Polyolefin film with high puncture resistance and wear resistance and preparation method thereof

Abstract

The invention relates to the field of high polymer material processing, provides a high-puncture-resistance wear-resistant polyolefin film and a preparation method thereof, and successfully prepares an ultra-high molecular weight polyethylene porous film with a compact and wear-resistant surface layer and a porous high-strength gradient structure in a core layer through an innovative process of combining'wet-process two-way synchronous stretching 'and'gradient surface densification'. The material has excellent mechanical properties and excellent surface tribological properties while realizing ultrathin and light weight. The method is suitable for the fields of consumer electronics protection, sports equipment, medical equipment and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer material processing, specifically to a highly puncture-resistant and abrasion-resistant polyolefin film and its preparation method. Background Technology

[0002] Ultra-high molecular weight polyethylene (UHMWPE) possesses excellent abrasion resistance, high impact strength, and a low coefficient of friction due to its extremely high molecular weight, and is widely used in artificial joints, safety protection, and industrial wear-resistant components. However, in practical applications, traditional UHMWPE materials and their modified products face two prominent technical challenges:

[0003] Firstly, there is a contradiction between lightweight materials and high mechanical properties. UHMWPE products prepared using traditional processes (such as molding and die casting) have low internal crystallinity and random molecular chain orientation, resulting in limited intrinsic mechanical strength. To meet the required strength and wear resistance, it is often necessary to increase the product thickness or add large amounts of inorganic fillers. However, this directly leads to heavy products with reduced flexibility, making it difficult to meet the modern industrial demands for thinner and lighter products. For example, in the prior art, patent CN114634663A discloses a wear-resistant composite material of ultra-high molecular weight polyethylene (UHMWPE) and zirconium tungstate. Its technical solution uses a traditional molding process: UHMWPE powder and zirconium tungstate particles are physically blended, then the mixture is placed in a mold and hot-pressed at a temperature of 160-185℃ using a "gradient pressurization method," finally cooling and demolding to obtain the product. This technology improves wear resistance by adding exogenous hard particles (zirconium tungstate), but its reinforcement mechanism has limitations. Performance improvement relies entirely on the addition of these exogenous hard particles; the process itself does not alter the disordered and unoriented original state of the UHMWPE molecular chains, thus limiting its potential for improving the material's intrinsic strength. To pursue higher performance, the traditional approach is to increase the filler ratio or the product thickness, which directly conflicts with the modern industrial goals of "thinning" and "lightweighting." The core of the process is static mold hot pressing, which cannot perform high-ratio directional stretching of the material, thus preventing the construction of a highly oriented fibrous crystal network internally. This makes it difficult to achieve breakthroughs in properties such as puncture resistance and tear resistance, which depend on the toughness of the network.

[0004] Secondly, there is a contradiction in the difficulty of synergistically improving surface tribological properties and bulk mechanical properties. Existing technologies typically employ physical blending of functional fillers to improve surface lubricity. However, this "integral blending" modification method only focuses on surface properties and does not alter the disordered, weakly oriented microstructure within the UHMWPE matrix. Therefore, it cannot simultaneously improve the material's intrinsic toughness, impact resistance, and puncture resistance. Furthermore, improving performance through methods such as gamma-ray crosslinking can easily trigger oxidative degradation of the material, affecting long-term stability. For example, patent CN117209875A discloses a technical solution for improving the surface properties of UHMWPE by introducing functional fillers. The core of this technology is to first prepare manganese phosphate trihydrate nanosheets with lubrication potential, and then mechanically blend these nanosheet powders with ultra-high molecular weight polyethylene (UHMWPE) resin powder to achieve uniform mixing on a macroscopic scale. The mixed powder is then loaded into a mold and hot-pressed at 160-180°C to melt the UHMWPE, while pressure (up to 120-150 MPa) is applied to shape and solidify the material. During the friction process, the added manganese phosphate nanosheets are designed to form a lubricating protective film on the material surface, thereby reducing the coefficient of friction and wear. However, this patent only optimizes lubrication for the "surface" where the material contacts the external environment. The entire process does not alter the internal microstructure of the UHMWPE matrix at all, and does not actively reinforce the arrangement, orientation, or crystal morphology of the polymer molecular chains. Since the matrix structure itself is not strengthened, the intrinsic toughness, impact resistance, and puncture resistance of the material depend entirely on the upper limit of the original UHMWPE resin's performance. Adding hard nanosheets may even slightly impair the matrix's toughness due to stress concentration.

