Soft core–hard shell latex particles for mechanically strong VOC‐free polymer films

Abstract

Polymer films cast from aqueous polymer dispersions typically suffer from an inherent lack of mechanical strength when compared to their solvent-borne counterparts. This drawback can be overcome by the use nanostructured hybrid particles that contain both a hard and soft phase. In this work, we demonstrate the use latex particles consisting of a soft core with a multilobed hard shell synthesized by seeded semicontinuous emulsion polymerization with the aim of maximizing the interconnectivity of the hard phase in the resulting polymer film, thus generating films with improved mechanical properties. Films with a minimum film formation temperature (MFFT) close to that of the soft phase are formed while obtaining a Young's modulus up to 4.5 times higher that of a standard homogeneous latex particle. The effect of annealing temperature on film morphology is also investigated, clearly demonstrating that a marked difference in mechanical properties is observed when a percolating network of the hard phase within the film is obtained.

Emulsifier-Free Acrylate-Based Emulsion Prepared by Reverse Iodine Transfer Polymerization

“…Changing soft/hard monomer ratio may not make obvious difference in size. However, there is also work reported that the particle size was not affected by mass ratio of BA/MMA [53][54][55] in conventional emulsion-free radical polymerization. In Figure 2, we also found PDI was around 0.06 ± 0.03, except for the particle in the ratio of 1/1.…”

Core–Shell Polymer Adhesive for Aluminized Coatings: From Improved Barrier Properties to Commercial Formulation

“…Core–shell (CS) nanoparticles are the combination of two different phases with well‐defined properties. For instance, in the present case, it seems promising to use a hard‐core/soft‐shell system to ensure better mechanical and barrier properties in the core, protected by a soft shell responsible for forming a homogeneous, defect‐free film …”

“…In the specific case of food packaging, better mechanical and barrier properties in the core, protected by a soft shell responsible for forming a homogeneous, defectfree film. [10][11][12][13][14][15][16] Core-shell particles are almost exclusively made using a seeded semibatch emulsion polymerization process. [17][18][19][20] Seed properties [21,22] and process control [23,24] will play a major role in determining the final morphology of the latex particles.…”

“…[51] The permeation process takes place in the amorphous phase of the polymeric film, as the interstitial volume of the crystalline fraction is so low that sorption and diffusion can occur only in the amorphous phase. [14] This in turn implies that it is necessary to consider the state of this matrix, whether it is above or below the glass transition (T g ), and whether or not it is crosslinked. [52][53][54][55] In short, factors that restrict the mobility of the chains in the amorphous fraction of the polymer can decrease the diffusivity, and thus permeability of penetrants.…”

“…The diffusivity of the penetrant will depend to a great extent on the free volume of the polymer through which it is diffusing . The permeation process takes place in the amorphous phase of the polymeric film, as the interstitial volume of the crystalline fraction is so low that sorption and diffusion can occur only in the amorphous phase . This in turn implies that it is necessary to consider the state of this matrix, whether it is above or below the glass transition ( T g ), and whether or not it is crosslinked .…”