Browsing by Author "Habr, Jiří"

Now showing 1 - 15 of 15
  • Thumbnail Image
    Item
    Dýchací maska se společným nádechovým a výdechovým otvorem - výrobní proces v poloprovozním režimu
    (Technická Univerzita v Liberci, 2014-01-01) Běhálek, Luboš; Bobek, Jiří; Habr, Jiří; Lenfeld, Petr; Seidl, Martin; Katedra strojírenské technologie - oddělení tváření plastů
    Tato zpráva se zabývá popisem výrobního procesu dýchací masky se společným nádechovým a výdechovým otvorem v poloprovozním režimu. Tato dýchací maska se skládá z pružné a tuhé části a je navržena pro dvě tvarové varianty vyměnitelných filtrů – kruhový a obdélníkový. Pružná část dýchací masky je současně navržena ve dvou materiálových variantách – silikon a termoplastický elastomer.
  • Thumbnail Image
    Item
    Effect of dielectric barrier discharge plasma surface treatment on the properties of pineapple leaf fiber reinforced poly(Lactic acid) Biocomposites
    (Trans Tech Publications Ltd, 2016-01-01) Borůvka, Martin; Ngaowthong, Chakaphan; Běhálek, Luboš; Habr, Jiří; Lenfeld, Petr
    Plant source-based stiff fiber reinforced bioplastics based on natural plant derived substances show promise of providing degradation back into the environment when they are no longer needed. These "green" composites have enormous potential to replace materials originated from non-renewable resources and may turn out to be one of the material revolutions of this century. Unlike synthetic composites, "green" composites are renewable, carbon neutral, biodegradable, nonpetroleum based, and have low environmental, human health and safety risks. In this paper effect of pineapple leaf fiber (PALF) length and physical surface treatment on to the properties of the composites was investigated at 10% wt. loading. In order to improve compatibility and composite properties of PALF/poly(lactic acid) composites without any hazardous chemicals that are usually involved in the process, dielectric barrier discharge (DBD) plasma surface treatment was conducted for fiber modification. Therefore more environmentally friendlier and industrially scalable technology was implemented in processing of composites by twin screw extrusion and injection moulding. Resulted composites were characterized by means of scanning electron microscopy (SEM), thermal and mechanical testing. © 2016 Trans Tech Publications, Switzerland.
  • Thumbnail Image
    Item
    Evaluation of Two-component Joint from Polymers for the Medical Applications
    (Technická Univerzita v Liberci, 2013-01-01) Habr, Jiří; Lenfeld, Petr; Běhálek, Luboš
    The paper deals with the evaluation of two-components joint at tested injected samples respectively both in the dependence on the selective combination of used polymers and thermoplastic elastomers and in the dependence on the selective two-component joint geometrical shape with respect to application possibilities. Polymers used for two-component joint are designed for health harmless applications.
  • Thumbnail Image
    Item
    Influence of different coupling agent type on processibility and applicability of polymer composites
    (Trans Tech Publications Ltd, 2016-01-01) Seidl, Martin; Habr, Jiří; Běhálek, Luboš; Šafka, Jiří; Ackermann, Michal; Bobek, Jiří
    The contribution deals with the processibility and applicability of polymer composite systems based on polypropylene matrix. The composites were filled with vegetable fibres (particularly the cotton fibres, coir fibres, hemp fibres and jute fibres) and the interface between the polymeric matrix and the natural fibres was modified using two types of coupling agents (the organosilane coupling agent and maleic anhydride grafted polypropylene). For evaluation of the final impact of all three phases presence on the processibility of the polymer composite the melt flow behaviour was analyzed (MFI analysis according to ISO 1133) for the filler concentration of 10, 20 and 30 wt. %. This study involves also the natural fibre surface profile analyses (based on SEM observation) and the applicability of created composite materials was determined using the heat deflection temperature (HDT analysis according to ISO 75). © 2016 Trans Tech Publications, Switzerland.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Monitorizace rozměrových změn vytlačovaného profilu
    (Technická Univerzita v Liberci, 2009-01-01) Habr, Jiří; Lenfeld, Petr
    The diploma work deals with the monitoring of extrusion parison dimensional changes by extrusion blowing technology by means of the machine GM 251. The aim of diploma work is described the influence of material and technological parameters on the growing of parison diameter.
