Abstract:

Objective In order to address the market demand for elastic textile finishing and to overcome the instability and performance limitations of polyurethane-silicone hybrid systems, a novel strategy is proposed based on emulsion polymerization, blending, and post-crosslinking to prepare elastic silicone oil emulsions, aiming to develop a stable, effective elastic silicone finishing agent that is capable of providing elasticity for textiles.

Method Within the emulsion system, octamethylcyclotetrasiloxane (D4) is copolymerized with coupling agents containing epoxy and amino groups, respectively, yielding two types of organosilicon emulsions functionalized with epoxy and amino groups. These two emulsions are then blended and applied to fabric finishing. During the curing stage, the epoxy and amino groups in the emulsion undergo interparticle crosslinking reactions, forming a three-dimensional network that imparts the fabric with elastic handling. The influences of blending ratio and curing temperature on the post-crosslinking reaction were systematically investigated using infrared spectroscopy and differential scanning calorimetry, intending to optimize the emulsion blend composition.

Results When the triethoxy groups of the amino coupling agent were replaced with dimethoxy groups during emulsion copolymerization, the polysiloxane chains transformed from a crosslinked structure to a linear structure, reducing the crosslinking temperature peak of the blended emulsion by 30 ℃. This enabled the development of a low-temperature crosslinking solution. Fourier transform infrared spectroscopy (FT-IR) analysis confirmed the successful ring-opening reaction between amino and epoxy groups of the emulsion blends during the high-temperature film formation process. Differential scanning calorimetry (DSC) results showed that the maximum crosslinking enthalpy was 25.3 J/g at the mass ratio of E3 to A3 of 1∶1, corresponding to an equimolar functional group ratio of amino and epoxy groups. The crosslinking reaction was sensitive to the curing temperature as well as chain structure. The increase of curing temperature from 120 ℃ to 180 ℃ led to the extent of reaction growing from 24.3% to 93.5%, as a result of enhanced polymer chain diffusion among particles at high temperature. The replacement of crosslinked chain structure amino silicone with linear one resulted in a 30 ℃ decrease in the reaction peak temperature, which benefits the finishing of heat-sensitive fabrics like nylon. The amino-epoxy blended emulsion also showed excellent chemical and disperse stability. The blend emulsion with a 1∶1 mixing was applied to finish polyester fabric, endowing a 45°increment of the elastic recovery angle to the finished fabric.

Conclusion Amino and epoxy functionalized silicone emulsion were successfully prepared by emulsion copolymerization of D4 with amino and epoxy coupling agents. The high efficiency curing reaction between amino and epoxy functionalities occurred during the film formation process of the blend latex at an increased temperature of 180 ℃. The reactivity of the blend emulsion was successfully maneuvered by blending ratio as well as chain structure of amino silicon emulsion. The measurement of reaction enthalpy indicated that the maximum value was achieved at 1∶1 blending ratio. Compared to the blend emulsion engaging amino silicon with crosslinked chain structure, the one blended with a linear chain structured amino silicon exhibited a significant decrease in the curing reaction temperature. The blend emulsion had excellent chemical and shear stability. All the above findings indicated the blend emulsion was applicable for fabric elastic finishing, which was further confirmed by the significant improvement in polyester fabric elastic recovery angle. In conclusion, a new and stable platform was demonstrated for developing high-performance silicone-based finishing agents showing elastic handling.

Key words: emulsion polymerization, elastic silicone emulsion, amino silicone oil, epoxy silicone oil, latex film formation, post-crosslinking reaction, silicone finishing agent