Calcium carbonate is an inorganic filler widely used in polymer composites. Adding inorganic fillers such as calcium carbonate to rubber and plastic products can improve the heat resistance, wear resistance, dimensional stability and rigidity of the products, and reduce the cost of the products, but the surface characteristics of the inorganic fillers are hydrophilic and oleophobic. The compatibility with the polymer material is poor, so irregular aggregates are easily formed during processing, resulting in uneven dispersion inside the high polymer, thereby causing interface defects, resulting in a decrease in physical and mechanical properties of the product. In order to overcome the shortcomings of calcium carbonate application and improve its compatibility and dispersibility with polymer materials, it has become a functional reinforcing and toughening filler material. In recent years, research at home and abroad has been very active.
The surface modification method of calcium carbonate is generally classified into four types: a coupling agent, an organic surface treatment agent, an inorganic material treatment agent, and a comprehensive surface treatment agent. It is generally believed that the surface modification of the filler by the surfactant or organic acid is physical adsorption, which can improve the rheological properties and processing properties of the material, but has little improvement on the physical and mechanical properties of the product. Modification with a coupling agent not only improves the processability, but also {TodayHot} and also improves the physical and mechanical properties of the article.
We use JL-G01 modifier to modify the surface of ordinary light calcium carbonate. Through physical and chemical action, the surface of calcium carbonate is organicized, thus preventing the agglomeration of calcium carbonate particles, and the particles are evenly distributed in the state of primary particles. It exists in the state of nano-particles. Therefore, it can be used in composite processing systems to improve not only dispersibility and compatibility, but also improve system fluidity and processing properties, and impart better physical and mechanical properties to the product to achieve toughening and reinforcing effects. .
1 experimental part
1.1 main raw materials and equipment
Polyvinyl chloride (PVC) S-1000 Qilu Petrochemical Company
Modifier JL-G01 Rudong Jinlai Amino Acid Co., Ltd.
Light calcium carbonate (CaCO3) industrial grade sorghum calcium carbonate plant
Composite stabilizer aF-1 Rudong Plastic Chemical Factory
Processing aid KM355P Wu Yu Chemical Company
Plasticizer (DOP) Industrial Grade Jinling Petrochemical Company
High-speed mixer SHR-10a Zhangjiagang Keda Machinery Co., Ltd.
Double Roller Refining Machine SK-106B Shanghai Rubber Machinery Factory
Universal material testing machine INSTRON4466 UK
Electron microscope JMC-35C Japan {HotTag}
Torque rheometer PLE331 Germany
1.2 Test methods
1.2.1 Surface treatment method
The ordinary light calcium carbonate is dried to a moisture content of 0.5% or less, and added to a high-speed mixer, and a JL-G01 type modifier is added at 1.5% (W), and the temperature is raised to 100 ° C, and the mixture is stirred for 8 minutes for discharge.
1.2.2 Preparation of polyvinyl chloride (PVC) samples
Raw materials such as PVC resin, composite stabilizer, DOP, ordinary calcium carbonate or modified calcium carbonate are formulated according to the formula, and mixed in a high-speed mixer for 10 minutes for use. The mixture was plasticized in a two-roll refiner, the film was fully plasticized at 165 ° C for 6 min, and the hard sheet was fully plasticized at 190 ° C for 8 min to make a 0.5 mm thick sheet. After being placed at room temperature for 24 hours, it was cut into dumbbells. The sample is ready for testing.
2 results and discussion
Comparison of microscopic morphology before and after modification of calcium carbonate
Under the electron microscope, the microscopic morphology of ordinary calcium carbonate and modified calcium carbonate was compared. The results are shown in Fig. 1.
Ordinary calcium carbonate modified calcium carbonate
Figure 1 Comparison of electron micrographs before and after calcium carbonate modification
It can be clearly seen from Fig. 1 that the ordinary calcium carbonate particles have a wide distribution range and mostly exist in the form of aggregated state, and the modified calcium carbonate particles are subjected to surface modification treatment, the surface energy is low, no agglomeration, and uniform dispersion is achieved, The state of the primary particles exists, some of which are in the state of nanoparticles (particle size is less than 100 nm), so that it can achieve better dispersion in the PVC resin and play a toughening and reinforcing effect.
2.2 Comparison of rheological properties before and after calcium carbonate modification
We mixed ordinary calcium carbonate and modified calcium carbonate according to the formula, and placed it at room temperature for 8 hr and then carried out rheological experiment on PLE331 type torque rheometer. The results are shown in Table 1.
