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Types of commonly used fillers
- Aug 17, 2018 -

1. calcium carbonate filler

(1) ordinary calcium carbonate (Bai E): white crystal or powder, with a specific gravity of 2.70-2.95, soluble in acid and insoluble in water. Calcium bicarbonate is excused in water saturated with carbon dioxide, and is heated to 825 C to decompose into calcium oxide and carbon dioxide. Naturally occurring calcium carbonate minerals include limestone, calcite, white extinction, field stone and so on. They are called ordinary calcium carbonate after being ground into powder. They are different from dry and wet grinding in that the particle size of dry grinder is between 1.5 and 44 microns, the particle size of dry grinder is greater than 20 microns and that of wet grinder is less than 20 microns.

(2) precipitation of calcium carbonate: carbon dioxide into lime water or sodium carbonate solution and lime water precipitation of the formation of powdered calcium carbonate, generally divided into:

Light precipitated calcium carbonate: specific gravity 2.50-2.60

Heavy precipitated calcium carbonate: specific gravity 2.70-2.80

Precipitated calcium carbonate particle size is 1.0-16 micron, specific surface area is 5-25 m 2/g, refractive index is 1.49, PH value is about 10, insoluble in water and alcohol, when acid emits carbon dioxide; slightly hygroscopic.

(3) Active Lightweight Calcium Carbonate (Brilliant White): This is a kind of light calcium carbonate adsorbed on the surface of a layer of fatty acid soap particles, tasteless and odorless white powder, specific gravity 1.99-2.01. Water content below 0.5%, stearic acid content 2-5%, particle size less than 0.1 micron, specific surface area 25-28 m 2/g, refractive index 1.49. It is insoluble in water and alcohol, and releases carbon dioxide when it is decomposed by acid. There is no chemical change in the air, only slightly hygroscopic. The activity is slightly larger than ordinary calcium carbonate.

2. carbon black filler

These kinds of fillers include all kinds of carbon black. Carbon black is produced by partial combustion or thermal decomposition of liquid or gaseous hydrocarbons under insufficient air. The element composition of carbon black is mainly carbon, containing only a few hydrogen and oxygen. It is a black powder with "quasi-graphite crystal" structure and colloid size range.

Carbon black can be divided into different grades because of different production processes, but there are two commonly used in the plastic industry:

(1) natural gas trough Black: black powder material, rough surface, easy to absorb moisture in the air. Average particle size 23-30 nm (easy mixing tank black 29-35 bright micron, difficult mixing tank black 23-26 nm), specific surface area 130-160 m 2/g.

(2) Mixed tank black: This is a kind of carbon black made from coal tar processed oil (anthracene oil, naphthalene oil, etc.) gasified and mixed with natural gas as raw materials.

The so-called "structure" of carbon black refers to the tendency of carbon black to aggregate in series. This "structure" plays an important role in the rheological properties of carbon black-polymer system. "High structure" carbon black promotes the extrusion of polymer with high viscosity, high elastic modulus, low flow rate and smooth swelling. The addition of carbon black into the polymer not only protects photodegradation and thermal oxidation, but also improves the rigidity of plastic products.

3. cellulose filler

(1) shredded paper: it can be filled with kraft paper, white paper and coloured paper. Generally, paper is soaked in resin, dried and sliced, and then pressed into sheet material.

(2) wood flour: widely used in thermosetting resins, with high impact strength, small shrinkage, good electrical properties and low cost. Wood powder particles are uniform in size, and large particles such as wood chips and bark should be removed.

(3) Cotton chips: Cotton chips are obtained by cutting cotton cloth or cotton spinning purification. The impact resistance of plastic products filled with cotton chips is improved and the volume is large.

(4) alpha cellulose: alpha cellulose is a colorless cellulose, which is the product of alkali treatment of wood pulp. It is mainly used in the formulation of light urea formaldehyde and melamine formaldehyde resin. The products with alpha-cellulose as filler have better impact strength than those with wood flour as filler, higher hardness, no influence on specific gravity, and lower molding shrinkage.

(5) peanut shell: peanut shell is a very cheap and abundant source of high phenol content. Peanut shell powder can appropriately improve the performance of HDPE, PS and PP and reduce the cost. The surface of peanut hull powder is generally non-polar. Its water absorbency is smaller than that of wood flour.

(6) Walnut shell: Walnut powder is the waste produced in the process of walnut, because it contains a lot of wood resin and keratinous wax, so it is not absorbent.