Xu Yang,Hong Zhao,Chengcheng Zhang,Chunyang Li,Xindong Zhao,Jiaming Yang,Xuan Wang
To enhance the DC electrical performance of cross-linked polyethylene (XLPE), the graftable antioxidant methacrylic acid 2-hydroxy-3-(4-anilinoanilino) propyl ester (GA), which contains carbonyl and amino groups, and the crosslinking coagent trimethylolpropane trimethacrylate (TMPTMA), which contains carbonyl groups, are individually or co-grafted onto XLPE. The slightly higher deep trap density introduced by higher grafting concentration of TMPTMA results in more significant suppression effect of conductance current and enhanced breakdown strength at a lower temperature, while the suppression effect for the conductance current at 90°C becomes weakened due to limited trap energy. Meanwhile, the deeper energy level introduced by GA suppresses the conductance current and improves the electrical strength of XLPE at 90°C more significantly. By co-grafting, the conductance current of XLPE in a wide range temperature can be significantly reduced, especially for the temperature dependence of conductance current, which is beneficial to suppress the field strength reversal. The results of thermally stimulated current and molecular simulation show that the polar groups of two monomers introduce deep charge traps in XLPE. The co-grafting system ensures the rationality of the crosslinking reaction kinetics and does not affect the cable manufacturing.
In this study, we employed two distinct branching coagents to optimize the topology structure of long-chain branched polylactide (LCB-PLA) via melt grafting with 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane (Trigonox301) and PLA. Our findings reveal that an impressive 22.8% degree of branching degree in PLA was attainable with the addition of merely 2 wt % allyl glycidyl ether (AGE) and 0.75% Trigonox301. Three mathematical models were applied to quantitatively assess the degree of branching based on molecular weight distribution, zero-shear viscosity η 0 , and phase angle. Notably, the presence of gel complicated the precise determination of the branching degree when using LCB G derived from molecular weight distribution fitting. Comparatively, the η 0 and LCB C , derived from complex viscosity fitting for LCB-PLA samples enriched with 2 wt % AGE, saw a marked escalation from 2140 Pa s and 0 mol % to 13286 Pa s and 22.8 mol %, respectively. Furthermore, the preferential end-group reaction between the epoxy group of AGE and the carboxyl group of the PLA molecule chain indicated that AGE was more efficacious in enhancing the branching degree than trimethylolpropane triacrylate (TMPTA).
Gum vulcanizates exhibit Payne effect and weak strain overshooting behavior, which is usually forgot in rubber industry. Herein the Payne effect of butadiene rubber (BR) vulcanizates is investigated for clarifying the effect of crosslinking density and sol content mediated by using coagent in conjugation with dicumyl peroxide. Toluene extraction and paraffin swelling of the vulcanizates are performed for clarifying the contribution of sol fraction and chains entanglement. The results show that the Payne effect and weak strain overshooting of gum vulcanizates are closely related to effective crosslinking density rather than network defects. This work is helpful for understanding the nonlinear rheological responses of the gum vulcanizates with defective network structure.
危险品化学品经营许可证（带存储）