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Search results for: emerytowany profesor Uniwersytetu
Łódzkiego. Zajmuje się kulturą i recepcją literatury romantycznej; poeta-
mi dwudziestolecia międzywojennego Krystyna Ratajska – prof. dr hab.
Recently, we proposed a novel strategy for fabricating high-performance stereocomplex-type polylactide (SC-PLA) products through low-temperature (180–210 °C, lower than the melting temperature of SC crystallites) sintering from its nascent powder, without serious thermal degradation involved in the conventional melt processing at higher temperatures. During the sintering, some poly(l-lactide) (PLLA)...
Polylactide (PLA) particles become increasingly important for practical applications as typical sustainable polymeric materials; however, their preparation still remains as a big challenge due to lacking effective preparation method directly starting from monomer lactide (LA) and lactic acid. In this study, we established an unprecedented strategy for preparing PLA particles in a high yield (>90 wt%)...
The molecular dynamics of the constrained and unconstrained mobile amorphous fractions in semi-crystalline polylactide (PLA) was investigated in the presence of both flow-induced crystalline structures and spherulites by fast scanning calorimetry (FSC) through cooperativity and physical aging concepts. First, the shear rate conditions leading to flow-induced crystallization were characterized by examining...
Hydroxy-terminated 4-armed star-shaped ɛ-caprolactone and l-lactide oligomers (H4CLOn and H4LAOn) with a degree of polymerization per arm (n = 5, 10 or 15) were reacted with furfuryl isocyanate and (4-maleimidophenyl)isocyanate to produce furan- and maleimide-functionalized 4-armed star-shaped ɛ-caprolactone and l-lactide oligomers (F4CLOn and M4LAOn), respectively. The Diels-Alder (DA) reaction of...
Pyrolitic lignin was modified through two methods. First, it was grafted with polylactide chains via a solvent-free process by ring-opening polymerization of l-lactide using calcium hydride as a catalyst. The efficiency of grafting was determined by infra-red, nuclear magnetic resonance and time-of-flight secondary ion mass spectrometry analyses. Then, lignin particles were oxygen plasma-treated and...
Three-dimensional porous polylactide (PLA) scaffolds of almost fully interconnected pores were successfully prepared by extracting the poly(ε-caprolactone) (PCL) phase from co-continuous PCL/PLA blends. Quiescent annealing of the blends in supercritical CO2 (scCO2) prior to the PCL extraction, reported for the first time in this paper, allowed control over the average pore size from 50 to 150 μm of...
When poly(d-lactide) (PDLA) is mixed with poly(l-lactide) (PLLA) of similar molecular weight and crystallized from the melt in ultrathin films (30 nm), hexagonal single crystals are obtained at the equimolar composition, and triangular single crystals at non-equimolar compositions. Here, stereocomplexes are formed by blending PDLA with a PLLA incorporated as the central block of a triblock copolymer...
Stereocomplex mesophase is for the first time disclosed by annealing of 1:1 poly (l-lactide) (PLLA)/poly (d-lactide) (PDLA) blends just above glass transition temperature. Its structure is analogue to that of stereocomplex crystals, as a result of weak intermolecular interactions between PLLA and PDLA chains. In the limited temperature range formation of stereocomplex mesophase is enhanced with annealing...
In this study, attempts have been put to prepare toughened polylactide (PLA) through melt blending with acrylonitrile butadiene rubber (NBR) via melt mixing process. The influences of acrylonitrile (ACN) content on the compatibility, microstructure, tensile properties and impact resistance have been investigated. A matrix-dispersed droplet morphology was noted for all blend samples, and the rubber...
The presence of an ionic liquid in the plasticized polylactide (PLA) contributes to enhancement of dielectric permittivity due to its electrical conductivity. Phase separation, induced by thermal annealing and mechanical stretching, respectively, can further enhance dielectric permittivity. It offers opportunities to monitor phase separation in the ionic liquid plasticized PLA by dielectric spectroscopy...
As a popular bioplastic, poly (l-lactic acid) (PLLA) still faces some drawbacks mainly related to its low crystallization rate and heat distortion resistance. Herein, we demonstrate a facile and promising route to solve these problems by compositing PLLA with poly(d-lactide) grafted cellulose nanocrystal (CNC-g-PDLA) which can be synthesized via ring-opening polymerization of d-lactide on the CNC...
Semi-crystalline polylactide (PLA)/polyolefin multi-component blends were used as precursors for the generation of a new class of micro-cellular polymers. Either a polypropylene-based elastomer (PBE) or polypropylene (PP) homopolymer were utilized as dispersed phases at the 10 wt% level. An epoxy-functionalized terpolymer (PEGMMA) was introduced (1 wt%) as a reactive compatibilizer to reduce the dispersed...
This work focuses, for the first time, on the structural evolution of Polylactide (PLA) and PLA-Talc nanocomposites upon biaxial stretching. Biaxial stretching is a widely used technique to improve the end-use properties of polymer films. Encountered in a large number of elaboration processes it involves important structural changes into the material which directly govern the properties gain. In this...
This work focuses on the mechanical behavior and the associated structural evolution of Polylactides homopolymers blends, i.e. PLLA and PDLA blends, with the aim of determining the ability to form the sterecomplex crystalline form upon stretching. The investigations carried out on initially amorphous samples revealed that only the crystalline α′-form, i.e. the one encountered in the case of the homopolymers,...
Relatively high contents of rubber are commonly required to trigger the brittle-to-ductile transition when using rubber components to toughen polylactide (PLA). However, the strength may drop remarkably after incorporation of large amount of rubber. The main motivation of the present work is to achieve a good toughness-strength balance in a PLA/rubber system with less amount of rubber phase (90/10...
Linear and star-shaped polymers have been synthesized by the controlled ring-opening (ROP) polymerization of l- and d-lactide using 1-methyl-2-hydroxymethyl-3-butylimidazolium tetrafluoroborate and dipentaerythritol as initiators, respectively. To introduce carboxylic end-groups onto the star-shaped polylactides, the reaction of –OH end-groups with succinic anhydride was employed. Afterwards, the...
Ion gels have been obtained by crystallization of polylactide (PLA) in an ionic liquid. The modulus of the resulted ion gels is increased with PLA content in the ionic liquid, whereas ionic conductivity follows an opposite tendency. Isolated spheres, caused by PLA crystallization, are responsible for low modulus in the ion gels with low PLA content. By adding a nucleating agent isolated spheres are...
An intensification and integration process of preparing highly thermal stable polylactide was reported. Calcium complex 1 [LCaN(SiMe3)2]2 (L = 2,5-bis-((pyrrolidin-1-yl)methene)-1H-pyrrole) was employed to synthesize the alcoholic chain-transfer agent and catalyze the immortal ring-opening polymerization of l-lactide in one pot. 1H NMR spectrum and MALDI-TOF mass spectrum analyses indicated that the...
In this study, we report the development of polylactide (PLA) bead foams with a double crystal melting peak structure. PLA bead foams with 3- to 30-fold expansion ratios and average cell sizes ranged from 350 nm to 15 μm were prepared. We found that the PLA's foam structure was significantly affected by the amount of perfected crystals (that is, crystals with a high melting temperature) generated...
Bio-based polylactide/poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PLA/PHBV) blend fibers have been prepared via the conventional melt-spinning and hot-drawing process. The spinnability was optimized by determining the narrow temperature window for each blend via rheological studies. The blend fibers showed unexpectedly improved heat-resistance and softness along with acceptable tensile properties,...
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