Protection Of Cultural Relics Of Organic Polymer Material Stability Study

The organic-coatings are commonly used in the fields of architectures, automobiles, home appliances. There are a lot of research reports on the degradation of these polymeric materials used in these fields above. However, there are no thorough and systematical reports on the photo-degradation or thermal-degradation of these materials used as relic protection materials. Eight polymeric materials' degradation process and degradation mechanism are systematically studied by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and diffuse reflectance spectroscopy (DRS). These relic conservation materials belong to four kinds.They are: (1) polyurethanes, including TDI-polyurethane, MDI-polyurethane and HDI-polyurethane; (2) poly (acrylic acid)s, including poly (acrylic acid) varnish, Primal AC 33 and B72; (3) organic-silicons; (4) epoxy-resin.Their infrared spectrum changes under UV-irradation and in the heating process have been monitored by ATR-FTIR. Then the aging mechanism has been induced by the infrared spectra before and after aging and their difference spectra. In the condition of UV-irradiation, the polyurethanes degrade to quinoid structures or azo-compounds, which is why polyurethanes' color can easily become yellow. The aging mechanism of the poly (acrylic acid)s is that ester groups scissor to more stable lactones, accompanying the scission of side-chains.Diffuse reflectance spectroscopy is a new, non-destructive and on-line analysis technique. In this paper, DRS technique is firstly and systemically used to study on the degradation of polymeric relic protection materials. With it we can conveniently determine the changes of color on the surfaces (chromatic aberration, AE) and their reflection factors (R). Then we can measure the degree of their degradation quantitatively. Form the experiment results, it can be concluded that: these eight materials' stability against light is poly ( acrylic acid)s) organic-silicon) epoxy-resin) polyurethanes; their stability against heat is organic-silicon) poly ( acrylic acid)s) polyurethanes) epoxy-resin. Consequently, organic-silicon and poly (acrylic acid)s are outstanding to light and heat, especially Primal AC 33 and B72 of poly ( acrylic acid)s.We suggest that these two materials can be popularized in relic conservation field.The changes of parameters such as contact angles, coating hardness values, stickiness values have been measured simultaneityly. These parameters can testify the anti-aging properties of these eight kinds of materials at the aspects of physical properties, molecular weights, surface configurations and heating characteristics.