1,720,956 research outputs found
Micromechanical analysis and fracture mechanics of Poly(lactic acid) (PLA)/Polycaprolactone (PCL) binary blends
Full text linkEven Poly(lactic acid)/polycaprolactone (PLA/PCL) blends have been studied in literature, the deformation mechanism that is related to the toughness increment with respect to pure PLA has not been investigated in detail. The novelty of this work is to understand in depth the correlation between the micromechanical deformation processes occurring in PLA/PCL blends to the macromechanical properties, their morphology and their fracture mechanism.PLA/PCL blends containing increasing amount of PCL (from 10 up to 40 wt%) were produced. A novel characterization approach, not yet investigated for these blends, was carried out by dilatometric uniaxial tests using a videoextensometer. The shape of the dilatometric curves coupled with SEM analysis revealed how changing the PCL amount different concurrent micromechanical deformation processes occurred. When 10 wt% of PCL was added only particles debonding occurred leading to lower enhancement of elongation at break; at 20 wt% both debonding and voids growth along the tensile direction occurred, while at 40 wt% of PCL shear yielding was predominant that lead to a great enhancement of the elongation at break. The PLA/PCL blends capability to absorb energy at slow rate, was evaluated by the elasto-plastic fracture approach based on the ESIS load separation criterion. The results obtained was then correlated with the final blend morphology
Poly(lactic acid) (PLA) properties as a consequence of poly(butylene adipate-co-terephtahlate) (PBAT) blending and acetyl tributyl citrate (ATBC) plasticization
No full textThis study was aimed at the modulation of poly(lactic acid) (PLA) properties by the addition of both a low-molecular-weight plasticizer, acetyl tributyl citrate (ATBC), and a biodegradable aliphatic–aromatic copolyester, poly(butylene adipate-co-terephthalate) (PBAT).
PLA/PBAT, PLA/ATBC, and PLA/PBAT/ATBC mixtures with 10–35 wt % ATBC and/or PBAT were prepared in a discontinuous laboratory mixer, compression-molded, and characterized by thermal, morphological, and mechanical tests to evaluate the effect of the concentration of either the plasticizer or copolyester on the final material flexibility. Materials with modulable properties, Young’s modulus in the range 100–3000 MPa and elongation at break in the range 10–300%, were obtained. Moreover, thermal analysis showed a preferential solubilization of ATBC in the PBAT phase. Gas permeability tests were also performed to assess possible use in food packaging applications. The results are discussed with particular emphasis toward the effects of plasticization on physical blending in the determination of the phase morphology and final properties
BIOCOMPOSITES BASED ON POLYESTERS AND NATURAL FIBRES
Full text linkThe use of “bio-polymers” for the production of “bio-plastic” and “Bio based composites” has became
worldwide an assessed priority with the aim of reducing dependence from petro sources, and handle the
concern for disposal of waste generated from not degradable plastics. Their use has attracted interest of
various application sectors ranging from packaging to automotive components and other high value
applications, and has been from many year a main topic of research activity in our unit, bound to several
related European and Regional projects (PHA- ARFAS 2007-2013). Advantages of natural fibres on
conventional reinforcements such as glass and aramid fibres are their relative cheapness, ability to recycle,
and competition with them in terms of strength per weight of material. However the strength of the bond
between fibres and matrix is substantial for the best mechanical performances of a composite. Many
factors interacting with each other affect the complex process of the fibre/matrix adhesio
Wheat bran addition as potential alternative to control the plasticizer migration into PLA/PBSA blends
No full textWheat bran (WB) was investigated as potential filler for controlling the plasticizer migration in poly(lactic acid) (PLA)/poly(butylene succinate adipate) (PBSA) binary blends (with 60 wt.% of PLA and 40 wt.% of PBSA). The migration process of three different biobased and biodegradable plasticizers [Triacetin (TA), acetyl tri-n-butyl citrate (ATBC) and oligomeric lactic acid (OLA)] was investigated adding them at a fixed amount of 10 wt.%. TA revealed the greater mass loss over the time as confirmed from the calculation of the diffusion coefficients. The addition of WB in different amount (from 10 to 30 wt.%) revealed its tendency to influence the diffusion process in a manner strictly dependent on its content. The great dimensions of the WB, however, weaken the material suggesting to adopt a preliminary dimensional reduction of the filler to mitigate the negative effect observed on the mechanical properties. From this study emerged the WB potential to be used as filler for controlling the plasticizer migration, thus suggesting a possible valorization of this waste byproduct in biobased and biodegradable materials
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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