The Study Of Damage On Glass Fiber Base Fabric Of High Temperature Resistant Filter Material Due To Needle Punched

Nowadays, the environment problem has caused global attention. Our country has issued a series of dust emission standards. In the meantime, the companies ask for longer life span of the filter material and higher filtering performance. The needle punched process used for high temperature filter material has unavoidable damage on glass fiber base fabric. Thus the strength of needle punched filter material decreases. The lifetime of filter material is shortened. The breakthrough point to this problem is to reducing the damage of glass fiber base fabric after needle punching. Based on such a background, this article puts forward that the study of damage on glass fiber base fabric used for high temperature filter material due to needle punching. The subject aims at reducing the damage on glass fiber base fabric to a lower point, increasing the strength of filter material after needle punched. So that the life span could be extended and the production cost could be lowered dramatically.This paper surveys the filter-bag's damage mechanism, inquires a large number of literatures, and does the following four aspects:firstly, it analyses the damage mechanisms of glass fiber and glass fiber base fabric due to needle punching and figures out that the damage on high temperature resistant filter materials is mainly caused by glass fiber base fabric's damage due to needle punching. Secondly, it analyses the property of glass fiber, glass fiber yarn and glass fiber base fabric. It also compares the physical properties of water-soluble PVA fiber with PPS fiber. Then it confirms that it is feasible to use water-soluble PVA fiber to replace PPS fiber. Because the glass fiber base fabric can be separated from filter material specimen. Thirdly, this paper determines to use the longitudinal strength loss rate, transverse strength loss rate and absolute strength loss rate to quantificationally represent glass fiber base fabric's damage degree after needle punching and uses the 3-D video microscope to qualitatively represent the breakage of glass fiber. It also introduces the glass fiber base fabric's strength test methods, evaluates their merits and demerits as well as their feasibility. Finally, it studies the relationships between glass fiber base fabric's damage degree with needle punching parameters, e.g. needling depth, needling density, stepping, the fiber orientation of surface web, the yarn diameter of glass fiber base fabric and hook orientation. It also analyses the change of glass fiber base fabric's strength loss rate due to different needle punching parameters.This paper obtains the following result from the above researches:(1) Glass fiber is a kind of high strength fiber with low extension. But it is easy to brittle. The glass fiber base fabric breaks instantaneously during the tensile test.(2) By comparing the break location, the strength and CV, it gets the relatively optimal method is using resin immersion. The longitudinal strength of glass fiber base fabric is 3188.90N with CV of 6.34%, and the transverse strength is 3070.33N with CV of 6.32%.(3) The damage of the glass fiber base fabric due to needle punching depends on the hook number used to cutting glass fiber. Besides, hook's movement and the needle tip's impact also have effect on glass fiber base fabric's damage.(4) With the increase of needle depth and web thickness, the glass fiber base fabric's damage increases. When the needle depth is more than 6.3 mm, there will be one more hook per 2.1 mm. The larger the needling density is, the greater the damage is. The damage of pre-needling is bigger than the main needling. The larger the stepping, the greater the damage is.(5) The surface web can protect the glass fiber base fabric. The fiber arrangement of the surface web has effect on glass fiber base fabric's damage after needle punching, and it arranges as following:fiber cross arrangement is better than horizontal arrangement, and horizontal arrangement is better than longitudinal arrangement.(6) The warp yarn diameter of 1# glass fiber base fabric is 46.97% of the 2# glass fiber base fabric. And the weft yarn diameter of 1# glass fiber base fabric is 45.46% of the 2# glass fiber base fabric. At the same needle punching parameter, the longitudinal strength loss rate of 1# glass fiber base fabric is 74.84% of the 2# glass fiber base fabric, and the transverse strength loss rate of 1# glass fiber base fabric is 74.84% of the 2# glass fiber base fabric when the base fabric is covered with surface web.(7) When the hook orientation is perpendicular to the web output direction, It defines the 0 as zero. Different hook orientation has different effect on glass fiber base fabric's damage after needle punching. The variation trend varies as following:LR(θ=45°)<LR(θ=-45°)<LR(θ=0°)<LR(θ=90°)<LR(θ=-90°). When theθis 45°, the absolute damage loss rate is lowest as 8.66%. At that time the longitudinal strength losses from 3188.90N to 2940.70N, while the transverse strength losses from 3070.33N to 2772.60N. When theθis 0°, the longitudinal strength loss rate is bigger than the transverse. While theθis±90°, the transverse strength loss rate is bigger than the longitudinal. If the needle punching parameters are same, along the output direction the damage of glass fiber base fabric is smaller than against the direction.