Polypropylene Metallocene

The application of metallocene catalysis to the preparation of polypropylenes reached a commercial stage with the production by Exxon of their Achieve range in 1996 and in 1997 by Targor, the BASF-Hoechst joint venture with the introduction of Metocene. Such metallocene polypropylenes are, however, only a small proportion of the total polypropylene market, predicted at only about 3% of the total in 2005. 

Ewen, J.A. Elder, M.J. Jones, R.L. Haspeslagh, L. Atwood, J.L. Bott, S.G. Robinson, K. Metallocene/polypropylene structural relationships implications on polymerization and stereochemical control mechanisms. Macromol. Symp. 1991, 48, 253. 

Ghaffin, K. A., J. S. Knutsen, P. Brant, and P. S. Bates. 2000. High-strength welds in metallocene polypropylene/polyethylene laminates. Science 288 2187-2190. 

The effect of stereochemistry and polydispersity on nanocomposite properties has yet to be explored fully. An intriguing result was obtained by Quijada et al. who performed melf mixing of PP-g-MA with octadecylamine-modified montmorillonite or hectorite, then blended these materials with different isotactic polypropylenes. Nanocomposites with better clay exfoliation were obtained using metallocene polypropylene compared to Ziegler-Natta polypropylene, presumably because of ifs lower polydispersity. While stereoselective metallocene catalysts have been used successfully for in situ propylene polymerization in combination with clay supports (see Section 5.2.2.2), the materials properties of these nanocomposites have thus far received insufficienf affention. 

Blends comprised 1-70 wt% of either metallocene polypropylene, PP, or a copolymer of propylene with <10 mol% ethylene or C2-C20 a-olefin that has MJMa < 3 and 30-99 wt% of a similar copolymer but with MJMn = 3.5-10. The blends were used for films having excellent low-temperature heat sealability and blocking resistance... 

Gomez-Elvira and co-workers [77], Schmidt-Rohr and Speiss [78] used DMTA to measure the Tg and a-relaxation of a metallocene polypropylene sample and an isotactic polypropylene sample, respectively. 

Figure 4 Calculated peak broadening in SEC of a metallocene polypropylene...

The microwave susceptors in this initial study have been carbon black, magnetite, lead zirconate titanate, and silicon carbide. The polymeric matrix for these trials has been mainly high density polyethylene, which is a nonpolar polymer without any absorption of microwave radiation. Other thermoplastic matrixes like polyamide 6 (PA6), polybutylene terephthalate (PBT) and metallocene polypropylene (m-PP) have been used as reference material. 

The newly developed foamed metallocene polypropylene (FMP) products are very flexible, processable, dimensionally stable, and heat resistant. Due to inherent chemical resistance, moisture barrier and insulating properties, FMP products offer alternatives to their more expensive polyurethane foam counterparts. 

The foamed metallocene polypropylene (FMP) has been developed by Sentinal Products Corporation in collaboration with Ferro. FMP products have advantages over competitive materials such as polyurethane foam, integral skin PVC foam and non-metallocene-based polyolefin foams. Due to the moisture barrier character, foamed metallocene polypropylene (FMP) offer alternatives to more expensive polyurethane foams in the medical packaging arena. 

Fig. 2.28 provides an explanation for the lower melting point of metallocene polypropylene in comparison to Z-N polypropylene. The melting point of metallocene polypropylene is in the range of 150°C... 

Materials. Nanocomposites from metallocene polypropylene (HM562S, Lyondell-Basell) and nanoclay (hydrophilic montmorillonite, MMT) are studied. The MMT is obtained from Laviosa Chimica Mineraria, Italy (3.8 wt.-% aq. dispersion of montmorillonite). A compatibilizer is added to two of the materials in order to intercalate the MMT. The compatibilizer is an amphiphilic block copolymer (ABC) made by atom-transfer radical polymerization (ATRP) [3, 4]. It consists of a hydrophobic block of hydrogenated polybutadiene, i.e. poly(ethylene-co-1,2-butylene) monoalcohol (trade name Kraton L-1203 from Kuraray Co., Japan) with molecular weight 7000 and PDI = 1.05, and a hydrophilic block of quaternized dimethylaminoethyl methacrylate. Modified nanoclays with 4.7 and 8.0wt.-% of the ABC have been prepared. Table2.1 describes the composition of the studied materials. Sample PP is the pure polypropylene. Sample PP+MMT is a blend of polypropylene and the freeze-dried hydrophilic MMT. The samples PP+lcMMT and PP+hcMMT are composites that contain MMT with low compatibilizer amounts and high compatibilizer amounts, respectively. In order to prepare the nanocomposites, modified IcMMT and hcMMT have first been freeze-dried and, second, blended" with the PP. 

Table 2.1 PP/MMT Nanocomposites based on metallocene polypropylene (PP)—HM562S (Lyon-deUBaseU) and montmoriUonite (MMT) (Laviosa) ...

Nevertheless, although the mechanical properties of the 4 materials are very similar, monitoring of the straining experiments by SAXS has shown that the semicrystalline nanostructure and its evolution vary considerably. The relative variations from material to material indicate that the dominant troublesome effect of blending MMT and the studied metallocene polypropylene grade is not the interfacial incompatibility between filler and matrix, but the alteration of the adjusted nanostructure of the matrix grade by the filler. 

The goal of this work was to evalnate the rotomoldability of the metallocene polypropylenes selected from the newly developed wax family of Licocene Performance Polymers. ... 

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