Blister method

Fracture energy required to separate polyurethane from a mold was studied by a blister method. It was foimd that the energy required for separation is determined by the surface roughness of a mold, the peeling rate, and the amoimt and the t5qje of release agent. 

Silicone fluids (polydimethylsiloxane) and silicone resins are in popular use in polyurethanes. They are usually applied from solvent-based systems. Figure 11.32 shows that silicone fluids having lower viscosity require less force to remove molding (the blister method was used to measure adhesion of polyurethane to the mold material). Figure 11.33 shows that 92% of silicone was absorbed by polyurethane and only 8% was detected by ATR-IR. This absorp-... 

Blister method was also used for studying esters of fatty acids as potential mold release materials. Selection of solvent for an active compound is very important because it determines the quality of film produced on the mold sur-face. Materials differ in their adherence to either a mold or molded part. For example, some stearyl stearate was found in polyurethane part but most has resided on the mold surface, whereas myristyl m5uistate was only present on the mold surface. Figure 10.15 shows the effect of concentration of stearic acid on the surface of a mold on the release properties of polyurethane. ... 

Fig. 1, Schematic of commonly u.sed methods for testing the strength of adhesive joints, (a) Peel test. Note that the peel angle can be changed depending on the test requirements, (b) Double overlap shear test. In this test, the failure is predominantly mode II. (c) Single overlap shear test. In this test the failure mode is mixture of mode I and mode II. (d) Blister test.

To prevent or minimize hydrogen blistering and embrittlement, the following methods should be considered ... 

The processes are dealt with fully in Chapters 11, 14 and 15. Because many paint systems include an initial surface pretreatment, e.g. chromated aluminium or phosphated steel, BS4479 1990, Part 3 deals with conversion coatings and should be consulted by designers. Whatever the method of treatment, liquids must be able to drain quickly and freely from the surfaces. Crevices where liquids can become entrapped are best avoided. The surface configuration needs to be such that active solutions can be washed away, leaving the surface to be painted completely free from unreacted pretreatment solution. Failure to achieve the requisite level of freedom from the surplus chemicals causes paint failure, e.g. osmotic blistering. 

The solution was applied to the surface of cold-rolled steel, dip-galvanized steel sheet, and aluminum strip for degreasing and passivating in a single operation at 40°C for 90 s. The surfaces were then lacquered (85-100 pm thickness) and tested in a salt-spray test for 480 h without showing subsurface migration and blistering. The method is especially useful in the automobile industry for coated sheet [191]. 

M.A. Dempster, B.F. MacDonald, P.J. Gemperline and N.R. Boyer, A near-infrared reflectance analysis method for the non invasive identification of film-coated and non-film-coated, blister-packed tablets. Anal. Chim. Acta, 310 (1995) 43-51. 

Do not use with heating pads or other methods of heat application because burning or blistering may occur. 

Immersion according to Hempel Method. Half the panel immersed in fresh water and half the panel exposed to vapour. Possible weak adhesion is hereby provoked. The panels are applied, cured for 7 days and immersed in potable water for 2 weeks. After exposure the panels are immediately examined for blistering and adhesion (Knife test, X-cut, -cut). 

It can be seen that for severely degraded specimens, both the harmonic analysis and Impedance techniques are capable of detecting the presence of gross corrosion. The harmonics method provides a reasonable estimation of the corrosion rate when the Impedance data exhibits Warburg type behaviour. For less severely degraded specimens, especially those exhibiting blister attack, the Impedance method Is not as successful as the harmonic analysis technique. 

Figure 26 AFM micrograph of DLC film on Ir(lOO) prepared by IBD method (100 eV followed by thermal annealing at 600 °C under He gas environment. After annealing, DLC film suffered from blistering because of immiscibility between C and Ir. Size of the micrograph is 9.85 x 9.85 pm. ...

Water blasting will remove substances such as loose and blistered paints, loose rust, grease and other accumulated residue. Although water blasting will not produce a surface equivalent to that produced by sand blasting, it is nevertheless an economical method of cleaning for lining application. 

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