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Medical grade polylactide, copolyesters and polydioxanone: Rheological properties and melt stability
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymer Technology.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.ORCID iD: 0000-0002-1922-128X
2018 (English)In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 72, p. 214-222Article in journal (Refereed) Published
Abstract [en]

Rheological measurements have shown that lactide-based copolymers with L-lactide content between 50 and 100 mol% with varying comonomers, as well as polydioxanone (PDX), can be used in additive manufacturing analogously to poly(L-lactide) (PLLA) if their melt behaviour are balanced. The results indicate that copolymers can be melt processed if the temperature is adjusted according to the melting point, and parameters such as the speed are tuned to conteract the elastic response. Small amplitude oscillatory shear (SAOS) rheology, thermal and chemical characterisation allowed us to map the combined effect of temperature and frequency on the behaviour of six degradable polymers and their melt stability. Values of complex viscosity and Tan delta obtained through nine time sweeps by varying temperature and frequency showed that the molecular structure and the number of methylene units influenced the results, copolymers of L-lactide with D-Lactide (PDLLA) or glycolide (PLGA) had an increased elastic response, while copolymers with trimethylene carbonate (PLATMC) or epsilon-caprolactone (PCLA) had a more viscous behaviour than PLLA, with respect to their relative melting points. PDLLA and PLGA require an increased temperature or lower speed when processed, while PLATMC and PCLA can be used at a lower temperature and/or higher speed than PLLA. PDX showed an increased viscosity compared to PLLA but a similar melt behaviour. Negligible chain degradation were observed, apart from PLGA.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD , 2018. Vol. 72, p. 214-222
Keywords [en]
Degradable polymers, Melt rheology, Polyesters, Melt stability and polylactide
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-241208DOI: 10.1016/j.polymertesting.2018.10.007ISI: 000454464600025Scopus ID: 2-s2.0-85055196906OAI: oai:DiVA.org:kth-241208DiVA, id: diva2:1280398
Note

QC 20190118

Available from: 2019-01-18 Created: 2019-01-18 Last updated: 2022-06-26Bibliographically approved
In thesis
1. Degradable copolymers in additive manufacturing: controlled fabrication of pliable scaffolds
Open this publication in new window or tab >>Degradable copolymers in additive manufacturing: controlled fabrication of pliable scaffolds
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [sv]

Inom vävnadsregenerering är produktionen av väldefinieradematriser med en porös arkitektur av nedbrytbara polymerer av stortintresse, dessa kan nu skapas genom additiva tillverkningsprocesser. Vidadditiv tillverkning krävs ett smalt munstycke för att skapa detaljrikastrukturer och detta ställer krav på att de reologiska egenskapernaanpassat. Lägre viskositet av smältan gör de lättare att använda, men enhög molmassa krävs för tillverka matriser där de mekaniska egenskapernakan bibehållas under tiden som krävs för vävnadsregenerering. Ytterligareen utmaning uppstår när nedbrytbara polymerer används i smältbaseradadditiva tillverkningsprocesser är att termisk nedbrytning ofta reducerarmolmassan redan under produktionsfasen. För att kunna användanedbrytbara polymerer av medicinsk kvalitet i smältbaserad additivtillverkning och samtidigt minimera den termiska nedbrytningen har, idenna avhandling, reologiska fingeravtryck av nedbrytbara syntetiskapolymerer med medicinsk kvalitet använts för att bestämmaprocessparametrar. Termisk nedbrytning beroende av processparamaterar har analyserats och minimeras i två smältbaserade additivatillverkningsprocesser.En additiv tillverkningsprocess var designad där nedbrytbarapolymerer av hög molmassa kunde användas utan termisk nedbrytning närprocessparametrar hade valts utifrån polymerens egenskaper. Kunskapenom användningen av dessa polymerer inom additiv tillverkning kundeappliceras på en sampolymer som utvecklats inom forskningsgruppen förmjukvävnad, poly(ε-kaprolakton-co-p-dioxanon) för att skapa böjbaramatriser. Genom att använda reologisk analys och polymerkarakteriseringerhölls processparametrar som möjliggjorde additiv tillverkning utantermisk nedbrytning. I tillägg till val av polymer och processparametrar såkan mekaniska egenskaper också styras av den strukturella designen.Poly(ε-kaprolakton) användes som modellmaterial för att reducerastyvheten med hjälp av designen, resultatet visade att det var möjligt medmer än en faktor 10 och mjuka böjbara matriser skapades.

Abstract [en]

In tissue engineering, the production of well-defined scaffolds with a porous architecture from degradable polymers is of great interest. Detailed designs have become feasible through the development of additive manufacturing. A small nozzle size is needed to obtain detailed scaffold structures, and careful control of the rheological properties is therefore required during production. A lower viscosity of the melt allows for easier printability, but a high molar mass is required to produce scaffolds that can retain mechanical properties over the time needed for tissue regeneration. An additional challenge of using degradable polymers with high molar mass in any melt-based processing is that thermal degradation can reduce the molar mass during the production stage. To utilise medical grade degradable polymers whilst limiting the thermal degradation a rheological analysis of the most commonly used commercial medical-grade degradable synthetic polymers was performed. Their rheological behaviours aided in setting process parameters for two different melt-based additive manufacturing routes. The variation in thermal degradation in the two routes was assessed, and the parameters were adjusted to minimise it.

A nondegradative additive manufacturing method was designed, and knowledge regarding printability was developed based on rheological analysis and polymer characterisation methods. This knowledge was applied to the copolymer poly(e-caprolactone-co-p-dioxanone) developed within the group to fabricate pliable scaffolds for tissue engineering with an increased rate of hydrolysis in comparison to poly(e-caprolactone). In addition to the selection of the polymer and process parameters, the mechanical properties were also controlled through the structural design. Poly(e-caprolactone) was used as a model material to show how the mechanical properties of scaffolds could be controlled based on the design solely. The results showed that the stiffness could be reduced by more than a factor of 10 through tuning of the design, resulting in soft pliable scaffold structures.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2021. p. 86
Series
TRITA-CBH-FOU ; 2021:7
National Category
Polymer Technologies
Research subject
Fibre and Polymer Science
Identifiers
urn:nbn:se:kth:diva-290799 (URN)978-91-7873-778-9 (ISBN)
Public defence
2021-03-26, https://kth-se.zoom.us/j/68298579714, Stockholm, 10:00 (English)
Opponent
Supervisors
Projects
Fibre and Polymer Science
Funder
Swedish Foundation for Strategic Research , RMA15-0010
Note

QC 2021-02-23

Available from: 2021-02-23 Created: 2021-02-23 Last updated: 2022-06-25Bibliographically approved

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Ahlinder, AstridFuoco, TizianaFinne Wistrand, Anna

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