A blow molding method for composite toughened films

Abstract

This invention relates to the field of polymer material processing technology, and more particularly to a blow molding method for a composite toughened film, comprising: Step 1: preheating the matrix resin in a preheating device; Step 2: feeding the mixed raw materials into a twin-screw extruder for melt blending; Step 3: feeding the dried composite granules into the hopper of a single-screw blow extruder; Step 4: adjusting the airflow and air pressure of the cooling system according to monitoring results; Step 5: folding the formed film tube into a flat shape through a guide component, leading it out through a traction roller, coordinating the traction speed with the extrusion speed to control the traction ratio, corona treatment of the film surface to improve surface energy, and then controlling the winding tension for winding, the winding tension being controlled according to the elasticity and thickness of the film to prevent excessive stretching or relaxation. The uniform distribution and appropriate compatibility of the composite toughening components improve the toughness of the film while maintaining its strength and barrier properties.

Description

Technical Field

[0001] This invention relates to the field of polymer material processing technology, and in particular to a blow molding method for composite toughened films. Background Technology

[0002] Plastic films have a wide range of applications in packaging, agriculture, medical, and electronics. As these applications continue to expand, the requirements for film performance are also increasing. Traditional single-material films often struggle to simultaneously meet the requirements of high strength, high toughness, and high barrier properties. This is especially true in specialized applications such as heavy-duty packaging, protective materials, and high-end electronic packaging, where ordinary films are prone to brittle fractures and puncture damage.

[0003] Currently, commonly used toughening methods in the market mainly include adding plasticizers, elastomers, and nanofillers. While adding plasticizers can improve the flexibility of the film, it often significantly reduces the film's strength and heat resistance, and plasticizers may migrate to the film surface, affecting the product's appearance and safety. When improving toughness by adding elastomers, the poor compatibility between the elastomer and the matrix resin can easily lead to phase separation, resulting in uneven mechanical properties and surface defects in the film. Adding nanofillers presents dispersion challenges; nanoparticles tend to aggregate, forming stress concentration points in the matrix, which conversely reduces the overall performance of the film.

[0004] In blow molding processes, existing technologies primarily focus on improving single properties, lacking synergistic control over multi-level structures. Traditional blow molding process parameters, such as blow ratio, draw ratio, and cooling rate, are often controlled independently, making it difficult to achieve a coordinated balance between the film's microstructure and macroscopic properties. Particularly in composite toughening systems, different toughening components have varying requirements for the blow molding process. Conventional process conditions cannot simultaneously satisfy the processing characteristics of multiple toughening components, resulting in composite toughening effects far below theoretical expectations.

[0005] Furthermore, existing blow molding equipment lacks dedicated designs for composite toughening systems. During film forming, the rheological behavior of the melt is influenced by multiple components, and traditional die designs and cooling systems struggle to achieve precise control of melt flow, affecting film thickness uniformity and performance consistency. While patent databases contain improvements to blow molding equipment, such as guide component designs, they do not address the issue of multi-layered structure formation in composite toughening systems.

[0006] Therefore, there is an urgent need to develop a dedicated blow molding method for composite toughening systems that can coordinate and control the distribution and orientation of multiple toughening components during the molding process, so as to achieve a significant improvement in film toughness without sacrificing other properties. Summary of the Invention

[0007] To achieve the above objectives, the present invention provides a blow molding method for composite toughened films, comprising the following steps:

[0008] Step 1: Preheat the matrix resin in a preheating device. The preheating temperature is controlled within the range of above the glass transition temperature of the matrix resin and below the melting point of the matrix resin. During the preheating process, the matrix resin is continuously stirred. Then, the preheated matrix resin and the composite toughening component are mixed in a dry mixing device in a specific ratio. The mixing time is used to ensure that the components are evenly distributed. The composite toughening component includes nano-sized inorganic fillers, elastomer particles and interface compatibilizers.

[0009] Step 2: The mixed raw materials are fed into a twin-screw extruder for melt blending. The temperature of the twin-screw extruder is controlled in zones, forming a gradually increasing temperature gradient from the feed inlet to the die. The screw speed is controlled to ensure that the composite toughening components are fully dispersed in the matrix resin without degradation. The melt-blended material is made into uniform particles by an underwater pelletizing device, and then the particles are vacuum dried to remove the absorbed moisture.

[0010] Step 3: Feed the dried composite granules into the hopper of the single-screw blow extruder, adjust the gap of the blow die to match the expected film thickness. The blow die is equipped with a fluid distribution channel, which enables the melt to generate a multi-layer alternating distribution structure during the flow process. Install and adjust the guide component, which has an arc-shaped contact surface and is made of a breathable material.

[0011] Step 4: Start the single-screw blow extruder, adjust the temperature control system to the predetermined process parameters, extrude the melt from the die to form a tube blank, introduce compressed air into the tube blank to inflate the tube blank to form a film tube, control the inflation pressure according to the required fold diameter and thickness of the film and monitor and adjust it in real time through a pressure sensor, monitor the temperature distribution of the film tube in real time through an infrared temperature measuring device, and adjust the air volume and air pressure of the cooling system according to the monitoring results.

[0012] Step 5: The formed film tube is folded into a flat shape by the guide component and led out by the traction roller. The traction speed is coordinated with the extrusion speed to control the traction ratio. The film surface is corona treated to improve the surface energy. Then, the winding tension is controlled to wind the film. The winding tension is controlled according to the elasticity and thickness of the film to prevent excessive stretching or slack.

[0013] Preferably, in step 1, the particle size distribution of the nano-sized inorganic filler is determined and controlled within a specific range using a laser particle size analyzer; the hardness of the elastomer microparticles is lower than that of the matrix resin and is determined using an indentation hardness tester; the molecular structure of the interface compatibilizer contains functional groups capable of interacting with both the matrix resin and the toughening component simultaneously, and the type of functional group is determined by infrared spectroscopy analysis; the ratio of the nano-sized inorganic filler, elastomer microparticles, and interface compatibilizer is adjusted according to the final film thickness and application requirements, and the adjustment process is based on calculations of the expected impact strength and elongation at break of the film; the mixing speed of the dry mixing equipment is determined by monitoring the uniformity of the mixture, and the uniformity is evaluated by sampling and testing the consistency of the distribution of each component.

[0014] Preferably, in step 1, the specific range of the preheating temperature is determined by the thermal analysis curve of the matrix resin, which is obtained by differential scanning calorimetry; the stirring speed during the preheating process is adjusted according to the particle size and flowability of the matrix resin, and the stirring speed is based on ensuring that the matrix resin is heated uniformly and does not clump; the mixing time is monitored by the power consumption curve in the dry mixing equipment, and when the power consumption is stable, it indicates that the mixing is uniform; the specific proportion of the composite toughening component is determined by preliminary experiments, which include preparing samples with different proportions and testing the mechanical properties of the film.

[0015] Preferably, in step 2, the temperature zone control of the twin-screw extruder includes a feeding zone, a melting zone, a mixing zone, and a die zone. The temperature settings of each zone are determined based on the thermal stability of the composite toughening system, which is measured by a thermogravimetric analyzer. The slope of the temperature gradient is calculated based on the melting characteristics of the matrix resin and the toughening component to ensure that the melt does not degrade. The screw speed is adjusted according to the viscosity change of the melt, and the viscosity is monitored by an online viscometer. The water temperature of the underwater pelletizing device is controlled below the glass transition temperature of the matrix resin to prevent particle adhesion. The vacuum degree and time of the vacuum drying are adjusted according to the moisture content of the particles, which is detected in real time by a moisture meter.