[0005] Therefore, there is an urgent need in this field for an innovative preparation method that can start from the microstructure design of the material and simultaneously achieve high strength, high toughness, excellent puncture resistance, and low surface friction and high wear resistance of UHMWPE film without relying on large-scale thickening or a large amount of exogenous fillers, thereby truly solving the above-mentioned technical bottlenecks. Summary of the Invention

[0006] In view of the prior art, this application proposes a highly puncture-resistant and abrasion-resistant polyolefin film to at least solve one of the problems existing in the related art. To achieve this objective, the present invention is implemented through the following technical solution.

[0007] The first aspect of the present invention provides a highly puncture-resistant and abrasion-resistant polyolefin film, the raw materials for which are prepared by weight include 100 parts of thermoplastic resin, 55-65 parts of plasticizer, and 0.3-0.6 parts of antioxidant.

[0008] Preferably, the thermoplastic resin includes, but is not limited to, one or more of ultra-high molecular weight polyethylene (UHMWPE), high-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP).

[0009] Preferably, the molecular weight of the UHMWPE is 3.0 × 10⁻⁶. 6 ~ 1.1×10 7 g / mol.

[0010] In some preferred embodiments, the thermoplastic resin may be a blend of UHMWPE with HDPE, LLDPE, or PP.

[0011] Preferably, the plasticizer includes one or more of liquid paraffin, dioctyl phthalate (DOP), paste paraffin, polyethylene wax, and stearate.

[0012] Preferably, the antioxidant includes one or more of antioxidant 1076, antioxidant 168, antioxidant B900, antioxidant PEPQ, and antioxidant KY-245.

[0013] In some preferred embodiments, the antioxidant is antioxidant 1076 and antioxidant 168 in a mass ratio of 1:1.

[0014] The method for preparing the high puncture-resistant and abrasion-resistant polyolefin film includes the following steps:

[0015] S1: Raw material premixing: Weigh the dried thermoplastic resin, plasticizer, and antioxidant according to the formula ratio, mix them at 80°C to ensure that each component is initially mixed evenly, and obtain the premix;

[0016] S2: Precursor sheet forming: The premixed material is fed into a twin-screw extruder for melt blending, and then cast onto a cooling roller through a T-die to form a uniform precursor sheet;

[0017] S3: Biaxial stretching and orientation: The precursor sheet is preheated, and after preheating, it is subjected to asynchronous or synchronous biaxial stretching to orient the molecular chains.

[0018] S4: Heat setting: The stretched film is heat-set to stabilize its orientation structure;

[0019] S5: Extraction to form pores: The heat-set membrane is immersed in the extraction solution and subjected to ultrasonic extraction to remove the plasticizer and form a porous membrane.

[0020] S6: Drying: Place the extracted membrane in an oven to dry it completely to remove residual solvent and obtain a pure porous membrane.

[0021] S7: Surface densification treatment: The porous film is subjected to hot rolling surface densification treatment using a mirror hot press or a high-precision two-roll calender to obtain a high puncture-resistant and abrasion-resistant polyolefin film.

[0022] Preferably, in step S2, the thickness of the precursor sheet is 3-4 mm; the melt blending temperature is 180-240℃, and the screw speed is 200-400 rpm; preferably, the melt blending temperature is 200℃, and the screw speed is 250 rpm.

[0023] Preferably, in step S3, the preheating temperature is 80-110℃, the stretching temperature is 130-140℃, the longitudinal (MD) stretching ratio is 4-16 times, and the transverse (TD) stretching ratio is 4-16 times; preferably, the preheating temperature is 90℃, the stretching temperature is 138℃, the longitudinal (MD) stretching ratio is 14 times, and the transverse (TD) stretching ratio is 14 times.

