Polycarbonate (Lexan) is always a better choice as it is both stronger and less likely to fracture as does plexiglass (acrylic). That being said, a shield is really only as strong as it's supporting structure and portable shields (I.e. that can be moved around) are really often useless except to protect against vacuum implosion and minor splashes. Even broken glass, while it won't penetrate, will often cause them to tip over. And of course, none of them provide any realistic fire protection.
I would suggest your boss read and take to heart he NPFA 45 guidance on the subject noting particularly the requirements highlighted in red.
12.3.2 Performance of Experiments or Demonstrations.
22.214.171.124 Experiments or demonstrations for students involving
open flames or fire, or the use of flammable, reactive, toxic, or
corrosive materials, shall be performed by a knowledgeable
instructor and in accordance with 126.96.36.199.1, and 188.8.131.52.2,
184.108.40.206.3, or 220.127.116.11.4.
18.104.22.168.1 Experiments or demonstrations shall be performed
in a location that does not block access to the primary means of
egress from the laboratory work area.
22.214.171.124.2 Experiments or demonstrations that involve or
produce hazardous quantities of fumes, vapors, particulates, or
gases shall be performed in a chemical fume hood or other
ventilation device, including demonstration hoods or other
devices that meet the requirements of 2.1.1 of ANSI/AIHA
Z9.5, Laboratory Ventilation, that is able to capture the materials
126.96.36.199.3 Experiments or demonstrations involving chemicals
that are performed outside a fume hood where the separation
distance in 188.8.131.52.4 is not possible shall be performed
behind an impact-resistant plastic or tempered-glass safety
shield that meets both of the following:
(1) The shield shall be at least 0.610 m (24 in.) high and shall
wrap 180 degrees around the hazard or extend at least
0.305 m (12 in.) beyond the hazard in both directions.
(2) The shield shall be secured to the work surface with bolts
or clamps to keep it in place.
184.108.40.206.4 Experiments or demonstrations involving chemicals
that are performed outside a fume hood where a shield is not
utilized shall be performed in a location that is at least 3.05 m
(10 ft) from students.
220.127.116.11 In educational and instructional laboratories where
experiments are conducted by students, the instructor shall be
responsible for conducting a safety briefing prior to the start of
each experiment to review the hazards of the chemicals used,
the personal protective equipment required for
Pilot plant and laboratory consulting, safety, design,reviews, and training
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From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU> On Behalf Of Heather Zimmer
Sent: Tuesday, September 8, 2020 2:55 PM
Subject: [DCHAS-L] demonstration safety shield material
Hi everyone -
We are putting up plexi shields to that clamp on the bench to divide them in half so students can work at opposite ends of the bench, facing each other. My department chair just suggested that we order some of them in a "thicker plexi" so they can be repurposed as demonstration shields, something I have been advocating for for several years now. Looking online, the shields I am finding are listed as "thick polycarbonate" (one site specifically said 3/16 in) or "acrylic". Is there something more specific that you can recommend? Members of my department really like to push beyond the boundaries of what I consider safe for chemistry demos, so I would love to protect students however I can.
Heather Wages Zimmer
Norris House Advisor
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