Method for improving interfacial compatibility of PE and PS

Abstract

The invention provides a method for improving interfacial compatibility of PE (polyethylene) and PS (polystyrene), and belongs to the technical field of HI PS production. The method comprises the following steps: preparing compatilizer premixed master batches of a hydrogenated styrene-butadiene block copolymer and a styrene-butadiene-styrene block copolymer, and determining an optimal compatilizer dosage by adopting an interfacial tension prediction model; a multi-stage melt blending process is adopted to realize segmented addition and step-by-step mixing of components, inorganic powder and a processing aid are added to form a composite aid system to regulate crystallization behavior and improve thermal stability, and process parameters such as temperature and rotating speed of a twin-screw extruder are controlled to promote dispersion orientation of a compatilizer on an interface. And optimal cooling parameters are determined through a graded cooling temperature optimization experiment and iterative optimization of a shortest path algorithm to realize matching of polyethylene crystallization and a polystyrene curing process, so that the technical problem of unstable mechanical properties of an alloy material caused by poor interfacial compatibility of polyethylene and polystyrene is solved.

Description

Technical Field

[0001] This invention belongs to the field of HIPS production technology, and more specifically, relates to a method for improving the interface compatibility of PE and PS. Background Technology

[0002] Polyethylene and polystyrene alloys are widely used in packaging, building materials, and automotive parts. Traditional methods for improving interfacial compatibility primarily rely on adding compatibilizers to reduce interfacial tension. Commonly used compatibilizers include maleic anhydride-grafted polyethylene and styrene-ethylene-butene-styrene block copolymers, which form a transition layer at the interface between the two phases through physical blending or chemical modification. In current polymer alloy preparation processes, due to the significant difference in polarity and surface tension between polyethylene (a non-polar polymer) and polystyrene (a weakly polar polymer), interfacial bonding is insufficient, making them prone to debonding under mechanical stress. Existing compatibilizer addition methods lack precise theoretical guidance and often rely on empirical proportions and process parameters. The main drawbacks of traditional technologies include difficulty in accurately determining the compatibilizer dosage, inaccurate prediction of interfacial tension, and internal stress caused by mismatched shrinkage of the two phases during cooling. These defects directly affect the interfacial bonding strength and overall performance stability of the alloy material. In other words, existing technologies suffer from poor interfacial compatibility between polyethylene and polystyrene, leading to unstable mechanical properties in the alloy material. Summary of the Invention

[0003] In view of this, the present invention provides a method for improving the interfacial compatibility of PE and PS, which can solve the technical problem in the prior art where poor interfacial compatibility between polyethylene and polystyrene leads to unstable mechanical properties of alloy materials.

[0004] This invention is implemented as follows: This invention provides a method for improving the interfacial compatibility of PE and PS, comprising: preparing a compatibilizer premix masterbatch; mixing hydrogenated styrene-butadiene block copolymer and styrene-butadiene-styrene block copolymer; adding paraffin oil; and stirring in a high-speed mixing tank to form a uniform compatibilizer premix masterbatch; establishing an interfacial tension prediction model; measuring the surface tension parameters of polyethylene and polystyrene; calculating the interfacial tension values ​​at different compatibilizer concentrations; determining the optimal compatibilizer dosage to reduce the interfacial tension to a preset threshold range; and performing multi-stage melt blending, adding polyethylene and polystyrene in the first stage. The compatibilizer premix masterbatch is added to the twin-screw extruder at the first feeding port and then to the second feeding port to ensure that the compatibilizer premix masterbatch is preferentially distributed at the polymer interface. A composite additive system is added, and inorganic powder and processing aids are added to the third feeding port. The melt extrusion process parameters are controlled, and the temperature and screw speed of the twin-screw extruder are set to promote the dispersion and orientation of the compatibilizer premix masterbatch at the polyethylene and polystyrene interface through shear force. The staged cooling and solidification parameters are determined through staged cooling temperature optimization experiments and iterative optimization of the shortest path algorithm. The extruded melt is subjected to water cooling at the first temperature and air cooling at the second temperature. The interfacial compatibility is evaluated.

[0005] Specifically, the step of preparing the compatibilizer premixed masterbatch involves mixing hydrogenated styrene-butadiene block copolymer and styrene-butadiene-styrene block copolymer at a mass ratio of 1 to 5:1, adding paraffin oil to 10% to 30% of the total mass fraction, and stirring in a high-speed mixing pot for 3 to 5 minutes to form a uniform compatibilizer premixed masterbatch.

[0006] The hydrogenated styrene-butadiene block copolymer refers to a styrene-butadiene block copolymer that has undergone hydrogenation treatment, possesses good thermal stability and compatibility with polyethylene, and has a molecular weight in the range of 50,000 to 150,000.

[0007] The styrene-butadiene-styrene block copolymer refers to a triblock copolymer with styrene as the end segment and butadiene as the middle segment. It has thermoplastic elastomer properties and can form a transition layer at the interface between polyethylene and polystyrene.

[0008] Specifically, the step of establishing the interfacial tension prediction model is based on the Young-Dupre equation and the Owens-Wendt theory, which is used to predict the interfacial tension value under different component ratios and determine the optimal compatibilizer dosage as 5-10%.

[0009] The multi-stage melt blending refers to setting multiple feed ports at different screw positions of a twin-screw extruder to achieve segmented addition and gradual mixing of components, thereby avoiding the agglomeration of compatibilizer premix masterbatch.

[0010] Specifically, the multi-stage melt blending step involves feeding polyethylene and polystyrene into a twin-screw extruder at the first feeding port, according to a mass fraction ratio of 30-50% polyethylene and 20-40% polystyrene.

[0011] The composite additive system includes a combination of inorganic powder nucleating agent and organic antioxidant. The inorganic powder is talc or calcium carbonate with a particle size in the range of 1 to 5 μm. The main antioxidant is a hindered phenolic compound, and the auxiliary antioxidant is a phosphite compound.

[0012] Specifically, the step of adding the composite additive system involves adding 1-5% inorganic powder and 0.5-2% processing aid at the third feeding port, wherein the inorganic powder acts as a nucleating agent to regulate the crystallization behavior of polyethylene.

[0013] Specifically, the step of controlling the melt extrusion process parameters involves setting the twin-screw extruder temperature to 170–200°C, the screw speed to 200–300 r / min, and the residence time to 3–5 min.

[0014] The staged cooling temperature optimization experiment refers to establishing a multi-objective optimization model using orthogonal experimental design methods, with the first initial temperature, the second initial temperature, the cooling time, and the material thickness as experimental factors, and the phase separation size and the interfacial bonding strength as response indicators.

[0015] The shortest path algorithm refers to constructing the temperature nodes in the cooling process into a weighted graph structure, using the temperature difference as the edge weight, minimizing the accumulation of internal stress as the objective function, and using Dijkstra's algorithm to solve for the optimal cooling path from the initial temperature to the target temperature.

