Expert System for Selecting Chemical Protective ... - ACS Publications

Chapter 7 Expert System for Selecting C h e m i c a l Clothing 1

1

1

Protective

1

2

L. H. Keith , M . T. Johnston , C. E. Hudak , M . Conoley , D. B. Walters , and A. T. Prokopetz 2

1

Radian Corporation, P.O. Box 201088, Austin, TX 78720-1088 National Toxicology Program, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, NC 27709

Downloaded by UNIV OF MISSOURI COLUMBIA on April 15, 2018 | https://pubs.acs.org Publication Date: August 29, 1989 | doi: 10.1021/bk-1989-0404.ch007

2

An expert system, named "GlovES+," has been written to provide reliable selections of chemical protective clothing for a wide variety of chemicals. The system conducts "intelligent searches" which emulate a human expert's decision path in evaluating a large database from an electronic publication by Forsberg. GlovES+ is menu-driven, rapid and easy to use, and requires no computer programming knowledge. Complete reports of its searches are made, and it helps the user find additional clothing by suggesting query modifications that will find alternatives. Data presented include manufacturer and product identifi cation, breakthrough times, permeation rates, the type of polymer, and its thickness. Predictions of the best polymers to select when a chemical has not yet been tested may be made with caution, using searches by chemical class instead of by individual chemical. These predictions are useful to polymer chemists, chemical protective clothing manufacturers, and industrial hygienists. Selection of polymers used i n the manufacture of chemical protective clothing (CPC) i s a complex task. It involves evaluating breakthrough times and permeation rates i n conjunction with such task requirements as t a c t i l i t y and resistance to cuts and abrasion. But, i t involves a more basic problem — that of deciding which polymer(s), i n the absence of test data, might be most l i k e l y to r e s i s t permeation by a s p e c i f i c chemical. These decisions are faced not only by users of CPC (e.g., i n d u s t r i a l hygienists), but also by polymer chemists and CPC manufacturers. The National Toxicology Program (NTP) has the r e s p o n s i b i l i t y of evaluating the t o x i c o l o g i c a l properties of many suspect carcinogens, mutagens, and/or teratogens. This i s accomplished by sending test chemicals to contract laboratories f o r t o x i c o l o g i c a l t e s t i n g . As part of the NTP safety program, gloves and other appropriate clothing are recommended whenever possible 0097-6156/89/0404-0063$06.00/0 © 1989 American Chemical Society

Provder; Computer Applications in Applied Polymer Science II ACS Symposium Series; American Chemical Society: Washington, DC, 1989.


64

COMPUTER APPLICATIONS IN APPLIED POLYMER SCIENCE II in documents accompanying the test chemicals. However, i t became clear early i n the program that the limited a v a i l a b i l i t y of chemical permeation data frequently would not permit the r e l i a b l e choice of chemical protective clothing (CPC) for the laboratory workers involved i n handling these potentially hazardous chemicals. With the exception of a few sources (1-2), the preponderance of available data dealt with permeation of commonly used solvents (3-6) and, thus, was of very limited use i n predicting permeation of the more complex NTP chemicals being tested. Many d i f f e r e n t polymers are used by manufacturers of CPC. Furthermore, variations i n the manufacturing process and chemical additives can s i g n i f i c a n t l y affect chemical permeation properties of a garment. As an example, Table I shows the results of permeation tests performed with f i v e common acids against n i t r i l e gloves. Consider the case of 30-70% hydrochloric acid, where s i x models from four companies were tested. Three of the four companies have a n i t r i l e glove which exhibited the "best" Performance Index Number — zero (where breakthrough time must be >4 hours with a permeation rate of 0). Nevertheless, s i g n i f i c a n t differences can also be found among different models from the same company. This i s i l l u s t r a t e d by the three Comasec gloves tested with hydrochloric acid, where only one model (Comatril Super) had no breakthrough after 8 hours of exposure. It i s important to emphasize that often — but not always — the performance of a product with a chemical depends heavily on the manufacturer and a s p e c i f i c product model. A model that performs well with one chemical may perform poorly with another chemical, even when the chemicals are i n the same chemical class. This i s i l l u s t r a t e d by the Edmont Model 37-165 glove which was tested against a l l f i v e acids. This glove shows good protective properties with hydrochloric, perchloric, and phosphoric acids, but exhibits degradation i n n i t r i c and s u l f u r i c acids. From the data presented i n Table I, i t can be seen that the selection of manufacturer and product model i s of greatest importance when selecting n i t r i l e gloves for protection against four of the f i v e acids. With phosphoric acid, a l l of the f i v e models tested show good protective properties. However, based on the v a r i a b i l i t i e s seen with the other acids, one cannot l o g i c a l l y assume that a l l models from a l l manufacturers of n i t r i l e gloves would provide similar degrees of protection. One might therefore conclude that the only absolutely safe selections are those that are based on available, published test data. Nevertheless, professional i n d u s t r i a l hygienists are called upon routinely to select protective clothing that w i l l provide an adequate, i f not absolute, l e v e l of protection, even when permeation data are not available for a s p e c i f i c chemical/polymer combination. Their task i s formidable. It i s also a task that can be performed more easily with the assistance of an expert system. Technical approach Although the NTP

many chemical permeation tests have been conducted over the past several years, the time and cost


by of

7. KEITH ET AL.

65 Expert System for Selecting Chemical Protective Clothing

Table I.


