光固化聚氨酯丙烯酸酯涂层的固化动力学及其光稳定化研究

研究了脂肪族和芳香族聚氨酯丙烯酸酯类低聚物的光固化动力学和反应型受阻胺 ( r HALS)对光固化聚氨酯丙烯酸酯涂层的光防护效果。加速老化实验结果表明 :r HALS的光稳定体系可有效地将试样的黄度指数 (YI)控制在较低水平内 (辐照时间 10 0 0h ,YI <1%～ 2 % )。含有 r HALS的光固化涂层比相应的商品HALS具有更优越的耐光氧老化性能。     

Ultraviolet-curable epoxy acrylate dispersions: effect of urethane acrylate anionomers on stabilizing and film properties

 Epoxy acrylate dispersions stabilized using urethane acrylate anionomers were prepared for an application of ultraviolet (UV) curing. By observing the optical microscopy and colloidal stability for the epoxy acrylate dispersions, it was confirmed that the urethane acrylate anionomers incorporated have an interfacial activity in the interface between the epoxy acrylate oil and the water/ ethanol mixture (80/20, w/w). This was possible by the structurally designed urethane acrylate anionomers, containing a hydrophobic soft segment and two hydrophilic ionic sites in their molecules. In addition, when ultraviolet (UV)-cured, the urethane acrylate anionomers agglomerated to form the rubber domains in the epoxy acrylate film, which were induced by the ionic interaction. Consequently, this agglomerated rubber domains improved the final film properties. Received: 4 April 1998 Accepted: 1 July 1998     

The effect of different variables on the accelerated and natural weathering of agricultural films

Lifetimes required for greenhouse cover films depend heavily on the country, especially the tradition in the country. They vary from one agricultural season (i.e. 6-9 months) to several years and are strongly dependent on the use of pesticides which destroy the photostabilisers (HALS and nickel quenchers) and on other geographic and climatic factors (solar irradiation, temperature, winds, etc.).In this work, we have measured the duration of four real agricultural films using the European Standard EN 13206:2001 conditions for the accelerated weathering test and the results have been compared to their duration under accelerated weathering using more aggressive conditions (pesticide spraying, different chamber temperatures) and under natural weathering. We have also explored the effect of the backing material in the artificial weathering test and of the starting date in the natural weathering. The final goal of this study is to obtain good correlations between accelerated weathering, natural weathering at defined, controlled conditions and weathering in real-use conditions for agricultural films.     

Effect of cross-link density on the morphology,thermal and mechanical properties of flexible molded polyurea/urethane foams and films

The effect of cross-link density on the morphology and properties of two flexible molded foam samples was studied. Film samples based on the same foam formulations were also fabricated to study the feasibility of using them for the characterization of complex foam products. Fourier transform infrared spectroscopy (FTIR) and small angle X-ray scattering (SAXS) data show that films and foam samples have entirely different hard domain ordering. The results of the study of morphology indicate that an increase in cross-link density appears to increases phase mixing in film and foam samples. Differential scanning calorimetry (DSC) studies indicate that the soft segment glass transition temperature (T_g) is independent of cross-link density (at levels studied). But for both film and foam samples, morphology clearly dicates the manner in which moisture interacts with the hard domains. Results of the stress-strain behavior indicate that an increase in cross-link density increases the modulus and decreases the elongation at break. Mooney-Rivilin modeling of the stress-elongation behavior of film shows that the higher cross-link density sample gives more nonaffine behavior, possibly due to a heterogeneous distribution of hard domains. Similar modeling of the foams was not possible because of their linear stress response to surprisingly high elongation. The results of the power law modeling of stress relaxation response indicates that with an increase in cross-link density (covalent and virtual), the power law exponent decreases as expected. At levels of cross-linking and hard segment content studied, stroke-controlled equilibrium hysteresis was independent of cross-link density. Normalized dynamic mechanical spectra (DMS) show that the film samples have higher rubbery plateau modulus. The magnitude of the area under the tan δ curve at T_g indicates greater flexibility of polymer segments in foam sample. Structure-property relationships of cellular materials can be established by characterizing film samples because a parallel trend exists between each group. © 1994 John Wiley & Sons, Inc.     

Influence of rheological additives on char formation and fire resistance of intumescent coatings

Styrene-butyl acrylate copolymer based fire retardant coatings were prepared using intumescent flame-retardant additives and mineral clay type rheological additives. Three different widely used nanoclays, organic-modified montmorillonite, palygorskite and sepiolite were applied in order to determine their effect on the flame retardancy. Significant differences were found when their heat-shielding activities were evaluated. It was observed that the addition of different clay particles in amount of 0.25 w% changes the char formation process; the height, the morphology, the structure and also the mechanical resistance of the protecting shield. The different geometry and composition of the additives induced different changes in fire performance. In case of palygorskite the catalytic effect of Fe accelerated mainly the thermal decomposition, therefore the fire resistance decreased. The plate-like montmorillonite reduced the extent of the intumescent char, whereas also improved the mechanical and sustained heat resistance of the fire protecting shield. The fibrous sepiolite of low Fe content assisted the development of efficient protecting shield, which exhibited optimal cell structure, suitable thickness, and thus ensured better heat-insulating performance. Consequently, fire retardant effect of sepiolite was found to be better than the other studied clay types.     

Tailoring the desired optical and mechanical performance of polyester‐plasticized PVC films: the role of different light stabilizers on the photo‐degradation

Effect of hindered amine light stabilizer (HALS: C944) and ultraviolet absorbers (UVAs: UV326, UV531) on the photo‐stabilities of polyester‐plasticized poly(vinyl chloride) (PVC) and polyester‐plasticized PVC/pigment yellow (PY) films were studied systematically. Both ultraviolet absorbers (UVAs) and hindered amine light stabilizer (HALS) could slow down the discoloration of polyester‐plasticized PVC and polyester‐plasticized PVC/PY films. However, the addition of UVAs protected polyester‐plasticized PVC films from being discolored and its efficiency is higher than HALS. The specific order of stabilizing effect on the photo‐oxidation is UV326 > UV531 > C944. For the optical performance, both UVAs and HALS could help to maintain the transmittance of visible light after photo‐degradation. The former could effectively adsorb ultraviolet (UV) light and resulted in lower transmittance of UV light. For the polyester‐plasticized PVC/PY systems, even though HALS and UVAs cannot help to maintain the shielding ability in high‐energy visible region after UV irradiation, they can help prevent the loss in transmittance of visible light. The surface morphology exhibited small holes on the surface of the films that contain UV531 or UV326; while large and deep holes were observed on the surface of PVC films without additives, C944‐doped and C944/PY‐doped films, indicating the higher UV‐stabilizing effect of UVAs. With regard to mechanical properties, UVAs and HALS can help to prevent the loss. Our present study systematically revealed the role of different stabilizers on the polyester‐plasticized PVC and polyester‐plasticized PVC/PY systems and paved the way to offer PVC materials with functional optical performance and desired long‐term performance using different light stabilizers. Copyright © 2017 John Wiley & Sons, Ltd.     

Influence of the type of foam films and the type of surfactant on foam stability

The behaviour and the life time ( _p) of different types of foam films (thin liquid films, for which DLVO-theory is valid; common black films, Newton black films) have been studied as a function of external pressure (P), applied in the Plateau-Gibbs-borders of the foam. The foam stability and the course of thep/P-dependence are determined mainly by the type of the foam films. A criterion for estimation of foam stability is proposed on the base of the obtained experimental results.