Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene. VI. Effects of pressure and temperature

In a radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene, the effects of pressure and temperature were investigated in the range of 0–40 kg/cm² and 7–53°C at emulsifier concentration of 0.5 and 2.0%. Both the polymerization rate and the molecular weight of copolymer increase with increasing pressure and decreasing temperature. These facts are mainly due to an increase of the monomer concentration in the polymer particles. The rate of polymer chain formation was found to be independent of pressure and temperature. The initiation reaction is due mainly to the entry of radicals generated in the aqueous phase into the polymer particles. The apparent activation energy is ?2.0 to ?3.8 kcal/mole for the polymerization in the presence of 0.5% emulsifier, but is nearly zero at an emulsifier concentration of 2.0%. This difference in apparent activation energies at emulsifier concentrations of 0.5 and 2.0% is explained in terms of the termination mechanisms.     

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene. IV. Effects of emulsifier concentration and dose rate

Radiation-induced emulsion copolymerization of tetrafluoroethylene with propylene was carried out by batch operation with an initial molar ratio of tetrafluoroethylene to propylene of 3.0 in the emulsifier concentration range of 0.1 to 3.0% and in the dose rate range of 2 × 10⁴ to 2 × 10⁵ R/hr. The effects of emulsifier concentration and dose rate on the polymerization rate and the number-average degree of polymerization are discussed in comparison with the Smith-Ewart theory. The polymerization rate is proportional to the 0.26 power of emulsifier concentration and to the 0.7 power of dose rate. The degree of polymerization is independent of the emulsifier concentration and the dose rate above the critical micelle concentration (CMC) of the emulsifier. These results are not in agreement with the Smith-Ewart theory. It is explained that the termination reaction is a degradative chain transfer of propagating radicals to propylene. On the other hand, the copolymerization in emulsion occurs either below the CMC or in the absence of emulsifier. Under these conditions, however, it is impossible to obtain a copolymer of high molecular weight at a high rate of polymerization because of the presence of a small number of polymer particles formed and the short interval of chain growth in the polymer particle.     

Emulsion copolymerization of tetrafluoroethylene and propylene with redox system containing tert-butylperbenzoate. II. Polymerization mechanism

Emulsion copolymerization of tetrafluoroethylene (TFE) and propylene (P) initiated by trilon-rongalite catalytic system containing tert-C₄H₉OH, initial monomer mixture, emulsifier (C₇F₁₅COONH₄) concentration, and monomer mixture/water ratio on the polymerization rate (R) and molecular weight (M?_n ) was investigated. Both R and M?_n increased considerably with TFE content in monomer mixture up to 75 mol %. Alternating rubber-like copolymers in a wide range of initial monomer mixture (from 55–85 mol %) were obtained. The reactivity ratio was found to be r_TFE = 0.005 ± 0.04 and r_p = 0.17 ± 0.07. Above the critical miscelle concentration, the effects of the initiating system Is and emulsifier Cs on R and M?_n were found to obey the following relations: according to which emulsion copolymerization proceeds by the I case of Smith-Ewart theory. Polymerization mechanism of the reaction studied was suggested. The copolymerization is mainly terminated by degradative chain transfer of the propagating radicals to propylene. © 1994 John Wiley & Sons, Inc.     

H2O2-photosensitized emulsion copolymerization of tetrafluoroethylene with propylene

The H₂O₂-photosensitized emulsion copolymerization of tetrafluoroethylene with propylene was carried out at room temperature in the presence of gaseous monomers of 50 mole-% tetrafluoroethylene content. The conversion increased almost linearly with irradiation time. The rate of polymerization was proportional to the 1.0 power of H₂O₂ concentration up to 3.5 × 10^?3M H₂O₂ and the 0.46 power of H₂O₂ concentration above 3.5 × 10^?3M H₂O₂. The result obtained at low H₂O₂ concentration was almost consistent with that obtained in the radiation-induced method. The rate of polymerization was proportional to the 0.58 power of the emulsifier concentration, and the degree of polymerization was independent of the emulsifier concentration. The H₂O₂-photosensitized emulsion copolymerization of tetrafluoroethylene with propylene is terminated mainly by degradative chain transfer of the propagating radical to propylene at low H₂O₂ concentration and by the reaction of the propagating radical with OH radical from photolysis of H₂O₂–aqueous solution at high H₂O₂ concentration.     