  • Thumbnail Image
    Item
  • Thumbnail Image
    Item
    Prototyp – Dýchací maska se společným nádechovým a výdechovým otvorem
    (Technická univerzita v Liberci, 2014-01-01) Běhálek, Luboš; Bobek, Jiří; Habr, Jiří; Lenfeld, Petr; Seidl, Martin; Katedra strojírenské technologie - oddělení tváření plastů
    Tato výzkumná zpráva se zabývá návrhem konstrukce a výrobního postupu výroby prototypu ochranné dýchací polomasky s filtrační vložkou vyměnitelného kruhového a obdélníkového filtru.
  • Thumbnail Image
    Item
    Solid and microcellular polylactide nucleated with PLA stereocomplex and cellulose nanocrystals
    (SPRINGER, VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS, 2020-03-01) Borůvka, Martin; Běhálek, Luboš; Lenfeld, Petr; Brdlík, Pavel; Habr, Jiří; Wongmanee, Sorasak; Bobek, Jiří; Pechočiaková, Miroslava
    Blending polylactide (PLA) with poly(d-lactide) (PDLA) and cellulose nanocrystals (CNC)-based stereocomplex (SC) nanohybrids presents practical approach to produce fully biobased blends and nanocomposites with enhanced properties. This paper investigated the nucleation effect of PLA/PDLA and PLA/PDLA-g-MAH/CNC nanohybrids at low loading levels on the non-isothermal crystallization, morphology, as well as thermal and thermo-mechanical properties of PLA-based samples. Neat PLA, blends and nanocomposites were produced by conventional and microcellular injection molding. Nitrogen (N-2) in a supercritical state was used as the physical blowing agent for preparation of microcellular samples. CNC-based SC showed superior nucleating efficiency compared to SC nucleating agents. However, low mold temperature resulted in relatively low degree of crystallinity (similar to 15%). In addition, decrease in cell size and increase in cell density of microcellular samples have been observed after introduction of both nucleating agents. Slight increase in mechanical properties of nucleated samples compared to neat PLA has been ascribed to the higher degree of crystallinity. Despite these, decrease in all mechanical properties of microcellular samples has been noticed when compared to solid counterparts. Furthermore, dynamic mechanical analysis (DMA) reveals subsequent foaming and dramatic decrease in dimensional stability of microcellular samples above glass transition temperature (T-g). The storage modulus in a glassy region has been improved in both solid blends and nanocomposites. In addition, shift of T-g due to restricted chain mobility of PLA due to retarded relaxation of amorphous regions due to SC interactions has been observed.
  • Thumbnail Image
    Item
    Thermal degradation of the thermoplastic Elastomers during the injection Moulding process
    (Trans Tech Publications Ltd, 2016-01-01) Běhálek, Luboš; Habr, Jiří; Seidl, Martin; Lenfeld, Petr; Borůvka, Martin
    The thermal degradation of the thermoplastic elastomers (TPEs) during the injection moulding process – depending on the melt temperature and residence time of the processed material within the barrel of the injection unit, was studied on the basis of oxidation induction time evaluation (isothermal OIT) of the moulded parts (according to ISO 11357-6) and their physical and mechanical properties, according to ISO 1183-1, ISO 37 and ISO 7619-1. TPEs with different chemical compositions intended for automotive, industrial and medical applications were analysed during the study of the thermal degradation process. © 2016 Trans Tech Publications, Switzerland.
