Polyamide adhesive shear strength

Adhesion studies of epoxy resins modified with high modulus and high glass transition temperature thermoplastics have shown adhesion can reach or even exceed that of the unmodified resin. The use of flexible polyamides or flexible epoxides resulted in shear strength increases in epoxy systems employed by Cunliffe et al. [144],polyethersulfones [18,145],polyetherimides [109,146,147], and polyetherketones [148-150]. 

Polyamide cured DGEBA epoxies provide improved flexibility, moisture resistance, and adhesion over aliphatic amines alone. However, polyamide cured epoxies are generally inferior in thermal resistance and shear strength due to the reduction in crosslink density. Polyamide cured epoxies lose structural strength rapidly with increasing temperatures and... 

As with amidoamine and polyamide cured adhesives, epoxy resins cured with aliphatic amines exhibit tensile shear strength that is dependent on the type of filler and concentration. Table 11.10 shows the effect of filler loading on strength of a simple general-purpose, room temperature curing epoxy adhesive composed of liquid DGEBA epoxy mixed with 10 pph of a tertiary amine. 

General-purpose epoxy adhesive with amidoamine curing agents Effect of fillers on tensile shear strength of polyamide cured epoxy... 

The mechanical properties of the surface-modified products were examined by a special shear test. After reactive surface modification under optimised chemical and technological conditions, the test specimens were cut and the pieces were bonded by special adhesives. The coimected pieces were examined in a shear test and the shear strength was determined in dependence on the chemical and processing conditions. The best results for polyamides were obtained for polyacrylic acid as the modifier with an increase of the shear strength from 28 MPa (non-modified polyamide) up to 37 MPa for polyacrylic acid-modified polyamide surfaces. 

Epoxy-polyamide and epoxy-polysulfide adhesives have been used successfully for bonding properly treated PC l EE. An epoxy-polyamide adhesive (Epon 828/Versamid 125 60 40 ratio) cured for 16 hours at room temperature and followed by 4 hours at 74 C has given tensile-shear strengths of... 

Peel resistance. The straight epoxies cured by either polyamines (amides) or anhydride are poor in peel. Polyvinyl formal-phenol formaldehyde (P/F) and butyral-P/F are moderate but the peel varies with the P/F content. As the P/F content increases, room temperature lap-shear and peel strength decrease but these properties improve at elevated temperatures. The epoxy-polyamides (epoxy-nylon) such as FM1000 (Cyanamid Corp.) give extremely good peel resistance under dry conditions. Hockney (1970) quotes 511N for an adhesive of this type with a strip 25 4 mm wide, peeled at 90°. The peeling... 

Fig. 115. Strength of lap shear joints after exposure to 97% relative humidity at 43°C. Adhesive epoxy-polyamide, FMIOOO (Cyanamid International Corp.) (adapted from Butt and Cotter, 1976).

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