[0016] Specifically, the step of determining the graded cooling and curing parameters involves determining the initial values ​​of the first and second temperatures through a graded cooling temperature optimization experiment, calculating the cooling rate using a shortest path algorithm, feeding the algorithm calculation results back to the graded cooling temperature optimization experiment for the next round of experimental design, and repeating the iteration until convergence.

[0017] The interfacial tension calculation equation set includes the Young-Dupre equation and the Owens-Wendt equation. The Young-Dupre equation is used to calculate the relationship between solid-liquid interfacial tension and surface tension, while the Owens-Wendt equation is used to analyze the contribution of the dispersive and polar components of surface tension to interfacial tension.

[0018] The phase separation size refers to the average particle size of the dispersed phase in the alloy material, which is obtained by statistical analysis of scanning electron microscope images using image analysis software.

[0019] Specifically, the interface compatibility evaluation step involves confirming that the interface compatibility meets the requirements when the phase separation size is less than 1 μm and the interface bonding strength is greater than a preset standard value.

[0020] This invention addresses the technical problem of unstable mechanical properties in alloy materials caused by poor interfacial compatibility between polyethylene and polystyrene by establishing an interfacial tension prediction model based on the Young-Dupre equation and Owens-Wendt theory, combined with staged cooling temperature optimization experiments and an iterative optimization method using the shortest path algorithm. The interfacial tension prediction model employed in this invention can accurately calculate interfacial tension values ​​at different compatibilizer concentrations at the molecular level, overcoming the blindness of traditional empirical proportioning methods. By decomposing surface tension into dispersive and polar components, it reveals the essential mechanism of interfacial interaction, providing a scientific basis for the precise dosage of compatibilizers. Simultaneously, this invention achieves coordinated matching between the polyethylene crystallization process and the polystyrene curing process through staged cooling temperature optimization experiments and closed-loop iterative optimization using the shortest path algorithm, effectively reducing internal stress generated during cooling and improving the stability of interfacial bonding strength. In summary, this invention solves the technical problem mentioned in the background art of unstable mechanical properties in alloy materials caused by poor interfacial compatibility between polyethylene and polystyrene. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method of the present invention.

[0022] Figure 2 The graph shows the relationship between interfacial tension and compatibilizer concentration in the examples.

[0023] Figure 3 This is a temperature optimization curve for the staged cooling in the embodiment. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0025] like Figure 1 The diagram shown is a flowchart of a method for improving the compatibility of PE and PS interfaces provided by the present invention. This method includes the following steps:

[0026] S01. Prepare compatibilizer premixed masterbatch by mixing hydrogenated styrene-butadiene block copolymer and styrene-butadiene-styrene block copolymer at a mass ratio of 1 to 5:1, adding paraffin oil to 10% to 30% of the total mass fraction, and stirring in a high-speed mixing pot for 3 to 5 minutes to form a uniform compatibilizer premixed masterbatch.

[0027] S02. Establish an interfacial tension prediction model, measure the surface tension parameters of polyethylene and polystyrene, calculate the interfacial tension values ​​at different compatibilizer concentrations, and determine the optimal compatibilizer dosage as 5-10% to reduce the interfacial tension to a preset threshold range.

[0028] S03. Perform multi-stage melt blending. According to the mass fraction ratio of polyethylene 30-50% and polystyrene 20-40%, first feed polyethylene and polystyrene into the twin-screw extruder through the first feeding port, and then feed compatibilizer premixed masterbatch into the second feeding port to ensure that the compatibilizer premixed masterbatch is preferentially distributed at the polymer interface.

[0029] S04. Add a composite additive system, add 1-5% inorganic powder and 0.5-2% processing aid at the third feeding port, wherein the inorganic powder acts as a nucleating agent to regulate the crystallization behavior of polyethylene, and the processing aid includes a main antioxidant and an auxiliary antioxidant to improve the thermal stability of the alloy material.

[0030] S05. Control the melt extrusion process parameters, set the twin-screw extruder temperature to 170-200℃, the screw speed to 200-300r / min, and the residence time to 3-5min, so as to promote the dispersion and orientation of the compatibilizer premixed masterbatch at the interface of polyethylene and polystyrene through shear force.

[0031] S06. The graded cooling curing parameters are determined through graded cooling temperature optimization experiments and iterative optimization of the shortest path algorithm. The extruded melt is subjected to water cooling at the first temperature and air cooling at the second temperature. The initial values ​​of the first and second temperatures are determined through graded cooling temperature optimization experiments, and the cooling rate is calculated by the shortest path algorithm. Then, the algorithm calculation results are fed back to the graded cooling temperature optimization experiments for the next round of experimental design. The iteration is repeated until convergence, so that the polyethylene crystallization and polystyrene curing process are matched.

[0032] S07. Conduct an interface compatibility evaluation. Observe the cross-sectional morphology of the alloy material using a scanning electron microscope, and determine the phase separation size and interface bonding strength. When the phase separation size is less than 1 μm and the interface bonding strength is greater than the preset standard value, the interface compatibility is confirmed to meet the requirements.

[0033] The hydrogenated styrene-butadiene block copolymer refers to a styrene-butadiene block copolymer that has undergone hydrogenation treatment. It has good thermal stability and compatibility with polyethylene, and its molecular weight is usually in the range of 50,000 to 150,000.

[0034] The styrene-butadiene-styrene block copolymer refers to a triblock copolymer with styrene as the end segment and butadiene as the middle segment. It has thermoplastic elastomer properties and can form a transition layer at the interface of polyethylene and polystyrene.

[0035] The interfacial tension prediction model is based on the Young-Dupre equation and Owens-Wendt theory and is used to predict interfacial tension values ​​under different component ratios.

[0036] The multi-stage melt blending refers to setting multiple feed ports at different screw positions of a twin-screw extruder to achieve segmented addition and gradual mixing of components, thereby avoiding the agglomeration of compatibilizer premix masterbatch.

[0037] The composite additive system includes a combination of inorganic powder nucleating agents and organic antioxidants. The inorganic powder is usually talc or calcium carbonate with a particle size in the range of 1 to 5 μm. The main antioxidant is a hindered phenolic compound, and the auxiliary antioxidant is a phosphite compound.

[0038] The staged cooling temperature optimization experiment refers to the establishment of a multi-objective optimization model by using orthogonal experimental design method, with the first initial temperature value, the second initial temperature value, the cooling time, and the material thickness as experimental factors, and the phase separation size and the interface bonding strength as response indicators. The model is trained by the experimental data to predict the neural network, and the experimental parameters are adjusted according to the feedback results of the shortest path algorithm.

[0039] The shortest path algorithm refers to constructing the temperature nodes in the cooling process into a weighted graph structure, using the temperature difference as the edge weight, minimizing the accumulation of internal stress as the objective function, and using Dijkstra's algorithm to solve for the optimal cooling path from the initial temperature to the target temperature, outputting the optimal cooling rate sequence, and feeding the results back to the staged cooling temperature optimization experiment.

[0040] The phase separation size refers to the average particle size of the dispersed phase in the alloy material, which is obtained by statistical analysis of scanning electron microscope images using image analysis software.