[0024] In some preferred embodiments, the stretching in step S3 is performed at least once or more, as long as the required stretching ratio is achieved.

[0025] Preferably, in step S4, the temperature of the heat setting treatment is 100-130℃; more preferably, it is 110℃.

[0026] Preferably, in step S5, the extractant used is a volatile solvent, the extraction temperature is 40-50℃, and the extraction time is 20-40 min; more preferably, the extraction temperature is 50℃ and the extraction time is 30 min.

[0027] Preferably, the volatile solvent includes, but is not limited to, dichloromethane and n-hexane.

[0028] Preferably, in step S5, the specific conditions for ultrasonic treatment are: power of 250-350W and frequency of 40kHz.

[0029] Preferably, in step S6, the drying temperature is 50-60°C; more preferably, it is 60°C.

[0030] Preferably, in step S7, the temperature of the roller used for hot roller surface densification treatment is 135-145℃, and the linear pressure is 5-15kN / cm; more preferably, the roller temperature is 140℃, and the linear pressure is 13kN / cm.

[0031] In some preferred embodiments, an annealing process may be added between steps S6 and S7 to eliminate internal stress and improve dimensional stability.

[0032] In some preferred embodiments, the hot rolling surface densification process in step S7 can be performed in a single pass or multiple passes (e.g., low pressure followed by high pressure), continuous rolling or intermittent rolling, to obtain a smoother or specific surface layer.

[0033] In some preferred embodiments, after the surface densification treatment by hot rolling in step S7, the treated film is cooled and shaped by cooling rollers, and then wound up to obtain a high puncture-resistant and abrasion-resistant polyolefin film.

[0034] The high puncture and abrasion resistant polyolefin film described in this invention can be applied to consumer electronics protection (such as batteries, circuit boards, etc.), sports equipment (such as helmets, skis, etc.), medical devices (such as artificial joints), and other fields.

[0035] By adopting a physical modification path that combines "wet biaxial stretching" and "gradient surface densification", a dense, smooth, and non-porous integrated surface layer is constructed in situ at the location where wear resistance is most needed, without damaging or sacrificing the existing highly oriented, porous, and tough structure of the core layer. This truly achieves the integrated synergy of ultra-wear-resistant film surface and high strength and toughness of the film body.

[0036] Traditional die-casting or molding processes for UHMWPE wear-resistant parts often suffer from low crystallinity, low orientation, and random crystal morphology due to the lack of effective molecular chain orientation and crystallization control during processing. This directly leads to three major performance bottlenecks: limited mechanical strength (tensile strength, modulus) in specific directions, insufficient puncture resistance, and the need to increase thickness to achieve target strength, making it difficult to meet lightweight requirements. While improving the surface properties of UHMWPE through "blending-dispersion" functional fillers is a mainstream method, it is essentially a holistic modification. Although uniform dispersion of fillers in the material can improve surface lubrication to some extent, it cannot selectively strengthen the surface layer. In fact, it may affect the matrix homogeneity due to interface issues, and it does not change the inherent weak orientation and non-porous bulk microstructure of UHMWPE.

[0037] This invention abandons the traditional approach of relying on thickness and fillers, and actively constructs a highly oriented fibrous crystal network at the molecular level through a wet biaxial stretching process. This not only fundamentally and significantly improves the intrinsic strength, modulus, and puncture toughness of the material, but also enables the material to achieve higher specific strength at a thinner thickness, thus successfully breaking through the traditional bottleneck of the difficulty in balancing strength and lightweight. Simultaneously, a new approach of "selective surface reconstruction" is proposed. Through precisely controlled hot-pressing conditions, the material's surface layer is precisely targeted, causing it to melt, flow, and recrystallize. This method is additive-free and non-monomeric, constructing a dense, smooth, and non-porous integrated surface layer in situ at the location where wear resistance is most needed, without damaging or sacrificing the existing highly oriented, porous, and tough structure of the core layer. This truly achieves a synergistic integration of ultra-wear-resistant surface and high strength and toughness of the bulk material.

