Effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws

Poly(lactic acid) (PLA) attracts much attention as a typical biodegradable and biocompatible polymer, because it degrades to nontoxic lactic acid through non-enzymatic hydrolytic degradation. Processing of PLA bone fixation devices have been investigated to improve their mechanical properties. Among...

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Autores principales:	Masato SAKAGUCHI, Satoshi KOBAYASHI
Formato:	article
Lenguaje:	EN
Publicado:	The Japan Society of Mechanical Engineers 2016
Materias:	bone fixation device poly(lactic acid) orientation mechanical property hydrolysis in vitro Mechanical engineering and machinery TJ1-1570
Acceso en línea:	https://doaj.org/article/0733b013667944e08839c26a5ec30774
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spelling	oai:doaj.org-article:0733b013667944e08839c26a5ec307742021-11-26T06:40:17ZEffects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws2187-974510.1299/mej.15-00629https://doaj.org/article/0733b013667944e08839c26a5ec307742016-02-01T00:00:00Zhttps://www.jstage.jst.go.jp/article/mej/3/2/3_15-00629/_pdf/-char/enhttps://doaj.org/toc/2187-9745Poly(lactic acid) (PLA) attracts much attention as a typical biodegradable and biocompatible polymer, because it degrades to nontoxic lactic acid through non-enzymatic hydrolytic degradation. Processing of PLA bone fixation devices have been investigated to improve their mechanical properties. Among fixations, screws are referred as one of the most general bone fixation device. The purpose of the present study is to clarify the effect of initial higher-order structure on degradation behavior and associated mechanical properties for self-reinforced PLA screws. PLA screws were prepared through a series of routes including casting extrusion drawing and forging. These screws were immersed in phosphate buffer solution (PBS) for 0, 8, 16 and 24 weeks, and orientation function, crystallinity, molecular weight and shear strength were measured. As a result, initial shear strength increased and degradation ratio decreased with orientation. This is due to lower water absorption caused by orientation crystallization. Shear strength decreased approximately 15 % at least with 24 weeks immersion. The results of the crystallinity showed that the screws were selectively hydrolyzed in amorphous region. This fact suggested that shear strength retention depends on hydrolysis in amorphous region. Initial shear strength for extrusion ratio (ER) 2 is the highest although the orientation function is the lowest. And the strength rapidly decreased with 8 weeks immersion. This might be due to hydrolysis of oriented tie chains. Although β crystals emerged only at ER 4, there was not clear difference in molecular weights and shear strength. This result suggested that the crystal form has little effects on degradation behavior and mechanical properties.Masato SAKAGUCHISatoshi KOBAYASHIThe Japan Society of Mechanical Engineersarticlebone fixation devicepoly(lactic acid)orientationmechanical propertyhydrolysisin vitroMechanical engineering and machineryTJ1-1570ENMechanical Engineering Journal, Vol 3, Iss 2, Pp 15-00629-15-00629 (2016)
institution	DOAJ
collection	DOAJ
language	EN
topic	bone fixation device poly(lactic acid) orientation mechanical property hydrolysis in vitro Mechanical engineering and machinery TJ1-1570
spellingShingle	bone fixation device poly(lactic acid) orientation mechanical property hydrolysis in vitro Mechanical engineering and machinery TJ1-1570 Masato SAKAGUCHI Satoshi KOBAYASHI Effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws
description	Poly(lactic acid) (PLA) attracts much attention as a typical biodegradable and biocompatible polymer, because it degrades to nontoxic lactic acid through non-enzymatic hydrolytic degradation. Processing of PLA bone fixation devices have been investigated to improve their mechanical properties. Among fixations, screws are referred as one of the most general bone fixation device. The purpose of the present study is to clarify the effect of initial higher-order structure on degradation behavior and associated mechanical properties for self-reinforced PLA screws. PLA screws were prepared through a series of routes including casting extrusion drawing and forging. These screws were immersed in phosphate buffer solution (PBS) for 0, 8, 16 and 24 weeks, and orientation function, crystallinity, molecular weight and shear strength were measured. As a result, initial shear strength increased and degradation ratio decreased with orientation. This is due to lower water absorption caused by orientation crystallization. Shear strength decreased approximately 15 % at least with 24 weeks immersion. The results of the crystallinity showed that the screws were selectively hydrolyzed in amorphous region. This fact suggested that shear strength retention depends on hydrolysis in amorphous region. Initial shear strength for extrusion ratio (ER) 2 is the highest although the orientation function is the lowest. And the strength rapidly decreased with 8 weeks immersion. This might be due to hydrolysis of oriented tie chains. Although β crystals emerged only at ER 4, there was not clear difference in molecular weights and shear strength. This result suggested that the crystal form has little effects on degradation behavior and mechanical properties.
format	article
author	Masato SAKAGUCHI Satoshi KOBAYASHI
author_facet	Masato SAKAGUCHI Satoshi KOBAYASHI
author_sort	Masato SAKAGUCHI
title	Effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws
title_short	Effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws
title_full	Effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws
title_fullStr	Effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws
title_full_unstemmed	Effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws
title_sort	effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws
publisher	The Japan Society of Mechanical Engineers
publishDate	2016
url	https://doaj.org/article/0733b013667944e08839c26a5ec30774
work_keys_str_mv	AT masatosakaguchi effectsofinitialcrystallinityandmolecularorientationonhydrolysisandmechanicalpropertiesofselfreinforcedpolylacticacidscrews AT satoshikobayashi effectsofinitialcrystallinityandmolecularorientationonhydrolysisandmechanicalpropertiesofselfreinforcedpolylacticacidscrews
_version_	1718409698807382016

Effects of initial crystallinity and molecular orientation on hydrolysis and mechanical properties of self-reinforced poly(lactic acid) screws

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