Jeon, Jinseok;Sathi, Shibulal Gopi;Kim, Hak Hyun;Nah, Changwoon
来源期刊：Plastics, Rubber and Composites
年/卷/期：2019 / 48 / 3/4
This paper describes the use of a combination of 4, 4' bis(maleimido)diphenylmethane and ZnO as a high-temperature processable vulcanising agent for the short aramid and carbon fibre-filled bromo-isobutylene-isoprene rubber. The fibre breakage analysis, cure characteristics, mechanical, thermal and morphological properties of the composites were evaluated with different fibre loading. The fibre breakage analyses revealed that the aramid fibres have good length retention property compared to carbon fibres. The morphological analysis of the extracted aramid fibres showed severe surface roughness primarily due to fibrillation after shear mixing. The fibrillated aramid fibres lead to aggregation and poor dispersion of the fibres in the rubber matrix. However, fibrillation imparted surface roughness and increased surface area on the aramid fibres which improved the fibre-matrix interaction via mechanical anchoring. On the other hand, the carbon fibre-filled composite showed poor fibre-matrix interaction and inferior strength and modulus.
The complete energy surfaces of the torsion around the central C-O or C-CH2 bonds in diphenyl ether (DPE) and diphenylmethane (DPM) are calculated with semiempirical methods (AM1, MNDO, PM3) and density functional theory (Becke3LYP/3-21G). Stationary points are optimized at the Becke3LYP/6-31G(d) level of theory. The geometry of a very recently published X-ray structure of 4,4'-bis [N-(2,4,6-trimethyl)benzenesulfonamide] diphenylmethane (1), as well as the solid state structures of many other diphenyl ethers and diphenylmethanes, is found in the low-energy regions of the AM1 surfaces of the parent compounds.
The 3-allyl-5,5-dimethylhydantoin (ADMH) was synthesized and characterized by Fourier transform infrared spectroscopy, H-1-nuclear magnetic resonance (NMR), and C-13-NMR spectroscopy. Then, the ADMH was used to modify the N,N '-(4,4 '-diphenylmethane)bismaleimide (BDM)/2,2 '-diallylbisphenol A (DABPA) resin to obtain the BDM/DABPA/ADMH resin system (BDA). The curing behavior was investigated by non-isothermal differential scanning calorimetry and the activation energy (E alpha) was obtained by Kissinger and Ozawa models. The thermomechanical property was measured by dynamic mechanical analysis. Analysis of the data revealed the complexity of the curing reaction, which was firstly dominated by the Ene reaction of allyl and C=C double bond at low and medium temperatures and was further governed by the Diels-Alder reaction and the anionic imide oligomerization occurred at high temperatures. The results demonstrated that 1-BDA had the best thermal and mechanical properties exhibiting excellent modification effect of ADMH.
Background: Very little is known about the dermal uptake of isocyanates, and dermal exposure to isocyanates has been discussed as a factor involved in the induction of respiratory diseases. Objectives: To investigate the dermal uptake of diphenylmethane-4,4'-diisocyanate (4,4'-MDI). Materials & Methods: Four volunteers were dermally exposed to 10,25,49 and 50 mg 4,4'-MDI, respectively, for eight hours. The exposed areas were tape stripped. Urine and blood were biologically monitored for 48 hours. Tape strips, plasma, and urine were analysed by liquid chromatography-mass spectrometry. Results: In total, 35-70% of the applied dose of 4,4'-MDI was absorbed by the skin. Very low fractions of applied dose were found in the tape strips. The 4,4'-MDA concentration in plasma and urine was low, but peaked in urine at 10-14 hours and plasma at 8-32 hours after exposure. Conclusions: 4,4'-MDI is readily absorbed by human skin. Only small fractions of 4,4'-MDI remain as such in the superficial skin layers. The amounts found in blood and urine were only small fractions of the total applied doses which indicates that very small amounts of 4,4'-MDI penetrate the skin and reach the blood stream. The dermal uptake and distribution of 4,4'-MDI is much slower compared to that associated with airway uptake. Our data strongly indicate that formation of 4,4'-MDA from 4,4'-MDI upon reacting with water in the skin can only occur to a very limited extent.