New modifiers & process aids for thermoplastics & thermosets.

Polyphenyl-based additives developed by Monsanto Europe in Brussels, Belgium, may soon find their way into applications in this country. Two new series of processing aids for filled polyolefins and new modifiers and nonreactive diluents for polyurethane foams and epoxy resins were first discussed last fall at the K'92 Fair in Dusseldorf, Germany. Monsanto Chemical Co., St. Louis, now is considering whether to introduce these products in North America later this year.

The processing aids--one series for glass-reinforced polypropylene and the other for mineral-filled polyolefins--reportedly improve melt flow, surface appearance and thermal/hydrolytic stability. All go under the trade name, "Flexaryl SPE." The polyurethane and epoxy diluents and modifiers, which are also part of the Flexaryl family, are based on similar chemistry. They are extensions of a line that includes at least one product marketed here for 15 years as a secondary plasticizer and extender for sealants. Known as Flexaryl 9020 in Europe, the additive is sold in North America under the name HB40.

FLOW AIDS FOR FILLED OLEFINS

Mineral fillers in PP and ethylene-propylene copolymers enhance the materials, chemical resistance and resistance to stress cracking, as well as raise stiffness and boost end-use temperatures. However, when PP is subjected to temperatures below the freezing point, mineral fillers tend to make the material brittle. Mineral fillers also sacrifice tensile elongation, impact strength, and flowability. Similar limitations occur in glass-filled polyolefins.

According to Monsanto, the addition of partly hydrogenated polyphenyls, particularly in large and complex parts, can help overcome these liabilities. Included in Monsanto's European list of polyphenyl processing aids are SPE 9022, 9024 and 9025, liquid mixtures of partly hydrogenated polyphenyls. They differ only in their viscosities. SPE 9026 and 9027 are solid polyphenyl waxes; 9027 has a broader melting range.

In mineral-filled PP and EP copolymers, Monsanto says 2-3 phr of SPE 9024 improves processability by increasing the melt flow index. In molded samples, the elongation and notched Izod impact strength also improve. The company says use of this additive should allow a formulator to increase the rigidity of parts by raising the filler level with little increase in melt viscosity.

In tests at Owens-Corning's Technical Center in Battice, Belgium, addition of 3% of partly hydrogenated polyphenyls to 30% glass-reinforced PP (modified with an acrylic binder that improves adhesion between the glass and matrix) produced an increase in the system's flowability. This, in turn, resulted in improved surface appearance and gloss. Increases similar to those for the mineral-filled compounds were also seen in impact strength.

When the acrylic binder was removed from the glass-reinforced formulation, tensile strength and modulus remained about the same. The processing aid's adhesion qualities were evidently as good as the acrylic binder and hydrolysis resistance increased, causing Monsanto to speculate that the polyphenyls could be potential substitutes for acrylics in some applications. (CIRCLE 56)

URETHANES AND EPOXIES

The basis for Monsanto's new range of functional modifiers and diluents for thermosets is a polyphenyl chemistry similar to that of the polyolefin process aids. The two products in the new line are Flexaryl 9022 and Flexaryl 9024. Both are based on partially hydrogenated, high-molecular-weight polyphenyls, providing low viscosity, low volatility and minimal moisture content without affecting the matrix polymer's curing properties. They are aimed primarily at construction coatings and glazing sealants. How ever, the combination of chemical stability, nonreactivity and good dielectric properties provided by these modifiers also position them for formulating epoxy compounds for potting and encapsulation of electrical and electronic components.

In a permeability test where a polyurethane glazing and construction sealant was subjected to moisture for 32 days, a PUR modified with hydrogenated polyphenyl attracted about 55% less water than a sealant modified with aromatic sulfonate ester and 12% less than one containing undecyl dodecyl phthalate.

Because they are nonreactive with MDI and TDI, hydrogenated polyphenyls can be added directly to the hardener portion of a two-component PUR system, Monsanto says, improving the ratio balance between hardener and prepolymer. (CIRCLE 57)