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SURFACTANTS FOR MINING AND AGRICULTURE

This article presents the use of polyisobutylene, phenol-formaldehyde and sugar derived surfactants and their applications in the mining industry and agriculture. A comprehensive overview of mining related surfactants, surfactants for agriculture as well as what is known regarding enhanced oil recovery is given. Lastly, sugars as building blocks for surfactants and possible new structures for phenol-based resins and their applications will be discussed.

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Surfactants for the Mining and Related Industries

Some of the most important areas for mining surfactants involve the following:

  • Emulsifiers for emulsion explosives
  • Encrusting agents
  • Residual agents
  • Foam agents
  • Wetting agents
  • Oil Recovery

Each of these will be briefly discussed separately.  A good introduction to the size of the mining industry in South Africa and the African Continent is also available at the website referred to below.[1]

Emulsifiers for emulsion explosives

Emulsifiers for emulsion explosives represent a curious situation in which high volumes are required but with a concomitant high margin that can be charged for these products.  Most emulsion explosives are based on polyisobutylene (PIB).  Various grades of polyisobutylene are available with different molecular masses.  The typical structure for PIB and its reaction with maleic anhydride to form polyisobutylenesuccinic anhydride (PIBSA) is given below in Schematic 1.

Typical ene reaction between PIB and maleic anhydride to form polyisobutylenesuccinic anhydride.

Schematic 1:

Typical molecular weights for PIBSA, which is the precursor to emulsion explosives is in the region of 950 Dalton.  The “ene” reaction takes place at an elevated temperature of 210 °C.  Once the PIBSA derivative has been made, the various types of emulsion explosives can be made.  Most of these will be based on reactions with mono ethanolamine, diethanolamine, diethyl aminoethanol and methyl aminoethanol.

Reaction of PIBSA with a ethanolamine derivative to yield an emulsifier.

Schematic 2:

The type of amine used has significant effects on the final properties of the emulsion explosive.  Emulsion explosives normally consist of an ammonium nitrate solution (85% by mass) with a fudge point of around 51 °C.  This emulsion is emulsified at 80 °C in an oil phase (7% by mass) containing about 1.5% by mass of the surfactant.  This is an inverse water-in-oil emulsion.  The most important aspect of the final emulsion is its shelf life which is a function of the type of surfactant.  Emulsion explosives are used in very different situations.  Sometimes a simple “load and shoot” scenario is used in which holes are drilled on the bench face of the mine (open pit).  This literally means that holes are drilled (3m to 5m deep) and immediately filled with the emulsion and shortly thereafter detonated.  In other cases, the emulsion requires so-called sleep time which comprises of drilled holes filled with the emulsion explosive and then left for weeks before the actual detonation of the explosive.  During this time the emulsion is still required to remain stable with no water ingress.  For this reason, the emulsion is an invert water-in-oil emulsion since the oil phase provides the water resistance and the surfactant provide the stability.

In many cases additional ammonium nitrate prill may be added to the emulsion to boost the oxidizer content.  A co-surfactant such as sorbitan monooleate can also be used to assist with the stability of the final emulsion and to reduce the cost.  Typically costs per kilogram of surfactant ranges from US$ 3 up to US$ 5 depending on the type of emulsifier being used.  A typical mining operation may use hundreds of tons of emulsifier in concentrated form per week.  A large company such as AEL, a subsidiary of AECI can use upward of a thousand tons of surfactant per month.  The same applies to the subsidiary of Omnia, Bulk Mining Explosives or BME.  Competition is fierce and the market for emulsifiers is conservative.  However, if a more cost-effective emulsifier can be produced most mining houses will be interested.  Suppliers of PIB and PIBSA include Nelson Brothers, Daelim, Texas Petroleum, BASF, Lubrizol, Orica and Maxam.

Emulsifiers for emulsion explosives is a niche area since the same structures used as emulsifiers in emulsion explosives are also used as additives for oils.  For this reason, far more research work is focused on the development of oil additives than emulsifiers.  However, literature has revealed that there may be room for the development of new types of oil additives as well as designs for emulsifiers based on phenol.

Alkylation of phenol with PIB

Schematic 3:

Schematic 3 shows that the functionalization of phenol or phenol derivatives with PIB is possible.  Once this is achieved many subsequent modifications can be made to the basic molecular structure including Mannich reactions with the previously mentioned ethanolamines.  An interesting modification to create an additive for oil is given below in Schematic 4.

