Melting behavior of poly(l-lactic acid): X-ray and DSC analyses of the melting process

MMT and LDH organo-modification with surfactants tailored for PLA nanocomposites

“…However, at the chosen annealing temperature, the crystalline domains exist in both forms α and α′ with prevalence of the form α′, the metastable crystalline phase having different associated enthalpy value with respect to more ordered α form [26]; by taking into account that the transition of the α′ to the α-form depends only on the temperature and annealing time, the differences observed for the composites, all treated in the same experimental conditions, could be attributed to the presence of the hybrid and its dispersion degree in the polymer matrix [18]. By highlighting the XRD curves of the composites in region of PLA diffraction peaks (focusing on (200) and (203)/ (113)) it appeared evident that both the clays favoured the formation of α′ with respect to PLA matrix, as proved by the peaks shifting to lower angle ( Figure 8) [20], whose amount, being difficult to be quantified, can certainly affect the final crystallinity data. The analysis of structural and thermal stability of the polymer matrix owing hybrids dispersion evidenced different features depending on the nature of inorganic substrates (MMT-PLANH 3 and LDH-PLA-COO) ( Table 2).…”

“…After intercalation in MMT-Na a remarkable increase of T g value was noticed presumably due to oligochains confinement between the silicate platelets; the same effect is likewise responsible for the delay in the cold crystallization whose peak temperature resulted shifted more than 10 degrees towards higher temperature values. The strong interactions of PLA chains with surface layers, granted by cationic exchange reaction of ammonium end groups, presumably hindered the packing of chains into the crystal lattice providing even broader crystallization and melting peaks (see Figure 3); this latter showed a split peak ascribable to melting phenomenon of α homocrystals developed in PLLA during heating [20] and induced by the platelets interaction, [18] here observed even for PLA oligomers. Likewise, the ATR spectrum of LDH-PLACOO (Figure 4a) showed absorptions due to the PLACOONa moiety thus confirming the hybrid nature of the collected LDH system.…”

Polylactic Acid (PLA)/Cellulose Nanowhiskers (CNWs) Composite Nanofibers: Microstructural and Properties Analysis

“…The tiny peak presented at 22.4° is the typical diffraction of crystalline CNWs because CNWs generally possess two typical peaks at 15°-16° and 22.4°, and the latter is more intense [25]. The intense peak at 16.6° for PLA/10CNWs is evident, which belongs to the peaks of crystalline PLA to enhance the crystallinity degree of PLA [26]. This peak is much more pronounced than that of PLA nanofibers with addition of 7.5% CNWs [27].…”

Thermal, rheological and morphological properties of poly (lactic acid) (PLA) and talc composites

“…Figure 7a shows the appearance of double melting peaks in PLA and PLA composites. The literature [18][19][20][21] reveals that double melting behavior is a common phenomenon in semicrystalline polymers, such as PET, PA, PLA and its copolymers. Guim et al [9] informed that possibilities of double or multiple melting behaviors include the presence of different crystal forms, the presence of different morphologies (lamellar thickness and perfection) and recrystallization and remelting processes during the subsequent heating.…”