Melt Spinning of PET (Polyethylene terephthalate)

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General description     capabilities    uses
Input Data process data    air velocity    geometry   options
Calculated Results input data   rowwise spinline parameters
rowwise fiber properties spinline parameter profiles air temperature
air velocity   overall results
Graphical Results general display   first and last row comparison
comparisons of several runs
Summary summary of results from several runs
Correlations correlations for transport coefficients and properties

 This page describes results generated by the software. Additional details are available in the following paper :

 Simulation Software for the Multifilament Melt Spinning of PET
 Dr. V. M. Nadkarni & Dr. V. S. Patwardhan
 International Fiber Journal, 1999(December), 14(6), 64-69
 

General description

This software package simulates the melt spinning of PET (i.e. polyethylene terephthalate). The calculation procedure consists of integration of the continuity, heat balance and constitutive equations down the spinline, using a fourth order integration scheme. This procedure generates axial profiles of fiber temperature, fiber diameter, and the tensile force along the spinline. The variation of percent hollow (for hollow fibers) along the spinline is calculated by integrating an additional equation which involves a surface tension parameter. The fiber tension is calculated iteratively, starting  from an initial guess value which is determined by the software itself. The inlet quench air velocity at any position is calculated by interpolation using the specified quench air velocity profile. The calculation proceeds from row to row consecutively, starting from the first row. The chimney flow of air generated by the moving filaments is taken into account while calculating the quench air conditions after each row. This procedure gives the variation in the air velocity profile and temperature profile as the quench air crosses successive rows. At the end of the quench air screen, the chimney flow is assumed to entrain additional atmospheric air, at a flow rate specified by  the user. This total air flow is assumed to be cocurrent with the fibers and provides additional cooling up to the convergence point.

The filaments (which are not exactly vertical in position), tend to sag due to gravity. In addition to this, the flow of air in a direction perpendicular to the filaments causes them to bend in the  direction of air flow. The software calculates the total deflection of filaments due to both these factors.

The software has a convenient user interface for data input and for output of results. It displays results of calculations in several forms such as a results file, a graphical display, graphical comparisons of several runs and a quick summary  of results from several runs, as explained elsewhere.

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Capabilities

The software package can be used for the following operating condition ranges :
 
   Spinerette geometry    rectangular, concentric circular
   Spinerette type    solid circular, concentric hollow circular
   Quench air flow geometry    crossflow, radially outward flow
   Quench air velocity    constant, velocity profile
   Number of holes    equal or unequal in all rows
   Take-up speed    upto 3500 m/min
   Filament denier    upto 50 decitex
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Utility of the software

A large number of parameters affect the process of melt spinning. These include major ones such as denier, take-up speed, melt viscosity, melt temperature and the quench air conditions, and many others which include the physical properties of the PET, geometrical dimensions, air draught conditions, atmospheric temperature etc. A comprehensive list of these can be seen in the input data screens presented elsewhere. In view of this complexity, this simulation software package is an important tool which can be broadly used for the following :
  1. process optimization
  2. new product development
  3. sensitivity analysis
  4. troubleshooting
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Correlations

The software package uses several correlations for polymer properties, heat transfer, air drag, filament properties etc. It permits the user to change the parameter values in all these correlations so that they are applicable to the specific situation under consideration.

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Results file generated by the software

INPUT DATA : Spinerette cross section : Solid circular
                        Quench air flow : Crossflow

            1. Glass transition temperature . deg C       75.0
            2. Intrinsic viscosity .......... dl/gm        0.63
            3. Melt temperature ............. deg C      290.0
            4. Capillary radius ............. mm           0.175
            5. Capillary length ............. mm           0.7
            6. Spinerette plate thickness.... mm           4.8
            7. Entry hole radius............. mm           1.0
            8. No. of filaments per end .....             34.0
            9. Number of rows ...............             10.0
           10. Delayed quench zone .......... mm          19.0
           11. Quench screen length ......... m            1.2
           12. Spinning length .............. m            1.3
           13. Quench air temperature ....... deg C       18.0
           14. As-spun filament denier ...... denier       7.0
           15. Take-up speed ................ m/min     2800.0
           16. Air entrainment factor .......              5.0
           17. Atmospheric temperature ...... deg C       25.0
           18. Mult. fact. for heat tr. coeff              1.0
           19. Mult. fact. for air drag coeff              1.0
           20. Generate data files for graphs ?          yes
           21. Calculate spinline deflections ?          no

