A mechanical reinforcement method for silica nanofiber membrane based on thermal-prestressing

Abstract

The present invention discloses a method for mechanically enhancing a silica nanofiber membrane based on heat-prestressing, which is applied to the field of electrostatic spinning nanofiber technology, including: preparing a silica spinning solution containing tetraethyl orthosilicate, ethanol, and hydrochloric acid; preparing a silica nanofiber membrane based on the silica spinning solution using electrostatic spinning technology, and applying heat-prestressing to the silica nanofiber membrane before the silica molecular chains of the silica nanofiber membrane are cross-linked into a network structure. The silica nanofiber membrane obtained by the heat-prestressing treatment of the present invention can exceed 1081% of the breaking strength of the untreated silica nanofiber membrane, and the increase rate of elongation at break can also reach 90%, thereby making the silica nanofiber membrane with enhanced mechanical properties better applied in certain fields.

Description

Technical Field

[0001] The present invention relates to the technical field of electrostatic spinning nanofibers, and in particular to a method for mechanically reinforcing a silicon dioxide nanofiber membrane based on thermal-prestress. Background Art

[0002] The preparation of silica nanofiber membranes by electrospinning has developed rapidly in the past decade. Due to its advantages such as high temperature resistance, good filtration performance, and thermal stability, it is expected to become the first choice for application in various inorganic composite materials. Especially in the fields of air purification, filtration, and high temperature resistant materials, due to its excellent performance, it is well used in high temperature fiber materials. The current preparation method of silica nanofibers usually uses the polymer template method, which involves the use and removal of polymer templates in the electrospinning preparation process of silica nanofibers. The steps are complicated, the silica nanofiber membrane is brittle, the mechanical strength of silica nanofibers is low, and they break when pulled, which seriously limits its application value and makes it unable to be used in the fields of textiles, membrane filtration, etc.

[0003] To improve the mechanical properties of silica nanofiber membranes and expand their applications, researchers have explored various methods to enhance their mechanical properties. Currently, the only known method for enhancing the mechanical properties of silica nanofiber membranes is chemical modification. While chemical modification can significantly enhance mechanical properties, it complicates the process and increases production costs. Conventional physical methods, such as altering electrospinning process parameters, can enhance the mechanical properties of silica nanofibers, but these enhancements are limited.

[0004] Therefore, how to provide a thermal-prestressed silica nanofiber membrane mechanical enhancement method with a simple process flow, low cost, and the ability to effectively enhance the mechanical properties of the silica nanofiber membrane is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] In light of this, the present invention proposes a method for mechanically strengthening silica nanofiber membranes based on thermal prestressing. By applying a certain prestress (generally no more than five times the weight of the silica nanofiber membrane itself) to the silica nanofiber membrane before the silica molecular chains are fully cross-linked, the silica nanofibers are oriented along the prestressed direction, while also increasing the orientation of the silica chains within the nanofibers. The fiber structure is then solidified through thermal treatment, thereby enhancing the mechanical properties of the silica nanofiber membrane.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for mechanically reinforcing a silica nanofiber membrane based on thermal prestressing, comprising:

[0008] Step (1): preparing a silica gel spinning solution containing tetraethyl orthosilicate, ethanol, and hydrochloric acid;

[0009] Step (2): Based on the silica spinning solution, the silica nanofiber membrane is prepared by using the electrospinning technology, and the silica nanofiber membrane is subjected to heat-prestress before the silica molecular chains of the silica nanofiber membrane are cross-linked into a network structure.

[0010] Optionally, in step (1), the molar ratio of tetraethyl orthosilicate, ethanol and hydrochloric acid is 1:2:0.0038.

[0011] Optionally, in step (2), heat-prestress is applied to the silica nanofiber membrane, specifically: heat treatment is performed while prestress is applied to the silica nanofiber membrane.

[0012] Optionally, the magnitude of the prestress is 1 to 5 times the weight of the silica nanofiber membrane itself.

