Wyniki wyszukiwania - BazTech

1

Thermal and mechanical properties of PLA/ENR thermoplastic vulcanizates compatibilized with tetrafunctional double-decker silsesquioxanes

Paszkiewicz Sandra, Kramek Grzegorz, Walkowiak Konrad, Irska Izabela, Piesowicz Elżbieta, Rzonsowska Monika, Dudziec Beata, Barczewski Mateusz

Polimery

|

2023

|

Vol. 68, nr 11-12

593--606

EN

The influence of the addition of tetrafunctional double-decker silsesquioxanes (DDSQ-ether- -4OH) on the compatibility, thermal and mechanical properties of polylactide and epoxidized natural rubber (PLA/ENR) vulcanizates was investigated. The apparent cross-linking density and thermal stability of PLA/ENR vulcanizates were also determined. The FTIR analysis confirmed the compatibilizing effect of DDSQ-ether-4OH and the formation of the PLA-g-ENR copolymer. A strong effect of ENR content and DDSQ-ether-4OH addition on the thermal and mechanical properties of the obtained vulcanizates was demonstrated.

PL

Zbadano wpływ dodatku czterofunkcyjnego silseskwioksanu typu double-decker (DDSQ-eter-4OH) na kompatybilność oraz właściwości termiczne i mechaniczne wulkanizatów polilaktydu i epoksydowanego kauczuku naturalnego (PLA/ENR). Oznaczono również pozorną gęstość usieciowania i stabilność termiczną wulkanizatów PLA/ENR. Metodą FTIR potwierdzono kompatybilizujące działanie DDSQ-eter-4OH i utworzenie kopolimeru PLA-g-ENR. Wykazano silny wpływ zawartości ENR i dodatku DDSQ-eter-4OH na właściwości termiczne i mechaniczne otrzymanych wulkanizatów.

2

PLA filament is not equal to PLA filament: Experimental studies of the influence of the type of pigment on the mechanical and thermal properties of poly(lactic acid) products

Iwko Jacek, Jaruga Tomasz, Trzaska Oliwia, Stachowiak Tomasz

Materials Science Poland

|

2023

|

Vol. 41, No. 1

177-190

EN

The correct manufacture of products using FDM printers is not an easy task, taking into account the value and repeatability of material properties. The properties of elements manufactured in this way depend on many factors, both technological and material. Poly(lactic acid) PLA is one of the most willingly used materials in additive techniques. It is sold in a very wide range of colours. This work was intended to answer the question of how the type of pigment affects the mechanical and thermal properties of products obtained from PLA. The correlation between the material properties and the structure of the material as well as the macroscopic structure of the product has also been investigated. The paper analyses the mechanical and thermal properties of products made of PLA filaments in 12 basic colours obtained from one supplier. Bending, impact strength, HDT and Vicat softening point tests were carried out. The percentage content of residues after calcination the samples was determined. Additional analysis (DSC) was performed to interpret the obtained tests results. They indicate that the mechanical properties differ significantly between different types of PLA with differences of up to 45%. Vicat softening point tests indicate differences of 5°C between the extreme values of these parameters. The DSC interpretive study did not clearly show the reasons for these differences in the properties of the filaments.

3

Geometrical Accuracy and Strength of Micro-Needles Made of Polylactide by Fused Filament Fabrication Method

Wichniarek Radosław, Kuczko Wiesław, Tomczak Dorota, Nowicka Ariadna B., Wojtyłko Monika, Froelich Anna, Osmałek Tomasz

Advances in Science and Technology. Research Journal

|

2023

|

Vol. 17, no 6

116--126

EN

Additive manufacturing is a technology that can be successfully used in pharmacy and medicine. One of the examples of products that can be additively manufactured are microneedle systems. The specificity of these products, which are used for transdermal drug delivery, makes additive manufacturing a perfect choice for related research. However, the dimensions of microneedles usually do not exceed 2 mm, which means that manufacturing them using the most widely available additive manufacturing method, Fused Deposition Modelling (FDM), is problematic. In this study, the authors decided to investigate the possibilities of manufacturing microneedle systems using the FDM method in such a way as to minimize or exclude the need for post-processing. Five types of microneedle geometries were tested in four sizes, examining how changing the values of FDM process parameters would affect the accuracy of reproducing the digital geometry of the microneedles. From the point of view of the application of microneedle systems, it is not only necessary to obtain the designed shape of the microneedles, but also to maintain their appropriate strength. The study presents the results of the bending and compression strength of microneedles made of polylactic acid.

