Lap shear adhesion

Fig. I. Comparison of unprimed and eleetroprimed single lap-shear adhesive joint strengths for steel coupons bonded with imidazole-cured epoxy [43].

In essence, the durability of metal/adhesive joints is governed primarily by the combination of substrate, surface preparation, environmental exposure and choice of adhesive. As stated earlier, the choice of the two-part nitrile rubber modified epoxy system (Hughes Chem - PPG) was a fixed variable, meeting the requirement of initial joint strength and cure cycle and was not, at this time, examined as a reason for joint failure. Durability, as influenced by substrate, surface preparation, and environmental exposure were examined in this study using results obtained from accelerated exposure of single lap shear adhesive joints. 

The aging environments in which cured lap shear adhesive bonds were exposed included ... 

Yoon TH, Arnold CA, McGrath JE (1989) Titanium 6/4 single lap shear adhesive performance of polyimide homopolymers and poly(siloxane imide) segmented copolymers. Mater Res Soc Symp Proc 153 (Interfaces Polym Met Ceram) 211... 

Berger EJ(1991)A method of determining the surface acidity of polymeric and metallic materials and its application to lap shear adhesion. 

D 3528 Test Method for Strength Properties of Double Lap Shear Adhesive Joints by... 

PA-6 (80) / PS (10-16) / SMA (2% MA) (4-10) internal mixer at 240°C / torque rheometry / SEM / selective solvent extraction / DSC / morphological stability to annealing / lap shear adhesion / comparison to PA-PS block copolymer compatibilized blends Park et at., 1992... 

PA/PS blends have been compatibilized through block copolymer formation between amine-terminated PA and anhydride-terminated PS. Anhydride end-groups were introduced into PS through reaction of either anion-terminated PS or hydroxy-terminated PS with trimeUitic anhydride chloride. Park et al. [1992] blended 80 parts PA-6 with 10-16 parts PS and 4-10 parts anhydride-terminated PS in an internal mixer at 240°C. The blends were characterized by torque rheometry, SEM, selective solvent extraction, DSC, morphological stability to annealing, and lap shear adhesion. The effect... 

Dharmarajan et al. [1995] have prepared com-patibilized blends of PO/PP/styrene copolymer. Blends of 100-0 parts PP, 0-100 parts SMA, 0-15 parts EP-g-l° amine (0.3 mol % amine), and 0-5 parts PP-2° amine (0.4 wt% amine) were combined in an internal mixer at 220°C. Blends were characterized by FTIR, DMTA, TEM, rheology, mechanical properties, lap shear adhesion, and paint adhesion. Properties were compared for blends containing either of the two amine-functionalized polymers alone. 

EMAc (100-0) / vinyl-functionaUzed PDMS (3.8% vinyl) (0-100) LDPE (50) / EMAc (0-10) / vinyl-functionalized PDMS (3.8% vinyl) (50) internal mixer at 85-180°C / capillary rheometry / DMA/FTIR internal mixer at 180°C / mechanical properties / DMA / FTIR / SEM / WAXS / X-ray diffraction / lap shear adhesion Bhattacharya Cl/., 1995 SaatraetaL, 1993a Santra et aL, 1993b... 

Figure 7.5 Effect of ageing at 50 °C, 50% RH on lap-shear adhesion of polyurethane/ PVC (a) and polyurethane/ABS (o) joints. Polyurethane adhesive cured according to...

For contact adhesives, acrylic latexes compare favorably to Neoprene A latex as well as to the solvent-based Neoprene. As expected, the latexes dry slower than the solvent-based Neoprene however, the drying time can be shortened through formulation. In terms of lap shear adhesion, acrylic latexes are better than Neoprene A latex. In addition, acrylic latexes offer comparable performance, freeze-thaw stability, nonflammability, ease of handling, and ease of cleanup. 

ASTM D3528-96 (2002) Standard test method for strength properties of double lap shear adhesive joints by tension loading. 

PA-6 (100-0)/SAN (0-100) or ABS/SMA (14 % or 25 % MA) (0-10) or imidized acrylate copolymer with 1 % MA content or SAN-co-IPO (1 % oxazoline) Double extrusion on SSE/torque rheometry/mechanical properties/ selective solvent extraction/SEM/ lap shear adhesion/SAN -l- SMA double extruded in separate step followed by extrusion with PA Triacca et al. 1991... 

LDPE (50)/EMAc (0-10)/ vinyl-functionalized PDMS (3.8 % vinyl) (50) Internal mixer at 180 °C/mechanical properties/DMA/FTIR/SEM/WAXS/X-ray diffraction/lap shear adhesion Santra et al. 1993b... 

ASTM (2004), D3528-96 (reapproved 2002), Standard test method for Strength properties of double lap shear adhesive joints by tension loading , in Annual Book of ASTM Standards, 2004 edn. West Conshohocken, PA ASTM International. 

ASTM D 5868-01 (2008), Standard test method for lap shear adhesion for fiber reinforced plastic (FRP) bonding, ASTM, West Conshohocken, PA. 

PC/SAN blends have been found to exhibit maximal properties at 25-27 wt% AN. This was evidenced by the improvanent in lap shear adhesion of compression-molded laminated sheets of PC and SAN copolymers, and in tensile modulus and elongation at break, improved notched impact Izod strength, and inward shifts of the glass transition temperatures of PC and SAN blend components with respect to their homopolymer values. PC and SAN were found to be partially miscible. The 25-27 wt% AN was found close to the azeotropic composition of SAN. 

A practical use of Saret 633 as an internal adhesion promoter is shown in Table 8.13 which gives a formulation for a pumpable sealant based on liquid EPDM [24]. This formulation not only gives excellent adhesion to steel, but bonds strongly to oily steel as well. In this example, lap shear adhesion was determined using steel coupons, overlapped 2.5 cm, with a spacer to form a uniform sealant thickness of 0.18 cm. Light pressure was applied so that the upper coupon would be pressed against the spacer. The sealant was then cured at 160 °C for 25 minutes. To test for bonding to an oily surface, the steel... 

Lap shear adhesion was measured using steel coupons overlapped 2.5 cm. Spacers were used between the coupons to obtain a uniform sealant thickness of 0.18 cm. Light pressure was applied so the upper coupon would bear evenly on the spacers. The sealant compounds were then cured at 160 °C for 25 minutes and then tested at room temperature. 

Fig. 10. Double-lap shear adhesive specimen configurations (ASTM D3528).

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