Polyamide chains grafted

A telechelic polystyrene containing two carboxyl groups at one end of a polymer can be used as a macromonomer in a step polymerization with a diol or diamine to yield a polyester or polyamide containing graft chains of polystyrene. The required telechelic polymer is obtained by radical polymerization of styrene in the presence of 2-mercaptosuccinic acid. 

Several ester monomers have also been studied. In methanol solution, methyl acrylate (16,21), ethyl acrylate (21,54), 2-ethyl hexyl acrylate (55), allyl acrylate (44), glycidyl acrylate (56,57) usually in methanol solution, have been extensively studied. Methyl methacrylate (19, 21, 28, 30, 36, 39, 58) in diversified media composition, has been successfully grafted on polyamides. Vinyl acetate is reported also for grafting on polyamide backbone (19, 28, 35, 58), as well as n-butyl maleate in methanol solution (55). Diallyl maleate as cross-linking agent for polyamide chains is reported (44). Other less usual ester monomers have been mentioned in the literature to form grafts (41,59,60). 

Runs 1-4 clearly show that, in the absence of AcCL, even if the CL conversion does not exceed 20%, graft copolymers having up to 32% by weight of polyamide can be obtained. It is interesting that, except for run 4, the polymerized CL was found mostly as grafted polyamide chains and, to a smaller extent, as PA 6 homopolymer. Slightly better results were obtained in the bulk polymerizations with respect to those carried out in the presence of xylene under the same experimental conditions. 

Figure 10.7 Illustration of how in situ polymerisation can lead to grafted polyamide chains (one plate surface only shown for clarity)...

Exhaustive solvent extraction of the extruder blended products with triflouroethanol (TFE), a polyamide solvent, indicated that a substantial amount of unextractable PA6 was usually bound to the reactive rubbers via the graft-coupling reactions. In the case of PA6/ maleated EPR (80/20) blend, >20% of PA6 is bound to the rubber as a graft copolymer. In the case of the PA6 blend compounded with 20% zinc ionomer of ethyiene-methacrylic acid copolymer (E-MAAZn), the TFE extraction indicated only <3% bound PA6. However, the blend showed a moderate torque increase in the Rheomixer experiment. These results indicate that the E-MAAZn ionomer does not bond covalently with the polyamide chains, but more likely interacts via a simple associative interaction occurring at the interface. 

To obtain the graft copolymer a copolycondensation involving an co-dihydroxylic macromonomer together with a diol (such as butanediol) and a diisocyanate (toluene diisocyanate or hexa-methylene diisocyanate) is carried out. Alternately, an co-dicarboxylic macromonomer is reacted with a diacid e.g. sebacic acid) and a diamine (such as phenylenediamine or hexamethylenediamine) (Scheme 31). " The backbone chain is constructed during the poiycondensation process, and each macromonomer incorporated results in a graft. This method offers interesting possibilities of grafting vinylic or acrylic chains onto a polyurethane backbone or onto a polyamide chain. 

The molecular weight of the grafted chain of polyacrylic acid, determined by acid hydrolysis, is of the order of 10000. The product differs markedly from the original polyamide in electrochemical properties. As a confirmation of a radical mechanism, radical acceptors prevented the reaction (see Fig. 5). The possibility of a minor and competitive ionic mechanism was also considered. 

Aqueous solution of acrylamide has been chosen as the grafting system for polyamidic filaments that had been preheated under gamma-rays, in air (35,48). If the filaments were irradiated under nitrogen, grafting occurs on the surface, but if the high energy treatment is carried on in air, the side chains are formed also inside the fiber (61). 

In full agreement with this explanation it was recognized that by a certain side reaction very strong cross links are formed during the polymerization. If a polymide was used as cocatalyst (a polymer styrene-methacryloyl caprolactam) the grafted polyamide side chains were joined in the very beginning of the polymerization and a crosslinked polymer resulted (92). 

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