only as diffuse reflected light spectrophotometry (DRS), described in the preceding paper, as a new approach to the radiolysis recognition. The presence of stable unsaturations formed by radiation are observed by DRS. These effects are drastically reduced already by the presence of 10% of SBS, what indicates intensive protection action and the transfer of single ionization spur sites.

Free radicals in electron beam irradiated blends of polyethylene and butadiene–styrene block copolymer

Abstract Two-components blends, of compositions in a range from 100% of high density polyethylene (PE) to 100% of butadiene–styrene block copolymer (SBS) were investigated from the point of view of basic radiation chemistry and modifications of technological and chemical properties. Irradiations were performed with 10 MeV electrons to doses of 30, 60 and 120 kGy, by the split dose technique to avoid thermal effects. EPR spectra were measured with the Bruker 300 ESP spectrometer, using a computer program for the deconvolution and analysis of spectra.

Some physical properties of polypropylene-phenolic microsphere blends

Abstract The effects of phenolic microspheres (PFM) on crystallinity and mechanical properties of isotactic polypropylene were studied. Isotactic polypropylene-PFM blends were formed by injection or moulding methods. The addition of PFM influences neither the degree of crystallinity of the polypropylene matrix nor the elastic properties of the composites. The specific work of deformation to yield decreases rapidly when the volume fraction of PFM exceeds 0.01.

Thermal dehydrochlorination of poly(vinyl chloride)-epoxidized butadiene/styrene triblock copolymer blends

The effect of the type of epoxidized butadiene/styrene block copolymer [ESBS; linear (B/S) or radial (E(B/S)n), containing 0–27% of epoxy groups] on the thermal dehydrochlorination of poly (vinyl chloride) (PVC)-ESBS blends (ESBS content 10%) was investigated in the temperature range 170–180 °C, under a non-oxygen atmosphere. Thermal stability of the PVC-ESBS blends was estimated on the basis of induction time, t0, and maximum rate of hydrochloride emission, Vmax from the system. It was found that, for a similar degree of epoxidation of the SBS copolymer, the induction time i.e. the time after which emission of HCl begins, is longer in the series PVC < PVC-SBS < PVC-EB/S < PVC-E(B/S)n, and the same is true for thermal stability. However, the maximum rate of emission of HCl is lowest in the case of PVC-EB/S blends, in the range of molar ratios from 0.5 to 2.0 × 1O−2. On the basis of the dependence Vmax = f(EBVC), it was found that there is a certain content of epoxidized butadiene (EB) units in a mixture which causes the optimum stability of poly (vinyl chloride) during heating. During thermal destruction of the PVC-ESBS blends, the HC1 evolved undergoes addition both to epoxy fragments and to double bonds. The degree of conversion of EB units in time t0 is 20% at 170 °C and 30% at 180 °C. The glass transition temperature, Tg, of PVC in the PVC-ESBS blends shifts towards higher temperatures by about 6–8 °C, proving the existence of crosslinking processes during moulding of the blends. The epoxidized butadiene/styrene radial block copolymer, E(B/S)n, is a better thermal stabilizer of PVC than the linear EB/S copolymer.

Investigation of the structure of isotactic polypropylene—thermoplastic elastomer blends by means of X-ray scattering

Abstract Blends of semicrystalline isotactic polypropylene (iPP) with two types of elastomer, butadiene/styrene (BS) and hydrogenated isoprene/styrene (HIS), block copolymers were investigated by means of wide-angle and small-angle X-ray scattering. Except for the sample with a low concentration of BS (5 wt%), where the copolymer macromolecules are probably dispersed in the amorphous phase of iPP, the blends can be described as two-component systems (copolymer-iPP), in which the crystalline phase of iPP is only slightly influenced by the copolymer. X-ray results in the structural investigation of the blends correlate well with the mechanical properties of the blends.

Molecular mobility in epoxidized butadiene/styrene triblock copolymer

Abstract Solid state nuclear magnetic resonance was carried out by the continuous wave and pulse methods for butadiene/styrene (B/S) triblock copolymers containing various amounts of epoxy groups. The effects of epoxidation on the second-order phase transition and molecular motion were examined. It was found that, with an increase in epoxy unit content from 0 to 0.31 groups 100 g copolymer, the glass transition temperature, T g , in polybutadiene matrix increased from 201 to 264 K. The main minimum of the spin-lattice relaxation time was also shifted to higher temperatures. The activation energy determined from the slope of the low temperature curve T 1 = f( 1 T ) was found to be 1.7 times higher in epoxidized copolymer containing 0.25 mol epoxy groups 100 g than in pure B/S copolymer.

Some properties of polypropylene-butadiene/styrene radial block copolymer blends

Abstract Experimental studies of blends containing isotactic polypropylene and radial block butadiene-styrene copolymer over the whole composition range have been carried out. Measurements of viscosity and mechanical properties as well as electron microscopic observations of the system have shown that, up to about 5% copolymer content, both components are miscible and probably only a single-phase blend exists. Above this concentration, the copolymer forms a separate phase, i.e. a two-phase blend is formed.