沥青基短切碳纤维表面改性及与纳米填料并用对天然橡胶力学性能的影响

对硝酸(HNO3)改性沥青基短切碳纤维(PCF)及与炭黑(CB)、白炭黑(Silica)协同填充天然橡胶(NR)进行了研究,考察表面改性及并用对PCF表面形貌、石墨化程度和NR力学性能的影响,分析填料与基体的界面相互作用机制。结果表明,HNO3改性后,PCF的表面粗糙度和O/C比显著增加,而石墨化程度有所降低。PCF单独填充NR时不具有增强作用,而与CB或Silica协同填充NR的拉伸强度显著提高,由3MPa分别提高到18.6MPa和23.7MPa;改性后则可达到24.5MPa和24.7MPa。与CB/NR硫化胶相比,PCF-CB/NR硫化胶的拉伸强度略有降低,但改性PCF-CB/NR硫化胶的拉伸强度则提高了25.6%;与Silica/NR硫化胶相比,添加改性前后的碳纤维均使PCF-CB/NR硫化胶的拉伸强度小幅降低。结合不同增强体系的拉伸强度、50%定伸应力和断面形貌SEM照片可以推断出,PCF单独填充NR时,改性前后均与基体的界面粘合较差;对PCF-CB增强体系来说,界面相互作用的提高主要以吸附理论为主,改性后则以机械互锁和吸附理论共同作用为主;对PCF-Silica增强体系,改性前后均以氢键作用为主。

Influence of PCF surface modification and blending with nanofillers on mechanical properties of Natural Rubber

Natural rubber (NR) reinforced with pitch-based chopped carbon fiber (PCF) modified by nitric acid (HNO3) or blending with carbon black (CB) or Silica was studied.The effects of the surface modification and blending on the surface morphology and microstructure of PCF and mechanical properties of NR matrix composites were investigated, and the mechanism of interfacial interaction between the filler and the matrix was analyzed.The results show that the surface roughness and O/C ratio of PCF are improved evidently, while graphitization degree decrease somewhat by HNO3 treatment.PCF has no reinforcing effect on NR when used alone.However, the tensile strength of NR improves martially by blending PCF with CB or Silica, which enhance from about 3 MPa to 18.6 MPa and 23.7 MPa, respectively, and to 24.5 MPa and 24.7 MPa after modification.Compared with of CB/NR vulcanizates, the tensile strength of PCF-CB/NR vulcanizates decreases slightly, but it enhances 25.6% for PCF-CB/NR vulcanizates.The tensile strength of PCF-Silica/NR where PCF modified or not is a little lower modifieated than that of Silica/NR vulcanizates.Combined with mechanical properties, 50% modulus of different reinforcing system and SEM of fracture section, it can be deduced that the improved interfacial interaction in PCF-CB and NR could be mainly attributed to adsorption theory and a subtle mixture of mechanical interlocking and adsorption theory before and after modification of PCF, but nearly hydrogen bonding in PCF-Silica and NR interface, whether modified or not.