4

Study of the adhesion between TPU and PLA in multi-material 3D printing

Brancewicz-Steinmetz E., Valverde Vergara R., Buzalski V. H., Sawicki J.

Journal of Achievements in Materials and Manufacturing Engineering

|

2022

|

Vol. 115, nr 2

49--56

EN

Purpose: In the Fused Filament Fabrication (FFF/FDM) technology, the multi-material manufacturing additive method is achieved by a single nozzle or multiple nozzles working simultaneously with different materials. However, the adhesion between different materials at the boundary interface in FDM multi-material printing is a limiting factor. These studies are concerned with improving and study the adhesion between two polymers. Design/methodology/approach: Due to the numerous applications and possibilities of 3D printed objects, combining different materials has become a subject of interest. PLA is an alternative to the use of petrochemical-based polymers. Thermoplastic Polyurethane is a flexible material that can achieve different characteristics when combined with a rigid filament, such as PLA. To improve the adhesion between PLA and TPU in multi-material FFF/FDM, we propose the comparison of different processes: post-processing with acetone immersion, surface activation during printing with Acetone, surface activation during printing with tetrahydrofuran, post-processing annealing, and connection of printed parts with tetrahydrofuran. Findings: Modifying the 3D printing process improved the quality of the adhesive bond between the two different polymers. Activation of the surface with THF is the treatment method recommended by the authors due to the low impact on the deformation/degradation of the object. Research limitations/implications: In the study, adhesion was considered in relation to the circular pattern of surface development. Further analysis should include other surface development patterns and changes in printing parameters, e.g. process temperatures and layer application speed. Practical implications: 3D printing with multi-materials, such as PLA biopolymer and thermoplastic polyurethane, allows for the creation of flexible connections. The strengthening of the biopolymer broadens the possibilities of using polylactide. Examples of applications include: automotive (elements, where flexible TPU absorbs vibrations and protects PLA from cracking), medicine (prostheses with flexible elements ensuring mobility in the joints). Originality/value: Multi-material printing is a new trend in 3D printing research, and this research is aimed at promoting the use and expanding the possibilities of using PLA biopolymer.

5

Influence of the Structure of Low MolecularWeight Esters on Poly(lactic acid) in the Plasticization Process - part 1

Gzyra-Jagieła Karolina, Sulak Konrad, Draczyński Zbigniew, Madej Kiełbik Longina, Jagodzińska Sylwia, Borkowski Dominik

Fibres & Textiles in Eastern Europe

|

2022

|

Vol. 30, no. 3

93--101

EN

Polymers derived from renewable sources which are additionally subject to degradation processes are currently an interesting alternative to conventional polymers of petrochemical origin. One of such polymers is poly(lactic acid) (PLA), which can be used in the packaging, textile and also medical industries. Its great advantage is the susceptibility to biodegradation and the nontoxicity of the degradation products. Because of high brittleness and stiffness, the modification of PLA is necessary to improve its plastic deformability, which can expand the new application possibilities. As part of the research work, the modification of PLA by plasticisation was undertaken to improve its plastic deformability properties. The low molecular mass esters from the citrate group and glycerol triacetate were used. The samples extruded from plasticised polymer were characterised using Differential Scanning Calorimetry (DSC) and Gel Permeation Chromatography/Size Exclusion Chromatography (GPC/SEC). The mechanical properties and melt flow rate after modification were determined. The aim of the research was to determine the relationship between the structure of a plasticiser and its ability to reduce the interactions in the polymer chain in order to develop an optimal polymerplasticiser arrangement. Based on this research, there was no relationship between the efficiency of the plasticisation process and the increasing molecular mass of the plasticiser. The additional chemical (acetyl) group in the plasticiser also does not increase the efficiency of the PLA plasticisation process. In the next steps of the research, functional forms will be produced, i.e. fibers, films, and fittings from the selected polymer-plasticiser systems.

