Flame-retardant high-strength silica gel plate and preparation method thereof

Abstract

The invention discloses a flame-retardant high-strength silica gel plate and a preparation method thereof, and belongs to the technical field of composite materials. The silica gel plate comprises a modified silica gel layer and a flame-retardant PVC layer, nano flame-retardant PVC particles are prepared by an ultrasonic-assisted sol-gel method, and a double-layer composite structure is prepared by adopting a multi-layer co-extrusion and hot-pressing combined process. Nano montmorillonite and triphenyl phosphate are introduced to synergistically improve the flame retardant property, and plasma treatment is adopted to enhance the interface bonding force. The obtained silica gel plate has excellent tensile strength, interface peel strength and flame retardance, and is suitable for safety protection materials in the fields of buildings, electronics, traffic and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of silica gel plates, in particular to a flame retardant high-strength silica gel plate and a preparation method thereof. Background Art

[0002] Flame-retardant, high-strength silicone sheets, as layered composite materials, are widely used in fields such as construction, electronics, automotive, and aerospace. Their development is driven by the excellent heat and weather resistance of silicone (polysiloxane) and the flame retardancy and cost-effectiveness of polyvinyl chloride (PVC). In recent years, with increasing demands for material safety and mechanical properties, the research and application of silicone / PVC composite sheets has rapidly advanced. Early technologies primarily achieved the layered bonding of silicone and PVC through physical blending or hot-pressing, supplemented by the addition of flame retardants (such as aluminum hydroxide and phosphate esters) to enhance flame retardancy. In the 21st century, the introduction of nanotechnology and interfacial modification has significantly improved the performance of composite sheets. For example, the addition of nanofillers (such as montmorillonite and graphene oxide) enhances flame retardancy and mechanical strength, while surface treatment techniques (such as plasma treatment) improve interlayer adhesion. Furthermore, the development of green, halogen-free flame retardants and novel processing techniques (such as co-extrusion and supercritical CO2 foaming) have further promoted the development of this field towards environmental protection and high performance. However, existing technologies still face many challenges in terms of interface optimization, synergistic improvement of mechanical properties and flame retardancy, and processing complexity, which limits the application of silicone / PVC composite panels in high-requirement scenarios.

[0003] While existing technologies have made some progress in the preparation and performance optimization of silicone / PVC composite panels, significant deficiencies remain, particularly in the inefficient interfacial stress transfer within layered composite structures. The high flexibility of silicone and the rigidity of PVC create a significant mechanical mismatch, leading to stress concentration at the interface, inducing microcracks and even delamination failure. Existing technologies often enhance interfacial bonding through the addition of compatibilizers or physical intercalation, but these methods struggle to fundamentally address the weak interfacial bonding caused by differences in chemical polarity and thermodynamic incompatibility. Summary of the Invention

[0004] The present invention provides a flame-retardant high-strength silicone plate and a preparation method thereof, comprising the following technical steps:

[0005] Step S1. Nano-montmorillonite and triphenyl phosphate are added to PVC resin, dispersed uniformly by ultrasound-assisted sol-gel method, and the mixture is melt-blended in a twin-screw extruder and granulated for later use;

[0006] Step S2. Place the modified silicone substrate and flame-retardant modified PVC particles at two feed ports of a multi-layer co-extrusion device, respectively, and form a silicone / PVC double-layer structure through a co-extrusion die;

[0007] Step S3: placing the co-extruded composite board in a hot press for hot pressing, and then cooling it at room temperature until it solidifies.

[0008] As a preferred technical solution for a flame-retardant high-strength silica gel plate and its preparation method, in step S1, the amount of the nano-montmorillonite added is 2-5wt% of the mass of the PVC resin, the amount of triphenyl phosphate added is 3-7wt% of the mass of the PVC resin, and the molecular weight of the PVC resin is 70,000-100,000 g / mol.

[0009] As a preferred technical solution for a flame-retardant high-strength silica gel plate and a preparation method thereof, in step S1, the ultrasound-assisted sol-gel method adopts an ultrasound frequency of 40 kHz and a dispersion time of 20-40 minutes.