[0041] The first initial temperature value refers to the initial target temperature value of the water cooling stage in the graded cooling and curing process, which is determined by the first round of experiments in the graded cooling temperature optimization experiment.

[0042] The second initial temperature value refers to the initial target temperature value of the air-cooling stage in the graded cooling and curing process, which is determined by the first round of experiments in the graded cooling temperature optimization experiment.

[0043] The first temperature refers to the final target temperature value of the water cooling stage in the graded cooling and solidification process, which was determined after iterative optimization.

[0044] The second temperature refers to the final target temperature value of the air-cooling stage in the graded cooling and curing process, which was determined after iterative optimization.

[0045] The set of equations for calculating interfacial tension includes the Young-Dupre equation and the Owens-Wendt equation.

[0046] The Young-Dupre equation is used to calculate the relationship between solid-liquid interfacial tension and surface tension. The inputs include the surface tension values ​​of polyethylene and polystyrene, the contact angle measurement value, and the temperature parameter. The output is the theoretical value of the interfacial tension.

[0047] The Owens-Wendt equation is used to analyze the contribution of the dispersive and polar components of surface tension to interfacial tension. The inputs include the polyethylene dispersive component, the polyethylene polar component, the polystyrene dispersive component, the polystyrene polar component, and the compatibilizer concentration. The output is the corrected interfacial tension prediction value, which is used to determine the optimal amount of compatibilizer in step S02.

[0048] The advantage of this invention, which combines the Young-Dupre and Owens-Wendt equations, lies in its ability to accurately describe the interfacial interaction mechanism between polyethylene and polystyrene at the molecular level. Compared to traditional empirical formulas, this equation set can decompose surface tension into dispersive and polar components, revealing the contribution of different components to interfacial tension, thus providing a theoretical basis for the selection and dosage determination of compatibilizers. Existing Flory-Huggins theory mainly describes polymer compatibility based on statistical thermodynamics, but it cannot accurately predict the absolute value of interfacial tension. In contrast, the equation set of this invention, by combining contact angle measurement and surface tension analysis, can quantitatively calculate interfacial tension, guiding compatibilizer design.

[0049] The advantage of this invention, which employs graded cooling temperature optimization experiments and iterative optimization using the shortest path algorithm, lies in its ability to simultaneously address the matching problem between polyethylene crystallization behavior and polystyrene curing process. Compared to traditional single-temperature control methods, this iterative optimization method obtains multi-objective response data through experiments, and the algorithm finds the optimal cooling path based on graph theory principles. The experiment and algorithm feedback each other to form a closed-loop optimization, enabling the finding of the global optimum in a complex multivariate space. Existing linear cooling methods only consider a single cooling rate and cannot handle the time differences between polyethylene crystallization and polystyrene curing. This invention, through graded control and path optimization, achieves coordinated matching of the two polymer solidification processes, fundamentally reducing the generation of internal stress.

[0050] The specific implementation of the above steps is described in detail below. The specific implementation of step S01 is as follows: First, the hydrogenated styrene-butadiene block copolymer and the styrene-butadiene-styrene block copolymer are accurately weighed according to a preset mass ratio, controlled within the range of 1 to 5:1, preferably 3:1. This ensures effective molecular chain entanglement at the interface between the two block copolymers through the principle of molecular weight matching. Then, paraffin oil is added to the mixture as a plasticizer, with the mass fraction controlled within the range of 10% to 30% of the total mass, preferably 20%. The addition of paraffin oil, based on the free volume theory, can lower the glass transition temperature of the block copolymer and improve the mobility of the molecular chain segments. Next, the mixture is placed in a high-speed mixing tank for mechanical mixing. The stirring speed is set to 1500–2000 r / min, and the stirring time is controlled within 3–5 min. The stirring process adopts the shear mixing principle, using high shear force to fully expand and uniformly disperse the block copolymer molecular chains, forming a homogeneous mixture at the molecular level. The purpose of the entire preparation process is to obtain compatibilizer premixed masterbatch with good flowability and dispersibility, so as to provide a basic material for subsequent improvement of interfacial compatibility.

[0051] The specific implementation of step S02 involves first measuring the surface tension parameters of polyethylene and polystyrene using a contact angle measuring instrument. The measurement employs the Young's equation principle, calculating the solid surface tension value based on the contact angle of the droplet on the solid surface. The surface tension value of polyethylene is typically in the range of 31–33 mN / m, while that of polystyrene is typically in the range of 40–42 mN / m. Subsequently, an interfacial tension prediction model is established based on the Owens-Winter theory. This theory decomposes surface tension into dispersive and polar components, calculating the interfacial tension through the principle of component superposition. Input parameters include the polyethylene dispersive component, polyethylene polar component, polystyrene dispersive component, polystyrene polar component, and compatibilizer concentration. The output parameter is the corrected predicted interfacial tension value. Next, the relationship between solid-liquid interfacial tension and surface tension is calculated using the Young's-Dupré equation. Input parameters include the polyethylene surface tension value, the polystyrene surface tension value, the measured contact angle value, and the temperature parameter. The output parameter is the theoretical value of the interfacial tension. Finally, the theoretical calculations and experimental measurements were compared and verified. When the error was less than 5%, the effectiveness of the model was confirmed. The optimal amount of compatibilizer was determined to be 5-10% through model prediction, so that the interfacial tension was reduced to the preset threshold range of 2-4 mN / m.

[0052] The specific implementation of step S03 involves first precisely metering the raw materials according to a mass fraction ratio of 30-50% polyethylene and 20-40% polystyrene, preferably 40% polyethylene and 30% polystyrene. Based on phase diagram theory, this ensures that the two polymers can form a stable two-phase structure in the molten state. Then, the twin-screw extruder is started and set to multi-stage feeding mode. Polyethylene and polystyrene are simultaneously added at the first feeding port. The shear mixing action of the twin screws allows for initial mixing of the two polymers, employing a dispersion mixing principle. The shear strain generated by the screw geometry breaks down and disperses the polymer particles. Next, the compatibilizer premix masterbatch prepared in step S01 is added at the second feeding port. The addition timing is controlled within 30-60 seconds after the initial mixing of polyethylene and polystyrene. Based on the interfacial diffusion principle, compatibilizer molecules can preferentially migrate to the polymer interface, forming a transition layer structure. The entire multi-stage melt blending process employs a segmented feeding strategy to avoid agglomeration of the compatibilizer premix masterbatch, ensuring uniform distribution of the compatibilizer at the polyethylene and polystyrene interface and improving interfacial compatibility.

