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Liquid heat capacity of an amorphous poly(lactic acid)

Skotnicki Marcin, Czerniecka-Kubicka Anna, Zarzyka Iwona, Pyda Marek

Polimery

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2024

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Vol. 69, nr 5

238--291

EN

The experimental and computed liquid heat capacity of an amorphous PLA was presented. The liquid heat capacity of PLA above the glass transition 333 K (60°C) is linked to the molecular motions and computed as the sum of vibrational, external (anharmonic), and conformational contributions. The largest contribution to the liquid heat capacity, Cp(liquid) of PLA comes from the vibrational motions calculated as the group and skeletal vibrational heat capacity. The external contribution to Cp(liquid) was calculated as a function of temperature from experimental data of the thermal compressibility and expansivity of the liquid state. The contribution of conformational heat capacity to the total heat capacity of an amorphous liquid PLA was calculated by fitting the experimental liquid heat capacity, after subtracting the vibrational and external parts, to the obtained heat capacity based on a one-dimensional Ising-type model with two discrete states. The parameters described in these states can characterise the macromolecule’s stiffness, cooperativity, and degeneracy. The computed and experimental data of Cp(liquid) showed good agreement at the investigated temperature region.

PL

W pracy przedstawiono eksperymentalna i obliczoną pojemność cieplną ciekłego amorficznego PLA. Pojemność cieplna cieczy PLA powyżej temperatury przejścia szklistego 333 K (60°C) jest powiązana z ruchami molekularnymi i została obliczona jako suma składników wibracyjnych, zewnętrznych (nieharmonicznych) i konformacyjnych. Największy wkład w pojemność cieplną cieczy, Cp(liquid) PLA, pochodzi z ruchów wibracyjnych, obliczonych jako pojemność cieplna wibracji grupowych i szkieletowych. Zewnętrzny wkład do Cp(liquid) został obliczony jako funkcja temperatury na podstawie danych eksperymentalnych z użyciem parametrów ściśliwości i rozszerzalności cieplnej cieczy. Wkład konformacyjnej pojemności cieplnej do całkowitej pojemności cieplnej amorficznego ciekłego PLA został obliczony przez dopasowanie eksperymentalnej pojemności cieplnej cieczy, po odjęciu części wibracyjnych i zewnętrznych, do otrzymanej pojemności cieplnej opartej na jednowymiarowym modelu typu Ising z dwoma dyskretnymi stanami. Parametry opisane w tych stanach mogą charakteryzować sztywność, kooperatywność i degenerację makrocząsteczki. Obliczone dane Cp(liquid) wykazały zgodność z danymi eksperymentalnymi w badanym zakresie temperatury.

2

Thermally stable biopolymer composites based on poly(3-hydroxybutyrate) modified with linear aliphatic polyurethanes– preparation and properties

Zarzyka Iwona, Czerniecka-Kubicka Anna, Hęclik Karol, Dobrowolski Lucjan, Pyda Marek, Leś Karolina, Walczak Małgorzata, Białkowska Anita, Bakar Mohamed

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 2

91--105

EN

Purpose: Poly(3-hydroxybutyrate) (P3HB) is a biopolymer, but storing products from P3HB causes the deterioration of their properties leading to their brittleness. P3HB has also low thermal stability. Its melting point almost equals its degradation temperature. To obtain biodegradable and biocompatible materials characterized by higher thermal stability and better strength parameters than the unfilled P3HB, composites with the addition of polyurethanes were produced. Methods: The morphology, thermal, and mechanical property parameters of the biocomposites were examined using scanning electron microscopy, thermogravimetric analysis, standard differential scanning calorimetry, and typical strength machines. Results: Aliphatic polyurethanes, obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycols, were used as modifiers. To check the influence of the glycol molar mass on the properties of the biocomposites, glycols with a molecular weight of 400 and 1000 g/mol were used. New biocomposites based on P3HB were produced with 5, 10, 15, and 20 wt. % content of polyurethane by direct mixing using a twin-screw extruder. The following property parameters of the prepared biocomposites were tested: degradation temperature, glass transition temperature, tensile strength, impact strength, and Brinell hardness. Conclusions: Improvement of the processing property parameters of P3HB-biocomposites with the addition of aliphatic polyurethanes was achieved by increasing the degradation temperature in relation to the degradation temperature of the unfilled P3HB by over 30 C. The performance property parameters have also been improved by reducing the brittleness compared to the P3HB, as evidenced by the increase in impact strength and the decrease in hardness with an increase in the amount of polyurethane obtained by the reaction of 1,6-hexamethylene diisocyanate and polyethylene glycol with a molecular weight of 400 g/mol (PU400) as modifier.

