Search results

Modifications of poly(vinyl alcohol) (PVA) can improve the properties and performance of poly(vinyl acetate) (PVAc) emulsions stabilized with these modified colloids. Water resistance and toughness of the emulsions as wood adhesives can be achieved through chemical reactions of the hydroxy groups of the colloid with various modifiers. The chemical changes can be carried out either in the preparation of PVA through hydrolysis of copolymers of vinyl acetate and other monomers, or by the reaction of modifiers with PVA aqueous solutions. The modified PVAc emulsions show better properties than those of the conventional emulsions in performance tests and applications. The modified colloids are becoming increasingly used in the manufacture of PVAc emulsions in the adhesive industry, because of their advantages over emulsions made using conventional (unmodified) PVA. The trend of current research is to introduce more functionality into the colloid, so that the traditional protective colloids can be modified to function as crosslinkers and chain transfer agents.

THE phenomenon of curling of systems comprising colloids such as cellulose nitrate, deposited on non‐rigid substrates such as paper or fabric, has been known for nearly a century. There is, however, no indication in the literature of any attempt to correlate this behaviour with, for example, the phenomenon of the bending of plates. The present investigation presents certain analogies, which enable us to interpret much of the behaviour of these colloid systems on substrates.

The abbreviated review touches upon the colloid science detail in multiple industrial usages. The inter‐relation of the paint chemist, the paper chemist and the textile chemist, or engineers in those fields, as colloid scientists is stressed. The commonality of the systems containing pigment/ filler solids, binders and rheology controllers (albeit in different ratios) is noted. The challenges offered on these systems minor constituents (surfactants, oligomers and salts) are approximated in simple models studied by the academic colloid scientists, but pose real problems to the formulators of commercial systems. The final statements call for more interaction and mutual learning from these varied industrial systems' researchers.

The inhibition of corrosion of B26S aluminium by various colloidal substances in aqueous sodium hydroxide has been studied. The extent of corrosion decreased with increase in the concentration of the inhibition. At an inhibition concentration of 0.5% and above. The efficiency of the colloids in decimolar sodium hydroxide increased in the order: gelatin < dextrin < glue < agar agar < acacia < tragacanth (86%). The efficiency decreased with increase in the concentration of alkali, the P.I. at an inhibitor concentration of 1.5% in 1M sodium hydroxide being, glue (23%), gelatin (39%), dextrin (47%), agar agar (64%), acacia (71%) and tragacanth (86%). The inhibition appears to be due to the absorption of the inhibitor on the aluminium surface. An increase in temperature also decreased the extent of inhibition. The aver‐age energy of activation for corrosion of B26S aluminium in 0.1M sodium hydroxide appeared to be 12.5 KCal, the value in the presence of the inhibitor being somewhat higher.

This paper aims to propose a simple method for stabilizing silica-coated silver iodide (AgI/SiO₂) core-shell particles, of which a colloid solution functions as an X-ray contrast agent.

A colloid solution of AgI nanoparticles was prepared by mixing silver perchlorate and potassium iodide in water. The AgI/SiO₂ nanoparticles were fabricated by a sol-gel method using NaOH, H₂O and tetraethylorthosilicate in ethanol in the presence of AgI nanoparticles surface-modified with 3-mercaptopropyltrimethoxysilane.

The silica shells of AgI/SiO₂ particles were dissolved near the AgI nanoparticle surface, when they were washed by a process composed of centrifugation, removal of supernatant with decantation, addition of water as a washing solution and a shake with a vortex mixer. In contrast, the shells were not damaged by using ethanol as the washing solution, i.e. ethanol-washing. An X-ray photoelectron spectroscopy spectrum of the silica was changed after the ethanol-washing, which indicated that the ethanol-washing had an effect on the chemical bonds in silica. The effect also acted on the silica shells of AgI/SiO₂ particles, which did not damage the core-shell structure, i.e. controlled the dissolution of shell.

The paper demonstrates that the ethanol-washing is quite useful for stabilizing the core-shell structure composed of the silica shells.

No one acquainted with the facts that gave rise to the packing‐house scandals of the year 1906 believed that the belated promises of reform then made by certain American meat packers were to be relied upon. Many of these people were threatened with a serious loss of trade, and it was evidently their best policy at the time not too strongly to oppose legislation that was apparently devised to permanently better the conditions in the slaughtering establishments and packing‐houses.