6

Time Distribution Analysis of 3D Prints with the Use of a Filament and Masked Stereolithography Resin 3D Printer

Paśnikowska-Łukaszuk Magdalena, Korulczyk Katarzyna, Kapłon Kamil, Urzędowski Arkadiusz, Wlazło-Ćwiklińska Magda

Advances in Science and Technology. Research Journal

|

2022

|

Vol. 16, no 5

242--249

EN

The article focuses on the subject of 3D printing. 3D printing technology and currently used solutions are described. The materials used in printing with the use of a filament printer and a resin printer are discussed. The fused deposiotion modeling technique and the LCD-based stereolithography. Printing technology were presented. Samples were prepared using 3D modeling software. The software used to make the models is discussed. The designed models were printed on two types of printers, using different model orientations. Printouts were measured several times. The obtained data was analyzed and the conclusions, proposed solutions and possible improvements to 3D printing were presented at the end. The article deals with the subject of the possibility of accelerating 3D prints due to their location, but also the influence of warming up the printer during subsequent prints was checked.

7

Experimental investigations on mechanical properties of walnut shell and pine needle ASH polylactic ACID biocomposites

Chaturvedi Adarsh, Ranakoti Lalit, Kumar Rakesh Pawan, Kumar Mishra Niraj

Composites Theory and Practice

|

2021

|

R. 21, nr 3

114--120

EN

Biocomposites consisting of polylactic acid reinforced with 2 to 8 wt.% walnut shell and pine needle ash fillers were fabricated by the microwave heating technique. The mechanical properties such as tensile strength, flexural strength, impact strength, Vickers hardness, and sliding wear behavior of the produced biocomposites were examined. The tensile strength declined by 11.62% with a reinforcement of 8 wt.% pine needle ash (PNA) in the PLA matrix as compared to the neat PLA matrix. The flexural strength also dropped by 3.09% with the reinforcement of 8 wt.% PNA in the PLA matrix compared to the neat PLA. It was found that the impact energy was enhanced by 77.27 and 66.67% with the reinforcement of 8 wt.% PNA and WN fillers in the PLA matrix, respectively. The Vickers hardness also improved by 14.54 and 10.35% with the reinforcement of 8 wt.% PNA and WN fillers in the PLA matrix, respectively. In addition, the weight loss due to sliding wear was improved by 95.86 and 94.52% with the reinforcement of 8 wt.% WN and PNA fillers in the PLA matrix as compared to the neat PLA matrix, respectively. The drilling forces (thrust force and torque) were additionally recorded during the drilling process of the PNA and WN filled PLA based biocomposites.

8

The composting of PLA/HNT biodegradable composites as an eco-approach to the sustainability

Czarnecka-Komorowska Dorota, Bryll Katarzyna, Kostecka Ewelina, Tomasik Malgorzata, Piesowicz Elżbieta, Gawdzińska Katarzyna

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2021

|

Vol. 69, nr 2

art. no. e136720

EN

The article presents the results of the research related to the decomposition of polylactic acid (PLA)/halloysite nanotube (HNTs) biocomposites into a simple organic form. After manufacturing the nanocomposites, the evaluation of the composting process simulation was conducted using the biodegradation method. First, the selected properties of PLA/HNTs biocomposites, such as density, water absorption, and impact strength were tested. Next, the impact of the composting process on the behavior of PLA/HNTs composites was investigated from 30 to 90 days. Finally, the loss of mass of the composites, hardness, and the structural changes of biocomposites under the composting conditions before and after the composting were evaluated using SEM microscopy. The results showed that the PLA modified by HNT particles has biodegradation-friendly properties and therein is fully suitable for organic recycling. Due to this, in the coming years, it may contribute to the replacement of non-biodegradability polymers, i.e. polyolefins and polyesters, and reduction of plastic packaging wastes.

