Лако-красочные материалы — производство

The pigmentation of latices is different from that of most resin systems. In most systems, the resin (binder) is soluble in the liquid system. Pigment is dispersed in the solution which can be considered as a varnish (for inks). Resin can be absorbed onto the pigment. Partially soluble resins can coat the pigment, but there […]

Plasticisers have a dual role of ensuring good film formation under adverse conditions and imparting flexibility to the polymer. Typical plasticisers would be dibutyl phthalate and butyl benzyl phthalate. Both of these plasticisers along with dioctyl (ethyl hexyl) phthalate are currently suspected of acting as oestrogen mimics or endocrine disruptors. It is strongly advised that […]

Hydrophobic solvents decrease the MFFT most efficiently and increase the hardness of the coating due to improvements in film formation. They also penetrate into the shell and swell the polymer, increasing the viscosity dramatically. Coalescing solvents distribute throughout the three phases, water, polymer shell and polymer core, in differing volumes. Optimum film formation takes place […]

As a general rule, the higher the molecular weight, Tg or viscosity of the emulsion resin, then the higher the MFFT. Increasing the MFFT gives better physical and chemical properties, provided a coherent film is produced. Reducing the MFFT, reduces properties. In order to overcome this dilemma, solvents are used, which effectively reduce the viscosity […]

When used as a surface coating, an emulsion must form a coherent film. The evaporation of water during the final stages of drying causes stress in the film and a brittle film will crack under this stress. The temperature at which no stress cracking occurs is termed the minimum film forming temperature, MFFT or MFT. […]

Viscosity is the resistance to flow in a liquid and is measured in Poise. The study of viscosity is known as Rheology and this plays an important part in emulsion applications. In an ideal liquid, the rate of flow is proportional to the force inducing that flow. Mobile liquids approximate to this ideal behaviour and […]

It is important to reproduce the particle size of any latex and also to be able to measure it. Particle sizes generally encountered range from less than one micron for a fine latex, to about three microns for a coarse one. The distribution as well as the average size are both important. Particle size can […]

The non-volatile content (nvc), or solids as it commonly referred to, is a standard test method in resin chemistry, but there are a multitude of different methods depending upon the volatility of the solvent/water, etc., and thermal stability of the resin. Acrylamide containing resins slowly decompose on heating, and it is generally difficult, if not […]

It is necessary for latex to remain stable upon storage and exposure to tight. Storage stability can be tested by examining the condition (i. e. has separation occurred?, is there sedimentation?, etc.) and determining the viscosity and pH with respect to time. A shelf life of six months is essential. Accelerated tests can be used […]

Many latices are shear sensitive, particular to pumping, which may be essential in bulk handling facilities. There are many ways to determine this, but an easy method is to rub the latex between finger and thumb. If it is mechanically unstable it will rapidly ‘ball up’. A certain amount of experience is required for this […]