[0038] First, through high-ratio biaxial stretching in step S3, the UHMWPE molecular chains are highly oriented in two directions within the plane, transforming the original spherulites or folded chain crystals into a large number of oriented fibrous crystals. This creates a three-dimensional network framework composed of highly oriented fibrous crystals in situ within the film, simultaneously forming a uniformly distributed microporous structure. This process fundamentally and significantly improves the material's intrinsic tensile strength, modulus, and puncture resistance, enabling the film to withstand extremely high mechanical loads even at extremely thin (micrometer-scale) thicknesses, resolving the contradiction between lightweight and high strength. Second, the surface densification treatment in step S7 precisely controls the temperature (above the glass transition temperature but below the melting temperature of the main fibrous crystals) and pressure of the hot rolling press, causing melting and recrystallization only at a micrometer-scale depth on the film surface. This achieves "selective surface reconstruction," forming a dense, smooth, non-porous, wear-resistant surface layer while preserving the integrity of the porous orientation structure of the core layer. This surface layer effectively reduces surface roughness, significantly decreasing the actual contact area and shear stress during frictional contact, thereby achieving a stable and extremely low coefficient of friction and wear rate, solving the problem of the difficulty in coexisting with surface wear resistance and bulk toughness. The synergy of the two processes provides the internal oriented structure with a skeleton to resist puncture and deformation, while simultaneously increasing the material's initial melting temperature and broadening the process window for surface treatment; while the dense surface layer protects the internal structure from direct frictional damage and inhibits the initiation and propagation of cracks. The combination of these two technologies successfully overcomes the traditional dilemma of balancing strength, wear resistance, and lightweight, enabling this porous membrane to maintain ultra-thin and lightweight properties while still possessing high mechanical strength, high puncture resistance, and wear-resistant, low-friction surface characteristics, ultimately achieving a leapfrog improvement in the overall performance of the thin film.

[0039] The embodiments of the present invention have the following beneficial effects:

[0040] 1. This invention successfully prepared an ultra-high molecular weight polyethylene porous membrane with a dense and wear-resistant surface layer and a porous, high-strength gradient structure in the core layer through an innovative process combining "wet bidirectional synchronous stretching" and "gradient surface densification". This material achieves ultra-thin and lightweight properties while also possessing excellent mechanical properties and superior surface tribological properties.

[0041] 2. This invention uses a stretching process to construct a three-dimensional network framework composed of highly oriented fibrous crystals in situ inside the material, and simultaneously forms a uniformly distributed microporous structure.

[0042] 3. The present invention uses precisely controlled hot pressing conditions to cause melting, flow and recrystallization only in the surface layer of the material (micrometer-level depth), thereby forming a dense, smooth, non-porous wear-resistant surface layer while preserving the integrity of the porous orientation structure of the core layer.

[0043] 4. This invention successfully overcomes the contradiction between the traditional material strength, wear resistance and lightweight, so that the porous membrane can maintain ultra-thin and lightweight while still having high mechanical strength, high puncture resistance and wear-resistant and low friction surface properties. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below. However, those skilled in the art will understand that many technical details are presented in the various embodiments of the present invention to enable readers to better understand this application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in this application can be implemented. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0045] All raw materials used in this invention are commercially available, as detailed below:

[0046] Ultra-high molecular weight polyethylene, sourced from Dongguan Taotao Plastic Raw Materials Co., Ltd.

[0047] Liquid paraffin, from Guangzhou Haihong Chemical Co., Ltd., product name: Liquid Paraffin.

[0048] Dichloromethane, sourced from Shandong Hongrun Chemical Co., Ltd., is marketed as monobromodichloromethane.

[0049] Antioxidant 1076 is from Dongguan Kangjin New Material Technology Co., Ltd., and its trade name is Antioxidant 1076.

[0050] Antioxidant 168 is from Dongguan Kangjin New Material Technology Co., Ltd., and its product name is Antioxidant 168.

