Destruction of the resins structure due to heating
This article considers a polymer composition based on acetone-formaldehyde (AFR) resin, which is used to reduce water influx into the well bore during the repair insulation work. Pumping into the well bore a composition, based on AFR resin, results in self-heating that causes destruction of its own structure and, therefore, the damage of the polymer blend structure. The purpose of the present article is to find the causes of AFR resin self-heating when injected into the well bore as part of the composite mixture that leads to the destruction of its structure. Author considers exothermic reaction between AFR resin and aqueous solution of sodium hydroxide during the curing of the polymer composition. The features of the given polymer structure are studied as well. The need for further studies of the resin structure is substantiated. Based on the study conducted, five possible reasons of the AFR resin self-heating, leading to destruction of resin structure, are revealed. Recommended practices that may decrease self-heating of the AFR resin are offered.
Colloid chemistry of polymers
1. General Colloid Chemistry of Polymers. General. Dispersion in colloidal polymer systems. 2. Microheterogeneous Structure of One- and Multi-Component Polymer Substances. Modern concepts of the structure of amorphous polymers. Structural heterogeneity of polymers. 3. Structure Formation in Disperse Polymer Systems. Thermodynamics of the formation of particles of a new phase. Theory of spinodal decomposition. Phase separation in polymer systems. Dissipative processes as a cause of microheterogeneity in polymer systems. 4. Surface Tension in Disperse Systems. Surface tension of solutions. Surface tension of polymer melts. Surface tension of solid polymers. 5. Surface-Active Properties of Polymers and the Influence of Low-Molecular-Mass Surfactants on the Properties of Disperse-Polymer Systems. Polymers as surfactants. Influence of surfactants on the properties of oligomers and polymers. Influence of surfactants on the strength and destruction of polymers. 6. Adsorption of Polymers on Solid Surfaces. Adsorption from dilute solutions. Isotherms of polymer adsorption from dilute solutions. Aggregation mechanism of adsorption. Some features of polymer adsorption kinetics on highly dispersed adsorbents. The role of adsorption layers of polymers in stabilizing disperse systems. Adsorption from polymers blends. 7. Polymer Adhesion. Thermodynamic description. Adhesion strength. Adhesion theory. Mechanism of adhesion joint formation. Internal stresses in adhesion joints. Colloid-chemical approaches to the increase of adhesion strength. 8. Structure and Properties of Surface and Interfacial Polymer Layers. Surface layers of polymer phases. Surface layers of polymers on the surface of solids. Interfacial layers in heterogeneous mixtures of polymers. Features of the interfacial region structure in polymer mixtures. Microheterogeneity of surface layers. Monomolecular layers of polymers. 9. Filled Polymers as Disperse Systems. General. Structure formation in polymers in the presence of dispersed fillers. Mechanical properties of filled polymers. Rheological properties of filled polymers. Surface modifications of fillers. Mechanisms of reinforcing action of fillers in polymers. Polymers filled with colloidal metals. 10. Colloidal Mixtures of Polymers. Theoretical concepts of mixing and compatability of polymers. Empirical determination of polymer compatability. Features of diagrams of the state of binary mixtures. Rheological properties of binary mixtures. 11. Colloid-Chemical Features of Polymer-Polymer Systems. Separation of polymer-polymer systems. Thermodynamics of the formation of stable dispersion systems. Dispersity of polymer-polymer compositions. Colloidal and chemical structure of polymer-polymer systems. 12. Gelation of Solutions Polymer Gels. Classification of polymer gels. Gel-formation conditions. Mechanism of gel-formation processes and structure of polymer gels. Phase state of polymer gels. Polymer gels as disperse colloidalsystems. 13.
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.