Table 1 Rheological experiment results*
Name Maximum Torque / Nm Balance Torque / Nm Plasticizing Time / S Melting Temperature / °C
Ordinary CaCO3 37.4 25.0 150 187
Modified CaCO3 34.3 24.1 120 186
*Recipe: PVC 100 parts composite stabilizer 5 parts KM355P6 parts
Ordinary CaCO3 or modified CaCO315
It can be seen from Table 1 that compared with ordinary calcium carbonate, the addition of modified calcium carbonate reduces the torque, the plasticizing time is obviously shortened, the melting temperature decreases, and the plasticizing speed becomes faster, indicating that the modified calcium carbonate has good compatibility with the PVC system. It is beneficial to processing, can improve the extrusion speed, and make the appearance of the product smooth and delicate. This is because the modifier of the chemical bonding of the surface of the modified calcium carbonate has good compatibility with the PVC resin, and exhibits strong internal lubrication, thereby weakening the force between the PVC molecules and changing the rheological properties of the system. It also shows that under the same conditions, the modified calcium carbonate can increase the filling amount and also achieve good processing performance.
2.3PVC test piece test results comparison
We prepared hard and soft test pieces from ordinary calcium carbonate and modified calcium carbonate, and tested them on the INSTRON 4466 universal material testing machine. The results are shown in Table 2 and Table 3.
Table 2 Comparison of test results of rigid PVC test pieces*
Name Yield Strength / Mpa Breaking Strength / Mpa Elongation at Break / % Young's Modulus / Mpa
Ordinary CaCO3 50.835 21.364 46.569 2666.59
Modified CaCO3 51.952 42.456 103.360 2740.27
*Recipe: PVC 100 parts composite stabilizer 5 parts DOP5 parts ordinary CaCO3 or modified CaCO320 parts
Table 3 Comparison of test results of soft PVC test strips*
Name Yield Strength / Mpa Breaking Strength / Mpa Elongation at Break / % Young's Modulus / Mpa
Ordinary CaCO3 7.09 6.91 48.7 75.7
Modified CaCO3 7.11 6.92 109.1 60.7
*Recipe: PVC 100 parts composite stabilizer 5 parts DOP50 parts
Ordinary CaCO3 or modified CaCO3120 parts
It can be seen from Table 2 and Table 3 that, in the case of the same addition amount, regardless of the PVC hard and soft products, the modified calcium carbonate is used, and the mechanical properties of the test piece are obviously superior to ordinary calcium carbonate, especially the test piece. The elongation at break is more than doubled, and the material is easy to plasticize, non-stick roller, high surface brightness and excellent processing performance. This is because ordinary calcium carbonate has a strong surface and high surface energy, is easy to agglomerate in the PVC resin, and is not easily dispersed, thereby affecting the processability of the product and destroying the mechanical properties of the product. The surface of the modified calcium carbonate has been organically modified, the surface energy is significantly reduced, and it is not easy to agglomerate. It is basically dispersed into the PVC resin in the state of primary particles, and is strongly strengthened at the interface by the molecular bridge of the organic modifier. The adhesion, and some of the rigid particles dispersed in the nano state penetrate into the three-dimensional network structure of the PVC resin. According to the viewpoint of non-elastomer toughening modification, rigid nano-sized calcium carbonate particles have few surface defects, many unpaired atoms, and are firmly bonded with PVC resin. When subjected to external force, the matrix resin is silver-stained to absorb energy, and brittle-tough occurs. Transformation [6], so as to avoid local stress concentration and cracking, so that the composite material achieves toughening and reinforcing effect, and has good mechanical properties.
3 conclusions
(1) Calcium carbonate modified by JL-G01 Modifier is uniformly distributed in the state of primary particles compared with ordinary calcium carbonate, does not agglomerate, and has excellent compatibility and dispersibility with PVC resin. , can increase the filling amount, and at the same time achieve the toughening and reinforcing effect.
(2) The modified calcium carbonate imparts excellent rheological properties to the PVC processing system, shortens the plasticizing time, accelerates the melting, promotes the plasticization, thereby improving the processing efficiency and imparting excellent surface properties to the product.
(3) The modified calcium carbonate is filled in the hard and soft PVC products. Compared with ordinary calcium carbonate, it is not only easy to plasticize, but also has no sticking roller, and has excellent processing performance, and the breaking strength and elongation at break of the product are obviously improved. Has good physical and mechanical properties.
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