| 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. |
- Khabbaz, F., et al.
(författare)
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Great advantages in using a natural rubber instead of a synthetic SBR in a pro-oxidant system for degradable LDPE
- 2000
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 1:4, s. 665-673
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Tidskriftsartikel (refereegranskat)abstract
- Different pro-oxidant systems are used in degradable low-density polyethylene (LDPE). The main question is the degradation products and not the degradation time from the used materials. The pro-oxidant formulation used consisted of manganese stearate and natural rubber (NR) or manganese stearate and a synthetic, styrene-butadiene copolymer rubber (SBR). The samples were heated in air at 100 degreesC in sealed glass vials. The molecular weight changes were measured by size exclusion chromatography (SEC). The volatile and nonvolatile degradation products have been identified by gas chromatography-mass spectrometry (GC/MS). A wide variety of degradation products were identified, including ketones, carboxylic acids, keto acids, dicarboxylic acids, and furanones as a homologous series. Benzaldehyde, acetophenone, benzoic acid, benzyl benzoate, and two benzene derivative compounds were identified only in the LDPE-SBR system. These aromatic compounds originate from the styrene parr of SBR. The advantages using pro-oxidant containing NR are more effective degradation of LDPE without any aromatic degradation products.
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| 3. |
- Khabbaz, F., et al.
(författare)
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Py-GC/MS an effective technique to characterizing of degradation mechanism of poly (L-lactide) in the different environment
- 2000
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Ingår i: Journal of Applied Polymer Science. - 0021-8995 .- 1097-4628. ; 78:13, s. 2369-2378
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Tidskriftsartikel (refereegranskat)abstract
- The biotic and abiotic degradation of poly (L-lactide) (PLLA) has been studied with pyrolysis gas chromatography mass spectrometry (Py-GC-MS). A mixed culture of compost micro-organisms was used as the biotic medium. Size-exclusion chromatography (SEC), gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were utilized to monitor the degradation and degradation mechanism. Differences in pH, molecular weight, surface structure, and degradation mechanisms were noted between sample aged in biotic and abiotic medium. Using fractionated Py-GC-MS at 400 and 500 degreesC, acetaldehyde, acrylic acid, lactoyl acrylic acid, two lactide isomers, and cyclic oligomers up to the pentamer were identified as thermal decomposition products of PLA as well as some other not completely identified products. The ratio of meso-lactide to L-lactide was lower in the sample aged in the biotic media than the abiotic media. This is a result of the preference of the micro-organisms for L-form of lactic acid and lactoyl lactic acid rather than the D-form that in turn influences the formation and the amounts of meso and D,L-lactide during the pyrolysis. Based on SEM micrographs, it was shown that degradation in the biotic medium proceeded mainly via a surface erosion mechanism, whereas bulk erosion was the predominant degradation mechanism in the abiotic medium. The SEC and Py-GC-MS data indicate that degradation was faster in the biotic than in the abiotic sample.
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| 4. |
- Khabbaz, F., et al.
(författare)
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Rapid test methods for analyzing degradable polyolefins with a pro-oxidant system
- 2001
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Ingår i: Journal of Applied Polymer Science. - 0021-8995 .- 1097-4628. ; 79:12, s. 2309-2316
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Tidskriftsartikel (refereegranskat)abstract
- Chemiluminescence, size exclusion chromatography, differential scanning calorimetry, thermogravimetry, and Fourier transform infrared spectroscopy were used to assess differences in oxidation rate between two different pro-oxidant systems in degradable low-density polyethylene. The pro-oxidant formulation used consisted of manganese stearate and natural rubber or manganese stearate and a synthetic, styrene-butadiene copolymer rubber. The low-density polyethylene containing the prooxidant with natural rubber showed the highest degradation rate. Chemiluminescence and thermogravimetry were found to be the most effective techniques for establishing the differences between different pro-oxidant systems.
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| 5. |
- Khosravi, Sara, et al.
(författare)
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Wetting and film formation of wheat gluten dispersions applied to wood substrates as particle board adhesives
- 2015
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Ingår i: European Polymer Journal. - : Elsevier BV. - 0014-3057 .- 1873-1945. ; 67, s. 476-482
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Tidskriftsartikel (refereegranskat)abstract
- The wetting, penetration, and film formation of wheat gluten dispersions on porous wood substrates have been studied using different microscopy techniques. The effect variation of wheat gluten concentration, processing temperatures, dispersion composition, and the application scheme has been studied. The results have been correlated to previously obtained results on the function of wheat gluten dispersions as adhesive binders for particle boards. The results show that the dispersions readily penetrate the porous wood substrate and that the key parameters for a successful gluing are the dispersion viscosity, concentration, and the application scheme.
