Block copolymers polyamide-polyether

Thermoplastic polyester rubbers are also block copolymers of polyethers and polyesters. The polyester groups are capable of crystallisation and the crystal structures act like cross-links. These materials have good hydrocarbon resistance. Similar thermoplastic polyamide rubbers are also now available. 

Polyamide block copolymer with polyether/polyester PVC... 

Table 4.4 Carbon dioxide (A)/nitrogen (B) permselectivity characterization for polyimide, polyurethane and polyamide block-copolymers containing polyether segments.

Polyamide TPEs are usually polyester-amides, polyetherester-amide block copolymers, or polyether block amides. Polyamide TPEs are characterized by then-high service temperature under load, good heat aging, and solvent resistance. The copolymers are used for waterproof/breathable outerwear, air conditioning hose, under-hood wire covering, automotive bellows, flexible keypads, decorative watch faces, rotationally molded sports balls, and athletic footwear soles. Producers include Elf Atochem (Pebax). 

Polyamide TPEs are usually either polyester-amides, polyetherester-amide block copolymers, or polyether block amides (PEBA) (see Fig. 3.7). PEBA block copolymer molecular architecture is similar to typical block copolymers. The polyamide is the hard (thermoplastic) segment, whereas the polyester, polyetherester, and polyether segments are the soft (elastomeric) segment. ... 

Table 6. Trade Names of Multiblock Thermoplastic Elastomers Based on Polyurethane/Elastomer, Polyether/Elastomer, and Polyamide/Elastomer Block Copolymers...

A wide range of polyether-polyamide block copolymers were first offered by Atochem in 1981 under the trade name Pebax. These are made by first producing a low molecular weight polyamide using an excess of dicarboxylic acid at a temperature above 230°C and under a pressure of up to 25 bar. This is then combined with a polyether by reaction at 230-280°C under vacuum (O.l-lOTorr) in the presence of a suitable catalyst such as Ti(OR)4. 

Table 18.16 Selected properties of polyether-polyamide block copolymers of the Pebax type (After Deleens, 1987)...

Membranes comprising silicone rubber coated onto polyimides, polyacrylonitrile or other microporous supports membranes are widely used [12,27]. Other rubbers such as ethylene-propylene terpolymers have been reported to have good properties also [28]. Polyamide-polyether block copolymers have also been used for pervaporation of some polar VOCs [29,30]... 

Polyamide-polyether block copolymers (Pebax , Elf Atochem, Inc., Philadelphia, PA) have been used successfully with polar organics such as phenol and aniline [32-34], The separation factors obtained with these organics are greater than 100, far higher than the separation factors obtained with silicone rubber. The improved selectivity reflects the greater sorption selectivity obtained with the polar organic in the relatively polar polyamide-polyether membrane. On the other hand, toluene separation factors obtained with polyamide-polyether membranes are below those measured with silicone rubber. 

In contrast, organophilic PV membranes are used for removal of (volatile) organic compounds from aqueous solutions. They are typically made of rubbery polymers (elastomers). Cross-linked silicone rubber (PDMS) is the state-of-the-art for the selective barrier [1, 43, 44]. Nevertheless, glassy polymers (e.g., substituted polyacetylene or poly(l-(trimethylsilyl)-l-propyne, PTMSP) were also observed to be preferentially permeable for organics from water. Polyether-polyamide block-copolymers, combining permeable hydrophilic and stabilizing hydrophobic domains within one material, are also successfully used as a selective barrier. 

Polyurethane-based FTPEs are produced by reacting fluorinated polyether diols with aromatic disocyanates. The resulting block copolymers contain fluorinated polyether soft segments.68 Another possible method of preparation of fluorinated TPE is dynamic vulcanization. Examples are a blend of a perfluoroplastic and a perfluoroelastomer containing curing sites or a combination of VDF-based fluo-roelastomers and thermoplastics, such as polyamides, polybutylene terephtalate, and polyphenylene sulhde.69 70... 

Polyamide-polyether (PA-PEG) block copolymers have been studied using deuterated water (2H20) molecules as 2H NMR probes [85, 86, 87]. Well resolved doublets are observed on 2H20 on stretching the samples at room temperature. At a given elongation ratio X, the splitting depends on the water concentration c. The linewidth is that of a liquid and becomes comparable to that in bulk water for c=0.6. This confirms that water... 

