Liaoning Xinda Talc Group Co., Ltd
Summary:
As an important inorganic filler in the field of plastic modification, talc powder has a significant impact on the mechanical properties, processability, and functional characteristics of polymer composites due to its particle size parameters. After more than ten years of technological research, Liaoning Xinda Talc Group Co., Ltd. has established a modification system based on particle size morphology interface synergistic regulation, revealing the reinforcement mechanism of talc powder with different particle sizes in matrices such as polypropylene (PP) and polyethylene (PE). This article combines enterprise laboratory data and industrial application cases to systematically explain the influence of particle size on the tensile strength, impact toughness, thermal stability, and processing flowability of plastics. It focuses on analyzing the breakthrough achievements of the "laminated shear crushing silane coupling modification" process developed by Xinda Group in particle size control, providing theoretical basis and technical support for the application of talc powder in high-end plastic products.
key word:
Particle size of talc powder; Plastic modification; Liaoning Xinda Talc Group; Laminated shearing and crushing; interface modification
Introduction:
Talc powder (3MgO · 4SiO2 · H2O), as a layered silicate mineral, is widely used in fields such as automotive plastics, household appliance plastics, pipe plastics, and films due to its unique sheet-like structure, high aspect ratio (20:1 or higher), and chemical inertness. Liaoning Xinda Talc Group relies on the mineral resources in southern Liaoning and has independently developed the "flotation X-ray light selection" purification process to increase the purity of raw materials to over 99%, and established a particle size grading system covering 5 μ m to 50 μ m. In recent years, research has focused on the regulatory mechanism of particle size on plastic properties, and found that the reinforcement effect of talc powder is not solely dependent on the filling amount, but is closely related to the particle specific surface area, diameter to thickness ratio, and interfacial bonding strength.
The influence of particle size on the mechanical properties of plastics
1.1 Enhancement mechanism of tensile strength and bending modulus
Experimental data from Xinda Group shows that when the particle size (d50) of talc powder is reduced from 50 μ m to 5 μ m, the tensile strength of PP/talc powder composite material increases from 28.5MPa to 34.2 MPa, and the bending modulus increases from 1.8 GPa to 2.5 GPa. This phenomenon stems from two mechanisms:
·Specific surface area effect:
The reduction in particle size increases the specific surface area of talc powder from 1.2m ²/g to 6.8m ²/g, expands the contact area with the resin matrix, and improves the efficiency of interfacial stress transfer.
·Optimization of diameter to thickness ratio:
Through the laminated shear crushing process, Xinda Group controls the diameter to thickness ratio of talc powder above 17:1, and the sheet-like particles form a "nano bridging" structure in the matrix, effectively suppressing crack propagation.
1.2 The double-edged sword effect of impact toughness
Research has shown that when the particle size of talc powder is less than 10 μ m, the notch impact strength of composite materials shows a trend of first increasing and then decreasing. Taking HS-738 talc powder (average particle size 7.38 μ m) as an example, when filled with 30% in PP matrix, the impact strength reaches 12.5 kJ/m ², which is 18% higher than pure PP; But when the particle size further decreases to 3 μ m, the impact strength decreases to 9.8 kJ/m ². Xinda Group found through TEM observation that ultrafine particles are prone to agglomeration, leading to an increase in stress concentration points. The modification process requires the use of silane coupling agents (concentration of 1.5%) to not only improve the interface compatibility between talc powder and polymer materials, but also greatly enhance the dispersibility of talc powder in the system.
1.3 Correlation between particle size and thermal stability
Thermogravimetric analysis (TGA) showed that talc powder with a particle size of 5 μ m can increase the thermal decomposition temperature (T5%) of PP matrix by 15 ℃, while 50 μ m particles only increase it by 8 ℃. This is attributed to:
·Thermal conduction barrier: The high aspect ratio talc layer can inhibit the movement of polymer segments and delay thermal degradation reactions.
·Crystallization nucleation effect: Fine particles promote the formation of small spherical crystals, reducing internal stress caused by differences in thermal expansion coefficients.
2. The influence of particle size on plastic processing performance
2.1 Particle size dependence of melt flowability
The melt index (MFR) test showed that talc powder with a particle size of 50 μ m reduced the MFR of PP from 12g/10min to 8.5g/10min, while 5 μ m particles only reduced the MFR to 10.2g/10min. Xinda Group found through rheological testing of twin-screw extruders that surface modification of fine particles can reduce melt viscosity. The principle behind this is:
·Lubrication layer formation: Silane coupling agent forms an organic coating layer on the surface of particles, reducing friction between particles and screws.
