Dušan Olčák

Characterisation of crumb rubber modifier using solid-state nuclear magnetic resonance spectroscopy

Crumb rubber (CR) can be used for binder modification or aggregate replacement in asphalt mixtures for road construction, when it is usually referred to as CR modifier (CRM). CRM elastic properties depend on the quality of parent material and storage conditions of final material. They deteriorate in time due to degradation processes and among other things they can influence CRM swelling capacity during asphalt rubber preparation. The presented paper demonstrates the sensitivity of basic nuclear magnetic resonance (NMR) parameters (proton spin-lattice relaxation time T1, proton spin–spin relaxation time T2 and the line broadening in 13C NMR and 1H NMR spectra) for detecting changes in CRM degradation. These NMR parameters are proposed to be used to assess CRM degradation before application in asphalt mixtures. In laboratory conditions, CRMs with different degrees of degradation were prepared by thermal ageing at 85°C for 0–36 days.

High-Resolution Solid-State NMR Characterization of Morphology in Annealed Polylactic Acid

Single-pulse 13C NMR spectra and spin-lattice relaxation times T1(1H), detected indirectly via 13C carbons, and T1(13C) were measured at 31°C for virgin pelletized and annealed polylactic acid (PLA) samples using the magic-angle spinning technique. The structural relaxation resulting in more regular crystals with narrower conformation distribution and increase in the lamellae thickness and crystallinity brought about by annealing at 100°C was deduced from the narrowing of the 13C NMR lines and proton spin-lattice relaxation times T1(1H). The spin-lattice relaxation times T1(13C) related to the respective carbons of the α-polymorph of PLA are also discussed in the study.

Characterization of native and plasticized starch using solid state NMR

The crystallinity of native starches influences numerous properties of starch-based materials and for this reason, its assessment is of great importance. It is known that the phase composition of native starch can be obtained by the decomposition of its 13C NMR spectrum into the sub-spectra of the ordered (crystalline and interfacial) and amorphous phases. The percentage of amorphous phase can be obtained from the intensity of C4 carbon resonance. The deconvolution of the C1 carbon resonance in the sub-spectrum of the ordered phase gives information on the ratio of crystalline and interfacial phases and the starch crystalline type, which is inferred from the presence of triplet (A-type) or doublet (B-type) of even intensities. Four native starches - soltex (wheat, A-type), amylex (potato, B-type) meritena and maisita (both corn A-type) were studied and as their amorphous counterparts the starches plasticized with urea were used. The 13C NMR spectra of the studied samples were recorded using the cross polarization (CP) and the magic angle spinning (MAS) techniques and using the decomposition of the spectra the phase compositions of native starches were obtained. In order to evaluate the mobility of different phases in native as well as plasticized samples the measurements of carbon spin-lattice relaxation times T1(13C) in laboratory frame were carried out. The T1(13C) values obtained fitting the bi-exponential function to the C1 carbon intensity decay and taking into account the calculated composition of the samples (ordered and disordered phases) show that A-type starches have close T1(13C) values which are shorter (16.6 – 20.8 s) for disordered phase and longer (53.9 – 80.1 s) for ordered phase proving different mobility of these phases. The B-type sample has lower T1(13C) values (1.7 s, 37.0 s) which are in line with less spatial constraints in its structure. The mono-exponential functions fitted to the data obtained for plasticized samples provided T1(13C) values in the interval (43.9–79.9 s) which could be explained by different molecular structure of native samples.The crystallinity of native starches influences numerous properties of starch-based materials and for this reason, its assessment is of great importance. It is known that the phase composition of native starch can be obtained by the decomposition of its 13C NMR spectrum into the sub-spectra of the ordered (crystalline and interfacial) and amorphous phases. The percentage of amorphous phase can be obtained from the intensity of C4 carbon resonance. The deconvolution of the C1 carbon resonance in the sub-spectrum of the ordered phase gives information on the ratio of crystalline and interfacial phases and the starch crystalline type, which is inferred from the presence of triplet (A-type) or doublet (B-type) of even intensities. Four native starches - soltex (wheat, A-type), amylex (potato, B-type) meritena and maisita (both corn A-type) were studied and as their amorphous counterparts the starches plasticized with urea were used. The 13C NMR spectra of the studied samples were recorded using the cross pola...

Problems with Solidification of Fly Ashes from the Municipal Solid Waste Incineration

One of the negative aspects of MSW (municipal solid waste) incineration is production of hazardous fly ashes. MSW fly ash usually contains heavy metals like for example chromium, lead, cadmium and organic substances (dioxins, furans), soluble compounds (salts) and other harmful substances. According to environmental legislative and with respect to the environment fly ash as a hazardous waste should be stabilized before landfilling. This work deals with certain problems occurring at solidification process of MSW fly ash by cementation. This work also describes efficiency of stabilization by two different binders (slag cement and waste containing alumina and silica). Leachability tests by TCLP (toxicity characteristic leaching procedure) and compressive strength of original and solidified samples by use of uniaxial pressing were studied in order to find suitable parameters for effective stabilization.