CN105885081A - Plasma modification method for polytetrafluoroethylene microporous membrane - Google Patents

Abstract

The invention discloses a plasma modification method for a polytetrafluoroethylene microporous membrane. A low temperature plasma treatment method is adopted for conducting surface modification on the PTFE microporous membrane, process parameters of low-temperature plasma treatment, such as the low-temperature plasma gas type, the treatment distance, the radio-frequency power, the treatment time and the gas circulation volume, are controlled, hydrophilia of the PTFE microporous membrane is improved, the PTFE microporous membrane which is originally quite great in hydrophobicity is modified into the PTFE microporous membrane which is quite great in hydrophilia, the water contact angle is lowered to approximately 40 degrees from the original approximately 13 degrees, and meanwhile mechanical strength of the PTFE microporous membrane is maintained. The plasma modification method is short in cycle and low in cost, commercialized production can be conducted, and the application scope of the PTFE microporous membrane is further expanded.

Description

A method for plasma modification of polytetrafluoroethylene microporous membrane

technical field

The invention belongs to the field of proton exchange membrane materials for fuel cells, and in particular relates to a plasma modification method for polytetrafluoroethylene microporous membranes.

Background technique

Polytetrafluoroethylene (PTFE) is polymerized from tetrafluoroethylene and only contains C-C bonds and C-F chemical bonds. Both chemical bonds contain very high chemical bond energy, so PTFE is very stable in chemical properties and can be used as an anti-corrosion agent material , the degradation rate is very small, the service life is relatively long, and it is widely used in medical application materials, anion exchange membranes, sealing materials, filter materials and other fields.

Polytetrafluoroethylene microporous membrane has strong hydrophobicity, low surface energy, weak adhesion and wettability, which limit its application, so it needs to be modified by hydrophilicity. 【Materials Research Bulletin,2009,44(6):1437-1440】CeO ₂ /PTFE composite membrane is hydrothermally synthesized by loading CeO ₂ on the PTFE microporous membrane. The water contact angle can only reach 80°, and the effect of modification is not ideal enough. [Energy Procedia, 2011, 9:539-544] Using tetrabutyl titanate as raw material, TiO ₂ is loaded on PTFE microporous membrane by hydrothermal synthesis method to form TiO ₂ /PTFE composite microporous membrane. The synthesis time of this method is Longer, the process is more cumbersome, the water contact angle can only reach 70°, and the mechanical strength of the microporous membrane is reduced. 【Vacuum,2012,86(6):643-647】The PTFE membrane is treated with argon plasma alone, the contact angle of the treated membrane is 60°, and the damage to the microporous membrane is relatively large, and the mechanical strength is reduced. 【Applied Surface Science,2008,254(6):1614-1621】The contact angle of the modified PTFE membrane was 55° after nitrogen plasma treatment, and the mechanical strength of the microporous membrane decreased slightly.

Contents of the invention

In view of the existing hydrophilic modification method of polytetrafluoroethylene microporous membrane, the modification effect is not good, and the mechanical strength of the modified microporous membrane is reduced. The present invention provides a polytetrafluoroethylene microporous The plasma modification method of the membrane uses the low-temperature plasma treatment method to modify the surface of the PTFE microporous membrane. By controlling the process parameters of the low-temperature plasma treatment, including the type of low-temperature plasma gas, treatment distance, radio frequency power, treatment time and gas Throughput, improve the hydrophilicity of PTFE microporous membrane, modify the original highly hydrophobic PTFE microporous membrane into a more hydrophilic PTFE microporous membrane, and reduce the water contact angle from about 130° to about 40° , while maintaining the mechanical strength of the PTFE microporous membrane.

Technical scheme of the present invention is as follows:

A method for plasma modification of a polytetrafluoroethylene microporous membrane, the specific steps are as follows:

Step 1, pretreatment of PTFE microporous membrane: soak PTFE microporous membrane in acetone solution for 12-24 hours, then soak in 80%-98% ethanol solution for 3-12 hours, after soaking in ethanol solution several times to remove acetone, Wash with deionized water to remove ethanol, and finally dry at 30-70°C for 10-24 hours to obtain a cleaned PTFE microporous membrane;

Step 2, plasma treatment: place the cleaned PTFE microporous membrane in the plasma high-vacuum preparation chamber, after vacuuming, feed CH ₄ and N ₂ , and control the volume ratio of CH ₄ and N ₂ to 3:1~ 1:3, the total gas flow rate is 10cm ³ /s-50cm ³ /s, the power is 20w-100w, the treatment distance is 1cm-100cm, the treatment time is 20s-100s, and finally the modified PTFE microporous membrane is obtained.

Preferably, in step 2, the volume ratio of CH ₄ and N ₂ is 2:1˜1:2, more preferably 1:1.

Preferably, in step 2, the total flow rate of the gas is 20cm ³ /s-40cm ³ /s.

Preferably, in step 2, the power is 40w-80w.

Preferably, in step 2, the treatment distance is 20cm-80cm, more preferably 40cm-60cm.

Preferably, in step 2, the processing time is 40s-80s.

