Bulk polymerization of methyl methacrylate

Bulk Polymerization. This is the method of choice for the manufacture of poly(methyl methacrylate) sheets, rods, and tubes, and molding and extmsion compounds. In methyl methacrylate bulk polymerization, an auto acceleration is observed beginning at 20—50% conversion. At this point, there is also a corresponding increase in the molecular weight of the polymer formed. This acceleration, which continues up to high conversion, is known as the Trommsdorff effect, and is attributed to the increase in viscosity of the mixture to such an extent that the diffusion rate, and therefore the termination reaction of the growing radicals, is reduced. This reduced termination rate ultimately results in a polymerization rate that is limited only by the diffusion rate of the monomer. Detailed kinetic data on the bulk polymerization of methyl methacrylate can be found in Reference 42. 

A valid kinetic model of stage 3 emulsion polymerization must account for diffusion-controlled termination and propagation reactions. Marten and Hamielec (J) have proposed such a model based on a free-volune theory and have confirmed its validity for the bulk polymerization of methyl methacrylate (7). Herein is reported an evaluation of this model for the emulsion... 

Figure 1. Conversion histories in bulk polymerization of methyl methacrylate, styrene, and vinyl acetate...

Problem 6.43 The bulk polymerization of methyl methacrylate (density 0.94 g/cm ) was carried out at 60°C with 0.0398 M benzoyl peroxide initiator [64]. The reaction showed first order kinetics over the first 10-15% reaction and the initial rate of polymerization was determined to be 3.93x10 mol/L-s. From the GPC molecular weight distribution curve reported for a 3% conversion sample, the weight fraction of polymer of DP = 3000 is seen to be 1.7x10 . Calculate the weight fraction from Eq. (6.217) to compare with this value. [Use the following data Cj 0.02 Cm = 10- fk = 2.7 x 10 s kt = 2.55x10 L/mol-s fraction of termination by disproportionation = 0.85 ]... 

In the bulk polymerization of methyl methacrylate at 60°C with azo-bis-isobutyronitrile as the initiator the initial rates of initiation and polymerization are 1.7x10 mol/L-s and 8.8x10 mol/L-s, respectively. Predict the initial molecular weight of the polymer formed in this system, if the extent of disproportionation is 70% at 60°C. Neglect chain transfer reactions for the calculation. 

Problem 7.20 Bulk polymerization of methyl methacrylate (MMA) at 60°C with 0.9 g/L of benzoyl peroxide yielded a polymer with a weight average degree of polymerization of 8600 at low conversions. Predict the conversions of MMA at which gelation would be observed if it is copolymerized with 0.05 mol% of ethylene glycol dimethaciylate (EGDMA) at the same temperature and initiator concentration as in the homopolymerization case. 

Norrish et al.18 discovered the acceleration effect in the polymerization of methyl methacrylate in 1939. In order to elucidate the cause of the effect, polymerization rates for methyl methacrylate were determined in various kinds of solvents. Schulz et al.19,20 reported that acceleration occurred at about 12% and 25% conversion in the bulk polymerization of methyl methacrylate at 50 and 70 °C, respectively, while there was no effect observed up to high conversion with styrene. Tromms-dorff et al.21 showed that this phenomenon is due to the increased viscosity of the polymerization system which is not caused by the interaction between a propagating radical and solvent. In order to investigate how the variation of the viscosity of... 

Because of the above heat transfer problems, bulk polymerization of vir l monomers is restricted to those with relatively low reactivities and enthalpies of polymerization. This is exemplified by the homogeneous bulk polymerization of methyl methacrylate and styrene (Table 10.1). Some polyurethanes and polyesters are examples of step-reaction polymers that can be produced by homogeneous bulk polymerizations. The products of these reactions might be a solid, as in the case with acryhc polymers a melt, as produced by some continuous polymerization of styrene or a solution of polymer in monomer, as with certain aUcyd-type polyesters. 

For the bulk polymerization of methyl methacrylate at 77°C with azo-bis-isobutyronitrile as the initiator, the initial rate of polymerization was 1.94 x 10 mol/l-s. The concentrations of the monomer and initiator were 9 mo 1/1 and 2.35x10 mol/1, respectively. To reduce the heat transfer problems, the polymerization was repeated in a solution of benzene by the addition of 4.5 1 of benzene with an initiator concentration of 2.11 X 10 1/mol. Assuming that the rate constants are the same for both the bulk and solution polymerizations, calculate the rate of solution polymerization of methyl methacrylate. If there is no transfer to the solvent and the initial rate of initiation is 4 x 10 mol/l-s, what is the ratio of the number-average degree of polymerization for bulk-to-solution polymerization Comment on your results. 

Poly (methyl methacrylate) for molding or extrusion is produced commercially by fiee-radical-initiated suspension or bulk polymerization of methyl methacrylate. To minimize polymerization reaction exotherm and shrinkage, bulk polymerization, which is used in the production of sheets, rods and tubes, is carried out with a reactive syrup of partially polymerized methyl methacrylate, which has a viscosity... 

Georgiev has reported a photoiniferter ability for [bis(acyloxy)iodo]arenes during the bulk polymerization of methyl methacrylate, styrene and A-vinylpyrrolidone [44]. The term photoiniferter refers to a chemical compound that has a combined function of being a free radical initiator, transfer agent and terminator in photolytically induced polymerization [47]. Under visible light [bis(acyloxy)iodo]arenes initiate... 