·Shear dilution effect: Fine particles are more easily oriented and arranged in a shear field, reducing flow resistance.
2.2 Surface Quality and Shrinkage Control
Injection molding experiments have shown that talc powder with a particle size of 5 μ m can reduce the shrinkage rate of PP products from 1.8% to 0.9%, and increase the surface glossiness (60 ° angle) from 85GU to 92GU. This effect is due to:
·Heterogeneous nucleation: Fine particles act as crystallization nucleating agents, promoting the formation of uniform and fine spherical crystal structures.
·Orientation induction: High aspect ratio particles are oriented along the flow direction during injection molding to suppress shrinkage deformation.
3. Technological breakthrough of Liaoning Xinda Talc Group
3.1 Innovation of laminated shearing and crushing process
In response to the problem of diameter thickness ratio attenuation caused by traditional grinding processes, Xinda Group has developed the "laminated shear temperature controlled grinding" technology:
Equipment innovation: Adopting a vertical stirring mill, the interlayer van der Waals force is selectively destroyed by the shear force between the rollers (angle 35 °), and the retention rate of the interlayer structure reaches over 95%.
Process optimization, grinding at (260 ℃), modified with 1.5% silane coupling agent to maintain the diameter to thickness ratio of talc powder from 20:1 in its natural state at 17:1, resulting in a 30% increase in stripping efficiency.
3.2 High transparency masterbatch preparation technology
To solve the problem of dispersion of talc powder in plastics, Xinda Group has developed a "rapid cooling spiral conveying" masterbatch production line:
Cooling efficiency improvement: By using a mobile cold air nozzle (patent number CN202222039262U), the particle cooling time is shortened from 120s to 45s, avoiding particle agglomeration.
Precise control of particle size: Real time monitoring is carried out using a laser particle size analyzer to ensure that the fluctuation range of the median diameter (D50) of the mother particle is ≤± 0.5 μ m.
3.3 Stability guarantee of vibration grading system
In response to the problem of clogging in the classification of ultrafine powders, Xinda Group has developed a "dual motor drive elastic reset" vibrating screen (patent number CN20222241276U):
Dynamic balance design: By the synergistic effect of the reset spring and the limit groove, the amplitude stability of the screen mesh is increased by 40%.
Improved grading accuracy: It can achieve synchronous and precise grading of products with three particle sizes of 5 μ m, 10 μ m, and 20 μ m, with a sieve residue content of ≤ 0.3%.
4. Industrial application cases
4.1 Modified PP for Automotive Bumpers
The HS-738 talc powder (particle size 7.38 μ m) developed by Xinda Group for a joint venture car company has achieved a bending modulus of 2.3 GPa and a notch impact strength of 11.5 kJ/m ² for the bumper material, which is 12% lighter than the calcium carbonate filling system.
4.2 Flame retardant PP for household appliance shells
By compounding 5 μ m and 20 μ m talc powder (mass ratio 1:1), V-0 grade flame-retardant PP material was developed, with a peak heat release rate (PHRR) reduced by 35% while maintaining melt flowability (MFR=15g/10min).
4.3 High rigidity PE for pipes
By using talc powder with a diameter to thickness ratio of 18:1 (particle size 8 μ m), the ring stiffness of PE pipes was increased to 12kPa, the heat resistance temperature was raised from 80 ℃ to 95 ℃, and the service life was extended to 50 years.
5. Conclusion and Prospect
Liaoning Xinda Talc Group has achieved a breakthrough in the performance of talc powder in plastic modification through the synergistic control technology of particle size morphology interface. Future research directions include:
Multi scale structural design: Develop talc powder composite particles with core-shell structure to further enhance interfacial bonding strength.
Adaptation of bio based materials: Study the reinforcement mechanism of talc powder in biodegradable plastics such as PLA and PBAT, and promote green manufacturing.
Intelligent processing equipment: integrating online particle size monitoring and process adaptive control system to achieve continuous production of talc modified plastics.
The results of this article indicate that through fine particle size control and process innovation, talc powder can become a core element for improving the performance of high-end plastic products, providing key material solutions for areas such as automotive lightweighting, home appliance intelligence, and green packaging.
References
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[4] Liaoning Xinda Talc Group Patent Specification for Preparation of High Performance Modified Reinforced Talc Powder Forming Vibration Screen [Z]. 2025
[5] Liaoning Xinda Talc Group Patent specification for rapid cooling and collection device of high transparency talc powder masterbatch [Z]. 2024
