PP blends

Polypropylene. PP is a versatile polymer, use of which continues to grow rapidly because of its excellent performance characteristics and improvements in its production economics, eg, through new high efficiency catalysts for gas-phase processes. New PP-blend formulations exhibit improved toughness, particularly at low temperatures. PP has been blended mechanically with various elastomers from a time early in its commercialisation to reduce low temperature brittleness. 

Figure 6 Tensile strength versus percent polypropylene in SBR ionomer/PP blends.

Figure 3 tan5 versus temperature plot for NR-PP blends (50 50) curve 1, purePP curve 2, dynamically cured blend curve 3, conventionally cured blend. Source Ref. 19. 

Elliot [38] has reported that interfacial adhesion in the NR-PP blend can be enhanced by the addition of small amounts of HOPE. Addition of HDPE does give some improvement in the notched Izod impact strength of NR-PP blend (Fig. 7). The effect of HDPE on the impact modification of NR-PP is associated with the improved crystallinity of PP, enhanced by HDPE. During the mill mixing of NR and PP, chain scission may occur to give polymeric radicals that, on reaction with... 

Figure 7 Effect of addition of HOPE on Izod impact strength of NR-PP blend. (O) 20 80 NR-PP homopolymer, (V) 20 67 13 NR-PP-homopolymer-HDPE, ( ) 15 85 NR-PP copolymer grade, and (x) 15 75 10 NR-PP-copo-lymer-HDPE.

Improvement in the compatibility of NBR-PP blends by various compatibilizers was reported by Rader and Sabet [40]. The effect of different compatibilizers on the properties of NBR-PP blends is given in Table 13. 

Recently, Nitto Denko has patented a single-layer separator made from a PE/PP blend by the dry stretch process [24], According to the patent, the separator has microporous regions of PE and PP. On heating in an oven, the impedance of the separator increases near the melting point of PE and the impedance remains high until beyond the melting point of PP. However, battery performance data have not been presented. 

A study on the effectiveness of the E-plastomers as impact modifiers for iPP was carried out in relation to the traditional modifier EPDM. In this study, the flow properties of the E-plastomer-iPP and EPDM-PP blends were also evaluated. The blends were analyzed by solid-state 13C-nuclear magnetic resonance (NMR) spectroscopy, microscopy (SEM), and DSC. The results showed that E-plastomer-PP and EPDM-PP blends present a similar crystallization behavior, which resulted in a similar mechanical performance of the blends. However, the E-plastomer-PP blend presents lower torque values than the EPDM-PP blend, which indicates a better processibility when E-plastomer is used as an impact modifier for iPP. 

As expected, the EDS data set indicates that the polymeric matrix material (the PE-PP blend) is composed only of carbon (hydrogen is not detectable by this method). The particle, however, appears to be composed mainly of aluminum and oxygen along with small amounts of copper. The ratio of aluminum to oxygen is consistent with the chemical formula for aluminum oxide (A1203). The SEM-EDS results are consistent with aluminum oxide and traces of copper as the primary constituents of the particulate contamination. (Al2O3.3H20 is a commonly used fire-retardant additive in polymeric products.)... 

FOAMED CROSSLINKED LDPE/PP BLENDS MADE BY HOT MOLD INJECTION MOLDING... 

Details are given of the mechanical properties and melting/crystallisation behaviour of foamed and crosslinked LDPE/PP blends made by hot mould injection moulding. The chemical changes as a result of the... 

Dallas, Texas, 6th-10th May, 2001, paper 400 EXTRUSION FOAMING OF PET/PP BLENDS Wan C Xanthos M Dey S Zhang Q New Jersey,Institute of Technology (SPE)... 

A study on the batch processing and characterisation of microcellular foamed HDPE/isotactic PP blends is reported. The blends were used to produce materials with a variety of crystaUine and phase morphologies to enhance the subsequent microcellular foaming. Much finer and more uniform foams were produced with the blends than with neat HDPE and isotactic PP. The mechanical... 

Thermoformable foamed PP sheet that processes with the same drawdown, sag and cycle times as PS has been manufactured by Omam using new PP blends and Safoam carbon dioxide blowing agents from Reedy International. Oman has already produced monolayer PP sheet with a 40% density reduction and three layer sheet with a 50% density reduction. The trials have been carried out using blends of conventional PP and a new high melt strength PP grade developed by Montell. The Omam line used to produce the foamed PP sheet is conventional apart from... 

Flexothene poly(alpha-olefms) PP blend with EPDM or EPR Quistar... 

The structure of crystalline polymers may be significantly modified by the introduction of fillers. All aspects of the structure change on filling, crystallite and spherulite size, as well as crystallinity, are altered as an effect of nucleation [9]. A typical example is the extremely strong nucleation effect of talc in polypropylene [10,11], which is demonstrated also in Fig. 2. Nucleating effect is characterized by the peak temperature of crystallization, which increases significantly on the addition of the filler. Elastomer modified PP blends are shown as a comparison crystallization temperature decreases in this case. Talc also nucleates polyamides. Increasing crystallization temperature leads to an increase in lamella thickness and crystallinity, while the size of the spherulites decreases on... 

Reichelt N, Stadlbauer M, Folland R, Park CB, Wang J (2003) PP-blends with tailored foam-ability and mechanical properties. Cell Polym 22 315-327... 

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