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| 6. |
- Khosravi, Sara, et al.
(författare)
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Wheat-gluten-based adhesives for particle boards : Effect of crosslinking agents
- 2014
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Ingår i: Macromolecular materials and engineering. - : Wiley. - 1438-7492 .- 1439-2054. ; 299:1, s. 116-124
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Tidskriftsartikel (refereegranskat)abstract
- WG proteins show potential as environmentally friendly replacements for amino/formaldehyde resins in particle boards. The performance of WG dispersions in combination with crosslinkers as adhesives for particle boards is studied. The WG dispersions are prepared with sodium hydroxide or citric acid as the dispersing agent. Polyamidoamine-epichlorohydrin (PAAE) and trimethylolpropane triacetoacetate (AATMP) are employed as crosslinkers. The performance of the WG dispersions and the crosslinkers are evaluated based on board properties, i.e., internal bond, thickness swelling, and water absorption. The results show an enhanced performance of WG using PAAE as crosslinker. The results reveal it is advantageous to disperse WG in sodium hydroxide compared to citric acid. The potential of crosslinked wheat-gluten-based adhesives for particle boards is demonstrated. The effect of parameters such as crosslinking type and pH is described. A formaldehyde-free particle board adhesive is thus obtained.
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| 7. |
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| 8. |
- Nordqvist, Petra, et al.
(författare)
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Characterization of hydrolyzed or heat treated wheat gluten by SE-HPLC and 13C NMR : Correlation with wood bonding performance
- 2013
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Ingår i: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 51, s. 51-61
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Tidskriftsartikel (refereegranskat)abstract
- Wheat gluten, being an abundant and relatively inexpensive protein source, is an attractive raw material for sustainable wood adhesives. Mild enzymatic hydrolysis (degree of hydrolysis: 0-5.5%) or heat treatment (50, 70, or 90°C for 15min-24h) was used to improve the bonding performance of wheat gluten. Size exclusion high performance liquid chromatography (SE-HPLC) and nuclear magnetic resonance (13C NMR) were used to correlate the obtained changes in bonding performance with the structural changes of wheat gluten.The protein structures of the samples heated at 50°C or 70°C were mainly unfolded as interpreted from the SE-HPLC results, however, without improvement in bonding performance. The 13C NMR results indicate that the extent of unfolding at 50°C or 70°C is too low to result in improved bond strength. Generally, heat treatment at 90°C or lower levels of hydrolysis (0-0.6%) resulted in similar improvements in bond strength and water resistance. The results indicate that the improvements in bonding performance are due to a combination of unfolding and polymerization for the samples heated at 90°C, while it is due to unfolding of the protein structure for the hydrolyzed samples. Higher levels of hydrolysis (≥1.3%) resulted in impaired bond strength and water resistance, most likely due to the decreased molecular size of the proteins. Carbohydrates, normally strongly associated with the proteins, were liberated during the hydrolysis, possibly contributing to the reduced bond strength for these samples.
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| 9. |
- Norström, Emelie, et al.
(författare)
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Gum dispersions as environmentally friendly wood adhesives
- 2014
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Ingår i: Industrial crops and products (Print). - : Elsevier BV. - 0926-6690 .- 1872-633X. ; 52, s. 736-744
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Tidskriftsartikel (refereegranskat)abstract
- Today, wood adhesives are mainly prepared from petroleum-based polymers. There is an ambition to decrease the utilization of petroleum-based raw materials and introduce bio-based polymers instead. However, the utilization of bio-based polymers is often limited due to insufficient properties in terms of water resistance or heat resistance. In this study bio-based dispersions have been prepared of locust bean gum, guar gum, xanthan gum and tamarind gum and evaluated as wood adhesives. Due to the high viscosity of the dispersions, a low dry solids content of 6. wt% was used. The film forming properties have been investigated and contact-angle measurement have been performed to obtain an indication of water resistance. Wood substrates have been bonded together and the bonding performance has been evaluated with different techniques. The gum dispersions have been compared with a commercial poly(vinyl acetate)-based wood adhesive and the results demonstrate that gums can be used as binders for wood adhesives. Locust bean gum dispersions show remarkable results - comparable to the commercial wood adhesive - even though the dry solids content is very low. The locust bean gum dispersion fulfills the D2 and WATT 91 requirements for wood adhesives according to the European Standard EN 204 and European Standard EN 14257.
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| 10. |
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