Reciprocity Law Experiments in Polymeric Photodegradation: A Critical Review.
Reciprocity Law Experiments in Polymeric
Photodegradation: A Critical Review.
Martin, J. W.; Chin, J. W.; Nguyen, T.
Progress in Organic Coatings, Vol. 47, No. 3/4,
292-311, September 2003.
photodegradation; band theory; photoconductance;
photography; polymers; reciprocity law; Schwarzschild
Accelerating the photodegradation of polymeric materials
is of great practical interest in weathering research.
Acceleration can be achieved by exposing polymeric
materials to a high radiant flux; however, questions
have arisen within the weathering community as to
whether high radiant flux results can be extrapolated to
in-service flux levels. Experiments designed to test
this premise are called reciprocity law experiments. An
extensive review has been conducted to assess the
state-of-the-art of reciprocity law experiments in the
photography, photoconductivity, photo-medicine,
photobiology, and polymer photodegradation literatures.
From this review, the Schwarzschild law (a power law
generalization of the reciprocity law) appears to model
adequately photoresponse vs. radiant flux for most
materials and systems. A band theory model has been
presented to explain variations in the Schwarzschild law
coefficients and other experimental phenomena commonly
associated with reciprocity experiments. Obstacles to
the general acceptance of high radiant flux,
laboratory-based experiments are discussed.