Photochemical stability of partially fluorinated acrylic protective coatings IV. Copolymers of 2,2,2-trifluoroethyl methacrylate and methyl α-trifluoromethyl acrylate with vinyl ethers (original) (raw)
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A new acrylic terpolymer, poly(methyl methacrylate-co-butyl acrylate-co-acrylic acid) [P(MMA-co-BA-co-AA)] of ultra-high molecular weight (UHMW) was synthesized via seeded emulsion polymerization. This polyacrylic showed good film properties; high transparency, water resistance and mechanical flexibility that may suitable for many environmental based applications such as coating, packaging, label sensors etc. In order to access the photo-stability of this material for environmental application, studies were conducted under UV illumination of a short-wavelength (l ¼ 254 nm) in air. The responses were collected at different irradiation times by using several characterization techniques: infrared/UV-visible spectroscopy (FTIR/UV-Vis), gel permeation chromatography (GPC), atomic force microscopy (AFM) and thermogravimetric analysis (TGA). Two distinguishable structures, cross-linked and fragmented chains, were formed under photo-irradiation at different times of exposure. The formation of cross-linked structures at short irradiation times (t < 60 min) increases the chain length as validated from the increase in average-molecular weight (M w), whilst at longer irradiation time the fragmentation causes a decrease in the chain length (decrease in M w). Only the chain scission at longer irradiation time (t > 60 min) causes the copolymer to degrade. The centre of reaction was identified at the pendent group and no effect of main chain destabilization was observed throughout the experimental condition. The occurrence of chain cleavage during photo-degradation causes chain-chain separation, as visually seen under the imaging technique and this coincides with the observed drop in thermal stability. Photo-oxidation was also proposed to occur simultaneously with photo-degradation as the irradiation was performed in air.
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The photooxidative stability of poly(methyl acrylate), poly(ethyl acrylate), poly(ethyl methacrylate) and poly(butyl methacrylate) has been investigated under conditions of artificial solar light irradiation. Molecular and chemical changes induced by the light treatment were followed by size exclusion chromatography and Fourier transform infrared spectroscopy. The acrylate units were found to be more reactive towards oxidation, in comparison with the methacrylate ones. With short alkyl side groups chain scissions prevailed over cross-linking reactions both in acrylate and methacrylate samples. The degradation of poly(butyl methacrylate) proceeds in a completely different way, with extensive cross-linking and simultaneous fragmentation reactions. In all the samples the structure formed as result of oxidation reactions were similar. It has also been found that the first effect of degradation to be detected is that connected with the changes of samples molecular weight distributions. ᭧
A detailed surface analytical study of degradation processes in (meth)acrylic polymers
Journal of Polymer Science Part A: Polymer Chemistry, 2012
The present study investigates the degradation behavior of various high-molecular-weight acrylic polymers (50,000 < M n /g mol À1 < 100,000), namely poly(methyl methacrylate) (PMMA), poly(n-butyl methacrylate) (PBMA), poly(nbutyl acrylate) (PBA), and poly(lauryl methacrylate) (PLMA), under extreme environmental conditions. These polymers were synthesized via various polymerization techniques to create different end-groups. The polymers chosen are readily applicable in the formulation of surface coatings and were degraded under conditions which replicate the harsh Australian climate, where surface coatings may reach temperatures of up to 95 C and are exposed to broad-spectrum UV radiation of up to 1 kW m À2 . The degradation behavior of the polymeric materials on their surface was followed via ATR-IR spectroscopy, high resolution FTIR microscopy, and X-ray photoelectron spectroscopy. The extent of the observed ther-mal and photo-oxidation is directly related to the length of the ester side group, with the degradation susceptibility decreasing in the order of PLMA > PBMA/PBA > PMMA, with PMMA still stable even after 5 months exposure to the harshest condition used (UV light at 95 C). The general degradation mechanism involves the loss of the ester side groups to form methacrylic acid followed by cross-linking. The effect of the variable end groups was found to be minimal. The results from this study are in good agreement with previous studies of low-molecular-weight model polymers under identical conditions.
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Polymer, 2001
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. ᭧
Properties of UV-curable coatings containing fluorinated acrylic structures
Progress in Organic Coatings, 1999
UV-curable systems based on the copolymerisation of typical acrylic resins with¯uorinated derivatives were prepared and their properties investigated. Firstly we used as comonomer, 4,4 H -hexa¯uoroisopropylidendiphenoldihydroxyethyletherdiacrylate which gives rise to homogeneous systems when mixed with the corresponding hydrogenated monomer. By using per¯uoropolyetherurethanemethacrylates, ®lms having interesting properties were obtained. When copolymerising a low amount of¯uorinated acrylates with acrylic resins, the bulk properties of the ®lms remained unchanged, but a selective modi®cation of the surface was obtained. A series of acrylic esters of alcohols having a per¯uorinated group ÀC n F 2n1 were investigated. In all cases, a selective enrichment of the¯uorinated monomer on the ®lm surface was observed, depending on the monomer structure, its concentration and the type of substrate. # 1999 Elsevier Science S.A. All rights reserved. 0300-9440/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved. PII: S 0 3 0 0 -9 4 4 0 ( 9 9 ) 0 0 0 3 3 -8