9

Circular economy: comparative life cycle assessment of fossil polyethylene terephthalate (PET) and its recycled and bio-based counterparts

Rybaczewska-Błażejowska Magdalena, Mena-Nieto Angel

Management and Production Engineering Review

|

2020

|

Vol. 11, No. 4

121--128

EN

The transition to circular economy requires diversifying material sources, improving secondary raw materials management, including recycling, and finally finding sustainable alternative materials. Both recycled and bio-based plastics are often regarded as promising alternatives to conventional fossil-based plastics. Their broad application instead of fossilbased plastics is, however, frequently the subject of criticism because of offering limited environmental benefits. The study presents a comparative life cycle assessment (LCA) of fossil-based polyethylene terephthalate (PET) versus its recycled and bio-based counterparts. The system boundary covers the plastics manufacturing and end-of-life plastic management stages (cradle-to-cradle/grave variant). Based on the data and assumptions set out in the research, recycled PET (rPET) demonstrates the best environmental profile out of the evaluated plastics in all impact categories. The study contributes to circular economy in plastics by providing transparent and consistent knowledge on their environmental portfolio.

10

3D printed Polylactid Acid based porous scaffold for bone tissue engineering: an in vitro study

Bodnárová Simona, Gromošová Sylvia, Hudák Radovan, Rosocha Ján, Živčák Jozef, Plšíková Jana, Vojtko Marek, Tóth Teodor, Harvanová Denisa, Ižariková Gabriela, Danišovič Ľuboš

Acta of Bioengineering and Biomechanics

|

2019

|

Vol. 21, no. 4

101--110

EN

The objective of this study was to fabricate PLA-based porous scaffold by 3D printing technology and to evaluate their cytotoxicity and biocompatibility under in vitro conditions in respect to bone tissue engineering. Material and methods: Pure PLA in filamentous form was processed via 3D printing technology of fused filament fabrication into porous scaffolds. The structure and porosity of scaffolds were measured by metrotomography. PLA scaffolds were pre-treated by human serum, foetal bovine serum and complete cell culture medium to enhance bio-attractivity of the scaffold’s surface for the adherence of the cells. Cells were enzymatically isolated from the periosteum of the proximal tibia and then expanded in monolayer. Periosteum-derived osteoprogenitors (PDOs) were seeded on the pre-treated PLA scaffolds and subsequent cell proliferation was measured by commercially available cell proliferation assay. Adherence of PDOs on the PLA scaffold was confirmed by scanning electron microscopy (SEM). Results: Prepared scaffolds had well-defined structure and were characterized by uniform distribution of pores. They were non-toxic and biocompatible with PDOs, however, PLA scaffold with the periosteum-derived progenitor cells was significantly better in the group of scaffolds pre-treated with normal human serum. Conclusions: The obtained PLA porous scaffolds favored attachment of periosteum derived progenitors and proliferation, furthermore, cells penetrated into the scaffold through the interstitial pores which was meaningful for cytocompatibility evaluation.

11

PVP based materials: Biodegradation in different environments

Vanharova L., Julinova M., Slavik R.

Ecological Chemistry and Engineering. S

|

2017

|

Vol. 24, nr 2

299--309

EN

The research deals with biodegradation of films prepared from polyvinylpyrrolidone and polylactic acid (PVP/PLA). Biodegradation of PVP/PLA films was supported by the following additives: 1-methyl-2-pyrrolidone, 1-octyl-2-pyrrolidone, acrylamide and N-acetyl-L-phenylalanine according to the previous study. The films were prepared by a solvent casting technique. Biodegradation was observed using the respirometric method in different environments. The films subjected to biodegradation were analyzed by scanning electron microscopy and Fourier transform infrared spectroscopy. It was found that the films are substantially degraded, but not in the biological way; PVP was quickly removed in presence of water because of its easy solubility. In contrast, this fact could support biodegradation of PLA, which becomes more available for microorganisms when PVP leaves PLA matrix.

12

Foto-biodegradowalne kompozyty poli (kwasu L-mlekowego) i TiO2

Sobczyk-Guzenda A., Owczarek S., Kaczorowski R., Gazicki-Lipman M., Szymanowski H.

