Synthesis of solvent absorption-desorption styrenic imbiber beads by suspension polymerization

Abstract

Syntheses of styrene-divinylbenzene copolymer beads were carried out bysuspension copolymerization. The reactions were performed in the presence of benzoylperoxide and poly(vinyl alcohol) as the initiator and suspending agent, respectively.The effects of reaction parameters, namely, monomer phase weight fraction, agitationrate, reaction temperature, reaction time, initiator concentration, crosslinkingagent concentration, concentration of suspending agent, diluent composition, and thethird comonomer, ~in~i-butyl acrylate or 2-ethyl hexyl acrylate, on the averageparticle size, size distribution, crosslinking density, and swelling properties ofthe resulting copolymers were thoroughly investigated. The average particle size andsize distribution was measured by sieve analysis, the swelling properties bygravimetric measurement, thermal properties by DSC, the functional groups by FT-IR,kinetics of absorption and desorption by optical microscopy, surface morphology bySEM, density by the liquid displacement technique, pore properties by a mercuryporosimeter and solubility parameters by swelling experiments. The absorption of thesolvent mixture on the water surface was also investigated. The optimum conditions for the polymerization were found to be as follows: 0.5%w/w BPO; 0.1% w/w PVA; 0.1 of the monomer phase weight fraction; 6% w/w DVB; theTol/Hep ratio (w/w) was 60/40; the agitation rate was 270 rpm; the reactiontemperature and time were 70(+,ฐ) C and 10 hrs, respectively. After variouscharacterizations, the resulting synthesized copolymers were spherical beads and hadthe following properties: average particle sizes were in the range of 0.82 - 1.49 mm;average pore diameter (1.33 - 2.12) x 10('-2) (+,m)m; surface area 17.466 - 44.057m('2)/g; pore volume 5.81 x 10('-2) - 2.34 x 10('-1) cm('3)/g; density 0.9375 -1.0581 g/cm('3); swelling ratios in the range of 4.2 - 12.3 times in toluene;solubility parameter 18.2 - 19.0 (MPa)('1/2.), the glass transition temperature(T(,g)) in the range of 42 - 107 (+,ฐ) C; the diffusion coefficient in the rangeof 6.40 x 10('-6) - 1.52 x 10('-5) cm('2)/sec. The advantage of these syntheticcopolymer beads is that they are capable of sorption and desorption of severalindustrial solvents with solubility parameters in the range of 18.2-19.0 (MPa)('1/2)which are beneficial for the removal of spilled solvents and oil on the surface ofwater in our environment. The lifespan of the beads is longer than 3 repeated useswhile still retaining their spherical shape.