3

Physical aging of polylactide-valsartan system investigated by differential scanning calorimetry

Drogoń Agata, Skotnicki Marcin, Pyda Marek

Polimery

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2020

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T. 65, nr 7-8

533--541

EN

The polylactide-valsartan systems with a mass ratio of 20 : 80, 50 : 50 and 80 : 20 were obtained and characterized by standard Differential Scanning Calorimetry (DSC). The isothermal physical aging process of polylactide-valsartan with a mass ratio of 50 : 50 was investigated at the aging temperature of 50°C and 70°C for different aging times. The enthalpy of relaxation values for each of the aging times and for all investigated components were determined experimentally and fitted to the Kohlrausch-Williams-Watts equation.

PL

Otrzymane układy polilaktydu z walsartanem w stosunkach masowych 20 : 80, 50 : 50 i 80 : 20 poddano analizie metodą różnicowej kalorymetrii skaningowej (DSC). Scharakteryzowano proces starzenia fizycznego mieszaniny polilaktyd-walsartan w stosunku masowym 50 : 50, prowadzony w temperaturze 50 i 70°C w różnym czasie. Z pomiarów doświadczalnych dla każdego czasu starzenia wyznaczono entalpię relaksacji, a następnie dopasowano otrzymane wielkości do równania Kohlrauscha-Williamsa-Wattsa.

4

Hybrid nanobiocomposites based on poly(3-hydroxybutyrate) : characterization, thermal and mechanical properties

Zarzycka Iwona, Czerniecka-Kubicka Anna, Szyszkowska Agnieszka, Pyda Marek, Frącz Wiesław, Byczyński Łukasz, Sedlarik Vladimir

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 1

97--110

EN

Poly(3-hydroxybutyrate) is a biopolymer used to production of implants in the human body. On the other hand, the physical and mechanical properties of poly(3-hydroxybutyrate) are compared to the properties of isotactic polypropylene what makes poly(3-hydroxybutyrate) possible substitute for polypropylene. Unfortunately, the melting point of poly(3-hydroxybutyrate) is almost equal to its degradation temperature what gives very narrow window of its processing conditions. Therefore, numerous attempts are being made to improve the poly(3-hydroxybutyrate) properties. In the present work, hybrid nanobiocomposites based on poly(3-hydroxybutyrate) as a matrix with the use of organic nanoclay – Cloisite 30B and linear polyurethane as a second filler have been manufactured. The linear polyurethane was based on diphenylmethane 4,4′-diisocyanate and diol with imidazoquinazoline rings. The obtained nanobiocomposites were characterized by X-ray diffraction, scanning and transmission electron microscopies, thermogravimetry, differential scanning calorimetry and their selected mechanical properties were tested. The resulting hybrid nanobiocomposites have intercalated/exfoliated structure. The nanobiocomposites are characterized by a higher thermal stability and a wider range of processing temperatures compared to the unfilled matrix. The plasticizing influence of nanofillers was also observed. In addition, the mechanical properties of the discussed nanobiocomposites were examined and compared to those of the unfilled poly(3-hydroxybutyrate). The new-obtained nanobiocomposites based on poly(3-hydroxybutyrate) containing 1% Cloisite 30B and 5 wt. % of the linear of polyurethane characterized the highest improvement of processing conditions. They have the biggest difference between the temperature of degradation and the onset melting temperature, about 100 °C.

5

Badanie procesu fizycznego starzenia amorficznego polilaktydu metodą różnicowej kalorymetrii skaningowej

Drogoń Agata, Pyda Marek

Polimery

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2019

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T. 64, nr 2

127--134

PL

Za pomocą różnicowej kalorymetrii skaningowej (DSC) zbadano proces fizycznego starzenia amorficznego polilaktydu. Przeprowadzono starzenie próbek polilaktydu o różnej zawartości izomeru D w łańcuchu: 8,1 i 16,4 %. Na podstawie wyników badań DSC oszacowano temperaturę zeszklenia, temperaturę fikcyjną relaksacji oraz entalpię relaksacji polilaktydu dla różnych czasów starzenia w temperaturze 40 °C i 50 °C. Stwierdzono, że wartość entalpii relaksacji zwiększa się ze wzrostem zarówno czasu, jak i temperatury starzenia. Doświadczalne wartości entalpii relaksacji w funkcji czasu starzenia dopasowano do równania Kohlrauscha-Williamsa-Wattsa (KWW).

EN

The process of physical aging of amorphous poly(lactic acid) was investigated using differential scanning calorimetry (DSC). The aging experiments of two types of amorphous polylactide with 8.1 % and 16.4 % content of D-isomer in the polymer chain were performed. Based on the DSC results, glass transition temperature, fictive temperature and enthalpy relaxation of unaged and aged polylactide were estimated for various aging times at 40 and 50 °C. It was found that the enthalpy relaxation is increasing with aging time and temperature. The experimental values of enthalpy relaxation as a function of aging time were fitted to the Kohlrausch-Williams-Watts (KWW) equation.