[0053] The specific implementation of step S04 involves first selecting a suitable inorganic powder as a nucleating agent, typically talc or calcium carbonate, with a particle size controlled within the range of 1–5 μm, preferably 3 μm. Based on the heterogeneous nucleation theory, the surface of the inorganic powder can provide nucleation sites for crystal growth, thus regulating the crystallization behavior of polyethylene. Subsequently, a composite antioxidant system is prepared. The primary antioxidant is a hindered phenolic compound, with a mass fraction controlled within the range of 0.3–0.8%, and the secondary antioxidant is a phosphite compound, with a mass fraction controlled within the range of 0.2–0.5%. Based on the principle of synergistic effect, the primary antioxidant is responsible for capturing free radicals, while the secondary antioxidant is responsible for decomposing hydrogen peroxide, jointly improving the thermal stability of the alloy material. Next, 1-5% inorganic powder and 0.5-2% processing aid are added sequentially at the third feed port of the twin-screw extruder. The preferred mass fraction is 3% inorganic powder and 1% processing aid. The order of addition is based on the principle of optimized dispersion; the inorganic powder is added first to ensure sufficient dispersion, and the organic aid is added later to avoid adverse interactions with the inorganic powder. The entire process of adding the composite additive system employs precise metering and staged addition to ensure uniform distribution of each component in the melt, providing excellent processing and performance properties for the alloy material.

[0054] The specific implementation of step S05 involves first setting the heating temperature of the twin-screw extruder based on the thermal properties of polyethylene and polystyrene. The temperature is controlled within the range of 170–200°C, with a preferred temperature of 185°C. This temperature setting is based on polymer rheology principles, ensuring that the two polymers have similar viscosities at this temperature, which is beneficial for uniform mixing. Next, the screw speed is set to 200–300 r / min, with a preferred speed of 250 r / min. This speed control is based on shear rate theory; by adjusting the speed, the shear rate of the melt is controlled and kept within a suitable range, ensuring thorough mixing while preventing molecular chain breakage. Then, the residence time of the material in the extruder is controlled to be 3–5 min, with a preferred residence time of 4 min. This residence time is determined based on heat and mass transfer principles, ensuring that the material is fully heated and mixed while avoiding thermal degradation. Finally, through coordinated control of screw geometry and process parameters, shear force is used to promote the dispersion and orientation of the compatibilizer premix at the polyethylene and polystyrene interface. Based on molecular orientation theory, appropriate shear force can cause the compatibilizer molecular chains to align at the interface, improving interfacial bonding strength. The purpose of the entire melt extrusion process is to achieve uniform mixing and interfacial modification of multiple components under suitable temperature and shear conditions.

[0055] The specific implementation of step S06 involves first designing a graded cooling temperature optimization experiment using orthogonal experimental design. Initial temperatures (first and second), cooling time, and material thickness are selected as experimental factors, with 3-4 levels for each factor. The initial temperature range is 60-80℃, and the initial temperature range is 20-40℃. A multi-factor optimization model is constructed based on experimental design theory. Experimental testing is then conducted, using phase separation size and interfacial bonding strength as response indicators. The target value for phase separation size is set to be less than 1 μm, and the target value for interfacial bonding strength is set to be greater than 15 MPa. An objective function is established using multi-objective optimization theory. Next, the experimental data is input into a neural network for model training. The neural network uses the backpropagation algorithm and a multilayer perceptron structure to learn the nonlinear relationship between input parameters and output response, establishing a prediction model. Then, a weighted graph structure is constructed to represent the temperature nodes in the cooling process. Temperature difference is used as the edge weight, and the Dijkstra algorithm from the shortest path algorithm is used to solve for the optimal cooling path from the initial temperature to the target temperature. The objective function is set to minimize internal stress accumulation, outputting the optimal cooling rate sequence. Finally, the algorithm's calculation results are fed back to the staged cooling temperature optimization experiment to adjust the experimental parameters for the next round, forming a closed-loop iterative optimization of experiment-algorithm-feedback. This iteration is repeated until the objective function converges, with the convergence criterion set as a change of less than 1% in three consecutive iterations. The entire process is based on adaptive optimization theory, achieving coordinated matching between the polyethylene crystallization process and the polystyrene curing process.

[0056] Step S07 is optional. Its specific implementation involves first preparing a sample of the alloy material using a liquid nitrogen brittle fracture method. The brittle fracture temperature is controlled at -196℃. Based on the principle of low-temperature brittleness, the material undergoes brittle fracture at extremely low temperatures, accurately reflecting its internal microstructure. Subsequently, a scanning electron microscope (SEM) is used to observe the cross-sectional morphology. The accelerating voltage is set to 15–20 kV, and the magnification is selected as 5000–20000x. Based on the principle of electron optics, high-resolution morphological images are obtained through the interaction between the electron beam and the sample surface. Next, image analysis software is used to statistically analyze the SEM images, determining the phase separation size. The analysis software, based on image recognition algorithms, calculates the average particle size of the dispersed phase through edge detection and particle size analysis. The sample size is no less than 200 particles to ensure the statistical significance of the data. Then, a tensile test is performed to determine the interfacial bonding strength. The test is conducted according to relevant standards, with the tensile rate set to 50 mm / min. Based on the principles of material mechanics, the tensile strength and elongation at break of the material are calculated using stress-strain curves. Finally, an evaluation standard was established. When the phase separation size is less than 1 μm and the interfacial bonding strength is greater than 15 MPa, the interfacial compatibility is considered to meet the requirements. This standard is based on the theory of the relationship between material properties and microstructure; the smaller the phase separation size, the better the compatibility, and the higher the interfacial bonding strength, the stronger the interfacial interaction. The entire evaluation process employed quantitative analysis methods to provide a scientific basis for the improvement of interfacial compatibility.

[0057] In another simple embodiment of the present invention, the specific formulation is as follows: 30-50% polyethylene, 20-40% polystyrene, 5-10% compatibilizer, 1-5% inorganic powder, and 0.5-2% processing aid. The compatibilizer is composed of hydrogenated styrene-butadiene block copolymer and styrene-butadiene-styrene block copolymer in a mass ratio of 1-5:1, with paraffin oil added to 10-30% of the total mass of the former two. The inorganic powder is talc or calcium carbonate, with a particle size controlled within the range of 1-5 μm, acting as a nucleating agent to regulate the crystallization behavior of polyethylene. The processing aid includes a primary antioxidant and a secondary antioxidant, wherein the primary antioxidant is a hindered phenolic compound, and the secondary antioxidant is a phosphite compound, used to improve the thermal stability of the alloy material. In this formulation, the hydrogenated styrene-butadiene block copolymer has a molecular weight of 50,000–150,000, exhibiting good thermal stability and compatibility with polyethylene. The styrene-butadiene-styrene block copolymer possesses thermoplastic elastomer properties, forming a transition layer at the polyethylene and polystyrene interface. Through reasonable component ratios and molecular weight control, the synergistic effect of each component is ensured, resulting in a PE / PS alloy material with excellent interfacial compatibility.