Tsubouchi and Yoshikawa [79] are concerned with pervaporation separation of benzene/cyclohexane mixtures using membranes based on polyamide/polyether block copolymers. It has been established that the separation factor increases with the increase in the polyamide component containing polar amide groups capable of forming hydrogen bonds e.g., the 1 1 block copolymer of polyamide 12 and polyoxyethylene has the benzene/cyclohexane separation factor /3p = 2.8 and the flux 2 = 300 g/m h a more rigid 3 1 polyamide 12/polyoxyethylene block copolymer has a much higher separation factor )8p = 5.0 and 2 = 80 g/m h. 

Tsubouchi K and Yoshikawa M. Pervaporation separation of benzene/cyclohexane mixtures through polyamide-polyether block copolymer membranes. Membrane (Maku) 1998 23(6) 322-326. 

Thermoplastic elastomers are most commonly formulated from elastomeric polyurethane or block copolymers of polystyrene-elastomer, polyamide-elastomer, or polyether-elastomer bases. Thermoplastic elastomers are provided as a raw material in pelletized form for subsequent compounding. The internal domain structure that is required for thermoplastic-elastomeric performance has been established by specific considerations of blending and structural-chemical interactions. In compounding operations, specific temperature ranges are required to assure that phase separation does not occur in the TPE base polymer. 

Tphe surface activity of block copolymers containing dimethylsiloxane units as one component has received considerable attention. Silicone-poly ether block copolymers (1,2,3) have found commercial application, especially as surfactants in polyurethane foam manufacture. Silicone-polycarbonate (4, 5), -polystyrene (6, 7), -polyamide (8), -polymethyl methacrylate (9), and -polyphenylene ether (10) block copolymers all have surface-modifying effects, especially as additives in other polymeric systems. The behavior of several dimethylsiloxane-bisphenol A carbonate block copolymers spread at the air—water interface was described in a previous report from this laboratory (11). Noll et al. (12) have described the characteristics of spread films of some polyether—siloxane block co-... 

NNMR spectra of polyamide/polyether block copolymers based on polyethylene oxide) and either nylon-6 or nylon-12 are dominated by peaks at approximately 119 ppm, arising from the amorphous nylon phase. In addition, both polymers also exhibit a shoulder. Downfield (about 112 ppm) and upheld (about 117 ppm) shoulders indicate that polyamide phases exist as a (nylon-6) and y (nylon-12) forms, respectively (62). 

The membrane material is decisive for the removal efficiency. Urkiaga et al. [129] tested different commercially available membranes on their adsorption characteristics for MTBE showing that sihcone rubber was more efficient than polyether-polyamide block-copolymer membranes (PEBA) and polyoctyl methyl siloxane membranes (POMS) at MTBE concentrations of 250mg/L and 1250 mg/L. The studies by Keller et al. [128] and Vane et al. [130] used polypropylene and silicone rubber membranes, respectively. 

Several classes of polymeric materials are found to perform adequately for blood processing, including cellulose and cellulose esters, polyamides, polysulfone, and some acrylic and polycarbonate copolymers. However, commercial cellulose, used for the first membranes in the late 1940 s, remains the principal material in which hemodialysis membranes are made. Membranes are obtained by casting or spinning a dope mixture of cellulose dissolved in cuprammonium solution or by deacetylating cellulose acetate hollow fibers [121]. However, polycarbonate-polyether (PC-PE) block copolymers, in which the ratio between hydrophobic PC and hydrophilic PE blocks can be varied to modulate the mechanical properties as well as the diffusivity and permeability of the membrane, compete with cellulose in the hemodialysis market. 

In reaction injection moulding (RIM), two monomers are injected into a mould, where polymerisation and crosslinking occur. It is used mainly with polyurethanes to make large automotive panels. The chemistry of polyurethanes was described in Chapter 4. Other systems used include a block copolymer between a crystalline polyamide (nylon 6) and a rubbery polyether (polypropylene oxide). In principle, any polymerisation reaction that can be substantially completed after about 30 s in the mould is a candidate for RIM. 

Louie JS, Pinnau I, Ciobanu I, Ishida KP, Ng A, and Reinhard M, Effects of polyether-polyamide block copolymer coating on performance and fouling of reverse osmosis membranes, Journal of Membrane Science 2006, 280, 762-770. 

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