Inphonlek Supharat, Bureewong Namthip, Jarukumjorn Kasama, Chumsamrong Pranee, Ruksakulpiwat Chaiwat, Ruksakulpiwat Yupaporn
School of Polymer Engineering, Institute of Engineering, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
Research Center for Biocomposite Materials for Medical Industry and Agricultural and Food Industry, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
Polymers (Basel). 2022 Oct 29;14(21):4602. doi: 10.3390/polym14214602.
This work aims to enhance the polarity of natural rubber by grafting copolymers onto deproteinized natural rubber (DPNR) to improve its compatibility with silica. Poly(acrylic acid--acrylamide)- DPNR ((PAA--PAM)-DPNR) was successfully prepared by graft copolymerization with acrylic acid and acrylamide in the latex stage, as confirmed by FTIR. The optimum conditions to obtain the highest conversion, grafting efficiency, and grafting percentage were a reaction time of 360 min, a reaction temperature of 50 °C, and an initiator concentration of 1.0 phr. The monomer conversion, grafting efficiency, and grafting percentage were 91.9-94.1, 20.8-38.9, and 2.1-9.9%, respectively, depending on the monomer content. It was shown that the polarity of the natural rubber increased after grafting. The (PAA--PAM)-DPNR was then mixed with silica to prepare DPNR/silica composites. The presence of the (PAA--PAM)-DPNR and silica in the composites was found to improve the mechanical properties of the DPNR. The incorporation of 10 phr of silica into the (PAA--PAM)-DPNR with 10 phr monomer increased its tensile strength by 1.55 times when compared to 10 phr of silica loaded into the DPNR. The silica-filled (PAA--PAM)-DPNR provided s higher storage modulus, higher Tg, and a lower tan δ peak, indicating stronger modified DPNR/silica interactions and greater thermal stability when compared to silica-filled DPNR.
这项工作旨在通过将共聚物接枝到脱蛋白天然橡胶（DPNR）上来增强天然橡胶的极性，以提高其与二氧化硅的相容性。通过在胶乳阶段与丙烯酸和丙烯酰胺进行接枝共聚成功制备了聚（丙烯酸 - 丙烯酰胺）- DPNR（（PAA - PAM）- DPNR），这通过傅里叶变换红外光谱（FTIR）得到证实。获得最高转化率、接枝效率和接枝率的最佳条件是反应时间360分钟、反应温度50°C和引发剂浓度1.0 phr。单体转化率、接枝效率和接枝率分别为91.9 - 94.1%、20.8 - 38.9%和2.1 - 9.9%，具体取决于单体含量。结果表明，接枝后天然橡胶的极性增加。然后将（PAA - PAM）- DPNR与二氧化硅混合以制备DPNR/二氧化硅复合材料。发现复合材料中（PAA - PAM）- DPNR和二氧化硅的存在改善了DPNR的机械性能。与在DPNR中加入10 phr二氧化硅相比，在含有10 phr单体的（PAA - PAM）- DPNR中加入10 phr二氧化硅使其拉伸强度提高了1.55倍。填充二氧化硅的（PAA - PAM）- DPNR具有更高的储能模量、更高的玻璃化转变温度（Tg）和更低的损耗因子（tan δ）峰，表明与填充二氧化硅的DPNR相比，改性后的DPNR/二氧化硅相互作用更强，热稳定性更高。
