Because of its small modulus, the sensitivity of the gap is low, the impact strength is low, especially the impact strength at low temperature and high strain rate is low, and the application of engineering plastics is limited. Usually increase the toughness of PP is by adding elastomers, but the addition of elastomers tend to increase the PP toughness while other performance degradation, such as stiffness, hardness, etc., so people try to use inorganic filler to increase the mechanical properties of PP. Addition of inorganic fillers can improve the mechanical properties and thermodynamic properties of materials, including stiffness, creep resistance, heat distortion temperature, shrinkage, etc. On the other hand, the presence of inorganic fillers tends to reduce the tensile strength and toughness of the material The
    The effect of inorganic filler on the mechanical properties of the material depends mainly on the shape, particle size, particle aggregate size, particle surface characteristics and polymer matrix properties of inorganic rigid particles. The following Xiaobian will introduce the commonly used inorganic filler in the enhanced toughening polymer applications.
    Application of Calcium Carbonate in Strengthening Toughened Polypropylene
    Calcium carbonate products are divided into heavy calcium carbonate and light calcium carbonate.
    Heavy calcium carbonate referred to as heavy calcium, English referred to as GCC, is a mechanical method of direct crushing of natural calcite, limestone, white, shells and other systems. Because the sedimentation volume of heavy calcium carbonate is smaller than that of light calcium carbonate, it is called heavy calcium carbonate. At present, industrial production of heavy calcium carbonate is mainly two kinds of technology, one is dry, one is wet. Dry process compared with the wet can produce lower cost, wide range of products.
    Light calcium carbonate referred to as light calcium, also known as precipitation of calcium carbonate, referred to as PCC, is the limestone and other raw materials for the formation of lime as the main component of calcium oxide and carbon dioxide, plus water digestion lime to produce lime milk main components of calcium hydroxide, And then into the carbon dioxide carbonized lime milk to produce calcium carbonate precipitation, and finally by dehydration, drying and grinding and prepared. Or with sodium carbonate and calcium chloride for metathesis reaction to produce calcium carbonate precipitation, and then by dehydration, drying and crushing and prepared.
    Calcium carbonate is one of the first inorganic fillers to be used to fill reinforced toughened PP, and the use 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 decreases, the addition of light calcium carbonate can improve the impact strength and yield strength, and the stearic acid treated PCC better , With the titanate coupling agent treated calcium carbonate can significantly improve the impact strength of PP.
    With the advent of nanoscale calcium carbonate, it has been found that the use of nano-calcium carbonate can enhance toughening at the same time, and the toughening effect is better than micronic calcium carbonate. The results show that the mechanical properties of the composites are different. Cubic nano-calcium carbonate is beneficial to improve the impact properties of composite materials, and fibrous nano-calcium carbonate can significantly improve the tensile properties of materials, nano-calcium carbonate can make PP fine crystal refinement, and can promote the β-type generate.
    Application of Glass Beads in Strengthening Toughened Polypropylene
    Glass beads are a new type of silicate material, both solid and hollow. Usually the glass beads with particle size of 0.5-5mm are called fine beads, and the beads are smaller than 0.4mm. The beads are different according to different sources. Fly ash glass beads are extracted from fly ash Out of a light micro-spherical material, its main component is silica, also contains a variety of metal oxides, fly ash glass beads have high temperature, thermal conductivity, etc., for filling plastic can not only increase Material wear resistance, compression resistance, flame retardant and other properties, and its special spherical surface can also improve the processing of fluid mobility, in addition, its surface gloss is good, can increase the surface gloss products to reduce the surface of the dirt adsorption.
    Glass beads (GB) are widely used to enhance the toughening of PP. The results show that the tensile modulus, flexural strength and modulus of the PP / GB composites increase linearly with the increase of the amount of GB, and the yield strength decreases slightly with the increase of the amount of GB. The impact strength of single and twin screw extruded materials is improved and increased with the increase of GB dosage in a certain range, and the impact strength of single screw extruded material is slightly increased Higher than that of twin screw extruded materials, GB particle size has a great influence on the toughness of PP / GB composites.
    Application of Silicate Minerals in Strengthening Toughened Polypropylene
    At present, the application and research of the most extensive silicate minerals are talcum powder, montmorillonite, wollastonite, etc., of which attapulgite, zeolite is also more attention.
    Talc and montmorillonite (MMT) are layered silicate minerals. Talc powder is a lamellar structure of magnesium silicate minerals, usually the finer particle size of the finer dispersion effect is better, can improve the material heat distortion temperature and surface finish; MMT layer spacing is large, often using intercalation method to prepare PP composite , MMT in the PP matrix can form a good intercalation structure, thereby enhancing the impact resistance of PP and dimensional stability.
    Attapulgite (ATP) is a layered silicate. ATP is a natural one-dimensional nanometer material silicate mineral, the basic structural unit for the needle or short fibrous single crystal, ATP can be in the micron-filled and nano-enhanced two levels of polypropylene and composite, improve the mechanical properties of the material The This new type of clay staple fiber to overcome the general glass fiber reinforced resin flow is poor, rough appearance, serious wear and tear on the processing equipment and other shortcomings, which has a high development value.
    Wollastonite is a single-chain silicate mineral, usually flaky, radial or fibrous aggregates. The results show that wollastonite filled plastic can not only improve its mechanical properties, but also can replace the use of glass fiber to reduce the cost, but with the increase in the amount of filler, the hardness of the composite material, wear more serious processing equipment.
    Zeolite is a silicate mineral. It has a rich pore structure, can be adsorbed or loaded by the function of particles, the preparation of more powerful polypropylene composite materials, improve the added value of the product. Therefore, the development of PP / zeolite functional composite materials has great potential, become the current research and focus of the hot spots.
    Application of Titanium Dioxide in Strengthening Toughened Polypropylene
    Titanium dioxide chemical composition of titanium dioxide, rutile and anatase type, rutile type is the most stable crystalline form, compact structure, hardness, weatherability and anti-chalking better than anatase, the atmosphere of the Chemical substances stable, insoluble in water, good heat resistance. Titanium dioxide can not only improve the whiteness of the product, but also reduce the damage of ultraviolet light, can improve the photo-aging properties of polypropylene, but also improve the rigidity of products, hardness and wear resistance, but its compatibility with the poor , It is necessary to modify its capacity.
    to sum up
    In recent years, polypropylene / inorganic rigid particle composites are increasingly popular, for its comprehensive performance and further enhance the application of the field opened up a new way. 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. The microstructure model of polypropylene inorganic rigid particle composites is established, and the interfacial molecules Design, through the inorganic rigid particles and the surface of the polymer physical and chemical modification, the interface compatibilizer synthesis, to determine the appropriate processing technology to achieve the design of the interface molecular structure, in order to achieve effective regulation of material performance is the direction can be The With the development of science and technology, polypropylene inorganic rigid particles composite material preparation method will be further improved, the performance is also improved, high rigidity, high toughness of polypropylene inorganic rigid composite materials of industrial applications, will be China's general The engineering of plastics makes an important contribution.