Crosslinking and ozone degradation of thermosetting resins based on maleic anhydride/diene copolymer and polyfunctional alcohols

Crosslinking and de‐crosslinking reactions of an alternating copolymer of maleic anhydride (MAn) and 2,4‐dimethyl‐1,3‐pentadiene (DMPD) by thermal curing with polyfunctional alcohols as the crosslinkers and subsequent ozone degradation are reported in this article. The ring‐opening reaction of an anhydride group by polyfunctional alcohols produces network polymers with an ester linkage. The rate of crosslinking reaction depends on the curing conditions, i.e. the structure of the used alcohols and the curing temperature and time. The crosslinking density of the alcohol‐cured copolymers is low due to a slow reaction between the anhydride and hydroxy groups, being different from the corresponding epoxy‐cured copolymer with a dense network structure reported in a previous article. The insoluble resins are readily de‐crosslinked and solubilized by ozone degradation. The polymer surface modification by ozone is also investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42763.     

Determination of degradation kinetics of two polyester thermosetting powder coatings using TGA and colorimetric analysis

Thermal stability and thermal degradation kinetics of two different polyester thermosetting powder coatings used as decorative finish in outdoor architectural applications, one standard durable and one superdurable, were investigated. The activation energies of the main stages of the degradation processes were determined by applying Kissinger's and Ozawa's equations on TGA data, which were obtained by using a thermobalance at different rates of heating in a mixed atmosphere of oxygen and nitrogen. The superdurable sample has an activation energy higher than that of the standard durable coating. Both the samples showed greater stability with respect to carboxylated polyesters with TGIC as cross-link agent and epoxy resins with dicyandiamide as reticulating agent. The results were compared to those obtained from aging experiment carried out in a oven at three different isothermal temperatures. The activation energy values were obtained from colorimetric measurements of the aged samples. Data from different approaches resulted closely comparable and it was possible to estimate the activation energies of the degradation processes from total chromatic changes with an error lower than 5% with respect to TGA. This last result highlights the possibility of obtaining kinetic data on these coatings also by using the colorimetric technique.     

Epoxy thermosetting systems based on cycloaliphatic diamines

We have investigated the reaction kinetics of a liquid prepolymer DGEBA with isophorone diamine (IPD) and menthane diamine (MNDA). IPD is 10 times more reactive than MNDA. With mixtures of these two hardeners we have the possibility to control the reactivity of the curing agent and the pot life of the system. The kinetic results can be described with a single conversion temperature-phase diagram and interpreted with the classical autocatalytic epoxyprimary and secondary amine hydrogens addition. The differences between IPD and MNDA can be explained by the steric hindrance around the amine group of MNDA and also by the difficulty to obtain pure MNDA without oxidation.     

Effect of catalyst on the thermal degradation of a polycyanurate thermosetting system

The thermal degradation of a polycyanurate thermosetting material was examined by monitoring glass temperature and weight loss at various temperatures ranging from 180 to 220°C. The effect of the cocatalysts, nonylphenol and copper naphthenate, which are generally used to facilitate curing, were also studied. A decrease in T_g is observed with increasing time at elevated temperatures in the systems containing copper naphthenate, with the onset of degradation occurring sooner with higher concentrations of the copper compound. No change in T_g occurred at long times in systems containing only nonylphenol. Weight loss studies were used to calculate an apparent activation energy of degradation. It was found to be approximately 50 kcal/mol. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 127–131, 1997     

Weathering study of epoxy paints

The weathering characteristics of TiO₂-based paints of diglycidyl ethers of bisphenol A (DGEBPA), bisphenol F (DGEBPF), bis-2,6-xylenol F (DGEBXF), bis-2,6-xylenol S (DGEBXS) and bis-2,6-xylenol (DGEBX) with various curing agents have been studied by subjecting them to accelerated and environmental weathering. Of all the epoxy resins, the paint using DGEBPA gave the best weathering characteristics with better chalk resistance, optimum yellowing and good gloss retention when cured with amine terminated dimer fatty acid-based polyamide. The methyl substitutions on aromatic ring and presence of methylene and sulfone groups between the phenolic moieties caused enhanced degradation of epoxy resins as evidenced by their faster chalking on exposure. When cured with an aminosilane compound all the epoxy paints showed excellent improvement in chalk resistance but were associated with poor initial gloss and more yellowing during exposure. The relationship between the two types of weathering was found to be approximately two and a half hours exposure in accelerated ageing being equal to 1 day in environmental weathering in Mumbai (India), thus leading to a nearly 10-fold acceleration of weathering.     

Bioactivity of antifouling paints based on organotin toxicants

This paper discusses the bioactivity of antifouling paints based on organotin toxicants, such as tributyltin fluoride (TBTF) and triphenyltin fluoride (TPTF). These compounds were used alone or mixed as the main toxicant in formulations. The use of TPTF or mixtures of TPTF and TBTF, with vinyl binders, led to paints with satisfactory bioactivity during a 24 months immersion period. With the same binders, TBTF alone provided only 12 months of antifouling protection. The correlation coefficients calculated from the fouling attachment values and the rosin content in the binder showed that the bioactivity of the tested formulations depended on the solubility of the toxicant in sea water and on the composition and solubility of the binders.     

