Bulk polymerization of styrene in presence of polybutadiene: Calculation of molecular macrostructure

Abstract

SYNOPSISIn our previous publication the detailed molecular macrostructure generated in a solution polymerization of styrene (St) in the presence of polybutadiene (PB) at 6OoC, was theoretically calculated. In this work, an extended kinetic mechanism that incorporates monomer thermal initiation, chain transfer to the rubber, chain transfer to the monomer, and the gel effect is proposed, with the aim of simulating a bulk high-impact polystyrene (HIPS) process. The mathematical model enables the calculation of the bivariate weight chainlength distributions (WCLDs) for the total copolymer and for each of the generated copolymer topologies and the univariate WCLDs for the free polystyrene (PS), the residual PB, and the crosslinked PB topologies. These last topologies are characterized by the number of initial PB chains per molecule; copolymer topologies are characterized by the number of PS and PB chains per molecule. The model was validated with published literature data and with new pilot plant experiments that emulate an industrial HIPS process. The literature data correspond to a dilute solution polymerization at a constant low temperature with chemical initiation and a bulk polymerization at a constant high temperature with thermal initiation. The new experiments consider different combinations of prepolymerization temperature, initiator concentration, and solvent concentration. One of the main conclusions is that most of the initial PB is transformed into copolymer. For example, for a prepolymerization temperature of 12OOC with addition of initiator, the experimental measurements indicate that the final total rubber mass is approximately three times higher than the initial PB. Also, according to the model predictions, the final weight fractions are: free PS, 0.778; graft copolymer, 0.220; initial PB, 0.0015; and purely crosslinked PB, 0.0005. The final graft copolymer exhibits the following characteristics: average molecular weights, Mn,c = 492,000 and Mw,c = 976,000; average weight fraction of St, 0.722; and average number of PS and PB branches per molecule, 5.19 and 1.13, respectively. 0 1996JohnWiley & Sons, Inc.

Partition of tert-dodecyl mercaptan in systems containing styrene, polystyrene, and polybutadiene. Its effect on the macromolecular characteristics of high-impact poly styrene

“…4c). It should be noted that the CTA reduces the molar masses of both the free and grafted PS [12]. Also, the grafting efficiencies are lower in Reaction 2 (Fig.…”

“…The conversion was calculated from the ratio between the total mass of polymerized St and the initial mass of St, while the St grafting efficiency was calculated from the ratio between the mass of grafted St and the total mass of polymerized St. Both variables were determined by solvent extraction-gravimetry [12]. First, the solvent and the unreacted St were eliminated under vacuum at room temperature until constant weight, and the total polymer mass was measured.…”

Simulation of a Continuous Bulk Styrene Polymerization Process with Catalytic Initiation for Crystal-Clear Polystyrene and Rubber-Modified Polystyrene

“…Mi, = -6.7 x10 5 J I kg (Peng, 1990) (Estenoz et al , 1996) (Estenoz et al, 1996) (Peng, 1990) (Peng, 1990) (Hui and Hamielec, 1972) (Hui and Hamielec, 1972) (Manaresi et al , 1975) (Rintelen et al, 1983) (Rintelen et al, 1983) Trademark names: Trigonox (Akzo) ; Lupersol or Luperox (Elf Atochem) manufacturer at I 0-15 ppm to prevent the poly me• iz<:tioP during shipping and storage . It has been suspected that the residual inhibitor after a TBC removal column may still interact with zinc stearate to give an undesi rable color.…”

“…Gonzalez et al ( 1996) examined bulk styrene polymerization using different binary mixtures of mono-and bifunctional initiators in a batch reactor. Estenoz et al ( 1996) investigated the molecular macrostructure of bulk styrene polymerization initiated by tert-butylperoxy-2-ethylhexanoate or tert-butylperoxy octoate (tBPO) in the presence of polybutadiene rubber in a batch reactor. Rintelen et al ( 1983) studied the formation of oligomers and verified the kinetic equations and data established in a batch reactor to be valid in continuous reactors.…”

Grafting Efficiency in High-Impact Polystyrene by Sec Combined With Theoretical Predictions From a Polymerization–sec Model

“…The kinetic parameters were all taken from the literature. [9,10] The least-known kinetic parameter was the initiation ratio k i,m =k i,r , where k i,m is the reaction rate between the initiator primary radical and the monomer, and k i,r is the reaction rate between the same primary radical and a butadiene repeating unit contained either in the unreacted PB or in the GC. As expected, k i,m =k i,r exhibits a large effect on the GE and, for example, a 30% decrease in this ratio increases the GE by around 25%.…”