A basalt fiber base composite geotextile and its preparation method

Abstract

The present invention discloses a basalt fiber base composite geotextile and a preparation method thereof, which includes a functional protective film layer, a modified high polymer layer and a basalt fiber grid cloth layer. The modified high polymer layer comprises raw materials in the following weight parts: 45-55 parts of matrix asphalt, 15-25 parts of phenolic resin, 8-14 parts of styrene-butadiene rubber powder, 4-8 parts of setting agent, 3-7 parts of ethylene-vinyl acetate copolymer, and 4-12 parts of modifier. The present invention produces a composite geotextile with high tensile strength, high temperature resistance, good adhesion and excellent low temperature toughness through scientific and reasonable design and formulation. In actual use, it can be firmly bonded to the base layer, has a good stress absorption effect, and effectively prevents the expansion of pavement reflection cracks. The present invention uses a basalt fiber grid cloth, which has a good interlocking effect on the modified high polymer, greatly reduces the consumption of raw materials while meeting the performance requirements, and has great cost advantages and marketability.

Description

Technical Field

[0001] The present invention relates to a composite geotextile and a preparation method thereof, and particularly to a basalt fiber matrix composite geotextile and a preparation method thereof. Background Art

[0002] "Thin base and strong surface" was the main idea guiding road development in the initial stage of highway network construction. The semi-rigid base asphalt pavement structure has also become the most common form of high-grade highways, accounting for more than 90% of expressways. On the one hand, using inorganic binder stabilized base can reduce the consumption of road materials such as asphalt and lower the construction cost; on the other hand, it can also better ensure the strength of the road base. However, under the action of factors such as temperature and load, semi-rigid base roads are prone to diseases such as reflective cracks, reducing the service life of the road and the driving safety. Laying composite geotextiles between the road base and the surface layer can better prevent the expansion of base reflective cracks, thus protecting the surface layer. There are many types of existing composite geotextiles, and polyester fiberglass cloth, non-woven stress cloth and other fabrics are mostly selected as the matrix, and high polymers are used as the base material for compounding. However, some of the new composite geotextiles published in the literature still have problems such as poor durability, single function, insufficient tensile strength, etc., are not suitable for preventing cracks, and there is a hidden danger of rapid performance degradation in a short time after use, which is likely to cause sliding between asphalt repair structural layers and damage the integrity of the road surface.

[0003] Basalt fiber has excellent properties such as high strength, high modulus, good high and low temperature resistance, oxidation resistance, fire resistance and flame retardance. However, there are few reports on the research of using basalt fiber to make grid cloth for enhancing and modifying composite geotextiles. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a high-performance basalt fiber matrix composite geotextile, which has performance advantages such as fast adhesion and firmness, obvious crack resistance effect, high temperature resistance, etc., and economic advantages of reasonable design, material saving and cost saving; another object of the present invention is to provide a preparation method of a basalt fiber matrix composite geotextile, which has a simple process, is green and low-carbon, is conducive to industrial production, and the main raw materials are natural and environmentally friendly, and is convenient for specific construction and use.

[0005] Technical solution: The basalt fiber base composite geotextile of the present invention includes a functional protective film, a modified high polymer layer, and a basalt fiber grid cloth; the modified high polymer layer is a specially developed modified high polymer asphalt, which has good adhesion and low temperature flexibility, and includes the following raw materials in parts by weight: 45-55 parts of matrix asphalt, 15-25 parts of phenolic resin, 8-14 parts of styrene-butadiene rubber powder, 4-8 parts of setting agent, 3-7 parts of ethylene-vinyl acetate copolymer, and 4-12 parts of modifier; the modifier and setting agent added in the modified high polymer have a synergistic effect of increasing viscosity and stability, effectively ensuring the high temperature performance and adhesiveness of the modified high polymer, and the added ethylene-vinyl acetate copolymer can effectively improve the low temperature flexibility. The present invention improves the stability and low temperature flexibility of common existing substrates, and enables each component to remain unchanged during processing and high temperatures.

