Most household utensils are dominated by plastic and fiber-based materials.Its flexible, lightweight and even easy-to-modify shape makes plastic and fiber currently one of the tools that are widely used by all groups of people.Although indeed in the long term, plastic furniture must be immediately reduced because it is based on polymers that are difficult to be decomposed by the natural environment.The growing use of polymers in the form of plastics and fibers has also encouraged the world to improvise products, one of which is giving color to polymers so that they have a more attractive appearance.In addition to art and design needs, coloring on plastic and fiber goods is also used for primary aspects such as markers, symbols and other uses involving color cues.So, how is the process for plastic and fiber-based materials to be colored?Since the first quarter of 2020, the corona virus outbreak has made a big shift in human life on earth.Starting from physical needs such as vitamin supplements, preventive sanitizers to the use of masks which were originally preventive, now seems to be a new safe culture.Well, one object, namely a mask, is an example of the use of polymers that have been improved into the form of fibers.Currently, masks have become items that almost play a role like rice, needed by the community all the time.Back to the concept of polymer modification, namely giving color to polymer-based materials such as fibers and plastics.One of the concepts taught in polymer chemistry is polymer rheology, which is the explanation that polymers are materials whose deformation or melt flow properties can be observed under given conditions.One of the important aspects in studying polymers is the relative molecular mass (BM).Starting from the flow properties, melting point, tensile strength of the polymer is closely related to its molecular weight (BM).Well, from this BM, the polymer concept has been widely developed in everyday life and one of them is coloring on tools based on fiber or plastic.Plastics and fibers are materials made from polymer base materials ranging from polypropylene (PP), poly ethylene (PE), poly styrene (PS) and so on.Then how do we suddenly get colored plastic stuff?For example, if the fan we bought is already blue, the cupboard is red, the mask is green?How can coloring be done?From here the concept of rheology is needed.Currently, many colorant companies are developing colorant products for plastics using technology with the concept of polymer rheology.In general, dyes chemicals (pigments) are produced by certain industries and marketed in powder form and then developed in the colorant industry for both plastics and other base materials.In the polymer colorant industry, pigment powder obtained from the color seed industry will be developed into a plastic-based dye product, namely by adding a suitable carrier to the polymer which will be colored and further processed using certain machines to form a solid colorant or colorant paste.The use of this career is part of improving every colorant company because it greatly affects the material to be colored.Then how is the coloring process on plastic or fiber equipment such as bottles, pipes, parts of cupboards and masks?Most plastic industries that produce packaging items use polymer injection molding technology, which is a technology with the principle of melting and molding polymers into the desired shape.Initially, the polymer used was polymer seeds in the form of masterbatch or powder.Then in the process, the polymer seeds, which will be packaged or in other shapes, will be included in injection molding along with the colorant.Well, this is where the concept of polymer rheology is needed, especially the melting point of the polymer used and the carrier of the colorant.When the polymer is melted by the molding machine, it is hoped that the colorant carrier will also melt, so that in its molten form, the polymer will be colored by the pigment bound by the carrier.In the next process, the molten polymer that has been colored by the pigment will automatically be printed according to the set shape.So far, it can be concluded that it is very important to know the polymer rheology which is closely related to the melting point, flow rate and other properties.