[0058] The key technical ideas of this invention mainly include the construction of an interfacial tension prediction model, the application of a multi-stage melt blending process, the integration of a graded cooling optimization algorithm, and the preparation of compatibilizer premixed masterbatch. The interfacial tension prediction model, by combining the Young's-Dupré equation and the Owens-Winter theory, can accurately describe the interfacial interaction mechanism between polyethylene and polystyrene at the molecular level. Compared with traditional empirical formula methods, this model decomposes surface tension into dispersive and polar components, revealing the contribution law of different components to interfacial tension, providing a theoretical basis for compatibilizer selection and dosage determination, and solving the problem that the Flory-Huggins theory in existing technologies cannot accurately predict the absolute value of interfacial tension. The multi-stage melt blending process, by setting multiple feeding ports at different positions in a twin-screw extruder, realizes the segmented addition and gradual mixing of components. Compared with the traditional one-time feeding method, this process, based on the interfacial diffusion principle, allows the compatibilizer to preferentially distribute at the polymer interface, avoiding compatibilizer agglomeration and improving the utilization efficiency and interfacial modification effect of the compatibilizer. The graded cooling optimization algorithm integrates experimental design methods and graph theory algorithms. It obtains multi-objective response data through orthogonal experiments and uses the Dijkstra algorithm to find the optimal cooling path. Compared to traditional linear cooling methods, this algorithm can handle the time differences between polyethylene crystallization and polystyrene curing, achieving coordinated matching of the two polymer solidification processes. The preparation of the compatibilizer premix masterbatch is based on the molecular weight matching principle and free volume theory. By controlling the mass ratio of block copolymers and the amount of paraffin oil added, a compatibilizer system with good flowability and dispersibility was obtained, providing an efficient modifying material for improving interfacial compatibility. The synergistic effect of these key technological ideas forms a complete interfacial compatibility improvement system, from theoretical prediction, process control, process optimization to effect evaluation. Compared to existing single modification methods, this invention achieves a systematic improvement in the interfacial compatibility of polyethylene and polystyrene through multi-technology integration, solving technical problems such as uneven compatibilizer dispersion, mismatched cooling processes, and low interfacial bonding strength in traditional methods.

[0059] It should be noted that this invention also solves the following technical problem: 1. The technical problem of uneven dispersion of compatibilizer in polymer matrix leading to differences in local compatibility effect. In the traditional polymer alloy preparation process, compatibilizer is often added in one go. Due to the viscosity difference between the compatibilizer and the matrix polymer and the limitation of mixing time, compatibilizer agglomeration is prone to occur, resulting in uneven distribution of compatibilizer on a macroscopic scale. The compatibilizer concentration is too high in some areas and insufficient in other areas. This uneven distribution directly affects the consistency of interfacial compatibility effect. This invention utilizes a multi-stage melt blending process, employing multiple feed ports at different screw positions in a twin-screw extruder to achieve segmented addition and gradual mixing of components. First, polyethylene and polystyrene matrix materials are added at the first feed port, and compatibilizer premixed masterbatch is added at the second feed port. This segmented feeding method allows the compatibilizer to participate in the interface construction process from the early stages of polymer interface formation, avoiding secondary penetration of the compatibilizer after interface formation. Simultaneously, by controlling the screw shear force and residence time, sufficient dispersion and orientation of the compatibilizer at the interface are ensured, achieving uniform spatial distribution and ordered interfacial structure. 2. The technical problem of insufficient thermal stability of alloy materials during processing and use, leading to interface performance degradation. Polyethylene and polystyrene alloy materials are prone to thermal oxidation reactions under high-temperature processing conditions, especially in the interfacial region where stress concentration and the presence of compatibilizers make molecular chain breakage and cross-linking reactions more likely. This causes the interfacial performance to gradually degrade with increasing processing time and temperature, affecting the long-term performance of the material. This invention constructs a composite additive system by simultaneously adding inorganic powder and processing aids at the third feeding port. The inorganic powder, such as talc or calcium carbonate, not only acts as a nucleating agent to regulate the crystallization behavior of polyethylene but also acts as a heat stabilizer to absorb and disperse heat, reducing the damage to the interfacial structure caused by local temperature rise. The primary antioxidant in the processing aid is a hindered phenolic compound that can capture free radicals and block the oxidation chain reaction, while the secondary antioxidant is a phosphite compound that can decompose hydrogen peroxide to prevent further oxidation. This synergistic effect of the primary and secondary antioxidants establishes a complete antioxidant protection system, effectively protecting the molecular structural stability of the interfacial region and ensuring the durability of the interfacial performance of the alloy material during processing and use.

[0060] Specifically, the principle of this invention is as follows: This invention can solve the technical problem of poor interfacial compatibility between polyethylene and polystyrene. Its core principle lies in the systematic method combining theoretical modeling and experimental optimization, which achieves precise control of interfacial tension and coordinated matching of the cooling process. First, the combined use of the Young-Dupre equation and Owens-Wendt theory provides a solid theoretical foundation for interfacial tension prediction. The Young-Dupre equation describes the thermodynamic relationship between solid-liquid interfacial tension and surface tension, while the Owens-Wendt equation further decomposes surface tension into dispersive and polar components. This decomposition accurately reflects the different contributions of the non-polar characteristics of polyethylene and the weakly polar characteristics of polystyrene to interfacial interactions. By quantitatively calculating the changes in interfacial tension under different compatibilizer concentrations, the precise amount of compatibilizer that reduces the interfacial tension to the optimal range can be determined. Second, the multi-stage melt blending process ensures that the compatibilizer premixed masterbatch can be preferentially distributed at the polymer interface, avoiding ineffective dispersion of the compatibilizer in the matrix and improving compatibility efficiency. Most importantly, the iterative optimization method of staged cooling temperature optimization experiment and shortest path algorithm solves the matching problem between polyethylene crystallization behavior and polystyrene curing process. Since polyethylene is a crystalline polymer and polystyrene is an amorphous polymer, their shrinkage behavior during cooling is significantly different. Traditional uniform cooling methods will cause stress concentration at the interface. This invention establishes a multi-objective optimization model through orthogonal experimental design, and at the same time uses the shortest path algorithm to transform the complex temperature control problem into a path optimization problem in graph theory. The optimal cooling path is solved with minimizing internal stress accumulation as the objective function. The closed-loop feedback mechanism of experiment and algorithm ensures the convergence and reliability of optimization results, and finally achieves the coordination of stress state at the two-phase interface, which significantly improves the interfacial bonding strength and the stability of the overall material performance.

[0061] The following provides a specific embodiment 1 of the present invention, and the specific implementation of each step in this embodiment 1 is described in detail below.

[0062] The specific implementation of step S01 is to first accurately weigh the hydrogenated styrene-butadiene block copolymer and the styrene-butadiene-styrene block copolymer according to a preset mass ratio. The mass ratio calculation formula is as follows:

[0063]

[0064] In the formula, R is the mass ratio of the two block copolymers, controlled within the range of 1 to 5; m SEBS-H The mass of the hydrogenated styrene-butadiene block copolymer is expressed in g; m SBS The mass of the styrene-butadiene-styrene block copolymer is given in grams. The amount of paraffin oil added is then calculated using the following formula for the mass fraction of paraffin oil:

[0065]

[0066] In the formula, w oil The mass fraction of paraffin oil is controlled within the range of 10% to 30%; m oil This represents the mass of paraffin oil, expressed in grams (g). Where m... SEBS-H and m SBS The weight was obtained by weighing using an electronic balance, with an accuracy of 0.01 g; m oil It is calculated based on the preset quality score.