[0010] As a preferred technical solution for a flame-retardant high-strength silicone plate and a preparation method thereof, in step S1, the melt blending temperature of the twin-screw extruder is 170-190°C, and the screw speed is 80-120rpm.

[0011] As a preferred technical solution for a flame-retardant high-strength silicone plate and its preparation method, in step S2, the preparation method of the modified silicone substrate includes: placing the polysiloxane substrate in a plasma treatment device, using an argon / oxygen mixed atmosphere with a mass ratio of 3:1, and treating it at a power of 100 W for 30-60 seconds.

[0012] As an optimal technical solution for a flame-retardant high-strength silicone plate and its preparation method, in step S2, the extrusion temperature of the silicone layer of the multi-layer co-extrusion equipment is 150-170°C, the extrusion temperature of the PVC layer is 180-200°C, and the extrusion rate is controlled at 0.3-0.7m / min.

[0013] As a preferred technical solution for a flame-retardant high-strength silicone plate and a preparation method thereof, in step S2, the silicone layer of the silicone / PVC double-layer structure has a thickness of 0.5-1 mm, and the PVC layer has a thickness of 1-2 mm.

[0014] As a preferred technical solution for a flame-retardant high-strength silicone plate and a preparation method thereof, in step S3, the hot pressing temperature is 110-130° C., the pressure is 4-6 MPa, and the hot pressing time is 8-12 minutes.

[0015] The present invention significantly improves the mechanical properties, interfacial bonding strength and flame retardant properties of the material by synergistically introducing nano-montmorillonite (MMT) and triphenyl phosphate (TPP) into the silica gel / PVC composite board, and combining plasma surface treatment and hot pressing processes. The high specific surface area of ​​MMT can adsorb the decomposition products of TPP, promote the formation of a dense carbon layer, and thus increase the oxygen index; TPP reacts with the hydroxyl groups on the surface of silica gel to form weak chemical bonds such as PO-Si, improving the interfacial bonding force; the hot pressing process further enhances the interlayer adhesion and structural density. Compared with the unoptimized control example, the tensile strength of the composite board increased by 7.1%-45.8%, the interfacial peel strength increased by 12.5%-65.7%, and the LOI increased by 7.1%-30.6%. DETAILED DESCRIPTION

[0016] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0017] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0018] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute a separate or selective embodiment that is mutually exclusive with other embodiments.

[0019] Example

[0020] Example 1

[0021] Example 1 provides a flame-retardant high-strength silicone plate and a preparation method thereof, comprising the following technical steps:

[0022] Step 1. Preparation of flame-retardant modified PVC: 100 kg of PVC resin (molecular weight 70,000 g / mol) was added with 2 kg (2 wt%) of nano-montmorillonite (MMT, particle size 50-100 nm) and 3 kg (3 wt%) of triphenyl phosphate (TPP). An ultrasound-assisted sol-gel method was used at an ultrasonic frequency of 40 kHz for 20 minutes to ensure that the MMT and TPP were evenly dispersed in the PVC matrix. The mixture was placed in a twin-screw extruder at a melt blending temperature of 170°C and a screw speed of 80 rpm. After extrusion, pelletization was performed.

[0023] Step 2. Silicone / PVC double-layer composite: A polysiloxane substrate (1.5mm thick) was placed in a plasma treatment apparatus using an argon / oxygen mixed atmosphere (mass ratio 3:1) at 100W for 30 seconds to introduce hydroxyl and carboxyl groups. The modified silicone substrate and flame-retardant modified PVC particles were then placed in a multi-layer co-extrusion apparatus. The silicone layer was extruded at 150°C, the PVC layer at 180°C, and the extrusion rate was 0.3m / min. A double-layer structure with a silicone layer thickness of 0.5mm and a PVC layer thickness of 1mm was formed.

[0024] Step 3. Hot pressing and curing: Place the co-extruded composite board in a hot press at a temperature of 110°C, a pressure of 4 MPa, and a hot pressing time of 8 minutes, and then cool and cure at room temperature.