[0006] Preferably, the basalt fiber base composite geotextile is, from top to bottom, an upper functional protective film, an upper modified high polymer layer, a basalt fiber grid cloth, a lower modified high polymer layer, and a lower functional protective film.

[0007] Preferably, the protective film is a polyethylene isolation film, and its main function is to prevent the modified polymer from losing its original properties when exposed to air.

[0008] Preferably, the basalt fiber base is a grid cloth woven from basalt fibers. This cloth type can reduce a large amount of raw material consumption while meeting the performance requirements, saving energy and the environment, and reducing costs. The density of the basalt fiber grid cloth base is 110-160 g / m 2 .

[0009] Preferably, the ethylene-vinyl acetate copolymer has a vinyl acetate content of 40% and a melt index of 25 g / 10 min.

[0010] Preferably, the modifier is at least one of ethyl cellulose, biomass cellulose, and hydroxypropyl methyl cellulose.

[0011] Preferably, the phenolic resin is phenolic resin 2130.

[0012] Preferably, the setting agent is one of ethylenediamine and diethylenetriamine.

[0013] The preparation method of the basalt fiber base composite geotextile of the present invention includes the following steps:

[0014] (1) Prepare each component of the matrix asphalt, phenolic resin, styrene-butadiene rubber powder, setting agent, ethylene-vinyl acetate copolymer, and modifier in parts by weight for later use;

[0015] (2) Preheat the above raw materials, then raise the temperature and shear to obtain a modified high polymer, and then pour the obtained modified polymer into the coating tank;

[0016] (3) Unroll the basalt fiber grid cloth and slowly pull it through the coating tank to fully impregnate the basalt fiber grid cloth with the kneaded modified high polymer;

[0017] (4) Pull out the basalt fiber grid cloth impregnated with the modified high polymer from the coating tank, blow dry and cool it;

[0018] (5) Attach a functional protective film to the surface of the basalt fiber grid cloth of the dried and cooled composite modified high polymer, and cut it into rolls.

[0019] Preferably, the temperature during shearing in step (2) is 160°C to 190°C, and the shearing time is 1 to 3 hours.

[0020] Preferably, the basalt fiber grid cloth in step (3) is preheated to 110°C to 140°C, and the speed of pulling it through the coating tank is 0.2 m / s to 0.4 m / s.

[0021] Preferably, the speed of pulling the basalt fiber grid cloth out of the coating tank in step (4) is 0.2 m / s to 0.4 m / s; the blowing and cooling is carried out by using a cold air blower to fully cool it at a wind speed of 3 m / s to 6 m / s.

[0022] Preferably, the temperature of the coating tank is 190°C to 200°C.

[0023] Preferably, the dosage of the modified high polymer is 900 g / m 2 ~1200 g / m 2 .

[0024] Preferably, the modified high polymer layer tightly wraps the basalt fiber grid cloth. In the ESEM microscopic analysis method, the thickness of the asphalt infiltration interface layer formed by the fiber adsorbing asphalt is 1 μm to 10 μm, and the overall thickness of the composite geotextile is 1.5 mm to 2.0 mm.

[0025] Preferably, the prepared basalt fiber base composite geotextile has no cracks as a whole, the maximum tensile force ≥ 1.4 kN / 50 mm, the elongation at the maximum tensile force is 3% to 9%, the mass loss rate of thermal aging is ±2%, and the low temperature flexibility at -20°C is without cracks.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) The basalt fiber matrix composite geotextile has the advantages of fast adhesion, obvious crack resistance effect, good high temperature resistance and low temperature toughness. When actually repairing roads, it can be firmly bonded to the base layer, has a good stress absorption effect, and can effectively prevent the development of reflective cracks, and is very suitable for rapid repair and prevention of road cracks; (2) The high-performance basalt fiber matrix composite geotextile has strong tensile properties and good wrapping property between fiber bundles and modified high polymers; (3) The basalt fiber matrix composite geotextile is a new type of environmentally friendly material with low carbon emissions, meeting the requirements of "carbon peak" and "carbon neutrality"; (4) The preparation process of the basalt fiber matrix composite geotextile is simple, can be prefabricated in factories, and the actual construction is fast and convenient, which is beneficial to the rapid passage of roads and has a wide application; (5) The basalt fiber matrix composite geotextile uses a grid cloth type as the basalt fiber matrix, which can greatly reduce the use of raw materials without reducing performance, greatly reduce costs, has extremely high cost performance and marketability, and also refines the matrix specifications of basalt fibers and optimizes the best basalt fiber matrix composite geotextile. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic structural diagram of a basalt fiber grid cloth;

