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Influence of liquid diffusion on the performance of polymer materials in industrial applications
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Diffusion of liquids into and through polymers is an important factor that negatively may influence the durability or lifetime of a polymer structure used in industrial applications. In this work two types of polymers, a liquid crystalline polymer (LCP, Vectra A950) and various thermoset resins as used in fibre reinforced plastics (FRP) process equipment were studied with regard to barrier properties, chemical resistance and long-term performance. LCP are known for their outstanding chemical resistance and barrier properties. FRP used in process equipment may be a cost-efficient solution in chemically aggressive environments where standard carbon or stainless steel cannot be used due to its limited corrosion resistance. Transport properties of typical industrial environments were determined for the LCP and the influence of annealing and orientation was investigated to study whether the barrier properties can be improved. The possibility to use LCP as cost-effective lining for FRP was explored. Special focus was put on the diffusion of water and its effect on long-term transport properties and stability of thermoset resins as the performance of FRP is strongly related to the diffusion of water.

The results showed that Vectra A950 was suitable for organic solvent and non-oxidising acid environments. Its transport properties were gravimetrically determined and found to be 10 to 102 times lower than that of a high barrier fluoropolymer of type FEP. The degree of molecular packing increased with annealing time both below and above the melting point. Below the melting point this was – at least – partly due to crystal formation whereas above the melting point other mechanisms were involved. The effects of annealing and orientation on the transport properties in LCP were, however, very small or not significant and probably significantly longer annealing times are required. LCP has potential to be used as lining material for FRP as the use of an LCP-lining substantially reduced the permeability of and the solute sorption in a bisphenol A epoxy-based vinyl ester resin. The bonding strength was improved significantly by a combined abrasive and oxygen plasma treatment.

The long-term sorption of water in thermoset resins including bisphenol A epoxy-based vinyl ester, novolac-based vinyl ester, urethane modified vinyl ester and bisphenol A polyester resins was found to increase with exposure time whereas the diffusion coefficient was not significantly affected. It was shown that the presence of water induced relaxation processes that were considered to be the primarily reason for the increase in sorption coefficient in comparison to degradation processes, such as hydrolysis, causing osmotic processes. A general relationship for the estimation of the sorption coefficient at 80ºC in dependence of the water activity and the sorption coefficient at unit activity independent of the resin type was established.

Place, publisher, year, edition, pages
Stockholm: Fiber- och polymerteknologi , 2007.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:35
Keyword [en]
LCP, Vectra A950, thermoset resin, FRP, diffusion, disclination, annealing, lining, bonding, long-term properties in water
National Category
Polymer Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-4433ISBN: 978-91-7178-694-4 (print)OAI: oai:DiVA.org:kth-4433DiVA: diva2:12298
Presentation
2007-06-07, K2, KTH, Teknikringen, Stockholm, 14:00
Opponent
Supervisors
Available from: 2007-06-13 Created: 2007-06-13 Last updated: 2012-03-21
List of papers
1. Transport and adhesion properties of an unlined and a liquid-crystalline polymer-lined vinyl ester thermoset exposed to severe environments
Open this publication in new window or tab >>Transport and adhesion properties of an unlined and a liquid-crystalline polymer-lined vinyl ester thermoset exposed to severe environments
2005 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 95, no 4, 797-806 p.Article in journal (Refereed) Published
Abstract [en]

The application of liquid-crystalline polymers (LCP) as lining materials for fiber-reinforced plastics was investigated. The lining consisted of one uniaxially and one biaxially oriented LCP and, for comparison, a fluorinated ethylene propylene copolymer. The lining was attached to a glass-fiber-reinforced vinyl ester thermoset. The laminates were examined with respect to their chemical resistance, transport/barrier properties, and lining/matrix adhesion behavior. The transport properties were determined by gravimetric desorption measurements and cup tests. It was shown that the LCP was suitable as a lining in organic solvent and nonoxidizing acid environments. Diffusivities, equilibrium concentrations, and transmission rates of water, methanol, toluene, and trichloroethylene were obtained in the LCP, the fluorinated ethylene propylene copolymer, and also, in the case of the vinyl ester, of hydrochloric acid. In general, the diffusivity and transmission rate in the LCP were one to several orders of magnitude lower than those of the fluorinated ethylene propylene copolymer and the vinyl ester. The reinforcement in the glass-fiber-reinforced plastic led to an increase in the water and methanol diffusivities and transmission rates, which was probably attributable to liquid capillary diffusion. The lap-shear bonding strength between the LCP and the vinyl ester was poor, but it was improved almost sixfold by a combined abrasive and oxygen plasma treatment.

Keyword
copolyesters, polyesters, sorption, water, pps
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-7320 (URN)10.1002/app.21238 (DOI)000226181100003 ()2-s2.0-12344315248 (Scopus ID)
Note
QC 20100629Available from: 2007-06-13 Created: 2007-06-13 Last updated: 2011-01-20Bibliographically approved
2. Influence of disclination density and crystallinity on the transport properties of a liquid crystalline copolyester
Open this publication in new window or tab >>Influence of disclination density and crystallinity on the transport properties of a liquid crystalline copolyester
Show others...
2008 (English)In: Journal of macromolecular science. Physics, ISSN 0022-2348, E-ISSN 1525-609X, Vol. 47, no 2, 305-316 p.Article in journal (Refereed) Published
Abstract [en]

The effect of annealing on the structure and transport properties of a compression-molded liquid crystalline co-polyester (Vectra(R) A950) consisting of 73mol% poly(hydroxybenzoic acid) and 27mol% poly(hydroxy-naphthoic acid) was studied. Films were annealed above (310 degrees C) or below (260 degrees C) the melting point. The structure was studied with density measurements, optical microscopy, differential scanning calorimetry and wide-angle X-ray diffraction. It was observed that the density increased as a linear function of the logarithm of annealing time and that the crystallinity increased only on annealing below the crystal melting point. The increase in density above the melting point, and also to a large extent below the melting point, must have occurred through improved molecular packing but without any reduction in disclination density, as revealed by optical microscopy. The methanol diffusivity, obtained from desorption data, showed a moderate decrease with increasing density; the trend was only significant within a 60% confidence limit.

Keyword
liquid-crystalline copolyester, annealing, density, crystallinity, X-ray, diffusion
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-7321 (URN)10.1080/00222340701849152 (DOI)000253507100010 ()2-s2.0-43349105744 (Scopus ID)
Note
QC 20100629Available from: 2007-06-13 Created: 2007-06-13 Last updated: 2011-11-07Bibliographically approved
3. Long-term transport and stability properties of thermoset resins exposed to water
Open this publication in new window or tab >>Long-term transport and stability properties of thermoset resins exposed to water
(English)Manuscript (Other academic)
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-7322 (URN)
Note
Finns som i en omarbetad version som artikel. QC 20101116Available from: 2007-06-13 Created: 2007-06-13 Last updated: 2010-11-16Bibliographically approved

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