Lecture 10

Question 1

What are the most common processes for performing free-radical polymerization?

Answer 1

1. Bulk polymerization
2. Solution polymerization
3. Gas-phase polymerization
4. Dispersion polymerization
5. Precipitation polymerization
6. Suspension polymerization
7. Emulsion polymerization

Imp note: Although the processes are described below specifically in the context of free-radical polymerization, the general features, advantages and disadvantages also apply to other types of polymerization carried out using these processes.

Question 2

Which polymerization techniques are Homogenous and which are heterogeneous?

Answer 2

Homogenous - Bulk and solution

Heterogenous - Gas-phase polymerization, Dispersion polymerization, Precipitation polymerization, Suspension polymerization, Emulsion polymerization

Question 3

What is bulk polymerization?

Answer 3

is the simplest process and involves only the monomer and a monomer-soluble
initiator (no solvent present). Here we assume the polymer is soluble in the monomer.

Question 4

Why is it hard to reproduce bulk polymerization?

Answer 4

according to the kinetics of free radical polymerization, we know that a high concentration of monomer gives rise to high rates of polymerization and high
degrees of polymerization. However, the viscosity of the reaction medium increases rapidly with conversion (i.e. as polymer forms, there is less monomer, i.e. less ‘solvent’), making it difficult to remove the heat evolved upon polymerization, because of the inefficient stirring, and leading to
autoacceleration. Bulk polymerization can, therefore, be difficult to reproduce

Note also that in order to increase the molar mass of the polymer produced, [I] and/or polymerization temperature
have to be reduced, which in either case will result in a reduced rate of polymerization. Thus, there has to be a compromise between polymer molar mass and speed of production

Question 5

How can we reduce the viscosity build-up and autoacceleration found in bulk polymerization?

Answer 5

The problems of viscosity build-up and autoacceleration normally are avoided by restricting the reaction to low conversions, though on an industrial scale the process economics necessitate recovery and recycling of unreacted monomer

Question 6

What are the advantages of bulk polymerization

Answer 6

• The principal advantage of bulk polymerization is that it minimizes contamination by impurities
  and produces a high molar mass polymer of high purity.
• No solvents

Question 7

What are the disadvantages of bulk polymerization?

Answer 7

1. Viscocity increase
2. gel effect
   (both contribute to making it hard to reproduce)
3. heat transfer happens
4. very broad MWD
5. Removal of residual monomer
6. pumping
7. fouling

Question 8

What are some applications of bulk polymerization?

Answer 8

1. PMMA sheets, rods, tube (batch processes)
2. High-impact polystyrene (HIPS)
3. Dental filling

Question 9

How can we prepare transparent
sheets of poly(methyl methacrylate) [PMMA]?

Answer 9

Transparent sheets of poly(methyl methacrylate) are prepared in a two-stage process. The monomer is first partially polymerized to yield a viscous solution which then is poured into a sheet mould where polymerization is completed at high temperature. This method reduces the problems of heat transfer and shrinkage.
The high ratio of surface area to volume of the sheet moulds provides for efficient heat transfer and control of autoacceleration, and the initial partial monomer conversion reduces problems associated with contraction in volume upon polymerization within the sheet mould.

Question 10

What is High Impact Polystyrene (HIPS)?

Answer 10

HIPS is an application of bulk polymerization and It is a polymer blend of polystyrene (very brittle) and polybutadiene (very rubbery). This allows for the improvement of impact resistance of the very brittle polystyrene, as now any energy applied will be dissipated by the rubbery polybutadiene (This is known as rubber toughening all will be discussed in detail below)

Imagines of HIPS and how it is made are shown in notes!

Note that the interfaces between the two polymers is stabilized by graft copolymer

Question 11

What is rubber toughening?

Answer 11

Rubber toughening is when a glassy
polymer matrix is toughened through the incorporation of a second phase consisting of particles which usually are spherical and of a rubbery polymer above its glass transition temperature, Tg. This can lead to significant improvements in the mechanical behaviour of the matrix polymer

Question 12

How does the mechanical properties of polystyrene change upon incorporation of polybutadiene?

Answer 12

Based on the stress-strain graph (shown in notes under flash card 9) we see that polystyrene shows brittle behaviour, whereas the inclusion of the rubbery phase causes the material to undergo yield and the sample to deform plastically to about 40% strain before eventually fracturing. The plastic deformation is accompanied by stress-whitening, whereby the necked
region becomes white in appearance during deformation. This is due to
the formation of a large number of crazes around the rubber particles in the material.

