Solution and melt viscoelastic properties of controlled microstructure poly(lactide)

Othman, Norhayani; Acosta-Ramírez, Alberto; Mehrkhodavandi, Parisa; Dorgan, John R.; Hatzikiriakos, Savvas G.

doi:10.1122/1.3609853

Cited by 70 publications

(67 citation statements)

References 36 publications

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“…Solution properties Figure 1 plots the intrinsic viscosities, [η] of the four commercial PLAs as well as those reported previously by Othman et al (2011) as a function of the weightaverage molecular weight. The data agree well and the linearity in this plot implies linear random coils.…”

Section: Resultsmentioning

confidence: 99%

“…The extensional behaviour of PLAs was also studied first by Palade et al (2001) reporting strain hardening. This was studied more extensively by Othman et al (2011). They have reported significant strain hardening at low temperatures which gradually disappears with an increase in temperature and decrease of Hencky strain rate.…”

Section: Introductionmentioning

confidence: 92%

“…The most comprehensive studies of melt PLAs has been reported by Dorgan and co-workers (Dorgan et al 1999;Palade et al 2001;Dorgan et al 2005a;Cooper-White and Mackay 1999). Thermally stabilized samples were used to demonstrate the zeroshear viscosity relationship with molecular weight by power of 3.4 which is expected for well-entangled linear polymers, also confirmed by Othman et al (2011). The extensional behaviour of PLAs was also studied first by Palade et al (2001) reporting strain hardening.…”

Section: Introductionmentioning

confidence: 98%

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Wall slip and melt fracture of poly(lactides)

et al. 2011

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The wall slip and melt fracture behaviour of several commercial polylactides (PLAs) as well as their rheological properties under shear and extensional have been investigated. The PLAs have had weight-average molecular weights in the range of 10 4 -10 5 g/mol and studied in the temperature range of 160-200 • C. The solution properties and linear viscoelastic behaviour of melts indicate linear microstructure behaviour. PLAs with molecular weights greater than a certain value were found to slip, with the slip velocity to increase with decrease of molecular weight. The capillary data were found to agree well with linear viscoelastic envelope once correction for slip effects was applied. The onset of melt fracture for the high molecular weight PLAs was found to occur at about 0.2 to 0.3 MPa, depending on the geometrical characteristics of the dies and independent of temperature. Addition of 0.5 wt.% of a polycaprolactone (PCL) into the PLA that exhibits melt fracture was found to be effective in eliminating and delaying the onset of melt fracture to higher shear rates. This is due to significant interfacial slip that occurs in the presence of PCL.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 98%

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Wall slip and melt fracture of poly(lactides)

et al. 2011

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“…As discussed above, the samples were kept in the vacuum oven at 35°C for 24 h to remove any solvents and humidity and to have the same thermal history. The rheological properties of the pure components of several PCLs and PLAs as functions of molecular weight characteristics have been studied and reported before (Noroozi et al 2012b;Othman et al 2011).…”

Section: Rheological Measurementsmentioning

confidence: 99%

Dynamics of partially miscible polylactide-poly(ε-caprolactone) blends in the presence of cold crystallization

et al. 2016

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Previous studies on polylactide (PLA)/poly(ε-caprolactone) (PCL) biodegradable blends revealed enhanced nucleation of PLA. The mechanism by which this enhancement of nuclei density occurs attracted significant interest. In this study, precursors' transportation from PCL into PLA phase is invoked in order to interpret the experimental findings related to phase separation and crystallization. This mechanism is supported by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The DSC data revealed that PCL crystallinity within the blends is decreased with PLA content. In addition, POM data showed more nuclei within PLA as the PCL weight fraction is increased. The linear viscoelastic properties of these blends in the vicinity of the phase separation and cold crystallization boundary are examined. It is shown that the combination of POM and rheometry allows determining the phase diagram of the blend and identifying changes occurring due to phase separation and crystallization. Thus, the complete phase diagram of such systems can be fully determined, essential in process design and optimization.

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“…Thus, PLLA offers great promise as one of the select few candidates for use in biomedical applications such as surgical sutures, bone fixation devices, and controlled drug-delivery systems. Moreover, due to its favorable biodegradability, good mechanical properties, and versatile fabrication processes, it has excellent potential for substitution of petroleum-based polymers [4][5][6]. Unfortunately, PLLA has several drawbacks, in terms of the processability and mechanical properties.…”

Section: Introductionmentioning

confidence: 99%

Non-Isothermal Cold-Crystallization Behavior and Kinetics of Poly(l-Lactic Acid)/WS2 Inorganic Nanotube Nanocomposites

2015

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Abstract:In order to accelerate the crystallization of poly(L-lactic acid) (PLLA) biopolymer and enhance its crystallizability, biocompatible and environmentally friendly tungsten disulphide inorganic nanotubes (INT-WS 2 ) were introduced into the polymer matrix. The non-isothermal cold-crystallization and subsequent melting behaviour of pure PLLA and PLLA/INT-WS 2 nanocomposites were investigated in detail by varying both the heating rate and INT-WS 2 loading. The kinetic parameters of the cold-crystallization process of PLLA chains under confined conditions, successfully described using Liu model, shows that the addition of INT-WS 2 significantly increased the crystallization rate and reduced the total cold-crystallinity of PLLA, while the crystallization mechanism and crystal structure of PLLA remained unchanged in spite of the INT-WS 2 loading. Similarly, the final crystallinity and melting behaviour of PLLA were controlled by both the incorporation INT-WS 2 and variation of the heating rate. The differential isoconversional method of Friedman was applied to estimate the dependence of the effective activation energy on the relative crystallinity and temperature for PLLA and PLLA/INT-WS 2 . On the other hand, the double-melting peaks, mainly derived from melting-recrystallization-melting processes upon heating, and their dynamic behaviour is coherent with a remarkable nucleation-promoting effect of INT-WS 2 involved in accelerating the cold-crystallization of PLLA. These observations have considerable practical significance for the future sustainable, economic and effective technological utilisation of PLLA, as it will enable the development of novel melt-processable biopolymer nanocomposite materials.

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Solution and melt viscoelastic properties of controlled microstructure poly(lactide)

Cited by 70 publications

References 36 publications

Wall slip and melt fracture of poly(lactides)

Wall slip and melt fracture of poly(lactides)

Dynamics of partially miscible polylactide-poly(ε-caprolactone) blends in the presence of cold crystallization

Non-Isothermal Cold-Crystallization Behavior and Kinetics of Poly(l-Lactic Acid)/WS2 Inorganic Nanotube Nanocomposites

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