Wavelength tunability in photoinitiated cationic polymerization
Onium salts, widely used cationic photoinitiators, have absorption in the short wavelength of the UV spectrum. However, their spectral sensitivity can be tuned up to the visible region by using several methods. Photosensitization of onium salts, their charge transfer complex formation and their free radical promotion are some techniques that are used to provide wavelength flexibility. This chapter summarizes these methods. Upon irradiation photosensitizers such as anthracene, perylene and phenothiazine form exciplexes with onium salts generating reactive species via electron transfer. Furthermore, ground state charge transfer formation Correspondence/Reprint request: Dr. Y. Yagci, Istanbul Technical University, Department of Chemistry, Maslak, Istanbul 34469, Turkey. E-mail: yusuf@itu.edu.tr
Influence of N-vynilcarbazole on the photopolymerization process and properties of epoxy-acrylate interpenetrating polymer networks
Abstract Photocured simultaneous epoxy-acrylate interpenetrating polymer networks (IPNs) were formed both under irradiation by UV-lamp and natural sunlight. The conversion degrees of functional groups were calculated by using data obtained from Fourier transform infrared (FTIR) spectroscopy. The influence of N-vynilcarbazole (NVC) as a photosensitizer on the kinetics of IPN photopolymerization was investigated. The conversion degrees of epoxy groups were revealed to increase significantly with the addition of NVC to the given systems. The phase morphology of IPNs was analyzed by optical and scanning electronic microscopy as well as by dynamic mechanical analysis (DMA). The data obtained using DMA method, which was used for analyzing the IPN samples with different component ratios, indicate the formation of both phase-separated and single-phase IPNs. The phase separation is occurred only in NVC-containing 50:50 IPN.
Pig Vocalizations Under Selected Husbandry Practices
Acoustical characteristics of vocalizations of sows, piglets, and nursery pigs under selected husbandry practices were analyzed with a digital signal processing system. The duration (D) and major energy-resonance frequency (P) for each call were determined as follows: a) processing of piglets (D = 0.81 s and f* = 3 700 Hz); b) food anticipation of breeding-gest ation sows (2.50 s and 3 000 Hz); c) isolation of piglet (0.34 s and 500, 3 500 Hz); d) startling of nursery pigs (0.29 s and 900 Hz); e) sows in heat (3.07 s and 1 375 Hz); f) farrowing (0.10 s and 3 000 Hz); g) sow nursing (0.15 s and 1 000 Hz); and h) mate greeting of sow (0.13 s and 1 000 Hz). Calls a) to d) are responses to human generated stressors, and calls e) through h) responses to social and physiological states of the pigs. Thus, vocalizations can be segmented for different pig production situations.