[0016] Preferably, in step 3, the gap of the blow molding die is calculated using a film thickness prediction model, which is based on melt flowability and blow-up ratio; the fluid distribution channel design includes multiple flow-dividing units, the geometry of which is optimized through computational fluid dynamics simulation to ensure that the melt produces a multi-layered alternating distribution structure; the radius of curvature of the arc-shaped contact surface of the guide component is determined according to the diameter of the membrane tube, and the radius of curvature is calculated through geometric relationships; the permeability of the breathable material is determined through material pore size distribution testing, and the permeability is based on ensuring that the membrane tube folds smoothly without wrinkles; the angle and position of the guide component are finely adjusted by simulating the motion trajectory of the membrane tube.

[0017] Preferably, in step 4, the predetermined process parameters of the temperature control system are determined by melt flow index testing, which is conducted at different temperatures; the blowing pressure is controlled based on the fold diameter and thickness requirements of the film, and the flow rate of compressed air is adjusted by feedback from a pressure sensor; the monitoring points of the infrared temperature measuring device are evenly distributed along the circumference of the film tube, and the number of monitoring points is determined according to the size of the film tube; the air volume and air pressure of the cooling system are adjusted based on the change in the position of the condensation line, and the position of the condensation line is determined by image processing captured by the infrared temperature measuring device; online monitoring also includes thickness uniformity detection, which is measured in real time by a laser thickness gauge, and the die head gap or traction speed is adjusted according to the measurement results.

[0018] Preferably, in step 4, the temperature distribution monitoring of the membrane tube includes real-time analysis of the height and shape of the condensation line, with the condensation line height identified by the inflection point of the temperature distribution curve; the airflow and air pressure adjustment of the cooling system adopt closed-loop control, and the setpoint of the closed-loop control is calculated based on the cooling rate requirement of the membrane, which is determined based on the crystallization behavior of the composite toughening system; the real-time monitoring of the inflation pressure includes pressure fluctuation analysis, with pressure fluctuations processed by a filtering algorithm to ensure control stability; the temperature of the compressed air is controlled below the ambient temperature to prevent premature cooling of the membrane tube, and the air temperature is regulated by a heat exchanger.

[0019] Preferably, in step 5, the coordination between the traction speed and the extrusion speed is controlled by a speed ratio, which is calculated based on the longitudinal orientation requirements of the film and determined through pre-experiments; the power of the corona treatment is adjusted according to the surface energy requirements of the film, which are evaluated by a contact angle measuring instrument; the control of the winding tension is based on the elastic modulus of the film, which is obtained through a tensile test; during the winding process, a tension sensor is used to monitor the tension change in real time, and the torque of the winding roller is adjusted by a PID controller; the elasticity of the film is verified by a stress-strain curve, which is determined by a universal testing machine.

[0020] Preferably, in step 5, the electrode spacing for corona treatment is adjusted according to the film thickness and material, and the electrode spacing is determined by a breakdown voltage test; the corona treatment speed is synchronized with the traction speed to ensure uniform treatment; the control of winding tension also includes inertia compensation, which is calculated based on the diameter change of the winding roller; the wound film undergoes aging treatment, and the aging treatment time is determined based on the internal stress relaxation characteristics of the film, which are obtained through stress relaxation experiments; the final performance of the film is verified by impact testing and tear testing, with test samples taken from different locations on the film.

[0021] Preferably, in steps 1 to 5, all process parameter adjustments are based on real-time data feedback, including temperature, pressure, speed, and tension. The data feedback system employs an industrial IoT platform, which integrates sensor data and control algorithms. The parameters of the control algorithm are optimized through a machine learning model, which is trained based on historical production data. The film's quality indicators are monitored online, including thickness uniformity, surface defects, and mechanical properties, and are predicted and adjusted using a digital twin model. The entire method is implemented automatically by a programmable logic controller (PLC), whose program is customized according to the film's specifications.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention employs a composite toughening system that can coordinate and control the distribution and orientation of toughening components during the molding process, thereby improving the toughness of the film without sacrificing its strength and barrier properties. This improvement enables the film to exhibit excellent mechanical properties in applications such as heavy-duty packaging, protective materials, and high-end electronic packaging, effectively avoiding the problems of brittle fracture and puncture damage that are common in traditional films.

[0024] 2. This invention optimizes the molding process of the composite toughening system, avoiding the problem of traditional plasticizers reducing film strength and heat resistance while improving flexibility. Simultaneously, addressing the issues of poor compatibility between the elastomer and the matrix resin, and poor dispersion of nanofillers, this invention achieves the synergistic effect of multiple toughening components, avoiding phase separation and agglomeration, ensuring uniform mechanical properties of the film, and reducing surface defects.

[0025] 3. This invention innovatively designs a blow molding process capable of synergistically controlling multi-layered structures. Traditional blow molding process parameters are usually controlled independently, failing to meet the processing requirements of different toughening components. However, this invention achieves a coordinated unity of film microstructure and macroscopic properties by precisely controlling process parameters such as blow ratio, traction ratio, and cooling rate, significantly improving the composite toughening effect.

[0026] 4. The dedicated blow molding equipment design of this invention can precisely control the melt flow behavior according to the specific requirements of the composite toughening system, overcoming the problem of traditional die design and cooling system's difficulty in controlling melt flow. This technological improvement effectively ensures film thickness uniformity and performance consistency, while ensuring the uniform distribution and orientation of toughening components, thus improving the overall performance of the film. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0028] Figure 1 This is a flowchart of the steps of the method of the present invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0030] Please see Figure 1 This invention provides a blow molding method for a composite toughened film. In step 1, the base resin is first preheated in a preheating device to ensure that the preheating temperature is above the glass transition temperature of the base resin but below its melting point. Continuous stirring ensures uniform heating of the resin, avoiding localized overheating or degradation. Subsequently, the preheated base resin is mixed with composite toughening components (including nano-sized inorganic fillers, elastomer particles, and interfacial compatibilizers) in a specific ratio. A dry mixing device ensures sufficient and uniform distribution of each component by maintaining an appropriate mixing time, avoiding uneven dispersion or aggregation of the toughening components. This step ensures the effective participation of the toughening components, which is beneficial for improving the mechanical properties and toughness of the film during subsequent molding.

[0031] In step 2, the mixed raw materials are fed into a twin-screw extruder for melt blending. The temperature gradient in the twin-screw extruder gradually increases from the feed inlet to the die. Precise temperature zoning ensures the homogeneity of the melt and the full integration of the toughening components. Screw speed control prevents the degradation of the toughening components, ensuring their effective performance. The melt-blended material is then cut into uniform particles by an underwater pelletizer to ensure particle uniformity. Subsequently, vacuum drying removes moisture to prevent residual moisture from affecting subsequent processes and film quality.

[0032] In step 3, the dried composite granules enter the hopper of a single-screw blow extruder and undergo melt extrusion within the blow die. The die gap is precisely adjusted to match the desired film thickness. Fluid distribution channels within the die facilitate the formation of a multi-layered, alternating structure during melt flow, a design that enhances the film's mechanical properties and toughness. The guide members, with their curved contact surfaces and made of permeable material, effectively control melt flow and guide its stable expansion during molding, preventing uneven melt stretching.

