TABLE OF CONTENTS
2.0 Mass pigmentation
188.8.131.52 Features of a pigment
184.108.40.206 Aplication of pigments.
3.2 Mass pigmentation application characteristics.
3.0 Textile spin finishers and finishes
4.4 Classification of finishes
4.5 Pre-treatment processes
4.6 Important finishes
This is a research assignment on mass pigmentation, being a part of Textile raw materials MIT 221.
2.0 MASS PIGMENTATION
Mass pigmentation is the incorporation of the pigment in a molten polymer mass during processing into a compound or molten batch or when ...view middle of the document...
2 MASS PIGMENTATION APPLICATION CHARACTERISTICS
The term mass pigmentation encompasses al the processes by which metal flakes are combed with polymer to ultimately form a finished article. Of these methods injection moulding is the most technically challenging because it has the most variables requiring control. They include;
Colour in the context of pigments generally means brilliance/brightness. It broadly corresponds to cleanliness in organic pigments. Metallic colour is influenced by the surface finish of the pifgment,its tint strength and its concentration.
The specific case of alluminium pigments, improved colour equates to increased whiteness. These properties are in turn dependant on the particle size distribution and the surface brightness of the flake.
The process of dispersion starts with a combination of metal flakes and polymer in dry state. Masterbatch preblending is used here. Masterbatch in this context covers the metal flake pigment damped or carried by any suitable organic material such as a plasticizer or a polymer.
A short period of dry tumbling erg in a double can blender should be sufficient for most commonly available alluminium pigment masterbatches. High speed powder blenders are not recommended for two reasons:
a) There is a danger that the high shear will break down the masterbatch, releasing single flakes with a consequent danger of explosion.
b) The same high shear can bend or break the flakes leading to a loss of metallic brightness.
Most metal flake pigments are very resistant to heat. The flakes themselves remain stable well above the highest polymer processing temperatures. In practice, the maximum processing temperature is often dictated by the polymer.
iii. Opacity and tint strength
Opacity or hiding power is a function of flake diameter, thickness and density of the metal. At constant thickness and density, opacity is roughly proportional to the inverse square of the diameter. The smaller the diameter or thickness, the higher the total surface area. With more surface area available to obliterate the substrate, opacity is higher.
Tint strength refers to the ability of a metal pigment to modify the colour depth of a colourant with which it is incorporated.
Thus a deep blue metallic effect will become paler if further metal flake pigment is added to the formulation.
A finer particle size flake will create a greater colour shift than the same weight of a courser flake. Increasing flake thickness i.e. reducing the aspect ratio is practiced to improve degradation resistance. It is at the expense of opacity.
Folded and bent flakes have an ambivalent effect on opacity. Folded and bent flakes have reduced effective surface area.
Alternatively if the focus becomes thinned and breaks, surface area is increased. This is however accompanied by loss of brightness due to both increased concentration of fine particles and the disruption of uniform orientation...