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Table 1: Characteristics and Costs for Commercially Available Chemical Protective Glove Materials that may be used with Methylene Chloride Material Diffusion Glove Breakthrough Surface Exposure Cost Coefficient, Thickness, I Time, 1 Concentration, Rate, (USS/ D (cm) hr S. (g/h) Pair) (10 cm/s) (g/cm') Multilayer" 0.0095 0.007 24 11.1 0.43 4.19 Poly(vinyl 4.46 0.075 0.68 24 alcohol) Viton rubber 3.0 0.025 0.97 0.1 0.35 72.00 Butyl rubber 110 0.090 0.34 0.44 15.5 58.00 Neoprene 92 0.075 0.28 3.53 125 3.35 rubber Poly(vinyl 176 0.070 0.13 1.59 115 3.21 chloride) Nitrile 157 0.040 0.05 2.68 303 1.56 rubber *Silver Shield For a linear concentration profile the equation can be expressed as follows: - J = -D xb For a linear concentration profile the equation can be expressed as follows: - J = -D xa - xb where "a" and "b" subscripts can be used to refer to glove surfaces in contact with methylene chloride and with the hand, respectively. If the glove thickness is l= xa- xb, this can then be written as: Ca - Cb J = -DT and the exposure rater, is equal to the product of the diffusion flux and the total glove surface area (A) so that: re-JA- DA ( Ca- Cb) 1 An important point to consider is: what is an acceptable exposure rate? Based on airbome exposure limits, set by Occupational Safety and Health Administration (OSHA) of the United states, the maximum allowable exposure (r.) to methylene 1.hr 3. Which of the glove materials listed in this study meet the standard guidelines set by OSHA for methylene chloride? Explain. (2 mark) 4. From the tabular data given in the write-up which glove would be an ideal choice? Why? (2 marks) 5. As an exercise, calculate the breakthrough time and exposure rate for Polyvinyl alcohol(PVA) using the data given in the table applying the relevant equations given in the article. Show your calculations. You may assume that all of the methylene chloride is immediately absorbed by the skin and swept away by the blood stream. (2x2 -4 marks) 6. Using the schematic diagram shown below, calculate the diffusive flux of methylene chloride through a butyl rubber glove of glove thickness 1 = 0.04 cm and given that surface concentrations are Ci=0.44g/cm' and C2=0.02g/cm?. Hift: Use the value for Diffusion coefficient in butyl rubber from the table in your document. Assume a linear concentration gradient ( 2 marks). alove versity skin