Effects of Temperature and External Force on the Stereocomplex Crystallization in Poly(lactic acid) Blends

Abstract

An investigation of the effects of temperature and external force on the stereocomplex-type poly(lactide acid) formation between equimolar of poly(L-lactide acid) (PLLA) and poly(D-lactide acid) (PDLA) was conducted. Wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) analysis indicated that exclusive stereocomplex-type poly(lactide acid) (sc-PLA) with relatively high crystallinity could be obtained at lower (0°C) temperature. During solution mixing process, increasing stirring speed within range 0-200 rpm was conductive to the formation of sc-PLA. However, excessive stirring speed gave rise to a decrease in sc-PLA production. During solvent evaporation process, addition of shaking could effectively improve formation of sc-PLA, wherein crystallinity of sc-PLA approached the maximum value as shaking speed reach 100 rpm. These suggest that lower temperature and appropriate external force are positive to the formation of sc-PLA in PLLA/PDLA blends.

Influence of Chain-Extension Reaction on Stereocomplexation, Mechanical Properties and Heat Resistance of Compressed Stereocomplex-Polylactide Bioplastic Films

“…This may be explained by the compression force under high temperature ( T > T m,hc ) induced stereocomplex formation of the film matrix. It has been reported that external force can enhance sterecomplexation [15,17,28].…”

“…These scPLA films have been widely used in research, and are prepared by solution blending [7,8,11,15,16,17]. However, fabrication of scPLA films by melt processing is interesting, because of its possible use in industrial-scale applications.…”

Appraisal of ε‐Caprolactam and Trimellitic Anhydride Potential as Novel Chain Extenders for Poly(lactic acid)

“…The XRD diffractogram of the neat PLA reveals a semi‐crystalline material and shows an intense diffraction peak at 2 θ = 11.6° corresponding to the (110) crystal lattice, and many other minor diffraction peaks at 14°, 17.3°, 20°, 22.4°, and 23.8° related to the (103), (110/200), (203), (210), and (220) planes of PLA, respectively. All these reflections imply the coexistence of characteristic diffraction peaks for both stereocomplex and homocrystallites, which are consistent with trigonal and pseudo‐orthorhombic structures of PLA . Because the DSC thermograms seem to be consistent with a highly predominant pseudo‐orthorhombic structure where the crystals adopt a helical conformation for the α‐form, it is suggested to be the more prevalent conformation of the neat PLA .…”

Improvement in Mechanical Properties and Heat Resistance of PLLA-b-PEG-b-PLLA by Melt Blending with PDLA-b-PEG-b-PDLA for Potential Use as High-Performance Bioplastics

“…The crystalline structures of the PLLA-PEG-PLLA and blend films were determined from XRD patterns as presented in Figure 3. The PLLA-PEG-PLLA film exhibited a diffraction peak at 17 ∘ attributed to homocrystalline structure of polylactide matrix [12], while all the blend films showed weak diffraction-peaks at 12 ∘ , 21 ∘ , and 24 ∘ ascribed to stereocomplex-crystalline structure [27,34]. The hcc,XRD of PLLA-PEG-PLLA film and scc,XRD of blend films calculated from (4) and (5), respectively, are summarized in Table 3.…”