[0025] Example 2

[0026] Example 2 provides a flame-retardant high-strength silica gel plate and a preparation method thereof, comprising the following technical steps:

[0027] Step 1. Preparation of flame-retardant modified PVC: 100 kg of PVC resin (molecular weight 85,000 g / mol) was added with 3.5 kg (3.5 wt%) of nano-montmorillonite (MMT, particle size 50-100 nm) and 5 kg (5 wt%) of triphenyl phosphate (TPP). An ultrasound-assisted sol-gel method was used at an ultrasonic frequency of 40 kHz for 30 minutes to ensure that the MMT and TPP were evenly dispersed in the PVC matrix. The mixture was placed in a twin-screw extruder at a melt blending temperature of 180°C and a screw speed of 80 rpm. After extrusion, pelletization was performed.

[0028] Step 2. Silicone / PVC double-layer composite: A polysiloxane substrate (1.5mm thick) was placed in a plasma treatment apparatus using an argon / oxygen mixed atmosphere (mass ratio 3:1) at 100W for 45 seconds to introduce hydroxyl and carboxyl groups. The modified silicone substrate and flame-retardant modified PVC particles were then placed in a multi-layer co-extrusion apparatus. The silicone layer was extruded at 160°C, the PVC layer at 190°C, and the extrusion rate was 0.5m / min. A double-layer structure with a silicone layer thickness of 0.75mm and a PVC layer thickness of 1.5mm was formed.

[0029] Step 3. Hot pressing and curing: Place the co-extruded composite board in a hot press at a temperature of 120°C, a pressure of 5 MPa, and a hot pressing time of 10 minutes, and then cool and cure at room temperature.

[0030] Example 3

[0031] Example 3 provides a flame-retardant high-strength silica gel plate and a preparation method thereof, comprising the following technical steps:

[0032] Step 1. Preparation of flame-retardant modified PVC: 100 kg of PVC resin (molecular weight 100,000 g / mol) was added with 5 kg (5.0 wt%) of nano-montmorillonite (MMT, particle size 50-100 nm) and 7 kg (7 wt%) of triphenyl phosphate (TPP). An ultrasound-assisted sol-gel method was used at an ultrasonic frequency of 40 kHz for 40 minutes to ensure that MMT and TPP were uniformly dispersed in the PVC matrix. The mixture was placed in a twin-screw extruder at a melt blending temperature of 190°C and a screw speed of 120 rpm. After extrusion, pelletization was performed.

[0033] Step 2. Silicone / PVC double-layer composite: A polysiloxane substrate (1.5mm thick) was placed in a plasma treatment apparatus using an argon / oxygen mixed atmosphere (mass ratio 3:1) at 100W for 60 seconds to introduce hydroxyl and carboxyl groups. The modified silicone substrate and flame-retardant modified PVC particles were then placed in a multi-layer co-extrusion apparatus. The silicone layer was extruded at 170°C, the PVC layer at 200°C, and the extrusion rate was 0.7m / min. A double-layer structure with a silicone layer thickness of 1.0mm and a PVC layer thickness of 2.0mm was formed.

[0034] Step 3. Hot pressing and curing: Place the co-extruded composite board in a hot press at a temperature of 130°C, a pressure of 6 MPa, and a hot pressing time of 12 minutes, and then cool and cure at room temperature.

[0035] Example 4

[0036] Example 4 provides a flame-retardant high-strength silica gel plate and a preparation method thereof, comprising the following technical steps:

[0037] Step 1. Preparation of flame-retardant modified PVC: 100 kg of PVC resin (molecular weight 85,000 g / mol) was added with 4.0 kg (4.0 wt%) of nano-montmorillonite (MMT, particle size 50-100 nm) and 4 kg (4 wt%) of triphenyl phosphate (TPP). An ultrasound-assisted sol-gel method was used at an ultrasonic frequency of 40 kHz for 25 minutes to ensure that the MMT and TPP were evenly dispersed in the PVC matrix. The mixture was placed in a twin-screw extruder at a melt blending temperature of 175°C and a screw speed of 90 rpm. After extrusion, pelletization was performed.

