Pebax copolymers

Detailed information on the synthesis of PEBA is presented in Chapters 2 and 10 and also in [13-16]. However, it is worth mentioning here that commercially available poly (ether- -amide) PEBAX copolymers are synthesized by melt polycondensation of carboxylic acid-terminated amide blocks with poly-(oxyalkylene glycol)s. The polymerization is catalyzed by a metal alkoxide Ti(OR)4 and is carried out at elevated temperatures of ca. 230°C under vacuum. These copolymers are marketed for use in many areas, a few of which include sports equipment, automotive components, applications that require polymers with antistatic properties, and also in biomedical applications, such as tubing and catheter balloons [17]. There is also a growing body of literature on the use of PEBAX in the manufacture of membranes for gas separations. Vestamid E-Series elastomers marketed by Degussa-Htils are another commercial example of PTMO-PA12 based PEBA 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)...

Block copolymers can contain crystalline or amorphous hard blocks. Examples of crystalline block copolymers are polyurethanes (e.g. B.F. Goodrich s Estane line), polyether esters (e.g. Dupont s Hytrel polymers), polyether amides (e.g. Atofina s Pebax grades). Polyurethanes have enjoyed limited utility due to their relatively low thermal stability use temperatures must be kept below 275°F, due to the reversibility of the urethane linkage. Recently, polyurethanes with stability at 350°F for nearly 100 h have been claimed [2]. Polyether esters and polyether amides have been explored for PSA applications where their heat and plasticizer resistance is a benefit [3]. However, the high price of these materials and their multiblock architecture have limited their use. All of these crystalline block copolymers consist of multiblocks with relatively short, amorphous, polyether or polyester mid-blocks. Consequently they can not be diluted as extensively with tackifiers and diluents as styrenic triblock copolymers. Thereby it is more difficult to obtain strong, yet soft adhesives — the primary goals of adding rubber to hot melts. 

The composition of the test sample was compared to literature values for commercial PA-12/TMG block copolymers marketed under the trade name PEBAX . PEBAX 5533 typically has a PA-12 content of 62wt%, and PEBAX 6333 has a PA-12 content of 76wt%. From the NMR data, the test sample has a composition most similar to PEBAX 6333. 

Pebax, commercial block copolymer, 7 648t Pebble mills, 25 64 Pebble quicklime, 15 28 Peclet numbers (Pe), 2 63 10 763 22 746 25 686t, 687t 25 279. See also Mass transfer Peclet number (PeMT) axial dispersion in bubble tray absorbers, 2 89... 

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. 

The above thermal analysis studies demonstrated the enhanced thermal stability of POSS materials, and suggested that there is potential to improve the flammability properties of polymers when compounded with these macromers. In a typical example of their application as flame retardants, a U.S. patent39 described the use of preceramic materials, namely, polycarbosilanes (PCS), polysilanes (PS), polysilsesquioxane (PSS) resins, and POSS (structures are shown in Figure 8.6) to improve the flammability properties of thermoplastic polymers such as, polypropylene and thermoplastic elastomers such as Kraton (polystyrene-polybutadiene-polystyrene, SBS) and Pebax (polyether block-polyamide copolymer). 

Newer materials are being developed which lie between plastics and elastomers. One of these is a polyether block amide copolymer developed by ATO Chemie, Europe, called Pebax. This is a tough, highly flexible material which by changing the ratio of ether and amide can have a wide balance between hardness and flexibility. Currently this material is relatively expensive ( 3,000- 5,000 per tonne). 

Poly(amide-b-ethylene oxide) copolymers were presented in 1990 as a promising membrane material [43]. These block copolymers were developed in 1972 but in 1981 began to be used for commercial purpose under the trade name Pebax , produced by ATOCHEM [44] (now ARKEMA). Another important group of segmented poly(ester)s used for membranes are block copolymers based on PEO and PBT (poly(butylene tereph-thalate), known under commercial name of Polyactive [45]. By changing the polyamide and polyether segment, molecnlar mass and the content of each block, the mechanical, chemical, and physical properties are nicely tnned as well [46]. 

