Effects of Sm3+/PMAA on mechanical and thermal properties of natural rubber latex film

Samarium carbonate [Sm2(CO3)3] was taken as the source of Sm3+, and methyl acrylic acid (MAA) was employed as the precursor to prepare polymethacrylic acid (PMAA). The mixture of Sm2(CO3)3 and PMAA was marked as “SmP.” The SmP prepared under different conditions was added to natural rubber (NR) latex to prepare NR/SmP films. The influence of the polymerization temperature of MAA and the amount of SmP on the mechanical properties and structure of NR/SmP films were analyzed. The results show that polymerization temperature has significant effect on the mechanical properties of NR/SmP film; lower temperature is benefit to improve modulus and rigidity, whereas higher temperature helps maintain good elasticity. Compared with neat NR, addition of 5‐phr Sm2(CO3)3 results in a 30%–37% increase of tensile strength. Furthermore, the glass transition temperature (Tg) can also be increased by the addition of SmP; and the tan δ curves of all samples exhibit only one transition peak and indicate no phase separation between SmP and NR matrix. The influence of SmP on the structure and morphology of NR was explored by Fourier transform infrared, X‐ray diffraction, thermogravimetric analysis, and scanning electron microscopy analysis; and the results show that SmP can be dispersed uniformly in the NR latex when loading of Sm2(CO3)3 is lower than 20 phr. The improved mechanical and thermal stability of Sm3+/PMAA/NR latex film are attributing to the multiple interactions between rubber chain and Sm3+/PMAA; the polymerization degree of PMAA show a significant effect on the density of ionic crosslinks, ion clusters and covalent networks.