| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- Contat-Rodrigo, L., et al.
(författare)
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Ultrasonication and microwave assisted extraction of degradation products from degradable polyolefin blends aged in soil
- 2001
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Ingår i: Journal of Applied Polymer Science. - 0021-8995 .- 1097-4628. ; 79:6, s. 1101-1112
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Tidskriftsartikel (refereegranskat)abstract
- Two nonconventional extraction techniques, microwave assisted extraction (MAE) and ultrasonication, were used to extract degradation products from polyolefins with enhanced degradability. High-density polyethylene/polypropylene blends with two different biodegradable additives (a granular starch/iron oxide mixture and Mater-Bi AF05H) were subjected to outdoor soil burial tests and removed at different periods of time between 0 and 21 months. The extracted products were analyzed by gas chromatography mass spectrometry (GC-MS). Ultrasonication was found to be a more suitable technique than MAE because of better reproducibility. In addition, higher amounts of certain products (e.g., carboxylic acids) were extracted by ultrasonication than by MAE. The degradation products extracted from the two blends were basically a homologous series of alkanes, alkenes, carboxylic acids, and alcohols. The amount of hydrocarbons (saturated and unsaturated) and alcohols remained basically the same as the degradation times increased. However, carboxylic acids tended to decrease slightly with the exposure time. Their concentration remained practically unchanged until 12 months of soil burial when a more significant decrease was noted. The quantitative analysis of the degradation products revealed for both samples a decrease in the amount of carboxylic acids with the exposure time, although the trend was different according to the additive used in each sample. For blends with Mater-Bi the amount of carboxylic acids was at a minimum after 12-month exposure in soil, which coincided with a minimum in the molecular weight distribution. After blends with granular starch/iron oxide were exposed to 3 months in soil, tetradecanoic acid was no longer detectable and the amount of hexadecanoic and octadecanoic acids decreased significantly. Solid-phase microextraction, a solvent-free extraction technique, was used to extract the degradation products that could have migrated to the soil from blends with Mater-Bi. Small amounts of tetradecanoic acid and dodecanol were identified by GC-MS in the soil surrounding the sample. The degradation patterns observed here correlate with our previous results from mechanical and morphological characterization of these samples.
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| 5. |
- Vilaplana, Francisco, et al.
(författare)
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Performance of crystallization analysis fractionation and preparative fractionation on the characterization of gamma-irradiated low-density polyethylene
- 2004
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 94:4, s. 1803-1814
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Tidskriftsartikel (refereegranskat)abstract
- The effects of gamma-radiation on a low-density polyethylene (LDPE) were investigated by novel techniques, such as crystallization analysis fractionation and preparative fractionation, to analyze and compare their performance with other analytical procedures such as DSC, FTIR, and GPC. The LDPE was thus irradiated with four different doses of gamma-radiation. Different fractions were obtained from these irradiated materials by preparative fractionation, which were characterized by the above-mentioned analysis techniques. The changes in the morphology and chemical structure of LDPE after the irradiation were analyzed and it was found that both oxidative scission and crosslinking are phenomena related to the exposure of LDPE at high-energy radiation. Crystallization analysis fractionation and preparative fractionation proved to be suitable techniques to characterize the effects of gamma-radiation on a low-density polyethylene material.
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