Question 13

How are dental fillings made?

Answer 13

Monomers, photoinitiators, and some fillers (like silica) are placed within the tooth. Upon exposure to the UV light, the initiator makes radicals leading to bulk polymerization and crosslinks forming!

Some possible monomers used are shown within the notes.

Question 14

What is solution polymerization?

Answer 14

Polymerization of a monomer in the presence of a solvent.

Question 15

What are the requirements for the solvent in solution polymerization (IMP point)?

Answer 15

• The solvent must be selected so that it dissolves not only the initiator and monomer but also the polymer that is to be produced.
• The solvent needs to be included at a level which reduces the viscosity of the reaction medium so that it can be stirred efficiently across the full conversion range, thus facilitating good heat transfer and eliminating (or at least enabling control of) autoacceleration.

Question 16

What are the advantages of solution polymerization?

Answer 16

• lower viscosities
• better temperature control
• better control gel effect
• the solution may have an application

Question 17

How can we isolate the polymer made in solution polymerization?

Answer 17

Isolation of the polymer requires either:

1. evaporation of the solvent, or
2. precipitation of the polymer by adding the solution to a sufficient (typically at least 5×) excess of a non-solvent (such that the final mixture of solvent/non-solvent overall is a nonsolvent for the polymer, but still a solvent for any unreacted monomer and initiator), and then collection of the polymer by filtration or centrifugation followed by drying.

Clearly, neither process is very efficient and so tends to be restricted to laboratory work. Thus, commercial use of solution polymerization tends to be restricted to the preparation of polymers for applications that require the polymer to be used in solution (e.g. solvent-borne paints and adhesives; solution spinning of polyacrylonitrile fibres).

Question 18

What are the disadvantages of solution polymerization?

Answer 18

• low Mw: The reduced [M] gives rise to decreases in the rate and degree of polymerization.
• Chain transfer to solvent: Furthermore,
  if the solvent is not chosen with care, chain transfer to solvent may be appreciable and can result in a major reduction in the degree of polymerization.
• Toxicity/inflam. of solvent
• Removal of solvent.
• Recycling of solvent.

Question 19

What is gas-phase polymerization?

Answer 19

It is the heterogeneous reaction between monomer gas and solid catalyst that takes place in the fluidized bed reactor to produce the polymer product.

It is restricted to about 40% conversion or too much heat will be produced.

It is only really used for the production of low-density polyethylene (LDPE) as shown in the notes

Question 20

What is heterogenous polymerization?

Answer 20

Generally, 2-phase systems in which a fine dispersion of polymer particles is formed in an immiscible liquid.

Question 21

What are the particle sizes formed from each heterogeneous polymerization technique?

Answer 21

Shown in notes.

Note that suspension polymerization forms beads big enough to hold!

Question 22

What is precipitation polymerization?

Answer 22

It is when the monomer & initiator are soluble in the continuous phase (bulk or solution); the polymer is insoluble and not swollen with monomer (or solvent).

Upon formation, the polymer precipitates as irregularly shaped particles of size: 0.1 - 10 μm. This is shown in the notes.

Due to this precipitation, the usual kinetics don’t apply.

Initiation and polymerization
take largely place in the
homogeneous medium.

Example:
“Bulk” polymerization of acrylonitrile.

Quick note: In the book it is defined as bulk polymerization under the case that the polymer isn’t soluble in the monomer. Keep that in mind for the exam!

Question 23

What is Dispersion polymerization?

Answer 23

Monomers, initiators, and stabilizers are soluble in the continuous phase. The polymer formed is insoluble causing the stabilizers to wrap around the monomers forming stabilized monomer-swollen particles. Polymerization takes place in these particles!

Question 24

What are the advantages and disadvantages of dispersion polymerization?

Answer 24

advantages:

• Forms monodisperse particles of the same same

Disadvantages:

• Not often used in the industry

Question 25

What is suspension polymerization?

Answer 25

This is essentially a bulk polymerization in which the reaction mixture is suspended as tiny droplets in an inert medium. The initiator, monomer and polymer must be insoluble in the suspension medium, which usually is water and so suspension polymerization tends to be used for monomers and polymers that have very low (or no) solubility in water

Question 26

What is the procedure that happens in suspension polymerization?