[0028] Figure 2 is a schematic structural diagram of a basalt grid composite geotextile;

[0029] Figure 3 is a schematic cross-sectional diagram of the interlayer of a pavement overlaid with a composite geotextile. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The technical solution of the present invention will be further described below in conjunction with specific examples.

[0031] The present invention provides a high-performance basalt fiber matrix composite geotextile, and the structural schematic diagram is as Figure 2 shown. In the figure, 1 is the upper functional protective film layer; 2 is the upper modified high polymer layer; 3 is the basalt fiber grid cloth layer; 4 is the lower modified high polymer layer; 5 is the lower functional protective film layer. The schematic cross-sectional diagram of the interlayer of a pavement overlaid with a composite geotextile is as Figure 3 shown. In the figure, 6-1 is the newly paved asphalt layer; 6-2 is the basalt fiber matrix composite geotextile; 6-3 is the extended crack; 6-4 is the base layer.

[0032] Example 1

[0033] The preparation steps of the basalt fiber matrix composite geotextile are as follows:

[0034] S101. Preparation of materials: Prepare 45 parts of matrix asphalt, 8 parts of styrene-butadiene rubber powder, 4 parts of diethylenetriamine, 15 parts of phenolic resin 2130, 3 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min, 2 parts of ethyl cellulose, 2 parts of hydroxypropyl methylcellulose, basalt fiber grid cloth (structural schematic diagram as shown in Figure 1 ), and polyethylene separator film. Among them, the density of the basalt fiber grid cloth is 110 g / m 2 .

[0035] S102. Preparation of modified high polymer: After preheating each raw material to above 100 °C, add 45 parts of matrix asphalt, 8 parts of styrene-butadiene rubber powder, 4 parts of diethylenetriamine, 15 parts of phenolic resin 2130, 3 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min, 2 parts of ethyl cellulose, and 2 parts of hydroxypropyl methylcellulose to the high-shear mixing machine in accordance with the component ratio in sequence, heat up to 175 °C and shear for 2.5 h to obtain the modified high polymer, and then pour the obtained modified polymer into the coating tank at 190 °C.

[0036] S103. Unroll the basalt fiber grid cloth, preheat it to 130 °C, and then slowly pull it through the coating tank at a speed of 0.3 m / s to fully impregnate the basalt fiber grid cloth with the kneaded modified high polymer;

[0037] S104. Pull out the basalt fiber grid cloth impregnated with the modified high polymer from the coating tank at a speed of 0.3 m / s, pass it through the rolling mill to the set thickness, and then use a cold air blower to fully dry and cool it at a wind speed of 5 m / s;

[0038] S105. Attach a polyethylene protective film to the surface of the dried and cooled basalt fiber grid cloth with the composite modified high polymer, and cut it into rolls.

[0039] Example 2

[0040] The preparation steps of the basalt fiber base composite geotextile are as follows:

[0041] S201. Preparation of materials: Prepare 48 parts of matrix asphalt, 10 parts of styrene-butadiene rubber powder, 5 parts of diethylenetriamine, 18 parts of phenolic resin 2130, 4 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min, 3 parts of ethyl cellulose, 3 parts of biomass cellulose, basalt fiber grid cloth, and polyethylene separator film. Among them, the density of the basalt fiber grid cloth is 120 g / m 2 .

[0042] S202. Prepare the modified high polymer: After preheating each raw material to above 100°C, add 48 parts of matrix asphalt, 10 parts of styrene-butadiene rubber powder, 5 parts of diethylenetriamine, 18 parts of phenolic resin 2130, 4 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min, 3 parts of ethyl cellulose, and 3 parts of biomass cellulose to the high-shear mixer in sequence according to the component ratio. Heat up to 175°C and shear for 2.5 h to obtain the modified high polymer, and then pour the obtained modified polymer into a coating tank at 190°C.

