Crystallization, morphology, and mechanical behavior of polylactide/poly(ε‐caprolactone) blends

Abstract

Optically pure polylactides, poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), were blended across the range of compositions with poly(-caprolactone) (PCL) to study their crystallization, morphology, and mechanical behavior. Differential scanning calorimetry and dynamic mechanical analysis (DMA) of the PLA/PCL blends showed two T g s at positions close to the pure components revealing phase separation. However, a shift in the tan ␦ peak position by DMA from 64 to 57°C suggests a partial solubility of PCL in the PLA-rich phase. Scanning electron microscopy reveals phase separation and a transition in the phase morphology from spherical to interconnected domains as the equimolar blend approaches from the outermost compositions. The spherulitic growth of both PLA and PCL in the blends was followed by polarized optical microscopy at 140 and 37°C. From tensile tests at speed of 50 mm/min Young's modulus values between 5.2 and 0.4 GPa, strength values between 56 and 12 MPa, and strain at break values between 1 and 400% were obtained varying the blend composition. The viscoelastic properties (E and tan ␦) obtained at frequency of 1 Hz by DMA are discussed and are found consistent with composition, phase separation, and crystallization behavior of the blends. POLYM. ENG. SCI., 46:1299 -1308, 2006.

Isothermal and nonisothermal crystallization kinetics of poly(ϵ‐caprolactone)

“…The values of n and K determined from the slope and intercept of the initial linear portion of the plots in Figure 2 are listed in Table I. n was in the range from 2.6 to 3.4; this indicated a three-dimensional heterogeneous nucleation with a spherical crystal geometry, which was in good agreement with the values of 2.5-3.5 reported by Goulet and Prud'homme 54 for temperatures ranging from 40 to 49 C for M w ¼ 48,000 and the n values of 2.2-2.8 published by Priftis et al 55 for M n ¼ 29,000 in a temperature range of [42][43][44][45][46][47][48] C. Skoglund and Fransson 56 found an n value of 3 for M w ¼ 55,000 at 47 C, whereas Balsamo et al 57 reported n values between 3 and 3.7 in a 35-48 C temperature range for a similar molecular weight PCL. The Avrami index for the PCL homopolymer was confirmed as 3 by Muller et al 58 Table I also lists other important parameters for this analysis, including the half-time of crystallization (t 1/2 ), which is defined as the time taken from the onset of crystallization until 50% completion, which was determined from Figure 1.…”

Electrical and thermal properties of PLA/CNT composite films

“…On the other hand, CNT contend showed an influence in crystallization, especially in the PLA/CNT 5% composition. PLA presents two crystallization temperatures, the second one right before Tm, assigned as recrystallization of imperfect crystals to more perfect ones [10]. This behavior was also observed for compositions with 1% and 2% of CNT.…”

Effect of halloysite on structure and properties of melt-drawn PCL/PLA microfibrillar composites

“…As a result, low yield stress, stiffness, and high ductile deformation under ambient conditions limit the range of PCL applications. The purpose of numerous modifications is, in particular, higher yield stress and modulus [1]; advantageous modifications are those preserving biodegradability, for instance blending with more rigid polyesters, mostly PLA [2][3][4][5].…”

“…The mostly applied PLLA containing 2-4% D-isomer has low compatibility with PCL [5]; therefore, various compatibilizing techniques [6,7] must be applied. In this area, application of various nanofillers (NF) leading to simultaneous reinforcement, compatibilization, and improvement of other material parameters may also be beneficial [8][9][10][11][12].…”