Лако-красочные материалы — производство

Applications for silicones in bonding are numerous. Generally, one sealant will not bond to all substrates and it is common practice to develop new formulations to meet the ever — increasing list of requirements. In some instances primers are used for certain substrates, but silicones are usually self-priming. This self-priming feature is important from the […]

As mentioned in the processing section, silicone sealants and adhesives generally contain polydimethylsiloxane (PDMS) polymer, cross-linkers, fillers, catalysts, and other addi­tives. These additives may be pigments, plasticizers (often unreactive PDMS polymers), and adhesion additives (such as silane coupling agents). Given below are simple formula­tions and properties (Table 2) for oxime-cured silicone sealants [8]. In these […]

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 […]

Silicone adhesives and sealants typically contain polymer, fillers, cross-linker, catalyst, and other additives. The most common fillers are the reinforcing fumed silicas or the less reinforcing grades of calcium carbonate. Other fillers and pigments, such as carbon black and titanium dioxide, are also used. Silicones are typically made in high shear, vertical change can mixers, […]

Silicones are available in one — and multicomponent forms. The one-component types are commercially the most important and will be the focus of most of this discussion. These products, which generally cure by reaction with atmospheric moisture, are called RTV (room-temperature vulcanizing) sealants or adhesives. The surface cure rate of these pro­ducts is a function […]

Loren D. Lower and Jerome M. Klosowski Dow Corning Corporation, Midland, Michigan, U. S.A. I. INTRODUCTION Silicone adhesives and sealants were introduced approximately 40 years ago and many of the silicones used in the early days are still performing. Products are available in a variety of forms, from pastelike materials to flowable adhesives. Both single- […]

When fully cured, cyanoacrylates will meet class VI standards for plastics, the highest class of safety and biocompatibility as defined by the United States Pharmacopoeia (USP). B. Thermal Conductivity Cyanoacrylates are essentially thermally nonconductive materials. The value for a typical methyl-grade cyanoacrylate is 2.1 (Btu-in.)/(hr-ft[16]-°F). C. Durability Assemblies joined with cyanoacrylate adhesives exhibit good long-term […]

Polyolefin bonding has been advanced using cyanoacrylates through the use of surface primers. These primers promote adhesion to untreated polyethylene (PE), polypropylene (PP), and EPDM rubber. Table 7 shows comparison bonds using standard industrial — grade cyanoacrylates. PE/PE PP/PP Lap shear (psi) Primed Unprimed Primed Unprimed After 15 min, room temperature 90 50 185 52 […]

The new range of surface-insensitive cyanoacrylates provides ultrafast cures independent of gap. In addition, these cyanoacrylates will rapidly bond acidic and low-energy surfaces. The fast cure also minimizes the occurrence of frosting and fogging. Table 6 shows a comparison of these new surface-insensitive materials compared to a standard ethyl — grade cyanoacrylate. These products are […]

A. New Flexible Cyanoacrylates New cyanoacrylate compounds exhibit good adhesion to various plastics and elastomeric surfaces, such as Mylar, copper foil, and vinyl films. These products show better impact resistance and good flexibility compared to standard cyanoacrylates, good resistance to cracking under flexing or bending, and a longer open time than that of standard products. […]