Effect of b-Phase Nucleating Additives on Structure and Properties of Blow Extruded Polypropylene S. RADHAKRISHNAN, 1 M. TAPALE, 2 N. SHAH, 2 E. RAIRK AR, 2 V. SHIRODK AR, 2 H. P. NATU 2 1 Polymer Science and Engineering, National Chemical Laboratory, Pune 411008 2 Department of Polymer Engineering, Maharashtra Institute of Technology, Pune 411004, India Received June 27, 1996; accepted June 28, 1996 ABSTRACT: The structure development and mechanical properties of blow extruded polypropylene containing b-phase nucleating additives was studied. Quinacridone red and cadmium red were both found to nucleate the b phase in polypropylene, the former being a much more efficient nucleator than the latter. The b-phase spherulites formed in the presence of these nucleating agents were small and extensively volume filled, yielding high crystallinity. The modulus increased 2 – 3 times, elongation at break de- creased, and there was a sharp break point without much yield when the b-phase nucleating agents were added as compared to the pure a-phase polypropylene.  1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1247 – 1253, 1997 INTRODUCTION properties when changing the crystalline struc- ture, it was interesting to study the effect of b- phase nucleating additives on the structure devel- The enhancement of properties of commodity plastics by modification of structure, orientation, opment and properties of PP films. The results of these studies are described in the present article. and morphology has received considerable atten- tion in recent years. 1–4 In this context polypropyl- ene (PP) has been studied extensively and a cou- ple of new high crystallinity grades were intro- EXPERIMENTAL duced recently. 5,6 Many of the earlier studies reported isothermal crystallization of PP under To study the crystallization behavior of PP in the laboratory conditions, but very few are available presence of nucleating agents for the b phase, the on the structure development during extrusion PP (grade SM85N, IPCL, Baroda) was first pre- blow molding. Although, pigments and coloring cipitated in powder form by dropping its xylene agents are routinely added to the PP films, their solution into acetone and subsequently filtering effect on the crystalline structure has not been and drying the same in a vacuum (10 02 torr) for studied in detail. Some authors reported that pig- 24 h. This pure powder was then mixed with the ments such as quinacridone red (QR) can prefer- desired amount of nucleating additives. Two pig- entially nucleate the b phase in PP. 7,8 However, ments, QR ( CI 46500, Lona Industries, India ) and the effect of such additives on the properties of cadmium red ( CR, Hoechts, Colour Chem, India ) blow extruded PP films has not been reported be- were used as the nucleating agents of the b phase fore. In view of the large changes expected in the in PP. The additive and the polymer powder were thoroughly mixed in an agate pestle mortar until uniform coloration was obtained. The isothermal Correspondence to: S. Radhakrishnan.  1997 John Wiley & Sons, Inc. CCC 0021-8995/97 / 071247-07 crystallization of these compositions was studied 1247 3674 / 8E70$$3674 03-21-97 10:31:09 polaa W: Poly Applied