Radiation-induced copolymerization of tetrafluoroethylene with vinyl ethers

Radiation-induced copolymerization of tetrafluoroethylene with various vinyl ethers has been studied. It was found that tetrafluoroethylene can be copolymerized with vinyl ethers to give alternating copolymers over a wide range of the initial monomer concentration in the monomer mixture. The monomer reactivity ratios were determined for the copolymerization of tetrafluoroethylene with n-butyl vinyl ether as 0.005 (r_TFE) and 0.0015 (r_NBVE). The rate of copolymerization is extremely high and has a maximum at an equimolar concentration of two monomers. The alternating structure of the copolymers was confirmed by the analysis of NMR spectra. Some thermal properties of the copolymers were measured by DSC and DTA.     

Radiation-induced copolymerization of methyl trifluoroacrylate with propylene

Copolymerization of methyl trifluoroacrylate (MTFA) with propylene in bulk was induced by γ irradiation. A wide range of the initial monomer composition gives an equimolar alternating co-polymer. The reactivity ratios of r₁ (MTFA) and r₂ (propylene) were determined to be 0.01 and 0.005, respectively. The polymerization rate at an equimolar monomer composition is proportional to the 1.0 power of the dose rate. The dose rate dependency of higher than 0.5 may be ascribed to unimolecular termination due to a degradative chain transfer of propagating radicals to propylene. The G values of the initiating radical formation and the polymerization reaction were calculated to be 1.78 and 1336, respectively. The dependence of the copolymerization rate on the temperature was small, and the activation energy of copolymerization was 1.1 kcal/mole from ?6 to 50°C.     

Emulsion copolymerization of tetrafluoroethylene and propylene with redox system containing tert-butylperbenzoate. I. Polymerization conditions and components

Emulsion polymerization of tetrafluoroethylene and propylene with ammonium perfluorooctanoate, initiated by a redox system containing tert-butylperbenzoate (TBPB) was carried out. The effect of the components of the redox system Is (TBPB, FeSO₄.7H₂O, ethylenediamine tetraacetic acid (EDTA), and CH₂(OH)SO₂Na.2H₂O) on the polymerization rate (R) and molecular weight () was studied. Among redox system components, Fe²⁺ concentration exerts the most significant effect (by power of 0.54) on the polymerization rate. It was found that R ∝ [Is]^0.2–0.54 and M_n ∝ [Is]^0.0–0.1 and polymerization reaction scheme was suggested for the action of the initiating system. The influence of the copolymerization conditions (pressure, temperature, stirring speed, and pH) is also discussed. The apparent activation energy of the reaction was found to be 46.0 kJ/mol. © 1994 John Wiley & Sons, Inc.     

Radiation-induced terpolymerization of tetrafluoroethylene with propylene and isobutylene in bulk

Terpolymerization of tetrafluoroethylene (TFE) with propylene (P) and isobutylene (iB) by γ radiation at temperatures of ?78 to 40°C, a dose rate of 5 × 10⁴?5 × 10⁵ rad/hr, and an iB/P molar ratio of 40/10?5/45 in the monomer mixture was carried out. Alternating copolymers of TFE and α-olefins, that is, P and iB, were formed at various monomer compositions. No crystalline structure was observed in the terpolymer obtained below an iB/P molar ratio of 15/35 in the monomer mixture but a partly crystalline order increased with the amounts of iB in terpolymer. The crystal lattice of the TFE–iB copolymer was affected by the introduction of P. The dose rate dependencies of the polymerization rate and inherent viscosity were 0.8 and ?0.2, respectively. The activation energy of polymerization was 2.4 kcal/mole, and the relative reactivity ratio of iB and P for a TFE radical chain end was estimated as 4.50 by the treatment of the free propagating mechanism.     

