The main component of Haicheng talc is talc containing magnesium silicate, and its molecular formula is Mg3 [Si4O10] (OH) 2. Talc is a monoclinic system. The crystals are pseudo-hexagonal or diamond-shaped flakes, occasionally. It usually forms dense aggregates, leaf-like, radial, and fibrous aggregates. It is colorless and transparent or white, but appears light green, light yellow, light brown, or even light red due to a small amount of impurities; the cleavage surface is pearly luster. Hardness 1, specific gravity 2.7 ~ 2.8.

Application in coatings

(1) Cosmetic grade (HZ): used for various emollient powder, beauty powder, talcum powder, etc.

(2) Medicine-Food Grade (YS): Pharmaceutical tablets, powdered medicines (such as acaphenol powder), sugar-coated, gardenia powder and traditional Chinese medicine prescriptions, food additives, release agents, etc.

(3) Coating grade (TL): used for white constitution pigments and various water-based, oil-based, resin industrial coatings, primers, protective paints, etc.

(4) Paper grade (ZZ): used as filler for various paper and cardboard, wood pitch control agent.

(5) Plastic grade (SL): filler for plastics such as polypropylene, nylon, polyvinyl chloride, polyethylene, polystyrene and polyester.

(6) Rubber grade (AJ): used for rubber filler and anti-adhesive for rubber products.

(7) Cable grade (DL): used for cable rubber additive and cable isolator.

(8) Ceramic grade (TC): used in the manufacture of electric porcelain, radio porcelain, various industrial ceramics, architectural ceramics, daily ceramics and enamels.

(9) Waterproof material grade (FS): used for waterproof coil, waterproof coating, waterproof ointment, etc.

(10) Fine talcum powder: used in high-grade paints and coatings, plastics, cable rubber, cosmetics, coated paper coatings, textile lubricants, etc.

Effect of talc on micro-foamed polypropylene composites

Polypropylene (PP) / talc is widely used in automotive plastics due to its low cost and excellent mechanical properties. However, the material still has some shortcomings, such as high density, which is not conducive to the weight reduction of automobiles. The micro-foamed PP / talc powder material not only has the excellent properties of composite materials, but also has a reduced density and reduced quality.

1.Sample preparation

(1) PP / talc powder masterbatch

Co-rotating twin-screw extruder is used for extrusion granulation. Process parameters: screw rotation speed is 140r / min, feeding rate is 1.2-1.5r / min, and the temperature of the extrusion heating zone is 160-188 ° C.

(2) Micro-foamed PP / talc powder composite material

PP / talc powder masterbatch and foaming agent masterbatch are re-molded in an injection molding machine to prepare dumbbell-shaped splines that meet the test standards. The injection temperature was 175 ° C, the injection rate was 95%, and the injection pressure was 500 kPa.

2.Effect of talc on mechanical properties of micro-foamed composites

Specific strength is an important indicator for measuring the light weight and high strength of materials. It can be seen from Figure 2 that compared with pure PP material, the specific tensile strength of 5% of unfoamed PP material with a talc powder content decreases, the specific flexural strength increases, and the specific impact strength is basically unchanged. The mass fraction is further increased, and the specific tensile strength, specific bending strength, and specific impact strength of the material are all reduced.

Compared with pure PP material, the 5% talc powder PP material foamed, the specific tensile strength and specific bending strength increased, and the specific impact strength decreased slightly; continue to increase the talc powder mass fraction, foamed material The specific tensile strength, specific bending strength, and specific impact strength are all reduced. For the same material, the specific strength of the foamed material is lower than that of the unfoamed material.

According to the analysis of the specific strength of the material, after the material is foamed, the specific strength of the PP material with a talc powder content of 5% is high. Continue to increase the mass fraction of the talc powder, but decrease the specific strength of the material. Therefore, a small amount of talc powder filling is beneficial to improve the mechanical properties of the PP material after foaming.