Weathering Stability Research Articles

Characterization of freshly quarried and decayed Doulting limestone

Abstract Freshly quarried Doulting limestone of Jurassic age differs in terms of mineralogy and porosity compared to the decayed stone of Wells Cathedral, Somerset, UK. Stones from both localities contain allochems including ooids, peloids, extraclasts (reworked Carboniferous limestone) and bioclasts. Sparry calcite cement is present as twinned, syntaxial, overgrowths nucleated onto crinoid ossicles with high Fe content due to extensive burial cementation. The Fe content in specific phases determines the weathering stability of the rock on the building. The decayed stone shows the development of porosity which is parallel to the weathered surface, mobilization of Fe into a hard layer near the surface and incidences of high concentrations of SO 4 2- , NO 3 - and Cl - . Despite low concentrations of SO 2 present in the atmosphere at the time of the study, the extent of stone decay and composition of crustal deposits implies that SO 2 pollution may have been greater in the past, with stone currently affected by gypsum salts formed during earlier pollution episodes.

Novel micaceous reinforcing fillers with fire and smoke retarding qualities

Laboratory tests were intended to show differences in processing and weatherability which occur when various powdered and liquid barium/cadmium stabilizers are used alone and in combination with epoxy plasticizer and phosphite. The results show that in the selection of stabilizers it is not necessarily the metal content of the stabilizer which is important, but rather that optimum weathering stability is achieved by the correct combination of complex barium, cadmium and zinc components. Liquid barium/cadmium/zinc compounds of the IRGASTAB BC 445 type, combined with epoxy plasticizer and phosphite, give optimum stabilization of plasticized PVC, ease of processing and excellent weatherability.

Rapid assessment of weathering stability from exposure of polymer films. I. Real and simulated weathering of commercial ABS terpolymers

AbstractChanges in the infared transmission spectra of thin films were used to follow the natural and artificial weathering of ABS terpolymers. Photo‐oxidation of the polybutadiene moiety, which is the major process involved, occurs only after a well‐defined amount of ultraviolet energy has been absorbed. Therafter, unsaturation decreases in a first‐order manner with respect to UV energy absorbed. Under artificial conditions with constant UV intensity, energy absorbed is synonymous with time, but this is not so in natural exposure because of the variability of solar energy and its UV content. The method permits rapid comparison of commercial grades of ABS with the advantage of using natural conditions. It has been shown that pigmentation (3.6 phr brown and 1.25 phr carbon black) increases weathering stability two‐ and fourfold respectively, as assessed by induction energy and rate of disappearance of unsaturation.

Rapid assessment of weathering stability from exposure of polymer films. III. Relative weathering stability of ABS and arylon, a related polymer blend

AbstractArylon, a blend of an aromatic polysulfone and a terpolymer of acrylonitrile–butadiene and α‐methylstyrene, weathers similarly to ABS. However its first‐order rate constant for the loss of unsaturation is only 0.39 cm2(Wh)−1 as against 0.80cm 2(Wh)−1 for ABS. This slower weathering is probably caused by the decrease in light intensity penetrating Arylon compared with ABS as a result of the high degree of light scattering observed in the former.