A R M E N T

Performance of N i t r i l e Gloves Versus Common Acids

Class & Number/ test chemical/ MATERIAL NftME

MANUFACTURER & HOXJCr IDEMTFICATICN

Break through Time in minutes

Perm Rate mg/ sq m/ nnii.

I N D E X

330m > 480m 18m > 360m

6600 0 2400 0

4 0 4 0

> 480m

0

Thick Sour ness Degradation ces and in and Comments nm Refs

tfydrochloric Acid, 30-70% G G G G G G

Nitrile Nitrile Nitrile Nitrile Nitrile Nitrile

Comasec Comatril Comasec Comatril Super Comasec Flexitril Ednont 37-165 North LA-142G Pioneer A-14

0.55 0.60 n.a. 0.60 0.38 0 0.56

#40 #40 #40 # 6 DEGRAEAITON # 7 #36

DEGRADATION #55 DEGRADATION #55 #40 #40 #40 DEGRADATION # 6 DEGRADATION #36

Nitric Acid, 30-70% G G G G G G G

Nitrile Nitrile Nitrile Nitrile Nitrile Nitrile Nitrile

Ansell 650 Ansell Challenger Comasec Comatril Comasec Comatril Super Comasec Flexitril Edmont 37-165 Pioneer A-14

18Cm 240n 25m

69060 109440 96600

5 5 5

72m

12060

5

n.a. n.a. 0.55 0.60 n.a. 0.60 0.56

0 0 0 0

0 0 0 0

0.55 0.60 n.a. 0.60

#40 #40 #40 # 6

n.a. n.a. 17040. 5 0.55 0 0 0.60 23000 5 n.a. 0.60

DEGRADATION #55 DEGRADATION #55 #40 #40 #40 DEGRADATION # 6

Perchloric Acid, 30-70% G G G G

Nitrile Nitrile Nitrile Nitrile

Comasec Comatril Comasec Comatril Super Comasec Flexitril Edmont 37-165

> > > >

48Cm 48Cm 480m 360m

Sulfuric Acid, > 70% G G G G G G

Nitrile Nitrile Nitrile Nitrile Nitrile Nitrile

Ansell 650 Ansell Challenger Comasec Comatril Comasec Comatril Super Comasec Flexitril Ednant 37-165

150m > 480m 20m

Itosphoric Acid, > 70% G G G G G

Nitrile Nitrile Nitrile Nitrile Nitrile

Comasec Comatril Comasec Comatril Super Comasec Flexitril Ednont 37-165 Pioneer A-14

> > > > >

48Cm 480m 480m 360m 48Qn

0 0 0 0 0

0 0 0 0 0

0.55 0.60 n.a. 0.60 0.56

Garment G = GLove INDEX = Performance Index Numbers range from 0 (Best) to 5 (Worst). n.a. = Not available.


#40 #40 #40 # 6 #36


66

COMPUTER APPLICATIONS IN APPLIED POLYMER SCIENCE II experimentally measuring chemical permeation for hundreds of compounds per year are prohibitive. Therefore, a small expert system was developed to aid i n the selection process. The usual approach to writing an expert system program by defining s p e c i f i c rules could not be followed. Attempts to derive rules for predicting chemical permeation from multiple products proved f r u i t l e s s . This was due to the wide v a r i a b i l i t y in the data, e.g., the breakthrough times and permeation rates for one chemical with different n i t r i l e gloves would vary from >8 hours of resistance to degradation. This i s apparently due i n part to differences i n manufacturing and i n the a n a l y t i c a l approach used. A different approach, which was successful, involved embedding two expert decision modules within a program designed to search a database drawn from an electronic reference book by K r i s t e r Forsberg(_7). The r e s u l t i n g program, GlovES+, i s a small expert system that has rules for i n t e l l i g e n t l y searching Forsberg's book. It locates CPC by s p e c i f i c manufacturer's model number on the basis of Forsberg s data. The program was written using RuleMaster, an expert system building tool available from Radian Corporation i n Austin, Texas. Forsberg's electronic book consists of information from over 5,000 permeation tests on 640 chemicals or mixtures of chemicals. Over 7,000 breakthrough times and/or permeation rates are recorded. Along with this information are over 25,000 pieces of associated data such as the test material, manufacturer, model number, thickness, comments, a performance index number, and references. Over 200 d i f f e r e n t models of CPC are represented. For convenience of searching for information on similar compounds, chemicals are grouped under 80 chemical classes. These same classes are used with the expert system. Synonyms for many of the compounds are also included where i t i s l i k e l y that the synonym might simplify searching. These same synonyms are also used i n the expert system. f