Compared with the prior art, the present invention has the following significant advantages: the present invention uses methane and nitrogen mixed gas plasma treatment method to modify the PTFE microporous membrane, after modification, the contact angle can be reduced to 40°, significantly improving the The hydrophilicity of the PTFE microporous membrane maintains the excellent mechanical properties of the PTFE microporous membrane. The method of the invention has short period and low cost, and can be used for commercial production.

Description of drawings

Fig. 1 is the contact angle diagram of untreated PTFE microporous membrane (a) and plasma treated PTFE microporous membrane (b).

Fig. 2 is a relation diagram of plasma power and contact angle of PTFE microporous membrane.

Fig. 3 is a graph showing the relationship between the plasma treatment time and the contact angle of the PTFE microporous membrane.

Fig. 4 is a graph showing the relationship between the ratio of plasma gas inlet and the contact angle of PTFE microporous membrane.

Fig. 5 is a graph showing the relationship between the gas flow rate of the plasma treatment inlet and the contact angle of the PTFE microporous membrane.

Fig. 6 is a graph showing the relationship between the plasma treatment distance and the contact angle of the PTFE microporous membrane.

Fig. 7 is a graph showing the results of the tensile strength test of the PTFE microporous membrane after plasma treatment.

detailed description

The present invention will be described in further detail below in conjunction with the embodiments and accompanying drawings.

Example 1

Pretreatment of PTFE microporous membrane:

Flatten the PTFE microporous membrane with two A4 papers, place it under a flat paper cutter, cut into several 5×5cm PTFE microporous membranes, immerse the cut PTFE microporous membranes in acetone solution, Soak in a fume hood for 12-24 hours, then soak in 80%-98% ethanol solution for 3-12 hours, replace the ethanol solution several times, remove acetone, then wash with a large amount of ionized water to remove ethanol, and finally put it in In a vacuum drying oven, dry at 30-70°C for 10-24 hours, cool the dried PTFE microporous membrane to room temperature, and then fix the microporous membrane on a glass plate for the next step of plasma modification.

Example 2

The pretreatment method of PTFE microporous membrane is as embodiment 1.

Plasma treatment:

First place the pretreated PTFE microporous membrane in the plasma high-vacuum preparation chamber, under the mixed gas of N ₂ +CH ₄ , adjust the plasma treatment distance to 40cm, select the treatment time to be 100s, and select the gas flow rate to be 20cm ³ /s. The gas ratio is selected as 1:1, that is, the gas flow rate of both methane and nitrogen is 10cm ³ /s, and the plasma power is controlled, and the power is respectively selected as 20w, 40w, 60w, 80w, and 100w.

The plasma-treated PTFE microporous membrane was measured with a JY-82 contact angle measuring instrument (Chengde Testing Machine Factory) respectively, and the contact angle of water was measured at 6 different positions respectively, and finally the average value was taken. The relationship between contact angle and plasma treatment power is shown in Fig. 2 . It can be seen from Figure 2 that the contact angle is between 40° and 60° at 20w to 100w. From the plasma treatment power of 20w to 40w, the contact angle gradually decreases, and at 40w, the contact angle reaches the minimum, and the contact angle reaches 42.84°, and the contact angle begins to gradually increase from 40w to 100w.

Example 3

The pretreatment method of PTFE microporous membrane is as embodiment 1.

Plasma treatment:

Put the pretreated PTFE microporous membrane in the plasma high-vacuum preparation chamber, under the mixed gas of N ₂ +CH ₄ , adjust the plasma treatment distance to 40cm, select the gas flow rate to be 30cm ³ /s, and select the gas inlet ratio to be 1:1 , that is, the gas flow rates of methane and nitrogen are both 10cm ³ /s, the power of plasma treatment is 40w, and the plasma treatment time is controlled, and the time is 20s, 40s, 60s, 80s, 100s respectively.

Fig. 1 is the contact angle diagram of untreated PTFE microporous membrane (a) and plasma treated PTFE microporous membrane (b). The relationship between contact angle and plasma treatment time is shown in Fig. 3. It can be seen from Figure 1 that the contact angle of PTFE film before plasma treatment is 130°, and the contact angle after final treatment reaches 40°. It can be seen from Figure 3 that before 20s, as the processing time increases, the contact angle decreases rapidly first, and reaches the minimum at 20s, and the contact angle is 41.82°. From 20s to 40s, it gradually increases, and after 40s, it tends to be stable.

Example 4

The pretreatment method of PTFE microporous membrane is as embodiment 1.

Plasma treatment:

Put the pretreated PTFE microporous membrane in the plasma high-vacuum preparation chamber, under the mixed gas of N ₂ +CH ₄ , adjust the plasma treatment distance to 40cm, select the gas flow rate to 30cm ³ /s, process power 40w, and process time 20s , to control the intake ratio, the intake ratios of methane and nitrogen are 3:1, 2:1, 1:1, 1:2, 1:3 respectively, that is, the intake volumes of methane and nitrogen are 22.5cm ³ /s and 7.5cm ³ /s, 20cm ³ /s and 10cm ³ /s, 15cm ³ /s and 15cm ³ /s, 10cm ³ /s and 20cm ³ /s, 7.5cm ³ /s and 22.5cm ³ /s.

