http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Young-Gun June,정인조,Tae Hee Lee,하미란,Seung Man Noh,정현욱 한국유변학회 2021 Korea-Australia rheology journal Vol.33 No.1
Isocyanate crosslinkers with blocking agents based on various amine derivatives were newly synthesized for automotive clearcoat applications. Amine-based blocking agents were prepared by varying the alkyl substituent attached on both sides of the main nitrogen atom (named DEA, DiPA, NtBEA, and NtBiA) to modify their deblocking feature in blocked isocyanates (BIs) and curing reaction under thermal curing conditions. Curing properties of clearcoats containing amine-based BIs were characterized at the normal curing temperature of 150°C and were compared with those by the commercialized BI, Desmodur® PL350. The dissociation ability of the amine-based BIs was interpreted using the density functional theory (DFT) simulation under their optimized geometric configurations. The urethane reaction between isocyanate group in BIs and hydroxyl group in a hydroxyl-functionalized polyol binder within clearcoats was confirmed from the OH stretching absorbance data via Fourier-transform infrared (FT-IR) spectrometer. The real-time crosslinking dynamics of various clearcoats with amine-based BIs were comprehensively investigated using rotational rheometer and rigid-body pendulum tester. The surface mechanical properties of fully-cured clearcoat films were measured by nano-indentation and nano-scratch testers to address the crosslinked network formation caused by amine-based BIs. It is demonstrated that the amine-based BIs could be favorably applied to thermal curing process of clearcoats, based on their reactivity and curing performance.
Shyam Dev Maurya,Surendra K. Kurmvanshi,Smita Mohanty,Sanjay K Nayak 한국고분자학회 2017 Macromolecular Research Vol.25 No.9
The current study deals with the synthesis of various compositions of crosslinked poly(ester-urethane-acrylate) (PEUA)/methylmethacrylate (MMA) copolymer employing free radical polymerization. Initially, (1,4-butanediol) orthophthalate (BPE) polyester polyol has been synthesized by reacting 1,4 butanediol (BDO) and phthalic anhydride (PA). Subsequently the PEUA prepolymer was formed by reacting one mole of BPE with two mole of isophorone diisocyanate (IPDI) followed by end capping with two mole of 2-hydroxyethyl methacrylate (HEMA) in the presence of dibutyltin dilaurate (DBTL) catalyst. Finally, different compositions of crosslinked PEUA/MMA copolymer were prepared by reacting the PEUA prepolymer with MMA, in the presence of 1% azobisisobutyronitrile (AIBN) (w/w) as a chain initiator. The formation of BPE, PEUA and copolymers was confirmed by Fourier transform infrared (FT-IR) and 1H NMR spectroscopy. Water uptake, mechanical, thermal and optical properties of PEUA, PMMA and their copolymers have been also investigated. The impact fractured surface morphology of copolymers was observed using scanning electron microscope (SEM). The results showed that the increased miscibility, improved mechanical and physical properties of copolymer was influenced by the crosslink density. Dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), Haze and transparency of PEUA/MMAcopolymers were determined. The copolymer with 40wt% MMA loading exhibited optimum mechanical and physical properties with respect to the other compositions.