Reinforcement of natural rubber (NR) latex films is one of the most difficult tasks in latex industry. Among the others, the best reinforcing filler is silica that steers for improvement of mechanical properties such as tear and tensile strengths of rubber matrix. However, surface of the silica particle is surrounded by hydrophilic silanol groups which are less compatible with natural rubber molecules. Hence, silica is not easy to be used as reinforcing filler for NR latex films without any surface modification. A study of modification of silica surface was successfully done by using an acrylic polymer synthesized in the laboratory. However, synthesis of polymers in this regard is not economically sound for latex industry. Therefore, a commercially available sodium salt of acrylic co-polymer solution is consumed for the modification of surface of silica particles. Modification is accomplished by the establishment of hydrogen bonds between silanol groups of silica and hydrophilic groups of co-polymer and that is confirmed by FTIR spectroscopy. Stability of modified filler dispersion is optimum at neutral pH and particle size reduction of modified filler particles is compatible with the size of rubber particles. The improved physical properties of modified filler added NR latex films are confirmed by testing tear strength, tensile strength and elongation at break. The preferred level of flexibility through interactions formed between modified filler and rubber matrix is shown by reduced glass transition temperature of modified filler added NR films that tested using differential scanning calorimeter (DSC)