Radiation-induced copolymerization of tetrafluoroethylene and 3,3,4,4,5,5,5-heptafluoropentene-1 under pressure

An investigation was made of the γ-ray-induced copolymerization of tetrafluoroethylene and 3,3,4,4,5,5,5-heptafluoropentene-1. At 22°C at 5000 and 10 000 atm the polymerization rate changes little between 0 and 75 mole-% tetrafluoroethylene. Above 90 mole-% the rate increases greatly. Molecular weights vary with composition in a fashion similar to the variation of the rates. Crystallization occurs in the bulk pentene at 13 500 atm at 24°C. The polymerization rate is very low in the solid state. Under some conditions polymerization continues long after irradiation is ended. Both reactivity ratios favor the pentene. Several copolymer properties were studied. The polymers are amorphous and soluble in perfluoro ethers, perfluoro alkanes, and perfluoroaromatics if they contain less than 80% tetrafluoroethylene. The glass temperatures of the amorphous polymers decrease and the thermal and radiation stability increases as the tetrafluoroethylene content increases.     

Microgel formation in emulsion copolymerization. I. Polymerization without seed latex

Microgel formation during emulsion copolymerization of methyl methacrylate and ethylene glycol dimethacrylate is investigated both experimentally and theoretically. It was found that the average crosslinking density is fairly high even from a very early stage of polymerization. The molecular weight distribution (MWD) development in emulsion crosslinking copolymerization is completely different from that in homogeneous polymerization. Because the maximum molecular weights allowed to exist is limited by the particle size, a comprehensive model for the MWD development in nonlinear emulsion polymerization must account for the size of polymerization locus properly. During the formation of microgels, a drastic change in the weight-average molecular weights, which is characteristic of gelation in homogeneous media, is not always required. In a typical microgel formation process where a large mole fraction of divinyl monomer is used, the average molecular weights may increase just linearly with conversion in which a sharp MWD shifts to higher molecular weights with the progress of polymerization. It is shown that the microgels formed in emulsion polymerization are characterized as intramolecularly crosslinked macromolecules that occupy a very large weight fraction in each polymer particle. © 1996 John Wiley & Sons, Inc.     

Polymerization of vinyl chloride and copolymerization with propylene by a ternary catalyst system

Polymerization of vinyl chloride by the ternary catalyst system of VOCl₃–AIR_nCl_3–n complexing agent was investigated. It was suggested that the formation of a polar complex (or charge-transfer complex) between AlR_nCl_3–n and the complexing agent participated in the polymerization of vinyl chloride. In the copolymerization of vinyl chloride with propylene with the present catalyst system, it was more difficult to incorporate the propylene unit in the copolymer than with a typical radical catalyst.     

Emulsifier-free emulsion polymerization of tetrafluoroethylene by radiation. III. Simultaneous formation of hydrofluoric acid

Simultaneous formation of hydrofluoric acid (HF) in the radiation-induced polymerization of tetrafluoroethylene (TFE) was investigated. HF concentration in PTFE latex was determined mainly by conductometric titration with 0.01 and 0.001N NaOH. The amount of HF formed is almost independent of agitation speed and the amount of n-hexadecane added and is maximal at ca. 70°C corresponding to the rate of polymerization. The rate of HF formation increases with the initial pressure of TFE monomer and dose rate and decreases with polymerization or TFE consumption. This fact suggests that HF is formed mainly by TFE reactions and not by the degradation of PTFE. The mechanism of HF formation in this reaction system in the absence of oxygen is shown in the following two schemes: scheme I is the reaction of TFE with primary radicals (OH·, H·, e) from the radiolysis of water; scheme II is the reaction of water with the species from the radiolysis of TFE. On the assumption that HF is formed only according to scheme I, the G value of HF formation G(HF)_calc can be calculated as 11.25. All observed G values G(HF)_obs are larger than G(HF)_calc. When the polymerization is carried out at 20 kg/cm² under various dose rates, G(HF)_obs increases with the dose rate. When the polymerization is carried out at 3.0 × 10⁴ rad/hr under various pressures, G(HF)_obs decreases with the decrease in pressure from 20 to 2 kg/cm² and is fairly close to G(HG)_calc at 2 kg/cm². This indicates that HF formation is due mainly to scheme II at high pressure (in the presence of enough TFE) and to scheme I as the pressure is lowered.     

