Birefringence in heat-mechanical modified freshly moulded polyester fibers Abstract. The article submits new experimental data concerning to the role of combined thermo-mechanical treatments on the structural development of freshly moulded uncrystallized but crystallizable poly (ethylene terephthalate) (PET) fibers. The object of the present work is PET as a thermoplastic polymer with a large practical application. The report is devoted to the influence of the heat-mechanical modification temperature on the structure rearrangement in uniaxially orientated amorphous PET. The heat-mechanical modification of the investigated yarns and the optical measurements were realized by specialized gears constructed and built in the author's laboratories. The fibers heat-mechanical modification includes samples annealing at constant temperature above their glass transition temperature (T g ) without strain stress. The yarn annealing has been followed from well defined uniaxially strain-loading with values from 0 MPa up to 30 MPa during two minutes. The optical measurements were carried out by an optical system using a polarization microscope and a CCD camera. The obtained experimental data has been analyzed by Mocha-1.2 (Jandel Scientific) software. There are established dependences between the heat-mechanical modification mode and the structural rearrangements running in the studied PET samples.

The possibilities for modifying the surface of phosphogypsum (CaSO 4 Á 2H 2 O) used as reinforcing material in polyethylene (PE) composites are investigated. The used method for surface modification of filler is the treatment with polyethylene glycol (PEG). The product has improved properties of compatibility with organic phase (polymer matrix). The use of PEG as modifier is described. The surface modified phosphogypsum and reinforcement materials have improved the properties including tensile strength. The optimum amount of PEG used for surface modification is 1-3%. These modified fillers and reinforcement materials may be used in a wide range of applications. The present study relates to a method for the surface modification of waste phosphogypsum and to their use in PE composites. The change in the surface characteristics of the filler influences also the properties of the composites in which they are used.

The fatty acid methyl esters (FAME) of triglycerides obtained by transesterification reaction in the presence of alkaline catalysts became a serious alternative of fossil fuels. In the present research FAME synthesized from five different in their chemical nature and composition vegetable oils were studied. The data for analysis and characterization of FAME was obtained using fourier transform infrared spectroscopy and then basic properties of biodiesel fuels were determined. The confirmation and validation of the results were proved by classical chemical methods of analysis. The ability for express analysis of biodiesel fuels by IR spectroscopy was confirmed and the achieved results are reliable basis for the biofuels stability research.

The spectra in middle IR-region of common polymers obtain different characteristic bands which can be analyzed for proper characterization and identification of single polymers in polymer mixture. In the present work the results of multilayer polymer films based on recycled high density polyethylene (HDPE) characterization are presented. The main technological problem in the secondary processing of HDPE is determination of the polymer degradation degree. The most suitable region in the IR-region is between 1850 – 1630 cm-1 , where the carbonyl group displays bands related to the oxidation processes of polyolefins. All IR-spectra have weak absorption in this region which proves the oxidation processes in macromolecular chains. The carbonyl index of the studied films is calculated too. It is proved that the recycling process of HDPE is insignificantly related to its stability, macromolecular characteristics and possibility for secondary processing. The results of present study show a perspective possibility for utilization of huge amounts of waste HDPE as main component in multilayer films with good characteristics, suitable for packaging purposes of foods.

The spectra in middle IR-region of common polymers obtain different characteristic bands which can be analyzed for proper characterization and identification of single polymers in polymer mixture. In the present work the results of multilayer polymer films based on recycled high density polyethylene (HDPE) characterization are presented. The main technological problem in the secondary processing of HDPE is determination of the polymer degradation degree. The most suitable region in the IR-region is between 1850 – 1630 cm-1, where the carbonyl group displays bands related to the oxidation processes of polyolefins. All IR-spectra have weak absorption in this region which proves the oxidation processes in macromolecular chains. The carbonyl index of the studied films is calculated too. It is proved that the recycling process of HDPE is insignificantly related to its stability, macromolecular characteristics and possibility for secondary processing. The results of present study show a perspective possibility for utilization of huge amounts of waste HDPE as main component in multilayer films with good characteristics, suitable for packaging purposes of foods.