ABSTRACT
In order to reduce the environmental pollution caused by waste rubber and to realize the recycling of resources, we proposed a facile method for the hydrophilic modification of waste rubber powder (HRP) and used it to reinforce a composite hydrogel. In the presence of toluene, dibenzoyl peroxide (BPO) diffused into the waste rubber powder. After the solvent was removed, BPO was adsorbed in the rubber powder, which was used to initiate the grafting polymerization of the acrylamide monomer on the rubber-water interface. As a result, the polyacrylamide (PAM) molecular chains were grafted onto the surface of the rubber powder to realize hydrophilic modification. The success of the grafting modification was confirmed by FTIR, contact angle testing, and thermogravimetric analysis. The hydrophilic modified waste rubber powder was used to reinforce the PAM hydrogel. Mechanical tests showed that the tensile strength and elongation at the break of the composite hydrogel reached 0.46 MPa and 1809%, respectively, which was much higher than those of pure PAM hydrogel. Such a phenomenon indicates that the waste rubber particles had a strengthening effect.
ABSTRACT
Simultaneously achieving good mechanical properties and high tolerance to hot and cold environments in hydrogel materials remains a challenge. In this work, ethylene glycol (EG) and cellulose nanofibrils (CNFs) were introduced into chitosan/poly(acrylamide-acrylic acid) double-network hydrogels to improve their toughness and tolerance to hot and cold environments. The effect of EG and CNFs on the properties of the hydrogels was studied respectively. EG increases the tolerance of the hydrogel to hot and cold environments. However, EG had a negative effect on the mechanical properties of hydrogels. In addition, CNFs substantially enhanced the strength and toughness of the chitosan/poly(acrylamide-acrylic acid)/EG organohydrogels. Finally, with the cooperative action of EG and CNFs, high-strength and tough organohydrogels (tensile strength = 0.71 MPa, elongation at break = 787.2%) with a high tolerance to hot and cold environments (-23 °C to 60 °C) were obtained. Further, EG enabled the organohydrogel to revert to its original state after drying at 60 °C. This paper provides a new route to prepare high-strength and tough organohydrogels with a high tolerance to hot and cold environments.