Polyamide Graft Copolymers

Assignee University of Florida Research Foundation, Inc. (Gainesville, FL) 

Polyamide copolymers containing a macromolecular graft substituent were prepared by condensing 4-amino-benzoic acid or a mixture of 1,4-phenylene diamine and adipic acid with 33%, 66%, and 90% 5-(poly(n-butylacrylate)cysteine macromonomer. A second macromolecular monomer, 5-(poly(methyl methacrylate)-cysteine, was also prepared and free radically copolymerized with perfluoromethyl methacrylate. 

Preparation of S-(Poly(n-Butyl Acrylate)-Cysteine Macromonomer 

The synthesis of poly(butyl acrylate) in the presence of cysteine was carried out using THF, ethyl alcohol, and water where the molar ratio of butyl acrylate monomer/ cysteine/azobisisobutyronitrile was 1000 30 1, respectively. The mixture was then refluxed for 6 hours at 65°C while under constant stirring. After cooling the cysteine-modified product consisted of a white precipitate dispersed within poly(butyl acrylate). The precipitate was isolated from the polymer by dissolving the poly(butyl acrylate) in THF and filtering. 

Preparation of Poly(4-Amino-Benzoic Acid-co-(Cysteine-g-Poly (/i-Butyl Acrylate)) 

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Keywords Block copolymers, Interface reactive injection moulding, Polyamide degradation, Polyolefine polyamide graft copolymers, PTFE polyamide materials... 

Grafting can also occur in the amide nitrogen, either through an anionic-type mechanism which is beheved to operate when ethylene oxide [75-21 -8] and similar copolymers are grafted to polyamides, or through a polycondensation mechanism when secondary amides are formed as graft copolymers (70). 

Polypropylene block and graft copolymers are efficient blend compatibilizers. These materials allow the formation of alloys, for example, isotactic polypropylene with styrene-acrylonitrile polymer or polyamides, by enhancing the dispersion of incompatible polymers and improving their interfacial adhesion. Polyolefinic materials of such types afford property synergisms such as improved stiffness combined with greater toughness. 

Els and McGill [48] reported the action of maleic anhydride on polypropylene-polyisoprene blends. A graft copolymer was found in situ through the modifier, which later enhanced the overall performance of the blend. Scott and Macosko [49] studied the reactive and nonreactive compatibilization of nylon-ethylene-propylene rubber blends. The nonreactive polyamide-ethylene propylene blends showed poor interfacial adhesion between the phases. The reactive polyamide-ethylene propylene-maleic anhydride modified blends showed excellent adhesion and much smaller dispersed phase domain size. 

The first sample is a reactive poly(tetrafluoroethylene)/polyamide 6 (PTFE/ PA) blend [43]. When mixing PTFE micro-powder and PA in an extruder at about 280°C, relatively large PTFE particles occur in the final product because of immiscibility. By irradiation with electrons in air reactive groups in the PTFE powder are formed. These functionalised particles react with the molten PA in the extruder, and graft copolymers are formed, improving the compatibility of the components. At the same time a decrease in PTFE particle size proportional to the irradiation dose can be observed, and a PTFE/PA compound with better properties is produced. 

Baramboim and coworkers (93-95, 95 bis) obtained graft copolymers based on polyamides. The extrusion of a polypropylene polycaprolactam mixture at 200-210° C changed the polypropylene molecular weight and formed a block and graft copolymer of linear and three dimensional structure. Investigations showed the radical nature of the process and that the amount of the resulting copolymer was proportional to the intensity of mechanical shear. 

The use of polyamide solutions for the preparation of graft copolymers is restricted to monomer and initiator systems able to be dissolved and stand strongly polar media such as phenols, organic or inorganic strong adds, or aqueous salt solutions, which are common solvents for the backbone polymer. 

Acrylic acid can be used simultaneously as a monomer and as the solvent, the polyamide solution being frozen at dry ice temperature and ground in a vibration mill. The graft copolymer is said to be formed by mechanosynthesis and was confirmed by nitrogen analysis and solubility as well as swelling characteristics (5). 

Graft copolymers of polyamides using pre-irradiation gamma-rays techniques have been reported for styrene (130), in solution, in the presence of water (40), in alcohols or acetone solution (131), vinyl acetate (130), methacrylic acid in water (132) or methanol solution (129), methyl (133) and ethyl (130) acrylates, 2-ethylhexyl acrylate (55,134), methyl methacrylate (130), in methanol solution (129), 2-dimethylamino ethyl methacrylate quaternary salts (135), acrylamide in aqueous medium (128,136), acrylonitrile (130,137), and 4-vinyl pyridine in aqueous solution (128). 

Very often graft copolymers have been synthesized by the polyaddition of cyclic monomers, such as ethylene oxide, ethylene imine or caprolactam, to cellulose, proteins, polyamides, polyvinyl alcohol, etc. 

In this method the active hydrogen of the polymer is utilised to form graft copolymers. Polyamide is grafted with poly(ethylene oxide) as shown below ... 

FrelucheM et al. (2006) Graft copolymers of poly(methyl methacrylate) and polyamide-6 Synthesis by reactive blending and characterization. Macromolecules 39 6905... 

Alkyd and polyester resins, epoxy compounds, phenol-formaldehyde resin, urea and/or melamine-aldehyde resin, cyclic urea resin, carbamide acid ester formaldehyde resin, ketone formaldehyde resin, polyurethane, polyvinylester, polyvinyl acetate, polyvinyl chloride and polymer mixtures, polyethylene, polystryrene, styrene mixtures and graft copolymers, polyamide, polycarbonate, polyvinyl ether, polyacrylic and methacrylic acid esters, polyvinyl flouride, polyvinylidene chloride copolymers, UV and/or electron irradiated lacquers. 

Hergenrother, W.L. Matlock, M.G. Ambrose, R.J. Impact Resistant Polymeric Compositions Containing Polyamides, Maleic Anhydride Adducts of Hydrogenated Polymers, and Graft Copolymers Thereof. U.S. Patent 4,427,828, Jan 24, 1984 Firestone. 

By a similar degradation and graft copolymer formation mechanism block copolymers could be obtained by reactive extrusion. A prerequisite is the presence of functional groups and the interaction of these groups with immiscible polymers during melt processing. Several polyamide block copolymers are synthesised by a melt-modification process. 

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