A spectroscopic approach to assess transport properties of water vapor in PLA

Santis, Felice De; Gorrasi, Giuliana; Pantani, Roberto

doi:10.1016/j.polymertesting.2015.03.015

Cited by 12 publications

(5 citation statements)

References 16 publications

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“…The D -value reported in the literature (0.7 × 10 −7 cm 2 /s by gravimetry) (De Santis et al, 2015) is found in good agreement with the present spectroscopic determinations; an increasing trend of D with the water vapor pressure is also noted in Figure 5, which indicates that the mutual diffusivity coefficient is a growing function of the penetrant concentration.…”

Section: Results and Discussion Ftir Spectroscopysupporting

confidence: 92%

Sorption of Water Vapor in Poly(L-Lactic Acid): A Time-Resolved FTIR Spectroscopy Investigation

Pannico

Manna

2019

Front. Chem.

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In this contribution the sorption of water vapor in Poly(L-lactic acid) (PLLA) was studied by time-resolved FTIR spectroscopy. The collected FTIR data were analyzed by complementary approaches such as difference spectroscopy, two-dimensional correlation spectroscopy (2D-COS), and least-squares curve-fitting analysis which provided information about the overall diffusivity, the nature of the molecular interactions among the polymer and the penetrant and the dynamics of the various molecular species. The diffusion coefficient were evaluated as a function of vapor activity and were found in good agreement with previously reported values. The system showed a Fickian behavior with diffusivity increasing with penetrant concentration. Two distinct water species (first-shell and second-shell layers) were detected and quantified by coupling FTIR and gravimetric measurements.

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Section: Results and Discussion Ftir Spectroscopysupporting

confidence: 92%

Sorption of Water Vapor in Poly(L-Lactic Acid): A Time-Resolved FTIR Spectroscopy Investigation

Pannico

Manna

2019

Front. Chem.

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“…Analysis of chemical changes were monitored by Fourier Transform Infrared Spectroscopy (FTIR) in a Thermo Nicolet, model IS10 instrument, on prepared films by the KBr pellet method, in the wave number range of 4000 to 400 cm − 1 . Lactic acid index ( I LA ) was calculated as the ratio between band surfaces A 1 (3200 cm − 1 ) and A 2 at 750 cm − 1 , which is considered one of the PLA bands [eq. ].…”

Section: Methodsmentioning

confidence: 99%

“…The band at 3200 cm −1 can be credited to the formation of lactic acid and/or pyruvic acid as hydrolysis products, an indication of PLA degradation. The absence of a large, strong intensity band in the region of 3700–3050 cm −1 (OH group stretching, which is characteristic of carboxylic acid and alcohol which make up lactic acid) evidences the absence of PLA hydrolysis products such as lactic acid and/or pyruvic acid …”

Section: Methodsmentioning

confidence: 99%

Degradation of PLA and PLA in composites with triacetin and buriti fiber after 600 days in a simulated marine environment

Pelegrini

Donazzolo

Brambilla

et al. 2015

J of Applied Polymer Sci

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Poly(lactic acid) (PLA), the polymer object of this study, degrades by a biotic process after an abiotic hydrolysis process. Its degradation was evaluated after 600 days of exposure in a simulated marine environment (SME), as buriti fiber-reinforced composites having triacetin as coupling agent. Composites were obtained by extrusion and films were produced by compression molding. After between 60 and 600 days of exposure, PLA had a weight loss of 2.5%, PLA/T of 1.5%, and 10-12% of weight loss for PLA/B and PLA/B/T, respectively. PLA intercalates reduction, increase, and decrease of its crystallinity attributed to hydrolysis (up to 15 days), impairment of amorphous segments (45 days), and loss of integrity of the matrix (100-600 days), respectively. In the PLA/T composites, triacetin inhibited the diatom colonization process, having its crystallinity values increased after nearly 100 days of exposure with subsequent reduction. For samples with buriti fiber, changes in crystallinity were attributed to absorption of water and exposure of matrix amorphous segments. PLA degradation in a SME is evidently favored by the use of natural fibers since they make easier water access to the matrix and colonization by the protists group, diatoms, showing that the polymer can have reduced postuse shelf life as composites, with benefits while in use and at the same time post-use environmental benefits. Triacetin inhibits PLA colonization and degradation up to 45 days after exposure, after which it no longer influences the degradation process. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43290.

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“…We recognize that diffusivity is often evaluated based on the evolution of space-averaged water concentration with time, making it an apparent value. Other techniques, such as time domain–nuclear magnetic resonance [ 47 ] and in situ time-resolved Fourier transform infrared spectroscopy [ 48 ], calculate the water diffusion coefficient from water distribution in space, which can provide true diffusivity [ 49 ]. We believe that examining the discrepancy we observed between apparent and true diffusivities is the first step toward future research.…”

Section: Discussionmentioning

confidence: 99%

Discrepancy of Effective Water Diffusivities Determined from Dynamic Vapor Sorption Measurements with Different Relative Humidity Step Sizes: Observations from Cereal Materials

Zhao

Wei

Wang

et al. 2023

Foods

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Water diffusivity, a critical parameter for cereal processing design and quality optimization, is usually concentration-dependent. dynamic vapor sorption (DVS) system provides an approach to establishing the relationship between water concentration and diffusivity. However, the usual relative humidity (RH) jump during practical sorption processes is usually greater than that adopted in DVS measurements. Water vapor sorption kinetics of glutinous rice grains, glutinous rice flour and wheat flour dough films were measured using the DVS system to verify if varying RH step sizes can obtain identical diffusivities within the same range. The effective diffusivities were determined according to Fick’s second law. The results revealed that increasing RH step size led to a higher estimated diffusivity, regardless of whether the water concentration gradient or potential chemical gradient was considered a driving force for water diffusion. This finding was further confirmed by a linear RH scanning DVS measurement. The water concentration-dependent diffusivity obtained from a multi-step DVS measurement, according to Fick’s second law, will overestimate the required time for practical cereal drying or adsorption. Thus, this paradoxical discrepancy needs a new mass transfer mechanism to be explained.

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A spectroscopic approach to assess transport properties of water vapor in PLA

Cited by 12 publications

References 16 publications

Sorption of Water Vapor in Poly(L-Lactic Acid): A Time-Resolved FTIR Spectroscopy Investigation

Sorption of Water Vapor in Poly(L-Lactic Acid): A Time-Resolved FTIR Spectroscopy Investigation

Degradation of PLA and PLA in composites with triacetin and buriti fiber after 600 days in a simulated marine environment

Discrepancy of Effective Water Diffusivities Determined from Dynamic Vapor Sorption Measurements with Different Relative Humidity Step Sizes: Observations from Cereal Materials

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