The air velocity is constant over the quench screen length.
                              Air velocity, in m/sec   =       0.6

                       Distance between rows  :     5.0   mm

                         ----------------------------------------------
 Air blowing width       Row    Air blowing    No. of   Av. Dist. bet.
 and no. of holes :      No.     width (mm)    holes     holes (mm)
                         ---   -------------   ------   ---------------
                           1         80.0        11         7.3
                           2         80.0        11         7.3
                           3         80.0        11         7.3
                           4         80.0        11         7.3
                           5         80.0        11         7.3
                           6         80.0        11         7.3
                           7         80.0        11         7.3
                           8         80.0        11         7.3
                           9         80.0        11         7.3
                          10         80.0        11         7.3
                         ----------------------------------------------
 

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ROWWISE SPINLINE PARAMETERS :

---------------------------------------------------------------------------
Row  Stress at  Stress at  Freeze    Tension     Max.     X max     Biref.
no.   spinert.  95% draw    point   at frz pt.  dv/dx
       N/m2       N/m2       cm    gm/filament    /s        cm       (-)
---  ---------  --------- --------- --------- --------- --------- ---------
  1   5.586E+02 3.019E+06 6.418E+01 2.394E-01 1.463E+02 4.017E+01 2.616E-03
  2   5.492E+02 3.028E+06 6.580E+01 2.405E-01 1.428E+02 4.141E+01 2.623E-03
  3   5.403E+02 3.041E+06 6.746E+01 2.415E-01 1.391E+02 4.268E+01 2.635E-03
  4   5.321E+02 3.053E+06 6.916E+01 2.424E-01 1.356E+02 4.402E+01 2.645E-03
  5   5.246E+02 3.065E+06 7.090E+01 2.432E-01 1.323E+02 4.542E+01 2.655E-03
  6   5.177E+02 3.074E+06 7.265E+01 2.442E-01 1.295E+02 4.688E+01 2.663E-03
  7   5.114E+02 3.086E+06 7.443E+01 2.451E-01 1.264E+02 4.837E+01 2.673E-03
  8   5.056E+02 3.096E+06 7.623E+01 2.458E-01 1.237E+02 4.991E+01 2.682E-03
  9   5.002E+02 3.107E+06 7.804E+01 2.464E-01 1.212E+02 5.149E+01 2.691E-03
 10   4.953E+02 3.116E+06 7.986E+01 2.472E-01 1.189E+02 5.312E+01 2.699E-03
---------------------------------------------------------------------------

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ROWWISE FIBER PROPERTIES (calculated) :

 -----------------------------
 Row    Tenacity     Per cent
 No.                elongation
 ---   ----------   ----------

   1    2.379E+00    1.878E+02
   2    2.381E+00    1.874E+02
   3    2.385E+00    1.868E+02
   4    2.388E+00    1.863E+02
   5    2.392E+00    1.858E+02
   6    2.394E+00    1.853E+02
   7    2.398E+00    1.848E+02
   8    2.401E+00    1.843E+02
   9    2.404E+00    1.839E+02
  10    2.406E+00    1.834E+02
 -----------------------------

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SPINLINE PARAMETER PROFILES :

--------------------------------------------------------------------------
dist. from      dia(mm)        temp(deg C)       tension(gm)      outlet
spinerette  first    last     first    last     first    last    air temp.
   cm.       row      row      row      row      row      row     (deg C)
----------  --------------   ---------------   ---------------   ---------
    0       0.35   - 0.35     290.0  - 290.0    0.0055 - 0.0049
   10       0.1535 - 0.1744   242.4  - 252.87   0.0059 - 0.0034     78.26
   20       0.0923 - 0.1199   202.88 - 219.62   0.0159 - 0.0072     59.29
   30       0.0571 - 0.0828   168.6  - 189.87   0.0443 - 0.0181     52.87
   40       0.0387 - 0.057    136.46 - 162.8    0.101  - 0.0432     48.27
   50       0.0309 - 0.0412   107.49 - 137.18   0.1678 - 0.0884     43.19
   60       0.028  - 0.033     83.45 - 113.41   0.2212 - 0.1467     37.77
   70       0.0274 - 0.0291    64.77 -  92.42   0.2558 - 0.2017     32.75
   80       0.0274 - 0.0274    50.89 -  74.77   0.285  - 0.2466     28.69
   90       0.0274 - 0.0274    40.83 -  60.58   0.3142 - 0.2757     25.62
  100       0.0274 - 0.0274    33.7  -  49.51   0.3433 - 0.3049     23.39
  110       0.0274 - 0.0274    28.72 -  41.06   0.3725 - 0.334      21.8
  120       0.0274 - 0.0274    25.28 -  34.72   0.4017 - 0.3632     20.68
  130       0.0274 - 0.0274    24.55 -  32.04   0.4309 - 0.3924     29.71
--------------------------------------------------------------------------