[0033] In step 4, the melt is extruded from the die using a single-screw extruder to form a preform. Compressed air is then introduced into the preform to expand it into a film tube. The inflation pressure is precisely controlled according to the required film diameter and thickness, and is monitored in real time by a pressure sensor to maintain pressure stability. An infrared thermometer is used to monitor the temperature distribution of the film tube, ensuring that it remains at the optimal temperature during the forming process and avoiding performance fluctuations caused by uneven temperature. Based on the temperature measurement results, the airflow and pressure of the cooling system can be adjusted in real time to ensure uniform cooling of the film and the quality of the forming process.

[0034] In step 5, the formed film tube is folded into a flat shape by the guide member and then led out by the traction roller. The coordination between the traction speed and the extrusion speed ensures accurate control of the traction ratio, avoiding excessive stretching or slack in the film. Corona treatment improves the surface energy of the film, making the film surface more suitable for subsequent printing or other processing. Finally, precise control of the winding tension prevents the film from stretching or slackning during the winding process, thereby ensuring the quality stability of the final product.

[0035] The uniform distribution and appropriate compatibility of the composite toughening components improve the toughness of the film while maintaining its strength and barrier properties, meeting the requirements of demanding applications. Secondly, precise control of process parameters at each molding stage, such as temperature, pressure, and traction speed, ensures the uniformity and consistency of film performance, avoiding the performance inhomogeneities and defects commonly found in traditional methods. Finally, optimized blow molding equipment and processes improve production efficiency and ensure controllable and stable product quality.

[0036] In one possible implementation, the particle size distribution of the nanoscale inorganic filler is first precisely measured using a laser particle size analyzer. The particle size is controlled within a specific range to ensure uniform dispersion of the filler in the resin matrix and improve the mechanical properties of the film, particularly in enhancing impact resistance and the rigidity of the material. The laser particle size analyzer can accurately determine the particle size distribution, ensuring that the size of each particle is controlled within the desired range, avoiding fluctuations in mechanical properties caused by excessively large or small particles.

[0037] The hardness of the elastomer microparticles is lower than that of the matrix resin. The hardness of the elastomer microparticles is measured using an indentation hardness tester to ensure they provide appropriate toughness within the film, thereby improving the film's impact strength and ductility. Hardness control is crucial; excessive hardness may increase the film's brittleness, while insufficient hardness may affect its tensile strength and abrasion resistance. Precise hardness control allows for a good balance within the film, resulting in high impact resistance and appropriate elongation during use.

[0038] The molecular structure of interfacial compatibilizers is designed to include functional groups that can interact with both the matrix resin and the toughening component simultaneously. These functional groups are identified through infrared spectroscopy analysis. Interfacial compatibilizers can effectively improve the compatibility between the resin and the toughening component, reduce interfacial tension, and promote their interaction, thereby improving the overall performance of the film, including impact resistance, aging resistance, and mechanical properties.

[0039] Regarding the raw material formulation, the proportions of nanoscale inorganic fillers, elastomer microparticles, and interfacial compatibilizers are adjusted according to the final film thickness and application requirements. The specific adjustment process is based on the expected impact strength and elongation at break of the film, both of which directly affect the film's actual performance in applications. For example, for films requiring higher impact strength, the proportion of elastomer microparticles may need to be increased, while for films requiring higher rigidity, the proportion of nanoscale inorganic fillers may need to be increased.

[0040] The mixing speed of the dry mixing equipment also needs to be monitored and adjusted according to the uniformity of the mixture. By sampling and testing the distribution consistency of each component, the uniformity of the mixture can be assessed, ensuring that each toughening component is evenly distributed in the matrix resin. This avoids the problem of local concentrations being too high or too low during subsequent melt blending, thus ensuring the uniformity of film performance.

[0041] By precisely controlling the properties and proportions of each component, better mechanical properties can be achieved in the film, particularly in terms of impact strength and elongation at break. Furthermore, optimizing the mixing process can effectively improve the uniformity and stability of the film, thereby ensuring its high reliability and durability in practical applications.

[0042] In one possible implementation, the preheating temperature is first determined using a thermal analysis profile of the base resin. This profile is measured using a differential scanning calorimeter (DSC), an instrument that accurately reflects the thermal behavior of the material at different temperatures, helping to determine the resin's glass transition temperature and melt temperature range. By analyzing these thermal characteristics, a suitable preheating temperature can be selected, ensuring that the resin does not overheat during preheating, leading to performance degradation, while also avoiding excessively low temperatures that could affect subsequent molding processes.

[0043] The stirring speed during preheating is adjusted according to the particle size and flowability of the base resin. The purpose of the stirring speed is to ensure that the base resin is heated evenly and to avoid agglomeration. Resins with larger particle sizes may require a lower stirring speed to avoid particle collisions and agglomeration; while resins with better flowability can have a higher stirring speed to ensure uniform heating and promote the smooth melting process of the resin.

[0044] Controlling the mixing time also plays a crucial role in this method. By monitoring the power consumption curve in the dry mixing equipment, the uniformity of the mixing process can be monitored in real time. When the power consumption curve stabilizes, it indicates that the components have been fully and uniformly mixed, reaching the ideal state. The stability of power consumption reflects the completeness of the mixing process, which is an important basis for ensuring the consistency of the final film quality.

[0045] The specific ratio of the composite toughening components is determined through preliminary experiments. These experiments involve preparing samples with different ratios of toughening components and determining the optimal ratio by testing the mechanical properties of the film (such as impact resistance and tensile strength). Through repeated experimental optimization, the most suitable ratio of toughening components can be found to obtain a composite film with excellent performance.

[0046] By precisely controlling the preheating temperature, stirring speed, and mixing time, the uniformity of the base resin during preheating and mixing can be ensured, which is crucial for the subsequent blow molding process. Simultaneously, the optimal proportions of the composite toughening components, confirmed through pre-experiments, enable the film to achieve an optimal balance in mechanical properties, enhancing its overall impact resistance, tensile strength, and other key characteristics, thereby improving its reliability and durability in practical applications.

[0047] In one possible implementation, the extruder's temperature zones mainly include a feeding zone, a melting zone, a mixing zone, and a die zone. The temperature setting of each zone must be adjusted based on the thermal stability of the composite toughening system. Thermal stability is determined using a thermogravimetric analyzer (TGA), which reveals the temperature range at which the material loses mass due to thermal degradation during heating, thus providing a reliable basis for setting the temperature zones. By precisely controlling the temperature of each zone, thermal degradation of the material during extrusion can be avoided, ensuring high-quality films during the forming process.

[0048] Regarding the setting of the temperature gradient, the slope of the temperature gradient is calculated based on the melting characteristics of the matrix resin and the toughening component. A reasonable temperature gradient helps to achieve smooth melt flow and avoids degradation or crystallization of the melt due to excessively rapid temperature changes during the flow process. This temperature control method ensures the physical properties and chemical stability of the composite toughened film during the molding process.

[0049] The screw speed is adjusted based on the viscosity changes of the melt. Viscosity is monitored in real time using an online viscometer to ensure that the screw speed matches the melt flowability under different temperatures and pressures, preventing uneven flow or material waste caused by excessively high or low melt viscosity. Appropriate screw speed helps ensure uniform mixing of the melt during extrusion, fully utilizing the toughening components and thus improving the mechanical properties of the film.

[0050] Temperature control is crucial during underwater pelleting. The water temperature must be maintained below the glass transition temperature of the matrix resin to prevent pellet sticking during cooling. Excessive water temperature can cause the resin pellets to soften or stick together, affecting pellet flowability and subsequent processing. Therefore, maintaining an appropriate water temperature ensures smooth pelleting and pellet integrity.