Phenolated PIB as a precursor to the synthesis of engine oil detergents.

Schematic 4:

In Schematic 4 the synthesis steps to make a detergent for use in engine oils is shown.  However, this structure may very easily be used to design emulsifiers for emulsion explosives.  Alternatively, the multi-route process shown in Schematic 4 may be simplified as in Schematic 5 below.

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Mannich reaction between Phenolated PIB and an amine derivative.

Schematic 5:

Although PIBSA is the backbone of most emulsion explosive emulsifiers in terms of the hydrophobe, other types of hydrophobes may also be considered including maleic anhydride functionalized polyisoprene and polybutadiene (Kuraray).  However, these alternatives are significantly more expensive than PIB.

Technology in terms of emulsion explosives is focusing on a number of areas of interest including the ability to use waste oil and biodiesel as alternative fuel phases.  These oil types have very demanding requirements for the emulsifiers given the unknown composition of the waste oils and the ester functionality of the biodiesel.  Another area of development is to find additives that can remove heavy metals from the ammonium nitrate solution.  Sometimes the ammonium nitrate may have significant levels of aluminium, iron etc. which causes deterioration of the emulsion and act as crystal seeding agents.  The worst that can happen to any emulsion is for it to crystallize while in the hole.  Ammonium nitrate crystals are needle-like and will pierce the periphery of the droplet and initiate crystallization in a cascading process.  Once it starts, very little can be done to stop the process.

Polyisobutylene, modified to the intermediate PIBSA or phenolated, is used a variety of industries from additives in commodity plastics to making engine oil detergents, pour point depressants, etc.  There is a range of applications for PIB and functionalized PIB.  Some of the big players using PIB additives is Lubrizol who also manufactures emulsifiers for emulsion explosives but where the main focus is on using PIB and PIBSA derivatives as oil additives. Another interesting product that can be manufactured using PIB and styrene are block copolymers which can be used in rubbers and many other applications including biomedical coatings.  Random block copolymers of isobutylene and styrene can also be used to synthesize hydrophobes for surfactants.

There is a limit with regard to the molecular weight of PIB that can be used to manufacture PIBSA.  PIB depolymerizes at high temperatures during the “ene” reaction with maleic anhydride.  If lower molecular mass PIB is used (250 D) depolymerization is enhanced.  The ability to design phenol-based PIB molecules may provide the option of using lower molecular weight PIB polymers to serve as hydrophobes.  Lower molecular weight PIB based surfactants offer advantages such as a lower viscosity emulsifier.

Another significant aspect of mining explosives is water gel explosives.  Water gel explosives represent the majority of blasting agents used in the commercial market.  They consist of a fuel sensitized ammonium nitrate gel.  The consistency can vary from an easily pourable gel through to a hard solid.  Polyvinyl alcohol, guar gum and urea-formaldehyde resins can be used as gelling agents.  There exists the possible exploitation of resol gels in this regard to substitute or replace some of the polymers mentioned previously.

Encrusting and anti-caking agents

Encrusting agents provide a thin polymer coating on the material.  Typically coatings of this nature are provided by companies such as ArrMaz[1].  The surfactants used by ArrMaz are usually phosphoric esters dissolved in an oil carrier.  The surfactants pack against the surface of the prilled granule (for example ammonium nitrate).  The surfactant keeps the oil layer on the surface of the granule and reduces ingress of the oil into the granule that will reduce its structural integrity.  The coating also prevents oxidation and protects against wind and rain erosion.  It offers protection against spontaneous combustion by limiting the amount of air that can enter and react with the surface of the material (coal).  The PIBSA based precursor can also be used as an encrusting or anti-caking surfactant by opening the anhydride functionality with a long chain amine or by purposely opening the anhydride to form the di-acid and then reacting both acid functionalities with a long-chain amine to provide the surface-active agents in the form of an amine salt.  Typical loading onto granules (mining and fertilizer) is in the region of 2 to 4% per ton of material.  The actual active surfactant level is usually in the range of 25% (recommended).  Due to explosives regulations not more than 0.4% oil may be coated onto fertilizer grade ammonium nitrate due to its oxidative nature and the risk of combustion.  For this reason, the efficacy of the surfactant is of utmost importance.