Engineering of Biomaterials

|

2014

|

Vol. 17, no. 128-129

46--49

PL

Wielofunkcyjne kompozyty składające się z polimerów oraz nieorganicznych nanododatków zmieniające pierwotne właściwości polimeru są uznawane za nowoczesne materiały, które można wykorzystać w wielu dziedzinach przemysłu oraz życia codziennego. Wpływ nanonapełniacza na modyfikację właściwości matrycy polimerowej zależy w dużym stopniu od kształtu i wielkości jego cząstek, cech powierzchniowych oraz co za tym idzie stopnia jego dyspersji. W przedstawionej pracy wytworzono kompozyty składające się ditlenku tytanu (IV) TiO2 oraz poli(kwasu mlekowego) (PLA). Użyto zarówno niemodyfikowany TiO2 oraz modyfikowany metodą RF PECVD (Radio Frequency Plasma Enhanced Chemical Vapour Deposition). Proces ten przeprowadzono przy dwóch przepływach metanu 15 i 30 sccm. W celu sprawdzenia efektywności modyfikacji wykonano badanie FTIR (Fourier Transform Infrared Spectroscopy). Badanie to potwierdziło obecność na powierzchni ziaren TiO2 grup -CH2 i -CH3. Gotowe kompozyty poddano badaniom właściwości mechanicznych takich jak statyczna próba na rozciąganie oraz pomiar udarności. Otrzymane wyniki dowiodły, że dodatek TiO2 zarówno modyfikowanego jak i niemodyfikowanego nie zmienia wytrzymałości na rozciąganie natomiast poprawia jego udarność. Obecność niemodyfikowanego TiO2 w matrycy PLA obniża nieco wartość kąta zwilżania gotowego kompozytu, a modyfikacja powierzchni TiO2 w plazmie metanowej prowadzi do zmniejszenia zwilżalności produktu końcowego.

EN

Multifunctional composites consisting of polymers or inorganic nanoadditions, which change the original properties of a polymer are considered to be modern materials for many industrial and daily life applications. An influence of a nanofiller on modification process of polymer matrix properties is strongly dependent on its particles shape and size, surface characteristics and in consequence its dispersion grade. In the present work composites consisting of titanium dioxide (IV) TiO2 and polylactic acid (PLA) were prepared. Unmodified TiO2 as well as modified one by RF PECVD (Radio Frequency Plasma Enhanced Chemical Vapour Deposition ) technique were used. Two different methane flow rates (15 and 30 sccm) were used during processes. In order to check the efficiency of modification process FTiR (Fourier Transform Infrared Spectroscopy) research was conducted. The results show that there are -CH2 and -CH3 groups present at the TiO2 grains surface. Mechanical properties like tensile testing and impact resistance of the composites were measured. The results prove that an addition of TiO2 (modified and unmodified) does not influence the tensile strength but improves impact resistance value. A presence of unmodified TiO2 in PLA matrix slightly reduces the water contact angle value for a composite. Methane plasma surface treatment leads to wetting properties reduction of a final product.

13

Kompozyty polilaktydu z napetniaczami pochodzenia roślinnego pozyskanymi z przemysłu rolno-spożywczego

Sałasińska K, Ryszkowska J

Przemysł Chemiczny

|

2013

|

T. 92, nr 11

2027-2031

PL

Metodą dwuetapową wykonano kompozyty o osnowie z polilaktydu (PLA) i napełniacza w postaci drobno mielonych łusek słonecznika oraz łupin pistacji, stanowiących odpady pozyskane z przemysłu rolno-spożywczego. Materiały wykazują zespół interesujących właściwości charakterystycznych dla kompozytów podatnych na biodegradację z napełniaczami roślinnymi (NFC). Uzyskano materiały o wyższej sztywności w porównaniu z nienapełnionym PLA, a w przypadku kompozytu ze słonecznikiem zaobserwowano również wzrost udarności. Twardość kompozytów podlegała nieznacznemu obniżeniu, natomiast istotnie zmniejszyła się ich wytrzymałość na rozciąganie i wydłużenie do zerwania.