[0067] The specific implementation of step S02 is based on establishing an interfacial tension prediction model using the Young-Dupre equation and Owens-Wendt theory. The specific expression of the Young-Dupre equation is as follows:

[0068]

[0069] In the formula, γ 12 γ1 represents the interfacial tension between polyethylene and polystyrene, in mN / m; γ2 and γ1 represent the surface tensions of polyethylene and polystyrene, respectively, in mN / m. and γ0 and γ1 represent the dispersive and polar components of the surface tension of polyethylene, respectively, in mN / m; γ2 and γ3 represent the dispersive and polar components of the surface tension of polystyrene, respectively, in mN / m. Considering the effect of compatibilizer concentration on interfacial tension, the corrected interfacial tension prediction equation is as follows:

[0070]

[0071] In the formula, The corrected interfacial tension prediction is expressed in mN / m; C comp The compatibilizer concentration is expressed in wt%; α and β are fitting coefficients, dimensionless. The parameters were obtained as follows: γ1 and γ2 were measured using a contact angle meter. The measurement steps included: Step 1: preparing a polymer film sample; Step 2: measuring the contact angle using deionized water and glycerol as probe liquids; Step 3: calculating the surface tension value according to the Young equation. The values ​​of α and β were obtained by the Owens-Wendt method; the range of α is 0.8 to 1.2 and the range of β is 0.05 to 0.15.

[0072] The specific implementation methods for steps S03-S05 are the same as those described above, and will not be repeated in detail here.

[0073] The specific implementation of step S06 is to first establish a multi-objective optimization model for the staged cooling temperature optimization experiment, with the objective function expression as follows:

[0074] F(T1, T2, t) c h)=w1·f1(D s )+w2·f2(σ b );

[0075] In the formula, F is the comprehensive objective function value; T1 is the first temperature, in °C; T2 is the second temperature, in °C; t c The cooling time is in minutes (min); h is the material thickness in mm; w1 and w2 are weighting coefficients, w1 + w2 = 1; f1(D s f2(σ) is the objective function for phase separation size; b The objective function for interfacial bonding strength is denoted as . The objective function for phase separation size is defined as:

[0076]

[0077] In the formula, D s The actual measured phase separation size, in μm; D s，target The target phase separation size is set to 1 μm. The objective function for interfacial bonding strength is defined as:

[0078]

[0079] In the formula, σ b The interfacial bonding strength is the actual measured value, in MPa; σ b，target The target interface bonding strength is set at 15 MPa. Based on the Dijkstra algorithm for shortest path calculation, the mathematical model expression for cooling path optimization is as follows:

[0080] d(v) = min{d(u) + w(u, v)};

[0081] In the formula, d(v) is the shortest distance from the initial temperature node to temperature node v, which is dimensionless; d(u) is the shortest distance from the initial temperature node to temperature node u, which is dimensionless; w(u, v) is the edge weight from temperature node u to temperature node v, representing the cumulative internal stress caused by temperature change, which is dimensionless; u and v represent the temperature node numbers in the cooling path diagram, obtained by discretizing continuous temperature intervals into nodes. The formula for calculating the cumulative internal stress is as follows:

[0082] σ internal =E·Δε=E·(α1-α2)·ΔT;

[0083] In the formula, σ internalInternal stress is expressed in MPa; E is the elastic modulus of the material, also in MPa; Δε is the strain difference, calculated using the formula Δε=(α1-α2)·ΔT, dimensionless; α1 and α2 are the coefficients of thermal expansion of polyethylene and polystyrene, respectively, in K. -1 ΔT represents the temperature change in Kelvin (K). The parameters were obtained as follows: the initial values ​​of T1 and T2 were determined through orthogonal experimental design, with experimental factor levels set as follows: T1: 60℃, 70℃, 80℃; T2: 20℃, 30℃, 40℃; D s σ was obtained by scanning electron microscopy. b The values ​​were obtained through tensile testing; E, α1, and α2 are inherent material parameters obtained through standard testing methods; the values ​​of w1 and w2 range from 0.4 to 0.6 and from 0.4 to 0.6, respectively.

[0084] The specific implementation method of step S07 is the same as described above, and will not be repeated in detail here.

[0085] The Young-Dupre equation is used to calculate the relationship between solid-liquid interfacial tension and surface tension. Input parameters include the surface tension values ​​of polyethylene (γ1), polystyrene (γ2), contact angle measurements, and temperature. The output parameter is the theoretical value of the interfacial tension, γ. 12 .

[0086] The Owens-Wendt equation is used to analyze the contribution of the dispersive and polar components of surface tension to interfacial tension. The input parameters include the polyethylene dispersive component. polar components of polyethylene polystyrene dispersion component polar components of polystyrene Compatibilizer concentration C comp The output parameter is the corrected predicted interfacial tension value. The corrected interfacial tension prediction value is used in step S02 to determine the optimal amount of compatibilizer.

[0087] The multi-objective optimization model in the staged cooling temperature optimization experiment uses the first temperature T1, the second temperature T2, and the cooling time t as the parameters. c Material thickness h is the input variable, and phase separation dimension D is the input variable. s and interface bonding strength σ b The response variable is solved by optimizing the comprehensive objective function F.

[0088] The shortest path algorithm constructs a weighted graph structure of temperature nodes in the cooling process, using the accumulated internal stress σ caused by the temperature difference as the basis for its calculation. internal Using the edge weights, the Dijkstra algorithm is used to solve for the optimal cooling path from the initial temperature to the target temperature, and the optimal cooling rate sequence is output.

[0089] Young-Dupre equations The principle is based on thermodynamic interface theory. By decomposing surface tension into dispersive and polar components, it can accurately describe the interfacial interactions between different polymers. Compared to the traditional Flory-Huggins theory, this equation can quantitatively calculate the absolute value of interfacial tension, providing a theoretical basis for compatibilizer selection and solving the problem of insufficient accuracy in interfacial tension prediction in existing technologies. The modified interfacial tension prediction equation... By introducing a quadratic correction term for the compatibilizer concentration This equation accurately reflects the nonlinear effect of compatibilizers on interfacial tension. Compared to the linear correction model, it improves prediction accuracy and enables precise control of compatibilizer dosage. The multi-objective optimization model F(T1, T2, t) c h)=w1·f1(D s )+w2·f2(σ b By unifying phase separation size and interfacial bonding strength into a single objective function, this model can simultaneously optimize the microstructure and macroscopic properties of materials. Compared to single-objective optimization methods, it avoids performance trade-offs during optimization, improving optimization efficiency and effectiveness. The Dijkstra shortest path algorithm, d(v) = min{d(u) + w(u, v)}, models the cooling process as a graph theory problem, finding the globally optimal cooling path in a complex multivariable space. Compared to traditional linear cooling methods, this algorithm considers the time difference between polyethylene crystallization and polystyrene curing, achieving coordinated matching of the two polymer solidification processes, fundamentally reducing internal stress generation and improving the overall material performance. The formula for calculating accumulated internal stress is σ. internal =E·(α1-α2)·ΔT Based on the theory of elasticity, by considering the difference between the elastic modulus and thermal expansion coefficient of the material (α1-α2), the stress distribution during the cooling process can be accurately predicted, providing a reliable weight basis for the optimization algorithm and ensuring the effectiveness of the cooling path optimization.