Residual agents

Residual agents are applied on material that may become dusty and to control fugitive dust generated during conveying processes.  Typically, this type of material has a slightly sticky character.  When dust is present it sticks to the surface of the granule rather than becoming airborne. 

Foam agents

Foaming agents also aid with regard to minimize fugitive dust by capturing air-borne dust in the foam.  It can be used above or below ground in mines and is designed to reduce the amount of water required that may impact negatively on certain processes where additional moisture can reduce the BTU and lead to chute plugging.

Wetting agents

Wetting agents are designed to increase water’s ability to wet dust particles and suppress material emissions allowing better control of dust by using less moisture.  Adding wetting agents to water lowers the interfacial tension and allows water to wet particles better, penetrate rock or coal and thereby reducing dust. Wetting agents also suppress dust rapidly in moving applications such as conveyor transfers.  A typical wetting agent that is used in coal mines for example is dioctyl sulfosuccinate.  Typically, 1 mole of maleic anhydride is reacted with 2 moles of long chain fatty acids to form a dioctyl ester.  The maleic anhydride is further reacted with sodium metabisulfite (SMBS) through a modified “ene” reaction in which SO2 is liberated by the decomposition of the SMBS and adds across the double bond of the maleic anhydride molecule.  These emulsifiers are extremely versatile and are used as wetting agents in the coal mining industry as well as in animal feeds and in many other applications.

Oil Recovery

Oil recovery proceeds through two main processes namely primary and secondary recovery.  The primary recovery mechanism involves the available energy in the bore hole that contributes to the lift of the hydrocarbon volume to the surface.  The secondary mechanism relies on the introduction of energy into the hydrocarbon (oil) reservoir to force the remainder of the contents to the surface.  Both mechanisms are required for optimum oil recovery.

Secondary oil recovery methods include the use of water flooding and gas injection or a combination of both.  Various types of water flooding arrangements exist which are based on efficacy and economic viability.

Tertiary recovery processes also exist and strive to recover oil beyond the primary and secondary processes.  Tertiary oil recovery sees the use of liquids other than water to boost oil recovery.  Enhanced oil recovery (EOR) is a term that refers to the injection of fluids and energy not normally present in an oil reservoir.  EOR can be applied to all three processes including primary, secondary and tertiary.

EOR works by recovering oil through the injection of fluids and energy not normally present in the reservoir.  The injected fluids must accomplish the following:

  • Boost the natural energy in the reservoir
  • Interact with the reservoir rock/oil system to create conditions favorable for residual oil recovery that include the following:
    • Reduction of the interfacial tension between the displacing fluid and oil.
    • Increase the capillary number.
    • Reduce capillary forces.
    • Increase the drive water viscosity.
    • Provide mobility control.
    • Oil swelling.
    • Oil viscosity reduction.
    • Changing the reservoir rock wettability.

The mobility ratio, M for water flooding is the ratio between the water and oil mobilities which is a function of their individual viscosities.  A large difference between the water and the oil gives a large mobility ratio which promotes fingering of the water through the more viscous oil phase and reduces the efficiency of oil recovery.  By increasing the viscosity of the water phase the mobility factor can be increased.

Another aspect that requires improvement is the capillary number.  By increasing the capillary number, Nc the oil trapped by capillary forces are liberated and recovered.  To achieve this surfactants and alkaline flooding is used.

To improve mobility two techniques are commonly used namely polymer flooding and gels (crosslinked polymers).  Polymer flooding is the most widely used EOR process for mobility control.  The use of gels or crosslinked polymers acts as permeability reducing agents to plug high mobility flow channels in the rock.  Some of the well-known polymers used in polymer flooding are hydrolyzed polyacrylamides and Xanthan gum.  Examples of polymer gels include crosslinked acrylic polymers such as chromium (III) carboxylate/acrylamide polymers.  Apart from the polymers mentioned here, there are a myriad of alternative polymers and surfactants available in the market including phenol/formaldehyde-based polymers, surfactants and gels.  Of importance to note is the use of resol gels in applications such as well shut-off in oil reservoirs.  By modifying the gelation properties of these gels, they may be used in enhanced oil and gas recovery mentioned previously as well as in the more recent fracking activities.