[0051] Finally, the vacuum level and drying time during the vacuum drying process also need to be adjusted according to the moisture content of the particles. Real-time monitoring of the moisture content is performed using a moisture analyzer to ensure precise control of the drying process. Excessively high or low moisture content can adversely affect subsequent extrusion and blow molding processes; therefore, controlling the moisture content is crucial to ensuring the quality of the composite toughened film.

[0052] Through these meticulous process controls, the composite toughened film achieves optimal physical properties and processing stability during the molding process, thereby improving the film's durability, impact resistance, and overall mechanical properties. The embodiments of this invention can significantly enhance the quality and application performance of the composite toughened film, meeting more demanding industrial requirements.

[0053] In one possible implementation, the die gap is first calculated using a film thickness prediction model. This model, based on melt flowability and blow-up ratio, predicts the relationship between the die gap and the final film thickness by simulating melt behavior under different flow conditions. This prediction model helps to accurately set the die gap, thereby ensuring film thickness uniformity and avoiding uneven thickness or surface defects.

[0054] Next, the design of the fluid distribution channel is crucial. Multiple flow-dividing units are incorporated within the channel, their geometry optimized using computational fluid dynamics (CFD) simulation. This optimization aims to ensure the melt is uniformly distributed as it passes through the die, forming a multi-layered, alternating distribution structure. This multi-layered, alternating distribution structure helps improve the mechanical properties and uniformity of the film, avoiding film defects caused by fluid inhomogeneity. CFD simulation can accurately simulate the melt flow process, optimizing melt distribution by adjusting the shape and size of the flow-dividing units, thereby improving production efficiency and product quality.

[0055] In the design of the guide component, the radius of curvature of the arc-shaped contact surface is determined based on the diameter of the membrane tube. The radius of curvature is calculated using geometric relationships to ensure a reasonable contact angle and pressure between the contact surface and the membrane tube, thereby avoiding unevenness or instability of the membrane tube during the molding process. By optimizing the design of the radius of curvature, it is possible to ensure that the membrane tube maintains a stable shape during blow molding, reducing film defects caused by uneven stretching or excessive bending during the molding process.

[0056] Furthermore, the air permeability of the breathable material is determined through pore size distribution testing. Controlling the air permeability is crucial because it ensures the membrane tube folds smoothly without wrinkles during the forming process. Excessive or insufficient air permeability will affect the forming quality of the membrane tube, resulting in an uneven surface or unnecessary defects. Therefore, the pore size distribution and air permeability of the breathable material must be precisely controlled to ensure smooth membrane tube forming.

[0057] Finally, the angle and position of the guide component are fine-tuned by simulating the movement trajectory of the membrane tube. This precise adjustment ensures that the membrane tube moves smoothly along the predetermined trajectory during blow molding, thereby avoiding deformation or uneven stretching of the membrane tube due to deviations in the movement trajectory.

[0058] By precisely controlling the blow molding die gap, optimizing the fluid distribution channel, accurately calculating the radius of curvature of the guide component, finely controlling the air permeability of the breathable material, and micro-adjusting the angle and position of the guide component, the uniformity, stability, and excellent mechanical properties of the composite toughened film can be ensured. These optimization measures not only improve the quality and production efficiency of the film but also effectively avoid common defects in the production process, such as wrinkles and uneven thickness.

[0059] In one possible implementation, the predetermined process parameters of the temperature control system are first determined by melt flow index testing. Melt flow index testing is conducted at different temperatures to accurately assess the melt's fluidity at specific temperatures. Melt flow index reflects the material's flow properties and directly affects the film forming process. Analyzing the results of melt flow index tests at different temperatures provides a basis for adjusting the temperature control system, ensuring that the melt flow is ideal throughout the blow molding process, thereby avoiding situations where the melt is too viscous or has poor flowability.

[0060] The blow-blowing pressure is controlled by adjusting the required fold diameter and thickness of the film. Fold diameter and thickness are key factors determining film quality, and the blow-blowing pressure is precisely controlled by using a pressure sensor to provide real-time feedback on the compressed air flow. Appropriate blow-blowing pressure ensures the film unfolds uniformly during the blow molding process, achieving the desired thickness and dimensional requirements, thereby guaranteeing the film's mechanical properties and appearance quality.

[0061] The infrared temperature measurement device is used to monitor the temperature of the membrane tube in real time. Monitoring points are evenly distributed along the circumference of the membrane tube, and the number of monitoring points is determined by the size of the membrane tube to ensure comprehensive monitoring of the temperature distribution throughout the entire circumference. Real-time temperature monitoring effectively controls the temperature uniformity of the membrane tube during the forming process, avoiding film defects such as wrinkles or irregular deformation caused by uneven temperature.

[0062] The airflow and air pressure of the cooling system also need to be adjusted according to the changes in the position of the condensation line. The position of the condensation line is determined by image processing captured by an infrared thermometer. Image processing technology can accurately locate the position of the condensation line, thereby enabling precise adjustment of the airflow and air pressure of the cooling system. Controlling the position of the condensation line ensures that the film can shrink uniformly during the cooling stage, avoiding internal stress imbalance caused by uneven cooling, and further ensuring the quality stability of the film.

[0063] In addition, the online monitoring system includes thickness uniformity detection. By measuring the film thickness uniformity in real time using a laser thickness gauge, even minute changes in film thickness can be accurately detected. If the thickness is uneven, the system will automatically adjust the die gap or traction speed based on the measurement results to ensure film thickness uniformity. This precise online monitoring and real-time adjustment allows for timely correction of any potential quality issues during the blow molding process, further improving film consistency and production efficiency.

[0064] The combination of temperature control, blow-up pressure regulation, cooling system adjustment, and online monitoring not only improves the precision of composite toughened film blow molding but also effectively ensures film quality. Through these technical means, film thickness uniformity, temperature control accuracy, and surface quality are effectively guaranteed, ultimately achieving stable production of high-performance films. These optimization measures significantly enhance the automation level of the production process and the consistency of film products, meeting high-standard industrial requirements.

[0065] In one possible implementation, monitoring the temperature distribution within the membrane tube first requires real-time analysis of the height and shape of the condensation line. This process is achieved by identifying the inflection points of the temperature distribution curve. The height of the condensation line reflects the position where the melt gradually solidifies during the film cooling process, and accurately identifying changes in the condensation line is crucial for film forming quality. By identifying the inflection points of the temperature distribution curve, the position and morphological changes of the condensation line can be determined in real time, thereby further guiding the adjustment of the cooling system.

[0066] The cooling system employs closed-loop control to ensure the accuracy and stability of temperature control. The setpoints for the closed-loop control are calculated based on the required cooling rate of the thin film. This required cooling rate stems from the crystallization behavior of the composite toughening system. Crystallization behavior significantly impacts the physical properties of the thin film (such as transparency and strength), therefore, the cooling rate must be precisely controlled according to the specific material characteristics. By calculating the required cooling rate, the closed-loop control automatically adjusts the airflow and air pressure of the cooling system, thereby precisely controlling the cooling process of the thin film and avoiding defects caused by excessively fast or slow cooling.

[0067] Furthermore, real-time monitoring of the blow-up pressure is also a crucial component of this method. By analyzing pressure fluctuations, the stability of the pressure during the blow molding process can be monitored in real time. Pressure fluctuations often lead to uneven film thickness or molding defects. Therefore, processing pressure fluctuations using filtering algorithms can effectively remove unwanted noise and ensure stable control of the blow-up pressure. This refined pressure fluctuation analysis helps maintain the stability of the molding process, thereby improving film quality.

