Peter G. Pape

Methods for improving the performance of silane coupling agents

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 io...

Silicones: Unique Chemicals for Petroleum Processing

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.

New Coupling Agents for Improved Corrosion-Resistant Composites

Abstract The major progress in fiberglass-reinforced polyester composites since the 1940s has been attributed to the development of silane coupling agents that improve the bond across the interface [1]. Among the best coupling agents for polyesters is 3-methacryloxypropyltrimethoxysilane (γ-MPS), first described in 1962 (Fig. 1). Other methacrylate-functional silane coupling agents show comparable coupling activity in fiberglass reinforced general purpose polyester composites [2] (Table 1). The bond between glass and polyester with these coupling agents was “perfect,” i.e., fracture surfaces after 2-h water boil showed essentially no interfacial bond failure.

New Silicone Processing AIDS for the Extrusion of Linear Low Density Polyethylene

Various silicone process aid candidates were evaluated and compared to alternative process aids for their effect on surface properties of extruded linear low density polyethylene (LLDPE). Their performance was influenced by the silicone polymer structure and the concentration of the silicone polymer in the polyethylene resin. An increase in the polarity of functional groups on the silicone polymer resulted in an increase in the effect on surface properties of extruded LLDPE. Silicone concentrations in the range 220 to 3520 ppm in the polyethylene resin gave significant reduction in surface roughness caused by melt fracture during extrusion. Concentrations of 10000 ppm or less gave coefficient of friction values of 0.3 or below. Beneficial effects on extruder parameters, such as the reduction of extrusion pressure, current, and output were also observed.

Evaluation of Process Aids for Controlling Surface Roughness of Extruded LLDPE

Publisher Summary Surface irregularities are typically represented in terms of a degree of surface roughness. “Sharkskin” is characterized by the appearance of fine scale surface irregularities (transverse ridges similar to the design of a tire tread), about less than one-tenth the diameter of the extrudate, during steady pressure flow conditions. A number of techniques have been used for delaying or eliminating surface melt fracture. A number of techniques have been used for measuring the surface roughness of extrudates. These techniques have included observations with the naked eye and light microscopy, contact profilometry, fractal analysis, digital image analysis, fiber optic surface analyzer/pattern recognition, and atomic force microscopy. The more popular of these techniques is profilometry. In this chapter, a surface roughness analyzer is used to evaluate, offline, the surface roughness of samples produced from a single-screw extrusion tape line. Similar to a profilometer, a roughness average is used to quantify the extent of surface roughness. This analytical technique is used to compare the effectiveness of various silicone and commercial process aids in controlling the surface roughness of extruded thermoplastics. The measurement of average surface roughness of extruded tape at various extruder speeds differentiates the effectiveness of various process aids. Six commercial process aids and eleven new silicone process aid candidates are compared. A new silicone process aid is discovered which shows a significant reduction in surface roughness of both ethylene–octene and ethylene–hexene LLDPE copolymers. Beneficial effects on extruder parameters, such as reduction of pressure and current, are also observed.