EN

Polilactide matrix was reinforced with of finely ground sunflower husk and pistachios shell by 2-step injection moulding to produce biodegradable composite materials. The filling resulted in increasing d., Young modulus, storage modulus and H2O absorption and in decreasing tensile strength, hardness and elongation at break of the polylactide matrix. Its impact strength increased after addn. of sunflower husk meal but decreased after addn. of pistachios shell meal.

14

Effect of plasma treatment on the spreading of micro drops through polylactic acid (PLA) and polyester (PET) fabrics

Wardman R. H., Abdrabbo A.

Autex Research Journal

|

2010

|

Vol. 10, no. 1

1--7

EN

The effect of oxygen plasma treatment on two polyester fibre types, polylactic acid and standard polyester, and the influence on their respective wetting characteristics is investigated. A novel analytical system, based on image analysis, was developed for measuring the rate of spreading and dynamic movement of liquid over the fabrics. The techniques of X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM) were utilized to examine the nature of the surface modifications after the plasma treatment. The analyses showed that the oxygen plasma treatment abraded the surface of the PLA fibres, but did not alter their chemical nature, whilst the surfaces of the PET fibres were less abraded, but had enhanced polarity due to an increase in carbonyl groups. The increased surface abrasion made little difference to the wetting or wicking rates of water on PLA fibres, but the increased polarity made a large difference to the rates on PET fibres.

15

Experimental Study and Numerical Analysis for Prediction of the Fibre Diameter of Polylactic Acid (PLA) Spunbonded Nonwovens

Bo Z.

Fibres & Textiles in Eastern Europe

|

2009

|

Vol. 17, no. 5 (76)

82--86

EN

An air-drawing model of the polylactic acid (PLA) spunbonding process is presented and solved by introducing numerical computation results of the air jet flow field of an aerodynamic device. At the same time, the model is also verified by experimental results obtained with our university’s equipment. The influence of the density and specific heat capacity of polymer melt at a constant pressure changing with the polymer temperature on the fibre diameter was studied. The fibre diameters predicted is in good agreement with experimental data. The effects of processing parameters on the fibre diameter are further analysed. We find that a lower polymer throughput rate, a higher initial temperature of the melt ,a higher initial temperature, velocity, and suction speed of the air can all produce finer fibres, but during the incruse in the venturi gap, the fibre diameters first decrease and next increase again. The results encourage us to further investigate how fine a fibre diameter can be obtained in the spunbonding process and what factors influence the fibre diameter formed. Furthermore, the results also show the great perspective of this research in the field of the (CAD), of the spunbonding process and technology.

PL

Przedstawiono model wyciągania włókien z kwasu polimlekowego za pomocą powietrza w procesie produkcji włóknin metodą spun-bonded. Model ten został rozwiązany przez zastosowanie numerycznych obliczeń komputerowych biorąc pod uwagę warunki przepływu powietrza w dyszach areodynamicznych, jednocześnie model ten został zweryfikowany eksperymentalnie przy wykorzystaniu zaprojektowanego przez nas urządzenia. Badano wpływ gęstości i ciepła właściwego stopu polimeru przy stałym ciśnieniu, zależnych od temperatury polimeru na średnicę włókien. Przewidywana średnica włókien jest dobrze skorelowana z danymi eksperymentalnymi. Wpływ parametrów procesu na średnicę włókien był również analizowany. Stwierdzono, że niski wydatek polimeru, wyższa temperatura początkowa stopu jak również wyższa początkowa temperatura, początkowa prędkość i prędkość ssania powietrza powodują otrzymywanie cieńszych włókien. Stwierdzono również, że podczas wzrostu szczeliny dyszy średnica włókien początkowo zmniejsza się ale następnie ponownie wzrasta. Otrzymane wyniki obserwacji skłoniły autorów do dalszych badań dla określenia jak cienkie włókna można uzyskać w procesie spun-bonded i jakie inne czynniki wpływają na średnicę włókien. Przeprowadzone badania wskazują na duże możliwości wykorzystania ich przy komputerowo wspomaganym projektowaniu procesu spun-bonded.˙

16

Effect of simulated body fluid on the microstructure of melt spun composite fibers

Rajzer I., Rom M., Fabia J., Sarna E., Biniaś D., Zima A., Ślósarczyk A., Janicki J.

