Process Oils

Shellflex oils have a variety of applications in polymer compounding. As extenders, they reduce content and compound cost without comprising performance. As plasticizers, they save energy by reducing the mix work. They also reduce production time by facilitating extrusion, calendering and blow molding. Finally, as modifiers, process oils promote surface smoothness of extrudates, assist controlled variation of TPE stiffness and improve both tensile strength and resistance to cold cracking. Depending on the compound, a good process oil can also serve as a catalyst carrier.

Paraffinic oils are highly stable process oils with excellent color stability and high flash points. They boast good high temperature properties and are commonly used in saturated polymers. These oils are less solvent than naphthenic oils, so they are less readily incorporated into certain compounds.

Naphthenic oils are high solvency, nonstaining oils with good stability and light color. These oils have lower flash points than paraffinic oils, but still exhibit good high temperature properties. They have low pour points and are generally easier to handle at lower ambient temperatures.

Properties
Aromatic Content: The higher an oil's aromatic content, the more of that oil a compound can take before bleed-out. Higher aromatic normally mix faster, also, which can translate into quicker batch production. Of course, lower aromatics have advantages, too- greater color stability, for one. Before basing an oil purchase on any aromatic benefit, consider the chemical structure of the base polymer to better appreciate its aromatic capabilities. The company measures aromatic levels with both the industry standard clay-gel absorption test and with their own UV total aromatics test. The UV method is more repeatable, and measures aromatic levels in mmols/100 grams rather than wt/% as the clay-gel does. This helps better differentiate among aromatic species, and therefore better determine the performance of an oil in a compound.

Aniline Cloud Point (ACP): This is an industry measure of oil solvency in compounds like plastic. The ACP test measures the temperature at which a 50/50 mix of oil and aniline becomes homogeneous. Generally speaking, aromatics have lower ACP values than naphthenics, which in turn have lower values than paraffinics. The company works constantly to better the solvency of aromatics with the need to achieve stability and avoid producing oils considered carcinogenic.

Volatility: The lower an oil's volatility, the higher its viscosity and flash point. Many applications require good high temperature performance, such as weight loss on heat aging, so low volatility becomes an important factor in oil choice.

Applications
Adhesives: Whether hot melt, pressure sensitive, aqueous or two-component, all adhesives must be sufficiently liquid during application to effectively cover the surface to be bonded. Process oils are excellent for enhancing a plastic's wetting characteristics, broadening the range of accessible substrates and forming a more versatile adhesive. As most adhesives are thermoplastic, manufacturers prefer naphthenic oils for their higher viscosities and greater compatibility with adhesives' low open time.

Sealants and Mastics: Widely used in construction and the automotive industry, these plastic compounds form weatherproof barriers that accommodate differential movement of structural parts. Sealants can b rubber-, TPE- or asphalt-based, and generally use process oils as a blending agent. Mastics and putties contain higher oil loadings, and generally employ process oils as extenders. Paraffinic and naphthenic oils are equally used here; chemical compatibility with the load-bearing polymer will largely determine which is best for a specific application.

Shell Oil Products Company, P.O. Box 4320, Houston, TX 77210. Tel: 713-241-2521. Fax: 713-241-3325.