  • Thumbnail Image
    Item
    Thermal properties and non-isothermal crystallization kinetics of biocomposites based on poly(lactic acid), rice husks and cellulose fibres
    (SPRINGER, VAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDS, 2020-06-01) Běhálek, Luboš; Borůvka, Martin; Brdlík, Pavel; Habr, Jiří; Lenfeld, Petr; Kroisová, Dora; Veselka, Filip; Novák, Jan
    Bioplastics reinforced by agricultural waste fibres show promise to provide degradation back into the environment when they are no longer needed. These biocomposites have the potential to replace synthetic polymers from non-renewable resources in some applications and may turn out to be one of the material revolutions of this century. Unlike synthetic composites, biocomposites are renewable, carbon neutral, biodegradable and non-petroleum based and have low environmental, human health and safety risks. In this paper, poly(lactic acid) (PLA)-based biocomposites filled with technical cellulose fibres (CeF) and rice husks (RHs) at 10-30 mass% loading were prepared by twin-screw extrusion and injection moulding to enhance stiffness of resulting biocomposites. Particular attention was given to the enhancement of adhesion between the polymer matrix and natural filler through the physical modification by ozone (O-3) and dielectric barrier discharge (DBD) plasma (p) surface treatments. Further than, compatibilizing agent based on PLA-g-MAH was produced and introduced into the PLA systems. The non-isothermal crystallization behaviour and thermal properties were investigated through differential scanning calorimetry (DSC) under various cooling rates (5, 10, 20 and 40 degrees C min(-1)). The addition of both fillers increased overall crystallization kinetics of resulted biocomposites, especially at high cooling rates. An increase in crystallinity degree from 2.4 (neat PLA) up to 51% has been observed for PLA/30CeF(O3)samples at 40 degrees C min(-1)cooling rate. An increase in crystallinity degree based on mass percentage of filler was noticed especially for PLA/RH. Mass percentage increase in CeF did not notice significant increase in PLA crystallinity. The influence of RH and CeF on transformation behaviours of PLA alpha MODIFIER LETTER PRIME-/alpha-polymorphs was observed. The elimination of imperfect alpha MODIFIER LETTER PRIME-crystals was observed with increasing amount of RH and CeF.
  • Thumbnail Image
    Item
    Use of composite materials for FDM 3D print technology
    (Trans Tech Publications Ltd, 2016-01-01) Šafka, Jiří; Ackermann, Michal; Bobek, Jiří; Seidl, Martin; Habr, Jiří; Běhálek, Luboš
    This article deals with specific polymer composites modified for the Fused Deposition Modeling (FDM) which is a 3D print technology. These two phase systems involve thermoplastic matrix filled with natural fibres. The crucial demand of this progressive technology is put on the accuracy of the semi-product formed into the filament shape. To reach the smooth production of 3D prototypes the filament should have a constant diameter. In the article, individual steps of the polymer composite pelletization and following pre-processing and processing activities are described. Among these steps the extrusion of the filaments belongs and subsequent print test on “RepRap” device accompanied by optimization of building parameters. Tensile specimens were chosen for print with regard to maps mechanical properties of this newly developed material which was the final stage of this work. Tensile test curves were then compared with those graphs which can be found for the material produced by conventional technologies such as injection moulding. © 2016 Trans Tech Publications, Switzerland.
  • Thumbnail Image
    Item
    Výzkum technologie přípravy a zpracování kompozitů s PLA matricí a vlákny rostlinného původu
    (Technická Univerzita v Liberci, 2016-01-01) Habr, Jiří
    Thesis deals with the phenomenon of production and processing biocomposites having absolutely plant origin. The aim of this thesis is research of the technologies for preparation and processing biocomposites which are on the basis of the fully biodegradable PLA matrix with chosen plant fibers and to carry out measurements of their mechanical properties, melt mass-flow rate and evaluation of their processability. Subsequently (on the basis of such results) there is necessity to perform selection of the proper fiber type for production biocomposites without necessary to use any chemical additives for improving interphase adhesion on the matrix-fiber boundary. As a partial aim of this theses there is effort to test possibilities for utilization low-temperature plasma atmospheric dielectric barrier discharge (DBD) as well as fibers surface physical treatments to improve interphase adhesion. This treatment is maximally environmentally friendly treatment which perfectly matches with the philosophy of the fully biocomposite materials. As an integral part of this thesis there is also mapping of the technological complications accompanying compounding and injection of biocomposites having PLA matrix and plant fibers. Moreover, there i salso effort to determinate supposed causes and to propose possibilities for their elimination while keeping maximal quality of the biocomposite.
  • Thumbnail Image
    Item
    Výzkum technologie přípravy a zpracování kompozitů s PLA matricí a vlákny rostlinného původu
    (Technická Univerzita v Liberci, 2016-01-01) Habr, Jiří