| 1. |
- Badia, J. D., et al.
(författare)
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Water absorption and hydrothermal performance of PHBV/sisal biocomposites
- 2014
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Ingår i: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 108, s. 166-174
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Tidskriftsartikel (refereegranskat)abstract
- The performance of biocomposites of poly(hydroxybutyrate-co-valerate) (PHBV) and sisal fibre subjected to hydrothermal tests at different temperatures above the glass transition of PHBV (T-H = 26, 36 and 46 degrees C) was evaluated in this study. The influences of both the fibre content and presence of coupling agent were focused. The water absorption capability and water diffusion rate were considered for a statistical factorial analysis. Afterwards, the physico-chemical properties of water-saturated biocomposites were assessed by Fourier-Transform Infrared Analysis, Size Exclusion Chromatography, Differential Scanning Calorimetry and Scanning Electron Microscopy. It was found that the water diffusion rate increased with both temperature and percentage of fibre, whereas the amount of absorbed water was only influenced by fibre content. The use of coupling agent was only relevant at the initial stages of the hydrothermal test, giving an increase in the diffusion rate. Although the chemical structure and thermal properties of water-saturated biocomposites remained practically intact, the physical performance was considerably affected, due to the swelling of fibres, which internally blew-up the PHBV matrix, provoking cracks and fibre detachment.
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| 2. |
- Camacho, W., et al.
(författare)
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Determination of moisture content in nylon 6,6 by near-infrared spectroscopy and chemometrics
- 2003
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 87:13, s. 2165-2170
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Tidskriftsartikel (refereegranskat)abstract
- The effects of moisture on the morphology and mechanical properties of polyamides have been extensively studied by a number of researchers. However, the assessment of water content in the resins has been carried out by thermal or thermogravimetric methods, which are destructive. In the present work partial least-squares (PLS) calibration models based on near-infrared (NIR) spectroscopy were produced in order to predict the moisture content of nylon 6,6. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the loss-on-drying (LOD) method were used as reference methods. TGA, LOD, DSC, and NIR analysis were performed in parallel, and the obtained data were used for multivariate calibration purposes. Data pretreatment techniques such as derivation and multiplicative scattering correction (MSC) successfully eliminated the baseline offset present in the raw spectra and compensated for differences in thickness and light scattering of the analyzed samples. Calibration models were validated by full cross validation with the help of a test set. A comparison of the prediction ability of PLS models based on pretreated data was also done. NIR spectroscopy is a rapid and nondestructive method for the determination of moisture in recycled nylon. The moisture content can be predicted with a RMSEP = 0.05 wt %.
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| 3. |
- Gil-Castell, O., et al.
(författare)
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Hydrothermal ageing of polylactide/sisal biocomposites. Studies of water absorption behaviour and Physico-Chemical performance
- 2014
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Ingår i: Polymer degradation and stability. - : Elsevier BV. - 0141-3910 .- 1873-2321. ; 108, s. 212-222
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Tidskriftsartikel (refereegranskat)abstract
- An accelerated hydrothermal degrading test was designed in order to analyse the synergic effect of water and temperature on PLA/sisal biocomposites with and without coupling agent. As well, the physicochemical properties of biocomposites were monitored along the hydrothermal test by means of Scanning Electron Microscopy, Size Exclusion Chromatography and Differential Scanning Calorimetry. The addition of fibre induced higher water absorption capability and promoted physical degradation, as observed in the surface topography. During the processing of biocomposites and throughout the hydrothermal ageing, a reduction of molecular weight due to chain scission was found. As a consequence, a faster formation of crystalline domains in the PIA matrix occurred the higher the amount of fibre was, which acted as a nucleating agent. Higher crystallinity was considered as a barrier against the advance of penetrant and a reduction in the diffusion coefficient was shown. The addition of coupling agent presented a different influence depending on the composition, showing an inflection point around 20% of sisal fibre.
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| 4. |
- Marti-Ferrer, F., et al.
