Silicone strength, elongation

Since most silicone adhesives and sealants are elastomeric in nature, their physical property testing often parallels classical rubber testing approaches. Common tests include durometer, tensile strength, elongation, and modulus. Several methods are available for the measurement of rubber properties, but the most commonly used are the American Society for Testing and Materials (ASTM) D-412, Test Method for Rubber Properties in Tension, and the ASTM C-661, Standard Test for Indentation Hardness of Elastomeric-Type Sealants by Means of a Durometer. These properties vary widely with the product... 

Wacker Chemie s silicone-based torque-redudng aids (also mentioned in Section 11.1.1) have also been shown to be effective for improving the impact strength, elongation, and abrasion resistance of PE and PP compounds that are highly filled with CaCOs, talc, or ATH (see Table 11.2) [11-9]. 

The standard stress-strain curve described in Chapter 3 displays important characteristics for rigid or elastomeric materials. Since elastomeric designs usually do not need high strengths, elongation is important and can be related to flexibility and softness. Elastomers are capable of extreme elastic deformation at low levels of stress. This strain is not proportional to stress (see Figs. 6-26 and 6-27). Like solid plastics, the elastomers become brittle below their Tg, which is in the range of - 20°C ( 4 F) for most rubbers and about -60°C (-75°F) for natural and silicone rubbers. 

Aluminum drillpipe is generally made of 2014 type aluminum-copper alloy. Composition of this alloy is 0.50 to 1.20% silicon, 1.00% iron maximum, 3.90 to 5.0% copper, 0.40 to 1.20% manganese, 0.25% zinc maximum and 0.05% titanium. The alloy is heat treated to T6 conditions that represent 64 ksi tensile strength, 58 Ksi yield strength, 7% elongation and a Hbn of 135- Aluminum drillpipe generally comes with steel tool joints that are threaded on to ensure maximum strength that cannot be attained with aluminum joints. 

Similar types of lamellar morphologies were observed for triblock copolymers of diphenylsiloxane and dimethylsiloxane having 40 wt% polydiphenylsiloxane, using electron microscopy, 47-148>. The lamellae thickness was approximately equal to the chain length of the rigid polydiphenylsiloxane blocks. These copolymers showed elastomeric properties comparable to those of conventional silica-reinforced, chemically crosslinked silicone rubbers. Tensile tests yielded an initial modulus of 0.5-1 MPa, tensile strength of 6-7 MPa and ultimate elongation between 400 and 800 %. 

Epoxy-silicone hybrid resins (Fig. 7.4) have generally been developed for use in the molding of microelectronic packages. These resins have moderate strength but exhibit a degree of elongation of about 60 percent at break. 

Figure 8.5 depicts representative ranges of bond strength and elongations for typical structural adhesives such as epoxies, methacrylate, polyurethanes, and silicones. The silyl-epoxy hybrids conveniently fill the gap between the silicones and polyurethanes. 

The bare vulcanized silicone pol)mier, a polydimethylsiloxane network, shows only a low mechanical strength. Adding 30 wt. % of fumed silica by mixing and dispersing increases the elongation and stress at break by a factor larger than 10 (Fig. 8). 

---