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AIR TEMPERATURE, DEG C (UPTO 100 CM. FROM SPINERETTE) AFTER EACH ROW :

 ---  --------------------------------------------------------------------
 Row                 Distance from the spinerette (cm.)
 no.    10     20     30     40     50     60     70     80     90    100
 ---  -----  -----  -----  -----  -----  -----  -----  -----  -----  -----
   1   23.0   21.8   21.3   20.8   20.3   19.7   19.2   18.9   18.6   18.4
   2   28.2   25.7   24.6   23.7   22.7   21.5   20.5   19.8   19.2   18.9
   3   33.6   29.6   27.9   26.7   25.1   23.4   21.9   20.7   19.9   19.3
   4   39.3   33.7   31.4   29.7   27.5   25.3   23.3   21.7   20.6   19.8
   5   45.2   37.8   34.8   32.7   30.1   27.3   24.8   22.8   21.4   20.3
   6   51.3   42.0   38.3   35.7   32.6   29.3   26.3   23.9   22.1   20.9
   7   57.7   46.2   41.9   38.8   35.2   31.3   27.8   25.0   23.0   21.5
   8   64.3   50.5   45.5   41.9   37.8   33.4   29.4   26.2   23.8   22.1
   9   71.2   54.9   49.2   45.1   40.5   35.6   31.1   27.4   24.7   22.7
  10   78.3   59.3   52.9   48.3   43.2   37.8   32.7   28.7   25.6   23.4
 ---  --------------------------------------------------------------------

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AIR VELOCITY, M/S (UPTO 100 CM. FROM SPINERETTE) AFTER EACH ROW :
 ---  --------------------------------------------------------------------
 Row                 Distance from the spinerette (cm.)
 no.    10     20     30     40     50     60     70     80     90    100
 ---  -----  -----  -----  -----  -----  -----  -----  -----  -----  -----
   1   0.57   0.59   0.59   0.6    0.61   0.61   0.61   0.61   0.61   0.61
   2   0.54   0.59   0.59   0.6    0.61   0.62   0.62   0.62   0.62   0.62
   3   0.51   0.59   0.58   0.6    0.62   0.63   0.64   0.63   0.63   0.63
   4   0.48   0.58   0.58   0.59   0.62   0.64   0.65   0.64   0.64   0.64
   5   0.45   0.58   0.57   0.59   0.62   0.65   0.66   0.66   0.65   0.65
   6   0.43   0.58   0.57   0.59   0.63   0.65   0.67   0.67   0.66   0.66
   7   0.4    0.57   0.56   0.59   0.63   0.66   0.68   0.68   0.67   0.67
   8   0.37   0.57   0.56   0.58   0.63   0.67   0.69   0.69   0.68   0.67
   9   0.34   0.57   0.55   0.58   0.63   0.68   0.7    0.7    0.69   0.68
  10   0.31   0.57   0.55   0.58   0.64   0.68   0.71   0.72   0.71   0.69
 ---  --------------------------------------------------------------------

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OVERALL RESULTS :

           Hydraulic diameter of spinerette, mm          0.35
           Capillary length / hydraulic diameter         2.0
           Velocity through spinerette, m/sec            0.3259
           Apparent shear rate in the capillary, /s     7.450E+03
           Throughput per hole, gm/min per hole         2.178E+00
           Total throughput, kg/hr per end              4.443E+00
           Total denier per end                         2.380E+02
           Pressure drop through spinerette, kg/cm2     5.178E+00
           Shear stress in the capillary, dynes/cm2     6.567E+05
           Spin stretch factor (based on velocity)      1.432E+02
           Freezeline location from spinerette, cm.    64.182 -  79.859
           Force at convergence point, gm per end       1.409E+01
           Tension at freezeline, gm                   0.2394 -  0.2472
                                  gm/denier            0.0342 -  0.0353
           Stress at freezeline, gm/sq. cm         40.587E+03 - 41.885E+03
           Birefringence                           2.6158E-03 - 2.6993E-03
           Fiber size convergence, per cent            0.0108 -  0.0278

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