The GlovES+ Expert System A menu system was designed for screen presentation. Keywords i n the main menu are activated using the cursor keys or the f i r s t l e t t e r i n the keyword. They are then displayed i n a highlighted format, and a question connected with t h e i r usage i s displayed i n an accompanying l i n e . The main menu choices are Chemical, Task, Attributes, Search, Match, Options, Print, and Quit. An i n i t i a l set of Task Requirements and Chemical Attributes i s generated by the program from data i n the database. When searches are conducted using chemical class, however, a l l of the chemical attributes are i n i t i a l l y recorded as "U" for unknown. These, along with a l l of the parameters i n the Task Requirements segment, can be changed by the user at w i l l . Such changes made by a user to the Chemical Attributes for a class or s p e c i f i c chemical are not recorded permanently i n the database because the user i s overriding the system's best information on a compound. Nevertheless, the opportunity to change the chemical attributes during a session i s given to the user.



7. KEITH ETAL.

Expert System for Selecting Chemical Protective Clothing

The F l function key toggles a help menu i n and out of the bottom section of the screen and provides guidance to the user i n the s p e c i f i c a t i o n of v a l i d entries f o r Task Requirements and Chemical Attributes. In fact, when chemical class searches are chosen, the user should change as many of the "U" designations i n Chemical Attributes as possible. When a "U" i s l e f t , the system assigns a "worst case" value to that attribute i n order to make the most conservative choice of materials. Thus, i f the answer to the question, "Is the chemical a known or potential carcinogen?" i s "U," the system assigns i t a "yes" because that i s the worst case and w i l l produce the most conservative selections when the database i s evaluated for materials that have been tested against the class of compounds under consideration. Chemical class searches can be helpful when making selections of materials f o r use with chemicals which have not been tested f o r permeation. By extrapolating the information provided by the program f o r a chemical class, one can (with caution) often select materials that w i l l have better protective q u a l i t i e s than those material selected without this information. However, the uncertainties i l l u s t r a t e d from the data i n Table I are inherent i n any polymer selections made this way. The program also has a Matching u t i l i t y that records the results of two or more searches, stores, and compares them. Matches may be made by material (polymer) or by product model. The Matching u t i l i t y eliminates test records that do not appear i n a l l of the searches that were made. Matching by product model always eliminates more models as the number of searches increases. Conversely, matching by polymer may increase or decrease the number of models found as the number of searches increases. Complete reports of the searches and matches are formatted by the program. These can be copied to a disk f i l e or printed. An Example of the Matching U t i l i t y A matching search was made of the data available f o r two highly polar classes of chemicals — polyamines and polyalcohols — to find the polymer l i k e l y to be most resistant to chemical permeation by such highly polar compounds. The task requirements specified were as follows: T a c t i l i t y : Not important Aqueous Protection: No Cut/Abrasion Resistance: No Consider A l l Types of Garments: Yes Time Required f o r Protection: 1 Hour The results of searches of these two chemical classes matched by polymer are presented i n Table I I . Three candidate polymers (natural rubber, neoprene, and n i t r i l e ) were found with 15 models giving acceptable test data. Table II represents a summary report. Data from a complete report are shown i n Table I I I . It l i s t s a l l of the chemicals


61


68

COMPUTER APPLICATIONS IN APPLIED POLYMER SCIENCE II

Table I I .

Polyamines and Polyalcohols Matched by Material (Polymer)

Material

Garment Model

Chemical Class

Natural Rubber Natural Rubber Natural Rubber Natural Rubber Neoprene Neoprene Neoprene Neoprene Neoprene Nitrile Nitrile Nitrile Nitrile Nitrile Nitrile

Ackwell 5-109 Comasec Flexigum Edmont 36-124 Pioneer L-118 Edmont 29-870 Comasec Comoprene Edmont 29-840 Edmont Neox Pioneer N-44 Edmont 37-155 Comasec Comatril Comasec Comatril Super Comasec F l e x i t r i l Edmont 37-165 Pioneer A-14

polyamines polyalcohols polyalcohols polyalcohols polyamines polyalcohols polyalcohols polyalcohols polyalcohols polyamines & polyalcohols polyalcohols polyalcohols polyalcohols polyalcohols polyalcohols



Natural Rubber Natural Rubber Natural Rubber Natural Rubber Neoprene Neoprene Neoprene Neoprene Neoprene Neoprene Neoprene Neoprene Nitrile Nitrile Nitrile Nitrile

Material (V) (V) (V) (V) CM) CM) CM) CM) CM) CM) (M) (M) CM) (M) (M) CM)

Tactility Rating

F A 60

Exposure Garment Task Time

Vendor and Model

Y M

Skin Absorber Irritant

tetraethylenepenfami ne 1,6-hexanediamine, 30-70% 1,6-hexanerii ami ne,

Expert System for Selecting Chemical Protective ... - ACS Publications

Recommend Documents