The use of silane coupling agents in mineral-and glass-reinforced composites is well known. They impart improved initial mechanical properties, but, more importantly, they cause mechanical properties to be retained during the use of the composite. The main cause of loss of mechanical properties is attack of water at the interface. Recent research has focused on imparting more durable bonding of the silane coupling agent to both the polymer and the reinforcement. Improved silane coupling agent systems have been developed by utilizing several techniques: blends of hydrophobic silanes with hydrophilic silanes to give greater hydrophobic character; use of 1,2-bis-(trimethoxysilyl)ethane as an additive to give increased siloxane crosslinking; use of more thermally stable silanes such as phenyltrimethoxysilane and N-[2-(vinylbenzylamino)-ethyl]-3-aminopropyltrimethoxysilane to give increased thermal stability; and the use of a carboxy-functional silane with a carboxy-functional polymer and zinc salt to give ionomer bonds at the interface. The effectiveness of these new coupling agent systems was tested by measuring the flexural strength of composites and the adhesion strength of coatings on inorganic substrates. The results show that composites have increased flexural strength and better strength retention during thermal aging; coatings have greater adhesion strength; there is greater resistance of interfacial bonding to degradation by moisture; and thermoplastic composites have better properties after high shear processing.
A short synthetic route to 7-substituted bicyclo[2.2.1] hept-2-enes has been developed. Bicyclo[2.2.l]hept-2-en-7-one has been prepared and was found to react with perbenzoic acid to give the epoxide (XI) rather than the Baeyer-F'illiger product, indicating that there is very little interaction between the carbonyl and the nonconjugated double bond.lli-lI8") (22) (a) S. Winetein and M . Shatavsky, ibid.. 78, 592 (1956); (b) P. R. Story, J . 070. Chem., 26, 287 (1961).The synthesis of la-niethylhydrocortisone, la-methylcortisone, and 1-methylprednisolone are described. The I-methylsubstituent is introduced by conjugate addition of methvl Grignard to the A1-3-keto steroid ( I ) . The configuration of the 1-methyl is assigned by optical rotatory dispersion.
Two new types of solid silomne additives for plastics are described which give improved benefits compared to previous silicone additives. Ultra-high-molecularweight (UHMW) siloxanes are used in the new additives: traditional silicone plastic additives have used much lower molecular-weight silicones. The siloxane is converted into solid forms, either masterbatch pellets or powders, that are easy to feed, or mix, into plastics during compounding, extrusion, or injection molding.Ultra-high-molecular-weight siloxanes can be compounded into masterbatch pellets at higher siloxane concentrations than previously possible, e. g., up to 500h.They impart improved processing and release, lower coefficient of friction, and broader performance latitude compared to conventional lower-molecular-weight silicones. These benefits can be delivered at reduced siloxane levels with increased concentration at the surface interface with a new functionalized UHMW siloxane which provides unique surface segregation characteristics. Ultra-high-molecular-weight siloxanes have been formulated into powders that can also act as processing aids and mechanical property modifiers for highly filled polymers such as fire-retardant systems. This paper uses polyolefins as a model. However, many of the effects shown in polyolefins have also been seen in other resin systems.
New powdered silicone additives for plastics have been developed that give benefits in flame retardant formulations. Cone calorimeter evaluations of thermoplastics, with or without other flame retardant additives, show reduction in rates of heat release, smoke generation, and carbon monoxide evolution. Other benefits that have been observed are: improved processing, reduced torque, reduced build-up on screws, and increased impact strength. The effect of silicone powder additives on the combustion of several thermoplastics will be shown. A suggested mechanism is discussed.
Silicones are specialty chemicals that are often critical in certain production operations. Their primary use in petroleum applications is as foam control agents. The physical and chemical properties of silicones are described, and foam and antifoam theory is discussed. State-of-the-art silicone use in selected key petroleum applications is outlined. The unique properties of silicones that should be considered by petroleum engineers in solving problems in other types of applications are emphasized.
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