Introduction to several kinds of inorganic fillers commonly used in plastics products

Glass fibre

Glass fiber is often used in engineering plastics filler, its main components are silica, and other derived metal oxides, the current international mainstream production process for the pool kiln wire drawing method; According to the amount of alkali content in glass, it can be divided into alkali-free glass fiber, medium alkali glass fiber and high alkali glass fiber; The glass fiber commonly used in engineering plastics is mainly alkali free cut glass fiber and non-twist long glass fiber. After adding glass fiber, engineering plastics will have the following changes.

Advantages:

1, enhance rigidity and hardness, the increase of glass fiber can improve the strength and rigidity of plastics;
2, improve the heat resistance and thermal deformation temperature, taking nylon as an example, increase the nylon glass fiber, thermal deformation temperature increased at least 30 degrees above, the general glass fiber reinforced nylon temperature can reach 220 degrees above;
3, improve dimensional stability, reduce shrinkage;
4, reduce warping deformation;
5, reduce creep;
6, reduce moisture absorption.

Cons:

When the modulus of the product increases, the toughness will decrease. It has an adverse effect on the flame retardant performance, because the candle wick effect will interfere with the flame retardant system and affect the flame retardant effect; The exposure of glass fiber will reduce the gloss of the surface of plastic products.

The length of the glass fiber directly affects the brittleness of the material; If the glass fiber is not treated well, the staple fiber will reduce the impact strength; Good treatment of the filament will increase the impact strength. In order to make the material brittle will not decrease greatly, it is necessary to choose a certain length of glass fiber.

The fiber content of the product is also a key issue. The industry generally adopts 15%, 25%, 30%, 50% and other integer content, and the specific need to determine the content of glass fiber according to the use of the product.

In order to obtain good mechanical properties and surface effects, the diameter and length of the glass fiber selection and subsequent modification of the surface treatment, glass fiber content, etc., are crucial!

Calcium carbonate

Calcium carbonate products are divided into heavy calcium carbonate and light calcium carbonate. Heavy calcium carbonate is referred to as heavy calcium, and the English abbreviation is GCC, which is made by directly crushing natural calcite, limestone, white and shell by mechanical method. Because the sedimentation volume of heavy calcium carbonate is smaller than that of light calcium carbonate, it is called heavy calcium carbonate. At present, there are two main processes for industrial production of heavy calcium carbonate, one is dry method and the other is wet method. The dry process can produce products at lower cost and with a wide range of uses compared to the wet process.

Light calcium carbonate is referred to as light calcium, also known as precipitated calcium carbonate, English abbreviation PCC, is the raw materials such as limestone forging to produce lime mainly composed of calcium oxide and carbon dioxide, and then add water to digest lime to produce lime milk, the main component is calcium hydroxide, and then through carbon dioxide, carbonized lime milk to produce calcium carbonate precipitation, and finally by dehydration, drying and crushing. Or, calcium carbonate is precipitated by the double decomposition reaction of sodium carbonate and calcium chloride, and then prepared by dehydration, drying and grinding.

Calcium carbonate is one of the earliest inorganic fillers used to fill PP, and the application of micron calcium carbonate has been in a dominant position. The research shows that the addition of calcium carbonate can increase the impact strength of PP, but reduce the tensile strength. The addition of light calcium carbonate can improve the impact strength and yield strength at the same time, and the effect of the PCC treated with stearic acid is better, and the impact strength of the calcium carbonate treated with titanate coupling agent can significantly improve the impact strength of PP.

With the appearance of nanometer calcium carbonate, it has been found that nanometer calcium carbonate can strengthen and toughen at the same time, and the toughening effect is better than micron calcium carbonate. The results show that the mechanical properties of nano-calcium carbonate composites are also very different with different morphology. Cuboidal nano-calcium carbonate is beneficial to improve the impact property of the composite, while fibrous nano-calcium carbonate can significantly improve the tensile property of the composite, nano-calcium carbonate can significantly refine PP spherulites, and promote the formation of β crystals.

Glass bead

Glass microbeads are a new type of silicate material, including solid and hollow. Glass beads with a particle size of 0.5-5mm are usually called fine beads, and those with a particle size below 0.4mm are called microbeads; There are a variety of microbeads according to different sources, fly ash glass microbeads are extracted from fly ash a kind of lightweight micro-spherical substance, its main component is silica, but also contains a variety of metal oxides, fly ash glass microbeads have high temperature resistance, low thermal conductivity and other advantages, used to fill plastics can not only increase the material wear resistance, pressure resistance, flame retardant and other properties, but also, Its special spherical surface can also improve the processing flow of the material, in addition, its surface gloss is good, can increase the surface gloss of the product, reduce the surface dirt adsorption.

Glass microbeads are widely used to strengthen and toughen PP. The results show that the tensile modulus, bending strength and modulus of PP/ glass microbead composites increased linearly with the increase of glass microbead content, while the yield strength decreased slightly. The fracture strain increases at low content and then decreases rapidly. The impact strength of both single and twin-screw extruded materials is increased, and increases with the increase of glass microbeads in a certain range. The impact strength of single screw extruded materials is slightly higher than that of twin-screw extruded materials.

Silicate mineral

At present, the most widely used and studied silicate minerals are talc powder, montmorillonite, wollastonite, etc., among which attapulgite and zeolite have also received more attention.

Talc and montmorillonite (MMT) are stratified silicate minerals. Talc powder is a magnesium silicate salt mineral with flake structure. Generally, the finer the particle size, the better the dispersion effect, which can improve the thermal deformation temperature and surface finish of the material. The intercalation method is often used to prepare PP composites with large spacing between MMT layers. MMT can form a good intercalation structure in PP matrix, thus improving the impact resistance and dimensional stability of PP.

Attapulgite (ATP) is a chain stratified silicate. ATP is a kind of natural one-dimensional nanomaterial silicate mineral, its basic structural unit is needle or short fibrous single crystal, ATP can be combined with polypropylene at the two levels of micron filling and nano reinforcement, to improve the mechanical properties of the material. This new type of clay short fiber overcomes the disadvantages of ordinary glass fiber reinforced resin such as poor fluidity, rough appearance and serious wear to processing equipment, so it has high development value.

Wollastonite is a single chain silicate mineral, usually in the form of flake, radial or fibrous aggregates. The research shows that wollastonite filled plastics can not only improve its mechanical properties, but also replace glass fiber and reduce the cost, but with the increase of the filling amount, the hardness of the composite material becomes larger, and the wear of the processing equipment is more serious.

Zeolite is a frame silicate mineral. It has a rich channel structure, which can prepare functional polypropylene composite materials by adsorption or loading functional particles, and improve the added value of products. Therefore, the development of PP/ zeolite functional composite materials has great potential, and has become the focus of current research and attention.

Titanium dioxide

The chemical composition of titanium dioxide is titanium dioxide, according to the crystal form, there are rutile type and anatase type, rutile type is the most stable crystal form, dense structure, hardness, weather resistance and resistance to pulverization is better than anatase type, stable for various chemicals in the atmosphere, insoluble in water, good heat resistance. After titanium dioxide is added, it can not only improve the whiteness of the product, but also reduce the damage of ultraviolet light, improve the photoaging performance of polypropylene, but also improve the rigidity, hardness and wear resistance of the product, but it is poor compatibility with crystalline materials, such as PP, PA, etc., it is necessary to modify the capacity.