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4,4'-Methylenebis (2-chloroaniline) (MBOCA) is used as a curing agent in industries that primarily produce castable polyurethane parts; thus, occupational exposure may occur during the manufacturing processes in these industries [Agency for Toxic Substances and Disease Registry (ATSDR) 1994].
The manufacturing of MBOCA includes the reaction, neutralization, washing, purification, and packing processes.
An area sampling program to monitor MBOCA levels in the work environment of this MBOCA manufacturing factory was initiated by the Taiwan Institute of Occupational Safety and Health (IOSH), Council of Labor Affairs (IOSH 2003a).
The concentration of MBOCA was highest in the purification area (0.23-0.41 mg/[m.sup.3], n = 2), followed by the washing area (< 0.02-0.08 mg/[m.sup.3], n = 7) and the neutralization area (< 0.05-0.06 mg/[m.sup.3], n = 2) (IOSH 2003a).
In addition to environmental monitoring, the Taiwan IOSH also collected workers' urine to monitor MBOCA concentrations.
The total urine MBOCA concentrations ranged from 267.9 to 15701.1 [micro]g/g creatinine, with a mean of 5,544 [micro]g/g creatinine (IOSH 2003b).
Although the production of MBOCA in the United States ceased in 1982, MBOCA is still manufactured in other countries.
Environmental monitoring of MBOCA levels in ambient air performed in the present study showed that the concentration was high in the purification process area (0.23-0.41 mg/[m.sup.3]) and exceeded the OSHA permissible exposure level (0.22 mg/[m.sup.3]) and NIOSH's recommended exposure level of MBOCA (3 mg/[m.sup.3] as a 10-hr time-weighted average) (Ward et al.
These prepolymers have been shown to be dynamically superior to conventional prepolymers when MBOCA is the crosslinker (ref.
In general, however, the best overall result is obtained at a 95% cure ratio and a cure schedule of 48 hours at 130[degrees]C, which is a departure from the conditions commonly used with MBOCA cured elastomers.
Unfortunately, a direct comparison with MBOCA cured elastomers was not possible and it is difficult to say if the result is a real effect of MCDEA or an artifact of the test.
When compared to a MBOCA cured, low oligomer PTMEG resin system (Airthane PET95A) which is known to perform well in dynamic environments, however, the MCDEA candidates show clear improvement.
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