[0043] S203. Unroll the basalt fiber grid cloth, preheat it to 130°C in advance, and slowly pull it through the coating tank at a speed of 0.3 m / s to fully infiltrate the basalt fiber grid cloth with the mixed and refined modified high polymer.

[0044] S204. Pull out the basalt fiber grid cloth impregnated with the modified high polymer from the coating tank at a speed of 0.3 m / s. After passing through the rolling mill to the set thickness, use a cold air blower to fully dry and cool it at a wind speed of 5 m / s.

[0045] S205. Attach a polyethylene protective film to the surface of the basalt fiber grid cloth of the dried and cooled composite modified high polymer, and cut it into rolls.

[0046] Example 3

[0047] The preparation steps of the basalt fiber base composite geotextile are as follows:

[0048] S301. Prepare materials: Prepare 50 parts of matrix asphalt, 12 parts of styrene-butadiene rubber powder, 6 parts of ethylenediamine, 21 parts of phenolic resin 2130, 5 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min, 4 parts of hydroxypropyl methylcellulose, 4 parts of biomass cellulose, basalt fiber grid cloth, and polyethylene separator film. Among them, the density of the basalt fiber grid cloth is 130 g / m 2 .

[0049] S302. Prepare the modified high polymer: After preheating each raw material to above 100°C, add 50 parts of matrix asphalt, 12 parts of styrene-butadiene rubber powder, 6 parts of ethylenediamine, 21 parts of phenolic resin 2130, 5 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min, 4 parts of hydroxypropyl methylcellulose, and 4 parts of biomass cellulose to the high-shear mixer in sequence according to the component ratio. Heat up to 175°C and shear for 2.5 h to obtain the modified high polymer, and then pour the obtained modified polymer into a coating tank at 190°C.

[0050] S303. Unroll the basalt fiber grid cloth, pre-heat it to 130 °C, and then slowly pull it through the coating bath at a speed of 0.3 m / s to fully impregnate the basalt fiber grid cloth with the compounded modified high polymer;

[0051] S304. Pull out the basalt fiber grid cloth impregnated with the modified high polymer from the coating bath at a speed of 0.3 m / s. After passing through the rollers to the set thickness, use a cold air blower to fully dry and cool it at a wind speed of 5 m / s;

[0052] S305. Attach a polyethylene protective film to the surface of the basalt fiber grid cloth with the compounded modified high polymer after drying and cooling, and cut it into rolls.

[0053] Example 4

[0054] The preparation steps of the basalt fiber base composite geotextile are as follows:

[0055] S401. Prepare materials: Prepare 55 parts of matrix asphalt, 14 parts of styrene-butadiene rubber powder, 8 parts of ethylenediamine, 25 parts of phenolic resin 2131, 7 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min, 4 parts of ethyl cellulose, 4 parts of hydroxypropyl methyl cellulose, 4 parts of biomass cellulose, basalt fiber grid cloth, and polyethylene separator film. Among them, the density of the basalt fiber grid cloth is 160 g / m 2 .

[0056] S402. Prepare the modified high polymer: After pre-heating each raw material to above 100 °C, add 55 parts of matrix asphalt, 14 parts of styrene-butadiene rubber powder, 8 parts of ethylenediamine, 25 parts of phenolic resin 2131, 7 parts of ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min, 4 parts of ethyl cellulose, 4 parts of hydroxypropyl methyl cellulose, and 4 parts of biomass cellulose to the high-shear mixing machine in sequence according to the component ratio. Heat it up to 175 °C and shear for 2.5 h to obtain the modified high polymer, and then pour the obtained modified polymer into the coating bath at 190 °C.

