| At present,PTFE dust filter bags are made of PTFE-coated needlepunched felt by sewing,and then the sewing thread holes are sealed and sealed,which requires many production processes and high costs.In order to enable one-time bonding in the production process,this paper uses the similar characteristics of PVDF molecular structure to PTFE,and prepares PVDF/PMMA hot melt adhesive by melt blending processing method.Improve and improve,as follows:(1)Firstly,the ratio of PVDF and PMMA components in PVDF/PMMA hot melt adhesive was explored,and the bonding performance,processing performance and heat resistance of PVDF/PMMA hot melt adhesive under different ratios were studied.When PVDF/PMMA is 75/25,the melt flow rate is 8.45 g/10 min,the Vicat softening temperature is 125 ℃,and the processing performance is good.the peel strength with PTFE dust filter cloth is greater than the tensile strength of PTFE fiber(filter The cloth fiber is broken,which meets the requirements of use),and the bonding performance is good.the initial decomposition temperature is also changed from 291 ℃ of PMMA to the overall initial decomposition temperature of PVDF/PMMA hot melt adhesive 326 ℃,10% PPS group is added to it.After the separation,with the increase of the content of PPS components,the crystallinity decreased from26.5% to 23.4%,and the melting temperature decreased from 172.74 ℃ to171.75 ℃,with little change,although the melt flow rate decreased slightly,the Vicat softening temperature decreased from 125 ℃ to 156 ℃.at 120 ℃,the peel strength of PVDF/PMMA hot melt adhesive is only 30.73 N/15 mm,while the peel strength of PVDF/PMMA/PPS hot melt adhesive is still greater than the tensile strength of PTFE fiber cloth It can still meet the requirements of use and meet the requirements of bonding performance at high temperature.because the decomposition temperature of PMMA is close to the processing temperature of PPS,the difficulty of welding processing increases.the rheology of PVDF/PMMA/PPS hot melt adhesives with different PPS contents is carried out.During the performance test,the PPS content was 10%,and the storage modulus G` changed from an obvious storage platform,indicating that at low frequencies,the viscosity began to transform into elasticity,and the phenomenon of shear thinning was obvious.Finally,it was found by scanning electron microscopy that PVDF The /PMMA/PPS hot melt adhesive penetrates well into the PTFE fiber cloth and forms a mechanical riveting effect.(2)The PVDF/PMMA/PA6 hot melt adhesives were studied on the bonding properties,processing properties,heat resistance properties and crystallization properties.On the basis of the previous chapter,continue to choose the ratio of PVDF/PMMA as 75/25,and select PA6 which has been processed in a wider temperature range as the third component,and blend with PVDF/PMMA to prepare PVDF/PMMA/PA6 Hot melt glue.With the addition of PA6 component,the melt flow rate decreased.At 0%～5% and15%～20%,the melt flow rate changed greatly,from 8.45 g/10 min to 6.72g/10 min and 6.06 g/10 min,respectively.g/10 min decreased to 5.24 g/10 min.when the addition amount of PA6 was 15%,the Vicat softening temperature increased from 125 ℃ to 156 ℃,but with the increase of PA6 content,the Vicat softening temperature increased slowly,and the melt flow rate decreased significantly.In the bonding test,when the PA6 content is 10%and 15%,the bonding effect meets the requirements at low temperature,but at150 °C,the PVDF/PMMA/PA6 hot melt adhesive with a PA6 content of 15%The peel strength remained at 40.76 N/15 mm.When the PA6 content is less than 10%,in the DSC crystallization curve,the crystallization peak is not obvious,and the melting enthalpy is small,only 6.7J·g-1.When the PA6 content increased from 0% to 5%,the crystallinity of PVDF in PVDF/PMMA hot melt adhesive increased from 26.5% to 47.7%.However,with the increase of PA6 content,the increase of PVDF crystallinity is very small,only1.2%.The melting temperature and melting enthalpy change very little.In the thermogravimetric analysis test,the PA6 component here increases the initial decomposition temperature of PVDF/PMMA hot melt adhesive from 320 ℃to 340 ℃.Select the best PA6 addition content and conduct rheological performance test.It can be seen that when adding 15% PA6,the storage modulus of PVDF/PMMA/PA6 hot melt adhesive increases the fastest,and the loss modulus rises less than the energy storage.modulus,and the complex viscosity is high,and it has obvious shear thinning phenomenon.the aging resistance test of PVDF/PMMA/PA6 hot melt adhesive is carried out,and it is found that due to the high water absorption rate of PA6,the peel strength is reduced on the 15 th day.It drops to 40.27 N/15 mm,and the water absorption rate is as high as 0.61%,which cannot be used for a long time in a humid environment.(3)The prepared PVDF/PMMA/PA6 hot melt adhesive is modified to reduce water absorption and improve aging resistance.Three different sizes of MMT powders of 500 mesh,1500 mesh and 3000 mesh were selected,modified with silane coupling agent KH-550,and then blended with PA6.comparing the contact angles of MMT powders of different sizes before and after modification,Through Fourier transform infrared test and XRD diffraction test,it is found that the MMT-1500 powder has the best modification effect,and the silane coupling agent is successfully attached to the surface of the MMT powder.After modification,the interlayer spacing of MMT powder was 1.27 nm and expanded by 0.04 nm.Then,the modified PA6 was blended with PVDF/PMMA.Through the melt flow rate test,bonding performance test and water absorption test analysis,it was found that in the PVDF/PMMA/modified PA6 hot melt adhesive,the optimal content of PA6 was still 15%.On the basis that the bonding performance meets the requirements of use,the water absorption rate drops from 0.71% to 0.53%.the aging resistance test analysis shows that the peel strength drops to 40.45 N/15 mm on the 25 th day,and the water absorption rate is 0.62%.Compared with the unmodified PA6,the use time is extended by 10 days,and the water absorption rate is reduced.Finally,the modified MMT powder and the hot melt adhesive bonded samples were analyzed by scanning electron microscope.(4)Under the hot-melt adhesive of PVDF/PMMA system in the full text,the bonding mechanism of PVDF/PMMA system hot-melt adhesive is discussed for PVDF/PMMA hot-melt adhesive with different third components.Two groups of PVDF/PMMA/PPS hot melt adhesives,PVDF/PMMA/PA6 hot melt adhesives and PVDF/PMMA/modified PA6 hot melt adhesives with different melt flow rates were selected for comparison.The experimental results show that the PVDF/PMMA hot melt adhesives that meet the application requirements have good processing fluidity,and the melt flow rate is 5.5 g/10 min.At the same time,three groups of PVDF/PMMA hot melt adhesive application samples with different welding processing temperatures were compared to compare the welding temperature and peel strength.The peel strength of the PMMA system hot melt adhesive meets the requirements for use.And in the micro-morphology test,it can be seen that the PVDF/PMMA hot melt adhesive test sample with high melt flow rate is significantly better than the PVDF/PMMA hot melt adhesive test with low melt flow rate for the micropore penetration of PTFE fiber cloth.samples,and an effective mechanical riveting structure was formed in the PTFE fiber cloth,which improved the peel strength of the hot melt adhesive. |
PDF Full Text Request