| 1. |
- Björk, Folke., et al.
(författare)
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Degradation of components in flooring systems in humid and alkaline environments
- 2003
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Ingår i: Construction and Building Materials. - 0950-0618 .- 1879-0526. ; 17:3, s. 213-221
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Tidskriftsartikel (refereegranskat)abstract
- Constituents from products that are used in the flooring on a concrete slab such as carpets of plasticised PVC and water-based adhesives sometimes degrade in an alkaline and humid environment. The concrete itself could be such an environment. In order to examine the effect of different levels of alkalinity and humidity on the mentioned products a specialised procedure was developed. By this procedure it was possible to imitate the effect of an environment of alkalinity and humidity corresponding to a recently produced concrete slab on different substances and also collect volatile degradation products produced. Degradation of some of the constituents was dependent on the levels of alkalinity and humidity, although there were significant differences in the possibility to resist the environmental factors. For some of the components, an increase in alkalinity resulted in a much higher production of degradation products even when the relative humidity was kept on a comparatively low level. The results give basis for a recommendation not to adhere plastic floorings directly to a recently produced slab of high-quality concrete because the alkaline material in the concrete could cause degradation.
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| 2. |
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| 3. |
- Camacho, W., et al.
(författare)
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Assessment of thermal and thermo-oxidative stability of multiextruded recycled PP, HDPE and a blend thereof
- 2002
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Ingår i: Polymer degradation and stability. - 0141-3910 .- 1873-2321. ; 78:2, s. 385-391
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Tidskriftsartikel (refereegranskat)abstract
- Differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and chemiluminescence (CL) techniques have been used for assessment of thermal and thermo-oxidative stability of recycled PP, HDPE and their blend containing 20 wt.% of PP. The pure polymers and the blend were subjected to six extrusion cycles. The oxidation induction time (OIT) of the PP, PE and the blend decreased with the number of extrusion cycles also did the temperature of oxidation (T-ox). The thermal stability of PE decreased with the number of number of processing cycles, which may indicate that the shear forces during processing induce chain scission of the polymer backbone leading mainly to shortening of the chains. PP, however showed a decrease in thermal stability up to the third extrusion, and about the same stability during further processing. Thus chain scission predominated during all the extrusions and no chain branching or crosslinking were observed. The behaviour of the blend showed a synergetic tendency and did not obey the mixture rule. The CL runs produced a clearer picture of the oxidation process in blends since two peaks were observed, a sharp one corresponding to the PP and the other of bimodal shape to PE. The PP appeared to oxidize first and accelerated the oxidation of PE due to the presence of oxidation sites in the PE-PP interfaces. The blend of PP an HDPE mechanically mixed appeared to be a two-phase system in the molten state. This information can not be obtained from DSC and TG experiments.
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| 4. |
- 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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| 5. |
- Camacho, W., et al.
(författare)
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Near infrared (NIR) spectroscopy compared with thermogravimetric analysis as a tool for on-line prediction of water diffusion in polyamide 6,6
- 2002
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Ingår i: Polymer international. - : Wiley. - 0959-8103 .- 1097-0126. ; 51:12, s. 1366-1370
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Tidskriftsartikel (refereegranskat)abstract
- NIR spectroscopy in the transmission mode and thermogravimetric analysis were used to predict diffusion of water into polyamide 6,6 samples immersed in water at 40, 60, 75 and 90degreesC for different periods of time. The sorption curves between 40 and 75 were sigmoidal indicating that the surface concentration was time dependent. The sorption curves were readily fitted by the use of a time-dependent surface concentration and a water-concentration-dependent diffusivity. The zero-concentration water diffusivity decreased non-linearly and the activation energy of diffusion increased from 24 to 58 kJ mol(-1), with decreasing temperature. The surface concentration relaxation time decreased rapidly. The sorption of water in thick polyamide samples was readily characterized by FT-NIR spectroscopy. The accuracy and feasibility of this method was similar to conventional thermogravimetric methods. The greatest advantage of FT-NIR, however, is the possibility of detecting and monitoring the moisture concentration on-line and in a non-destructive way.
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| 6. |
- Camacho, W., et al.
