Polypropylene is limited in its application as an engineering plastic because of its small modulus, strong notch sensitivity, and low impact strength, especially at low temperatures and high strain rates. Generally, the toughness of PP is increased by adding an elastomer, but the addition of the elastomer tends to increase the toughness of the PP while other properties are lowered, such as rigidity and hardness. Therefore, an inorganic filler is tried to increase the mechanical properties of the PP. The addition of inorganic fillers can improve the mechanical properties and thermodynamic properties of the material, including stiffness, creep resistance, heat distortion temperature, shrinkage, etc., but on the other hand, the presence of inorganic fillers tends to reduce the tensile strength and toughness of the material. .
The influence of inorganic fillers on the mechanical properties of the materials mainly depends on the shape, particle size, particle agglomerate size, particle surface characteristics and polymer matrix properties of the inorganic rigid particles. The following small series will introduce the application of commonly used inorganic fillers in reinforced and toughened polymers.
Application of calcium carbonate in reinforced and toughened polypropylene
Calcium carbonate products are classified into heavy calcium carbonate and light calcium carbonate.
Heavy calcium carbonate is referred to as heavy calcium, which is abbreviated as GCC in English . It is made by mechanically pulverizing natural calcite, limestone, white toe and shell. Since the sedimentation volume of the heavy calcium carbonate is smaller than the sedimentation volume of the 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 produces a lower cost, versatile product than the wet process.
Light calcium carbonate is abbreviated as light calcium, also known as precipitated calcium carbonate. It is abbreviated as PCC . It is used to calcinate raw materials such as limestone to form lime. The main components are calcium oxide and carbon dioxide, and water is added to digest lime to form lime milk. The main component is calcium hydroxide. Then, carbon dioxide carbonized lime milk is introduced to form a calcium carbonate precipitate, which is finally obtained by dehydration, drying and pulverization. Alternatively, the metathesis reaction of sodium carbonate and calcium chloride is first carried out to form a calcium carbonate precipitate, which is then obtained by dehydration, drying and pulverization.
Calcium carbonate is one of the first inorganic fillers to be used to fill and strengthen toughened PP, and the application of micron-sized calcium carbonate has been dominant. Studies have shown that the addition of calcium carbonate can increase the impact strength of PP, but the tensile strength is reduced, the addition of light calcium carbonate can simultaneously improve the impact strength and yield strength, and the PCC treated with stearic acid is better. The calcium carbonate treated with the titanate coupling agent can significantly increase the impact strength of PP.
With the advent of nano-scale calcium carbonate, it has been found that nano-calcium carbonate can simultaneously enhance toughening and the toughening effect is better than that of micron-sized calcium carbonate. Studies have shown that the morphology of nano-CaCO3 is different, and the mechanical properties of the composites are also very different. The cubic nanometer calcium carbonate is beneficial to improve the impact properties of the composite material, while the fibrous nano calcium carbonate can significantly improve the tensile properties of the material. The nano calcium carbonate can significantly refine the PP spherulites and promote the β crystal form. generate.
Application of Glass Beads in Strengthening Toughened Polypropylene
Glass beads are a new type of silicate material, both solid and hollow. Generally, glass beads with a particle size of 0.5-5 mm are referred to as fine beads, and beads having a particle diameter of 0.4 mm or less are called microbeads; microbeads are various according to different sources, and fly ash glass beads are extracted from fly ash. A light micro-spherical material whose main component is silica and also contains various metal oxides. The fly ash glass microbeads have the advantages of high temperature resistance and small thermal conductivity, and can not only be used for filling plastics. The material's wear resistance, pressure resistance, flame retardant and other properties, and its special spherical surface can also improve the processing fluidity of the material. In addition, its surface gloss is good, which can increase the surface gloss of the product and reduce the dirt adsorption on the surface.
