Brittle-to-ductile transition of PLA induced by macromolecular orientation

Poly(l-lactide): optimization of melting temperature and melting enthalpy and a comparison of linear and cyclic species

“…A first intensive study in this direction was performed by the group of Pennings [12][13][14][15] followed by numerous other research groups. [16][17][18][19][20][21][22][23][24][25][26][27] Studies above 120 1C are simplified by the fact that the a-modification is the thermodynamically most stable crystal modification. 28 3.…”

The Effect of Processing Parameters and Calcium-stearate on the Ejection Process of Injection Molded Poly(Lactic Acid) Products

“…This is because each processing parameter, like temperature, pressure, volume, and flow rate can be precisely controlled [7]. A great deal of research has been dedicated in the last two decades to improving PLA, for example, improving its HDT through nucleation [8] or stereocomplexation [9], improving its ductility through plasticization [10,11], blending [12,13], orientation [14] or improving its impact strength [15,16], and tensile strength through reinforcement with several types of fibers including plant [17] and basalt fibers [18,19]. At the same time, the injection molding of PLA is little researched, especially the ejection process of PLA parts, although a continuous series production is needed, free from human intervention, for mass production.…”

Deformation of Poly-l-lactid acid (PLLA) under Uniaxial Tension and Plane-Strain Compression

“…On the other hand, compression, rolling, solid-state extrusion, or die-drawing can be applied to induce chain orientation in objects with large cross-sections, and thus to obtain materials with improved stiffness and strength, suitable for the production of technical parts or other items with larger dimensions, such as, e.g., biocompatible surgical implants. From this point of view, the structural changes and mechanical behavior of PLLA in various deformation modes and under different conditions have recently attracted considerable attention [10][11][12][13][14][15][16][17][18]. However, in spite of quite a large number of papers, still relatively little is known about the mechanical behavior of PLLA in relation to the crystalline structure, its plastic deformation habits, and the mechanisms involved.…”

“…The deformation behavior of PLLA was studied mostly in tensile deformation modesuniaxial [4,9,10,12,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] and biaxial drawing [13,14,[38][39][40][41][42], although other deformation modes, such as zone-drawing [43], die-drawing [44], solid-state extrusion [5][6][7]16,17] or plane-strain compression [18] were also explored. It was found that the deformation conditions, such as temperature of deformation, deformation rate, or final strain, seriously affect the structural evolution of PLLA and the resulting mechanical properties; for example, when deformation is performed at a temperature above T g , but below the cold crystallization temperature T cc (in this temperature range, the crystallization rate is too low to generate noticeable crystallinity in the time scale of the deformation experiment), the initially amorphous PLLA sample remains amorphous at low and moderate strains and then undergoes strain-induced crystallization when the strain increases [31,40] due to a decrease in conformational entropy associated with molecular orientation that grows gradually with increasing strain.…”

“…Polymers 2021,13, x FOR PEER REVIEW 4 of 31 ρ = 1.24 g/cm 3 , the melt flow rate MFR = 15.4 g/10 min (210 °C, 2.16 kg), molecular weight Mw = 95,000, and polydispersity Mw/Mn = 1.33 as determined by SEC with a multi-angle laser light scattering (MALLS) detector (Wyatt Technology Corp., CA, USA), in methylene chloride.…”