[0051] Example 1

[0052] This embodiment provides a highly puncture-resistant and abrasion-resistant polyolefin film, the raw materials for which, by weight, are prepared, including 100 parts of thermoplastic resin, 60 parts of plasticizer, and 0.5 parts of antioxidant.

[0053] The thermoplastic resin is ultra-high molecular weight polyethylene (UHMWPE).

[0054] The molecular weight of the UHMWPE is 9.0 × 10⁻⁶. 6 g / mol.

[0055] The plasticizer is liquid paraffin.

[0056] The antioxidants are antioxidant 1076 and antioxidant 168 in a mass ratio of 1:1.

[0057] The preparation method of the high puncture resistance and abrasion resistance polyolefin film includes the following steps:

[0058] S1: Raw material premixing: Weigh the dried thermoplastic resin, plasticizer, and antioxidant according to the formula ratio, and stir and mix them at 80℃ for 30 minutes to obtain the premix.

[0059] S2: Precursor sheet forming: The premixed material is fed into a twin-screw extruder for melt blending, and then cast onto a cooling roller through a T-die to form a uniform precursor sheet;

[0060] S3: Biaxial stretching and orientation: The precursor sheet is preheated, and after preheating, it is subjected to asynchronous or synchronous biaxial stretching to orient the molecular chains.

[0061] S4: Heat setting: The stretched film is heat-set to stabilize its orientation structure;

[0062] S5: Extraction to form pores: The heat-set membrane is immersed in the extraction solution and subjected to ultrasonic extraction to remove the plasticizer and form a porous membrane.

[0063] S6: Drying: Place the extracted membrane in an oven to dry it completely to remove residual solvent and obtain a pure porous membrane.

[0064] S7: Surface densification treatment: The porous film is subjected to hot roll densification treatment using a mirror hot press or a high-precision two-roll calender. The treated film is then cooled and shaped by a cooling roller and then wound up to obtain a high puncture-resistant and abrasion-resistant polyolefin film.

[0065] In step S2, the thickness of the precursor sheet is 3.5 mm; the melt blending temperature is 200°C; and the screw speed is 250 rpm.

[0066] In step S3, the preheating temperature is 90°C, the stretching temperature is 138°C, the longitudinal (MD) stretching ratio is 14 times, and the transverse (TD) stretching ratio is 14 times.

[0067] In step S4, the temperature for heat setting is 110°C.

[0068] In step S5, the extraction solution used is a volatile solvent, the extraction temperature is 50°C, and the extraction time is 30 min.

[0069] The volatile solvent is dichloromethane.

[0070] In step S5, the specific conditions for ultrasonic treatment are: power of 300W and frequency of 40kHz.

[0071] In step S6, the drying temperature is 60°C.

[0072] In step S7, the temperature of the roller undergoing hot roller pressing for surface densification is 140°C, and the linear pressure is 13 kN / cm.

[0073] Example 2 (Change in stretch ratio)

[0074] This embodiment provides a high puncture resistance and abrasion resistance polyolefin film. The specific implementation method is the same as that in embodiment 1, except that the biaxial stretching ratio of MD and TD in step S3 is changed from 14 times to 8 times.

[0075] Example 3 (Tension Temperature Change)

[0076] This embodiment provides a high puncture-resistant and abrasion-resistant polyolefin film. The specific implementation method is the same as that in embodiment 1, except that the stretching temperature in step S3 is changed from 138°C to 133°C.

[0077] Example 4 (Change in linear pressure)

[0078] This embodiment provides a high puncture resistance and abrasion resistance polyolefin film. The specific implementation method is the same as that in embodiment 1, except that the linear pressure in step S7 is changed from 13 kN / cm to 8 kN / cm.

[0079] Example 5 (Roller Temperature Change)

[0080] This embodiment provides a high puncture and abrasion resistant polyolefin film. The specific implementation method is the same as that in embodiment 1, except that the roller temperature in step S7 is changed from 140°C to 137°C.

