Hydrolysis of Polyamides

Hydrolysis of polyamide-based formulations with 6 N HC1 followed by TLC allows differentiation between a-aminocaproic acid (ACA) and hexamethylenedi-amine (HMD) (hydrolysis products of PA6 and PA6.6, respectively), even at low levels. The monomer composition (PA6/PA6.6 ratio) can be derived after chromatographic determination of the adipic acid (AA) content. Extraction of the hydrolysate with ether and derivatisa-tion allow the quantitative determination of fatty acids (from lubricants) by means of GC (Figure 3.27). Further HC1/HF treatment of the hydrolysis residue, which is composed of mineral fillers, CB and nonhydrolysable polymers (e.g. impact modifiers) permits determination of total IM and CB contents CB is measured quantitatively by means of TGA [157]. Acid hydrolysis of flame retarded polyamides allows to determine the adipic acid content (indicative of PA6.6) by means of HPLC, HCN content (indicative of melamine cyanurate) and fatty acid (indicative of a stearate) by means of GC [640]. Determination of ethylene oxide-based antistatic agents... 

Almansa E, Heumann S, Eberl A et al (2008) Surface hydrolysis of polyamide with a new polyamidase from Beauveria brongniartii. Biocatal Biotrans 26 371-377... 

Chapter 5 shows that the application of hydrolytic enzymes is a powerful yet mild strategy to directly improve polymer surface properties (i.e. hydrophilicity) or activate materials for further processing. The surface hydrolysis of polyamides (PA), polyethyleneterphthalates (PET) and polyacrylonitriles (PAN) is discussed, as well as the mechanistic details on the enzymatic surface hydrolysis. The mechanistic data, combined with advances in structural and molecular biology, help to explain different activities of closely related enzymes on polymer surfaces. 

Finally, it is necessary to explain the possible causes of the discussed hydrolysis of polyamides during processing. The following test series demonstrates one case of this phenomenon - (residues of) active catalysts from the polycondensation... 

Scheme 1.74. The mechanism for acid hydrolysis of polyamide leading to chain scission and amine and carboxylic acid end groups. After Zaikov (1985).

Due to the presence of moisture on the surface or environment, NO forms HNOj and HNO. Hydrolysis of polyamide-6 may occur in acidic conditions. Water protonates amide and hydroxyl functionalities and results in chain scission. The attack might have occurred in the amorphous region of the crystal structure, where the water diffusion occurs in a limited manner by the dispersed clay platelets. 

The ratio of CHj to CONH groups, the hydrogen ion concentration in the acid (pH-value), diffusion rate, temperature, and the degree of crystallization are decisive factors for the hydrolysis of polyamides. The smaller the CH2/CONH ratio, the more... 

The selective hydrolysis of polyamides and that of linear polyestes, and so... 

Hydrolysis and Polycondensation. One of the key properties of polyamides relates to the chemical equihbrium set up when the material is polymerized. The polymerization of nylon is a reversible process and the material can either hydrolyze or polymerize further, depending on the conditions. 

Seb cic Acid. Sebacic acid [111-20-6] C QH gO, is an important intermediate in the manufacture of polyamide resins (see Polyamides). It has an estimated demand worldwide of approximately 20,000 t/yr. The alkaline hydrolysis of castor oil (qv), which historically has shown some wide fluctuations in price, is the conventional method of preparation. Because of these price fluctuations, there have been years of considerable interest in an electrochemical route to sebacic acid based on adipic acid [124-04-9] (qv) as the starting material. The electrochemical step involves the Kolbn-type or Brown-Walker reaction where anodic coupling of the monomethyl ester of adipic acid forms dimethyl sebacate [106-79-6]. The three steps in the reaction sequence from adipic acid to sebacic acid are as follows ... 

Acid anhydride-diol reaction, 65 Acid anhydride-epoxy reaction, 85 Acid binders, 155, 157 Acid catalysis, of PET, 548-549 Acid-catalyzed hydrolysis of nylon-6, 567-568 of nylon-6,6, 568 Acid chloride, poly(p-benzamide) synthesis from, 188-189 Acid chloride-alcohol reaction, 75-77 Acid chloride-alkali metal diphenol salt interfacial reactions, 77 Acid chloride polymerization, of polyamides, 155-157 Acid chloride-terminated polyesters, reaction with hydroxy-terminated polyethers, 89 Acid-etch tests, 245 Acid number, 94 Acidolysis, 74 of nylon-6,6, 568... 

While additive analysis of polyamides is usually carried out by dissolution in HFIP and hydrolysis in 6N HC1, polyphthalamides (PPAs) are quite insoluble in many solvents and very resistant to hydrolysis. The highly thermally stable PPAs can be adequately hydrolysed by means of high pressure microwave acid digestion (at 140-180 °C) in 10 mL Teflon vessels. This procedure allows simultaneous analysis of polymer composition and additives [643]. Also the polymer, oligomer and additive composition of polycarbonates can be examined after hydrolysis. However, it is necessary to optimise the reaction conditions in order to avoid degradation of bisphenol A. In the procedures for the analysis of dialkyltin stabilisers in PVC, described by Udris [644], in some instances the methods can be put on a quantitative basis, e.g. the GC determination of alcohols produced by hydrolysis of ester groups. 

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,... 

The molecular weight increases with increasing conversion. Regulation of the molecular weight can be achieved by adding small amounts of substances (e.g., benzoic acid) that can react with the polyamide chains by transamidation. Because of the transamidation reaction and hydrolysis of amide bonds, an equilibrium molecular-weight distribution is finally attained (see Sect. 4.1). 

Many properties of polyamides are attributable to the formation of hydrogen bonds between the NH and CO groups of neighboring macromolecules. This is evidenced by their solubility in special solvents (sulfuric acid, formic acid, m-cresol), their high melting points (even when made from aliphatic components), and their resistance to hydrolysis. In addition, polyamides with a regular chain structure crystallize very readily. 

A lipase from Rhizomucor miehei is immobilized onto a porous polyamide support with a bead diameter of 0.3 mm and used for the hydrolysis of 100 mM caprylin at pH 7.0 and 30°C, in a continous plug flow reactor. Calculate the amount of immobilized lipase needed to achieve a conversion degree of 97% with an inlet flow rate of 1 l.min ... 

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