1. Polymer Nanofibers from Recycling of Waste Expanded Polystyrene
Research at The University Of Akron
C. Shin and G. G. Chase
ABSTRACT
This work is to investigate the production of polystyrene (PS) nanofibers from expanded polystyrene (EPS) and the coalescence separation of water droplets in a water-in-oil mixture using glass fiber media and glass fiber supplemented with electrospun PS nanofiber media from recycled EPS. The experimental results in this work show that around 700 nm polystyrene nanofibers were produced by electrospinning method and adding nanofibers to conventional micron sized fibrous filter media improves the separation efficiency of the filter media.
EXPERIMENT
Figure 1. Experimental apparatus of coalescence filtration
1. Oil Tank 2. Peristaltic pump 3. Mixing pipe 4. Hypodermic needle
5. Syringe pump 6. Filter Sample holder 7. Manometer 8. Valve
9. Settling tank 10. Reservoir tank S. Sampling points
ELECTROSPINNING .
Figure 2 shows a schematic diagram of the apparatus used in the electrospinning. The syringe is filled with polymer solution. The flow rate is controlled with a syringe pump (WPI, Model Sp101i). The needle with a 1.6 mm outside diameter, 1 mm inside diameter is connected to a power supply and charged to 15,000 volts (Gamma High Voltage Research, Model D-ES30PN/M692). The collecting surface is grounded to attract the charged fibers. A collecting surface is placed at a distance of about 20 cm from the tip of the needle of syringe pump. The needle is charged to volts to charge the polymer solution and the polymer nanofibers are produced. The EPS solution is prepared by dissolving 20 wt% waste EPS (from chemical packing) by mass in 80 wt% N,N-dimethylacetamide (DMAc).
DATA Table 1. Filter Media Data
RESULTS
Figure 3. Commercial glass fiber and eletrospun EPS polymer nanofibers.
Figure 4. Experimental results.
a. Particle size distribution b. Pressure drop vs. time
c. Area ratio of polymer nanofibers vs efficiency
INTRODUCTION
Various techniques are available for recycling the waste plastics such as chemical, thermal, and material recycles. EPS is the material commonly used for insulating and packing materials. Many industries use EPS because of excellent insulation, versatile for designs, dimensional stability, clean, and lower cost per unit. EPS is one of the most difficult to recycle because it contains so much air. The used EPS is generally disposed of in landfills. If these EPS are recycled as an alternative to land-filling, this would produce a decrease in the volume of EPS being land-filling.
Electrospinning produces nanofibers with high surface areas and long lengths with diameters in the range of nm. The electrospinning process is driven by the electrical forces on free charges on the surface or inside a polymeric liquid. When the free charges in the polymer solution, which are generally ions, move in response to the electric field, they quickly transfer a force to the polymer solution. When the electric field reaches a critical value at which the repulsive electric force overcomes the surface tension force, a charged jet of the solution is ejected from the tip of a cone protruding from a liquid drop of the polymer. Thus, continuous fibers are produced to form a non-woven fabric.
The coalescence filter is economical and effective for separation of secondary dispersions. There are three main steps of the coalescence process. First, the fibrous bed captures water droplets. Second, the collected water phase passes through the bed and the droplets coalesce on the fiber. Third, the enlarged droplets are released from a fiber surfaces and drain out of the medium.
Figure 2. Electrospinning process
Amounts of polymer nanofiber in filter (g)
0.0204
0.0415
0.0601
0.1224
Separation efficiency (E), %
67.5
72.3
79.0
85.4
88.1
CONCLUSIONS
In this work, we investigate EPS in an attempt to convert the EPS into PS nanofibers which is used for filtration materials. A blend of 0.5 g glass fiber and EPS polymer nanofibers showed improvement of separation efficiency. Added PS nanofiber filters had a better capture efficiency, but also had a higher-pressure drop. The increased surface area of the filter samples provides an improvement in the separation efficiency.
FUTURE WORK
Modeling of binary fibers filter for estimating coalescence efficiency.
Filter
Glass fiber (g)
Binder (g)
Nanofiber (g)
Total weight (g)
Filter A
0.500
0.325
0.000
0.825
Filter B
0.352
0.020
0.872
Filter C
0.370
0.042
0.911
Filter D
0.369
0.060
0.929
Filter E
0.122
0.992