1. What kind of sorbents are available?
1. CLAY GRANULES
- Absorbs less than 1 times its own weigh
2. VERMICULITE GRANULES
- Absorbs 4 to 5 times its own weight
- Too light if used loose (used mainly in SOCs)
- Retrieval is labor-intensive
- Can damage machines
- Is expensive as waste
3. ORGANIC GRANULES
- Plants / sawdust / paper / corn cob
- Absorbs up to 6 times its own weight
- Limited chemical resistance
- Retrieval is highly labor-intensive
- Absorbs 10 to 25 times its own weight
- Many specially made sizes and models
- Incinerable - only 0.02% ash - and energy value of 14 kwh/kg.
- Chemical resistant
- Storage life / does not rot or mildew
- Ability to float
- Cost effective
2. Why should I use meltblown polypropylene sorbents?
For many reasons:
- No dust formation
- Less bulky
- No risk of granules getting on to surfaces to be sprayed, in templates, molds or expensive pumps
- Easily incinerable
- Retrieval is quick and efficient
- Low weight and volume as waste
- Chemical resistance
- Total Economic Value!
3. How is meltblown polypropylene made?
The resin is fed into an extruder where it is heated and melted to the appropriate temperature and viscosity required for fiber formation.
The extruder feeds molten polymer through a distribution die which enforces the polymer through fine holes in a spinnerette which is attached to the discharge end of the distribution die.
As the resin strands emerge from the spinnerette, high velocity hot air is discharged along both sides of the spinnerette.
This stream of hot air attenuates the polymer strands into a blast of microfibers which are frozen by the surrounding ambient atmosphere before being propelled onto the web former.
4. Can a polypropylene sorbent sink?
NO! Only in rare cases a sorbent will float just beneath the water surface.
- Surfactants in the water
- Dispersants in the water
If surfactants and dispersants are presents in the water then the surface tension changes in the sorbent, resulting in the sorbent then absorbing water and other liquids. The surfactant will cling to the polypropylene fibers resulting in the changing of the fibers surface tension. For further explanations on surface tensions, see chapter "Why does a polypropylene sorbent float and repel water".
5. Why does polypropylene float and repel water?
Mainly because of three reasons:
1. Surface tension:
- polypropylene: 29 dynes / cm2
- water: 72 dynes / cm2
There are several scientific characteristics of meltblown polypropylene that cause it to repel water and float. First there is the surface energy of water (72 dynes/cm2) versus polypropylene (29 dynes/cm2). A dyne is a metric unit of force. This large difference is what causes polypropylene to be water repellent or hydrophobic. The surface energy of salt water is between 60-65 dynes/ cm2 and will make the meltblown polypropylene slightly less repellent.
- polypropylene: specific gravity of 0.9
- water: specific gravity of 1
- sea water: specific gravity of > 1
Then there is the specific gravity as defined as the density of polypropylene relative to the density of fresh water. The specific gravity of fresh water is 1.0 and the specific gravity of polypropylene is 0.9. This simply means that polypropylene is lighter than water and will float. Salt water's density is higher than the density of fresh water. In salt water the meltblown polypropylene will be even more buoyant.
3. The amount of air between the fibers:
The "pronounced buoyancy" of meltblown polypropylene is a result not only of the surface energy and the specific gravity but also of the air that is trapped between the fibers of the sorbent. The fiber packing is so dense that the surface energy of the sorbent will not allow water to replace the air that naturally exists between the fibers, thus the sorbent will not become water-logged. The net result is that an oil sorbent will float indefinitely.
The only thing that may cause polypropylene to float lower than the water line is the presence of a contaminant such as a surfactant or emulsifier in the water. Such contaminants might include soap, detergent, alcohol or chemical dispersant. The presence of these surfactant materials would cause the oil to be at least partially soluble in the surrounding water and would change the surface energy enough to allow water to penetrate between the fibers. The polypropylene will not sink (as to the bottom) but it can hold some water in the presence of the surfactants.
For the polypropylene to sink to the bottom, it would need to be weighted (sand, rock, debris, or heavier than water type liquid) to offset the buoyancy of polypropylene. In open water conditions, polypropylene will float indefinitely, even if fully saturated with oil.
6. What distinguishes a good sorbent?
Several things distinguish a good sorbent including:
- Absorption capacity
- Amount of lint
- User friendliness
- Consistent Quality
7. Why do sorbents have different colors?
Take Note: Sorbents do not alter the characteristics of the (chemical) liquid absorbed! For your safety the SPC chemical sorbents are colored green. So always be careful when picking up a green sorbent.
Chemical resistance should not be confused with hazardous resistance. A flammable, toxic, explosive, or corrosive liquid does not become less hazardous when absorbed into the sorbent media.Only if vapors are suppressed will the risk of flammability be reduced; and while some sorbents may claim to do this, liability disclaimers still appear with these products.
Chemical Resistance and Inertness continue to be a priority. Users want to be safe with their Sorbent inventories. Whether it is an "aggressive" or "non-aggressive" liquid, the correct sorbent must be on hand. 100% polypropylene sorbents have the best chemical resistance (e.g., concentrated hydrofluoric acid, potassium hydroxide, gasoline, etc. can be absorbed).
8. Who uses sorbents?
This can be a short answer. EVERYBODY (well almost everybody).
Almost each repair shop, factory, printing company etc. uses industrial liquids. And where these liquids are used they are also spilled.
The name of our most sold sorbent (MRO) is an abbreviation of Maintenance, Repair and Operation. Meaning that they can be used in each industry, e.g.:
- Metal processing
- Cable production
- Ink and paint industry
- Fire service
- Cleaning companies
- Disaster combating companies
- Paper factories
- Energy companies
- Oil refineries
- Petro chemical plants
- Automotive manufacturing and repair
9. What about disposal?
The advantages in regard to disposal of MBPP Sorbents compared to all other types of sorbents are eminent:
- Less volume
- Less weight
- No rot or mildew
- Liquids can be reclaimed (separating the liquid from the sorbent so the liquid can be recycled)
- No special equipment needed for handling
- Non biodegradable
10. How do sorbents work?
100% polypropylene is naturally hydrophoic or repels water, while like materials adhere or are attracted to the surface area of the polypropylene fibers. And since polypropylene is a petroleum derivative, it will absorb any oil or oil-based liquids.
Terminology Note: As mentioned earlier, polypropylene sorbents technically adsorb fluids, but throughout the industry the more generic "absorb" or "absorbent" is typically used. So the rest of this training will utilize the more generic industry standard.
In addition to having a lower density than water, polypropylene's natural aversion to water made these "oil only" sorbents an excellent choice for environmental clean up. Both the oil and the sorbent floated on the top of the water.
As industrial and other indoor sorbent applications emerged, sorbents were needed to clean up more than just petroleum-based spills. Water-based liquids and chemicals leak, drip and spill in manufacturing and industrial facilities around the world. So by adding a surfactant into the manufacturing process, sorbents can absorb both oil and water-based liquids - making the product hydrophilic.
Dyes are also added in to the manufacturing process to color - code sorbents - creating a very easy to use color system for identifying which sorbent you need for the job:
- White - Oil Only
- Grey - Universal
- Green - Chemical