Лако-красочные материалы — производство

Perhaps the most apt definition of analysis of adhesives is their qualitative and quantita­tive characterization. Since the early days of adhesive development, the elementary che­mical analysis of adhesives has provided valuable information on the structure and purity of materials. Chemical methods of analysis are simple and cheap but labor intensive. The use of such techniques for analysis has been decreasing over the past 30 years. This is due to the complexity of the polymeric structures of adhesives as well as the development of much powerful and sophisticated instrumentation. More recently, advances in computer technology have been combined with analytical instruments to give speed, resolution, simplicity, and minimal sample requirements that were unimaginable two decades ago.

Adhesives may be synthesized by many processes; very often the precise conditions used have an effect on the structure of the product. Because of the statistical nature of the polymerization process, most polymers show a distribution of molar mass or molecular weights, which may be averaged in several different ways. Any physical or performance property of a polymer may be related to one or more average molecular weights, the type of average being determined by the physical averaging process inherent in the method used to measure the property. Thus, a complete description of the molecular weight distribution of a polymer is important to understand its physical, rheological, and mechanical proper­ties. Hence a separation technique, gel permeation chromatography (GPC), which has proven to be useful for determination of molecular weight and molecular weight distribu­tion, is discussed. The use of spectroscopic methods for the characterization of adhesive systems has provided important molecular level descriptions of these systems. Thus Fourier transform infrared (FTIR) and Raman spectroscopy and nuclear magnetic reso­nance (NMR) are described. Many adhesives are network polymers that are insoluble and as a result are not as easily characterized by the conventional methods, including GPC, which require dissolution. For these adhesives, thermal techniques have been used popu­larly to study chemical kinetics of curing reactions, curing behavior, degradation reac­tions, and transition of molecules. Thus three thermal analysis techniques, namely, differential thermal analysis (DTA), differential scanning calorimetry (DSC), and dynamic mechanical thermal analyzer (DMTA) are described.