Polyolefin-polystyrene blends

Polyolefin-polystyrene blends have long been studied. They are immiscible showing two-phase morphologies. The blends showed poor mechanical properties, especially elongation at break and impact strength, much lower than those predicted based on an additive rule (118). Their fracture surfaces were observed by electron microscope (119,120). As shown in Fig. 2.8, the dispersed phase is easy to be pulled from the matrix and leaves very smooth surface, indicating low interfacial adhesion. 

Because of the high interfacial tension, the morphology of the blends is not stable. Coalescence readily occurs in the molten state. As suggested by Macosko et al. (121), in melt mixing of immiscible polymer blends, the disperse phase is first stretched into threads and then breaks into droplets, which can coalesce together into larger droplets. The balance of these processes determines the final dispersed particle sizes. With increase of disperse phase fraction (usually more than 5 wt%), the coalescence speed increases and the dispersed phase sizes increase (121-123). 

Polyolefin-polyamide melt blends are striking in not only the lack of miscibility, but also the large interfacial tensions between the two melt phases. Investigations of these phenomena in our laboratories (118,124-126) have made numerous studies of these polymer blend systems and found that their phase morphology are quite unstable and trend to coalesce especially under quiescent or low deformation rate conditions. Similar to polyolefin-polystyrene blends, they also show weak interfacial adhesion (118,124,127) (as shown in Fig. 2.9). The mechanical properties of the 

6 TERNARY BLENDS OF POLYOLEFINS WITH OTHER POLYMERS AND COMPATIBILIZING AGENTS 

Soap is the earliest surfactant. The earliest soap was made by boiling fats together with ashes of plant, which dated as early as 2800 B.C. in ancient Babylon. In 1823, Michel Eugene Chevreul, a French chemist, worked out the structure of fats 

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Polyolefin-Polystyrene Blends with Compatibilizing Agents... 

The examples given above are, however, exceptions. In general, polymer blends are immiscible. Immiscible polymer blends usually exhibit ultimate mechanical properties such as elongation at break inferior to either of the pure components. This is notably the case in polyolefin-polystyrene blends. Another example of this inferiority of ultimate properties is found in studies of the tensile test energy to break in blends of polyethylene and polyamides [89]. 

Polycarbonate-polystyrene blend along with poly(alkylene-dicarboxylate) such as SMA SEBS copolymer for toughening blends of PPO with nylon and polyolefin (proprietary compatibilizer)... 

Limited compatibility to standard polymers. Ecoflex is incompatible to standard polymers like polyolefins, polystyrene and polyvinylchloride (PVC), forming large domains in blends with standard polymers. 

Guo, Z., Fang, Z., and Tong, L. 2007. Application of percolation model on the brittle to ductile transition for polystyrene and polyolefin elastomer blends. eXPRESS Polymer Letters 1 37-43. http //www. expresspolymlett.com/... 

To improve the properties of PLA, plasticizers, special additives such as chain-extenders, polymer blends, and composites are commonly investigated. Martin and Averous (10) have studied the effects of various plasticizers on the properties of PLA. Pilla et al. (11-12) have investigated the effects of chain-extenders on the foaming properties of PLA. In addition, a vast number of studies have been conducted to enhance the properties of PLA by blending it with various polymers such as polyethylene oxide (PEO), polypropylene oxide (PPO), polyvinyl acetate, polyolefins, polystyrene, HIPS (high impact polystyrene), polyacetals, polycarbonate, and acrylonitrile butadiene styrene (ABS) (13-26). 

Polyolefin + Polystyrene or Styrene Copolymer Binary Blends... 

Polyolefin-nylon blends Polypropylene, polystyrene Japan 38,836 1971 Mitsubishi Rayon... 

The vector fluid concept was first suggested for a polyethylene (PE)/polyamide (PA) reactive blending system [12], as mentioned earlier in this chapter. This concept is interesting because it has the potential to provide a compatibilization method for polymers that have no chemical functionalities suitable for copolymer formation during melt blending (e.g. the case of polyolefin and polystyrene). It has been seen that the blends of polyolefin/polystyrene are difficult to compatibilize in situ by simply adding a free radical initiator into the blending process. Usually, flie pre-made block or reactive polymers or copolymers, which can be expensive, are needed for polyolefin/polystyrene compatibilization [15-17]. If a suitable vector fluid can be found for the polyolefin/ polystyrene/peroxide in situ compatibilization, the process could become more controllable and more cost efficient. 

