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Transport Properties and Durability of LCP and FRP materials for process equipment
KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on transport properties and durability of liquid crystalline polymers (LCP)and fibre reinforced plastics (FRP) with regard to application in industrial process equipment.In the first part of the study the possibility of using a thermotropic LCP of type Vectra A950as lining material for FRP process equipment was investigated. Its performance wascompared to that of a fluorinated ethylene propylene copolymer (FEP) with respect tochemical and permeation resistance. Transport property and chemical resistance data wereestablished for different types of LCP film (compression molded, uniaxially and biaxiallyoriented film) exposed to selected chemicals chosen to represent typical industrial processenvironments. Annealing of the LCP, which may reduce the disclination density and henceimprove the barrier properties, induced a crystallinity increase, but did not significantlyimprove the barrier and chemical resistance properties. Different surface treatments toincrease the bonding between the LCP and FRP were explored. The conclusion was that LCPhas potential to serve as lining material for FRP in contact with water, organic solvents andnon-oxidizing acid environments, although certain issues, such as jointing techniques, stillhave to be evaluated. The second part of the study focused on transport and long-termproperties of commercial thermoset and FRP materials for industrial process equipment inaqueous environments (50 – 95 °C, water activity 0.78 – 1, exposure time ≤ 1000 days). Thewater transport properties in different thermosets were related to their chemical structureusing the solubility parameter concept. The transport of water in the thermosets with differentchemical structures could be predicted from the water activity, regardless of the actual type ofionic or non-ionic solute in the solution. An empirical relationship, independent of boththermoset chemistry and temperature, was established to describe the water concentration inthe thermoset as a function of water activity and the water concentration in pure water. Inlong-term, the water concentration in the thermosets increased with exposure time. Thisseemed to be primarily related to stress relaxation processes induced by water absorption andcertain leaching effects. The effects of hydrolysis seemed to be small. The glass fibrereinforcement may to various extents affect the water transport properties by capillarydiffusion and additional absorption around fibre bundles. The extent of such processesseemed to depend on temperature, water activity and the type of thermoset and reinforcement.The present work may be a useful contribution to an increased understanding of water effectsand durability of FRP process equipment. However, open questions still remain for a morecomprehensive durability analysis.

Place, publisher, year, edition, pages
Stockholm: KTH , 2010. , iv, 52 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2010:16
Keyword [en]
Liquid crystalline polymer (LCP), Vectra A950, disclination, annealing, transport properties, diffusion, lining, bonding, glass fibre reinforced plastics (FRP), thermoset, vinyl ester, novolac, water, water activity, sorption isotherm, long-term properties, FEP
Identifiers
URN: urn:nbn:se:kth:diva-13221ISBN: 978-91-7415-584-6 (print)OAI: oai:DiVA.org:kth-13221DiVA: diva2:322293
Public defence
2010-06-04, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC20100629Available from: 2010-06-04 Created: 2010-06-04 Last updated: 2011-01-20Bibliographically approved
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. Short-Term and Long-Term Performance of Thermosets Exposed to Water at Elevated Temperatures
Open this publication in new window or tab >>Short-Term and Long-Term Performance of Thermosets Exposed to Water at Elevated Temperatures
2009 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 116, no 2, 1057- p.Article in journal (Refereed) Published
Abstract [en]

The water-transport, mechanical, and chemical-structure changes in various vinyl ester, novolac, and urethane-modified vinyl ester thermosets exposed to water at 50 to 95oC for times up to 1000 days have been studied within the framework of a larger study of osmotic blistering in fiber reinforced plastics (FRP) process components. The water sorption saturation concentration did not reach a steady-state value but gradually increased in many cases upon long-term exposure. The diffusion coefficient was not significantly affected. Infrared spectroscopy and gas chromatography-mass spectrometry indicated that the net mass loss from the thermosets on immersion in water was due to the leaching of non-reacted styrene, monomer, and additives. It is suggested that this, together with polymer relaxation processes (as measured on specimens under tension in water at 80oC), is the primary reason for the time-dependent increase in the water saturation concentration. Infrared spectroscopy indicated that, even at the highest temperatures, hydrolysis of the polymer ester groups was small. Correlations were found between the styrene content in the uncured thermosets, the estimated solubility parameters, and the sorption and diffusion coefficients.

Keyword
thermoset, transport properties, water, long-term performance
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-13806 (URN)10.1002/app.31548 (DOI)000274646300054 ()2-s2.0-75449114646 (Scopus ID)
Note
QC 20100629Available from: 2010-06-29 Created: 2010-06-29 Last updated: 2017-12-12Bibliographically approved
4. The Effect of Water Activity on the Sorption and Diffusion of Water in Thermosets Based on Polyester, Vinyl Ester, and Novolac Resins
Open this publication in new window or tab >>The Effect of Water Activity on the Sorption and Diffusion of Water in Thermosets Based on Polyester, Vinyl Ester, and Novolac Resins
2012 (English)In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 52, no 4, 718-724 p.Article in journal (Refereed) Published
Abstract [en]

In this work, the transport properties of water in various thermoset resins typically used for fiber-reinforced plastic process equipment (vinyl ester, novolac, bisphenol-A-epoxy-based polyester, and urethane-modified vinyl ester) were systematically studied with a focus on the effects of water activity. Sorption and desorption studies were carried out in aqueous solutions (water activity = 0.78–1) with different salts (NaCl, MgCl2, Na2SO4, and KCl) and one nonionic substance (sucrose) within the temperature interval 65–95°C. It was found that the water concentration in thermoset resins with different chemical structures could be predicted from the water activity, regardless of the actual solute (salt or sucrose) in the aqueous solution. The water quasi-equilibrium concentration decreased with decreasing water activity, whereas the average diffusion coefficient was considered to be independent of water activity in the studied water activity range. A relationship, based on a power law fit, was established describing the water concentration as a function of the water activity and the concentration of pure water. The relationship was independent of resin chemistry and temperature.

Keyword
thermoset, sorption, diffusion, water activity, calculations
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-13808 (URN)10.1002/pen.22042 (DOI)000301539300002 ()2-s2.0-84858447261 (Scopus ID)
Note
QC 20120327. Updated from submitted to published.Available from: 2010-06-29 Created: 2010-06-29 Last updated: 2017-12-12Bibliographically approved

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