Answer 26

A solution of initiator in monomer is prepared and then added to the preheated aqueous suspension medium. Polymerization temperatures are limited by the boiling point of water and so are usually in the range 70–90 °C. Droplets of the organic phase are formed and maintained in suspension by:

1. vigorous agitation throughout the reaction, which typically is provided through use of baffled reactors with turbine stirrers, and
2. dispersion stabilizers dissolved in the aqueous phase; these typically are present at levels of 3–5wt% to monomer and usually are low molar mass water-soluble polymers, such as poly(vinyl alcohol) or hydroxyalkylcelluloses, used in combination with surfactants.

Each droplet acts as a tiny bulk
polymerization reactor for which the normal kinetics apply. The droplets are converted directly to polymer which, therefore, is produced in the form of beads
which are isolated easily by filtration or centrifugation provided that they are rigid and not tacky. Thus, the polymerization must be taken to complete conversion (to
prevent plasticization and reduction of the polymer glass transition temperature, Tg, by unreacted monomer) and normally is not used to prepare polymers that have Tgs below about 60 °C.

note: The low viscosity and high thermal conductivity of the aqueous continuous phase and the high surface area of the dispersed droplets provide for good heat transfer. Also, At high conversions, autoacceleration can occur but is much better controlled than in bulk polymerization due to the greatly improved heat dissipation.

Question 27

What are the advantages of suspension polymerization?

Answer 27

• Low viscosity
• Good heat transfer
• Products are beads
• Contaminated by low levels of the dispersion stabilizers.
• Widely used on an industrial scale

Question 28

What are the disadvantages of suspension polymerization?

Answer 28

Mostly only batch, and reactor wall fouling

Question 29

What are microporous resins?

Answer 29

They are particles made using a suspension polymerization of a crosslinking monomer + a progen (Unreactive solvent)

Question 30

What is the procedure to make macroporous resins?

Answer 30

Within the suspension polymerization, you will add an unreactive solvent forming a droplet that has the monomer and the intaitor. Now the procedure happens as follows (depicted in the notes):

The droplet containing the monomer and initiator will become a highly solvated microgel, this microgel will aggregate and polymerize, and then the polymers formed will phase separate from the monomer remaining in the solution, then once polymerization is over the solvent is removed. This forms macroporous resins

Question 31

What role does the unreactive solvent play?

Answer 31

It controls the size and the porosity of the macroporous resins. If a good solvent smooth non porous sphere with small size. Vice versa for bad solvent. This is depicted in the notes.

Question 32

What is emulsion polymerization?

Answer 32

It is where the monomer is dispersed in a non-solvent, with an initiator soluble within the solvent used (but not within the monomer) and micelle-forming surfactants.

Question 33

What is the product formed in emulsion polymerization?

Answer 33

The form of the reaction product, is a colloidally-stable dispersion of particulate polymer in water known as latex. The polymer particles generally have diameters in the range 0.1–1 μm, i.e. about three orders of magnitude smaller than for suspension polymerization

Question 34

What are the advantages and disadvantages of micelles?

Answer 34

Advantages:
- Low viscosity
- Heat transfer
- High MW,
- Direct application of latex

Disadvantages:
- Separation costs
- Surfactant
- Fouling

Question 35

What are the applications of emulsion polymerization?

Answer 35

• Medical diagnostics:
  Magnetic particles are placed within a person’s blood. The particle will stick to a specific molecule (or substance) that is required to be extruded. Then the magnetic particle is separated from the blood by a magnet. The molecule/substance can be analyzed now
• Cancer treatment:
  When the same magnetic particles are placed in a tumourous region, a magnetic can apply an oscillating frequency that causes the particle to heat up
• Paint: Latex particles
• ABS, PVC, PVAc, ABS, SAN, NBR, and coatings.

Question 36

What is the difference between suspension and emulsion polymerization?

Answer 36

Check notes.

Question 37

What are the commonly used surfactants in emulsion polymerization?

