Deformation and structure evolution of glassy poly(lactic acid) below the glass transition temperature

CrystEngComm ◽  
2015 ◽  
Vol 17 (30) ◽  
pp. 5651-5663 ◽  
Author(s):  
Chengbo Zhou ◽  
Hongfei Li ◽  
Yao Zhang ◽  
Feifei Xue ◽  
Shaoyong Huang ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Structure Evolution ◽  
Poly Lactic Acid

The mesocrystal was found to form from the mesophase of glassy PLA stretched below the glass transition temperature.

scholarly journals Thermal and Dynamic Mechanical Analyses of Poly(Lactic Acid)/Poly(Ethylene Glycol) Blends

2018 ◽  
Vol 1 (1) ◽  
pp. 526-535
Author(s):  
Benaniba Mohamed Tahar ◽  
Aouachria Kamira
Keyword(s):  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Ethylene Glycol ◽  
Poly Lactic Acid ◽  
Poly Ethylene Glycol ◽  
Scanning Calorimetry ◽  
Dynamic Mechanical ◽  
Poly Ethylene

Blends of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) with various contents (0, 5, 10, 15, 20 and 30 weight %) and with different molecular weights (M¯w = 1000, 4000 and 6000 g/mol), called respectively PEG1, PEG2, and PEG3 were prepared by melt blending. Since glass transition temperature (Tg), T? and loss factor (tan ?) are relevant indicators of polymer chain mobility, plasticization has been studied by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). Low molecular weight (LMW) PEG enable increased miscibility with PLA and more efficient reduction of glass transition temperature (Tg) for concentrations of PEG less than 20%. This effect is not only enhanced by the LMW but also by increasing its content up to 20%. As expected, both T? and Tg decrease when increasing PEG molar mass and content up to 20%, which demonstrates the effectiveness of PEG to act as a plasticizer of PLA.

scholarly journals Biocomposites based on poly(lactic acid) and kenaf fibers: Effect of micro-fibrillated cellulose

2013 ◽  
Vol 32 (1) ◽  
pp. 331 ◽  
Author(s):  
Gordana Bogoeva-Gaceva ◽  
Dimko Dimeski ◽  
Vineta Srebrenkoska
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Flexural Strength ◽  
Microfibrillated Cellulose ◽  
Poly Lactic Acid ◽  
Kenaf Fiber ◽  
Kenaf Fibers

In this work, the influence of microfibrillated cellulose (MFC) on the basic mechanical properties of PLA/kenaf fiber biocomposites has been studied. The addition of 5–15 % microfibrillated cellulose to a biocomposite premix has resulted in an increased glass transition temperature of the final product, produced by compression molding of previously melt-mixed composite components. The presence of MFC has influenced the interface-sensitive properties of the PLA/kenaf composite: at an optimal loading of 10 %, the interfacial energy release rate was increased by about 20 %. Moreover, flexural strength and modulus of the composites were also improved (from 34.8 MPa to 57.1 MPa and from 4.9 GPa to 5.8 GPa, respectively).   

scholarly journals Este trabajo se centró en el desarrollo de envases activos biodegradables con mezclas de poli (ácido láctico) (PLA), poli (etileno-co-acetato de vinilo) (EVA), polietilenglicol (PEG) y quitosano (QUI). Se investigaron las características morfológicas térmicas y mecánicas de las mezclas, así como, al mismo tiempo, la actividad antifúngica del envase. Para evaluar la actividad antimicrobiana de las mezclas PLA/EVA/PEG/QUI, las muestras se insertaron entre rebanadas de pan sin conservantes para evaluar su vida útil. Al comparar entre PLA/EVA/PEG, mezclas de PLA/EVA/PEG/QUI y PLA puro fue posible evidenciar la miscibilidad parcial, la disminución de la temperatura de transición vítrea (Tg) al incorporar PEG en las mezclas, una disminución de la fuerza fl exural del 71% y módulo de elasticidad del 80,4% a la mezcla PLA/ EVA/PEG/2.5QUI, así como un aumento del alargamiento a la rotura del 153% y del 392% a la tenacidad al impacto. Se observó un comportamiento similar a PLA/EVA/20PEG y PLA/EVA/PEG/5.0QUI. La película que contiene QUI entre las rebanadas de pan también influyó en la reducción de la actividad del agua y redujo aproximadamente un 35% en el recuento de mohos y levaduras en las rebanadas de pan. El quitosano en mezclas con PLA/EVA/PEG mostró potencial como agente antifúngico natural en envases de panadería.  

2021 ◽  
Vol 10 (9) ◽  
pp. e50010916964
Author(s):  
Leticia Riboldi Cavalli ◽  
Jalma Maria Klein ◽  
Ivana Greice Sandri ◽  
Rosmary Brandalise
Keyword(s):  
Antimicrobial Activity ◽  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Elasticity Modulus ◽  
Morphological Characteristics ◽  
Poly Lactic Acid ◽  
Elongation At Break ◽  
Poly Ethylene