[0081] Comparative Example 1 (Traditional Die Casting Method)

[0082] This comparative example provides a highly puncture-resistant and abrasion-resistant polyolefin film, which, by weight, comprises 100 parts of thermoplastic resin and 25 parts of zirconium tungstate; the molecular weight of the UHMWPE is 9.0 × 10⁻⁶. 6 g / mol.

[0083] Sample preparation was performed using the method described in the example of CN114634663A.

[0084] Comparative Example 2 (Traditional methods for optimizing material surfaces)

[0085] This comparative example provides a highly puncture-resistant and abrasion-resistant polyolefin film prepared from manganese phosphate trihydrate nanosheets: synthesized according to the method of Example 1 in CN117209875A; the highly puncture-resistant and abrasion-resistant polyolefin film, by weight, comprises 100 parts of thermoplastic resin and 7.53 parts of manganese phosphate trihydrate nanosheets; the molecular weight of the UHMWPE is 9.0 × 10⁻⁶. 6 g / mol.

[0086] Samples were prepared using the method described in Example 2 of CN117209875A.

[0087] Comparative Example 3 (without hot pressing)

[0088] This comparative example provides a high puncture and abrasion resistant polyolefin film. The specific implementation method is the same as that in Example 1, except that step S7 (surface densification treatment) is completely omitted, and S8 winding is performed directly after extraction and drying in S5.

[0089] Comparative Example 4 (Stretch Ratio Exceeding Boundary)

[0090] This comparative example provides a high puncture resistance and abrasion resistance polyolefin film. The specific implementation method is the same as that in Example 1, except that the biaxial stretching ratio of MD and TD in step S3 is increased from 14 times to 18 times.

[0091] Comparative Example 5 (Tension Temperature Exceeds Boundary)

[0092] This comparative example provides a highly puncture-resistant and abrasion-resistant polyolefin film. The specific implementation method is the same as that in Example 1, except that the stretching temperature in step S3 is reduced from 138°C to 125°C.

[0093] Comparative Example 6 (Linear Pressure Exceeds Boundary)

[0094] This comparative example provides a highly puncture-resistant and abrasion-resistant polyolefin film. The specific implementation method is the same as that in Example 1, except that the linear pressure in step S7 is increased from 13 kN / cm to 18 kN / cm.

[0095] Comparative Example 7 (Roller temperature exceeds the boundary)

[0096] This comparative example provides a highly puncture-resistant and abrasion-resistant polyolefin film. The specific implementation method is the same as that in Example 1, except that the roller temperature in step S7 is increased from 140°C to 150°C.

[0097] Performance testing

[0098] 1. Tensile strength:

[0099] Test standard: Refer to national standard GB / T 1040.3-2006.

[0100] Testing instrument: Electronic universal testing machine.

[0101] Test parameters: Sample size: 150mm×15mm, with two parallel markings spaced 50mm apart in the middle.

[0102] Fixture spacing: 100mm.

[0103] Test speed: 250 mm / min.

[0104] Prestress: controlled at ≤10 -2 F0.

[0105] Results show that the tensile strength (MPa) of 5 specimens was recorded, and the average values ​​for the longitudinal and transverse directions were taken respectively.

[0106] 2. Thickness test:

[0107] Test standard: Refer to national standard GB / T 6672-2001.

[0108] Testing instrument: Thin film thickness gauge.

[0109] Test parameters: Measuring head pressure: 0.1 MPa.

[0110] Results are as follows: 10 points were randomly measured on each sample, and the average value was taken. The unit is micrometers (μm).

[0111] 3. Puncture resistance test:

[0112] Testing standard: Refer to national standard GB / T 37841-2019.

[0113] Testing instrument: Thin film puncture force tester.

[0114] Test parameters: Puncture needle: diameter (1.00±0.05) mm, stainless steel, tip angle (30±1)°.

[0115] Ring clamp: 50mm in diameter, increases the clamping ring pressure to prevent tensile deformation of the sample.

[0116] Puncture speed: 200 mm / min.

[0117] Sample size: 100mm × 100mm.

