Reciprocity Law Failure in X-Ray Films

Morgan, Russell H.

doi:10.1148/42.5.471

Cited by 21 publications

(6 citation statements)

References 10 publications

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“…Photochemical processes sometimes follow the "reciprocity law", 46,47 where conversion is determined by UV dose regardless of exposure profile. Therefore, an exposure at low intensity for a long duration has the same result as an exposure at high intensity for a short duration.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Photochemical processes sometimes follow the “reciprocity law”, , where conversion is determined by UV dose regardless of exposure profile. Therefore, an exposure at low intensity for a long duration has the same result as an exposure at high intensity for a short duration. , If the DCPD resins followed the reciprocity law, printing speeds could be further increased by proportionately increasing UV irradiation intensity so that the dose remains equivalent.…”

Section: Resultsmentioning

confidence: 99%

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Employing Photosensitizers for Rapid Olefin Metathesis Additive Manufacturing of Poly(dicyclopentadiene)

2021

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The additive manufacturing (AM) of thermoset polymers has been limited primarily to radical or cationic photopolymerizations, restricting available resins and attainable material properties. Recent efforts in the AM of polydicyclopentadiene (pDCPD) via ring-opening metathesis polymerization (ROMP) have resulted in printable thermoset materials with advantageous high-performance properties. However, previous demonstrations of DCPD ROMP for AM have been hindered by sluggish printing rates and there is limited characterization of the printed materials. Here, we report the rapid direct-ink-write (DIW) AM of pDCPD by employing a photosensitizer/latent catalyst system to obtain unprecedented rates of photocatalyzed ROMP of DCPD (60 mm·s–1). Characterization of the resin system in situ shows that the use of a photosensitizer decreases the induction period from 78.3 to 3.6 s. The short induction period and rapid curing enable the DIW AM of geometrically complex architectures and printing without the need for supports. In addition, the living nature of ROMP and high catalyst stability is leveraged to improve the adhesion between layers, a long-standing and prevalent issue in extrusion-based AM. The system described herein can guide the development of rapid AM approaches for additional metathesis-active monomers and greatly expand the materials selection and performance properties achievable with additively manufactured thermoset resins.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Employing Photosensitizers for Rapid Olefin Metathesis Additive Manufacturing of Poly(dicyclopentadiene)

2021

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“…The reciprocity law hypothesizes that all photo-chemical reaction is only concerned with the total absorption energy or cumulative radiation energy [18][19][20]. The total absorption energy depends on the product of UV radiation intensity I and radiation time t, and can be written as I Â t ¼ constant.…”

Section: Analysis Methodsmentioning

confidence: 99%

Relationship between physical and mechanical properties of accelerated weathering and outdoor weathering of PVC-coated membrane material under tensile stress

Yang

Jiang

et al. 2016

Journal of Industrial Textiles

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To estimate the photo-oxidation aging performance of PVC-coated membrane material in atmospheric conditions under tensile stresses, the relationship between physical and mechanical properties under accelerated weathering test and outdoor weathering test is studied with the same cumulative UV radiation energy. And then, both tensile strength and whiteness index were measured and compared to characterize the property change of membrane material after aging under four different tensile stresses (0%, 5%, 10% and 20% of the breaking strength), respectively. In addition, FTIR spectrometry was applied to characterize the chemical components of the samples under different weathering conditions, and the carbonyl index was extracted. The results show that there were significant differences of tensile strength and carbonyl index between two kinds of aging conditions, whereas with the increasing tensile stresses, the whiteness index represented a consistent increasing deviation of accelerated weathering from the outdoor weathering. However, the relationship have been built between both whiteness index and tensile strength retention of accelerated weathering and those of outdoor weathering conditions after a Schwarzschild’s modification. Therefore, the service lifespan of PVC-coated membrane materials can be evaluated by accelerated weathering tests under tensile stresses.

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“…They concluded from their experiments that all photochemical reaction kinetics depend only on the total absorbed energy and are independent of the two factors that determine total energy, i.e., the intensity or irradiance, I, and the exposure time, t. This hypothesis later became known as the law of reciprocity because, in photography, the quality of a series of photographic or radiographic films will be uniformly constant if the exposure times to which the films are subjected vary reciprocally with the intensities of the exposing radiation. 5 For a given photoresponse, the reciprocity law states that…”

Section: Overview Of the Reciprocity Lawmentioning

confidence: 99%

Validation of the reciprocity law for coating photodegradation

Chin

Nguyen

Byrd

et al. 2005

J Coat. Technol. Res.

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Accelerating the photodegradation of commercial polymeric materials has great practical importance in the weathering community. However, questions exist as to whether high radiant flux exposure results can be extrapolated to in-service exposure levels. Based on the reciprocity law, the photoresponse of a material is dependent only on the total energy to which the specimen is exposed, and is independent of the exposure time and the intensity of the radiation taken separately. An experiment to validate the applicability of the reciprocity law for polymeric coatings has been carried out using the NIST integrating sphere-based ultraviolet (UV) weathering device. A nonpigmented, non-UV stabilized acrylicmelamine coating was exposed to six different UV radiation intensities ranging from 36 W/m 2 to 322 W/m 2 , and in the spectral region between 290 nm and 400 nm. Chemical changes in the coating due to UV exposure were measured with transmission Fourier transform infrared (FTIR) spectroscopy and UV-visible spectroscopy. Using two dose-damage models, the reciprocity law photoresponse for this polymeric system was verified for different photodegradation mechanisms, including chain scission, oxidation, and mass loss. P olymeric materials used in an outdoor environment are subjected to a wide variety of stress factors, including solar ultraviolet (UV) radiation, temperature, and moisture. The physical and chemical degradation resulting from outdoor exposure is known in the materials community as weathering. For commercially viable materials, weathering is usually a slow and lengthy process, often taking five years or longer before a critical performance property is deemed to have failed. These long testing periods are costly to the manufacturer and are also a barrier to innovation and the timely introduction of new products into the market. A need exists for developing exposure strategies that can accelerate weathering and yet permit valid extrapolations or predictions of service life from accelerated levels to in-service exposure conditions. Although temperature and moisture acting alone are important stress factors in the degradation of many materials, UV radiation, in conjunction with temperature and moisture, plays a dominant role in the photodegradation of polymeric materials. It is well known that polymer photodegradation can be accelerated by increasing the radiant flux to which the material is exposed. The law of reciprocity states that the photoresponse of a material is dependent only on the total energy involved and is independent of the intensity (or irradiance) of the radiation and the exposure time taken separately. 1 Experiments in which the photoresponse of a material is measured as a function of irradiance levels are commonly called reciprocity experiments.Over the last 100 years, the use of high irradiance exposures has been successfully employed by the biological, medical, and materials weathering communities. In materials weathering, for example, high solar irradiance field exposure devices have been reco...

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Reciprocity Law Failure in X-Ray Films

Cited by 21 publications

References 10 publications

Employing Photosensitizers for Rapid Olefin Metathesis Additive Manufacturing of Poly(dicyclopentadiene)

Employing Photosensitizers for Rapid Olefin Metathesis Additive Manufacturing of Poly(dicyclopentadiene)

Relationship between physical and mechanical properties of accelerated weathering and outdoor weathering of PVC-coated membrane material under tensile stress

Validation of the reciprocity law for coating photodegradation

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