Surfactants Flashcards
(26 cards)
What are surfactants
Surface active agents with a hydrophilic head and hydrophobic tail that reduce surface and interfacial tension
Surfactant roles in formulated products
detergency, cleansing, emulsifying, dispersing, wetting, solubilising, foaming, conditioning
Kinds of surfactants
Anionic (SLES), cationic (quats), amphoteric (CAPB), nonionic (spans, tweens)
What is HLB
hydrophilic-lipophilic balance is a numerical scale (0-20) describes how water or oil loving a surfactant is.
HLB calculation
HLB = Mh / M x 20
molecular weight of head / total molecular weight.
0 = lipophilic
20 = hydrophilic
Cpp
critical packing parameter describes what shape a micelle will form
Cpp = v / (a x l)
CMC
critical micelle concentration, concentration where micelles begin to form
Issue with HLB
low scale products fine but doesn’t represent whole system. Mainly only relevant for O/W emulsions
What is HLD
hydrophilic-lipophilic difference describes full properties of a system and predicts a better surfactant
HLD calculation
cC - k(EACN) - å()T + s(f)
cC = surfactant characteristic
k + å = constant
()T = temp difference from 25ºC
f(s) = function of salinity
Colligative properties
of solutions depend on number of solute particles. BP elevation, FP depression, VP decrease, OP
BP elevation
BP of solutions increase - solute particles block solvent from jumping into vapour phase, require more energy. T = i x K x m
FP depression
FP of solutions decrease - solute particles block solvent from forming lattice, require more energy.
T = i x K x m
VP decrease
solvent usually at equilibrium of liquid and vapour phase, solute blocks liquid particles from jumping into vapour phase, less particles in vapour phase. ()P = i x X x P
OP
osmotic pressure is movement of solvent particles through semi-permeable membrane from low solute to high to make equal concentration. π = i x M x R x T
Paint
Multi-phase colloidal dispersion of solid (pigment) particles in liquid medium.
Main ingredients in paint
pigment, binder, dispersant, solvent, additives
Pigments
give opacity and colour, insoluble in the solvent
Binder
helps form film over paint and bind to substrate
Dispersing agent
Surface active agent helps disperse insoluble particles so they don’t coalesce, aggregate or sediment
Solvents
dissolve binder, control viscosity, evaporate when paint applied
Additives
enhance properties of paint
Types of pigments
inorganic, organic, primary, secondary
Primary pigments
usually inorganic, more expensive, high RI, opaque and strong colour