High‐performance thermosetting films based on an amino‐functionalized poly(ether sulfone)

We have developed a sequence‐dependent synthesis of the amino‐functionalized poly(ether sulfone) P2 . The amino groups of P2 act as reactive sites toward epoxy resins. After curing P2 with diglycidyl ether of bisphenol A (DGEBA) and cresol novolac epoxy (CNE), we obtained the flexible, light‐yellow, transparent, epoxy thermosetting films P2 /DGEBA, and P2 /CNE, respectively, having glass transition temperatures (T_g) of 258 and 274°C, respectively. In addition, we also prepared a flexible film after condensation of the amino groups of P2 with the anhydride groups of 4,4′‐oxydiphthalic anhydride (ODPA); after imidization at 300°C for 1 h, the resulting P2 /ODPA thermosetting film possessed a value of T_g of 340°C. These three thermosetting films also exhibited flame retardancy with a UL‐94 VTM‐0 grade. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40980.     

Marine paints: The particular case of antifouling paints

The authors present a general overview of marine paints, paying particular attention to the case of antifouling paints. After locating these paints in the anticorrosive protection systems used on the underwater parts of ships and/or other moving structures, a summary is made of the main types of antifouling products used through history up to the present time. This is complemented by a systematic assessment of the main types of living organisms that fix themselves to the underwater parts of ships. Consideration is also briefly made of the main basic mechanisms by which the different types of antifouling paints work. Finally a number of current research lines on antifouling technologies are mentioned.     

The study of photochemical reactions in polyoximurethane

Summary The irradiation of polyoximurethane at 77K yields only iminoxy radicals. The gaseous products are CO and CO₂. The mechanism of photodegradation, including 2 initial processes of N-O and C-O bond scission is discussed. The ratio between the initial processes depends on the wavelength of the light used. Only the C-O bond cleavage results in polymer degradation.     

ESR study and copolymer analysis of acrylamide-methacrylamide solid solutions

When acrylamide-methacrylamide mixed crystals are irradiated by ultraviolet (UV) rays, a copolymeric sample is obtained containing both monomeric constituents. For identification and quantitative analysis of these copolymers, a modified form of UV spectroscopy was used. The greatest advantage of UV spectroscopy for copolymer analysis lies in its rapid application. A comparison of the spectrum of the unknown compositions with spectra of known systems by using a calibration curve and the shifts in absorption maxima in different concentrations are valuable aids in establishing the composition. Electron spin resonance (ESR) provides a correlation between the obtained copolymer composition and the shape of the signal of the responsible radical. ESR spectra obtained for UV-irradiated acrylamide-methacrylamide mixed crystals reveal that during polymerization both radicals are present. As methacrylamide percentage increases in the mixture, the signal becomes similar to the 9-line spectrum of pure methacrylamide. When there is 90% methacrylamide present in the original mixture, a 5-line signal is observed, with even-numbered peaks in the methacrylamide signal appearing now as shoulders. When the methacrylamide percentage is about 16%, a characteristic 3-line signal of acrylamide is dominant. As the methacrylamide percentage increases in the original mixture of the copolymers, ESR signals indicate a decrease in the rate constant values for second-order decay at 60°C. The stability of the formed radicals was studied by admitting oxygen to the copolymeric samples as well as to the homopolymeric systems. Since the peroxidic radicals are more active in the hydrogen abstraction process, they decay more rapidly than the macro radical itself by a bimolecular termination reaction. As the methacrylamide percentage increases in the copolymeric mixtures, the peroxide radical formation becomes more difficult. This indicates that polymethacrylamide brings more stability in copolymerization reactions with acrylamide. The polymerization rate of both monomers and their mixed crystals were enhanced by adding chlorine gas before irradiation. Chlorine acts as an agent for slowing down the radical decay as well as accelerating the radical initiation reactions.     

Research progress on bio‐based thermosetting resins

Compared with the rapid progress on bio‐based thermoplastics, research on bio‐based thermosetting resins should have attracted much more attention, considering that they will have a bright future. In this paper, the current research progress on bio‐based thermosetting resins is reviewed. We pay special attention to the synthesis and investigation of properties of epoxies and unsaturated polyesters derived from renewable plant oil, cardanol, rosin acid, lignin, glycerol, gallic acid, furan, isosorbide, itaconic acid, etc. This mini review gives an overall perspective for bio‐based thermosets.© 2015 Society of Chemical Industry     

The leveling of thermosetting waterborne coatings. Part II: Drying of coated wet films

Evaporation behavior of water/solvent blends was estimated using the universal functional activity coefficient, UNIFAC, method. The evaporation rate from a free surface of a waterborne coating, WBC, containing a co-solvent was experimentally determined. These results were used to estimate the evaporation rate from wet films of a WBC containing a variety of co-solvents with a range of initial thickness. Knowing the composition of the WBC during the drying process, the change in the viscosity and the surface tension was determined. The results strongly support the development of a surface tension gradient in the film. It is also suggested that a surface tension gradient would accelerate the leveling of the ribs if a proper co-solvent were employed.     