(författare)
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NIR, DSC, and FTIR as quantitative methods for compositional analysis of blends of polymers obtained from recycled mixed plastic waste
- 2001
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 41:9, s. 1626-1635
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Tidskriftsartikel (refereegranskat)abstract
- Methods for the determination of the composition of two binary blends in mixtures of recycled polymeric materials were analyzed and compared. Recycled polypropylene/polyethylene (PP/HDPE) and recycled poly(acryl-butadiene-styrene) and polypropylene(ABS/PP) were used to develop and validate the methods. Diffuse reflectance near infrared spectroscopy (NIRS) offers high sensitivity and ease of operation and a possibility to perform multivariate data analysis. In comparison, differential scanning calorimetry (DSC) and Mid-IR which are commonly used for this purpose require certain sample preparation and are indeed time consuming. In addition, the low sensitivity of these two methods to concentrations lower than 1% wt makes their application in quality control of recycled polymers inappropriate. NIR can be used for estimating the composition of the recyclate on-line in only a few seconds, no sample preparation is required, and high precision is achieved. We obtained a root mean square error of prediction (RMSEP) equal to 0.21% wt in the interval from 0-15% wt of PP in HDPE and a RMSEP equal to 0.91% wt in the interval 0-100%. For blends of PP/ABS a RMSEP of 0.74% wt in the range 0-100% and 0.32% wt in the range 0-15% wt PP was calculated. Most of the variation in the spectral data with respect to the polymer blend composition for all the studied blends were explained by two principal components (PC). The optimal number of factors (PC) was determined by cross-validation analysis.
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| 7. |
- Camacho, W., et al.
(författare)
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Quality-determination of recycled plastic packaging waste by identification of contaminants by CC-MS after microwave assisted extraction (MAE)
- 2000
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Ingår i: Polymer degradation and stability. - 0141-3910 .- 1873-2321. ; 71:1, s. 123-134
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Tidskriftsartikel (refereegranskat)abstract
- The quality of recycled resins of high density polyethylene (HDPE) and polypropylene (PP) separated from mixed solid waste (MSW) were studied by analyzing the tentative low molecular weight contaminants. For that purpose a microwave assisted extraction (MAE) technique was developed using MDPE and two aromatic antioxidants (Irganox 1010 and Irgafos 168) as models. A 50:50 mixture of cyclohexane and isopropanol gave high recovery yields; 97% for Irgafos 168 and 93% for Irganox 1010 and short extraction times. Limonene, isopropylester of myristic and palmitic acids were examples of products identified in recycled HDPE. These compounds are typically fragrance and flavor constituents. In addition alcohols, esters, ketones were identified. Most of the substances are constituents of the packaging fillings at their first usage. But the possibility that contaminants may have entered the material by contact with other plastics is not excluded. The major category of compounds identified already in the virgin material is composed of aliphatic hydrocarbons (e.g. pentadecane, hexadecaned, 1-hexadenene), branched alkanes, branched alkenes and others. The same kind of compounds were also identified in the recycled materials at a similar concentration as in virgin ones. Virgin and recycled polyethylene contain also ethylbenzene and o-, m- and p-xylenes, where o-xylene had the largest peak of the four. The aromatic hydrocarbons are probably parts of additives, which degraded during extraction and sample preparation procedures. Aromatic hydrocarbons without functional groups, such as ethylbenzene and xylenes are considered highly toxic, but the height and area of their peaks suggest low concentrations. The concentration of these hazardous contaminants in the recycled resin is, however, approximately five times higher in recycled material, estimated by a comparison of the peak areas. Ethylbenzene and o-, m- and p-xylenes, o-xylene having the largest peak of the four were also identified in virgin and recycled polypropylene resins.
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| 8. |
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| 9. |
- Camacho, W., et al.
(författare)
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Quantification of antioxidants in polyethylene by near infrared (NIR) analysis and partial least squares (PLS) regression
- 2002
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Ingår i: IJPAC. International journal of polymer analysis and characterization. - : Informa UK Limited. - 1023-666X .- 1563-5341. ; 7:02-jan, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- Partial least squares (PLS) regression was used to generate a calibration model that can be used for the prediction of the content of two antioxidants, Irganox 10 10 and Irgafos 168, in high density polyethylene (HDPE). The samples containing levels of either one or both antioxidants in a range of 0-4500 ppm were analyzed by near infrared (NIR) in the diffuse reflectance mode. The samples were compounded in an extruder and subsequently analyzed as pellets, therefore, sample preparation was not required. High performance liquid chromatography (HPLC) was used as a reference method and the extraction of the antioxidants was performed either by microwave-assisted extraction (MAE) or ultrasonication. Data pretreatment of the raw NIR-data was necessary in order to eliminate the physical differences of the samples, e.g., size and shape. Multiple scattering correction (MSC) and second derivative of the raw data were used for this purpose. Root-mean-square error of prediction (RMSEP) for Irganox 1010 and Irgafos 168 was 46 and 97 ppm, respectively, when derived raw data was used,- similar results were obtained when calibration was performed on MSC data. The number of principal components was determined by cross-validation; in addition, the calibration model was validated with a test set.
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| 10. |
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