Engineering of Biomaterials

|

2009

|

Vol. 12, no. 88

2--4

EN

Polylactic acid (PLA) offers unique features of biodegradability and thermal processability, that offer potential applications in medicine. PLA can be transformed into fibers by spinning enabling then subsequent fabrication of desirable three dimensional fabrics which may be used as scaffolds for tissue engineering applications. Incorporation of synthetic nano-hydroxyapatite into the fibrous polymer matrix can enhance bioactive properties of the prospective scaffold. In the present work, the method of production of composite fibers based on polylactic acid (PLA) and nano-hydroxyapatite (n-HAp) is proposed. Obtained fibers have shown excellent apatite-forming ability when immersed in simulated body fluid.

17

Wpływ modyfikacji włókien naturalnych na właściwości kompozytów biodegradowalnych na osnowie PLA

Iwańczuk A., Kozłowski M., Frąckowiak S.

Czasopismo Techniczne. Mechanika

|

2009

|

R. 106, z. 1-M

119-123

PL

Przedmiotem niniejszej pracy było określenie wpływu modyfikacji włókien naturalnych na właściwości kompozytów poli(kwasu mlekowego) (PLA). W tym celu włókna lniane poddano merceryzacji bądź bieleniu. Wytworzono kompozyty na osnowie PLA zawierające 30%wag. włókien naturalnych. Przedstawiono rezultaty badań właściwości wytrzymałościowych, lepkości oraz wskaźnika prędkości płynięcia. We wnioskach stwierdzono, że modyfikacja włókien w znacznym stopniu przyczynia się do zwiększenia wytrzymałości kompozytu oraz do polepszenia adhezji międzyfazowej.

EN

Biodegradable materials have been developed mainly for packaging purposes and designed for composting after use. In this paper influence of natural fiber (flax) modification (boiling, bleaching) on the mechanical properties, melt viscosity and melt flow index have been presented for poly(lactic acid) composites. It has been shown that the modified fibers enhance the mechanical properties of PLA composites as well as the melt viscosity.

18

On the spontaneous condensation of selected hydroxy acids

Sajewicz M., Matlengiewicz M., Kronenbach D., Gontarska M., Kowalska T.

Acta Chromatographica

|

2009

|

Vol. 21, no. 2

259--271

EN

In a previous study we provided thin-layer chromatographic, polarimetric, and other experimental evidence that phenylglycine can undergo easy spontaneous peptidization in abiotic aqueous media. From our unpublished results it is apparent that this behaviour is also characteristic of some other amino acids (e.g., alanine and phenylalanine). It seems highly probable that this abiotic peptidization of amino acids dissolved in aqueous media is directly linked to their ability to undergo spontaneous oscillatory chiral conversion. In our earlier research it was also shown that spontaneous oscillatory chiral conversion was characteristic not only of amino acids but also of several other classes of carboxylic acid, including profen drugs and hydroxy acids. We therefore decided to check whether selected chiral hydroxy acids — lactic acid and mandelic acid — previously recognized for their ability to undergo spontaneous oscillatory chiral conversion, could also furnish the respective polyacids. Condensation of hydroxy acids can be viewed as a reaction fully analogous with peptidization of amino acids and, hence, it seemed to us highly probable that it also can be triggered by oscillatory chiral conversion. In our study, we used thin-layer chromatography and 13 C NMR spectroscopy to check whether formation of polylactic acid and polymandelic acid occurred in stored solutions of lactic and mandelic acids. By means of polarimetry with continuous recording we provided experimental evidence that all three hydroxy acids investigated (i.e. L -(+)-lactic acid, S -(+)-mandelic acid, and R -(−)-mandelic acid) undergo continuous chiral conversion. From the thin-layer chromatographic results obtained it was apparent that — similar to the spontaneous and instantaneous peptidization of amino acids — the hydroxy acids investigated also undergo easy condensation to form the respective polyacids. 13 C NMR spectroscopy provided additional experimental confirmation of this.