Answer 37

Anionic surfactants most commonly are used as dispersion stabilizers, typically at levels of 1–5wt% to monomer. They consist of molecules with hydrophobic hydrocarbon chains at one end of
which is a hydrophilic anionic head group and its associated counter-ion (e.g. sodium lauryl sulphate, CH3(CH2)11SO4−Na+). Due to their hydrophobic tails, they have a low molecular solubility in water and above a certain characteristic concentration, the critical micelle concentration (CMC), the surfactant molecules associate into spherical aggregates known as micelles which contain the order of 100 molecules and typically are about 5 nm in diameter. The surfactant molecules in the micelles have their hydrophilic head groups in contact with the water molecules and their hydrocarbon chains pointing inwards to form a hydrophobic core which has the ability to absorb considerable quantities of water-insoluble substances.

This is depicted in the slides shown in the notes.

Question 38

What is the situation at the beginning of emulsion?

Answer 38

The beginning of emulsion is when a water-insoluble monomer is added to an aqueous solution containing a surfactant well above its CMC and the mixture is subjected to reasonably vigorous agitation. This will result in three phases:

(i) the aqueous phase in which small quantities of surfactant and monomer are molecularly dissolved;

(ii) large (about 1–10 μm diameter) droplets of monomer maintained in suspension
by adsorbed surfactant molecules and agitation; and

(iii) small (about 5–10 nm diameter) monomer-swollen micelles which are far greater in number (1018–1021 dm−3) than the monomer droplets (1012–1015 dm−3) but contain a relatively small amount of the total monomer.

note that the aqueous phase also contains the initiator which usually is either a persulphate or a redox system. This whole situation is depicted in Figure 4.8 in the notes.

Also, some typical initiators are shown in notes.

Question 39

What are the typical monomers used in emulsion?

Answer 39

Shown in notes

Question 40

What are the 3 intervals of emulsion?

Answer 40

Interval I - Particle Nucleation

Intervals II and III - Particle Growth

Shown in notes

Question 41

What is particle nucleation?

Answer 41

Particle nucleation is the first stage of emulsion polymerization and is known as Interval 1. There are several mechanisms by which particles can be formed (listed in the next flash card). Whilst they can all contribute to particle nucleation, usually one mechanism predominates depending on the monomer used and the precise conditions of polymerization.

In all cases, the primary free radicals formed from the initiator react with molecules of monomer dissolved in the aqueous phase to produce oligomeric radical species that continue to propagate in the aqueous phase. These oligomeric radicals have several possible fates. They may terminate in the aqueous phase to produce species that are surfactant-like (because the oligomeric chain is hydrophobic and the initiator end-group is hydrophilic), or they may continue to propagate until they reach a critical degree of polymerization z at which they become surface active, or can grow still further until they reach another critical degree of polymerization j at which they become insoluble in the aqueous phase and precipitate from it.

Question 42

What are the different particle nucleation mechanisms?

Answer 42

1. Micellar nucleation
2. homogeneous nucleation
3. Coagulative nucleation
4. Droplet nucelation

Question 43

What is the micellar nucleation mechanism?

Answer 43

Micellar nucleation, proposed by Harkins, happens when oligomeric radicals (small polymer chains) enter and diffuse into monomer-swollen micelles (small surfactant clusters), starting polymerization. It’s unlikely for radicals to enter monomer droplets because micelles have a much larger surface area and are better at capturing radicals. When a micelle captures a radical, it becomes a particle nucleus, where polymerization continues by absorbing monomer from the surrounding water. The monomer moves from droplets to water to maintain balance. These growing particles outgrow the original micelles, and additional surfactant adsorbs onto the particles to stabilize them. This extra surfactant comes from micelles that didn’t initiate polymerization. As the reaction proceeds, micelles are eventually depleted, marking the end of particle nucleation. Micellar nucleation only occurs when surfactant concentration is above the critical micelle concentration (CMC) and is more common with hydrophobic monomers like styrene or n-butyl acrylate, which have low water solubility.

Question 44

What is homogenous nucleation mechanism?

Answer 44

For monomers with higher solubilities in water (e.g. MMA, methyl acrylate and vinyl acetate), homogeneous nucleation is important and can be dominant. In this mechanism, an oligomeric radical continues to propagate in solution in the aqueous phase (i.e. homogeneously) until it becomes a j-mer, at which point the chain radical collapses and becomes a primary particle whilst retaining the radical site at its chain end. The other end group derived from the initiator (e.g. SO4− from
persulphate) provides some colloidal stability but not sufficient; hence the primary particles adsorb surfactant to achieve colloidal stability and absorb monomer so that the chain radical can continue to propagate. Provided that this happens, each primary particle becomes a latex particle. Nucleation ceases when the number of already-formed particles is high enough to ensure that they capture all
oligomeric radicals

Question 45

What is the coagulative nucleation mechanism?