[0038] Step 2. Silicone / PVC double-layer composite: A polysiloxane substrate (1.5mm thick) was placed in a plasma treatment apparatus using an argon / oxygen mixed atmosphere (mass ratio 3:1) at 100W for 40 seconds to introduce hydroxyl and carboxyl groups. The modified silicone substrate and flame-retardant modified PVC particles were then placed in a multi-layer co-extrusion apparatus. The silicone layer was extruded at 155°C, the PVC layer at 185°C, and the extrusion rate was 0.4m / min. A double-layer structure with a silicone layer thickness of 0.6mm and a PVC layer thickness of 1.2mm was formed.

[0039] Step 3. Hot pressing and curing: Place the co-extruded composite board in a hot press at a temperature of 115°C, a pressure of 4.5 MPa, and a hot pressing time of 9 minutes, and then cool and cure at room temperature.

[0040] Control Example

[0041] Comparative Example 1

[0042] The difference between Control Example 1 and Example 1 is that no MMT was added.

[0043] Comparative Example 2

[0044] The difference between Comparative Example 2 and Example 1 is that no TPP is added.

[0045] Comparative Example 3

[0046] The difference between Comparative Example 3 and Example 1 is that the silicone substrate (polysiloxane, thickness 1.5 mm) is not subjected to plasma treatment and is directly used for co-extrusion.

[0047] Comparative Example 4

[0048] The difference between this control example and Example 1 is that the hot pressing step is omitted, and the co-extruded composite board is directly cooled and solidified at room temperature.

[0049] Performance testing methods

[0050] Tensile strength test: Tested according to ASTM D638-14 standard;

[0051] Interfacial peel strength test: tested in accordance with ASTM D903-98 (2017);

[0052] Limiting Oxygen Index (LOI) test: tested in accordance with ISO 4589-2:2017;

[0053] Table 1 Experimental data of Examples 1 to 4 and Comparative Examples 1 to 4

[0054]

[0055]

[0056] Combining Examples 1 to 4 and Table 1, it can be seen that the tensile strength of Examples 1 to 4 reaches 28-35 MPa, the interfacial peel strength is 4.5-5.8 N / mm, and the LOI is 28.5-32.0%. Examples 1 to 4 optimize the mechanical properties and flame retardant properties of the silicone / PVC composite board by adjusting the amount of MMT and TPP added and process parameters (such as ultrasonic dispersion time, co-extrusion temperature, and hot pressing conditions), thereby solving the problem of interfacial stress concentration.

[0057] Combining Example 1, Control Example 1, Control Example 2, and Table 1, it can be seen that a performance comparison of Example 1 with Control Examples 1 and 2 shows that: Example 1 has a tensile strength of 28 MPa, an interfacial peel strength of 4.5 N / mm, and a limiting oxygen index (LOI) of 28.5%; Control Example 1 has 24 MPa (a decrease of 14.3%), 3.8 N / mm (a decrease of 15.6%), and 25.5% (a decrease of 10.5%), respectively; and Control Example 2 has 26 MPa (a decrease of 7.1%), 4.0 N / mm (a decrease of 11.1%), and 24.5% (a decrease of 14%), respectively. The present invention significantly improves the flame retardancy and interfacial bonding strength of the silicone / PVC composite board through the synergistic effect of nano-montmorillonite (MMT) and triphenyl phosphate (TPP), alleviating stress concentration caused by the mismatch in mechanical properties between silicone and PVC. The high specific surface area of ​​MMT adsorbs phosphoric acid compounds decomposed from TPP, promoting their reaction with the pyrolyzed polyene structure of PVC to form a dense carbon layer and increase the LOI. The decomposition products of TPP form weak PO-Si or P-Cl chemical bonds with the Si-OH of activated silica gel or the HCl of PVC, which, combined with the physical bridging of MMT, enhance the interfacial bonding, making the peel strength and tensile strength of Example 1 better than those of the control example.

