The effect of the dry glass transition temperature on the synthesis of paraffin microcapsules obtained by suspension-like polymerization

Abstract

PRS 1 paraffin wax was encapsulated by means of suspension-like copolymerization of methyl methacrylate (MMA) with butyl acrylate (BA). The effects of the polymeric shell dry glass transition temperature (T g ) and the reaction temperature (T r ) were then studied. Additionally, the evolution of particle diameter, molecular weight, conversion, and T g during polymerization was also researched. The chemical properties of the shell material (acrylic polymer), together with those found in the core material (PRS 1 paraffin wax), for instance: polarity and interfacial tensions, largely determine whether the morphology of the microcapsules will be thermodynamically favored or not. The high polarity of MMA (c 0 ¼ 18 mN m 21 ) and BA (c 0 ¼ 24 mN m 21 ) should provide a thermodynamic driving force to cover the paraffin wax droplet which would result in a core/ shell thermodynamically favored structure. However, most systems are defined by kinetics rather than thermodynamics such as the monomers dry T g and T r . It was observed that penetration of polymer radical chains was severely limited when the dry T g was 108C above the reaction temperature, resulting in irregular and undifferentiated particles. However, penetration did occur when the copolymeric shell dry T g was 108C below the reaction temperature which led to uniform and spherical particles being synthesized. POLYM. ENG.

Polyurethane‐acrylic hybrid emulsions with high acrylic/polyurethane ratios: Synthesis, characterization, and properties

“…MMA and BA are the hard monomer and soft monomer, respectively, which have great influenced on the properties of PU‐AC hybrid films . Although all the films were transparent enough in the visible, in the experiment, the PU‐MMA copolymers formed hard and fragile films, while the PU‐BA copolymers formed soft and sticky films.…”

“…These phenomena are possible caused by the different water solubility and polarity of the two monomers. BA exhibits lower water soluble and polar than MMA . The hydrophobic of the monomers are favor of forming the colloidal particles with bigger size and reduced stability in water, and thus increase in the viscosity of the corresponding emulsions …”

Recent progress in preparation and agricultural application of microcapsules

“…(Huguet & Dellacherie, 1996;Jia et al, 2017;Lulevich & Vinogradova, 2004;Polk, Amsden, De Yao, Peng, & Goosen, 1994a) Temperatures Release, activity and morphology (Cui, Zhang, Lin, Li, & Jin, 2008;Dianawati, Lim, Ooi, & Shah, 2017;Kuck, Wesolowsk, & Norena, 2017;Kohler, Biesheuvel, Weinkamer, Mohwald, & Sukhorukov, 2006;Kohler, Shchukin, Mohwald, & Sukhorukov, 2005;Liu et al, 2008;Ye, Wang, Liu, & Tong, 2005) Particle sizes Loading, aggregation, drug release and retention (Berkland, King, Cox, Kim, & Pack, 2002;Foda & El, 1989;Lemos et al, 2017;Morris & Warburton, 1984;Sen, Bahadur, Mazumder, & Bhattacharya, 2012) Additives and others Strength, release, yield, encapsulation efficiency, membrane porosity, etc. (Angelova & Hunkeler, 2001;Bartkowiak, 2002;Fang, Li, & Liu, 2010;Jono et al, 1997;Luzzi & Gerraughty, 1967;Simón, Rodriguez, & Sanchez, 2013;Varma, Kaushal, Garg, & Garg, 2004;Wang, Hu, Liu, He, & Guo, 2011;Wong et al, 2015;Yamaguchi et al, 2002) F I G U R E 4 Schematic diagram of chitosan and sodium alginate polyelectrolyte membrane formation (Liu et al, 2008) (Cui et al, 2008). Therefore, the temperature not only affects the structures and properties of the microcapsule shells, but also affects the sustained release characteristics of the loaded contents.…”

“…The optimum reaction conditions were as follows: the agitation rate at 250 rpm, the core/wall material weight ratio of 1.4:1, 1.5% of emulsifier sodium dodecyl benzene sulfonate, and the reaction time for 3 hr, which affects the surface morphology and core permeability of microcapsules (Wang et al, 2011). Simón et al synthesized paraffin-containing particles with methyl methacrylate (MMA) and butyl acrylate (BA) by suspension polymerization and found that the glass transition temperature (T g ) of polymers and the reaction temperature (T r ) affected the shape of the microcapsules (Simón et al, 2013). It appeared to the uniform microparticles, which were formed at the wall dry T g of 10-20 C below T r ; it may be related to the high polarity of MMA and BA (Simón et al, 2013).…”

“…Simón et al synthesized paraffin-containing particles with methyl methacrylate (MMA) and butyl acrylate (BA) by suspension polymerization and found that the glass transition temperature (T g ) of polymers and the reaction temperature (T r ) affected the shape of the microcapsules (Simón et al, 2013). It appeared to the uniform microparticles, which were formed at the wall dry T g of 10-20 C below T r ; it may be related to the high polarity of MMA and BA (Simón et al, 2013). Bartkowiak A. investigated effects of ionic strength on performance of alginate/oligomeric chitosan microcapsules and found that the properties of capsules were directly associated with the ionic strength of the solvents (Bartkowiak, 2002).…”