Glass microbeads (GB) are widely used for the reinforcement and toughening of PP. The results show that with the increase of GB dosage, the tensile modulus, flexural strength and modulus of single/double-screw extruded PP/GB composites increase linearly, while the yield strength decreases slightly. The low content increases and then decreases rapidly. The impact strength of the single and twin-screw extruded materials is improved, and increases with the increase of GB dosage within a certain range, and the impact strength of the single-screw extruded material is slightly Higher than twin-screw extrusion materials, GB particle size has a greater impact on the toughness of PP/GB composites.
Application of silicate minerals in reinforced and toughened polypropylene
At present, the most widely used silicate minerals are talc, montmorillonite, wollastonite, etc. Among them, attapulgite and zeolite have received much attention.
Talc and montmorillonite (MMT) are layered silicate minerals. The talc powder is a magnesium silicate mineral with a sheet structure. Generally, the finer the particle size, the better the dispersion effect, and the heat distortion temperature and surface finish of the material can be improved; the spacing of the MMT layer is large, and the PP composite material is often prepared by the intercalation method. MMT can form a good intercalation structure in the PP matrix, thereby improving the impact resistance and dimensional stability of PP.
Attapulgite (ATP) is a chain layered silicate. ATP is a natural one-dimensional nanomaterial silicate mineral whose basic structural unit is a needle-like or short-fiber single crystal. ATP can be compounded with polypropylene at two levels of micro-filling and nano-enhancement to improve the mechanical properties of the material. . The novel clay short fiber overcomes the shortcomings of the general glass fiber reinforced resin, such as poor fluidity, rough appearance, and severe wear on processing equipment, and thus has high development value.
Wollastonite is a single-chain silicate mineral, usually in the form of flakes, radial or fibrous aggregates. Studies have shown that wollastonite filled plastic can not only improve its mechanical properties, but also can replace the use of glass fiber, reducing costs, but as the filling amount increases, the hardness of the composite material becomes larger, and the wear of processing equipment is more serious.
Zeolites are framework silicate minerals. It has a rich pore structure, which can prepare functional polypropylene composites by adsorbing or loading functional particles, and increase the added value of the products. Therefore, the development of PP/zeolite functional composites has great potential and has become a hot spot of current research and attention.
Application of titanium dioxide in reinforced and toughened polypropylene
The chemical composition of titanium dioxide is titanium dioxide, rutile and anatase. The rutile is the most stable crystalline form. The structure is compact, hardness, weather resistance and anti-dusting are better than those of the anatase. The chemical substance is stable, insoluble in water, and has good heat resistance. Titanium dioxide can not only improve the whiteness of the product, but also reduce the damage of ultraviolet rays, improve the photoaging performance of polypropylene, and improve the rigidity, hardness and wear resistance of the product, but its compatibility with PP is poor. It is necessary to increase the capacity and modify it.
to sum up
In recent years, polypropylene/inorganic rigid particle composites have become more and more popular, opening up new avenues for further improvement of their comprehensive performance and expansion of application fields. At present, how to effectively promote the dispersion of inorganic rigid particles in the composite system and the combination of inorganic rigid particles and matrix is ​​still the focus of modification, and the microstructure model of polypropylene inorganic rigid particle composite is established, and the interface molecule is applied to the composite system. Design, through the physical and chemical modification of inorganic rigid particles and polymer surface, the synthesis of interfacial compatibilizer, determine the appropriate processing technology, realize the designed interface molecular structure, so that the effective adjustment of material properties is the direction that can be carried out. . With the development of science and technology, the preparation method of polypropylene inorganic rigid particle composite material will be further improved and the performance will be improved. The industrial application of high rigidity and high toughness polypropylene inorganic rigid particle composite material will be universal in China. The engineering of plastics makes an important contribution.
Stainless Steel Filter,Hydraulic Oil Filter,Gas Oil Filter,Steel Hydraulic Filters
Xinxiang Xin Ming De Machinery Co., Ltd. , https://www.xmdsieve.com