(författare)
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Flour rice husk as filler in block copolymer polypropylene : Effect of different coupling agents
- 2006
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 99:4, s. 1823-1831
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Tidskriftsartikel (refereegranskat)abstract
- Flour rice husk (FRH) was employed as a filler in block copolymer polypropylene (PPB) in order to prepare polymer-based reinforced composites. Four coupling agents were selected to modify the surface of the rice husk in the composite materials, including two types of functionalized polymers [PP homopolymer grafted with maleic anhydride (MA-PP) and an elastomer styrene-ethylene-butadiene-styrene triblock copolymer grafted with MA (MA-SEBS)] and two bifunctional organometallic coupling agents (silane and titanate with linear low-density polyethylene as a carrier). The influence of each type of coupling agent on the interfacial bonding strength was studied by dynamic mechanical analysis, scanning electronic microscopy, and rheological tests. The results showed that strong interactions were formed between the coupling agents and the filler surface. The addition of a coupling agent with an elastomeric carrier (MA-SEBS) increased the loss tangent and reduced the storage modulus of the composite. A similar but less intense effect was observed for the titanate coupling agent. However, an antagonistic performance was obtained when MA-PP and silane were employed as coupling agents. In addition, when the percentage of MA-SEBS was increased, the impact properties of FRH/PPB blends were improved and the strength was reduced.
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| 5. |
- Valles-Lluch, A., et al.
(författare)
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Influence of water on the viscoelastic behavior of recycled nylon 6,6
- 2002
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 85:10, s. 2211-2218
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Tidskriftsartikel (refereegranskat)abstract
- Nylons are highly sensitive to moisture, as water molecules are able to form hydrogen-bonded complexes with nitrogen and oxygen from the amide functional groups. In recycled nylon 6,6, a higher absorbed moisture content can be detected in comparison to virgin material. Moisture uptake is manifested in chemical and physical properties, and has important technological consequences, so the relationship between them must be assessed. Differential scanning calorimetry (DSC) has been used to measure the water content of different samples and physical changes have been analyzed by means of dynamic mechanical thermal analysis (DMTA). The relaxation zones of the dynamic-mechanical relaxation spectra of the samples have been characterized according to the Fuoss-Kirkwood equation and with help of the deconvolution method.
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| 6. |
- Vilaplana, Francisco, et al.
(författare)
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Swelling behavior of PDMS-PMHS pervaporation membranes in ethyl acetate-water mixtures
- 2004
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 93:3, s. 1384-1393
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Tidskriftsartikel (refereegranskat)abstract
- Pervaporation composite membranes were prepared with a three-layer structure: a PP support, a PEI microporous structure, and a PDMS-PMHS selective layer. Swelling tests were performed in water, ethyl acetate, and four different ethyl acetate-water mixtures, to calculate the diffusional and swelling parameters. Moreover, the dynamic-mechanical properties of the membranes were obtained before and after the swelling experiments, and their relaxation spectra were characterized with the Fuoss-Kirkwood equation and analyzed in terms of the free volume parameter. It was found that the ethyl acetate possesses high affinity with the composite membranes and that the absorption of these small molecules substantially modifies the viscoelastic behavior and structure of the active layer. The combination of swelling experiments and the study of the mechanical relaxations proved to be an appropriate technique to investigate the behavior of pervaporation membranes immersed in different mixtures.
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| 7. |
- Badia, J. D., et al.
(författare)
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A statistical design of experiments for optimizing the MALDI-TOF-MS sample preparation of polymers. An application in the assessment of the thermo-mechanical degradation mechanisms of poly (ethylene terephthalate)
- 2011
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670 .- 1873-4324. ; 692:1-2, s. 85-95
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Tidskriftsartikel (refereegranskat)abstract
- The sample preparation procedure for MALDI-TOF MS of polymers is addressed in this study by the application of a statistical Design of Experiments (DoE). Industrial poly (ethylene terephthalate) (PET) was chosen as model polymer. Different experimental settings (levels) for matrixes, analyte/matrix proportions and concentrations of cationization agent were considered. The quality parameters used for the analysis were signal-to-noise ratio and resolution. A closer inspection of the statistical results provided the study not only with the best combination of factors for the MALDI sample preparation, but also with a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measure of PET stated that the best combination of factors and levels was the following: matrix (dithranol), proportion analyte/matrix/cationization agent (1/15/1, V/V/V), and concentration of cationization agent (2 g L-1). In a second part, multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PET under mechanical recycling. The application of MALDI-TOF-MS showed that thermo-mechanical degradation primarily affected initially predominant cyclic species. Several degradation mechanisms were proposed, remarking intramolecular transesterification and hydrolysis. The ether links of the glycol unit in PET were shown to act as potential reaction sites, driving the main reactions of degradation.
