ABSTRACT
Polyurethane adhesives are currently used in Apache aviator masks to secure polycarbonate lenses to a bromobutyl-natural rubber face piece. This study examined the rupture behavior of polycarbonate(pc)components bonded to butyl-rubber with polyurethane adhesives. Composites were fabricated and destructively tested to reveal differences in failure mode and rupture strength as a function of surface preparation, curing regime, and polyisocyanate-polyol formulations.
Alternative polyurethane adhesives packaged in premeasured assemblies offer greater ease of application and were investigated to determine if the replacement adhesive could be used in lieu of the original adhesive employed during the manufacturing process. Data on the rupture strength of polycarbonate-adhesive-rubber joints was collected to compare LORD 7500 and Lord 7540(pre-packaged) adhesive. Rubber components of die prototypes were abraded with 80 grit, 100 grit, or no surface abrasion and bonded to polycarbonate with adhesive. Specimens were cured at temperatures of 63 Celsius or ambient temperature(23 C). All polycarbonate surfaces were abraded with sand paper and treated with Lord 7701 adhesion promoter.
The rubber-adhesive-polycarbonate rupture strength results, loads reported in pounds are listed below(average of all specimens with error in measurement reported as 95% confidence limit).Loads were applied perpendicular to the bond surface plane (1 inch diameter right circular cylindrical surface) in an Instron Load cell. Grips of the load cell were moving apart at a constant rate of 0.15 inches per minute. Load versus displacement results were recorded for seventy-five specimens and correlated with failure mode. Distinct failure modes for heat-cured versus ambient-cured composites are evident in the specimens(photographs are included in the body of the report.)
https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429332609/b489e897-3e47-4364-b629-cdcef395eff2/content/pg389_1.jpg" xmlns:xlink="https://www.w3.org/1999/xlink"/>Load measurements indicate both adhesives are 390adequate for securing optical lenses within the aviator mask. To improve polyurethane adhesive bonding in the aviator mask application, curing at 63 degrees Celsius for 18 to 24 hours is recommended. Load to Induce Rupture https://www.niso.org/standards/z39-96/ns/oasis-exchange/table">
Adhesive
Surface
Curing
Separation Mode
Load at Failure
7500
100 grit
63 C
rubber tearing
261+/−31lbs
7540
100 grit
63 C
adhesive tear from pc
239+/−41bs
7500
100 grit
23 C
adhesive peeled from rubber
195+/−21lbs
7540
80 grit
23 C
adhesive peeled from rubber
177+/−36 lbs
7540
100 grit
23 C
adhesive peeled from rubber
170+/−19 lbs
7500
80 grit
23 C
adhesive peeled from rubber
149+/−15 lbs