Agricultural Applications of Surfactants

Surfactants including those based on phenol formaldehyde condensation products are used in various applications in agriculture.  One of the main areas of application is in seed coatings.  The merger of seed coating formulation science and surfactants provide solutions with regard to water scarcity by modifying hydrophobic soils (soil conditioning) as well as to aid in delivering certain additives such as herbicides, pesticides and growth factors to the developing root system of the seedlings.  Surfactants can also be used in pesticide suspension concentrates which is a separate application to seed coatings.  Some of the most successful types of surfactants used in the agricultural industry for emulsifying low water-soluble additives such as pesticides are the so-called ABA block copolymers.  These are typically available from BASF as their Pluronic range and from Croda as their Synperonic range.  Normally these block copolymers are based on segments of polyethylene glycol and polypropylene glycol of varying molecular weights.  The agricultural sector and fertilizer industry in South Africa and Africa is enormous. In addition, not only should southern Africa be considered but all sub-equatorial regions including South America and Australia.  The various seed-related companies in South Africa are shown in Appendix A.  It is interesting to note that an international player such as the Dutch Incotec[1] group has announced the intention to build a plant for seed coatings in Pietermaritzburg in South Africa.  In addition, Syngenta has started an R&D facility in Brits, a town close to Pretoria in South Africa.  Among Syngenta’s aims is to develop seed related technology for Kenya.

Possible new Surfactant Technologies to Address the Mining and Agricultural Industries

The previous section has highlighted the various areas of application for surfactants in the mining and agricultural sectors.  Some of the phenol-formaldehyde and phenol-based additives and surfactants are listed below.:

  • Fuel and lubricants
    • Anti Wax Sedimentation
    • AO for jet fuels
    • Dispersants
    • Detergents
    • Anti-wear agents
    • Rust and corrosion inhibitors
    • Friction modifiers
    • Rheology modifiers
    • PDDP Phenate technology
  • Demulsifiers
    • Alkyl phenol novolacs
  • Surfactants
    • Metal Extraction
    • Inks
    • Dyes

Some structures of phenol derived surfactants.

Schematic 6: 

Schematic 6 depicts some of the alkyl phenols that are possible.  The main building blocks for the surfactants are phenol and olefins.  In addition, water-soluble resols should also be counted as potential surface-active agents (Schematic 7).  The application of resol gels in oil recovery has been mentioned.  Another area of great potential where resol gels could also find a useful application is in the area of superabsorbents.  Not only are superabsorbents used in nappies but this technology is now used in agriculture to improve the capacity of soil to hold water.

Resole structure

Schematic 7:

Surface active agents for mining, oil and gas as well agricultural applications derived from phenol, an alkene and formaldehyde.

Schematic 8:

The author is well versed in the use of phenol and formaldehyde polymers, and it is therefore interesting to investigate what can be done with phenol and formaldehyde to synthesize surface-active molecules.  Examples of this technology are given below in Schematic 8.

The structures shown above are only based on phenol and formaldehyde, structures based on other aryl structures are also possible.  Good examples of the structures in this regard are to be found on the website of Oil Chem Technologies[1] as well as the website of Kao.[2]  The technology is also relatively straight forward based on the reaction of formaldehyde with phenol, formaldehyde sulfonation and condensation.  These types of surfactants can be used in the following areas of application:

  • Detergents
  • Emulsifiers
  • Wetting agents
  • Agricultural surfactants
  • Metal treatment
  • Corrosion inhibition
  • Oil fields
  • Emulsion polymerization
  • Lubricants
  • Heavy duty cleaners

In addition, further alkoxylation can be done on these basic structures to include the attachment of polyethylene glycols, polypropylene glycols as well as block copolymers of these.  Mannich modification of phenolic resins may also be considered.

