Find materials for this course in the pages linked along the left. In the following paragraphs the chain mechanism of the bulk free radical polymerization will be. Difficult to remove solvent from final form, causing degradation of bulk properties. Anshuman shrivastava, in introduction to plastics engineering, 2018. Polymerization on an industrial scale is conducted using five basic methods. This in turn lowers the effective termination rate k. The polymerization of methyl methacrylate, for example, deviates strongly from classical mechanism behavior around 20% conversion. Autoacceleration in bulk freeradical polymerization. Autoacceleration of the overall rate of a free radical polymerization system has been noted in many bulk polymerization systems. Weakly nonlinear analysis is applied to investigate pulsating instabilities in two dimensions. It is used for most stepgrowth polymers and many types of chaingrowth polymers.
In solution polymerization, or for polymerizations carried out in the presence of chain transfer agents, the duration of the lowconversion regime is extended and the very highconversion regime may not occur. The polymerization conforms to the fixed shape of the reaction vessel when solidification occurs. Converting monomer to long chain polymer is the final step in the polymer manufacturing sequence. Bulk polymerization or mass polymerization is carried out by adding a soluble initiator to a pure monomer in liquid state. Study of the isothermal bulk polymerization of methacrylic acid and. Initiator concentration dependence of the autoacceleration. The increase in polymerization rate and molecular weight of certain vinyl monomers during bulk polymerization explanation of autoacceleration. Solvent reduces viscosity, making processing easier. Experimental data of styrene conversion dependence on reaction time were well described by estimated kinetic model. Autoacceleration article about autoacceleration by the free dictionary. Autoacceleration of the overall rate of a freeradical polymerization system has been noted in many bulk polymerization systems.
The freeradical bulk polymerization of many monomers is characterized. Texas tech university, haoyu zhao, december 2014 ii acknowledgments. A freeboundary model is used to describe frontal polymerization. Pdf nonlinear dynamics of frontal polymerization with. Principles of polymerization third edition george odian the college of staten island. Polymerization is a reaction process in which two or more monomers are bonded chemically to form large polymer chains or threedimensional networks. Reversible additionfragmentation chaintransfer polymerization for the synthesis of poly4acetoxystyrene and poly4acetoxystyreneblockpolystyrene by bulk, solution and emulsion techniques subbareddy kanagasabapathy,a arumugam sudalai, brian c. Especially the termination rate constant can be strongly in. Chemical engineering 160260 polymer science and engineering lecture 6 mechanism and kinetics of free radical chain polymerization january 29, 2001. Request pdf autoacceleration in bulk freeradical polymerization.
As a consequence an autoacceleration period, the so. The freeradical bulk polymerization of many monomers is characterized by a sudden rise in the rate of polymerization, a phenomenon called autoacceleration. Bulk polymerization an overview sciencedirect topics. Chain transfer to solvent occurs, leading to low molecular weights. Although we have considered this slowly evolving polymer in terms of the extent of reaction, another question starts to be worrisome. Kinetic modeling of bulk freeradical polymerization of. Consider the polymerization of mma at low concentrations, % conversion as a function of time follows the expected path. G polymerization methods authorstream presentation. Tromsdorff effect or autoacceleration autoacceleration usually occurs in radical chain polymerizations and normally in bulk polymerization. Modeling insight into the diffusionlimited cause of the gel effect in free radical polymerization. Model development and parameter estimation for styrene. Bulk polymerization, which may also be referred to as mass polymerization, involves a monomer and an initiator as the main components, without a solvent.
In bulk polymerization, the initiator is mixed with pure monomer. Abstract the model and methodology for estimating diffusion. Radical polymerization bulk polymerization of s and mma, 1 is typically 20%, 2 is 2085%, and 3 is 85%. Another example of bulk or melt polymerization is the synthesis of polyamides through the direct interaction between a dicarboxylic acid and a diamine. In highconversion atom transfer radical polymerization atrp, all the. Effect of chain transfer the model and methodology for estimating diffusioncontrolled. A new approach for the kinetic modeling of free radical.
Read sensitivity analysis of a batch polymerization reactor, journal of applied polymer science on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Graphenebased electrochemical sensors for biomolecules, 2019. Diffusion of single molecular and macromolecular probes. A semiempirical breakpoint treatment of diffusion control on. It is well known that the free radical bulk polymerization of styrene is characterized by autoacceleration phenomenon after a definite conversion of the monomer. The reaction is initiated by heating or exposure to radiation. Nonlinear dynamics of frontal polymerization with autoacceleration. Control of exothermic reactions is crucial for preventing runaway reactionsexplosions in the. David victoriavalenzuela, jorge herreraordonez, cristy l.
The reaction is initiated by heating or exposing to radiation. An arrehnius plot for the effective rate constant prior to autoacceleration for bulk and nanoconfined samples. Autoacceleration article about autoacceleration by the. In our previous study, the bulk atrp of methyl methacrylate mma was. Autoacceleration is a dangerous reaction behavior that can occur in freeradical polymerization. Nonlinear dynamics of frontal polymerization 61 with an increase in the degree of conversion. The influence of oxide nanoparticles on the kinetics of free radical methyl methacrylate polymerization in bulk. Bulk polymerization of ndodecyl methacrylate initiated by 2,2. The absence of solvent makes it too difficult to control the temperature and viscosity of the polymerization medium due to high amount of evolved heat and high molecular weight caused by the accelerated exothermic polymerization reaction. Techniques of polymerization in engineering chemistry. Addition polymerization of alkenes is an exothermic process due to the relief of the bond strain from cc double bonds. Free radical bulk polymerizations exhibit complex kinetics due to the viscosity increase during the polymerization process. A new kinetic model of styrenefree radical bulk polymerization was developed. Sensitivity analysis of a batch polymerization reactor.
Effect of azo and peroxide initiators on a kinetic study. Read initiator concentration dependence of the autoacceleration of polymerization rate, journal of polymer science in two sections on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Bulk polymerization is carried out in the absence of any solvent or dispersant and is thus the simplest in terms of formulation. The real challenge concerns the dissipation of the heat produced by polymerization. In freeradical polymerizations, an autoacceleration of polymerization rate is typically observed when the monomer. Pdf modelling of free radical bulk polymerization o styrene. Polymerization is usually highly favourable in thermodynamic terms, mainly on energetic grounds because ordering molecules into linked chains is a process where the entropy is decreased. Similar autoacceleration was not observed for monomers yielding pel with charge spacing of. The mechanism of the explosive polymerization of methyl.
Chemistry of industrial polymers stepgrowth polymerization. The trommsdorff effect under shear and bulk polymerization of methyl. Especially the termination rate constant can be strongly influenced by the mobility of polymer chains in the polymerization mixture. In the following paragraphs the chain mechanism of the bulk free radical polymerization will be described in detail, a kinetic model will be presented and an expression for the rate of polymerization will be derived. Chapter two, stepgrowth polymerization, version of 1505 80 by line 5, the reaction has reached 80% completion and the number average value of the degree of polymerization nn is 5. On the other hand, it is not possible to state categorically that a specific suspension polymerization reaction follows the same conversion profile that was determined for a bulk polymerization.
302 267 198 724 628 424 347 351 247 108 108 694 353 1391 1525 222 927 9 1238 460 1110 158 1019 1127 366 62 988 55 1418 400 142 317 607 709 916 1187 1482 492 201 445 179 949 922 324 1401 918