Miscibility and Crystallization Behavior of Crystalline/Crystalline Polymer Blends. Poly(ester carbonate)/Poly(l-lactic acid)

Abstract

KEY WORDSPoly(butylene succinate-co-butylene carbonate) / Poly(L-lactic acid) / Crystalline Polymer Blends / Interpenetrated Spherulites / The numbers of the studies on miscible pairs of crystalline polymers with different chemical structures are still restricted compared with those with similar chemical structures. 1-10 The differences of the melting temperatures T m of the components are usually 100 • C in the former systems. In these cases, the higher-T m component crystallizes first in the crystallization process and the other component then crystallizes in spatially constrained amorphous regions inside the spherulites.In contrast, when T m s of both components are close enough to each other, the blends exhibit simultaneous spherulitic growth. The spherulites in poly(butylene succinate)/poly(vinylidene chloride-co-vinyl chloride) (PBSU/PVDCVC) blends, whose T m difference is about 35 • C, grow simultaneously. These blends were found to show interpenetrated spherulites (IPS). 11,12 They are characterized by the penetration of PBSU lamellae into PVDCVC spherulites since the lamellar population density in a spherulite is larger for PBSU than for PVDCVC. 13,14 They are expected to have various unique physical characteristics.The reports on the blend systems that show IPS are very few. This is partly because miscible crystalline polymers rarely have close T m s. Our group has been searching polymer blends that show IPS.Poly(butylene succinate-co-butylene carbonate) (PEC) and poly(L-lactic acid) (PLLA) are polyesters whose T m s are close to each other (106 • C and 140 • C, respectively). If they are miscible, they possibly crystallize simultaneously and show IPS. Furthermore, since both PEC and PLLA are biodegradable, PEC/PLLA blends can be ecological crystalline polymer blends.The purposes of this paper are to show miscibility of PEC/PLLA by differential scanning calorimetry (DSC), to study the crystallization behavior by polarizing optical microscopy (POM), and to investigate the possibility of IPS. PEC/PLLA blends were prepared with mutual solvent chloroform at room temperature. The solution was cast on glass plates and then the solvent was removed at room temperature to make thin films for POM observation. For DSC, the solution was dried for a week and then in a vacuum for three days to remove the solvent from the bulky samples.The glass transition temperature T g was determined by DSC (TA Instruments DSC 2910). Samples were heated to 170 • C for 5 min, quenched to −100 • C using liquid nitrogen, kept for 5 min, and heated at 10 • C min −1 . The value of T g was determined as the temperature of the half-height of the step transition.To study the morphology of the blends and the radial spherulitic growth rates G of PEC and PLLA, we used POM (Olympus BHP-P) equipped with a first order retardation plate and a temperature controller (Linkam TH-600). Samples were premelted at 170 • C for 3 min and then quenched to the crystallization temperature T c . RESULTS AND DISCUSSIONTo confirm the miscibility of the PEC/PLL...

Crystallization kinetical and morphological peculiarities in binary crystalline/crystalline polymer blends

“…36,37,41 Simultaneous crystallization (in the sense that the components crystallize at the same time) upon isothermal conditions, and the IPC as well as the ILC schemes, respectively, could be realized, for example, in the blend PBSU/ P(VDC-co-VC), [46][47][48][49][50][51][52][53] in the blend PESU/PEO 26,28 and in the blend PLA/P(BSU-co-BC). 44,45 The actual crystallization scheme-whether S-co-S, IPC, ILC, or IFC, whether one-step or two-step crystallization occurs-depends clearly on the composition and on the thermal conditions. All schemes may be realized in a given blend system by proper choose of these boundary conditions.…”

Synchrotron SAXS Studies on Morphology Formation in a Binary Blend of Poly(ε-caprolactone) Homopolymer and Poly(ε-caprolactone)-block-Polybutadiene Copolymer

“…As a result, we study the morphology formation in a binary blend of two crystalline polymers with an UCST-type phase separation between components. Though there is a limited number of studies on the crystallization behavior and resulting morphology for completely miscible binary blends, [17][18][19][20] it is a new point to investigate the process of morphology formation by the combined effect of crystallization and phase separation by using two crystalline polymers.…”

Crystallization Kinetics and Hydrophilicity Improvement of Biodegradable Poly(butylene succinate) in its Miscible Blends with Poly(ethylene oxide)

“…However, miscible polymer blends involving two crystalline components have received much less attention than fully amorphous or amorphous/crystalline blends. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] It is of great importance, from both academic and technological viewpoints, to investigate this special kind of blend, in which both components are able to crystallize with different conditions leading to varied crystallization behavior and morphology. Recently, Jungnickel reviewed the crystallization kinetic and morphological peculiarities in binary crystalline/crystalline polymer blends.…”

“…When the gap between the T m s is large, the melting and crystallization behavior occurring in both component phases can be studied separately. [1][2][3][4][5][6][7][8][9][10][11][12][13] In addition to the effects of blend composition and crystallization temperature, the crystallization kinetics in these blends is also concerned with the question of how the crystallinity of one component affects the crystallization behavior of the other. Therefore, a thorough investigation of The spherulitic morphology and growth, overall isothermal crystallization kinetics and hydrophilicity of PBSU were investigated by POM, DSC and WCA measurements in its miscible blends with PEO.…”

“…Furthermore, interpenetrated spherulites are found in a few miscible pairs of two crystalline polymers when the two components crystallize simultaneously. [11][12][13][14][15][16][17][18][19][20] Moreover, of particular interest and importance is that most of the reported miscible binary crystalline blends, such as poly(3-hydroxybutyrate) (PHB)/PEO, [4] PHB/poly (ethylene succinate) (PES), [8] poly(vinylidene fluoride) (PVDF)/PHB, [10] poly(L-lactic acid) (PLLA)/poly(ester carbonate) (PEC) [11,12] and PLLA/PHB blends, [16] consist of biodegradable aliphatic polyesters. PBSU/PEO blends are typical miscible crystalline/crystalline blends with PBSU being the high-T m component and PEO the low-T m component.…”