[1]http://www.oil-chem.com/

[2]https://chemical.kao.com/content/dam/sites/kao/chemical-kao-com/global/pdf/forum/catalog_surfactants_1505.pdf

Mannich reaction with etholamine derivative followed by protection of phenolic OH with AcAc followed by reaction with maleic anhydride. (A = ethyl acetoacetate group)

Schematic 9:reaction with etholamine derivative followed by protection of phenolic OHreaction with etholamine derivative

The ability to functionalize a phenolic resin such as a novolac with a functional amine and then possibly reacting it further to include acid and double bonds allows for many manipulations.  Specifically, the type of ABA block copolymers mentioned earlier, or the Gemini class of surfactants is very versatile across a wide range of applications.  For example, ABA block copolymers with a hydrophobic B block can be achieved by esterification of the acid moiety (Schematic 10).  The ethyl acetoacetate groups prevent the acidic phenolic OH groups from reacting with the maleic anhydride functionality.  Alternatively, this may be allowed irrespectively to obtain functional novolac resins with carboxylic acid functionality.

Esterification of diacid functional novolac

Schematic 10:

Esterification of diacid functional novolac

The structure in Schematic 10 may seem overly complex but the essence of the story is that by end-functionalizing short chain novalacs using for example a Mannich reaction with functional amines, opens up possibilities to design novel Gemini type surfactant structures.  Another way of functionalizing a novolac is to mask the acidic OH groups on the phenol ring with an allyl halide.  By doing this not only is it possible to introduce functional groups for the purpose of surfactancy and the ability to design novel surfactant structures, but it also allows for many other methods of crosslinking novolacs that may not be immediately apparent.

In Schematic 11 a novolac is reacted with allyl chloride which serves to provide vinylidene groups that can be used in the formation of Diels Alder ene reactions.  In this way anhydride functionality through maleic anhydride can be introduced.  This modification can be used to make surfactants by opening the anhydride with a polyethylene glycol (excess) and it can also be used to serve as crosslinking points for Novolac/polyester blends.  Simply adding a polyamine or a polyol to the novolac will result in crosslinking at low temperatures (< 100 °C).

Functionalizing a novolac with allyl chloride and using Diels Alder reaction to introduce maleimide and anhydride functionality.

Schematic 11:

Functionalizing a novolac with allyl chloride

Schematic 12 below shows the introduction amine alcohol derivative that imparts polar groups.  These type of surfactant structures may very well be used as co-surfactants and main surfactants in many mining applications as well as in seed coatings.  The anhydride functionality may serve as an attachment point for certain pesticides such as the nicotinoids, a range of pesticides that interfere with the neural cells of insects and which must be systemically available for a young germinating seedling.  These types of pesticides have very low water solubility but as a salt could be made available for root uptake.

Diisobutylene Maleic Anhydride Copolymers

Copolymers of diisobutylene (DIB) and maleic anhydride offers further surfactant opportunities.  DIB and maleic anhydride copolymers are obtained by reacting DIB and maleic anhydride as well as any other functional acrylic monomer at temperatures of 125 °C to 150 °C under a nitrogen blanket at 6 – 7 bar pressure.  The free radical polymerization (for detail see Appendix B) between DIB and maleic anhydride proceeds through a charge transfer complex that facilitates polymerization.

Free radical polymerization of DIB and maleic anhydride to yield alternating copolymers of DIB and maleic anhydride

Schematic 12:

Free radical polymerization of DIB and maleic anhydride

DIB and maleic anhydride copolymers are used in the following applications:

  • Washing detergents.
  • Tanning in the leather industry.
  • Paper sizing and paper processing agents.
  • Agrochemical granules.
  • Mineral ore slurries.
  • Dye and pigment dispersants.
  • Paints and coatings.
  • Oil lubricants and fuel additives.
  • Water-based varnishes.
  • Pesticide suspensions.
  • Spray dried re-dispersible powders.
  • Heat sensitive recording material.
  • Cement admixtures.
  • Coal-mine slurries.
  • Water treatment chemicals.
  • Water soluble adhesives.
  • Treatment of flue gases.

Some industrial names for these copolymers are:

  • Xiran, from Polyscope[1]
  • Dylark range from Nova
  • Orotan range, DuPont.
  • Tamol range from DOW.
  • Glissopol range from BASF
  • Ultravis from BP.

While the applications of diisobutylene maleic anhydride copolymers are significant, the ability to control the molecular mass and polymer structure by means of Controlled Free Radical Polymerization (CFRP), offers more opportunities.  Two of the most important mechanisms for CFRP is Atom Transfer Radical Polymerization (ATRP) and Reversible Addition-Fragmentation Chain Transfer (RAFT).  Schematic 13 illustrates the various products and structures that can be achieved with CFRP.

