Photo-oxidative stability of paraloid acrylic protective polymers

Abstract The photo-oxidative stability of a series of commercial acrylic/methacrylic protective resins, which find use in consolidation and protection of art works, monuments and historical buildings, and are known by the name of Paraloids, has been investigated. The structural and molecular changes occurring under conditions of artificial solar light irradiation have been followed by FTIR and UV–Vis spectroscopy, and size exclusion chromatography. In all the resins the first degradative event which is detected is the molecular weight distribution change due to chain scissions and/or coupling of macroradicals. The overall stability of the polymers is strongly influenced by the presence of long alkyl side groups, such as butyl or isobutyl, whose oxidation is favoured by the presence of relatively labile hydrogen atoms. At the same time these polymers containing long ester groups undergo fast and extensive cross-linking together with some fragmentation and consequent weight losses. The resins containing only ethyl and methyl esters showed a good stability towards oxidation, reaching an equilibrium between scission reactions and macromolecular coupling which permit them to maintain their molecular characteristics during the ageing.

[1]  Maria João Melo,et al.  Photodegradation of acrylic resins used in the conservation of stone , 1999 .

[2]  J. Lemaire,et al.  Photolysis and photo-oxidation of ethylene-ethyl acrylate copolymers , 1986 .

[3]  Giovanni G. Amoroso,et al.  Stone decay and conservation , 1983 .

[4]  J. Lemaire,et al.  Influence of hydroperoxides on the photothermal oxidation of polyethylene , 1981 .

[5]  K. Hatada,et al.  Effect of Stereoregularity on the Thermal Behavior of Poly(methacrylic acid)s. 2. Decomposition at Low Temperatures , 1998 .

[6]  N. Allen,et al.  The durability of water-borne acrylic coatings , 1995 .

[7]  George Wypych,et al.  Handbook of Material Weathering , 1995 .

[8]  J. H. Adams.  Analysis of the nonvolatile oxidation products of polypropylene I. Thermal oxidation , 1970 .

[9]  Gerald Scott,et al.  Polymer Degradation and Stabilisation , 1988 .

[10]  Oscar Chiantore,et al.  Photooxidative degradation of acrylic and methacrylic polymers , 2000 .

[11]  A. Tobolsky,et al.  Structure and Reactivity in the Oxidation of Elastomers , 1965 .

[12]  L. J. Bellamy.  The infra-red spectra of complex molecules , 1962 .

[13]  M. Lazzari,et al.  Characterization of Acrylic Resins , 1996 .

[14]  S. Nakhla.  A COMPARATIVE STUDY OF RESINS FOR THE CONSOLIDATION OF WOODEN OBJECTS , 1986 .

[15]  R. Arnaud,et al.  Photo-oxidation of linear low density polyethylene: A comparison of photoproducts formation under natural and accelerated exposure , 1993 .

[16]  Pippa Cruickshank,et al.  The conservation of amber , 1995 .

[17]  R. S. Williams,et al.  Adhesive testing at the Canadian Conservation Institute-an evaluation of selected poly(vinyl acetate) and acrylic adhesives , 1996 .

[18]  W. Potts,et al.  Infrared absorptions characteristic of organic carbonate derivatives and related compounds , 1961 .

[19]  M. Lazzari,et al.  Photochemical stability of partially fluorinated acrylic protective coatings I. Poly(2,2,2-trifluoroethyl methacrylate) and poly(1H,1H,2H,2H-perfluorodecyl methacrylate-co-2-ethylhexyl methacrylate)s , 2000 .

[21]  Anthony Davis,et al.  Weathering of polymers , 1983 .

[22]  M. Polytechnic,et al.  Polymers in Conservation , 1993 .

[23]  Oscar Chiantore,et al.  Thermal-ageing of paraloid acrylic protective polymers , 2000 .

[24]  Stephen P. Koob,et al.  THE USE OF PARALOID B-72 AS AN ADHESIVE: ITS APPLICATION FOR ARCHAEOLOGICAL CERAMICS AND OTHER MATERIALS , 1986 .

[25]  J. Lemaire,et al.  Mécanismes de photo-oxydation du poly(méthacrylate de méthyle) , 1991 .