New PP Clarifiers/Nucleators Challenge Industry Workhorse
Two additives based on new nucleator chemistry from Japan offer molders and thermoformers of polypropylene new tools for improving productivity. They also offer sparkling clarity in PP packaging. The supplier's data show performance exceeding that of the industry leaders, sorbitol-based Millad 3998, 3940, and 3905 from Milliken Chemical, Spartanburg, S.C.
Based on a complex organophosphate metal salt, ADK NA-11 and NA-21 are available from Amfine Chemical Corp., Allendale, N.J., the North American joint venture of Asahi Denka Kogyo K.K. and Mitsubishi Corp. The nucleating/clarifying additives are currently toll manufactured or imported from Japan. Next July, Amfine will start manufacturing them in Hopkinsville, Ky.
PP runs clearer, faster
NA-21 is being reviewed by the FDA for food-contact uses, whereas NA-11 is already approved for use at up to 0.3%. At just 0.1%, both products are said to improve PP properties such as flexural modulus, HDT, impact strength, and scratch or abrasion resistance. For example, 0.1% of NA-11 raises the flexural modulus of PP copolymer from 122,500 psi to 142,000 psi. The same loading of Millad 3998 reportedly yields a modulus of 134,000 psi.
At these loadings, NA-21 reportedly also provides high clarity, especially in thin-wall PP parts. As a clarifier, it outperforms both NA-11 and Millad 3988.
Commercial uses in Japan include thermoformed single-serve food packages and injection molded food-storage containers. Amfine general manager Peter Goman says this chemical class of nucleator/clarifier is also preferred in Japan for medical products and liquid packaging that need good extraction resistance.
NA-21 has also been used in large injection molded auto parts where its modest rate of crystallization leads to good dimensional stability. On the other hand, NA-11 induces faster crystallization at higher temperatures. For example, in PP homopolymer, Amfine reports a crystallization temperature of 275 F with NA-11, versus 270 F for NA-21 and about 252 F for Millad 3988. As a result, NA-11 looks best for reducing cycle times in injection molding and thermoforming.