[0013] Optionally, the heat treatment temperature is 150°C to 1000°C.

[0014] Optionally, the heat treatment time is 0.5h to 5h.

[0015] Through the above technical solution, it can be seen that compared with the existing technology, the present invention proposes a method for mechanically strengthening silica nanofiber membranes based on thermal prestressing. By applying a certain amount of thermal prestressing to the silica nanofiber membrane before the silicone molecular chains are completely cross-linked, the silica nanofiber membrane obtained by thermal prestressing can achieve a maximum breaking strength exceeding 1081% of the untreated silica nanofiber membrane, and the increase in elongation at break can reach 90%, effectively enhancing the mechanical properties of the silica nanofiber membrane. This allows the silica nanofiber membrane with enhanced mechanical properties to be better applied in fields such as textiles and membrane filtration, and the process is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the method of the present invention.

[0018] Figure 2 Schematic diagram of the electrospinning device of the present invention.

[0019] Figure 3Schematic diagram of the device for applying prestress to the silica nanofiber membrane according to the present invention.

[0020] Figure 4 This is a schematic diagram of the simulated effect of the change in unit area of ​​the silica nanofiber membrane before and after applying heat-prestress in the present invention. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] Example 1:

[0023] Example 1 of the present invention discloses a method for mechanically strengthening a silica nanofiber membrane based on thermal-prestressing, such as Figure 1 Shown, including:

[0024] Step (1): Prepare a silica spinning solution containing tetraethyl orthosilicate, ethanol, and hydrochloric acid by a sol-gel method, without using a polymer to prepare the silica spinning solution; wherein the molar ratio of tetraethyl orthosilicate, ethanol, and hydrochloric acid is 1:2:0.0038, specifically: first dissolve tetraethyl orthosilicate in an anhydrous ethanol solution, take a hydrochloric acid solution and drop it into the former mixture, and then place the prepared mixture under constant temperature magnetic stirring at 80°C and heat it until the silica spinning solution reaches a spinnable viscosity. The silica spinning solution preparation method adopted by the present invention is different from the current mainstream polymer template electrospinning method, and does not use a polymer to prepare the silica spinning solution, which can further improve the mechanical properties of the silica nanofiber membrane.

[0025] The current mainstream polymer template electrospinning method is specifically as follows: a polymer such as polyvinyl alcohol solution is slowly dripped into a mixed solution of tetraethyl orthosilicate, ethanol and acid for aging to obtain a polyvinyl alcohol / tetraethyl orthosilicate (PVA / silica gel) viscous solution, which is then electrospun to obtain a PVA / silica gel composite fiber membrane, which is then calcined and the polymer template is removed to finally obtain a silica nanofiber membrane. The silica nanofiber membrane finally obtained by this method through the polymer template has very poor mechanical properties, and due to the poor mechanical properties, it breaks when pulled. Therefore, the heat-prestress in step (2) of the present invention cannot be applied.

[0026] Step (2): Based on silica gel spinning solution, apply Figure 2The electrospinning device shown uses electrospinning technology to prepare silica nanofiber membranes. Specifically, the silica spinning solution that reaches a spinnable viscosity is transferred to a syringe, and a high voltage of 20KV is passed through. A layer of tin foil is covered on the roller receiving device. Under the combined action of electrostatic force, the bonding force of the spinning solution, etc., Taylor cone-jet silica nanofibers are formed, and a silica nanofiber membrane is obtained on the receiving tin foil; and the following methods are used: Figure 3 The prestressing device shown applies heat-prestress to the silica nanofiber membrane before the silicone molecular chains of the silica nanofiber membrane are cross-linked into a network structure. That is, while applying prestress to the silica nanofiber membrane, heat treatment is performed to orient the molecular chains along the prestressing direction and to order some disordered fibers, thereby increasing the number of fibers along the prestressing direction. After the nanofibers are completely cross-linked, a new fiber structure is formed. The schematic diagram of the simulated effect of the change in unit area of ​​the silica nanofiber membrane before and after applying heat-prestress is shown in FIG. Figure 4 As shown in FIG, the mechanical properties of the nanofibers are directionally enhanced, specifically: the prepared silica nanofiber membrane sample (silica nanofiber membrane whose silicone molecular chains are not completely cross-linked into a network structure) is fixed on a homemade prestressing instrument, and weights are added to the sample along the longitudinal direction of the nanofiber to directionally apply prestress, wherein the magnitude of the prestress is 1 to 5 times the weight of the silica nanofiber membrane itself, and then the prestressing device is placed in a muffle furnace for heat treatment at a heat treatment temperature of 150°C to 1000°C and a heat treatment time of 0.5h to 5h. Through these three factors, the mechanical properties of the silica nanofiber membrane are enhanced to a certain extent under this method, wherein the growth rate of the breaking strength reaches 1081%, and the growth rate of the breaking elongation can reach 90%, as shown in Table 1.

