Stabilization of poly(l-lactide) in the melt

Södergård, Anders; Näsman, Jan H.

doi:10.1016/0141-3910(94)90104-x

Cited by 109 publications

(34 citation statements)

References 11 publications

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“…Figures 3a and b show the number of branches per molecule m calculated from equation (7) and the LCB frequency l calculated from equation (8), respectively, as a function of molecular weight for w-PLLA. Figure 3a indicates that the number of branches per molecule m of all w-PLLAs increases with increasing M w and that the maximum m of each w-PLLA increases with an increase in the effective radical number per PLLA precursor molecule n. Figure 3b indicates that the LCB frequency l of all w-PLLAs reaches a constant value when M w of w-PLLAs is more than 10 5.7 .…”

Section: Resultsmentioning

confidence: 99%

“…To overcome this disadvantage, various methods have been used to introduce a branched architecture into the PLLA, including chemical crosslinking, 1-4 radiation-induced crosslinking 1, [5][6][7] and peroxide-induced crosslinking. [1][2][3][4][8][9][10][11][12][13][14] Among those methods, the peroxide-induced crosslinking process by the addition of a small amount of peroxide to PLLA during extrusion has been widely accepted because of its simplicity.…”

Section: Introductionmentioning

confidence: 99%

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Molecular characterization and crystallization behavior of peroxide-induced slightly crosslinked poly(L-lactide) during extrusion

Takamura

Nakamura

Kawaguchi

et al. 2010

Polym J

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Reactive extrusion of poly(L-lactide) (PLLA) was carried out in the presence of a small amount of various peroxides with relatively slow decomposition rates. The resulting crosslinked, four-armed randomly branched PLLA (v-PLLA) was characterized by size exclusion chromatography equipped with multiangle laser light scattering (SEC-MALS), and the results were interpreted according to the type of peroxide used. A new component with a higher molecular weight than the original PLLA was observed in the SEC-MALS chromatograms of the v-PLLA. The weight-averaged molecular weight (M w ) of the v-PLLA was found to increase with increasing effective radical number per PLLA precursor (n), where n is the overall hydrogen abstraction ability of peroxide times the mole ratio of radical to PLLA precursor molecule. This implies that the hydrogen abstraction ability is a good index for the crosslinking efficiency of PLLA. The extent of branching of v-PLLA was estimated by the shrinking factor, g¼/R g 2 S b //R g 2 S l , and rationalized with n, where /R g 2 S b and /R g 2 S l are the mean square radii of gyration of branched and linear polymers with the same molecular weight, respectively. The nucleation and overall crystallization rate of v-PLLA in the nonisothermal crystallization from the melt was discussed from the viewpoints of branching and entanglement density.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Molecular characterization and crystallization behavior of peroxide-induced slightly crosslinked poly(L-lactide) during extrusion

Takamura

Nakamura

Kawaguchi

et al. 2010

Polym J

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“…In the case of intermolecular transesterification, a reaction between two ester molecules exchanges their radicals, thus leading to a variation of the distribution of Mws [140]. Only a few studies considered the intermolecular transesterification [149,150] as a mechanism present during degradation in the melt, which can be minimized by the addition of benzoyl peroxide [151], 1,4-dianthraquinone [152] and other stabilizers. Kopinke et al proposed that above 200°C, PLA can degrade through intra-and intermolecular ester exchange, cis-elimination, radical and concerted non-radical reactions, resulting in the formation of CO, CO 2 , acetaldehyde and methylketene [138,153].…”

Section: Samplementioning

confidence: 99%

Physical and mechanical properties of PLA, and their functions in widespread applications — A comprehensive review

Farah

Anderson

Langer

2016

Advanced Drug Delivery Reviews

2,252

1,486

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Available online xxxxPoly(lactic acid) (PLA), so far, is the most extensively researched and utilized biodegradable aliphatic polyester in human history. Due to its merits, PLA is a leading biomaterial for numerous applications in medicine as well as in industry replacing conventional petrochemical-based polymers. The main purpose of this review is to elaborate the mechanical and physical properties that affect its stability, processability, degradation, PLA-other polymers immiscibility, aging and recyclability, and therefore its potential suitability to fulfill specific application requirements. This review also summarizes variations in these properties during PLA processing (i.e. thermal degradation and recyclability), biodegradation, packaging and sterilization, and aging (i.e. weathering and hygrothermal). In addition, we discuss up-to-date strategies for PLA properties improvements including components and plasticizer blending, nucleation agent addition, and PLA modifications and nanoformulations. Incorporating better understanding of the role of these properties with available improvement strategies is the key for successful utilization of PLA and its copolymers/composites/blends to maximize their fit with worldwide application needs.© 2016 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirectAdvanced Drug Delivery Reviews

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“…4 Several stabilizers and metal deactivators are used to reduce degradation of PLLA during melt processing. 5,6 Another shortcoming of PLLA is its low melt viscosity, which may limit its extrusion processability. Chain extension is a useful technique to increase the molecular weight of polycondensates and hence their melt viscosity.…”

Section: Introductionmentioning

confidence: 99%

Reactive extrusion of poly(L‐lactic acid) with glycidol

Deenadayalan

Lele

Balasubramanian

2009

J of Applied Polymer Sci

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Glycidol modified polylactic acid (PLLA) polymers have been prepared by reactive extrusion. Influences of residence time and the concentration of glycidol on the extent of reaction with different weight average molecular weight (45,000, 65,000, and 100,000) PLLA's were studied. Structure-property relationship has been established by measuring molecular, mesoscopic, and macroscopic properties. Under reactive extrusion conditions glycidol reacted with the end groups of PLLA to initiate chain extension. Low-molecular weight PLLA reacted with glycidol faster than the medium molecular weight PLLA, whereas high-molecular weight PLLA did not show significant reactions. The glass transition temperature, melting temperature, crystallization temperature, and heat of fusion were measured for unmodified and modified PLLA's. Chain extended PLLA had higher T g and T m than the unmodified samples. Time sweep rheological experiments were performed to test the melt stability of PLLA. Chain extended PLLA's were found to retain viscoelastic properties for much longer time than the unreacted samples.

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Stabilization of poly(l-lactide) in the melt

Cited by 109 publications

References 11 publications

Molecular characterization and crystallization behavior of peroxide-induced slightly crosslinked poly(L-lactide) during extrusion

Molecular characterization and crystallization behavior of peroxide-induced slightly crosslinked poly(L-lactide) during extrusion

Physical and mechanical properties of PLA, and their functions in widespread applications — A comprehensive review

Reactive extrusion of poly(L‐lactic acid) with glycidol

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