Binary req cled polymer blends, such as recycled polyolefin-polystyrene or polyolefin-polyamides, have poor mechanical properties. It is found in these cases that to introduce styrene-hydrogenated butadiene-styrene block copolymer or maleated polyolefins, respectively, as compatibilizing agents has great benefits. These both produce finer morphologies and enhanced mechanical properties. Other additives [55 to 69] should also be included into recycled polymer blends. We describe this in detail in Section 8.4.3. 

The brittleness of isotactic polystyrenes has hindered their commercial development. Quoted Izod impact strengths are only 20% that of conventional amorphous polymer. Impact strength double that of the amorphous material has, however, been claimed when isotactic polymer is blended with a synthetic rubber or a polyolefin. 

These results demonstrate some interesting chemical principles of the use of acrylic adhesives. They stick to a broad range of substrates, with some notable exceptions. One of these is galvanized steel, a chemically active substrate which can interact with the adhesive and inhibit cure. Another is Noryl , a blend of polystyrene and polyphenylene oxide. It contains phenol groups that are known polymerization inhibitors. Highly non-polar substrates such as polyolefins and silicones are difficult to bond with any technology, but as we shall see, the initiator can play a big role in acrylic adhesion to polyolefins. 

Substitute for Conventional Vulcanized Rubbers, For this application, the products are processed by techniques and equipment developed for conventional thermoplastics, ie, injection molding, extrusion, etc. The S—B—S and S—EB—S polymers are preferred (small amounts of S—EP—S are also used). To obtain a satisfactory balance of properties, they must be compounded with oils, fillers, or other polymers compounding reduces costs. Compounding ingredients and their effects on properties are given in Table 8. Oils with high aromatic content should be avoided because they plasticize the polystyrene domains. Polystyrene is often used as an ingredient in S—B—S-based compounds it makes the products harder and improves their processibility. In S—EB—S-based compounds, crystalline polyolefins such as polypropylene and polyethylene are preferred. Some work has been reported on blends of liquid polysiloxanes with S—EB—S block copolymers. The products are primarily intended for medical and pharmaceutical-type applications and hardnesses as low as 5 on the Shore A scale have been reported (53). 

Although solution blending has only been used at the lab scale at this time, compared with the in situ process, it may be more industrially friendly, particularly for the primary polymer producers who have operations, which can easily recover and recycle the solvent. High dilution is required and this may have an effect on the production of the PNs and the process is quite dependent on the individual polymer. Some polymers have many solvents from which to choose while others do not. A typical example is polystyrene, which can dissolve in a variety of solvents, so it is easy to find a solvent that is compatible with both the clay and the polymer. Polyolefins, on the other hand, require high boiling solvents and the high temperature may exert an effect of thermal degradation on the modifier. 

PVC can be blended with numerous other polymers to give it better processability and impact resistance. For the manufacture of food contact materials the following polymerizates and/or polymer mixtures from polymers manufactured from the above mentioned starting materials can be used Chlorinated polyolefins blends of styrene and graft copolymers and mixtures of polystyrene with polymerisate blends butadiene-acrylonitrile-copolymer blends (hard rubber) blends of ethylene and propylene, butylene, vinyl ester, and unsaturated aliphatic acids as well as salts and esters plasticizerfrec blends of methacrylic acid esters and acrylic acid esters with monofunctional saturated alcohols (Ci-C18) as well as blends of the esters of methacrylic acid butadiene and styrene as well as polymer blends of acrylic acid butyl ester and vinylpyrrolidone polyurethane manufactured from 1,6-hexamethylene diisocyanate, 1.4-butandiol and aliphatic polyesters from adipic acid and glycols. 

Polystyrene is one of the most widely used thermoplastic materials ranking behind polyolefins and PVC. Owing to their special property profile, styrene polymers are placed between commodity and speciality polymers. Since its commercial introduction in the 1930s until the present day, polystyrene has been subjected to numerous improvements. The main development directions were aimed at copolymerization of styrene with polar comonomers such as acrylonitrile, (meth)acrylates or maleic anhydride, at impact modification with different rubbers or styrene-butadiene block copolymers and at blending with other polymers such as polyphenylene ether (PPE) or polyolefins. 

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