Figure 12.1 presents the chemical structure of poly(amide-b-ethylene oxide) (commercial name Pebax ) and poly(ethylene oxide)-poly(butylene terephthalate) (PEO-PBT) (commercially known as Polyactive ). These copolymers with high content of PEO are hydrophilic and show excellent chemical resistance towards solvents. The solubility of these copolymers in different solvents is determined by the ratio of segmented blocks. Pebax MH 1657 is soluble only in few solvents and generally the polymer solution is prepared under reflux at high temperature and low polymer concentration by using n-butanol or a mixture of n-butanol/l-propanol, after cooling down to room temperature. 

Erom all the commercial copolymers presented in Table 12.1, Pebax 1657, 1500PE077PBT and 4000PE055PBT (Polyactives) have high CO2 selectivity over H2 and N2 and moderate CO2 permeability, thus by adding PEG with low molecular weight, their CO2 permeability can be improved without affecting the selectivity [24,67]. The other... 

Table 12.1 Physical and gas transport properties of Pebax and Polyactive multi-block copolymers [24,64-67]...

Pebax /PEG and 40000PE055PBT/PEG exhibit similar trend (experimental data) the higher the PEG content, the higher the permeability. 1500PE077PBT/PEG blends, however, are different permeability increases and then is reduced below theoretical values calculated by the additive model. It can be observed that every copolymer shows different behaviour hence, the selection of an appropriate additive for a specific copolymer is very important. 

On the other hand, pristine 4000PE055PBT45 copolymer showed two characteristic Tni values (40 °C for PEO and 213 for PBT, see Table 12.2). It is consistent with the microphase separated slnictme in block copolymers [91]. For the blend samples for the PEO crystalline phase was shifted to higher values when PEG is added into the polymer matrix (Figme 12.12a). These results are in contradiction to those observed in Pebax/PEG system reported earlier [24]. High PEG content slightly increases the crystallinity from 19% (pristine polymer) to 24% (blend with 50% of PEG). values of PBT... 

The novel developed membrane materials should have potential applications on a large scale. The composite membrane preparation and its evaluation therefore must present promising results before testing the membranes in a real gas mixture. Single gas (CO2, H2, N2 and CH4) measurements of Pebax /PEG blend membrane at high pressure (up to 20 bar) and at 293 K presented higher CO2 fluxes than pristine copolymer (Figure 12.14). 

It should be noted that Car et al. [10,11] (see also Chapter 12 of this volume) worked independently on similar blend manbranes, which were made of Pebax 1657, a grade of commercial poly(amide-b-ether) block copolymer with six polyamide blocks, and free PEG. Those membranes were also shown to exhibit high selectivity and permeability performances, which were attribnted to changes in both the chemical composition (i.e. higher EO content) and the morphological stmctuie (i.e. lower material crystallinity). On the contrary, Jaipurkar [12] observed CO2 permeability and selectivity improvements for the blend of Pebax 2533 with 25% of PEG 10000, bnt not for the blends with other PEG molecular weights or composition. 

Those results motivated us, in the present work, to stndy the structure, physical characteristics and gas transport properties of membranes made of different grades of Pebax block copolymers and their blends with PEG (Table 13.1). 

Pebax polyether block amide copolymers consist of regular linear chains of rigid polyamide blocks and flexible polyether blocks. They are injection molded, extruded, blow molded, thermoformed, and rotational molded. 

There are two generic types of permanent antistats hydrophilic polymers and inherently conductive polymers. Hydrophilic polymers are currently the dominant permanent antistats in the market. Typical materials that have been used successfully are such polyether block copolymers as PEBAX from Atochem. Typical use levels for these materials are in excess of 10%. B.F. Goodrich is supplying compounds utilizing their permanent antistat additive, STAT-RITE. Office automation equipment, such as fax and copier parts, is the principal application for permanent antistats based on hydrophilic polymers. The most common resins are ABS and high-impact polystyrene (HIPS). 

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). 

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