[1]http://www.polyscope.eu/en/content/pages/neat_resin_sma.aspx

The ability to control polymer structures and molecular weights through ATRP and RAFT.

Schematic 13:

A very good summary of ATRP can be found in reference 15 while reference 16 details the mechanism of RAFT.  Schematic 14 illustrates the structure of various RAFT chain transfer agents as well as the mechanism of polymerization.  The type of RAFT chain transfer agent is related to the type of monomer.  For example, methyl methacrylate will require a completely different type of RAFT agent compared to vinyl acetate because of the level of activation of the double bond in the monomer structure.

The RAFT chain transfer agent structure and the mechanism of polymerization.

Schematic 14:

Although CFRP became well-known in academic circles during the 1990’s, the commercial unavailability of many of the chemicals required in ATRP and RAFT postponed the commercialization of this technology until the start of the 21st century.  Today many centers of excellence can be found in South Africa at Stellenbosch University, Eindhoven University in the Netherlands and the ATRP group at Carnegie Melon University to name but a few.

Adjacent Technologies: Sugar based Surfactants and Sugar Building Blocks

The use of sugars as an alternative to formaldehyde is gaining momentum.  It has been shown for example that novolac resins can be prepared by using a strong acid as catalyst at moderately high temperatures between 120 °C – 150 °C.  The reported starting ratio of phenol to glucose was 1:0.5.  The resin still requires curing using hexamethylenetetramine.

The fact is glucose is an abundant raw material and can be readily made from sucrose to yield fructose and glucose.  This so-called inversion process of preparing glucose from sucrose is shown below in Schematic 15.  Worldwide demand is much less than supply (long market) and countries having large sugar resources are exporting it at prices that undercut the production cost of locally produced sugar in many other countries (In other words, dumping).  An alternative would be to use sugar as a raw material not only for transportation fuel but also as a building block to make other molecules.  In this regard, glucose is an excellent example of a building block that can be examined for making phenol-based resins.

Hydrolysis of sucrose to glucose and fructose.  Usually achieved by adding citric acid to catalyse the hydrolysis reaction.

Schematic 15:

Hydrolysis of sucrose to glucose and fructose

 

Another technology that uses sugars in a significant way is the development of sugar-based surfactants, an adjacent technology that could have significant synergies with phenol-formaldehyde based surfactant technology.[1]  An example of the structure of one such sugar-based surfactant is given below in Schematic 16.

An example of an alkyl glycoside sugar based surfactant

Schematic 16:

alkyl glycoside sugar based surfactant

Apart from the fact that oil-derived raw materials such as phenol and formaldehyde will eventually run out which means the cost of these raw materials will escalate over time, the connection with a so-called “green” sustainable technology may have further advantages since some customers may be willing to pay a premium for this type of technology.  Appendix C gives further examples of sugar-based surfactants.  Some of the companies active in this regard are:

Sugar-based surfactants are finding uses in all the major applications sited earlier.  This includes mining and agriculture and it is for this reason that it may deemed a good fit in terms of an available technology. .Another very interesting alternative that may very well impact directly on the use of phenol is the reaction with phenol and glucose to yield the structure in Schematic 17.

Phenyl –β-Galactoside.

Schematic 17:

Phenyl –β-Galactoside

No references of using phenyl-β-galactoside to make phenolic resins could be found for this document but what may be possible (and this is an untested hypothesis) is to make the following type of resins (Schematic 18).

Possible structure of a phenolic resin based on phenyl-β-galactoside. (S = Sugar moiety).

Schematic 18:

structure of a phenolic resin based on phenyl-β-galactoside

REFERENCES

  1. Long chain phenols – part 30: A rate study of the Mannich reaction of phenols (with particular reference to 3-pentadecylphenol), Journal of Chemical Technology and Biotechnology, Vol. 53, Iss. 4, pp.389-396, DOI: 10.1002/jctb.280530412
  2. Recent Technology Developments in Surfactants and Polymers for Enhanced Oil Recovery, Jun Lu et al., International Petroleum Technology Conference, 26-28 March, Beijing China, Document ID: IPTC-16425-MS, (2013)
  3. Synthesis of phenol-terminated polyisobutylene: Competitive chain transfer reactions, J.M. Rooney, Journal of Applied Polymer Science, Vol. 25, Iss. 7, pp.1365-1372, (2003)
  4. Method for Producing Mannich Adducts that contain polyisobutylene phenol, US patent 8,016,898 B1, (2011)
  5. Research on novel polyisobutylphenoxyethyl polyamines as gasoline detergents, HejunGuo, Fuel Chemistry Division Preprints, Vol. 47, No. 2, pp. 578-579, (2002)
  6. The use of adducts of N-alkylalkanolamines (AAA’s) with alkenyl succinic anhydrides (ASA’s), AAA carboxamides and structurally unique AAA’s as emulsifiers in metalworking fluids, M.D. Gernon et al,
  7. Bismaleimide modified by allylNovolak for superabrasives, Zheng Hongfei, et al., Chinese Journal of Chemical Engineering, Vol. 15, No. 2, pp.302 – 304, (2007)
  8. New polymeric comb dispersants for agricultural formulations: A comparison of performance in pesticide suspension concentrates, A.J. Stern, C.M. Elsik,
  9. Synthesis of novolac-type phenolic resins using glucose as the substitute for formaldehyde, Mingcun Wang et al, Journal of Applied Polymer Science, Vol. 118, Iss. 2, pp.1191-1197, (2010)
  10. Piispanen, Peter S; Synthesis and Characterization of Surfactants Based on Natural Products. KunglTekniskaHögskolan, Stockholm, Maj 2002
  11. New chelating glucose-based surfactants, Nadège FERLIN, Laboratoire des Glucides – UMR 6219, Université de Picardie Jules VERNE AMIEN (http://www.ensc-lille.fr/actu/GCI/ferlin.pdf )
  12. New Block Copolymers of Isobutylene by Combination of Cationic and Anionic Polymerizations DISSERTATION zurErlangung des akademischen Grades einesDoktors der Naturwissenschaften (Dr. rer. nat.) in FachChemie der FakultätfürBiologie, Chemie und Geowissenschaften der Universität Bayreuth vorgelegt von NemesioMartínez-Castro Geboren in Tampico / Mexiko, Bayreuth, 2004
  13. INVESTIGATION OF THE MECHANICAL AND THERMAL PROPERTIES OF POLY(STYRENE-BLOCK-ISOBUTYLENE-BLOCK-STYRENE) (SIBS) AND ITS BLENDS WITH THYMINE-FUNCTIONALIZED POLYSTYRENE A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Master of Science Kathleen A. Perevosnik December, 2008
  14. Thermosetting Compositions Containing Alternating Copolymers of Isobutylene type monomers, PPG Industries, US Patent Application 2004/0242777 A1, (2004).
  15. SYNTHESIS, CHARACTERIZATION AND APPLICATION OF BRANCHED POLYMERS AS MIDDLE DISTILLATE FUELS COLD FLOW ADDITIVES, Proefschrift ter verktijging van de graad van doctor aan de Technische Universiteit Eindhoven door Morang Norah Maithufi, geboren te Rustenburg, Zuid Afrika, ISBN: 978-90-386-2329-0, Eindhoven University.
  16. Living Free Radical Polymerization by Reversible Addition-Fragmentation Chain Transfer: The RAFt Process, Ezio Rizzardo, San H. Thang et al, Macromolecules, Vol. 31, pp.5559 – 5562, (1998).
  17. Surfactants and their applications, L.L. Schramm, E.N. Stasiuk, D.G. Marangoni, Annual Reports on Progress in Chemistry, Section C., Vol. 99, pp.3-98, (2003), DOI: 10.1039/b208499f.
  18. Principles of Polymerization, Fourth Edition, George Odian, John Wiley & Sons, Hoboken New Jersey, 2004, ISBN 0-471-27400-3.

Appendix A:

Seed producing companies in South Africa

Seed producing companies in South Africa

Appendix C:

Examples of sugar based surfactants

sugar based surfactants

Appendix B:

Free radical polymerization

Initiation:

 

 

 

Propagation:

 

 

 

Transfer to monomer:

 

 

 

Transfer to chain transfer agent (CTA):

 

 

 

Termination:

Appendix D:

Characterization of surfactants

The characterization of surfactants for mining and agricultural applications generally does not differ from conventional surfactants.  In general, the most important physical aspects also play a role such as the Critical Micelle Concentration (CMC), the cloud-point and Kraft points are all considered.  A very good reference with regard to surfactant characterization can be found in reference 17 and one of the accompanying pdf files to this document.