[0068] For compressed air temperature control, it needs to be maintained below ambient temperature to prevent premature cooling of the membrane tube during the forming process. Premature cooling will result in incomplete melt formation, affecting the uniformity and mechanical properties of the film. Therefore, the air temperature is regulated through a heat exchanger to ensure that the compressed air temperature is stable within a suitable range, avoiding the impact of temperature fluctuations on membrane tube forming.

[0069] The embodiments of this invention ensure the coordinated control of temperature, cooling rate, and blow-up pressure during the blow molding process of composite toughened films, thereby improving the quality stability of the films. Closed-loop control systems, pressure fluctuation analysis, and compressed air temperature regulation ensure that every step of the blow molding process is in optimal working condition, further enhancing film performance and production efficiency.

[0070] In one possible implementation, to ensure the longitudinal orientation of the film meets requirements during the molding process, the coordination between the traction speed and the extrusion speed is controlled by a speed ratio. The speed ratio is set based on the longitudinal orientation requirements of the film, which are determined through preliminary experiments. After determining the optimal longitudinal orientation angle using experimental data, the ideal longitudinal orientation can be achieved by adjusting the speed ratio, thereby optimizing the mechanical properties of the film, such as tensile strength and impact resistance.

[0071] Furthermore, corona treatment plays a crucial role in adjusting the surface energy of thin films. The power of the corona treatment needs to be adjusted according to the required surface energy of the film. The surface energy of the film is assessed using a contact angle meter. By measuring the contact angle of the film surface, its surface energy can be evaluated. Higher surface energy results in better film adhesion and printability. Therefore, by adjusting the power of the corona treatment, the surface energy of the film can be precisely controlled to meet the requirements of subsequent processing.

[0072] Tension control during the winding process is crucial for ensuring the morphological stability of the film. Winding tension control is based on the film's elastic modulus. The elastic modulus is obtained through tensile testing, which directly reflects the material's deformation and recovery ability under stress. By understanding the film's elastic modulus, appropriate tension can be adjusted during winding to prevent deformation or quality problems caused by excessive or insufficient tension.

[0073] During the winding process, a tension sensor monitors tension changes in real time, and a PID controller adjusts the torque of the winding roller. The PID controller regulates the torque of the winding roller through real-time feedback, thereby ensuring the stability of film tension during winding and avoiding quality problems caused by tension fluctuations.

[0074] The elastic properties of a thin film are verified using stress-strain curves. These curves are determined using a universal testing machine, which accurately measures the relationship between stress and strain during the tensile process. Analysis of the stress-strain curves allows for the assessment of the film's elastic and plastic characteristics, ensuring its durability and flexibility in practical applications.

[0075] By precisely controlling the longitudinal orientation, surface energy, tension, and elastic properties of the film, not only is the stability and consistency of the film during the blow molding process ensured, but the subsequent processing performance and final application effect of the film are also optimized. By adjusting key parameters such as speed ratio, corona treatment power, winding tension, and elastic modulus, the mechanical properties, processing adaptability, and surface properties of the film can be effectively improved, ultimately achieving the production of high-quality films.

[0076] In one possible implementation, the electrode spacing for corona treatment is first adjusted according to the film thickness and material to achieve optimal surface treatment results. The selection of the electrode spacing is determined based on a breakdown voltage test, which ensures the appropriateness of the electrode spacing, thereby guaranteeing the stability and uniformity of the corona discharge process. An appropriate electrode spacing can effectively increase the charge density on the film surface, enhance the surface adhesion of the film, and thus improve subsequent processing performance (such as printing and coating) and enhance the functionality of the film.

[0077] The corona treatment speed is synchronized with the traction speed to ensure uniformity of the treatment. If the corona treatment speed is too fast or too slow, it will lead to uneven surface treatment of the film, affecting the overall performance of the film. Therefore, ensuring that the corona treatment speed is matched with the traction speed helps to guarantee the consistency of the film surface treatment, thereby improving the surface properties of the film and the effect of subsequent processing.

[0078] Precision tension control is crucial during the winding process. Besides relying on the film's elastic modulus, tension control also requires consideration of inertia compensation. Inertia compensation is calculated based on the diameter variation of the winding roller, and this compensation can handle tension fluctuations caused by the continuous change in the roller diameter. Through proper inertia compensation, it can be ensured that the film tension remains within the ideal range during winding, avoiding film quality problems caused by tension fluctuations.

[0079] After winding, the film undergoes aging treatment, the duration of which needs to be determined based on the film's internal stress relaxation characteristics. These characteristics are obtained through stress relaxation experiments. These experiments reveal the release process of internal stress within the film over a certain period, providing a basis for setting the aging treatment time. By rationally controlling the aging treatment time, stress deformation that may occur in subsequent processing can be effectively reduced, improving the film's dimensional stability and mechanical properties.

[0080] Finally, the final performance of the film is verified through impact and tear tests. These tests assess key properties such as impact resistance and tear resistance. To ensure the representativeness of the test results, samples need to be taken from different locations on the film. This process allows for a comprehensive evaluation of the film's performance under various conditions, ensuring its reliability in practical applications.

[0081] The embodiments of this invention ensure that the various properties of the composite toughened film are comprehensively optimized during the blow molding process. By precisely controlling the electrode spacing, corona treatment speed, winding tension, aging treatment, and final performance testing, the surface adhesion, mechanical properties, and processing stability of the film can be improved, thereby ensuring the film's excellent performance in various applications.

[0082] In one possible implementation, the real-time data feedback system first integrates key process parameters such as temperature, pressure, speed, and tension. This data is acquired in real time via sensors and processed and transmitted through an industrial IoT platform. Real-time monitoring of sensor data enables each stage of the production process to respond to changes in real time, ensuring process stability and consistency during film forming. For example, monitoring temperature and pressure can precisely control heat transfer and pressure changes during extrusion and blow molding, avoiding quality fluctuations caused by process variations.

[0083] The parameters of the control algorithm are optimized using a machine learning model. This model is trained on historical production data, extracting valuable information from past production processes and adjusting the control algorithm's parameters accordingly to meet the demands of different batches. This allows for continuous self-optimization during production, improving efficiency while ensuring optimal film quality.

[0084] Online monitoring of quality indicators includes aspects such as thickness uniformity, surface defects, and mechanical properties. These indicators are tracked in real time using sensors and monitoring systems, and predicted and adjusted in conjunction with a digital twin model. The digital twin model, through virtual modeling of the thin film, allows for simulation of the production process in a virtual environment, predicting potential quality problems and making adjustments to proactively avoid potential defects in production. In this way, end-to-end monitoring of thin film quality can be achieved, enabling timely detection and correction of problems.

[0085] The entire method is implemented automatically using a programmable logic controller (PLC). The PLC program is customized according to the film's specifications and can automatically adjust various process parameters based on real-time data feedback, such as traction speed, corona treatment power, and winding tension. This automated control system reduces manual intervention, improves production stability and efficiency, and minimizes the impact of human error.

[0086] By integrating sensor data, machine learning-optimized control algorithms, digital twin model prediction and adjustment, and PLC automated control, the blow molding process of composite toughened films achieves highly precise control and real-time optimization. This invention not only improves production efficiency and film quality consistency but also ensures the flexibility and adaptability of the production process, enabling it to cope with various production needs and changes, and ensuring the excellent performance and stability of the final product.

[0087] Example;

[0088] This embodiment takes the preparation of polyethylene composite toughened film for heavy-duty packaging bags as an example to describe in detail the implementation process of each step.