[0057] S403. Unroll the basalt fiber grid cloth, pre-heat it to 130 °C, and then slowly pull it through the coating bath at a speed of 0.3 m / s to fully impregnate the basalt fiber grid cloth with the compounded modified high polymer;

[0058] S404. Pull out the basalt fiber grid cloth impregnated with the modified high polymer from the coating bath at a speed of 0.3 m / s. After passing through the rollers to the set thickness, use a cold air blower to fully dry and cool it at a wind speed of 5 m / s;

[0059] S405. Attach a polyethylene protective film to the surface of the basalt fiber grid cloth with the compounded modified high polymer after drying and cooling, and cut it into rolls.

[0060] Comparative Example 1

[0061] In this comparative example, a polyester fiberglass cloth base with a weight of 160 g / m 2 was used to replace the basalt fiber mesh cloth base in Example 4, and the other components, their dosages, and the preparation method were the same as those in Example 4.

[0062] Comparative Example 2

[0063] In this comparative example, a non-woven stress cloth base with a weight of 160 g / m 2 was used to replace the basalt fiber mesh cloth base in Example 4, and the other components, their dosages, and the preparation method were the same as those in Example 4.

[0064] Comparative Example 3

[0065] In this comparative example, a polyester filament geotextile with a weight of 160 g / m 2 was used to replace the basalt fiber mesh cloth base in Example 4, and the other components, their dosages, and the preparation method were the same as those in Example 4.

[0066] Comparative Example 4

[0067] In this comparative example, no modifier was added, and the other components, dosages, and the preparation method were the same as those in Example 4.

[0068] Comparative Example 5

[0069] In this comparative example, no setting agent was added, and the other components, dosages, and the preparation method were the same as those in Example 4.

[0070] Comparative Example 6

[0071] In this comparative example, no ethylene-vinyl acetate copolymer was added, and the other components, dosages, and the preparation method were the same as those in Example 4.

[0072] Comparative Example 7

[0073] In this comparative example, 15 parts of an ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min were added, and the other components, dosages, and the preparation method were the same as those in Example 4.

[0074] Comparative Example 8

[0075] In this comparative example, a basalt fiber plain cloth with a weight of 250 g / m 2 was used to replace the basalt fiber mesh cloth base in Example 4, and the other components, their dosages, and the preparation method were the same as those in Example 4.

[0076] Performance testing was carried out on a high-performance basalt fiber matrix composite geotextile provided by the present invention, and the test results are shown in Table 1 below; the test method refers to the Technical Specification for Application of Highway Geosynthetics JTG / T D32-2012 and the Polymer Modified Asphalt Crack Resistance Sticker for Asphalt Overlay JT / T 971-2015.

[0077] Table 1

[0078]

[0079] As can be seen from the table, for Comparative Examples 1, 2, 3, and 8, although their maximum tensile forces all meet the standard of ≥1.4 kN / 50 mm, the maximum tensile forces that the composite geotextiles with basalt fiber mesh fabrics designed in Example 4 of the present invention can withstand are 2.19 times, 2.77 times, 1.96 times, and 1.91 times of theirs respectively. From Comparative Example 8, it can be known that since the fiber fabric is formed by the intersection of warp and weft, through electron microscope scanning, it is found that there are areas where the modified high polymer is not wrapped at the intersection of the warp and weft, and it is found that the area where the modified high polymer is not wrapped in the plain weave fabric is much larger than that in the mesh fabric. Due to the existence of the unwrapped areas, the warp and weft are easily pulled and deformed, and the tensile resistance ability is weakened. Therefore, although the plain weave fabric is also woven from basalt fibers and the fiber dosage is 1.56 times that of the mesh fabric, its tensile resistance ability is much lower than that of the mesh fabric. It can be seen that the fabric type design of the present invention meets high performance while can greatly reduce the use of raw materials and lower the cost. For Comparative Examples 4 and 5, when no modifier or stabilizer is added, their thermal aging mass loss rates are both greater than the standard of ±2%, so the modifier and stabilizer added in the modified high polymer developed by the present invention have a synergistic effect of increasing viscosity and stabilizing, and can effectively ensure the high-temperature performance and bonding performance of the modified high polymer. From Comparative Examples 6 and 7, it can be known that the ethylene-vinyl acetate copolymer with a vinyl acetate content of 40% and a melt index of 25 g / 10 min added in the modified high polymer developed by the present invention can effectively improve the low-temperature flexibility, but adding too much will also cause a decrease in tensile strength and an increase in brittleness, thus generating cracks. Therefore, the present invention has developed an appropriate addition range to ensure its comprehensive performance.