When it comes to mining and agricultural surfactants and specifically polymeric surfactants, additional tests are required which also requires additional equipment.  Features such as the interfacial tension become critical and can be measured using a Kruss K100 shown below for the measurement of receding and advancing contact angles.

Schematic D1.Kruss K100 receding and advancing contact angle measurement of polymeric surfactants.

Another critical parameter to study is the deformation over time of emulsions.  This is done by subjecting emulsions to controlled shear and stress deformations using rheometers such as the MCR 301 from Anton Paar. A further piece of equipment used with polymeric surfactants is the droplet size analyzer such as the Malvern Mastersizer 2000 (Schematic D3).

Schematic D2.MCR301 rheometer.

Schematic D3.  Malvern Mastersizer 2000 for droplet size analysis.

A typical droplet size distribution is given in Schematic D4.  This is of considerable interest, especially for emulsion explosive emulsifiers as the large droplet fraction is usually an indication of instability.

Schematic D4.  Droplet size distribution for emulsion explosive emulsifier.

Another aspect of emulsifiers for mining applications is the large droplet analysis.  Apart from the Malvern instrument, phase contrast microscopy can be used to characterize large droplets which are an indication of emulsifier efficacy both for mining and agricultural purposes (Schematic D5).

Schematic D5.  Large droplet analysis using phase contrast or dark field microscope analysis.

The images obtained from microscope investigations should be analyzed using convenient software programs that can classify droplets greater than a specified range.  Many of the equipment listed above are by South African standards very expensive.  It may be noteworthy to consider outsourcing many of the characterizations necessary for polymeric surfactants such as through the innovation option for instance the Eindhoven Innovation[1] portal.

[1]http://www.tue.nl/innoveren/tue-sure-innovation/

Frequently asked Questions about Surfactants

  1. What are surfactants?

    Surfactants, or surface-active agents, are compounds that lower the surface tension between two substances, such as liquids and solids. They have both hydrophilic (water-attracting) and hydrophobic (water-repelling) properties, allowing them to interact with various materials.

  2. How do surfactants work?

    Surfactants work by positioning themselves at the interface between different phases (like oil and water). Their hydrophobic tails attach to oils or dirt, while their hydrophilic heads remain in water, effectively emulsifying or dispersing the unwanted substances.

  3. What are the different types of surfactants?

    Surfactants are classified into four main types based on their charge: anionic (negatively charged), cationic (positively charged), nonionic (no charge), and zwitterionic (both positive and negative charges). Each type has specific applications depending on its properties.

  4. What are common applications of surfactants?

    Surfactants are widely used in cleaning products, detergents, personal care items (like shampoos), pharmaceuticals, food processing, and industrial applications such as emulsifiers in paints and coatings.

  5. What is critical micelle concentration (CMC)?

    CMC is the concentration of surfactants in a solution at which micelles begin to form. Below this concentration, surfactants primarily reduce surface tension; above it, they aggregate into micelles that can solubilize oils and other hydrophobic substances.

  6. Are surfactants safe to use?

    Many surfactants are safe for use in consumer products; however, some can be irritating to skin or eyes. It’s essential to follow safety guidelines and use appropriate concentrations in formulations to minimize risks.

  7. How do surfactants affect cleaning efficiency?

    Surfactants enhance cleaning efficiency by breaking down and suspending dirt and grease, allowing them to be easily rinsed away. Their ability to lower surface tension helps penetrate surfaces more effectively.

  8. Can surfactants be biodegradable?

    Yes, many modern surfactants are designed to be biodegradable, meaning they can break down into harmless substances in the environment. This is particularly important for reducing pollution from cleaning products.

  9. What role do surfactants play in emulsions?

    In emulsions, surfactants stabilize the mixture of oil and water by reducing interfacial tension. They prevent the separation of phases by forming a protective layer around dispersed droplets.

  10. How can surfactant performance be measured?

    The performance of surfactants can be measured using various techniques, including surface tension measurements, foam stability tests, and emulsion stability assessments. These tests help determine their effectiveness for specific applications.

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