PE-PP blends

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. 

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.)... 

PE/PP blends have also been studied in terms of stability to oxidation. Livanova shown that oxidative degradation reaches a maximum when PP is in an isotropic structure and minimum for an oriented one [90]. 

The peeling strength of PE-PP blends is increased by welding its sheet ultrasonically [213]. Rizzo et al. [214] have irradiated IdPE-i-PP blends with 125 Mrad and have studied structural modifications. For blends containing small amounts of one component, the decrease of crystallinity on increasing y-irradiation... 

Heat-resistant [218] soft foams were prepared from the blends of hdPE with E-P random copolymers. The azodicarbanamide acts as a thermal antioxidant and the crosslinking of the blend was increased by electron beam radiations and foamed at 225 °C with 2320% expansion. A blend of 35 wt.% PE-PP (8 92), 15 wt.% E-P block copolymers, and 50 wt.% EPDM showed accelerated weathering resitance [219] 1000 h probably due to crosslinking between constituents of the block copolymer, polyblend and EPDM. The effect of filler and thermodynamic compatibility on kaolin-filled PE-PP blend was studied by Lipatov and coworkers [220]. The thermodynamic interaction parameter (%) decreased and thermodynamic stability increased by filler addition, the degree of crystallinity decreased with increasing thermodynamic compatibility of the components due to sharp decrease in the phase separation rate during cooling. 

The adverse environments experienced during high temperature processing are exemplified by studies on PS blends with PIB [La Mantia and NociUa, 1987] and with PE [Komova et al., 1991 1992], of PE/PP blends [La Mantia et al., 1985], and of poly(hydroxy acids) blends with poly(hydroxybutyrates) [Gogolewski et al.,... 

There have been extensive applications of isotactic polypropylene (iPP)/EPM blends. These were used to produce rubber toughened polypropylene blends and subsequently polyolefin thermoplastic elastomers (88,89). Most commercial EPMs contain more than 50 mol% of ethylene, and these are elastomers. The solubility parameter of EPM should be intermediate to those of polyethylene and polypropylene dependent on ethylene content. Thus, it is often used to compatibilize PE/PP blends (90,91). 

Irrespective of DCP and MAH ratio in a reacting system, grafting efficiency of PE/PP blends exceeds that of neat PE. According to Chaoqin Li et al. (44), this can be explained by a lower viscosity of PE/PP melt against neat PE, which makes diffusion of reagents easier and raises the homogeneity of the reacting system. 

On the basis of the IR spectral analysis of the grafted products, Chaoqin Li et al. (44) have concluded that in the PP/PE melt, MAH gets grafted to chains of both PE and PP. This conclusion is based on the fact that the values of characteristic band frequencies of carbonyl absorption of MAH grafted to PE/PP blends (1864.1 and 1785.6 cm ) are between frequency values for MAH grafted to PE (1865.2 and 1784.9 cm ) and to PP( 1862.5 and 1785.8 cm ). However, if Chaoqin Li etal. (44) had separated the (PEZPP)-g-MAH blend into separate PE and PP fractions by some known methods used in polymer blend fractionation (e.g., temperature rising elution fractionation, TREF, or some others), then determination of grafting location by IR spectral analysis would have been much more certain and precise. 

Triple SMPs have one permanent shape and two temporary shapes, compared to the traditional double shape memory polymers (SMPs) that have only one permanent and one temporary shape. Triple SMPs can therefore provide more complex actuation than double SMPs. While double SMPs only need one reversible phase, triple SMPs generally need two reversible phases. Zhao et al. [13] first built a co-continuous architecture in immiscible polyethylene (PE)/polypropylene (PP) blends, and then prepared triple SMPs through chemical crosslinking of the blends. The co-continuous window of typical immiscible PE/PP blends is a volume fraction of PE of approximately 30-70 vol.%. This architecture can be stabilized by chemical crosslinking. Different initiators, 2,5-dimethyl-2,5-di(tert-butylperoxy)-hexane (DHBP), dicumylperoxide (DCP) coupled with divinylbenzene (DVB) (DCP-DVB), and their... 

Prydilova O. Petronyuk U. Tertyshnaya U. Ledneva O. Popov A. The correlation of structure and properties of PE-PP blends. Chemistry and computer modeling. 2002, ll, 103-106. 

Most PE/PP blends show a two-phase structure that may be detrimental to blend performance at large strains. Blending enhances the crystallinity and reduces the spherulite size, which may improve performance especially at small deformations, viz. increased modulus, where the effect of immisdbility is small. However, at large strains poor adhesion between the two phases results in a low value of the stress and... 

Interfacially active graft or block copolymers of the t5 pe A-B or A-C may compatibilize the immiscible polymers A and B provided that C is also miscible or capable of strong interactions with B. Poly(ethylene-co-propylene) elastomer (EPR) or poly(ethylene-co-propylene-co-diene) (EPDM) is an example of such nonreactive compatibilizer for polyethylene/polypropylene (PE/PP) blends. 

Figure 4.54 DSC curve for a PE-PP blend [75J. The known amount of PE in the blend is 14.0%...

Reactive compatibilization of polymers through copol5uner formation is also possible with the help of low molecular weight compounds (56), eg by combination of a peroxide with an oligomer coagent for preparation of PE/PP blends (57) or bis-maleic imide for PE/PBT (58). Special cases of reactive compatibilization can be considered radical-initiated reactions of monomers forming homopolymers and grafts on the chains of dissolved polymers. This process is nsed for manufacture of such important polymers as HIPS or ABS (59). 

Microporous polymer membranes are the most commonly used separators in lithium-ion batteries. Majority of the microporous polymer membrane separators are based on semicrystalline polyolefin materials, such as polyethylene (PE), polypropylene (PP), PE-PP blends and high-density polyethylene (HDPE)-ultrahigh molecular polyethylene (UHMWPE). 

Collision crushing PE-PP blend Thin film formers 63... 

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