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| 8. |
- Badía, J. D., et al.
(författare)
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A thermogravimetric approach to study the influence of a biodegradation in soil test to a Poly(lactic acid)
- 2008
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Ingår i: Macromolecular Symposia. - : Wiley. - 1022-1360 .- 1521-3900. ; 272:1, s. 93-99
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Tidskriftsartikel (refereegranskat)abstract
- An amorphous grade Poly (lactic acid) (PLA) was selected for an accelerated burial in soil test during 450 days. Thermogravimetric analyses were carried out to study the effects of degradation in soil on the thermal stability and the thermal decomposition kinetics. A single stage decomposition process is observed for all degradation times. It is shown that the thermal stability of PLA is slightly affected by degradation in soil. Concerning the study of the thermal decomposition kinetics, Criado master curves were plotted from experimental data to focus the study of the thermodegradation kinetic model.The kinetic methods proposed by Broido and Chang were used to calculate the apparent activation energies (Ea) of the degradation mechanism. These results were compared to the Ea values obtained by the method developed by Coats and Redfern in order to prove the applicability of the former methods to the kinetic study. As expected, non-linear tendency is found out for Ea variation along the degradation times, which can be explained as an evolution by stages. Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA.
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| 9. |
- Badia, J. D., et al.
(författare)
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Assessing the MALDI-TOF MS sample preparation procedure to analyze the influence of thermo-oxidative ageing and thermo-mechanical degradation on poly (Lactide)
- 2011
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 47:7, s. 1416-1428
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Tidskriftsartikel (refereegranskat)abstract
- Multiple processing by means of successive injection cycles was used to simulate the thermo-mechanical degradation effects on the oligomeric distribution of PLA under mechanical recycling. Likewise, an accelerated thermal ageing over PLA glass transition was performed in order to simulate its service life. MALDI-TOF MS was used for the analysis and the sample preparation procedure was assessed by means of a statistical Design of Experiments (DoE). The quality effects in use for the analysis were signal-to-noise ratio and Resolution. Different matrixes, analyte/matrix proportions and the use of NaTFA as cationization agent were considered. A deep inspection of the statistical results provided a better understanding of the influence of the different factors, individually or in combination, to the signal. The application of DoE for the improvement of the MALDI measurement of PLA stated that the best combination of factors (levels) was the following: matrix (s-DHB), proportion analyte/matrix (1/5 V/V), and no use of cationization agent. Degradation primarily affected the initially predominant cyclic [LA(C)](n) and linear H-[LA(L)](n)-OH species, where LA stands for a PLA repeating unit. Intramolecular and intermolecular transesterifications as well as hydrolytic and homolytic reactions took place during the formation and disappearance of oligomeric species. In both degradation mechanisms induced by thermal ageing and thermo-mechanical degradation, the formation of H-[LA(L)](n)-O-CH(3) by intermolecular transesterifications was highlighted.
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| 10. |
- Badia, J. D., et al.
(författare)
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Effect of sisal and hydrothermal ageing on the dielectric behaviour of polylactide/sisal biocomposites
- 2017
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Ingår i: Composites Science And Technology. - : Elsevier. - 0266-3538 .- 1879-1050. ; 149, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- The dielectric properties of virgin polylactide (PLA) and its reinforced composites with different weight amounts of sisal fibres were assessed at broad temperature (from −130 °C to 130 °C) and frequency ranges (from 10−2–107 Hz), before and after being subjected to accelerated hydrothermal ageing. The synergetic effects of both the loading of sisal and hydrothermal ageing were analysed by means of dielectric relaxation spectra. The relaxation time functions were evaluated by the Havriliak-Negami model, substracting the ohmic contribution of conductivity. The intramolecular and intermolecular relaxations were respectively analysed by means of Arrhenius and Vogel-Fulcher-Tammann-Hesse thermal activation models. The addition of fibre increased the number of hydrogen bonds, which incremented the dielectric permittivity and mainly hindered the non-cooperative relaxations of the biocomposites by increasing the activation energy. Hydrothermal ageing enhanced the formation of the crystalline phase at the so-called transcrystalline region along sisal. This fact hindered the movement of the amorphous PLA fraction, and consequently decreased the dielectric permittivity and increased the dynamic fragility.
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