[0118] The results show that the maximum puncture force (N) of 5 specimens was recorded, the average value was taken, and the puncture resistance strength (Fp=F0 / d, unit N / mm) was calculated.

[0119] The results of the thickness, puncture resistance, and tensile strength tests are shown in Table 1.

[0120] 4. Dynamic / static friction coefficient test

[0121] Testing standard: Refer to national standard GB / T 10006-2021

[0122] Testing instrument: Friction coefficient meter (including 200g standard slider, bottom area 63mm×63mm)

[0123] Test parameters: Number of samples ≥ 5 (200mm × 63mm); Pretreatment at 23℃±2℃ and 50%±5% RH for ≥ 4 hours;

[0124] The slider speed is 100 mm / min; the contact rest time is 30 seconds; the test surface is a film / film (or film / metal); one set of dynamic and static friction data is acquired simultaneously in one test.

[0125] The results show that: for each piece, one set of dynamic / static friction coefficients (μs / μd) was tested, and the average value of 5 valid tests was taken. The unit is dimensionless; the results are shown in Table 2.

[0126] 5. Wear and tear test

[0127] Test standard: Refer to national standard GB / T 5478-2008.

[0128] Test instruments: Taber abrasion tester (equipped with CS-10 standard grinding wheel, 250g weight load, speed controller (60r / min), analytical balance with accuracy ≥0.01mg).

[0129] Test parameters: Sample size: 100mm×100mm, quantity ≥3 pieces; Pretreatment at 23℃±2℃ and 50%±5% RH for ≥4h; Load 250g, rotation speed 60r / min, tested at 500 rpm and 1000 rpm respectively; Dust collection device turned on during the test.

[0130] Results are expressed as mass loss (mg). The mass difference before and after wear of each sample after 500 and 1000 revolutions was calculated. The average value of 3 tests was taken. The results are shown in Table 3.

[0131] Table 1

[0132]

[0133] Table 2

[0134]

[0135] Table 3

[0136]

[0137] As can be seen from Tables 1, 2, and 3, the porous membrane prepared in Example 1 of this invention, with a thickness of only 15 μm, achieves a puncture resistance of 14.8 N, a maximum tensile strength (MD) of 570 MPa, a maximum tensile strength (TD) of 480 MPa, and a specific puncture strength of 0.95 N / μm. It also exhibits a low coefficient of friction (static friction coefficient 0.120, dynamic friction coefficient 0.106) and minimal wear mass loss (2.1 mg after 1000 revolutions). In contrast, the sample prepared by Comparative Example 1 (conventional die-casting method) has a thickness of 200 μm, but its tensile strength and puncture resistance are extremely low (MD tensile strength 45 MPa, puncture resistance / ); the sample prepared by Comparative Example 2 (conventional surface optimization method) has a low surface friction coefficient (static friction coefficient 0.09, dynamic friction coefficient 0.07), but its tensile strength and puncture resistance are still low (MD tensile strength 50 MPa, no puncture resistance).

[0138] Compared with Example 1, Examples 2, 3, 4, and 5 showed some changes in performance by adjusting key process parameters, but all were superior to Comparative Examples 1 and 2. Comparative Example 3 (without hot pressing) maintained high tensile strength (MD tensile strength 500 MPa, TD tensile strength 430 MPa), but had a high coefficient of friction (static friction coefficient 0.191, dynamic friction coefficient 0.182) and significant wear mass loss (7.2 mg after 1000 revolutions), indicating poor surface wear resistance when the surface was not densified.

[0139] Comparative Examples 4, 5, 6, and 7, by adjusting key process parameters beyond the scope of the claims, show that when the stretching ratio, stretching temperature, linear pressure, or roller temperature exceeds a reasonable range, the material properties all decrease, further proving the scientific nature and necessity of the process parameter settings of the present invention.