The relationship between contact angle and intake ratio is shown in Fig. 4. It can be seen from Figure 4 that the contact angle is a process of first decreasing and then increasing. When the gas ratio is 1:1, the contact angle reaches the minimum.

Example 5

The pretreatment method of PTFE microporous membrane is as embodiment 1.

Plasma treatment:

Put the pretreated PTFE microporous membrane in the plasma high-vacuum preparation chamber, under the N ₂ +CH ₄ mixed gas, adjust the plasma treatment distance to 40cm, the gas inlet ratio to 1:1, and the plasma treatment time to 20s. The plasma processing power is 40w, and the gas flow is controlled. The total gas flow is 10cm ³ /s, 20cm ³ /s, 30cm ³ /s, 40cm ³ /s, 50cm ³ /s respectively.

The relationship between the contact angle and the total gas flow is shown in Figure 5. It can be seen from Figure 5 that when the gas flow rate of the plasma changes, under certain conditions, the contact angle gradually decreases with the increase of the gas flow rate, but when the gas flow rate is 20cm ³ /s, the contact angle reaches a minimum of 40.83 °, then the contact angle began to increase instead.

Example 6

The pretreatment method of PTFE microporous membrane is as embodiment 1.

Plasma treatment:

Put the pretreated PTFE microporous membrane in the plasma high-vacuum preparation chamber, under the mixed gas of N ₂ +CH ₄ , adjust the intake ratio to 1:1, the plasma treatment time is 20s, and the plasma treatment power is 40w , the plasma treatment gas flow rate is 20cm ³ /s, and the plasma treatment distance is controlled. The plasma treatment distances are 1cm, 20cm, 40cm, 60cm, 80cm, and 100cm.

The relationship between contact angle and plasma treatment distance is shown in Fig. 6. It can be seen from Figure 6 that the contact angle shows a trend of first increasing and then decreasing at the plasma treatment distance from 1cm to 40cm, the contact angle gradually increases from the plasma treatment distance of 40cm to 100cm, and the contact angle reaches the minimum at 40cm.

Example 7

The pretreatment method of PTFE microporous membrane is as embodiment 1.

Plasma treatment:

Put the pretreated PTFE microporous membrane in the plasma high-vacuum preparation chamber, under the mixed gas of N ₂ +CH ₄ , the processing power is 40w, the gas ratio is 1:1, the gas flow rate is 20cm ³ /s, and the plasma processing distance Under the condition of 40cm, control the plasma treatment time, 20s, 40s, 60s, 80s, 100s for plasma treatment. With the treated PTFE microporous membrane, get 2cm * 5cm strip microporous membrane, and adopt the tensile strength instrument (tensile strength tester of Shenzhen Xinsansi Material Testing Co., Ltd.) to carry out tensile strength test. The relationship between tensile strength and plasma treatment time is shown in Figure 7. As can be seen from Figure 7, after the plasma treatment, the tensile strength of the PTFE microporous membrane remains unchanged, indicating that the modification method of the present invention has no effect on the mechanical properties of the PTFE microporous membrane.

Claims (8)

1. the Plasma modification method of a microporous teflon membran, it is characterised in that specifically comprise the following steps that

Step 1, the pretreatment of microporous teflon membran: microporous teflon membran is soaked in acetone soln 12～24h, then in the ethanol solution of 80%-98% soak 3～12h, ethanol solution repeatedly soak removing acetone after, go from Sub-water cleans and removes ethanol, is finally dried 10～24h at 30～70 DEG C, obtains the microporous teflon membran cleaned up；

Step 2, Cement Composite Treated by Plasma: the microporous teflon membran cleaned up is placed in plasma fine vacuum and prepares In room, after evacuation, it is passed through CH₄And N₂, control CH₄And N₂Volume ratio be 3:1～1:3, the total flow of gas For 10cm³/ s～50cm³/ s, power is 20w～100w, and process distance is 1cm～100cm, and the process time is 20s～100s, Finally give modified microporous teflon membran.

The Plasma modification method of a kind of microporous teflon membran the most according to claim 1, its feature exists In, in step 2, described CH₄And N₂Volume ratio be 2:1～1:2.

The Plasma modification method of a kind of microporous teflon membran the most according to claim 1, its feature exists In, in step 2, described CH₄And N₂Volume ratio be 1:1.

The Plasma modification method of a kind of microporous teflon membran the most according to claim 1, its feature exists In, in step 2, the total flow of described gas is 20cm³/ s～40cm³/s。

The Plasma modification method of a kind of microporous teflon membran the most according to claim 1, its feature exists In, in step 2, described power is 40w～80w.

The Plasma modification method of a kind of microporous teflon membran the most according to claim 1, its feature exists In, in step 2, described process distance is 20cm～80cm.

The Plasma modification method of a kind of microporous teflon membran the most according to claim 1, its feature exists In, in step 2, described process distance is 40cm～60cm.

The Plasma modification method of a kind of microporous teflon membran the most according to claim 1, its feature exists In, in step 2, the described process time is 40s～80s.