Лако-красочные материалы — производство

The problem of extrapolating down to molecular dimensions from macro­scopic experience can be seen in two simple cases.6 First, consider the macro­scopic task of sieving pebbles in the garden, as shown in Fig. 3.4(a). If the mesh size is 20mm, then the 10mm pebbles can easily be shaken through the holes. Each pebble shows no […]

The first fallacy, that vacuum causes adhesion, was understandable because of Galileo’s influential statement above and also because vacuum was invented by Newton’s contemporary, Galileo’s pupil and secretary Torricelli, who built the original mercury barometer around the time of Newton’s birth, generating the first artificial vacuum in the closed tube above the mercury column. The […]

I found the place in which they touched to become absolutely transparent, as if they had there been one continued piece of glass Isaac Newton,1 Opticks, p. 194 The ideas that Newton developed about the sticking together of bodies were quite advanced compared with those of Galileo who had died just a few years earlier. […]

Consider a definition of molecular adhesion which allows it to be distin­guished from all the other known forms of attractions between bodies: molecular adhesion is the force experienced when bodies make contact at the molecular level, with gaps near molecular dimensions. This definition raises a number of questions which will be addressed in the following […]

ATTRACTIONS A simple way to distinguish molecular adhesion from electrostatic, gravita­tional, or liquid bridge adhesion is to observe the range of action of the force. Newton knew of the long-range action of those forces and was tantalized by the much shorter range of molecular adhesion. The two most easily distinguishable forces of attraction are suction […]

Consider now an experiment which demonstrates molecular adhesion simply and unequivocally. Take a sample of very fine, pure solid powder, say 4 g of 0.2 pm diameter grains of titanium dioxide. This powder can be poured into a hard steel pelleting die, as shown in Fig. 2.9(a). Coulombic forces can be prevented by the presence […]

Electrons (very small sub-atomic particles) are therefore the fundamental cause of molecular attractions. These were the first elementary particles to bediscovered, identified, and measured, for example in the classic experiments of J. J. Thomson more than a century ago. It was evident from those studies that an electron is much smaller than an atom, almost […]

Yet another confusing adhesive influence is that of electricity and magnet­ism. Adhesion of bodies as a result of electrical charging was known to the Greeks. Rubbing glass or amber with cloth would make the material attract smallpieces of dust or paper. A particularly eerie sensation is when your hair stands up as a result of […]

In addition to friction, which is often confused with adhesion, there are several other phenomena which give attractions between bodies. These phenom­ena can therefore mix up the issues of molecular adhesion. As Newton wrote: “the attractions of Gravity, Magnetism and Electricity reach to very sensible distances, and so have been observed by vulgar Eyes, and […]

Many phenomena lead us to believe that molecular adhesion exists. We recognize that, just as a small solid particle sticks to a surface, so a droplet of water adheres to glass, and we realize, as Young and Laplace did in the early 1800s, that this can be explained by attractions between the water molecules and […]