Microhardness of PET-based liquid crystalline copolyesters: influence of the microstructure

Minkova, L.; Peneva, Y.

doi:10.1016/j.polymer.2003.07.004

Cited by 6 publications

(1 citation statement)

References 21 publications

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“…It also gives information about several bulk properties such as yield stress or elastic modulus 14. Several microhardness studies related to high crystallinity degree polymers15, 16 can be found in literature, but regarding polymers with low crystallinity degree, such as PLLA, the literature is more scarce9, 17, 18 and focuses specially on poly(ethylene terephthalate).…”

Section: Introductionmentioning

confidence: 99%

In vitro monitoring of surface mechanical properties of poly(L‐lactic acid) using microhardness

Saiz‐Arroyo

Wang

Rodríguez‐Pérez

et al. 2007

J of Applied Polymer Sci

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Poly(L-lactic acid) (PLLA) was immersed in a simulated body fluid (SBF) solution at 37.58C for distinct times. The variation of the surface mechanical properties of PLLA samples with immersion time was followed by microhardness. These measurements showed that PLLA microhardness decreased significantly ($ 60%) after only 30 days of immersion. The results were explained in terms of hydrolytic degradation of the samples. The dependence of microhardness with the applied dwell time was also analyzed. The creep curves were successfully described by a power law. A decrease of the creep constant k as the immersion time increased was found. Differential scanning calorimetry was also used to analyze the changes in the physical properties of PLLA, namely in crystallinity degree (X c ) and glass transition temperature (T g ), as a function of the immersion time in SBF. A significant variation in the crystallinity degree of PLLA, initially nearly amorphous (X c 5 9%), was detected after only 3 days of immersion (X c 5 37%). The interpretation of this behavior was based on the hydrolysis process suffered by PLLA.

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Section: Introductionmentioning

confidence: 99%

In vitro monitoring of surface mechanical properties of poly(L‐lactic acid) using microhardness

Saiz‐Arroyo

Wang

Rodríguez‐Pérez

et al. 2007

J of Applied Polymer Sci

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Hardness

Calleja

Flores

2011

Encyclopedia of Polymer Science and Technology

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A description of the hardness technique and its application to polymer systems is presented. The method is based on the local deformation produced on a material surface by an indenter upon application of a given load. Conventional methods based on the optical measure of the residual impression left behind upon load release represent a rather simple technique for a rapid evaluation of the surface mechanical properties. In the past two decades, depth‐sensing indentation devices based on the monitoring of the load and displacement throughout an indentation have progressively substituted traditional testers. Smaller loads can be applied capable of producing penetration depths in the nanoscale. Indentation hardness has nowadays gained widespread application in polymer science. Besides its aforementioned technical advantages, one has to add its extreme sensitivity to detect nanostructural changes occurring in polymer materials. Behind this ability is the intimate correlation between the mechanisms of local deformation and the polymer basic nanostructural entities. The present contribution intends to provide the reader a general overview of the state of the art of indentation hardness in relation to nanostructure and morphology in glassy and semicrystalline polymers including blends.

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