The effect of molecular weight and hydrolysis degree of poly(vinyl alcohol)(PVA) on the thermal and mechanical properties of poly(lactic acid)/PVA blends

Restrepo, Iván; Medina, Carlos; Meruane, Viviana; Akbari‐Fakhrabadi, Ali; Flores, Paulo; Rodríguez-Llamazares, Saddys

doi:10.1590/0104-1428.03117

Cited by 57 publications

(48 citation statements)

References 31 publications

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“…As it can be seen from Figure 2 , the curves of PHSu, PLA and the 3 copolymers do not present the same pattern, with the curve of PHSu starting first to lose mass at around 180–200 °C, but the main mass loss step is shifted to higher temperatures compared to the other samples. PLA presents one mass loss step which can be simultaneously seen in the mass (%) and in the DTG curve and is associated with the loss of ester groups by unzipping depolymerization [ 38 ]. As far as copolymers are concerned, PLA-b-PHSu95/05 follows quite the same pattern as pure PLA, as the content of PHSu is quite small.…”

Section: Resultsmentioning

confidence: 99%

Thermal Degradation Mechanism and Decomposition Kinetic Studies of Poly(Lactic Acid) and Its Copolymers with Poly(Hexylene Succinate)

2021

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Ιn this work, new block poly(lactic acid)-block-poly(hexylene succinate) (PLA-b-PHSu) copolymers, in different mass ratios of 95/05, 90/10 and 80/20 w/w, are synthesized and their thermal and mechanical behavior are studied. Thermal degradation and thermal stability of the samples were examined by Thermogravimetric Analysis (TGA), while thermal degradation kinetics was applied to better understand this process. The Friedman isoconversional method and the “model fitting method” revealed accurate results for the activation energy and the reaction mechanisms (nth order and autocatalysis). Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS) was used to provide more details of the degradation process with PHSu’s mechanism being the β-hydrogen bond scission, while on PLA the intramolecular trans-esterification processes domains. PLA-b-PHSu copolymers decompose also through the β-hydrogen bond scission. The mechanical properties have also been tested to understand how PHSu affects PLA’s structure and to give more information about this new material. The tensile measurements gave remarkable results as the elongation at break increases as the content of PHSu increases as well. The study of the thermal and mechanical properties is crucial, to examine if the new material fulfills the requirements for further investigation for medical or other possible uses that might come up.

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Section: Resultsmentioning

confidence: 99%

Thermal Degradation Mechanism and Decomposition Kinetic Studies of Poly(Lactic Acid) and Its Copolymers with Poly(Hexylene Succinate)

2021

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“…The heating rate used was 10 °C/min, from 40 °C to 230 °C. To overcome the thermal history of the samples (interference from the samples’ previous thermal processing), the second heating cycle was used to obtain the glass transition temperature (Tg), the melting temperature, and the degree of crystallinity (Xc), calculated according to Equation (1) [ 46 ]. The Xc calculated was based on relativity to the melting of PVA crystallites, where ΔH is the enthalpy of the sample peak at ~220 °C, w t is the amount of PVA in the sample, and ΔH* is the theoretical enthalpy of 100% crystalline PVA (138.6 J/g) [ 47 ].…”

Section: Methodsmentioning

confidence: 99%

Physically Cross-Linked Gels of PVA with Natural Polymers as Matrices for Manuka Honey Release in Wound-Care Applications

Santos

Moreira²,

Carvalho

et al. 2019

Materials

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Manuka honey is a well-known natural material from New Zealand, considered to have properties beneficial for burn treatment. Gels created from polyvinyl alcohol (PVA) blended with natural polymers are potential burn-care dressings, combining biocompatibility with high fluid uptake. Controlled release of manuka honey from such materials is a possible strategy for improving burn healing. This work aimed to produce polyvinyl alcohol (PVA), PVA–sodium carboxymethylcellulose (PVA-CMC), PVA–gelatin (PVA-G), and PVA–starch (PVA-S) cryogels infused with honey and to characterize these materials physicochemically, morphologically, and thermally, followed by in vitro analysis of swelling capacity, degradation/weight loss, honey delivery kinetics, and possible activity against Staphylococcus aureus. The addition of honey to PVA led to many PVA crystals with defects, while PVA–starch–honey and PVA–sodium carboxymethylcellulose–honey (PVA-CMC-H) formed amorphous gels. PVA-CMC presented the highest swelling degree of all. PVA-CMC-H and PVA–gelatin–honey presented the highest swelling capacities of the honey-laden samples. Weight loss/degradation was significantly higher for samples containing honey. Layers submitted to more freeze–thawing cycles were less porous in SEM images. With the honey concentration used, samples did not inhibit S. aureus, but pure manuka honey was bactericidal and dilutions superior to 25% honey were bacteriostatic, indicating the need for higher concentrations to be more effective.

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“…The PVA-only fibers and PVA composite fibers prepared in this work exhibited high crystallinity compared with PVA films [22] because they were highly drawn. The XRD peaks at about 11.4°, 19.7°, and 22.7° were assigned to the crystal faces of (100), (101), and (200), respectively [23,24]. The XRD patterns of the PVA/EOG composite fibers were similar to that of the PVA-only ones, indicating that the EOG incorporation did not decrease the fiber crystallinity.…”

Section: Resultsmentioning

confidence: 99%

Facile Fabrication of Polyvinyl Alcohol/Edge-Selectively Oxidized Graphene Composite Fibers

2019

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Graphene derivatives are effective nanofillers for the enhancement of the matrix mechanical properties; nonetheless, graphene oxide (GO), reduced GO, and exfoliated graphene all present distinct advantages and disadvantages. In this study, polyvinyl alcohol (PVA) composite fibers have been prepared using a recently reported graphene derivative, i.e., edge-selectively oxidized graphene (EOG). The PVA/EOG composite fibers were simply fabricated via conventional wet-spinning methods; thus, they can be produced at the commercial level. X-ray diffractometry, scanning electron microscopy, and two-dimensional wide-angle X-ray scattering analyses were conducted to evaluate the EOG dispersibility and alignment in the PVA matrix. The tensile strength of the PVA/EOG composite fibers was 631.4 MPa at an EOG concentration of 0.3 wt %, which is 31.4% higher compared with PVA-only fibers (480.6 MPa); compared with PVA composite fibers made with GO, which is the most famous water-dispersible graphene derivative, the proposed PVA/EOG ones exhibited about 10% higher tensile strength. Therefore, EOG can be considered an effective nanofiller to enhance the strength of PVA fibers without additional thermal or chemical reduction processes.

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The effect of molecular weight and hydrolysis degree of poly(vinyl alcohol)(PVA) on the thermal and mechanical properties of poly(lactic acid)/PVA blends

Cited by 57 publications

References 31 publications

Thermal Degradation Mechanism and Decomposition Kinetic Studies of Poly(Lactic Acid) and Its Copolymers with Poly(Hexylene Succinate)

Thermal Degradation Mechanism and Decomposition Kinetic Studies of Poly(Lactic Acid) and Its Copolymers with Poly(Hexylene Succinate)

Physically Cross-Linked Gels of PVA with Natural Polymers as Matrices for Manuka Honey Release in Wound-Care Applications

Facile Fabrication of Polyvinyl Alcohol/Edge-Selectively Oxidized Graphene Composite Fibers

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