attenuating pp/pet bicomponent melt blown microfibers. - pet fiber
Introduction: Fusion spray is one of the most popular processes for manufacturing ultra-ultra
Fine fibers on a kilogramme or sub
It has found applications in more and more fields such as filtration, absorption, hygiene and clothing.
Researchers and engineers around the world have made many significant efforts to better understand the technology and improve the equipment.
Wadsworth and maschevich (1)
It is reported that the polymerization flux is 0.
2g/hole/min of PP, fiber diameter significantly smaller than low airflow rate was observed at high airflow rate. Haynes (2)
The correlation between the average pp fiber diameter and jet momentum is shown, I . E. e.
The larger jet outlet momentum will result in a smaller fiber diameter. Bresee (3)andHaynes (2)
It shows that the ata distance with the fastest attenuation of PP wire is 5. 08 to 7.
62 cm from the tip of the mold, after which there was no significant change in fiber diameter.
Uyttendaele and Shen Dawei (4)
One has been developed using PP and one-
By following previous studies of conventional melting rotation, holes, concentric molds.
Miriam and Haines (5)
PP melt spray modeling based on air hitting thin wire at 30 [angle] was also carried outdegrees]
From both sides of thespinneret nozzle.
Bico MB non-woven fabric with sideby-side (S/S)cross-
Cross-section fiber geometry has attracted the attention of industry and academia.
S/S bico fiber provides the possibility to combine the advantages of both polymers to produce unique fiber and network properties, for example, if the two polymers provide different properties under heatAs in a mono-
Assembly MB process, by manipulating processing conditions such as melting/mold temperature, throughput, mold geometry, airflow rate and temperature, mold-to-collector-distance (DCD)
And collector speed.
However, due to the difference between the two components, it becomes more complicated to process the two polymers together to produce S/S bico fiber MBfabricg.
Flow properties, such as melt viscosity (
Tensile and shear viscosity)
, Thermal properties, melting density and crystal rate.
With the growing interest and demand in the industry.
Bico MB fabric shows great potential as a unique product.
In order to produce a better bicoMB net, it is important to study the attenuation of hot wire in the process of hot wire.
Experimental polymer material PP particles provided by ExxonMobil Chemical company with an average size of 3--
5mm in diameter, is specially designed for the spinning process.
Nominal melt flow rate (MFR)
It's 35g/10 min at230 [degrees]C.
Fiber grade PET (IV = 0. 645 [+ or -]0. 017)
Crystal chip provided by Wellman company
In 120 [dry]degrees]
C. place 4 hours in Conair dryer before extrusion.
The research on processing and sample preparation was conducted 61 cm (24-inch)Reicofil [R]
MBpilot production line installed in textile and non-woven Development Center (TANDEC)
University of Knoxville, Tennessee.
MBpilot wire schematic diagram with dual-element processing capability can be found in reference (6).
The MB mold is a single row of passes that includes 60 ° [degrees]
The density of the line hole is 25 holes/inch, and the average hole diameter is 0.
38mm, this is a typical "Exxon design" MB die (7).
The mold geometry is configured as air gap 0.
The retrogression of 8mm and 1. 0 mm.
Processing conditions with air temperature are listed in Table 1, including polymer throughput, polymer mass ratio, air flow, mod and mold/air temperature (Ta)
Mold temperature (Td)fixed at 599[degrees]F(315[degrees]C).
The fibers are collected along MBspin in different locations-
Line with specially designed equipment with 51-cm rigid arm.
The instrument adopts a drive mechanism to ensure accurate position reading along the direction of the spin
Speed of line and arm movement.
Microscope slides (2. 5 cm X 7. 6 cm)
Securely connect to the far end of the arm at the appropriate angle to which the air jet blows. Thefiber-
In this work, the collection device is set in a fixed position.
Therefore, the fiber is collected in the same position relative to the MB mold. Three fiber-
Make the collected slides for each position along the direction of rotation
Correct Line and protection.
These high-speed production samples are used to determine the average number of fibers per inch thickness, which are further used to calculate the average fiber speed (6).
Another set of samples was prepared using the same technique, but the arm movement speed was relatively low for determining the average fiber diameter.
We assume that the sampling process has no significant effect on the fiber diameter.
Determination of fiber diameter and fiber diameter distribution fiber diameter using Olympus Optical microscope COP)
And image analysis software (NIH 1.
62, Harvest Company).
A camera was installed on the three-eye microscope.
The sample image is displayed on the monitor screen, analyzed through the software and saved to the file.
