Vliv přidaných aditiv a technologických podmínek přípravy na krystalizaci symetrické směsi PLLA/PDLA biopolymerů
Loading...
Date
2021-06-22
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Tato diplomová práce se zabývá studiem fyzikálních a mechanických vlastností biopolymerů kyseliny poly(L-mléčné) (PLLA) a stereokomplexu kyseliny polymléčné (scPLA). Tyto materiálové systémy byly modifikovány vybranými nukleačními aditivy: nanokrystaly celulózy (CNC); stereokomplexem PLA; N,N´-Ethylen bistearamidem (EB); kyselinou orotovou (OA) a itakovou (IA). Zkoumán je také technologický vliv přípravy vzorků prostřednictvím vstřikování do studené (45 °C) a vyhřívané formy (100 °C). Práce je rozdělena na dvě části, a to na teoretickou a experimentální. Teoretická část je zaměřena na biopolymery, kyselinu polymléčnou, její stereokomplexaci a nukleační činidla. Experimentální část je dělena na úvodní experiment a hlavní experiment. Z výsledků měření termických vlastností v úvodním experimentu byly vyselektovány nejúčinnější nukleační aditiva a jejich hmotnostní poměr. Hlavní experiment popisuje výrobu zkušebních těles, mikroskopické studium struktury polymerů, tahové a rázové vlastnosti, teplotu měknutí Vicata, dynamo-mechanické vlastnosti a diferenční snímací kalorimetrii. Výsledky jsou hodnoceny v závislosti na procentuálním přídavku nukleačních aditiv a technologickém hledisku přípravy. Výsledná morfologie a stupeň krystalinity materiálových systémů na bázi PLLA s 0,5 % EB vedla k výraznému navýšení teplotní a rázové odolnosti při vstřikování vzorků do teplé formy. Nukleační účinek 3 % OA směřoval jak u PLLA, tak u stereokomplexu k výraznému navýšení stupně krystalinity. U druhého jmenovaného pak bylo dosaženo výrazného potlačení homokrystalické fáze a selektivní tvorby stereokomplexní struktury. Přestože tento systém nevykazoval tak dobré mechanické vlastnosti, díky nukleaci byla zajištěna struktura s vyšší teplotní stabilitou i nad 100 °C. Tam, kde nemodifikované PLLA zcela ztratilo teplotní stabilitu, byl naměřen elastický modul pružnosti v ohybu u vzorků scPLA s 3 % OA o hodnotě 850 MPa.
This Master's thesis deals with research of physical and mechanical properties of biopolymers of poly(L-lactic acid) (PLLA) and stereocomplex of polylactic acid (scPLA). These material systems were modified with selected nucleation additives: cellulose nanocrystals (CNC); stereocomplex PLA; N,N´-Ethylenebis(stearamide) (EB); orotic acid (OA) and itaconic acid (IA). The technological influence of samples preparation by injection into cold (45 °C) and heated molds (100 °C) is also analysed. The thesis is divided into two parts - theoretical and experimental. The theoretical part is focused on biopolymers, polylactic acid, its stereocomplexation and nucleating agents. The experimental part is divided into an introductory and main experiment. The most effective nucleation additives and their weight ratio were selected from the results of measuring thermic properties in the initial experimentation. The main experiment describes the production of testing specimens, microscopic study of the structure of polymers, tensile and impact properties, Vicata softening temperature, dynamo-mechanical properties and differential scanning calorimetry. The results are evaluated according to the percentage addition of nucleating additives and technological aspects of preparation. The resulting morphology and degree of crystallinity of PLLA - based material systems with 0,5 % EB led to a significant increase in temperature and impact resistance when samples were injected into a heated mold. The nucleation effect of 3 % OA led to a significant increase in the degree of crystallinity in both PLLA and stereocomplex. In the latter, considerable suppression of the homocrystalline phase and selective formation of a stereocomplex structure were accomplished. Even though this system did not prove such good mechanical properties, a structure with higher temperature stability even above 100 °C was ensured due to the nucleation. Where unmodified PLLA completely lost thermal stability, the storage modulus of scPLA samples with 3 % OA of 850 MPa was measured.
This Master's thesis deals with research of physical and mechanical properties of biopolymers of poly(L-lactic acid) (PLLA) and stereocomplex of polylactic acid (scPLA). These material systems were modified with selected nucleation additives: cellulose nanocrystals (CNC); stereocomplex PLA; N,N´-Ethylenebis(stearamide) (EB); orotic acid (OA) and itaconic acid (IA). The technological influence of samples preparation by injection into cold (45 °C) and heated molds (100 °C) is also analysed. The thesis is divided into two parts - theoretical and experimental. The theoretical part is focused on biopolymers, polylactic acid, its stereocomplexation and nucleating agents. The experimental part is divided into an introductory and main experiment. The most effective nucleation additives and their weight ratio were selected from the results of measuring thermic properties in the initial experimentation. The main experiment describes the production of testing specimens, microscopic study of the structure of polymers, tensile and impact properties, Vicata softening temperature, dynamo-mechanical properties and differential scanning calorimetry. The results are evaluated according to the percentage addition of nucleating additives and technological aspects of preparation. The resulting morphology and degree of crystallinity of PLLA - based material systems with 0,5 % EB led to a significant increase in temperature and impact resistance when samples were injected into a heated mold. The nucleation effect of 3 % OA led to a significant increase in the degree of crystallinity in both PLLA and stereocomplex. In the latter, considerable suppression of the homocrystalline phase and selective formation of a stereocomplex structure were accomplished. Even though this system did not prove such good mechanical properties, a structure with higher temperature stability even above 100 °C was ensured due to the nucleation. Where unmodified PLLA completely lost thermal stability, the storage modulus of scPLA samples with 3 % OA of 850 MPa was measured.
Description
Subject(s)
biopolymery, kyselina polymléčná, stereokomplexace, nukleační aditiva, biopolymers, poly(lactic acid), stereocomplex, nucleation additives