Mechanical performance of polymer systems: The relation between structure and properties

Meijer, Heh Han; Govaert, Leon Le

doi:10.1016/j.progpolymsci.2005.06.009

Cited by 380 publications

(291 citation statements)

References 83 publications

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“…However, another reason is probably related to the intrinsic deformation behaviour of PLA. Govaert and co-workers [17] showed that PLA exhibits a very strong post-yield softening behaviour together with virtually no strain hardening, the combination of both leading to strong localization of deformation and brittle fracture [18,19]. Mechanical pre-deformation as a result of drawing will lead to an increase in strain hardening due to orientation of crystalline material, which will alter the subtle interplay between strain softening and strain hardening.…”

Section: The Influence Of Drawing On Mechanical Properties Of Plla Tapesmentioning

confidence: 99%

The Influence of Solid-State Drawing on Mechanical Properties and Hydrolytic Degradation of Melt-Spun Poly(Lactic Acid) (PLA) Tapes

Mai

Bilotti

et al. 2015

Fibers

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Abstract:The influence of solid-state drawing on the morphology of melt-spun poly(L-lactic acid) (PLLA) tapes, and the accompanying changes in mechanical and degradation behaviour have been studied. Mechanical properties are found to be strongly dependent on both applied draw ratio and drawing temperature. Moduli of these highly oriented tapes are significantly increased compared to as-extruded tapes at both ambient and elevated temperatures. Interestingly, drawing leads to a significant increase in elongation to break (~3 times) and toughness (~13 times) compared to as-extruded tapes. Structural and morphological characterization indicates strain-induced crystallization as well as an increase in orientation of the crystalline phase at small strains. Upon further stretching, an "overdrawing" regime is observed, with decreased crystalline orientation due to the breakage of existing crystals. For fixed draw ratios, a significant increase in Young's modulus and tensile strength is observed with increasing drawing temperature, due to a higher crystallinity and orientation obtained for tapes drawn at higher temperatures. FT-IR results indicate no crystal transformation after drawing, with the α-form being observed in all tapes. Hydrolytic degradability of PLLA was significantly reduced by solid-state drawing.

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Section: The Influence Of Drawing On Mechanical Properties Of Plla Tapesmentioning

confidence: 99%

The Influence of Solid-State Drawing on Mechanical Properties and Hydrolytic Degradation of Melt-Spun Poly(Lactic Acid) (PLA) Tapes

Mai

Bilotti

et al. 2015

Fibers

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“…It is possible that toughness is equivalent to delocalization of stress. 37 The incorporation of heterogeneities into polymeric materials should be expected during molding. In addition, microor nano-scale cracks or voids might arise from secondary crystallization 38 and mechanical strains.…”

Section: Microscopic Observationmentioning

confidence: 99%

The toughening effect of a small amount of poly(ɛ-caprolactone) on the mechanical properties of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/PCL blend

Katsumata

Saitō

Fang

et al. 2011

Polym J

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To improve the mechanical properties of bacterial poly(3-hydroxybutyrate) [P(3HB)] and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HH)], the materials were blended with poly(e-caprolactone) (PCL). The P(3HB-co-7 mol% 3HH) cast film and the P(3HB-co-11 mol% 3HH) melt-pressed film show brittleness after aging, although unaged samples show ductile behavior. However, the addition of a small amount of PCL was found to greatly improve the toughness of the P(3HB-co-7 mol% 3HH) cast film and the P(3HB-co-11 mol% 3HH) melt-pressed film. Reduction in the whitening of the elongated P(3HB-co-7 mol% 3HH) film by blending with PCL indicates that a transition in the deformation mechanism of the film was induced. In P(3HB-co-11 mol% 3HH)/PCL melt-pressed films, a cloud of craze initiation created by the dispersed PCL was observed. Differential scanning calorimetry thermograms and scanning electron microscopy images of the blended films indicated that finely dispersed PCL, the crystallization of which was restricted, and/or voids formed during preparation contribute to the delocalization of the applied stress and ductile deformation of P(3HB-co-3HH) films. In conclusion, the transition in the deformation mechanisms and the delocalization of the applied stress are expected to be important for enhancing the toughness of aged P(3HB-co-3HH)s, and blending with a small amount of PCL is a simple way to improve the mechanical properties of P(3HB-co-3HH)s. Polymer Journal (2011) 43, 484-492; doi:10.1038/pj.2011.12; published online 23 February 2011Keywords: blend; mechanical property; polyhydroxyalkanoate; poly(e-caprolactone); tensile test INTRODUCTION Several kinds of polyhydroxyalkanoates (PHAs) are biosynthesized by various bacteria as energy-storage materials. 1-5 They may be produced from renewable natural resources and have biodegradability. Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HH)] is part of the PHA family. 6 Doi et al. 7 have found that the content of the 3HH unit greatly affected the thermal and mechanical properties of P(3HB-co-3HH), but had little effect on the crystalline structure of 3HB-rich P(3HB-co-3HH)s because of the formation of the P(3HB)-homopolymer-type crystalline phase and the exclusion of the 3HH unit from the crystalline lattice. P(3HB-co-3HH) was found to show improved mechanical properties and thermal plasticity over those of known PHAs. 8,9 One of the notable advantages of P(3HB-co-3HH)s is their adjustable mechanical properties, from soft to hard material, depending on the comonomer-unit composition; this allows for the tailoring of P(3HB-co-3HH) to various societal applications, such as in green and sustainable polymeric materials.However, P(3HB-co-3HH) becomes brittle after aging at room temperature, thus restricting its practical applications. Although

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“…Such structural heterogeneities are more marked in heterogeneous materials including rocks 13 , composites 32 , and multiphase alloys 23 . Similarly, crazing observed in brittle polymers at highly stressed regions has been associated with molecular inhomogeneities 33,34 . Lawn 35 introduced a concept of "energy sinks" (e.g.…”

Section: (B)mentioning

confidence: 95%

Origin of compression-induced failure in brittle solids under shock loading

Huang

Liu

et al. 2015

Phys. Rev. B

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The origin of compression-induced failure in brittle solids has been a subject of debate. Using in situ, high-speed, strain field mapping of a representative material, polymethylmethacrylate, we reveal that shock loading leads to heterogeneity in compressive strain field, which in turn gives rise to localized lateral tension and shear through Poisson's effects, and subsequently, localized microdamage. A failure wave nucleates from the impact surface and its propagation into the microdamage zone is self-sustained, and triggers interior failure. Its velocity increases with increasing shock strength and eventually approaches the shock velocity. The seemingly puzzling phenomena observed in previous experiments, including incubation time, failure wave velocity variations, and surface roughness effects, can all be explained consistently with nucleation and growth of microdamage, and the effects of loading strength and preexisitng defects.

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Mechanical performance of polymer systems: The relation between structure and properties

Cited by 380 publications

References 83 publications

The Influence of Solid-State Drawing on Mechanical Properties and Hydrolytic Degradation of Melt-Spun Poly(Lactic Acid) (PLA) Tapes

The Influence of Solid-State Drawing on Mechanical Properties and Hydrolytic Degradation of Melt-Spun Poly(Lactic Acid) (PLA) Tapes

The toughening effect of a small amount of poly(ɛ-caprolactone) on the mechanical properties of the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/PCL blend

Origin of compression-induced failure in brittle solids under shock loading

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