[0089] Raw material preparation and pretreatment:

[0090] Matrix resin selection: High-density polyethylene (HDPE) with a melt index of 0.8 g / 10 min (190°C, 2.16 kg) and a density of 0.952 g / cm³ was used. This resin has high strength and rigidity, providing the basic mechanical properties for the film.

[0091] Composite toughening component composition:

[0092] Nanoscale inorganic filler: Nanoscale calcium carbonate with a surface treated with silane coupling agent was selected. Its particle size distribution, measured by laser particle size analyzer, showed a D50 of 105 nm and a D90 of 142 nm. The particle size distribution test employed wet dispersion, with ultrasonic treatment time controlled to 5 minutes to ensure thorough dispersion of the particles without breakage.

[0093] Elastomer microparticles: Polyolefin elastomer (POE) was selected, and its Shore hardness was determined to be 52A using an indentation hardness tester. The elastomer microparticles were prepared using a spray granulation process, with the average particle size controlled at 1.2 micrometers.

[0094] Interface compatibilizer: Maleic anhydride-grafted polyethylene (PE-g-MAH) was used, and the grafting rate was determined to be 0.85 wt% by titration. Infrared spectroscopy analysis showed a distinct characteristic absorption peak of carboxyl groups at 1710 cm⁻¹.

[0095] The formulation was determined as follows: the mass ratio of the matrix resin to the composite toughening component was 100:15, with the mass ratio of nano-calcium carbonate, POE elastomer, and PE-g-MAH being 3:10:2. This formulation was optimized through preliminary experiments using an orthogonal design method to investigate the effects of different formulations on the impact strength and elongation at break of the film.

[0096] Detailed implementation steps:

[0097] Step 1: Raw material pretreatment; HDPE granules were preheated in a forced-air drying oven at 75°C, a temperature determined based on differential scanning calorimetry (HDPE's glass transition temperature is -120°C, melting point is 132°C). During preheating, a double-cone rotary vacuum dryer was used for stirring at 12 rpm for 45 minutes. The preheated HDPE was then mixed with the composite toughening component in a high-speed mixer at 600 rpm for 8 minutes. Mixing uniformity was monitored using a power consumption curve; uniform mixing was considered achieved when power fluctuations stabilized within ±5%.

[0098] Step 2: Melt blending and granulation; melt blending is performed using a co-rotating twin-screw extruder with a screw diameter of 45 mm and an aspect ratio of 36:1. Temperature zones are set as follows:

[0099] Feeding area: 150°C, to prevent raw materials from melting and clogging prematurely;

[0100] Melting zone: 175°C, to ensure the matrix resin is completely melted;

[0101] Mixing zone: 185°C, providing sufficient shear to disperse toughening components;

[0102] Die head area: 180°C, moderate cooling increases melt strength;

[0103] The screw speed was set to 220 rpm, and the melt viscosity was monitored using an online viscometer and controlled within the range of 3500 Pa·s ± 200 Pa·s. The melt-blended material was then processed into cylindrical particles with a diameter of approximately 3 mm using an underwater pelletizing device, with the water temperature controlled at 25°C. The particles were subsequently dried in a vacuum drying oven at a vacuum degree of -0.095 MPa for 4 hours, and the final moisture content was measured to be less than 0.02% using a Karl Fischer moisture analyzer.

[0104] Step 3: Preparations for blow molding;

[0105] The dried composite granules are fed into a single-screw blow extruder with a die diameter of 100 mm and an initial die clearance of 1.8 mm. The fluid distribution channel inside the blow die contains eight flow distribution units, each with a taper angle of 20°, an expansion ratio of 1.8, and an aspect ratio of 1.0. The guide components are made of porous ceramic material with a radius of curvature of 85 mm on the arc-shaped contact surface and an air permeability of 200 L / m²·s.

[0106] Step 4: Blow molding and online monitoring;

[0107] Start the blow molding extruder. Set the temperature control system to: Zone 1 165°C, Zone 2 175°C, Zone 3 180°C, and Die 175°C. Initially, the screw speed is 25 rpm, gradually increasing to 45 rpm after the melt is uniformly extruded. Introduce compressed air into the preform, and stabilize the blowing pressure at 0.35 MPa using a PID controller. The blowing ratio is calculated to be 2.5.

[0108] The temperature distribution of the membrane tube was monitored in real time using an 8-point infrared thermometer, with the measurement points evenly distributed circumferentially. Monitoring data showed the condensation line height was 320mm. By adjusting the airflow of the cooling ring (from the initial value of 1200m³ / h to 950m³ / h) and the air pressure (from 0.25MPa to 0.20MPa), the condensation line height was stabilized at 350mm. Simultaneously, the film thickness was monitored using a laser thickness gauge, with the thickness deviation controlled within ±3%.

[0109] Step 5: Post-processing and winding;

[0110] The membrane tube is folded into a flat shape by the guide component, and the traction speed is set to 8.5 m / min, with a calculated traction ratio of 4.7. Corona treatment employs a bidirectional approach with a processing power of 3.5 kW, an electrode spacing of 2.0 mm, and the processing speed synchronized with the traction speed. The initial winding tension is set to 120 N, dynamically adjusted based on the film's elastic modulus (850 MPa, as determined by online testing), using PID control to ensure tension fluctuations remain within ±5 N. The wound film is then aged at 25°C for 48 hours to eliminate internal stress.

[0111] Performance testing and effect verification:

[0112] To fully verify the technical effectiveness of the method of this invention, systematic experimental tests and comparative analyses were conducted below. The tests covered three aspects: mechanical properties, structural characterization, and application performance, and were compared with thin films prepared by traditional methods. All tests were performed according to international standard methods to ensure the reliability and comparability of the data.

[0113] Experimental Design:

[0114] Test sample preparation:

[0115] Sample of this invention embodiment: Composite toughened film prepared according to the method of the foregoing embodiment, with a thickness of 50 μm;

[0116] Comparative Example 1: Toughened film with single nanofiller (only nano-calcium carbonate added, 5% addition amount);

[0117] Comparative Example 2: Single elastomer toughened film (POE elastomer added only, 10% addition amount);

[0118] Comparative Example 3: Composite toughened film prepared by traditional blow molding process (without special die design and online monitoring and control);

[0119] Comparative Example 4: Commercially available heavy-duty packaging polyethylene film (50 μm thick);

[0120] Test environment: temperature 23±2°C, relative humidity 50±5%, the sample was conditioned for 24 hours under standard conditions before the test;

[0121] Mechanical property testing:

[0122] Tensile tests were performed using a universal testing machine according to ASTM D882. Impact strength tests were performed using a falling dart impact tester according to ASTM D3420. Tear strength tests were performed according to ASTM D1922.

[0123] Table 1: Comparison of Mechanical Performance Test Results

[0124] Performance indicators Embodiments of the present invention Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Longitudinal tensile strength (MPa) 45.2±1.5 38.5±2.1 32.8±1.8 41.3±1.7 36.7±1.9 Transverse tensile strength (MPa) 42.1±1.3 36.2±1.7 30.5±1.5 38.9±1.4 34.2±1.6 Longitudinal elongation at break (%) 420±15 285±12 380±14 350±13 250±10 Transverse elongation at break (%) 380±12 260±11 350±13 320±12 230±9 Impact strength (kJ / m²) 125±8 85±6 95±7 105±7 75±5 Longitudinal tear strength (N / mm) 180±10 120±8 140±9 155±9 110±7 Transverse tear strength (N / mm) 165±9 110±7 130±8 145±8 100±6 Anisotropy Index 1.07 1.06 1.08 1.06 1.07

[0125] Results analysis:

[0126] The samples from the embodiments of this invention exhibit excellent toughness while maintaining high tensile strength. Compared with Comparative Examples 1 and 2, the synergistic effect of the composite toughening system is significant, with impact strength increased by approximately 30-50% compared to the single toughening system. Compared with the traditional blow molding process (Comparative Example 3), this invention, through multi-level structural control, increases the elongation at break by more than 20%, indicating that this invention has a significant advantage in improving toughness. The anisotropy index is close to 1.0, indicating good balance between longitudinal and transverse properties of the film.

