Methyl methacrylate reaction rate data

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. 

Kochi (1956a, 1956b) and Dickerman et al. (1958, 1959) studied the kinetics of the Meerwein reaction of arenediazonium salts with acrylonitrile, styrene, and other alkenes, based on initial studies on the Sandmeyer reaction. The reactions were found to be first-order in diazonium ion and in cuprous ion. The relative rates of the addition to four alkenes (acrylonitrile, styrene, methyl acrylate, and methyl methacrylate) vary by a factor of only 1.55 (Dickerman et al., 1959). This result indicates that the aryl radical has a low selectivity. The kinetic data are consistent with the mechanism of Schemes 10-52 to 10-56, 10-58 and 10-59. This mechanism was strongly corroborated by Galli s work on the Sandmeyer reaction more than twenty years later (1981-89). 

Additional data were obtained from the study of kinetics of the slow disproportionation of the living dimers of methyl methacrylate. The progress of this reaction is shown in Fig. 8 which displays also the respective rates and equilibrium constants. 

A more conventional mechanism appears to be operative in the photopolymerization of ethyl acrylate [178] and methyl methacrylate [179] in aqueous solution, sensitized by fluorescein and Erythrosin, respectively. Ascorbic acid is the reducing agent in both cases and it is observed that the reaction does not proceed in the absence of buffer, usually phosphate buffer pH 6. Polymer formation starts after an induction period but its dependence on light intensity and ascorbic acid concentration has not been determined. The rate of photopolymerization is proportional to the monomer concentration and to the square root of the light intensity, dye, and ascorbic acid concentration. The authors report the order with respect to the monomer as 3/2. However, from our analysis of the data for fluorescein, which are more... 

There is further evidence that radical termination reactions are diffusion-controlled. For many polymers, the rate of polymerization shows a sudden increase when the fraction of polymer produced reaches values near 15 to 30 per cent. In the case of methyl methacrylate, Matheson et al. found that, at 30 C and 15 per cent conversion, kt has decreased 160 fold, while kp has not changed appreciably. Vaughan " has proposed a simple diffusion model which is in reasonable accord with the data on styrene polymerization at high conversions. 

More satisfactory data have been obtained for methyl methacrylate polymerization using soluble allylic compounds such as Cr(7r-C3115)3 or Cr(7r-2Me—C3 H4 )3 [229]. With these catalysts the rate relationship in the early stages of reaction is... 

In order to obtain data for the hydrolysis as well as condensation rates of the monomers 3a and 3e incorporated in polymers, copolymers of 0.5 mol% silane with methyl methacrylate have been synthesized in methyl ethyl ketone (30% solids content). Catalyzing the crosslinking reaction with an aq. Me4NOH-solution, it turned out that PMMA-3a copolymer needed only 13 min to solidify, whereas 95 min were necessary for a PMMA-3e copolymer (0.5 mol% 3e) to become a gel. 

Most recently the polymerization of methyl methacrylate with Ba counterion has been reported. In THF at —70 °C the rate constant for propagation is independent of the active centre concentration and growth seems to occur via ion pair species only. The kinetic data obtained compare favourably with those for polymethylmethacryl sodium and caesium.As before, active centres are terminated by side-reactions involving the ester group. 

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 ]... 

The effect of a, a -azobisisobutyronitrile initiator concentration [1] on the rate of polymerization of methyl methacrylate at 50°C has been stndied by Arnett (1952). Use the following data to show that the termination reaction is second order with respect to the growing chains and initiation is first order with respect to the initiator concentration. ... 

Figure 2 shows the propagation rate constant of the copolymerization of methyl methacrylate (MMA) and STY as a function of the fraction of MMA in the reaction mixture. The experimental data have been determined via pulsed laser polymerization (PLP), which is known to be the most reliable method to measure propagation rate constants. The two curves are based on the implicit PUM and the TM. It is clear that the TM fails completely to describe kp versus feed composition. Contrarily, the implicit PUM provides a very satisfactory description of the experimental data. 

Empirical rate equations have been reported for the mastication degradation of many polymers, for example, polyethylene [29], poly(methyl methacrylate) [30], styrene rubbers [31, 32], polychloroprene [33], and EPDM [34]. Reaction rate generally depends on [35]. Experiments on degradation rate have been performed also on the molten state [15, 16, 35]. Pohl and co-workers [15, 16] reported their data as the fraction of bonds broken (Eq. 2.17) as a function of capillary residence time. They found that the average rate of bond breaking b depends on shear rate y and absolute temperature T by the following equation for polyisobutylene ... 

According to the authors, many literature data agree with this expression. As the rate equation is second order with a limit Ainu not first order in molecular weight, they consider that chain scission is related to the chain length of adjacent polymer molecules. The same equation was applied by Fujii [30] to mastication of poly(methyl methacrylate). For poly(vinyl chloride) the exponent was 1 instead of 2, indicating a first-order reaction. 

Problem 6-16 (Level 2) The kinetics of the polymerization of methyl methacrylate monomer were studied at 77 °C using benzene as a solvent and azo-bisisobutyronitrile (AIBN) as the free radical initiator. The following table contains some data from an ideal batch reactor that shows the initial rate of reaction as a function of the initial concentration of monomer M and the initial concentration of initiator I. 

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