Answer 45

Coagulative nucleation is most easily understood as an extension of homogenous nucleation in which the primary particles coagulate with each other until the aggregate particle attains a size at
which it becomes colloidally stable and can absorb appreciable quantities of monomer. These aggregate particles are the latex particles that grow in Intervals II and III.

Question 46

What is the droplet nucleation mechanism?

Answer 46

When the radical enters the monomer droplet. Very hardly happens. Never is a dominant mechanism. but it’s okay it can be a power bottom.

Question 47

A final note about nucleation mechanisms?

Answer 47

Each of these particle nucleation mechanisms can contribute in most emulsion polymerizations, as summarized in Figure 4.9. However, when the surfactant concentration is below the CMC, only
the homogeneous and coagulative mechanisms are possible. If the surfactant concentration is very low, coagulative nucleation will be dominant.

Question 48

What is particle growth (Intervals II and III)?

Answer 48

Provided that the particles remain colloidally stable, the number Np of particles per unit volume of latex (typically 10^16–10^18 particles dm^−3) remains constant after the end of Interval I.

Polymerization within these particles continues, supported by diffusion of monomer through the aqueous phase
from the monomer droplets, as described above. Thus, the monomer droplets have only one function, which is to serve as reservoirs of monomer. The rate of monomer diffusion exceeds the rate of
polymerization so that the concentration [M]p of monomer within a particle remains constant. Since Np is constant, the rate of polymerization also is constant; this period of polymerization is known as Interval II. Eventually, the monomer droplets are exhausted, marking the end of the period of constant rate. Thereafter, in Interval III, [M]p and the rate of polymerization decreases continuously as the remaining monomer present in the particles is polymerized. The three intervals of emulsion polymerization are identified in the schematic conversion-time curve shown in Figure 4.10.

Support from the slides is also shown in notes (read the writing under the graph)

Question 49

Flashcard 50 likeeee

Answer 49

Although Equation 4.36 is applicable to all stages in emulsion polymerization, full theoretical treatment is complex because of the need to derive equations for Np and nˉ in terms of experimentally accessible
quantities. This is non-trivial because both Np and nˉ are determined by balances between several competing processes and the reaction mechanism usually is much more complex than indicated in this basic introduction to emulsion polymerization.

For example, chain transfer agents often are used to reduce xˉn, small radical species (e.g. product radicals from chain transfer events) can desorb from the particles, and small amounts of water-soluble comonomers are often included.

Only the simplest situation will be considered here (known as Smith–Ewart Case 2 conditions)

Question 49

What is the rate of polymerization per unit volume of latex in emulsion polymerization?

Answer 49

Check written notes

Question 50

What are the Smith–Ewart Case 2 conditions?

Answer 50

A case for which it is assumed that radical desorption from particles does not occur and that the particles are so small that two radical species can exist independently within a particle only for very short periods of time before reacting together. Under these conditions, a radical cannot escape the particle once captured and termination can be considered to occur immediately upon entry of a second radical species into a particle that already contains one propagating chain radical. The particle then
remains dormant until entry of another radical initiates the propagation of a new chain.

Therefore, on average, each particle contains one propagating chain radical for half the time of its existence and none for the remaining half Under these conditions, nˉ=1/2 and the rate reduces to (shown in written notes)

Support from the slides to understand this is also shown in digital notes

Question 51

Flashcard 52 likeee

Answer 51

The two equations are known as the Smith−Ewart ‘Case 2’ Equations and are best applied to Interval II when [M]p and Np are constant. They show that both Rp and xˉn can be increased. by increasing Np (e.g. by using a higher concentration of surfactant), i.e. high molar mass polymer
can be formed at high rates of polymerization without compromise, unlike in bulk and suspension polymerization processes (see Section This is because simultaneously propagating chain
radicals are segregated into separate particles and cannot react with each other. Hence the isolation of individual propagating chains into separate particles, termed compartmentalization, is the key
reason for the unique kinetics of emulsion polymerization!