[0127] Structural characterization analysis:

[0128] The microstructure of the thin film was observed using a scanning electron microscope (SEM, Hitachi SU8000) with an accelerating voltage of 5 kV. The crystal structure was analyzed using wide-angle X-ray diffraction (XRD, Rigaku SmartLab) with CuKα radiation and a scanning range of 5°–40°. The surface morphology was analyzed using atomic force microscopy (AFM, Bruker Dimension Icon).

[0129] Table 2: Structural Characterization Results

[0130] Test Project Embodiments of the present invention Comparative Example 1 Comparative Example 2 Comparative Example 3 Nanofiller dispersion (*) 0.92±0.03 0.85±0.04 - 0.88±0.03 Elastomer particle size distribution (μm) 1.0-1.5 - 1.5-2.5 1.2-2.0 Interfacial bond strength (MPa) 25.3±1.2 18.5±1.0 20.8±1.1 22.1±1.1 Crystal Orientation 0.35±0.02 0.42±0.03 0.38±0.02 0.40±0.02 Surface roughness Ra (nm) 45±3 65±4 55±3 52±3

[0131] Note: Dispersion is calculated through image analysis; 1.0 indicates perfectly uniform dispersion.

[0132] SEM analysis:

[0133] SEM images from this embodiment of the invention show that the nano-calcium carbonate filler is uniformly distributed in the matrix without obvious agglomeration. The elastomer particles form a clear island structure, with a particle size distribution concentrated in the range of 1.0-1.5 μm. The cross-sectional morphology shows a large number of fibrous stretched structures, indicating that an effective energy absorption mechanism occurred during fracture.

[0134] In Comparative Example 1, the nanofiller exhibited localized agglomeration, forming stress concentration points. In Comparative Example 2, the elastomer particle size distribution was relatively wide, and phase separation occurred in some areas. Although Comparative Example 3 had the same composition, due to the lack of precise process control, the filler distribution and interfacial bonding were not as good as those in the embodiments of the present invention.

[0135] XRD analysis:

[0136] The diffraction patterns of this embodiment show that the orientation of the (110) and (200) crystal planes is moderate, and the crystal size distribution is narrow. The crystal orientation degree calculated by the Hermans orientation function is 0.35, indicating that the crystal exhibits a moderate orientation arrangement in the thin film plane, which helps to balance the longitudinal and transverse properties.

[0137] Comparative Example 3 exhibits a higher crystal orientation (0.40), resulting in more pronounced anisotropy. Comparative Example 1, due to filler agglomeration affecting crystal growth, has the highest orientation (0.42), but exhibits poorer mechanical properties.

[0138] Application performance testing:

[0139] To verify the performance of the film in practical applications, a series of simulated environmental tests were conducted. Drop tests were performed according to ASTM D5276, puncture tests according to ASTM F1306, and air permeability tests according to ASTM D1434.

[0140] Table 3: Application Performance Test Results

[0141] Test Project Embodiments of the present invention Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Drop test pass height (m) 1.8 1.2 1.4 1.6 1.0 Puncture intensity (N) 85±5 55±4 65±4 75±5 50±3 Water vapor transmission rate (g / m²·day) 12.5±0.5 15.2±0.6 13.8±0.5 13.2±0.5 16.5±0.7 Oxygen permeability (cm³ / m²·day·atm) 850±30 1100±40 950±35 900±35 1200±50 Surface contact angle (°) 72±2 85±3 78±2 75±2 88±3 Thickness deviation (%) ±2.5 ±4.5 ±3.8 ±3.2 ±5.2

[0142] Drop test:

[0143] The film was made into a standard packaging bag (30×20cm), filled with a 25kg standard sandbag, and dropped from different heights. The embodiment of the present invention showed no damage after 20 drops from a height of 1.8m, while Comparative Examples 1 and 2 showed damage at heights of 1.2m and 1.4m, respectively. This indicates that the film of the present invention has excellent impact resistance.

[0144] Puncture test:

[0145] The test was conducted using a standard puncture probe (1 mm in diameter) at a speed of 50 mm / min. The puncture strength of this embodiment reached 85 N, which is 70% higher than that of commercially available products (Comparative Example 4), indicating that it has excellent puncture resistance and is suitable for packaging sharp items.

[0146] Barrier performance:

[0147] The embodiments of this invention exhibit superior barrier properties, with both water vapor and oxygen permeability lower than those of the comparative sample. This is attributed to the excellent dispersion of the nanofiller and the dense structure of the film, which is beneficial for food and pharmaceutical packaging applications.

[0148] Surface properties:

[0149] Surface contact angle testing shows that the embodiments of the present invention have moderate surface energy (contact angle 72°), which is beneficial for subsequent printing and lamination processes. Thickness deviation is controlled within ±2.5%, indicating good production process stability.

[0150] Mechanism analysis

[0151] The above test results provide a deeper understanding of the technical mechanism of this invention:

[0152] The composite toughening synergistic mechanism involves: nanofillers absorbing energy by inducing crazing, elastomers dissipating energy through shear yielding and voiding, and interfacial compatibilizers ensuring effective stress transfer. These three mechanisms work synergistically to achieve a balance between high strength and high toughness.

[0153] Multi-layered structure formation mechanism: Special die design and process control enable toughening components to form a gradient distribution and oriented arrangement in the film. In the thickness direction, the filler concentration exhibits a gradient change; in the planar direction, the elastomer is oriented along the flow direction, forming an ordered reinforcing network.

[0154] Process stability assurance: The online monitoring and feedback control system ensures stable process parameters, the control of the condensation line height optimizes the crystallization process, and the coordinated control of the traction ratio and the blow-up ratio reduces anisotropy.

[0155] in conclusion:

[0156] Through systematic performance testing and effect verification, the technical advantages of the method of this invention in preparing composite toughened films have been fully demonstrated. Compared with traditional methods, the films prepared by this invention maintain high strength while significantly improving toughness, and anisotropy is effectively controlled, fully meeting the requirements of demanding applications such as heavy-duty packaging.