Radiation-induced emulsion polymerization of ethylene. III. Emulsion polymerization with ammonium perfluorooctanoate as the emulsifier

Radiation-induced emulsion polymerization of ethylene with ammonium perfluoro-octanoate as an emulsifier was studied in order to elucidate the effect of the number of polymer particles. Owing to the stable structure of the emulsifier from a radical attack, no C? F bond was detected in the polyethylene as expected. The polyethylene produced was mostly gel containing a small amount of low molecular weight polyethylene. This may be attributable to chain transfer to the polyethylene. The effects of dose rate and of concentration of the emulsifier were determined without considering the chain-transfer reaction to the emulsifier. By considering the escape of the radical which is produced by chain transfer to the monomer from the polymer particle to the aqueous phase at the steady state, the following equation is derived: The experimental results could be explained by this equation, and the apparent rate constants were obtained.     

Linear copolymerization of piperylene with propylene

Conclusions Linear cooligomerization of piperylene with propylene over the catalyst NiCl₂[P(C₄H₉)3]₂- (C₂H₅)2AlCl results in the formation of 2,3-dimethyl-1,4-hexadiene and 4,5-dimethyl-2,5,8-undecatriene, and to their isomers containing conjugated double bonds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 862–865, April, 1976.     

Radiation-induced copolymerization of methyl trifluoroacrylate with ethylene

Copolymerization of methyl trifluoroacrylate (MTFA) with ethylene in bulk was induced by γ irradiation. The copolymerization was observed to proceed in the liquid monomer mixture of MTFA and ethylene at 25°C with the dose rates ranging from 5.0 × 10⁴ to 1.0 × 10⁶ rad/hr. A wide range of the initial monomer composition gives an almost equimolar and alternating copolymer. The highest polymerization rate was observed at the equimolar monomer composition. The dose rate exponent of the polymerization rate is unity. The reactivity ratios of r₁ (MTFA) and r₂ (ethylene) were determined to be 0.034 and 0.14, respectively.     

Cationic copolymerization of tetrahydrofuran with epoxides. I. Polymerization mechanism in the presence of a glycol

Polymerization of several epoxides and their copolymerization with tetrahydrofuran have been studied. The polymerizations were carried out by use of BF₃·O(C₂H₅)₂ as catalyst in the presence of 1,4-butanediol. Variations of catalyst and 1,4-butanediol ratio and concentration affect polymerization rate, molecular weight, and the formation of cyclic oligomers. The latter is also influenced by monomer fed ratio in the case of the copolymerizations. These effects are discussed, and some observations are made concerning the mechanism, particularly with respect to the role of the 1,4-butanediol. Mayo-Lewis monomer reactivity ratios were determined. The ratios found differed from previously published figures.     

Polymerization of propylene oxide by activated monomer mechanism. Suppression of macrocyclics formation

Evidence for the activated monomer (AM) mechanism operating in the polymerization of propylene oxide (PO) initiated with HBF₄ is presented. The contribution of AM route of propagation is the highest and formation of cyclic oligomers mostly suppressed when monomer concentration is low enough. This was achieved by slowly adding PO to the reaction mixture, as previously proposed on the basis of kinetic considerations.     

Radiation-induced copolymerization of chlorotrifluoroethylene with ethyl vinyl ether

The radiation-induced copolymerization of chlorotrifluoroethylene with ethyl vinyl ether was investigated in the liquid phase at 20 and ?78°C over a wide range of monomer compositions. A copolymer was obtained in which the monomers alternate with regularity along the polymer chain over the entire range of monomer compositions investigated. Both the rate of copolymerization and the intrinsic viscosity of the resulting copolymer were found to depend strongly on the initial monomer composition, both reaching a maximum value at an equimolar concentration of the monomers. The monomer reactivity ratios were determined and correspond well with calculated values. A decrease in the irradiation temperature was accompanied by a marked decrease in the rate of copolymerization and the intrinsic viscosity of the copolymer.