[0140] In summary, this invention successfully prepared an ultra-high molecular weight polyethylene porous membrane with a unique gradient structure of "dense and wear-resistant surface layer and porous and high-strength core layer" through an innovative process combining "wet biaxial synchronous stretching-extraction" and "precise surface hot-pressing densification". Test data shows that this material achieves ultra-thin and lightweight properties (thickness ≤15μm) while possessing excellent mechanical properties (MD tensile strength ≥570MPa, TD tensile strength ≥480MPa, specific puncture strength >0.95N / μm) and superior surface tribological properties (average kinetic friction coefficient <0.11, mass loss after wear ≤2.1mg / 1000 rpm), comprehensively solving a long-standing technical contradiction in this field. The comparative results further demonstrate that "biaxial stretching" and "gradient surface treatment" are indispensable core technical features for achieving the aforementioned effects.

[0141] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A highly puncture-resistant and abrasion-resistant polyolefin film, characterized in that, The raw materials for its preparation, by weight, include 100 parts of thermoplastic resin, 55-65 parts of plasticizer, and 0.3-0.6 parts of antioxidant; the thermoplastic resin includes, but is not limited to, one or more of ultra-high molecular weight polyethylene, high-density polyethylene, linear low-density polyethylene, and polypropylene; the ultra-high molecular weight polyethylene has a molecular weight of 3.0 × 10⁻⁶. 6 ~ 1.1×10 7 g / mol.

2. The high puncture resistance and abrasion resistance polyolefin film according to claim 1, characterized in that, The plasticizer includes one or more of liquid paraffin, dioctyl phthalate, paste paraffin, polyethylene wax, and stearate.

3. The high puncture resistance and abrasion resistance polyolefin film according to claim 1, characterized in that, The antioxidants include one or more of antioxidants 1076, antioxidant 168, antioxidant B900, antioxidant PEPQ, and antioxidant KY-245.

4. A method for preparing a high puncture-resistant and abrasion-resistant polyolefin film according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Raw material premixing: Weigh the dried thermoplastic resin, plasticizer, and antioxidant according to the formula ratio, mix them, and ensure that each component is initially mixed evenly to obtain a premix; S2: Precursor sheet forming: The premixed material is melted and blended, and then cast onto the cooling roller through a T-die to form a uniform precursor sheet; S3: Biaxially stretched orientation: After preheating the precursor sheet, it is subjected to biaxial stretching; S4: Heat setting: Heat setting the stretched film; S5: Extraction and Pore Formation: The heat-set membrane is immersed in the extraction solution and subjected to ultrasonic extraction to form a porous membrane. S6: Drying: Place the extracted membrane in an oven to dry, and obtain a pure porous membrane; S7: Surface densification treatment: The porous membrane is subjected to hot roll pressing surface densification treatment to obtain a high puncture resistance and wear resistance polyolefin film.

5. The method for preparing a high puncture-resistant and abrasion-resistant polyolefin film according to claim 4, characterized in that, In step S2, the thickness of the precursor sheet is 3-4 mm; the melt blending temperature is 180-240℃; and the screw speed is 200-400 rpm.

6. The method for preparing a high puncture-resistant and abrasion-resistant polyolefin film according to claim 4, characterized in that, In step S3, the preheating temperature is 80-110℃, the stretching temperature is 130-140℃, the longitudinal stretching ratio is 4-16 times, and the transverse stretching ratio is 4-16 times.

7. The method for preparing a high puncture-resistant and abrasion-resistant polyolefin film according to claim 4, characterized in that, In step S1 and step S4, the temperature of the heat setting treatment is 100-130℃.

8. The method for preparing a high puncture-resistant and abrasion-resistant polyolefin film according to claim 4, characterized in that, In step S5, the extractant used is a volatile solvent, the extraction temperature is 40-50℃, and the extraction time is 20-40 min.

9. The method for preparing a high puncture-resistant and abrasion-resistant polyolefin film according to claim 4, characterized in that, In step S2 and step S6, the drying temperature is 50-60℃.

10. The method for preparing a high puncture-resistant and abrasion-resistant polyolefin film according to claim 4, characterized in that, In step S7, the temperature of the roller used for hot roller surface densification treatment is 135-145℃, and the linear pressure is 5-15kN / cm.

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