“…PCL is a biodegradable polyester with a very flexible chain, characterized by a low glass transition temperature ( -60°C), although the melting and crystallization also occur in the lowtemperature range at around 60 and 30°C, respectively. In this section, the main works dealing with the crystallization behavior of these blends, including the effect of composition and additives, are summarized [16,31,32,36,38,[59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78]. Table 2 provides a compendium of the related studies.…”
“…Similarly to the case of PLA/PBS blends, a distinct effect of PCL on the crystallization of PLA from the glassy state in their immiscible blend has also been extensively reported. [38,44,59,60,62,66,[69][70][71]. A literature-based collection of PLA cold-crystallization temperatures as a function of PCL content is presented in Figure 11, according to the same normalization method employed in Figure 6.…”
Bio-based thermoplastic polyesters are highly promising materials as they combine interesting thermal and physical properties and in many cases biodegradability. However, sometimes the best property balance can only be achieved by blending in order to improve barrier properties, biodegradability or mechanical properties. Nucleation, crystallization and morphology are key factors that can dominate all these properties in crystallizable biobased polyesters. Therefore, their understanding, prediction and tailoring is essential. In this work, after a brief introduction about immiscible polymer blends, we summarize the crystallization behavior of the most important bio-based (and immiscible) polyester blends, considering examples of double-crystalline components. Even though in some specific blends (e.g., polylactide/polycaprolactone) many efforts have been made to understand the influence of blending on the nucleation, crystallization and morphology of the parent components, there are still many points that have yet to be understood. In the case of other immiscible polyester blends systems, the literature is scarce, opening up opportunities in this environmentally important research topic.
“…PCL is a biodegradable polyester with a very flexible chain, characterized by a low glass transition temperature ( -60°C), although the melting and crystallization also occur in the lowtemperature range at around 60 and 30°C, respectively. In this section, the main works dealing with the crystallization behavior of these blends, including the effect of composition and additives, are summarized [16,31,32,36,38,[59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76][77][78]. Table 2 provides a compendium of the related studies.…”
“…Similarly to the case of PLA/PBS blends, a distinct effect of PCL on the crystallization of PLA from the glassy state in their immiscible blend has also been extensively reported. [38,44,59,60,62,66,[69][70][71]. A literature-based collection of PLA cold-crystallization temperatures as a function of PCL content is presented in Figure 11, according to the same normalization method employed in Figure 6.…”
Bio-based thermoplastic polyesters are highly promising materials as they combine interesting thermal and physical properties and in many cases biodegradability. However, sometimes the best property balance can only be achieved by blending in order to improve barrier properties, biodegradability or mechanical properties. Nucleation, crystallization and morphology are key factors that can dominate all these properties in crystallizable biobased polyesters. Therefore, their understanding, prediction and tailoring is essential. In this work, after a brief introduction about immiscible polymer blends, we summarize the crystallization behavior of the most important bio-based (and immiscible) polyester blends, considering examples of double-crystalline components. Even though in some specific blends (e.g., polylactide/polycaprolactone) many efforts have been made to understand the influence of blending on the nucleation, crystallization and morphology of the parent components, there are still many points that have yet to be understood. In the case of other immiscible polyester blends systems, the literature is scarce, opening up opportunities in this environmentally important research topic.
“…However, PCL showed poor miscibility with PLA even at a molten temperature [17], which resulted in unsatisfactory toughening effects, and eventually leaded to a deterioration in other properties, such as strength, modulus, especially transparency, which was important for food packaging and other consumer products. Therefore, more researches had aimed to increase the compatibility between the two phases without significantly compromising other desirable characteristics [18][19][20]. Various strategies had been used to improve the compatibility of two phases, such as the addition of a compatibilizer [21], reactive compatibilization [22], and copolymerization [23].…”
Modification of poly(L-lactide) (PLLA) via blending with two or more polymers is one of the effective approaches used to overcome the brittleness of PLLA, which often requires the addition of a compatibilizer and generate opaque materials. To solve this problem, multiarmed polycaprolactone-block-PLLA (PCL-b-PLLA) was synthesized by consecutive ring-opening polymerization of e-caprolactone and L-lactide using multihydroxyl alcohols as initiator. The structure and composition was confirmed by proton nuclear magnetic resonance and gel permeation chromatography. PLLA/multiarmed PCL-b-PLLA blends with various blend ratios were prepared via melt mixing. The presence of multiarmed PCL-b-PLLA (30%) in the PLLA matrix exhibited more than 80 times improvement in the elongation at break, as compared to unmodified PLLA. The addition of multiarmed PCL-b-PLLA in the PLLA contributed to the enhancement of the storage modulus in the low frequency, which was related to the entanglement of the PLLA and multiarmed PCL-b-PLLA. The blend interface had no obvious phase separation, and showed good adhesion between dispersed block copolymer phases within the continuous PLLA phase. The compatibilization mechanism and toughing mechanism were proposed. The resulting PLLA blends also showed good transparency. The current research opened a new route available to prepare transparent PLA-based resin with enhanced properties.
“…For instance, the addition of small molecular weight chemicals or polymers with reactive groups has been used to form in situ bloc copolymers that act as compatibilisers. Polymers containing reactive glycidyl [17] or maleic groups [3] and small molecules with carbodiimide [18], epoxide [19], caprolactam [20], oxazoline [21] and isocyanate moieties [22-25] have been used for such purpose. Figure 2 Chemical structures of the various thermoplastic (TPE) elastomers: (a) PEBA; (b) PEEs; (c) PEU.…”
Poly(lactic acid) (PLA) is characterised by its inherent brittleness, a detrimental feature for the production of durable bioplastics. PLA has been toughened by a low amount (12 wt-%) of various thermoplastic elastomers (TPE) including poly(ether-b-ester) (PEEs), poly(ether-bamide) (PEBA) and poly(ether-b-urethane) (PEU). PLA-TPE blends were prepared by using a twin screw extruder. Ductility and impact resistance can be slightly improved with the incorporation of TPEs but but PEBA appears the most efficient. Reactive compatibilisation has been performed with the addition in the melt of a low amount (2 wt-%) of 4,4-methylene diphenyl diisocyanate. All compatibilised blends exhibit high toughness with similar ductility. These blends preserve good stiffness and high tensile strength. Compatibilised PEBA blends can be considered as super tough poly(lactic acid) materials. This work confirms that the flexibility of the elastomer together with the quality of the interfacial adhesion between the rigid (PLA) and the soft (TPE) phases are the primary factors influencing the toughness.
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