High-build antifouling paints based on rosin and chlorinated rubber

The fundamental objective of this work was to formulate antifouling paints giving a high thickness film with a reduced number of coats and having suitable physico-chemical properties and biocidal characteristics for the protection of ships' hulls. Formulation variables studied were WW rosin (gum rosin)/chlorinated rubber (grade 10) ratio, which defines the binder dissolution rate, and the rheological agent content (castor oil), which influences the paints' thixotropic behaviour. Red cuprous oxide, zinc oxide and natural calcium carbonate were used as pigments. Tests were made in the laboratory for evaluating abrasion resistance, adhesion and elongation. Binder dissolution rate of the different paints in artificial sea water and also some rheological parameters of the samples were determined. Service tests were performed on ships' hulls (a destroyer, two light destroyers and an aircraft carrier), showing some paints retaining good antifouling characteristics after 25 months' immersion.     

乳胶漆毒性问题的探讨

通过对组成乳胶漆各主要成分的毒性分析,得出乳胶漆是无毒的,并且符合环保要求的结论,剖析了引起乳胶漆毒性的可能因素     

UV stability of polymeric binder films used in waterborne facade paints

The UV-stability study of four polymeric binders for water-borne paints, based on acrylic, styrene-acrylic, vinyl acetate and vinyl acetate-butyl acrylate (co)polymers is described. To the best of our knowledge the UV stability of this set of binders relevant to decorative industry is systematically compared for the first time. Thin films obtained from the respective latexes were irradiated with UV light (λ ≥ 275 nm) and analysed using electrokinetic potential (ζ-potential), FTIR ATR spectroscopy, SEM microscopy and differential scanning calorimetry (DSC). The films obtained from different latexes displayed distinct changes in their surface composition and response to UV-irradiation. Among the studied compositions, the vinyl acetate-based ones seem to be the least prone to UV-degradation in the absence of other components typically present in paint formulations. The analytical techniques employed in this study are shown to be complementary and provide information on different regions of the surface layer, depending on their effective probing depth. Especially, a combination of FTIR and ζ-potential measurements is shown useful to clarify the nature of the carbonyl groups formed during photodegradation.     

The use of fluoropolymers for non-stick cooking utensils

Conclusions  The formulation of non-stick coatings for cooking utensils is probably more complicated than had been thought. It has been shown that the addition of copolymers to PTFE greatly improves the properties of the coating. The problem of having a ‘non-stick’ coating ‘sticking’ to a metal substrate is partly solved by the fluoropolymer stratifying to the coating surface. FEP is the copolymer of choice for adhesion of primers to very smooth surfaces where there is lack of mechanical adhesion. The abrasion resistance and barrier properties of the coating are enhanced by the addition of PFA due to the better mechanical properties and lower crystallinity of this copolymer. In the end, non-stick coatings are a complex blend of several fluoropolymers (homopolymer and copolymers), bonding resins and pigments. Fluoropolymers have not been developed essentially for non-stick cooking utensils technology, but today the consumer benefits from the most advanced non-stick technology due to the requirement of industry to search for increasingly improved performance with existing materials.     

High-build soluble matrix antifouling paints based on vinyl resin

The aim of this work was to formulate and evaluate high-build, soluble matrix antifouling paints showing reduced solvent retention in the film and sufficient bioactivity to protect structures submerged in sea water for long immersion periods.

The variables analyzed were binder composition, pigment content, toxicant type and thixotropic agent content.

Binder dissolution in sea water was achieved by employing WW rosin or calcium resinate; the control of the binder dissolution rate was achieved by using a vinyl resin as a cobinder. The paints were formulated with pigment volume concentrations of 40 and 45%; red cuprous oxide and triphenyl tin fluoride were used as the main toxicants. The rheological additive employed was hydrogenated castor oil at levels of 2.0 and 2.5 wt.% in the paint.

The bioactivity of the antifouling paints was determined in the natural environment (30 month immersion in sea water).     

The acetylation and enzymatic degradation of starch films

The preparation of films from starch and their degradation by amylase enzymes is described. Starch acetate was prepared by acetylation of starch with a pyridine/acetic anhydride mixture. The resulting polymer was cast into films from solutions of 90% formic acid. A series of films with a range of acetyl content were then exposed to buffered amylase solutions and the retained tensile strength measured. It was found that with a sufficient acetyl content the wet strength of the films was maintained in the aqueous solutions, but that the acetyl content was sufficiently low enough to permit degradation by a mixture of alpha and beta amylases within a period of 1 h. These films could be useful as membranes in bioreactors, which could be degraded at will by the addition of enzymes to the system. © 1993 John Wiley & Sons, Inc.