I would like a simple explanation of emulsion polymerization, and I would like to know whether the process requires UV light and how UV light will effect the process.
Dear Luke Wang, emulsion (direct and inverse) polymerization is a heterogenious process in which a dispersed polymerizable phase surrounded by an emulsifier (surfactant: surface active agent) forming and maintaining micelles. These latter is suspended in the continuous phase which in most case being water. The mode of initiation depends on each situation, and it may be activated by thermal energy or light, including UV. Light bring the necessary energy (hv) to promot polymerization. Regards
Emulsion polymerization involves the formation of an initial emulsion from two immiscible phases, commonly an aqueous phase and organic phase. The emulsion has to be stabilized by some form of surfactant or small particles so the two phases do not separate before the polymerization reaction is complete. A common example might be a salt solution as and aqueous dispersed phase, styrene as the continuous organic phase with Tween as the surfactant.
Polymerization is then initiated by UV or some form of chemical initiator often at raised temperature. Normally the continuous phase is then polymerized to form a porous solid monolith containing voids in the shape of the dispersed phase droplets. If the dispersed phase concentration is high enough the solid walls between the droplets are not formed and the monolith has significant permeability. The ability to control the amount (volume %) and size of the droplets in the template emulsion to produce a monolith tailored to specific applications why emulsion polymerization is often researched.
If the dispersed phase is then undergoes polymerization small solids particles in the shape of the dispersed phase droplets will be formed. If both phase polymerized a composite solid material will be formed.
Emulsion polymerization is an important industrial process used to produce a great variety of polymers of multiple uses (e.g. paints, adhesives, coatings, varnishes, etc.)
There are various components required in formulating latexes: synthetic ingredients such as monomer(s), surfactants, and initiator and post-synthesis ingredients such as biocides added to serve a specific purpose. In addition, the 8 number of ingredients added to a formulation depends on the type and scale. For example, a laboratory scale recipe contains significantly fewer ingredients than a more complex commercial emulsion polymerization that can have well over 20 different ingredients. Regardless, ingredients affect both the rate at which latex particles are synthesized and the composition and characteristics of the final product.
Emulsion polymerization has significant advantages over bulk and solution polymerization
Ø These advantages result mostly from the multiphase and compartmentalized nature of the emulsion polymerization which allows for production of polymers of high molecular weights at high polymerization rates at the same time, delivering a high versatility to product qualities.
Ø Another distinct advantage of employing emulsion type of polymerization process is a very good controllability of process temperature. This is again caused by the multiphase nature of the process and by the excellent heat conducting properties of water being present in relatively large amount in the reactor
Now the second question whether the process requires UV light? Well it depend upon different methods for the synthesis of Emulsion polymerization like free radical emulsion polymerization, microwave assisted emulsion polymerization, radiation induced polymerization like UV irradiation emulsion polymerization method etc. So UV irradiation is one of the method for emulsion polymerization.
Thirdly , you ask for how UV light will effect the process? The radiation-induced initiation process makes it possible to trigger polymerization under reaction conditions (temperature, initiation rate, type, location and spatial distribution of the initiating species) that are unusual, if not specific, compared to the activation with thermally cleavable initiators (such as peroxides) or with redox systems (such as a reductive metal associated with a peroxide).
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