Plastic filling modification refers to the method of adding inorganic or organic fillers (such as calcium carbonate, talcum powder, glass fiber, etc.) to plastics to change their mechanical properties, processing properties, usability, or reduce costs. Its main purpose is to improve the strength, hardness, heat resistance, and cost reduction of plastics. The laboratory twin-screw extruder plays an important role in plastic filling modification.
Application of inorganic fillers
Calcium carbonate filling modification
Performance improvement: Calcium carbonate is one of the most commonly used inorganic fillers in plastic filling modification. In laboratory twin-screw extruders, calcium carbonate can be mixed with various plastics such as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC). When calcium carbonate is filled into plastic, it can improve the hardness and rigidity of the plastic. For example, adding an appropriate amount of calcium carbonate to PP can increase its Rockwell hardness from around 80-90R to around 100-110R, which is very beneficial for manufacturing products that require higher hardness, such as plastic pipes and plastic furniture.
Cost reduction: Calcium carbonate has a relatively low price, and filling it into plastic can to some extent reduce material costs. The filling amount can be adjusted according to product requirements while ensuring that the basic properties of the plastic meet the usage requirements. Usually, the filling amount of calcium carbonate can reach about 10% -50% of the plastic mass. For example, when producing ordinary PVC profiles, filling with about 30% calcium carbonate can not only reduce production costs, but also maintain the basic mechanical properties and appearance quality of the profiles.
Talc powder filling modification
Enhancement effect: Talc powder has a layered structure, and under the action of a twin-screw extruder, it can be uniformly dispersed in the plastic matrix, playing a role in enhancing and improving plastic properties. Filling talc powder in polyamide (PA) can significantly improve the heat resistance and dimensional stability of PA. For example, PA6 without talc powder filling is prone to deformation in high temperature environments, while after filling with 30% talc powder, its thermal deformation temperature can be increased from about 60 ℃ to about 120 ℃. This modified PA6 can be used to manufacture components around automotive engines that require high heat resistance and dimensional stability.
Improving barrier performance: Talc powder filling can also improve the barrier performance of plastics. For some packaging materials, such as PP film filled with talc powder, their barrier properties against water vapor and oxygen are improved. This is because the layered structure of talc powder forms a tortuous channel in the plastic matrix, increasing the path length for gas and water vapor to pass through, thereby reducing the transmittance.
Titanium dioxide filling modification
Optical performance improvement: Titanium dioxide is a white pigment with high refractive index and good coverage. Filling titanium dioxide in plastics is mainly used to improve the optical properties of plastics. For example, filling titanium dioxide in polystyrene (PS) can significantly improve the whiteness and glossiness of PS. In a twin-screw extruder, by precisely controlling the filling amount and dispersion degree of titanium dioxide, PS products with different whiteness and glossiness can be manufactured for use in packaging materials, stationery, and other fields.
UV shielding effect: Titanium dioxide also has UV shielding function. In some outdoor plastic products, such as plastic trash cans and outdoor plastic furniture, filling titanium dioxide can effectively absorb and reflect ultraviolet rays, reduce the photo aging effect of ultraviolet rays on plastics, and extend the service life of plastic products.
Application of organic fillers
Wood fiber filling modification
Preparation of biobased materials: Wood fiber is a renewable organic filler. In a laboratory twin-screw extruder, it can be mixed with thermoplastic to prepare biobased composite materials. For example, mixing wood fibers with polylactic acid (PLA) can not only reduce the cost of PLA, but also endow the material with good biodegradability and woody texture. This modified material can be used to manufacture environmentally friendly products such as disposable tableware and packaging materials.
Enhancement and toughening effects: Wood fibers can also enhance and toughen plastics to a certain extent. Filling wood fibers in PP can improve the tensile strength and impact toughness of PP due to the interaction between wood fibers and PP matrix. For example, when the filling amount is about 20%, the tensile strength of PP can be increased by about 20% -30%, and the impact toughness can be increased by about 30% -40%. It can be used to manufacture some household products that have certain requirements for mechanical properties.
Modification of waste rubber filling
Resource recycling and utilization: Filling with waste rubber is an effective way of resource recycling and utilization. In a twin-screw extruder, waste rubber (such as waste tire rubber) is crushed and filled into plastic. For example, filling into ethylene vinyl acetate copolymer (EVA) can improve the elasticity and wear resistance of EVA. This is very advantageous for manufacturing products such as shoe soles and sports field materials, while also solving the problem of waste rubber disposal and reducing environmental pollution.
Improving damping performance: Filling with waste rubber can also improve the damping performance of plastics. For some products that require shock absorption and noise reduction, such as car interior parts, plastic filled with waste rubber can effectively absorb and attenuate vibration and noise, improving ride comfort.
Application of Nanofillers
Nano calcium carbonate filling modification
Significant performance improvement: Compared with ordinary calcium carbonate, nano calcium carbonate can significantly improve plastic properties due to its nanoscale effect. In the laboratory twin-screw extruder, nano calcium carbonate can be uniformly dispersed in the plastic matrix. For example, filling nano calcium carbonate in PVC can not only improve its hardness and rigidity, but also enhance its toughness. This is because nano calcium carbonate particles can act as stress concentration points in the PVC matrix, causing silver lines and shear bands, absorbing energy, and thus improving toughness. Meanwhile, the filling of nano calcium carbonate can also improve the processing performance of PVC and enhance the fluidity of the melt.
Multi functional modification: Nano calcium carbonate filling can also endow plastics with some special functions. For example, filling nano calcium carbonate in PE film can improve the barrier and anti-static properties of the film to a certain extent. This is because the presence of nano calcium carbonate changes the microstructure of the film, increases the resistance to gas and water vapor transmission, and makes it easier for charges to conduct, reducing static electricity accumulation.
Carbon nanotube filling modification
Electrical performance improvement: Carbon nanotubes have excellent electrical properties. In a laboratory twin-screw extruder, filling carbon nanotubes into plastics, such as conductive polymers like polyaniline, can greatly improve the conductivity of the material. Carbon nanotubes form a conductive network in the plastic matrix, transforming the originally insulating plastic into a material with certain conductivity. This modified material can be used to manufacture anti-static materials, electromagnetic shielding materials, etc.
Enhanced mechanical properties: Carbon nanotubes can also enhance the mechanical properties of plastics. Filling carbon nanotubes into epoxy resin can significantly improve its tensile strength and modulus due to the high strength and modulus of carbon nanotubes. Meanwhile, the interaction between carbon nanotubes and epoxy resin matrix can also improve the toughness of the material, which can be used in high-end fields such as aerospace and electronics.
The laboratory twin-screw extruder has broad application prospects and significant advantages in plastic filling modification. By selecting and optimizing process parameters reasonably, its performance can be fully utilized to improve the quality and performance of filled modified plastics.