Before the measurement, the instrument was calibrated with an astandard millimetre.
It is reported that there are an average of 150 fiber diameter readings per designated position on MBspinline.
The fiber diameter distribution profile is constructed by drawing the frequency of the fiber diameter according to the corresponding classification Group of the fiber size.
Results and discussion the fiber diameter distribution is determined by measuring the fiber collected at different distances from the MB mold on the rotation line.
Figure 1 compares 100% PP, 100% PETmono-
Component MB fiber and PP/PET bico MB fiber. Both mono-
The double fiber diameter decreases sharply when it is 5 kilometers away from the mold.
The silk of PP is attenuated faster than the PET silk, while the bico silk is attenuated at a medium rate between PP and PET.
After the initial 5 centimeters, the PP filament continuously reduces the size at a slower speed until the freezing point, obviously 10 ~ 13 cm.
Starting from this point, the reduction in fiber diameter at a larger distance is minimal.
The average diameter of PET filaments decreased continuously to 6.
3 cm from the mold, then the fiber diameter has been increased to about 20.
3 cm from death.
This is an interesting result for the fused PET microfibers.
Because there is no drag device that can take up high-speed filament, mb pet fiber is likely to shrink within this rotation range when the air resistance during processing becomes very weak.
Jet temperature dropped from 315 [observed]degrees]
At the death exit to around 93. 3[degrees]
C 5 cm from the mold (6).
This produces a relatively rapid quenching effect on PET filaments, resulting in a nearly low rate of crystal from 5% to 15% (6, 8).
So average down
Line shrinkage measurement of mb pet net up to 30-55% (9).
The 50% PP/50% PET bico MB fiber has a similar attenuation curve.
After a rapid decay, the average diameter of the filament remains slowly decreasing.
However, PETcomponent hinders this level compared to the 100% PP wire.
On the other hand, PPcomponent helps slow down the solidification of PET parts.
Therefore, the freezing point of the bico MB fiber moves further downstream of the spin line.
The attenuation curve of 50% PP/50% PETfilaments is closer to 100% PET, which indicates that PET is the control part of the final diameter of the two-component fiber.
Image in figure
Figure 2 illustrates the attenuation and entanglement of 75% PP/25% PET two-component fibers.
At a distance near the MB chip, the fibers are arranged almost parallel to the direction of the air flow, and the fiber number is arranged at the intersection at a specific length
The direction of the airflow is much smaller.
With the increase of distance, the orientation of the fiber begins to be disturbed and winding occurs.
There is no doubt that these fibers are entangled to a greater extent and form a fiber bundle or ropesas when they fly a greater distance from the mold.
This result is consistent with previous observations (10).
Within a distance of about 5 cm m from the MB chip, the airflow turbulence becomes significant, and the silk wire is widely attenuated from several hundred micrometers to several hundred micrometers.
Although the filament accelerates rapidly near the mold, the filament speed decreases after reaching the maximum value (6)
, Which causes the fiber to clog at a long distance from the mold.
Air turbulence and fiber blockage during MB process are considered to be two main causes of fiber winding and bunching.
Although many related papers usually report the final average fiber diameter (1-5)
The size distribution of the optical fiber during attenuation is usually ignored.
In this work, monitoring the distribution of fibers along the spin line reveals important information about the effects of fiber attenuation, structural development and processing conditions.
Figure 3 shows the diameter distribution of PP fibers at different locations. At 2.
5 cm from the die head, the fiber diameter distribution is very wide, covering the fiber size from 1 [mu]m to 20 [mu]
No obvious advantage.
As distance-from-the-die (DFD)
With the increase of fiber diameter, the main groups appear within the smaller fiber diameter range and the distribution is narrower and narrower. At a DFD of 16.
5 cm, 92% of the fiber population is 0. 5 [mu]m to 4[mu]m; at 29.
2 cm, the number increased to 98%.
Therefore, the attenuation of the PP filament has always occurred in the journey of the collector and has become more and more uniform in the fiber size.
Figure 4 shows the PP fiber diameter distribution at different positions along the spin line at higher airflow rates, showing the same trend of fiber attenuation development and changes in fiber diameter distribution3.
Difference of graph3 and Fig.
4 is mainly located near the mold.
At a higher airflow rate, the fiber distribution is relatively narrow, and the degree of filament decay is higher.
It is reasonable to consider the increased air resistance applied to the wire by considering the wire mild not far from the mold.
With the increase of DFD to 12 cm, the difference between low flow rate and high flow rate cases obviously disappeared.
