Block copolyamides

Simple melt blending reactions can also be apphed to preparations of block copolyamides, similarly to the process for polyesters. With time, total equilibrium conditions also are gradually achieved in the melt [423]. Interfacial polycondensation is also useful in preparation of block copolymers. When mixed diacid chlorides and/or mixed diamines are reacted, the more active diacid chlorides and/or diamines react preferentially and blocks form. In addition, it is possible to carry out the growth of one of the segments first, to a fairly large size and follow it by addition of the other comonomers [424]. 

---

Block coal, 6 705 Block copolyamide, 79 739 Block copolymerization, 79 762 Block copolymers, 7 645-650 70 436 23 367... 

Property Polyurea Epoxy Poly(cyclo pentadiene) Block copolyamide A-B-A... 

Random block copolyamide-ethers (hard-soft block elastomers) were imaged, showing that thicker films contain much larger crystals of the hard block segments than those obtained with thin films (30-nm films had crystals of approximately 7 nm X 50-100 nm 20-/im films had crystals of about 12 nm x 200 nm). Further analysis also suggested that within the thicker films, more soft-segment is available at the surface compared to the thinner films (134). 

Reaction polymerization reactions of isocyanates with suitable monomers can he performed in an extruder or in a RIM machine. In the latter reaction thermosets (cross-hnked polymers) are produced. In an extruder usually linear polymers are manufactured. For example from methylene di-p-phenylene isocyanate (MDI), with some macroglycols and 1,4-hutanediol as extenders, segmented polyurethane elastomers are produced in an extruder (6). However, linear condensation polymers are also produced in a vented extruder. For example from MDI, with macrodicarboxylic acids and dicarboxyhc acids as extenders thermoplastic block copolyamide elastomers are produced. The by-product of the condensation reaction, carbon dioxide, is removed in the vented extruder. The polycondensation process can also be performed in solution. For example, MDI can be added to a solution of dicarboxyhc acids in tetramethylene sulfone, with simultaneous removal of the carbon dioxide. Tetramethylene sulfone is the solvent of choice for solution polymerization of isocyanates (7). In addition to dicarboxyhc acids trimellitic acid anhydride and benzophenonetetracarboxylic acid dianhydride (BTDA) are utilized as monomers for condensation polymers. With these monomers poly(amide imides) and poly(imides) are produced. The diisocyanate-derived commercial polycondensation products are listed in Table 1. 

Ohshimizu, K., Shibasaki, Y, Komura,M. etal. (2007) Synthesis and characterization of aromatic block copolyamides by condensative chain polymerization. Chemistry Letters, 36,742-743. 

Hydrolysis of Copolyamide-esters (CPAEs) by Lipase (jj,). CPAEs were synthesized by the amide-ester interchange reaction between polyamide and polyester. The length of the polyamide blocks was measured after hydrolysis of ester bonds in CPAE by alkali at 30 C. The infrared spectra after hydrolyzing ester bonds on CPAEs showed that the ester bonds were almost completely removed. The molecular weight distribution of polyamide blocks was examined by GPC (Table II). The following samples were used CPAE-1 (reaction time for synthesis, 1 hr) and CPAE-2 (reaction time, U hr) composed of nylon 6 and PCL at a 50/50 molar ratio, CPAE-3 (reaction time, 1 hr) and CPAE-U (reaction time,... 

By using mixtures of adipic and azelaic acids as monomers in the reaction with MDI, transparent copolymers are obtained useful as engineering thermoplastics. Also, copolyamides obtained from mixtures of isophthalic (IPA) and azelaic acids and MDI/TDI mixtures have been made. TDI in combination with MDI is used to lower the melt temperature of the IPA/MDI blocks to allow thermoplastic processing. 

In polyurethanes, copolyesters, and copolyamides, the molecular weight of each block is a key factor in determining the mechanical properties of the material. Soft segment block lengths between 1000 and 5000 g/mol have been... 

The chemical resistance of many TPEs is poor compared to that of conventional rubbers. Polyurethanes, copolyesters, and copolyamides are very susceptible to oxidation, especially at elevated temperatures. Antioxidants and other additives are added to commercial products to improve the chemical resistance of these materials. Carbon black can be added to improve stability to UV light if the color of the material is unimportant. Hydrolytic stability is poor for the polyester-based polyurethanes and the copolyamides because the ester linkage can be attacked by water. For all TPEs, certain organic solvents can degrade these materials if one or both of the blocks will dissolve in the particular solvent. The resistance to many common oils and greases is high for the more polar TPEs. 

Polyamide 666 or 6/66 is the designation given to copolyamides made from PA 6 and PA 66 building blocks. A precise structure cannot be drawn. 

---