[0027] Table 1 Enhancement results of mechanical properties of silica nanofiber membrane under three-factor treatment

[0028]

[0029] Among them, the first group of experiments is the control group, and the growth rates of fracture strength and fracture elongation of each of the remaining groups of experiments are calculated based on the control group. The experiments show that after the silica nanofiber membrane is cut into specimens, 3 times prestress is immediately applied to it, and then it is treated at 450°C for 0.5 hours. Its fracture degree can be increased by 1081%, and the increase rate of fracture elongation can reach 90%.

[0030] The embodiment of the present invention discloses a method for mechanically enhancing a silica nanofiber membrane based on thermal prestressing. By preparing a silica spinning solution containing tetraethyl orthosilicate, ethanol, and hydrochloric acid without using a polymer to prepare the silica spinning solution, not only the mechanical properties of the silica nanofiber membrane are further improved, but also the silica nanofiber membrane prepared based on the silica spinning solution can withstand a certain prestress; by applying a certain thermal prestress to the silica nanofiber membrane before the silica molecular chains are completely cross-linked, the silica nanofiber membrane obtained by the thermal prestressing treatment can exceed 1081% of the breaking strength of the untreated silica nanofiber membrane, and the increase rate of elongation at break can reach 90%, effectively enhancing the mechanical properties of the silica nanofiber membrane, so that the silica nanofiber membrane with enhanced mechanical properties can be better applied in the fields of textiles, membrane filtration, etc., and the process flow is simple and the cost is low.

[0031] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0032] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for mechanically strengthening a silica nanofiber membrane based on thermal prestressing, characterized in that: include: Step (1): preparing a silica gel spinning solution containing tetraethyl orthosilicate, ethanol, and hydrochloric acid; Step (2): preparing a silica nanofiber membrane based on the silica spinning solution by using an electrospinning technique, and applying heat-prestress to the silica nanofiber membrane before the silica molecular chains of the silica nanofiber membrane are cross-linked into a network structure; In step (2), heat-prestress is applied to the silica nanofiber membrane, specifically: heat treatment is performed while prestress is applied to the silica nanofiber membrane.

2. The method for mechanically reinforcing a silica nanofiber membrane based on thermal prestressing according to claim 1, characterized in that: In step (1), the molar ratio of the tetraethyl orthosilicate, the ethanol, and the hydrochloric acid is 1:2:0.0038.

3. The method for mechanically reinforcing a silica nanofiber membrane based on thermal prestressing according to claim 1, characterized in that: The magnitude of the prestress is 1 to 5 times the weight of the silicon dioxide nanofiber membrane itself.

4. The method for mechanically reinforcing a silica nanofiber membrane based on thermal prestressing according to claim 1, characterized in that: The temperature of the heat treatment is 150°C to 1000°C.

5. The method for mechanically reinforcing a silica nanofiber membrane based on thermal prestressing according to claim 1, characterized in that: The heat treatment time is 0.5h to 5h.

Images