Good agreement between the predicted rate from Equation 3.17 and the experimental values obtained for the bulk polymerization of methyl methacrylate has been reported. 

As expected for CLIP, the ratio (kp)/ (kt) (and hence the rate) decreases with decreasing DP (kt) increases with decreasing DPa, while kp remains constant. For CLDP we see a positive deviation from the CLIP situation, because the effect of an increasing value of (kt) is compensated by an increasing value of (kp) with decreasing DPp. This effect becomes more pronounced with increasing values of im and Ci. It should also be noted here that this behaviour was observed experimentally for the low-conversion bulk polymerization of methyl methacrylate at 60 °C in the presence of dodecanethiol. ... 

At high conversion, the growth of viscosity hinders the termination by radical-radical reactions, but it has less effect on the propagation reaction, because diffusion of small monomer molecules is not so much affected by viscosity. Hence, both the rate of polymerization and the molecular weight of the polymer show an increase, there is auto acceleration at high conversion. This effect is known as gel-effect or Tommsdorf-effect, which is usually accompanied by a sudden rise of temperature (Swallow 1973). Such effect was observed in many systems, for instance in the y-ray induced steady-state bulk polymerization of methyl methacrylate (Luthjens et al. 2001). 

Using variable power of microwave irradiation, Boey et al. showed that bulk polymerization of methyl methacrylate (MMA) was faster by ca. 130-150% compared with the conventional methods (Fig. 4) [35]. Also, the limiting conversion... 

In the bulk polymerization of methyl methacrylate (MMA), the Trommsdorff effect sets in after an unperturbed period of about 15-20 % conversion. This enables a separation to be made between unperturbed and autoaccelerated kinetics. Benson and North, O Driscoll, Ito and others have attempted to describe the kinetics of autoacceleration or gelation by introducing a chain-length-dependent value of the termination rate constant... 

Ross, R.T. Laurence, R.L. (1976) Gel effect and free volume in the bulk polymerization of methyl methacrylate. AIChE Symposium Series, 72, 74—79. 

Radical polymerization is initiated by a free radical, which subsequently adds to a vinyl or diene monomer to produce a propagating radical. To obtain information about the structure and concentrations of initiating and propagating radicals in radical polymerizations, use of ESR spectroscopy has called the interest of physical or polymer chemists. However, ESR measurements on these radicals in solution poly merizati on were found to be difficult, except for the case where polymers precipitated, because otherwise the concentrations of the radicals were too low. Thus, these measurements had to be limited to polymerization systems in highly viscous solutions or in the solid state, where the disappearance of free radicals by bimolecular reactions is suppressed. Bresler et al. -i7) succeeded for the first time in obtaining ESR spectra of free radicals which were produced in homogeneous bulk polymerization of methyl methacrylate (MMA), methyl acrylate (MA) and vinyl acetate (VAc) at conversions of 50-60% (in the gel state). 

The calculated values of agreed well with the limiting convorsion values for bulk polymerization of methyl methacrylate estimated by isothermal differential scanning calcainKtry (DSQ and gravimetry The theory can be ap(Aed not only to radical... 

Bulk polymerization of methyl methacrylate at 22.5°C with AIBN as initiator [8]. 

Kinetic studies of the solution (benzene) and bulk polymerization of methyl methacrylate with MA have been run at 60°C and 70°C, using AIBN initiator. The microstructure of the purified copolymers was determined by H-NMR and IR spectroscopy. Analysis of the comonomer pair sequence distribution for the solution-prepared copolymers supported a copolymerization mechanism involving participation of an association species between the two monomers. A terminal model or the classical Mayo-Lewis concept more adequately explained the results of bulk copolymerization, where the comonomer sequence distribution was more random. Theoretically, the concentration of associating species should be greatest in bulk, which was... 

The curing reaction of unsaturated polyester resin involves the copolymerization of unsaturated polyester and styrene in the presence of an organic initiator. Like any other free-radical polymerization (e.g., bulk polymerization of methyl methacrylate), the organic initiator first decomposes to form an initiator radical [/ ], which will then react with unsaturated polyester to form a polyester radical [ ] and with styrene monomer to form a styrene radical [S ]. Therefore, the curing reaction can be treated by a free-radical polymerization approach. Below, we describe briefly the mechanistic kinetic model for unsaturated polyester (Han and Lee 1987a, 1987b Stevenson 1986). 

Recently, Abuin et al. [96] investigated the kinetic features of bulk polymerization of methyl methacrylate using triethyl boron (TEB)-di-ter -butylperoxide mixture as the radical initiator. From their data, it can be seen that, working at a constant di-rerr-butylperoxide concentration, the reaction rate increases as the TEB concentration increases, reaching a maximum and then decreasing with further TEB addition. If the TEB only modifies the initiation rate, a simple free-radical mechanism would predict that at a given temperature, the following equation should hold true ... 

Abuin et al. [96] also reported the bulk polymerization of methyl methacrylate at 20°C using triethylboron-di-t-butylperoxide at various triethylboron concentration. The amount of polymer produced was proportional to the reaction time. The results are presented in Table 11. 

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