Insight into the annealing peak and microstructural changes of poly(l-lactic acid) by annealing at elevated temperatures

Wei, Zhiyong; Song, Ping; Zhou, Cheng; Chen, Guangyi; Chang, Ying; Li, Jianfeng; Zhang, Wanxi; Liang, Jicai

doi:10.1016/j.polymer.2013.04.027

Cited by 41 publications

(33 citation statements)

References 63 publications

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“…9, with melt crystallization, T g decreases slightly first and then increases with further increasing crystallinity. During cold crystallization, however, the T g seems to decrease steadily with the increase of crystallinity; the maximum decrease in T g is about 5 K [39]. Particularly, at the lowest cold crystallization temperature, 79.3°C, T g seems to reduce dramatically in the beginning when little crystallinity is formed.…”

Section: Evolution Of Mobile Amorphous Fractionmentioning

confidence: 90%

Crystallization kinetics and structure evolution of a polylactic acid during melt and cold crystallization

Henricks

Boyum

Zheng

2015

J Therm Anal Calorim

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The isothermal melt and cold crystallization and the evolutions of the mobile and rigid amorphous fractions during the crystallization are fully investigated for a polylactic acid using differential scanning calorimetry. The crystallization kinetics is analyzed through fitting the Avrami equation to two different sets of crystallinity data, one obtained from the crystallization extherms and one from the enthalpies of melting and cold crystallization. Both sets yield similar results, indicating the consistency between these two methodologies. The cold crystallization shows clearly faster crystallization rate and has a higher activation energy of 172.3 ± 8.9 versus 109.6 ± 8.8 kJ mol -1 for the melt crystallization. The Avrami exponent of the cold crystallization seems to decrease with increasing crystallization temperature, whereas the exponent of melt crystallization is relatively constant. In addition to the crystalline phase, properties of the mobile and rigid amorphous fractions are also studied and compared. With the increase in crystallinity, the glass transition temperature (T g ) of the mobile amorphous phase is found to decrease during the cold crystallization, whereas T g decreases and then increases during the melt crystallization, indicating slightly different environment formed. However, no obvious difference is found regarding the heat capacity change at T g nor the cooperative length scale associated with T g . Furthermore, the rigid amorphous fraction is determined and found to be 30 % at the maximum crystallinity for the both cold-and melt-crystallized samples.

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Section: Evolution Of Mobile Amorphous Fractionmentioning

confidence: 90%

Crystallization kinetics and structure evolution of a polylactic acid during melt and cold crystallization

Henricks

Boyum

Zheng

2015

J Therm Anal Calorim

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“…This thermal analysis technique has been used in our previous research to investigate the origin of annealing peak of PLLA. 56 Exothermic peaks can only be detected in the nonreversible part, while endothermic peak appears in both parts. Namely, crystallization and recrystallization process can be easily separated from reversible melting events.…”

Section: Multiple Melting Behavior and Equilibrium Melting Pointmentioning

confidence: 98%

“…Namely, crystallization and recrystallization process can be easily separated from reversible melting events. [56][57][58] As shown in Fig. 9(a), there is only one melting peak and one obvious crystallization peak detected in the reversible and nonreversible part, respectively, which determines the existence of melting-recrystallization-melting process.…”

Section: Multiple Melting Behavior and Equilibrium Melting Pointmentioning

confidence: 99%

Biobased copolyesters from renewable resources: synthesis and crystallization kinetics of poly(propylene sebacate-co-isosorbide sebacate)

Zhou

Wei

et al. 2015

RSC Adv.

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In this work, a series of novel biobased copolymers, poly(propylene sebacate-co-isosorbide sebacate) (P(PSe-co-IS)), were synthesized by melt-polycondensation from sebacic acid (SA) and isosorbide (IS) with 1,3-propanediol (PD). In order to analyze the effects of isosorbide on the relative properties of poly(propylene sebacate) (PPSe), the composition, crystal structure, crystallization behavior, multiple melting behavior, and spherulitic morphology of these copolymers were investigated by 1 H-NMR, WAXD, DSC, TMDSC and POM, respectively. Results of 1 H-NMR indicated that IS have been successfully introduced into the PPSe main chains with the designed molar ratio. DSC data showed that crystallization ability of P(PSe-co-IS) copolymers was retarded with the introduction of IS. With the increment of IS, the overall crystallization rate decreased gradually. Furthermore, crystallization temperature (T c ), crystallization enthalpy (DH c ), melting temperature (T m ), and equilibrium melting temperature (T o m ) of P(PSe-co-IS) copolymers also decreased apparently with the increase of IS content. WAXD suggested that crystal structure of PPSe was not affected by IS, and POM revealed that all spherulites possess the typical "Maltese Cross" image. Furthermore, no obvious ring-banded spherulites could be detected for P(PSe-co-IS) copolymers in the wide temperature range except neat PPSe due to the hindrance of IS. With the increment of IS and crystallization temperature, the number of spherulites decreased rapidly and the size of spherulites increased, respectively.

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“…In another study, it has been shown that the RAF is not located at the lateral surface area of crystals []. Wei et al [] show that an annealing of semicrystalline PLA promotes the chain mobility of the amorphous phase and divides it into two components, a more ordely RAF linked to crystals and a relaxed MAP. So, RAF is characterized as an extended boundary between the crystalline and the MAP induced by tie molecules [].…”

Section: Introductionmentioning

confidence: 99%

Evidence of two mobile amorphous phases in semicrystalline polylactide observed from calorimetric investigations

et al. 2013

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Amorphous phase dynamics in Poly(lactic acid) (PLA) with different crystallinity degrees have been investigated from the vitreous state to the glass transition by means of two calorimetric methods. Temperature Modulated Differential Scanning Calorimetry was used to characterize the heat capacity signals and the average cooperativity length at the glass transition in non‐aged materials. Standard DSC was used to study the physical aging. It is shown that amorphous and fully crystallized PLA exhibit different relaxation parameters. For semicrystalline PLA with an intermediate degree of crystallinity, the peaks of the enthalpy of recovery and the out‐of‐phase heat capacity component are bimodal. The bimodality of the peaks is attributed to the relaxations of the inter‐spherulitic and intra‐spherulitic amorphous phases, respectively. Thus, in partially crystallized PLA, the non‐crystalline fraction of the material could be divided in three fractions, namely the Rigid Amorphous Fraction, the inter‐spherulitic Mobile Amorphous Phase (MAP), and the intra‐spherulitic MAP. Each of them exhibits a distinct molecular mobility. POLYM. ENG. SCI., 54:1144–1150, 2014. © 2013 Society of Plastics Engineers

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Insight into the annealing peak and microstructural changes of poly(l-lactic acid) by annealing at elevated temperatures

Cited by 41 publications

References 63 publications

Crystallization kinetics and structure evolution of a polylactic acid during melt and cold crystallization

Crystallization kinetics and structure evolution of a polylactic acid during melt and cold crystallization

Biobased copolyesters from renewable resources: synthesis and crystallization kinetics of poly(propylene sebacate-co-isosorbide sebacate)

Evidence of two mobile amorphous phases in semicrystalline polylactide observed from calorimetric investigations

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