[0080] Generally speaking, the geotextile composed of basalt grid cloth and modified high polymer in the present invention has high tensile strength, good high temperature stability and excellent low temperature flexibility. It can play a good crack resistance performance in actual use. And because it is basalt fiber grid cloth, it can increase the contact area and interfacial friction force with the modified high polymer, greatly improving the interlayer bonding effect and improving the interlayer slip phenomenon. From the test data of the embodiments, the present invention not only well meets the requirements of conventional projects for composite geotextiles, but also greatly reduces the material usage amount, thus reducing the cost. With the popularization of the high-performance basalt fiber matrix composite geotextile of the present invention, it can not only greatly reduce the influence of reflective cracks on the surface layer, but also achieve rapid road repair and restore normal traffic during actual construction.

Claims

1. A basalt fiber base composite geotextile, characterized in that, It includes a functional protective film layer, a modified high-polymer layer and a basalt fiber mesh layer. From top to bottom, they are the upper functional protective film layer (1), the upper modified high-polymer layer (2), the basalt fiber mesh layer (3), the lower modified high-polymer layer (4), and the lower functional protective film layer (5). The protective film is a polyethylene isolation film; The modified high-polymer layer comprises raw materials in the following weight parts: 45-55 parts of matrix asphalt, 15-25 parts of phenolic resin, 8-14 parts of styrene-butadiene rubber powder, 4-8 parts of a setting agent, 3-7 parts of ethylene-vinyl acetate copolymer, and 4-12 parts of a modifier; wherein, the modifier is at least one of ethyl cellulose, biomass cellulose and hydroxypropyl methyl cellulose, and the setting agent is ethylenediamine or diethylenetriamine.

2. The basalt fiber matrix composite geotextile according to claim 1, wherein The density of the basalt fiber mesh fabric base is 110~160 g / m 2 .

3. A method for preparing the basalt fiber base composite geotextile according to any one of claims 1 to 2, characterized in that, It includes the following steps: (1) Prepare each component according to the weight parts of matrix asphalt, phenolic resin, styrene-butadiene rubber powder, setting agent, ethylene-vinyl acetate copolymer and modifier for later use; (2) Perform preheating treatment on the above raw materials, then raise the temperature for shearing to obtain a modified high-polymer, and then pour the obtained modified polymer into a coating tank; (3) Unroll the basalt fiber mesh and slowly pull it through the coating tank to fully infiltrate the basalt fiber mesh with the compounded modified high-polymer; (4) Pull out the basalt fiber mesh impregnated with the modified high-polymer from the coating tank, and blow-dry and cool it; (5) Attach a functional protective film to the surface of the basalt fiber mesh of the compounded modified high-polymer after blow-drying and cooling, and cut it into rolls.

4. The preparation method of the basalt fiber matrix composite geotextile according to claim 3, characterized in that, The temperature during shearing in step (2) is 160°C to 190°C, and the shearing time is 1 to 3 hours.

5. The preparation method of the basalt fiber base composite geotextile according to claim 3, characterized in that The temperature of the coating tank is 190°C to 200°C.

6. The preparation method of the basalt fiber base composite geotextile according to claim 3, characterized in that, The modified high polymer layer tightly wraps the basalt fiber grid cloth. In the ESEM microscopic analysis method, the thickness of the asphalt infiltration interface layer formed by the fiber adsorbing asphalt is 1 ~10 , and the overall thickness of the composite geotextile is 1.5 mm to 2.0 mm.

7. The preparation method of the basalt fiber base composite geotextile according to claim 3, characterized in that, The prepared basalt fiber matrix composite geotextile has no cracks as a whole, the maximum tensile force ≥ 1.4 kN / 50 mm, the mass loss rate of heat aging is ±2%, and the low-temperature flexibility at -20°C has no cracks.

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