[0058] Combining Example 1, Control Example 3, and Table 1, it can be seen that a performance comparison between Example 1 and Control Example 3 shows that Example 1 has a tensile strength of 28 MPa, an interfacial peel strength of 4.5 N / mm, and a limiting oxygen index (LOI) of 28.5%; while Control Example 3 has values ​​of 25 MPa (a decrease of 10.7%), 3.5 N / mm (a decrease of 22.2%), and 27.5% (a decrease of 3.5%), respectively. The present invention introduces Si-OH and -COOH groups onto the surface of silica gel through plasma treatment, thereby increasing surface polarity and improving the wettability of the PVC melt. The weak chemical bonds PO-Si or P-Cl formed by the decomposition of TPP and the adsorption of TPP decomposition products by MMT promote a dense carbon layer, significantly enhancing the interfacial bonding and flame retardancy of the silica gel / PVC composite board and alleviating stress concentration caused by mechanical property mismatch.

[0059] Combining Example 1, Control Example 4 and Table 1, it can be seen that after co-extrusion, Example 1 adds a hot pressing step, and its tensile strength is 28 MPa, the interfacial peel strength is 4.5 N / mm, and the limiting oxygen index (LOI) is 28.5%; while after removing the hot pressing step, the tensile strength of Control Example 4 drops to 26 MPa (a decrease of 7.1%), the interfacial peel strength drops to 4.0 N / mm (a decrease of 11.1%), and the LOI is 28.0% (a decrease of 1.8%). This shows that the hot pressing step plays an important role in improving the mechanical properties and interfacial bonding strength of the composite board. Hot pressing can promote the interfacial penetration and physical intercalation between silicone and PVC, while improving the structural density, thereby enhancing the overall performance of the material. It can be seen that Example 1 effectively improves the mechanical properties and interfacial bonding strength of the silicone / PVC composite board while maintaining high flame retardant properties by optimizing the molding process.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A flame-retardant high-strength silicone plate and a preparation method thereof, characterized in that: The following technical steps are included: Step S1. Nano-montmorillonite and triphenyl phosphate are added to PVC resin, dispersed uniformly by ultrasound-assisted sol-gel method, and the mixture is melt-blended in a twin-screw extruder and granulated for later use; Step S2. Place the modified silicone substrate and flame-retardant modified PVC particles at two feed ports of a multi-layer co-extrusion device, respectively, and form a silicone / PVC double-layer structure through a co-extrusion die; Step S3: placing the co-extruded composite board in a hot press for hot pressing, and then cooling it at room temperature until it solidifies.

2. The flame-retardant high-strength silicone plate and the preparation method thereof according to claim 1, characterized in that: In step S1, the amount of the nano-montmorillonite added is 2-5 wt% of the mass of the PVC resin, the amount of the triphenyl phosphate added is 3-7 wt% of the mass of the PVC resin, and the molecular weight of the PVC resin is 70,000-100,000 g / mol.

3. The flame-retardant high-strength silicone plate and the preparation method thereof according to claim 1, characterized in that: In step S1, the ultrasound-assisted sol-gel method uses an ultrasound frequency of 40 kHz and a dispersion time of 20-40 minutes.

4. The flame-retardant high-strength silicone plate and the preparation method thereof according to claim 1, characterized in that: In step S1, the melt blending temperature of the twin-screw extruder is 170-190° C., and the screw speed is 80-120 rpm.

5. The flame-retardant high-strength silicone plate and the preparation method thereof according to claim 1, characterized in that: In step S2, the preparation method of the modified silica gel substrate includes: placing the polysiloxane substrate in a plasma treatment device, using an argon / oxygen mixed atmosphere with a mass ratio of 3:1, and treating it at a power of 100 W for 30-60 seconds.

6. The flame-retardant high-strength silicone plate and the preparation method thereof according to claim 1, characterized in that: In step S2, the extrusion temperature of the silicone layer of the multi-layer co-extrusion equipment is 150-170°C, the extrusion temperature of the PVC layer is 180-200°C, and the extrusion rate is controlled at 0.3-0.7 m / min.

7. The flame-retardant high-strength silicone plate and the preparation method thereof according to claim 1, characterized in that: In step S2, the thickness of the silicone layer of the silicone / PVC double-layer structure is 0.5-1 mm, and the thickness of the PVC layer is 1-2 mm.

8. The flame-retardant high-strength silicone plate and the preparation method thereof according to claim 1, characterized in that: In step S3, the hot pressing temperature is 110-130° C., the pressure is 4-6 MPa, and the hot pressing time is 8-12 minutes.

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