Blends between Polyethylenes

Blends between iPP and High Comonomer Concentration Polyethylene Copolymers... 

Microscopically Viewed Structural Characteristics of Polyethylene Blends Between Deuterated and Hydrogenated Species Cocrystallization and Phase Separation... 

Blends of polyethylene terephthalate and linear low-density polyethylene were compatibilised using diethylmaleate grafted polyethylene, and characterised using Fourier transform infra-red spectroscopy, thermogravimetric analysis and scanning electron microscopy. Interactions between the components in the blends were observed, which affected the glycol sequences of the polyester and also improved the thermal oxidative stability of the blends. The introduction of the compatibiliser resulted in a particle size reduction of the dispersed phase and better adhesion between the phase and the matrix. 15 refs. 

Figure 13.11 illustrates the change in torsional stiffness that can occur as the temperature drops and compares polyurethane with other rubbers. There is only a small increase in the torsional stiffness as the temperature is decreased from -2(fC to about — 25" C, but then the increase in stiffness occurs very rapidly. The second-order transition point is between — 30 and —40°C and it is dependent upon the regularity of the molecular structure. Lower transition temperatures can be obtained by the use of mixed glycol polyadipates in place of the common polyethylene glycol adipate. For example, it is common commercial practice to use a blend of polyethylene... 

The lack of synchronous cross peaks between polystyrene and polyethylene bands indicates these polymers are reorienting independently of each other. Cross peaks appearing in the asynchronous spectrum (Figure 1-19) also verify the above conclusion. For an immiscible blend of polyethylene and polystyrene, where molecular-level interactions between the phase-separated components are absent, the time-dependent behavior of IR intensity fluctuations of one component of the sample... 

The blends of thermoplastics with LC polymers exhibit inferior properties due to lack of adequate compatibility between the two phases. However, application of common method of compatibiliza-tion, i.e., adding a third component in the form of a copolymer, having monomer unit of the two polymers, the properties of the blend can be enhanced. Thus, blends of Polyethylene (PE) with LCP can be compatibilized by adding PE-g-LC copolymers. The PE-g-LC copolymers can be produced by either of the two methods, i.e. melt polycondensation of LC monomers in the presence of a PE containing free carboxyl group and by reactive blending of the two. The blends can be prepared in an extruder fitted with internal mixer at high temperature ( 250°C). The mixture of PE and LC polymer... 

Recycled plastic railroad ties have very large scale potential. A number of test projects with a few ties each were carried out between 1996 and 1997. In 1998, the Chicago Transit Authority became the first commercial purchaser, buying 250 ties for a test on its elevated train line. U.S. Plastic Lumber has been one of the major prodncers of these materials, and it claims that they have twice the fife span of wood ties. Polywood produces RPL for railroad ties as well as for bridges and boardwalks from a blend of polyethylene and poly-... 

Polyolefin materials used for the battery separator are based on a homopolymer or a blend of polyethylene (PE) and polypropylene (PP) in a number of combinations between high density polyethylene (HOPE) and ultrahigh molecular weight polyethylene (UHMWPE). The methods for manufacturing the microporous polyolefin membranes can be divided into the dry process and wet process. Both processes contain an extmsion step to produce a thin film, and employ one or more orientation steps to impart porosity and increase tensile strength. The membranes made by diy process show a distinct slit-pore microstmcmre, while those by wet process feamre interconnected spherical or elliptical pores. 

Note that both the interaction energy, and the interaction parameter, x, are proportional to the size of the system, or V,. For example, for blends with polyethylene, Vr can be adopted as the molar volume of one methylene unit or as the molar volume of one dimethylene unit. Doubling implies doubling BVr and x-To allow comparisons in the strength of the interactions between different systems, some authors prefer to work with an arbitrarily chosen constant value for V instead of changing its value from one system to another [llj. 

We have previously discussed recycled polymer blends in Section 5.11 and 6.7. We noted that binary (or indeed ternary) blends involving polyethylene, polystyrene, polyvinyl chloride, polyamides, etc., have poor mechanical properties because of a lack of adhesion between the components (Section 5.11). We indicated in Section 6.7 that introducing compatibiHzing agents such as styrene-hydrogenated butadiene-styrene triblock copolymer and maleated polyolefins can enhance the mechanical properties. However, this in itself is not enough. 

Rajasekharan and co-workers have investigated united atom and atomistic models of blends of polyethylene with vinyl polymers. They have provided a simple explanation of why isotactic polypropylene and polyethylene are immiscible even though their monomers are so similar. The immiscibility arises from the difference in packing between the branched and linear chains. In a melt the polyethylene molecules prefer to minimize their energy by packing amongst each other rather than packing less efficiently in the blend. 

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