This work focused on the development of biodegradable active packaging with poly(lactic acid) (PLA), poly(ethylene-co-vinyl acetate) (EVA), polyethylene glycol (PEG) and chitosan (QUI) blends. It investigated thermal and mechanical morphological characteristics of the blends, as the same time, the antifungal activity of the packaging. To assess the antimicrobial activity of the PLA/EVA/PEG/QUI blends, the samples were inserted between slices of bread with no preservative to the evaluation of their shelf life. By comparing between PLA/EVA/PEG, PLA/EVA/PEG/QUI blends and neat PLA was possible to evidence the partial miscibility, decreased glass transition temperature (Tg) by incorporating PEG into the blends, a decrease in flexural strength of 71% and elasticity modulus of 80.4% to PLA/EVA/PEG/2.5QUI blend, as well as an increase in elongation at break of 153% and 392% to impact toughness. A similar behavior was observed to PLA/EVA/20PEG and PLA/EVA/PEG/5.0QUI. The QUI-containing film among the bread slices has also influenced the water activity reduction, and reduced about 35% in the count of molds and yeasts in the slices of bread. Chitosan in mixtures with PLA/EVA/PEG showed potential as a natural antifungal agent in bakery packaging.

Study of thermal behavior of poly (lactic) acid composites with electron beam irradiated luffa fiber

2020 ◽  
pp. 2150009
Author(s):  
S. Patra ◽  
K. L. Mohanta ◽  
C. Parida
Keyword(s):  
Thermal Stability ◽  
Electron Beam ◽  
Lactic Acid ◽  
Glass Transition ◽  
Thermal Properties ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Irradiation Dose ◽  
Poly Lactic Acid ◽  
Thermal Stability Of

Modification of surface of natural fibers by high energy electron beam irradiation (6 MeV) is a process for enhancing the adhesion between fiber and matrix. Composites reinforced with natural fiber have gained a prominent place in the field of research and innovation due to the advantages such as low cost, light weight and environment friendly factors. We have studied the thermal properties such as thermal degradation and crystallinity behavior of biodegradable composites using biodegradable polymer poly (lactic) acid (PLA) and fiber of luffa cylindrica (LC) fabricated by using injection molding technique. First, reinforcement LC fibers are irradiated with electron beam of 0.5, 1.0, 2.0, 4.0 and 10.0 Gy using 6 MeV linear accelerator at room temperature in presence of air. The thermal properties like glass transition temperature [Formula: see text], cold crystallization temperature [Formula: see text], melting peak temperature [Formula: see text] and thermal stability of the composites are studied using differential scanning calorimetry (DSC) in the temperature range from 30[Formula: see text]C to 250[Formula: see text]C and thermogravimetric analysis (TGA) in temperature range from 20[Formula: see text]C to 700[Formula: see text]C. The variation of these properties in response to the irradiation dose is analyzed in detail. It is observed that with increase in irradiation dose, glass transition temperature and crystallization temperature increase. However, the thermal stability of the composites is found to increase with increase in irradiation dose.

Study on the Crystallization Activation Energy of Poly (L-lactic acid) Nucleated with P-tert-butylcalix[8]arene

2018 ◽  
Vol 26 (2) ◽  
pp. 169-175
Author(s):  
Yaoqi Shi ◽  
Liang Wen ◽  
Zhong Xin
Keyword(s):  
Activation Energy ◽  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Crystallization Temperature ◽  
Nucleating Agent ◽  
Crystallization Activation Energy ◽  
Temperature Range ◽  
Chain Mobility

The crystallization activation energy (Δ E) of a polymer comprises the nucleation activation energy Δ F and the transport activation energy Δ E*. In this paper, the Δ E of poly (L-lactic acid) (PLLA) nucleated with nucleating agent p- tert-butylcalix[8]arene (tBC8) was calculated. The results showed that the Δ E of nucleated PLLA was 165.97 kJ/mol, which is higher than that of pure PLLA. The reason why Δ E of PLLA increased when incorporating nucleating agent was studied. The increment of glass transition temperature ( Tg) for nucleated PLLA revealed that the polymer chain mobility was restricted by tBC8, which was considered as the reason for the increase of Δ E*. Further, polyethylene glycol (PEG) was added to improve the chain mobility, thus eliminated the variation of the transport activation energy Δ E* caused by tBC8. Then the effect of the increment of crystallization temperature range on the increase of Δ F was also taken into consideration. It was concluded that both decreasing the mobility of chain segments and increasing the crystallization temperature range caused an increase of Δ E for PLLA/tBC8.

scholarly journals Shape-Memory Properties of 3D Printed Cubes from Diverse PLA Materials with Different Post-Treatments

Technologies ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 71
Author(s):  
Guido Ehrmann ◽  
Bennet Brockhagen ◽  
Andrea Ehrmann
Keyword(s):  
Lactic Acid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Shape Memory ◽  
Poly Lactic Acid ◽  
Safety Equipment ◽  
Shape Memory Properties ◽  
3D Printed ◽  
Proper Material ◽  
The Impact

Poly(lactic acid) (PLA) belongs to the 3D printable materials which show shape-memory properties, i.e., which can recover their original shape after a deformation if they are heated above the glass transition temperature. This makes PLA quite an interesting material for diverse applications, such as bumpers, safety equipment for sports, etc. After investigating the influence of the infill design and degree, as well as the pressure orientation on the recovery properties of 3D printed PLA cubes in previous studies, here we report on differences between different PLA materials as well as on the impact of post-treatments after 3D printing by solvents or by heat. Our results show not only large differences between materials from different producers, but also a material-dependent impact of the post treatments. Generally, it is possible to tailor the mechanical and recovery properties of 3D printed PLA parts by choosing the proper material in combination with a chemical or temperature post-treatment.

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