Melt blending/blended

Transamidation is an important process in the melt phase for polyamides because it is usually the process by which an equiUbrium molecular weight distribution is reestabUshed and, in the case of the melt blending of two or more polyamides to form a copolymer, it is the process by which randomi2ation of the individual monomers along the chain is effected. In the soHd phase, chain mobiUty is restricted and equiUbrium in either case often is not achieved. 

Noryl. Noryl engineering thermoplastics are polymer blends formed by melt-blending DMPPO and HIPS or other polymers such as nylon with proprietary stabilizers, flame retardants, impact modifiers, and other additives (69). Because the mbber characteristics that are required for optimum performance in DMPPO—polystyrene blends are not the same as for polystyrene alone, most of the HIPS that is used in DMPPO blends is designed specifically for this use (70). Noryl is produced as sheet and for vacuum forming, but by far the greatest use is in pellets for injection mol ding. 

Most elastomers that are used for nylon modification contain a small amount of maleic anhydride (0.3 to 2%). In the melt blending process, these elastomers react with the primary amine end groups in nylon, giving rise to nylon grafted elastomers. These grafts reduce the interfacial tension between the phases and provide steric stabili2ation for the dispersed mbber phase. Typically, thermally stable, saturated mbbers such as EPR, EPDM, and styrene—ethylene/butylene—styrene (SEBS) are used. 

The effect of a second polymer blended with PPS which causes enhanced nucleation of PPS has been previously observed. It was found that low concentrations (1—2 wt %) of poly(phenylene sulfide ketone) and poly(ether ether ketone), when melt-blended with PPS, function effectively to increase the nucleation density of PPS (149). 

There has also been some interest in melt blending with polyamides to increase the toughness but at some sacrifice to dimensional stability and moisture resistance. 

Prior to blending, the LCP was dried at 155°C for 5 h. The melt blending of the materials was carried out with a Berstorff ZE 25 x 33D corotating twin-screw extruder at a melt temperature of 290°C, with a screw speed of 200 rpm, and an output of 6.4 kg/h. The extrudate was immediately quenched in a water bath and repelletized. 

Low-draw ratio (I I) in melt blending (L) High-draw ratio (6 1) in melt blending (H) ... 

The melt blends exhibited the best mechanical properties, which could be still further improved with additional drawing. The composites Hel-He4 could not be drawn to improve the mechanical properties. In the case of the melt blends, even higher draw ratios than used in this study will increase the fibrillation and orientation of the LCP phase leading to significant improvements in strength and modulus [21,30]. 

Shear viscosities of the twin-screw blended materials were measured at 190°C and 290°C (Fig. 6), the same temperatures as the melt temperatures during processing 190°C for the composites and 290°C for the melt blends. 

The addition of LCP sharply decreased the viscosity of PP in the melt blends, but increased it in the composites. The increase in viscosity effected by the solid LCP fibers was nevertheless surprisingly small. 

The materials were dried in a vacuum oven at 115°C for 24 h. They were then melt blended by using a domestic twin-screw extruder ( 35) [screw diameter = 35 mm]. The weight ratios of PES-TLCP were 90 10 and 70 30, respectively [12]. 

Many random copolyesters and polyester-polycarbonates have also been prepared by ester interchange reactions in the molten state. Thus, poly(ethylene terephthalate-co -isophthalates) can be obtained by simple melt blending of PET and poly(ethylene isophthalate) (PEI) homopolyesters at 270°C. The copolymer changes gradually from a block type at the beginning of reaction to a random-type... 

The problem of carpet recycling is considered and the different methods being proposed or commercially utilised are discussed. The main component of the carpet waste is fibres of nylon-6 and nylon-66. The review of the literature includes a limited amount of journal publications, which focus primarily on fundamental aspects, and a large number of patents, which describe the available technologies. The most promising recycling techniques (depolymerisation, extraction, melt blending and mechanical separation) are described. 48 refs. 

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