Self-Crosslink Acrylic Latex And Its Water-Borne Wood Coating

In this paper, the influence of the latex particles structure, the film formation process and crosslink on the performance of the latex and its film have been investigated.Self-crosslinkable core-shell latex was synthesized through two-stage emulsion polymerization with acrylate monomers and diacetone acrylamide (DAAM). Hydrophilic DAAM was introduced in the core and hexanediol diacrylate (HDDA) in the shell. The influence of the hydrophilic core glass-transition temperature (T_g) on the latex particles structure and the film properties were studied, then the film formation mechanisms were suggested. Lower core T_g helps the migration of the core polymer to the outer crosslink layer and increases the gel content and compatibility of the film with two phases. The latex with higher core T_g has more obvious core-shell structure, and the pencil hardness of the film is higher.DDM as chain transfer agent was introduced into self-crosslinkable acrylate latex system. The polymerization rate was increased, but the T_g of the polymer, the minimum film formation temperature (MFFT) of the latex were decreased. When the ratio of DDM/monomers was less than 1.67 % (wt.%), the gel content and the Young's modulus of the latex film remained at the high level, but the MFFT of the latex changed much.Acrylate latexes with different self-crosslink system were synthesized and characterized. For DAAM-ADH (adipic dihydrazide) system, the film pencil hardness could be enhanced by increasing the design T_g and the DAAM content in monomers, and advancement was difficult once 2H was gained. The application of acetoacetoxy ethyl methacrylate-hexamethylene diamine (AAEM-HAD) system increased the pencil hardness to 3H, but influenced the film formation process negatively. Core-shell structured latex with high pencil hardness and good film-formation performance was gained when there were much difference in weight and T_g between core and shell.Acrylate latex with DAAM/AAEM-ADH di-self-crosslink system, whose core was introduced AAEM into and shell DAAM, was prepared. The swell ratio and water absorption of the latex film decreased and pencil hardness increased when self-crosslinkable monomers content increased. The gel content of the latex film was lower than that of DAAM-ADH system latex film, but higher than AAEM-HAD system. Compared with the above two systems, the films of the di-self-crosslink system latex have higher water absorption and lower contact angle.