The mechanical properties of epoxy resins and epoxy resin/graphite fiber composites are adversely affected by moisture absorption. Incorporation of masked isocyanates that unmask to release isocyanates in situ at the cure temperatures (150-177ºC) reduce the equilibrium absorption up to ∼70%. Dynamic mechanical analyses and stress-strain properties of epoxy resins containing masked isocyanates were examined to determine their effect on mechanical properties. The ultimate Tg of the epoxy is reduced by incorporation of masked isocyanate, but the actual Tg is comparable to the “as cured” Tg of the epoxy. The dynamic moduli up to the Tg are relatively unaffected. Ina number of cases, the initial modulus, elongation at break and peak stress are equal or better than the unmodified resins.

A Hartmann-Hahn type of cross-polarization experiment is performed with dipolar order in the rotating frame instead of Zeeman order as is the usual case. Under matched Hartmann-Hahn conditions, ω1S = ω1I, no polarization is transferred. Under mismatched conditions, however, a positive or a negative polarization is acquired depending on whether ω1S > ω1I or ω1S < ω1I and also on the sign of the initial spin temperature of the dipolar order. The polarized S signal has a maximum intensity when the mismatch amount |ω1S − ω1I| has the same order of magnitude as the local field produced by the homonuclear and heteronuclear dipolar interactions. This behavior can be described qualitatively by a spin-temperature hypothesis.

The removal and fate of CaCO[sub 3] extender in latex and alkyd paints upon exposure of paint films to UV and atmospheric pollutants generated in a large environmental chamber were studied using optical and scanning electron microscopy in combination with energy dispersive spectroscopy. X-ray mapping of film cross sections was used to examine migration of calcium to the film surface, and x-ray diffraction and Energy Dispersive Spectroscopy (EDS) were employed to determine crystalline nature of surface deposits. Crystals of various forms of calcium sulfate formed on paint surfaces. Surprisingly, migration of calcium to the paint surface occurred in the absence of liquid water in the form of dew.

This text on how polymers can be utilized in textile science covers environmental effects, biomedical applications, logistical considerations and latex blends.

Automotive finishes of various compositions on metal substrates were exposed vertically in a smog chamber to UV and acidic atmospheres. The pollutants were generated from combinations of SO (sub 2), NO, propylene, water, and air. Dews of different composition were generated and collected twice a day. Spot tests were performed by placing drops of dews on the surfaces of paints and heating in an air-circulating oven at 90 C for 24 hours. Visual observation, reflection optical microscopy, profilometry, SEM, and EDS were used to examine surface damage. Various degrees of damage occurred depending upon the dew composition and surface properties. In general, the damage areas were in the form of rings with diameters smaller than the original drop. After rinsing and buffing, the damage was still visible. Microscopy and SEM revealed that the rings consisted of numerous small areas of damage and that swelling, pitting, blistering, and cracking had occurred. EDS showed aluminum and sulfur at the damage surface, while the surrounding area did not. Since the base coat contained Al flakes, this suggested that the acidic dew had penetrated through the top coat into the base coat.

Journal of Polymer Science Part B: Polymer PhysicsVolume 27, Issue 9 p. 1949-1949 Note Anisotropic solutions of methylol cellulose R. D. Gilbert, R. D. Gilbert Fiber and Polymer Science Program, North Carolina State University, Raleigh, North Carolina 27695Search for more papers by this authorR. E. Fornes, R. E. Fornes Fiber and Polymer Science Program, North Carolina State University, Raleigh, North Carolina 27695Search for more papers by this author R. D. Gilbert, R. D. Gilbert Fiber and Polymer Science Program, North Carolina State University, Raleigh, North Carolina 27695Search for more papers by this authorR. E. Fornes, R. E. Fornes Fiber and Polymer Science Program, North Carolina State University, Raleigh, North Carolina 27695Search for more papers by this author First published: August 1989 https://doi.org/10.1002/polb.1989.090270911AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References 1 P. A. Patton and R. D. Gilbert, J. Polym. Sci., Polym. Phys. Ed., 21, 515 (1983). 10.1002/pol.1983.180210403 CASWeb of Science®Google Scholar 2 H. Chanzy, Private Communication. Google Scholar 3 A. Ritchey and D. Gray, Macromolecules, 21, 2914 (1988). 10.1021/ma00188a003 Web of Science®Google Scholar 4 Zugenmaier, private communication. Google Scholar Volume27, Issue9August 1989Pages 1949-1949 ReferencesRelatedInformation

Preliminary experiments were carried out to characterize the potential deleterious effects of acidic deposition on three representative paints: an oil alkyd paint and two acrylic latex formulations. The base-polymer latex common to both latex paints was also studied individually. Free films of paint were exposed to relatively high levels of gaseous SO2 and ultraviolet light, and were immersed in aqueous SO2 at pH 2.0. Several analytical techniques were used to assess the resulting chemical and physical changes in the paint films, including sorption and diffusion measurements, attenuated total-reflectance infrared spectroscopy, dynamic mechanical analysis, sol-gel analysis, contact-angle measurements, differential scanning calorimetry, and electron spin resonance. All techniques show promise for characterizing the early stages of damage to paint films caused by acidic deposition. The major effects noted include leaching of acid-soluble extender components upon immersion in aqueous SO2, and enhanced degradation of the base polymer upon exposure to gaseous SO2, and ultraviolet light.

The epoxy resin formed by tetraglycidyl 4,4'-diamino diphenyl methane and 4,4'-diamino diphenyl sulfone was characterized by dynamic mechanical analysis. Epoxy specimens were exposed to varying dose levels of ionizing radiation (0.5 MeV electrons) up to 10,000 Mrads to assess their endurance in long-term space applications. Ionizing radiation has a limited effect on the mechanical properties of the epoxy. The most notable difference was a decrease of approximately 40°C in Tg after an absorbed dose of 10,000 Mrads. Sorption/desorption studies revealed that plasticization by degradation products was responsible for a portion of the decrease in Tg.

This report describes 3 MeV proton bombardment experiments on several polymeric materials of interest to NASA carried out on the Tandem Van De Graff Accelerator at the California Institute of Technology's Kellogg Radiation Laboratory. Model aromatic and aliphatic polymers such as poly(1-vinyl naphthalene) and poly(methyl methacrylate), as well as polymers for near term space applications such as Kapton, Epoxy and Polysulfone, have been included in this study. Chemical and physical characterization of the damage products have been carried out in order to develop a model of the interaction of these polymers with the incident proton beam. The proton bombardment methodology developed at the Jet Propulsion Laboratory and reported here is part of an ongoing study on the effects of space radiation on polymeric materials. The report is intended to provide an overview of the mechanistic, as well as the technical and experimental, issues involved in such work rather than to serve as an exhaustive description of all the results.

The epoxy resin system formed by tetraglycidyl 4,4'-diamino diphenyl methane (TGDDM) and 4,4'-diamino diphenyl sulfone (DDS) was characterized by dynamic mechanical analysis and differential scanning calorimetry. Dynamic mechanical properties of graphite fiber epoxy composite specimens formulated with two different adhesive systems (NARMCO 5208, NARMCO 5209) were determined. The specimens were exposed to varying dose levels of ionizing radiation (0.5 MeV electrons) with a maximum absorbed dose of 10,000 Mrads. Following irradiation, property measurements were made to assess the influence of radiation on the epoxy and composite specimens. The results established that ionizing radiation has a limited effect on the properties of epoxy and composite specimens.