Thermoplastic chosen for breathing apparatus

Edited by the Engineeringtalk editorial team Aug 8, 2007

A breathing apparatus application demanded a thermoplastic that would withstand even the most rugged use while providing protection against radio interference.

When Biomarine , a division of Neutronics was designing the housing for its BioPak 240R self contained breathing apparatus (SCBA), it turned to Premix Thermoplastics for help in developing a thermoplastic compound that would meet the unit's demanding requirements for withstanding even the most rugged use while providing protection against radio interference.

Certified by NIOSH/MSHA, EN136/EN137/EN145 and the Chinese Mining Authority, the new four-hour BioPak 240R is the industry's most advanced and easiest to use long-duration rebreather on the market.

With its six-litre tidal volume, disposable solid CO2 scrubbers, and quick-change coolant, the 240R represents the most significant advancement in closed circuit, self-contained breathing apparatus technology in over a decade.

Overall user safety and comfort has also been dramatically increased over standard SCBAs with an ergonomic design and advanced status/warning systems.

The BioPak 240R rebreather is designed for use in mine and tunnel rescue, industrial accidents, Hazmat clean-up, search and rescue, and military or homeland security operations.

For the housing of the BioPak 240R, Biomarine needed a material whose properties included the ability to handle impact requirements and withstand continuous temperatures of 88C without deforming.

In addition, the material had to withstand 15 seconds of direct flame without burning or showing after glow, or flame after the flame is removed.

Using a matrix approach to developing a customised compound for the housing, Premix engineers considered a number of options.

Initially, they thought PRE-ELEC ESD 14-000 would be an excellent choice due its high impact resistance, heat deflection and colourability.

However, they quickly ruled it out because the flame test showed that the inherently dissipative polymer (IDP) in this PC alloy would release some of its chemically bound water molecules and cause blistering on the surface of the BioPak, which was unacceptable.

Another option considered was PRE-ELEC 14-000, a carbon black polycarbonate compound that met all the physical, thermal and electrical requirements.

However, this was ruled out because Biomarine wanted to manufacture BioPak with some colour in it.

Next on the list for consideration was PRE-ELEC 14-031, which could be easily coloured grey for the housing but its impact resistance was too low.

Even with impact modification, PRE-ELEC 14-031 would not meet the requirements for the application.

This left only one option, PRE-ELEC 14-040, a stainless steel fibre polycarbonate - but even this compound needed impact modification to meet the impact properties.

After strenuous testing, the impact-modified compound, PRE-ELEC 14-040-HI, became the product of choice.

Premix supplies it in three colours, black, grey and yellow.

The ability to offer so many conductive and static dissipative compounds allows Premix to use this type of matrix approach when customising compounds.

By tabulating the requirements versus the abilities of its individual compounds, it is possible to develop special compounds very quickly.

It took less than 12 weeks to have a material qualified for the housing of Biomarine's SCBA.