[0090] It should be noted that the variables involved in this invention are explained in detail in Table 1.

[0091] Table 1. Variable Explanation Table

[0092]

[0093]

[0094] To better understand and implement this invention, Example 2, a specific application scenario, is provided below: A technical R&D team addressed the interfacial cracking and mechanical property instability issues encountered in the practical application of polyethylene-polystyrene alloy materials for automotive parts by employing the interfacial compatibility improvement method of this invention. The core technical challenge faced by the team was that the interfacial bonding force between the polyethylene and polystyrene phases in existing alloy materials was insufficient under temperature changes and mechanical stress, leading to microcrack propagation and performance degradation during material use.

[0095] The technical team first prepared the compatibilizer premix masterbatch. Hydrogenated styrene-butadiene block copolymer with a molecular weight of 82,000 and styrene-butadiene-styrene block copolymer with a molecular weight of 75,000 were selected as compatibilizer components and formulated at a mass ratio of 3:1. During the formulation process, 24 kg of hydrogenated styrene-butadiene block copolymer and 8 kg of styrene-butadiene-styrene block copolymer were added to a 50 L high-speed mixing tank, followed by the addition of paraffin oil to 18% of the total mass fraction, i.e., 5.76 kg of paraffin oil. The mixture was stirred continuously for 4 minutes at a speed of 1500 rpm to obtain a uniform compatibilizer premix masterbatch with no obvious agglomeration. This premix masterbatch exhibited good flowability and dispersibility, laying the foundation for subsequent interfacial tension control.

[0096] Next, the technical team established an interfacial tension prediction model based on the Young-Dupre equation and Owens-Wendt theory. The surface tension parameters of polyethylene and polystyrene were measured using a contact angle meter. The surface tension of polyethylene was found to be 31.2 mN / m, with a dispersive component of 29.8 mN / m and a polar component of 1.4 mN / m; the surface tension of polystyrene was found to be 40.7 mN / m, with a dispersive component of 35.3 mN / m and a polar component of 5.4 mN / m. Based on these fundamental data, the interfacial tension variation under different compatibilizer concentrations was calculated using the interfacial tension calculation equations. The calculation results show that when the compatibilizer concentration is 7.5%, the PE / PS interfacial tension decreases from the original 12.3 mN / m to 4.8 mN / m, a reduction of 61%. Figure 2 As shown, the interfacial tension decreases sharply and then levels off as the compatibilizer concentration changes. When the compatibilizer concentration exceeds 8%, the rate of decrease in interfacial tension slows down significantly. Therefore, the optimal compatibilizer dosage is determined to be 7.5%.

[0097] In the multi-stage melt blending stage, the technical team used a twin-screw extruder with a length-to-diameter ratio of 40:1. The materials were formulated according to a mass fraction ratio of 42% polyethylene, 35% polystyrene, and 23% other additives. First, polyethylene and polystyrene matrix materials were fed into the first feeding port at a rate of 168 kg / h for polyethylene and 140 kg / h for polystyrene. Then, 30 kg / h of compatibilizer premixed masterbatch was precisely added into the second feeding port to ensure that the compatibilizer could participate in the interface construction process during the critical period of polymer interface formation. By precisely controlling the feeding sequence and amount at each feeding port, preferential distribution of the compatibilizer at the polymer interface was achieved, avoiding ineffective dispersion of the compatibilizer in the matrix.

[0098] The composite additive system was added at the third feeding port. The technical team selected talc powder with an average particle size of 2.5 μm as the inorganic powder, with a dosage of 12 kg / h, accounting for 3% of the total mass fraction. Simultaneously, a composite processing aid containing a primary antioxidant and a secondary antioxidant was added at 6 kg / h, accounting for 1.5% of the total mass fraction. The primary antioxidant was 2,6-di-tert-butyl-4-methylphenol, and the secondary antioxidant was tris(2,4-di-tert-butylphenyl) phosphite. The addition of talc powder not only acted as a nucleating agent, regulating the crystallization behavior of polyethylene, but also served as a heat stabilizer to improve the thermal stability of the material. The synergistic effect of the composite antioxidant system effectively protected the molecular structural stability of the interfacial region.

[0099] Precise control of melt extrusion process parameters has a significant impact on interfacial compatibility. The twin-screw extruder temperature was set using a segmented control method: the first to third segments were 175℃, 185℃, and 195℃, respectively; and the fourth to sixth segments were 190℃, 185℃, and 180℃, respectively. The screw speed was set to 250 r / min, and the material residence time in the extruder was controlled at 4.2 min. Through reasonable temperature gradient design and shear force control, the compatibilizer premix masterbatch was effectively dispersed and orderly oriented at the polyethylene and polystyrene interface.

[0100] The key technical aspects of this embodiment are the staged cooling temperature optimization experiment and the iterative optimization of the shortest path algorithm. The technical team first conducted an orthogonal experimental design, selecting the first initial temperature value, the second initial temperature value, the cooling time, and the material thickness as experimental factors, and setting the factor levels as shown in Table 1.

[0101] Table 2. Experimental Factor Levels for Optimizing Staged Cooling Temperature

[0102] Experimental factors Level 1 Level 2 Level 3 Level 4 Initial temperature value (°C) 45 55 65 75 Second initial temperature value (°C) 25 30 35 40 Cooling time (min) 8 12 16 20 Material thickness (mm) 2.0 3.0 4.0 5.0

[0103] Through L 16 (4 4An orthogonal experimental design was used to obtain 16 sets of experimental data. A multi-objective optimization model was established using phase separation size and interfacial bonding strength as response indicators. Experimental results show that relatively optimal experimental results were obtained when the initial temperature was 65℃, the second initial temperature was 30℃, the cooling time was 12 min, and the material thickness was 3.0 mm. Based on this, the shortest path algorithm was used to further optimize the cooling process. The temperature nodes in the cooling process were constructed as a weighted graph structure, with the temperature difference as the edge weight and minimizing the accumulation of internal stress as the objective function. Dijkstra's algorithm was used to solve for the optimal cooling path from the initial temperature of 195℃ to the target temperature of 25℃. The optimal cooling rate sequence was calculated to be 3.2℃ / min for the first stage, 1.8℃ / min for the second stage, and 0.9℃ / min for the third stage.

