Reactive stabilizer shields nylon from heat & light.

A new multifunctional stabilizer is said to be compatible with all types of nylons because it bonds chemically to the polymer. Nylostab SEED is a developmental product from Clariant Corp., Charlotte, N.C. It's an aromatic hindered-amine light stabilizer (HALS) that also imparts both thermal and thermo-oxidative stability to nylon polymers and fibers and their colorants, according to technical service manager Joseph Webster.

Chemical structure of S-EED consists of two tetramethyl piperidine HALS groups chemically bound to an aromatic ring. S-EED forms hydrogen bonds with the nylon chain, resulting in better compatibility, higher tensile strength, and excellent resistance to extraction and washing, says Webster.

AT HOME IN NYLON MELTS

Common stabilizers such as phenolic antioxidants and oligomeric HALS are typically nonpolar, hydrophobic substances designed primarily for compatibility with polyolefins, explains Webster. But nylons require additives that are more polar or hydrophilic, more heat stable, and resistant to the reductive environment of nylon melts, which is hostile to many colorants and additives.

Nylostab S-EED is a white, free-flowing powder with a melting point of 522 F. It is highly soluble in melts of nylon 6 and other nylons at use levels of 0.5% to 1%. It reportedly has higher heat stability and lower volatility than traditional HALS, even at high processing temperatures. In dynamic thermogravimetric analysis, S-EED shows 10% weight loss at 671 F, compared with 10% weight loss at 536 F for standard HALS.

STRONGER COLOR HOLD

In molding studies, S-EED improved clarity and refractive index, resulting in less yellowing and increased gloss in filled, pigmented, and neat nylon.

The graph above shows the yellowness index of injection molded nylon 6 plaques containing different stabilizers. They were traditional hydroxy-substituted uv stabilizers for nylon - a benzophenone and two benzotriazoles - as well as a newer oxanilide alternative, Clariant's Sanduvor VSU. Yellowness is greater with Cyasorb UV531 from Cytec Industries and with Tinuvin 327 and 234 from Ciba Additives. Less yellowing results with Sanduvor VSU and Nylostab S-EED.

The product will hit the market once it receives EPA ToSCA registration. Webster says it will be priced competitively with standard HALS.