The Influence of Fillers and Dyes on the Quality of Weld Joints at Ultrasonic Welding of Plastics

In this work, the impact of dyes and fillers on the process of heat generation during ultrasonic welding of plastics was studied, which made it possible to influence the weldability and quality of products. Experiments to weld samples of plastics with various concentrations of dyes and fillers were carried out. Based on the experimental data, it was established that the main parameters of the welding process and the properties of the polymer influenced weldability and performance indicators of the weld joint. The nature and the concentration of the dyes and fillers injected into the polymer to obtain certain characteristics and colors had an impact as well. Optimal concentrations that provided the best weldability, strength and quality of the weld products were obtained for fat-soluble dyes and organic pigments (0.1–1.5 g/kg) as well as disperse fillers and inorganic pigments (5–12 g/kg). Types of dyes and fillers and their optimal concentrations for fat-soluble dyes, organic pigments and disperse fillers were determined. Parameters of the process of ultrasonic welding of dyed and filled plastics were defined. It was established that welded products with the recommended optimal concentration and types of dyes and fillers showed the best weldability, increased strength and performance, and could be used longer under various climatic conditions.

Assessment of influence of disperse filler polarity on structure and water absorption of epoxy compositions

Introduction. Composite materials on the basis of epoxy resin find wide application as adhesives, coatings and structural materials whose properties it is possible to regulate by introduction of various additives including disperse fillers in the epoxy binder. Positively influencing properties of epoxy materials, the disperse fillers can reduce water resistance of the materials. This work is aimed at studying of influence of polar and nonpolar disperse fillers on structure and water absorption of the epoxy materials. Materials and methods. When obtaining composite materials, the following components were used: ED-20 epoxy resin (state standard GOST 10587-84), dibutylphthalate (state standard GOST 8728-88) plasticizer, polyethylenepolyamine (specification TU 2413-357-00203447-99) hardener, marshallite (state standard GOST 9077-82) and graphite (state standard GOST 17022-81) disperse fillers. The structure of samples was investigated by means of IR-spectroscopy method. Water absorption was determined in boiling water using the standard gravimetric method (state standard GOST 4650-2014 (ISO 62:2008)) and evaluated by sample mass variation within 120 days. Results. As a result of the conducted researches, the optimum content of the marshallite and graphite fillers in epoxy materials is established. When mass filler-to-binder ratio is equal to 15/85, water absorption of the materials is minimum. The IR-spectroscopy method showed that introduction of the marshallite polar filler in the epoxy binder promotes ordering of material structure due to formation of hydrogen bond between reactive groups of the filler and resin. Localizing in amorphous areas, particles of the graphite nonpolar filler lead to weakening of the hydrogen-bond system. Interaction of marshallite-filled samples with water is accomplished at the swelling mode, with equilibrium degree of swelling about 1 %. The mechanism of interaction of graphite-filled samples with water includes the alternating stages of dissolution and swelling, which are more expressed as compared with check samples. Conclusions. Water resistance of epoxy materials filled with disperse fillers is defined by a microstructure of the cured resin. Introduction of the marshallite polar filler in the epoxy binder leads to ordering of material structure that results in increasing of water absorption. Introduction of the graphite nonpolar filler in the epoxy binder leads to disordering of material structure that results in reducing of water absorption. Lower value of water absorption of graphite-filled epoxy material is connected with partial dissolution of the sample. Using nonpolar fillers is inexpedient for epoxy materials contacting with water.

Acid-basic surface properties of clay disperse fillers

The mineral composition, surface morphology, dispersion and specific surface of dispersed clay fillers of various chemical nature have been experimentally determined. As materials for research used clay mineral disperse fillers of various chemical and mineral composition: bentonite clay, kaolinite clay and diabase flour. Using the thermogravimetric (TG) analysis and the differential thermal analysis (DTA), the structure of the hydroxyl-hydrated surface layer of the filler surface has been studied. The amount and acidity of the surface active centers of clay fillers have been investigated using pK-metric and pH-metric methods. It was established that the mineral composition is the determining factor in the acid-base surface properties of clay fillers. The thickness of the hydroxyl-hydrated surface layer affects the acidity of the surface, at certain large sizes. It has been shown that clay fillers, which include montmorillonite as the dominant minerals, are characterized by higher acidity than the fillers that consist of kaolinite. In the mixed clay fillers, the acid-base properties of the surface depend on the chemical nature of the impurities and related minerals.