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- Albertsson, Ann-Christine, et al.
(författare)
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Molecular weight changes and polymeric matrix changes correlated with the formation of degradation products in biodegraded polyethylene
- 1999
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Ingår i: Journal of environmental polymer degradation. - 1064-7546 .- 1572-8900. ; 64, s. 91-99
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Tidskriftsartikel (refereegranskat)abstract
- The molecular weight changes in abiotically and biotically degraded LDPE and LDPE modified with starch and/or prooxidant were compared with the formation of degradation products, The samples were thermooxidized for 6 days at 100 degrees C to initiate degradation and then either inoculated with Arthobacter paraffineus or kept sterile. After 3.5 years homologous series of mono- and dicarboxylic acids and ketoacids were identified by GC-MS in abiotic samples, while complete disappearance of these acids was observed in biotic environments. The molecular weights of the biotically aged samples were slightly higher than the molecular weights of the corresponding abiotically aged samples, which is exemplified by the increase in (M) over bar(n) from 5200 g/mol for a sterile sample with the highest amount of prooxidant to 6000 g/mol for the corresponding biodegraded sample. The higher molecular weight in the biotic environment is explained by the assimilation of carboxylic acids and low molecular weight polyethylene chains by microorganisms. Assimilation of the low molecular weight products is further confirmed by the absence of carboxylic acids in the biotic samples. Fewer carbonyls and more double bonds were seen by FTIR in the biodegraded samples, which is in agreement with the biodegradation mechanism of polyethylene.
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- Hakkarainen, Minna, et al.
(författare)
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Prediction by multivariate data analysis of long-term properties of glassfiber reinforced polyester composites
- 1999
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Ingår i: Polymer degradation and stability. - 0141-3910 .- 1873-2321. ; 64, s. 91-99
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Tidskriftsartikel (refereegranskat)abstract
- The prediction of long-term properties of polymers has been analysed by identifiction of low molecular weight compounds in glassfibre-reinforced polyester composites which were subjected to accelerated ageing at 40 and 60 degrees C and 80 %-RH for periods up to 6 years. Before the accelerated ageing the materials were stored for 20 years at ambient temperature. After different ageing times the low molecular weight products in the materials were identified with GC-MS and headspace-GC-MS. Several different alcohols, phthalates and other aromatic compounds were identified. Temperature had a large influence on the degradation of phthalates and the formation of alcohols. In the first step we used principal component analysis (PCA) and partial least square (PLS) to locate outliers and to identify the products that were not connected to degradation time or temperature. After that PCA and PLS were used to reveal if unsaturated polyesters have different degradation mechanisms at 40 and 60 degrees C by comparing the amounts and types of degradation products. The relative influence of each factor on the degradation rate was studied and groups were made among the degradation products to define which degradation products are correlated with ageing time and temperature. Finally the ageing time was predicted from the amounts of degradation products (in that case the amount of products are considered as X factors and the time of degradation as a Y response). PCA showed that it was not possible to find a pattern in the HS-GC-MS chromatograms, due to the different volatility of the compounds. The score plots revealed the existence of domains which depended on the degradation temperature. Some of the compounds (diethyl phthalate, 2-propenyl ester of bensoic acid and bensoic acid) could not be predicted by the models. These products are not related to the degradation of the material itself. At 60 degrees C, 80% RH in air, PLS models showed a good correlation between amount of identified products and degradation time and it was possible to estimate the degradation time directly from the quantity of the 13 identified degradation products.
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