This is depicted in notes

Question 52

What are the benefits and applications of emulsion polymerization? (part 2 ig recap + extra stuff)

Answer 52

Further important features of emulsion polymerization are the excellent heat transfer, the relatively low viscosity of the product latexes at high polymer concentrations, and the ability to control particle morphology (e.g. formation of core-shell particle structures by successive additions of different monomers). Additionally, due to the increasingly stringent environmental legislation on emission of volatile organic compounds (VOCs), water-borne polymers (i.e. latexes) prepared by emulsion polymerization are growing in importance as environmentally friendly alternatives to solvent-borne
polymers, especially for coating applications.

Polymers prepared by emulsion polymerization are used either directly in latex form (e.g. emulsion paints, water-borne adhesives, paper coatings, binders for non-woven fabrics, foamed
carpet-backings) or after isolation by coagulation or spray drying of the latex (e.g. synthetic rubbers and thermoplastics). In this respect, contamination by inorganic salts and dispersion stabilizers is
often the most significant problem.

Question 53

What is miniemulsion polymerization?

Answer 53

Miniemulsion polymerization was developed from emulsion polymerization with the objective of controlling Np by starting the polymerization with a miniemulsion that comprises monomer
droplets which are sufficiently small (typically 50–300 nm diameter) and large enough in number (1016–1018 dm−3) to capture efficiently all radicals. The locus for particle nucleation is then the miniemulsion monomer droplets, each of which (ideally) becomes a polymer particle, and so Np is defined by the number of miniemulsion droplets Nd present at the start of the polymerization. Once polymer has been formed within a miniemulsion droplet, it becomes a monomer-swollen particle and polymerization continues in much the same way as during Interval III of an emulsion polymerization.

Question 54

How can you produce miniemulsions?

Answer 54

To create miniemulsions, you need a two-part stabilizer system: a surfactant and a costabilizer (a substance soluble in the monomer but insoluble in water, like hexadecane). First, a coarse mixture (macroemulsion) of monomer and costabilizer in water is made. Then, high shear forces (like ultrasonication or homogenization) break it into tiny droplets, forming the miniemulsion. The surfactant stabilizes these small droplets, using most of it up, leaving few or no micelles. The costabilizer stops the monomer from diffusing out of the droplets, preventing them from reforming into larger droplets (macroemulsion). It’s usually added in small amounts (1-4% of monomer) and can be a low molecular weight polymer for better droplet nucleation efficiency.

Question 55

What are the other advantages of miniemulsions?

Answer 55

Miniemulsion polymerization was developed to better control the number of polymer particles (Np), but it has other benefits. Since there’s no need for monomer transport through water and the droplets act as tiny reactors, it can be used for more than just making latex (like in traditional emulsion polymerization). You can also use miniemulsions to produce latex from monomers that are insoluble in water or create hybrid particles by mixing in additives (like polymers, resins, or pigments) that get incorporated into the final particles. Additionally, you can make latexes of different polymer types, like epoxy resin latexes, by polymerizing inside the droplets.

Question 56

What are microgels?

Answer 56

Microgels are tiny crosslinked polymer particles made through emulsion copolymerization of mono- and multi-functional monomers. These particles form network polymers that don’t dissolve in water during polymerization but can mix with water under different conditions. Typically, the polymerization happens at temperatures above the lower critical solution temperature (LCST). When the latex is cooled below the LCST, the microgels absorb water and swell, but they don’t dissolve due to the crosslinks. Microgel latexes are especially useful in biomedical applications, like diagnostics and controlled drug release, because of their ability to swell and shrink.

Question 57

What are the three generic strategies for carrying out a polymerization process?

Answer 57

1. Batch: All reactants are added completely to the reaction vessel at the start of the
   polymerization.
2. Semi-continuous batch (or semi-batch): Only part of the total reaction formulation is introduced at the beginning of the reaction, the remainder being added according to a predetermined schedule during the course of the polymerization.
3. Continuous: Reactants are added continuously to the reactor from which product is removed continuously such that there is a balance between the input and output streams.

Question 58

What is the comparison between these processes?

Answer 58

Batch processes are of limited versatility for manufacture of polymers by free-radical polymerization and mainly find use in academic studies and simple evaluations of reaction formulations. By comparison, semi-batch processes are very versatile and are widely used, both industrially and in
academic laboratories. Continuous processes tend to be used when very large volumes of a specific polymer needs to be manufactured, but (unlike semi-batch reactors) are not easily switched from
production of one polymer to another.