[0157] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0158] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A blow molding method for a composite toughened film, characterized in that, Includes the following steps: Step 1: Preheat the matrix resin in a preheating device. The preheating temperature is controlled within the range of above the glass transition temperature of the matrix resin and below the melting point of the matrix resin. During the preheating process, the matrix resin is continuously stirred. Then, the preheated matrix resin and the composite toughening component are mixed in a dry mixing device in a specific ratio. The mixing time is used to ensure that the components are evenly distributed. The composite toughening component includes nano-sized inorganic fillers, elastomer particles and interface compatibilizers. Step 2: The mixed raw materials are fed into a twin-screw extruder for melt blending. The temperature of the twin-screw extruder is controlled in zones, forming a gradually increasing temperature gradient from the feed inlet to the die. The screw speed is controlled to ensure that the composite toughening components are fully dispersed in the matrix resin without degradation. The melt-blended material is made into uniform particles by an underwater pelletizing device, and then the particles are vacuum dried to remove the absorbed moisture. Step 3: Feed the dried composite granules into the hopper of the single-screw blow extruder, adjust the gap of the blow die to match the expected film thickness. The blow die is equipped with a fluid distribution channel, which enables the melt to generate a multi-layer alternating distribution structure during the flow process. Install and adjust the guide component, which has an arc-shaped contact surface and is made of a breathable material. Step 4: Start the single-screw blow extruder, adjust the temperature control system to the predetermined process parameters, extrude the melt from the die to form a tube blank, introduce compressed air into the tube blank to inflate the tube blank to form a film tube, control the inflation pressure according to the required fold diameter and thickness of the film and monitor and adjust it in real time through a pressure sensor, monitor the temperature distribution of the film tube in real time through an infrared temperature measuring device, and adjust the air volume and air pressure of the cooling system according to the monitoring results. Step 5: The formed film tube is folded into a flat shape by the guide component and led out by the traction roller. The traction speed is coordinated with the extrusion speed to control the traction ratio. The film surface is corona treated to improve the surface energy. Then, the winding tension is controlled to wind the film. The winding tension is controlled according to the elasticity and thickness of the film to prevent excessive stretching or slack.

2. The blow molding method for a composite toughened film according to claim 1, characterized in that, In step 1, the particle size distribution of the nanoscale inorganic filler is determined and controlled within a specific range using a laser particle size analyzer. The hardness of the elastomer microparticles is lower than that of the matrix resin and is determined using an indentation hardness tester. The molecular structure of the interface compatibilizer contains functional groups that can interact with both the matrix resin and the toughening component simultaneously, and the type of functional group is determined by infrared spectroscopy analysis. The ratio of the nanoscale inorganic filler, elastomer microparticles, and interface compatibilizer is adjusted according to the final film thickness and application requirements. The adjustment process is based on calculations of the expected impact strength and elongation at break of the film. The mixing speed of the dry mixing equipment is determined by monitoring the uniformity of the mixture, and the uniformity is evaluated by sampling and testing the consistency of the distribution of each component.

3. The blow molding method for a composite toughened film according to claim 1, characterized in that, In step 1, the specific range of preheating temperature is determined by the thermal analysis curve of the matrix resin, which is obtained by differential scanning calorimetry. The stirring speed during the preheating process is adjusted according to the particle size and flowability of the matrix resin, and the stirring speed is determined to ensure that the matrix resin is heated uniformly and does not clump. The mixing time is monitored by the power consumption curve in the dry mixing equipment. When the power consumption is stable, it indicates that the mixing is uniform. The specific proportion of the composite toughening component is determined by preliminary experiments, which include preparing samples with different proportions and testing the mechanical properties of the film.

4. The blow molding method for a composite toughened film according to claim 1, characterized in that, In step 2, the temperature zone control of the twin-screw extruder includes the feeding zone, melting zone, mixing zone, and die zone. The temperature settings of each zone are determined based on the thermal stability of the composite toughening system, which is measured by a thermogravimetric analyzer. The slope of the temperature gradient is calculated based on the melting characteristics of the matrix resin and the toughening component to ensure that the melt does not degrade. The screw speed is adjusted according to the viscosity change of the melt, and the viscosity is monitored by an online viscometer. The water temperature of the underwater pelletizing device is controlled below the glass transition temperature of the matrix resin to prevent particle adhesion. The vacuum degree and time of the vacuum drying are adjusted according to the moisture content of the particles, which is detected in real time by a moisture analyzer.

5. The blow molding method for a composite toughened film according to claim 1, characterized in that, In step 3, the gap of the blow molding die is calculated by the film thickness prediction model, which is based on melt flowability and blow-up ratio; the design of the fluid distribution channel includes multiple flow splitting units, and the geometry of the flow splitting units is optimized by computational fluid dynamics simulation to ensure that the melt produces a multi-layered alternating distribution structure. The radius of curvature of the arc-shaped contact surface of the guiding component is determined based on the diameter of the membrane tube, and the radius of curvature is calculated through geometric relationships; the air permeability of the breathable material is determined by material pore size distribution testing, and the air permeability is based on ensuring that the membrane tube folds smoothly without wrinkles; the angle and position of the guiding component are finely adjusted by simulating the movement trajectory of the membrane tube.

6. The blow molding method for a composite toughened film according to claim 1, characterized in that, In step 4, the predetermined process parameters of the temperature control system are determined by melt flow index testing, which is conducted at different temperatures; the blowing pressure is controlled based on the fold diameter and thickness requirements of the film, and the flow rate of compressed air is adjusted by feedback from the pressure sensor; the monitoring points of the infrared temperature measuring device are evenly distributed along the circumference of the film tube, and the number of monitoring points is determined according to the size of the film tube; the air volume and air pressure of the cooling system are adjusted based on the change in the position of the condensation line, and the position of the condensation line is determined by image processing captured by the infrared temperature measuring device; online monitoring also includes thickness uniformity detection, which is measured in real time by a laser thickness gauge, and the die head gap or traction speed is adjusted according to the measurement results.

7. The blow molding method for a composite toughened film according to claim 1, characterized in that, In step 4, the temperature distribution monitoring of the membrane tube includes real-time analysis of the height and shape of the condensation line, with the height of the condensation line identified by the inflection point of the temperature distribution curve; the airflow and air pressure adjustment of the cooling system adopt closed-loop control, and the set value of the closed-loop control is calculated based on the cooling rate requirement of the membrane, which is determined based on the crystallization behavior of the composite toughening system; the real-time monitoring of the inflation pressure includes pressure fluctuation analysis, with pressure fluctuations processed by a filtering algorithm to ensure control stability; The temperature of the compressed air is controlled below the ambient temperature to prevent the membrane tube from cooling down prematurely. The air temperature is regulated by a heat exchanger.

8. The blow molding method for a composite toughened film according to claim 1, characterized in that, In step 5, the coordination between traction speed and extrusion speed is controlled by speed ratio, which is calculated based on the longitudinal orientation requirements of the film and determined through pre-experimentation; the power of corona treatment is adjusted according to the surface energy requirements of the film, which are evaluated by a contact angle measuring instrument; the control of winding tension is based on the elastic modulus of the film, which is obtained through tensile testing; tension changes are monitored in real time by a tension sensor during winding, and the torque of the winding roller is adjusted by a PID controller; the elasticity of the film is verified by stress-strain curve, which is determined by a universal testing machine.

9. The blow molding method for a composite toughened film according to claim 1, characterized in that, In step 5, the electrode spacing for corona treatment is adjusted according to the film thickness and material, and the electrode spacing is determined by breakdown voltage testing; the corona treatment speed is synchronized with the traction speed to ensure uniform treatment; the control of winding tension also includes inertia compensation, which is calculated based on the diameter change of the winding roller; the wound film undergoes aging treatment, and the aging treatment time is determined based on the internal stress relaxation characteristics of the film, which are obtained through stress relaxation experiments; the final performance of the film is verified by impact testing and tear testing, with test samples taken from different locations on the film.

10. The blow molding method for a composite toughened film according to claim 1, characterized in that, In steps 1 to 5, all process parameters are adjusted based on real-time data feedback, including temperature, pressure, speed, and tension. The data feedback system uses an industrial IoT platform that integrates sensor data and control algorithms. The parameters of the control algorithm are optimized through a machine learning model, which is trained based on historical production data. The film's quality indicators are monitored online, including thickness uniformity, surface defects, and mechanical properties, and are predicted and adjusted using a digital twin model. The entire method is implemented automatically by a programmable logic controller (PLC), whose program is customized according to the film's specifications.

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