[0104] The algorithm's calculation results were fed back to the staged cooling temperature optimization experiment for the next round of experimental design. After three rounds of iterative optimization, the final staged cooling curing parameters were determined as follows: first temperature 68℃, second temperature 28℃, first-stage cooling rate 3.0℃ / min, and second-stage cooling rate 1.6℃ / min. Under these parameters, the extruded melt was first water-cooled to 68℃, and then air-cooled to 28℃, achieving a coordinated match between the polyethylene crystallization process and the polystyrene curing process. Figure 3 As shown, the optimized cooling curve can effectively reduce the internal stress generated during the cooling process and improve the stability of the interface bonding strength.

[0105] Interfacial compatibility was evaluated using scanning electron microscopy (SEM) to observe the cross-sectional morphology of the alloy material. The technical team prepared standard tensile specimens and observed their cross-sectional morphology after brittle fracture in liquid nitrogen. Statistical analysis of the SEM images was performed using image analysis software to determine the phase separation size and interfacial bonding strength. The optimized alloy material achieved a phase separation size of 0.73 μm, far less than the technical requirement of 1 μm; the interfacial bonding strength reached 18.6 MPa, exceeding the preset standard value of 15 MPa. Compared to the material before optimization, the phase separation size decreased by 42%, and the interfacial bonding strength increased by 31%.

[0106] Further performance tests showed that the PE / PS alloy material prepared using the method of this invention exhibited significant improvements in tensile strength, impact strength, and flexural strength. The tensile strength of the material reached 34.8 MPa, and the impact strength reached 15.2 kJ / m. 2The flexural strength reached 41.6 MPa. More importantly, the material exhibited excellent stability in temperature cycling tests, retaining over 95% of its mechanical properties after 100 cycles from -20°C to 80°C. Thermal aging tests showed that after aging at 80°C for 1000 hours, the interfacial bonding strength remained above 16.8 MPa, indicating that the composite additive system effectively protected the molecular structural stability of the interfacial region.

[0107] The technological advancements of this invention compared to traditional methods for improving interfacial compatibility are mainly reflected in three aspects. First, the interfacial tension prediction model based on the Young-Dupre equation and Owens-Wendt theory enables precise control of the compatibilizer dosage, overcoming the blindness of traditional empirical proportioning methods. By decomposing surface tension into dispersive and polar components, the interfacial interaction mechanism is revealed at the molecular level, providing a theoretical basis for the scientific design of compatibilizers. Second, the iterative optimization method using staged cooling temperature optimization experiments and shortest path algorithms solves the matching problem between the crystallization behavior of polyethylene and the curing process of polystyrene. Traditional uniform cooling methods cannot handle the differences in thermodynamic properties between the two polymers. This invention, through a combination of multi-objective optimization and graph theory algorithms, achieves precise control of the cooling process, effectively reducing stress concentration at the interface. Finally, the multi-stage melt blending process ensures the preferential interfacial distribution of the compatibilizer, avoiding the problems of compatibilizer agglomeration and uneven dispersion caused by traditional one-time addition methods. Through staged feeding and gradual mixing, the orderly arrangement of the compatibilizer in the interfacial structure is achieved, significantly improving the compatibility efficiency and the consistency of interfacial bonding strength.

[0108] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the interface compatibility between PE and PS, characterized in that, include: To prepare a compatibilizer premixed masterbatch, hydrogenated styrene-butadiene block copolymer and styrene-butadiene-styrene block copolymer were mixed, paraffin oil was added, and the mixture was stirred in a high-speed mixing pot to form a uniform compatibilizer premixed masterbatch. An interfacial tension prediction model was established to measure the surface tension parameters of polyethylene and polystyrene, calculate the interfacial tension values ​​at different compatibilizer concentrations, and determine the optimal compatibilizer dosage to reduce the interfacial tension to a preset threshold range. Multi-stage melt blending was performed, with polyethylene and polystyrene fed into a twin-screw extruder at the first feeding port and compatibilizer premix masterbatch added at the second feeding port to ensure preferential distribution of the compatibilizer premix masterbatch at the polymer interface. A composite additive system was added, with inorganic powder and processing aids added at the third feeding port. Melt extrusion process parameters were controlled, setting the twin-screw extruder temperature and screw speed to promote the dispersion and orientation of the compatibilizer premix masterbatch at the polyethylene and polystyrene interface through shear force. Staged cooling and solidification parameters were determined through staged cooling temperature optimization experiments and iterative optimization using the shortest path algorithm, and the extruded melt was subjected to water cooling at the first temperature and air cooling at the second temperature. Interfacial compatibility was evaluated.

2. The method for improving the interface compatibility of PE and PS according to claim 1, characterized in that, The specific steps for preparing the compatibilizer premixed masterbatch are as follows: hydrogenated styrene-butadiene block copolymer and styrene-butadiene-styrene block copolymer are mixed at a mass ratio of 1 to 5:1, paraffin oil is added to 10% to 30% of the total mass fraction, and the mixture is stirred in a high-speed mixing pot for 3 to 5 minutes to form a uniform compatibilizer premixed masterbatch.

3. The method for improving the interface compatibility of PE and PS according to claim 2, characterized in that, The hydrogenated styrene-butadiene block copolymer refers to a styrene-butadiene block copolymer that has undergone hydrogenation treatment, possesses good thermal stability and compatibility with polyethylene, and has a molecular weight in the range of 50,000 to 150,000.

4. The method for improving the interface compatibility of PE and PS according to claim 3, characterized in that, The styrene-butadiene-styrene block copolymer refers to a triblock copolymer with styrene as the end segment and butadiene as the middle segment.

5. The method for improving the interface compatibility of PE and PS according to claim 4, characterized in that, The steps for establishing the interfacial tension prediction model are specifically based on the Young-Dupre equation and the Owens-Wendt theory.

6. The method for improving the interface compatibility of PE and PS according to claim 5, characterized in that, The multi-stage melt blending refers to setting multiple feed ports at different screw positions in a twin-screw extruder to achieve segmented addition and gradual mixing of components.

7. The method for improving the interface compatibility of PE and PS according to claim 6, characterized in that, The step of multi-stage melt blending is specifically to add polyethylene and polystyrene into the twin-screw extruder at the first feeding port according to a mass fraction ratio of 30-50% polyethylene and 20-40% polystyrene.

8. The method for improving the interface compatibility of PE and PS according to claim 7, characterized in that, The composite additive system includes a combination of inorganic powder nucleating agent and organic antioxidant. The inorganic powder is talc or calcium carbonate with a particle size in the range of 1 to 5 μm. The main antioxidant is a hindered phenolic compound, and the auxiliary antioxidant is a phosphite compound.

9. The method for improving the interface compatibility of PE and PS according to claim 8, characterized in that, The step of adding the composite additive system specifically involves adding 1-5% inorganic powder and 0.5-2% processing aid at the third feeding port.

10. The method for improving the interface compatibility of PE and PS according to claim 9, characterized in that, The steps for controlling the melt extrusion process parameters specifically involve setting the twin-screw extruder temperature to 170–200°C, the screw speed to 200–300 r / min, and the residence time to 3–5 min.

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