This observation shows that the effect of airflow rate on fiber attenuation is mainly manifested in the narrow range close to the mold.
Under similar processing conditions, PET fibers exhibit a wide distribution and two major groups in different positions of thespinline, unless very close to the tip of the mold (DFD = 1. 27 cm)
As shown in the figure. 5.
At more than 6 points, the distribution of PET fibers seems to be wider. 35 cm.
Combining these results with the pet fiber attenuation curve shown in the graph
1. it can be concluded that the pet filament does not decay to a constant extent, and the fiber size distribution will be generated even in the same filament.
The part with a larger attenuation in continuous fibers is likely to have a greater degree of crystalline than the part with a smaller attenuation.
Therefore, when they fly over a specific point, the smaller part of the attenuation may shrink to a greater extent (when DFD = 6.
35 cm, in this case)
Resulting in a wider distribution of optical fibers.
Figure 6 shows the fiber diameter distribution of 50% PP/50% PETbico filaments at different positions on the rotation line.
The experiment was carried out under the following conditions: the throughput was 15 kg/h and the mold temperature and air temperature were set to 315 [degrees]
C. air flow at 9: 00. 91 SCMM (
Standard cubic meters per minute)
DCD is 48. 3cm.
Similarly, with the increase of DFD, the distribution of fiber diameter becomes narrower and narrower, with the main population in the smaller fiber size area.
As shown in the figure, it seems to become narrower at higher airflow rates. 7.
This difference occurs at a large distance from the mold, such as 20. 32 cm.
In the range close to the MB chip, the fiber diameter distribution has a similar width.
Comparing the fiber diameter distribution curve of the double wire with the fiber diameter distribution curve of 100% PP and 100% PET, it was found that the distribution profile of the bico wire is wider than that of the PP wire, which is very similar to PET.
Another important observation is that the profile of the fiber distribution of the double wires also shows a double
Peak, although one of these two peaks becomes stronger than the other when the DFD is close to 20. 32 cm.
As discussed in the previous section, PET components have unique properties such as high glass transition and melting temperatures.
It is clear that PET controls the outline of the fiber diameter distribution of the bico filament and has an obstacle to the attenuation of the filament, which causes the fiber diameter distribution to be significantly wide. The double-
The peak in the fiber diameter distribution curve of PP/PET and 100% PET may be related to the air resistance on the filament and the Tensile viscosity curve of the spinning line, but at the time of this study, the exact cause of this phenomenon is not yet clear.
Conclusion two singleand bi-
In 5 cm of the time before the mold, the component filaments decay from a few hundred micrometers to a few micrometers, after which the filaments slowly decay far from the mold.
The diameter of the Bico MB filament is between 100% PP and PET filament.
With the increase of PET percentage, the final fiber diameter is closer to 100% PET filament.
The PETcomponent in the Bico filament controls the final fiber diameter.
In a short area close to the mold, the filament is aligned with the direction of the airflow.
Start winding at about 2.
5 cm away from the mold, the direction is more and more random as the distance increasesfrom-
People on a diet
Although the filaments significantly decay in the initial 5 or 7 cm, it is found in these fibers that the fiber diameter distribution is wide and that they become narrower as the filaments move further from the mold.
The diameter of PP fibers near the mold is more uniform and the airflow rate is higher.
In a position relatively far away from the mold, the effect of the airflow rate on the fiber size distribution is not significant.
The fiber diameter distribution of Bico silk is wider than that of a single PP.
The higher the airflow rate, the narrower the fiber size distribution of the bico wire. [
Figure 1 slightly][
Figure 3 slightly][
Figure 4 slightly][
Figure 5 Slightly][
Figure 6 slightly][
Figure 7 Slightly]
Thanks to the author for the financial support of the textile and non-woven fabric development center at the University of Tennessee in Knoxville for this study.
They thanked Exxon Mo chemical for donating polypropylene resin and sincerely thanked Dr. Exxon Mo chemical.
David Ghana, director of TANDEC, encouraged him. REFERENCES (1. )L. C.
Wadsworth and. O.
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Zhao, "two Poly polypropylene/poly (
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Buntin, "Fusion mold for the production of cloth mats", United States of AmericaS.
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Polymer International (in press). (9. )R. Zhao. D. Zhang. C. Sun, and L. C. Wadsworth.
Properties and properties of PET, PP/BES and PP/PET fused-sprayed micro-fiber non-woven fabrics prepared by hot-explosive method
10 th TANDEC conference
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Current Address: Biax fiber film, N992 quality doctorSuite B.
WI 54942 Greenville.