Crosslinking reactions of high density polyethylene with low peroxide concentrations ranging from 0.1 wt% to 1.0 wt% at temperatures of 170, 180 and 190 ℃ were monitored by rheological measurements. A critical gel fo...Crosslinking reactions of high density polyethylene with low peroxide concentrations ranging from 0.1 wt% to 1.0 wt% at temperatures of 170, 180 and 190 ℃ were monitored by rheological measurements. A critical gel forms at the peroxide concentration of 0.2 wt%, where the transition from long chain branching generation to crosslinking network formation could occur. Rheokinetics of crosslinking can be fitted well by Ding-Leonov＇s model. The curing rate k2 at the earlier stage exhibits about 3 times acceleration per 10 ~C with increasing temperature, while the equilibrium modulus G＇ at the fully cured stage is almost independent of temperature. Influences of crosslinking on the subsequent crystallization behaviors were detected by DSC measurements. Above the critical gel concentration, crystallization is largely retarded as evidenced by the lower crystallization temperature Tc and crystallinity Xc due to the network formation. The secondary crystallization valley located at the temperature near 80 ℃ can be observed above the critical concentration, which becomes more evident with the increasing peroxide concentration and curing temperature. This phenomenon provides another evidence of crystallization retardation by the crosslinking network.展开更多
Introduction The emulsion of acrylate copolymers with actively functional groups have been widely developed and used as coating, adhesive and handling agent in spinning and weaving industry. Bessett, D. R. et al. stud...Introduction The emulsion of acrylate copolymers with actively functional groups have been widely developed and used as coating, adhesive and handling agent in spinning and weaving industry. Bessett, D. R. et al. studied the thermoset of N-(isobutoxymethyl) acrylamide by thermal evolution analysis and thermal gas chromatogram. Krejcar,展开更多
Crosslinking reaction of LDPE resin in the presence of dicumyl peroxide （DCP） was studied by isothermal rheological measurements at different temperatures and non-isothermal differential scanning calorimetry （DSC）...Crosslinking reaction of LDPE resin in the presence of dicumyl peroxide （DCP） was studied by isothermal rheological measurements at different temperatures and non-isothermal differential scanning calorimetry （DSC） technique with different heating rates. The kinetic parameters of crosslinking reaction were calculated by both rheological and DSC measurements. The results reveal that with the increase of DCP contents, the apparent activation energy, Ea, ranges from about 140 kJ/mol to 170 kJ/mol and the order of crosslinking reaction, n, approaches unity. The influence of measurement frequency, on crosslinking reaction was also investigated. It can be found that n does not change with the increase of ωand Ea decreases slightly with the increase of ω展开更多
基金financially supported by the Technical Innovation Project of National Institute of Clean and Low-Carbon Energy(No.15H0543)the Open Project of State Key Laboratory of Polymer Materials Engineering of China(Sichuan University)(No.sklpme2015-4-11)
文摘Crosslinking reactions of high density polyethylene with low peroxide concentrations ranging from 0.1 wt% to 1.0 wt% at temperatures of 170, 180 and 190 ℃ were monitored by rheological measurements. A critical gel forms at the peroxide concentration of 0.2 wt%, where the transition from long chain branching generation to crosslinking network formation could occur. Rheokinetics of crosslinking can be fitted well by Ding-Leonov＇s model. The curing rate k2 at the earlier stage exhibits about 3 times acceleration per 10 ~C with increasing temperature, while the equilibrium modulus G＇ at the fully cured stage is almost independent of temperature. Influences of crosslinking on the subsequent crystallization behaviors were detected by DSC measurements. Above the critical gel concentration, crystallization is largely retarded as evidenced by the lower crystallization temperature Tc and crystallinity Xc due to the network formation. The secondary crystallization valley located at the temperature near 80 ℃ can be observed above the critical concentration, which becomes more evident with the increasing peroxide concentration and curing temperature. This phenomenon provides another evidence of crystallization retardation by the crosslinking network.
文摘Introduction The emulsion of acrylate copolymers with actively functional groups have been widely developed and used as coating, adhesive and handling agent in spinning and weaving industry. Bessett, D. R. et al. studied the thermoset of N-(isobutoxymethyl) acrylamide by thermal evolution analysis and thermal gas chromatogram. Krejcar,
基金financially supported by the Industrial Research Projects of the Science and Technology Plan of Ningbo, China(No.2010B10022)
文摘Crosslinking reaction of LDPE resin in the presence of dicumyl peroxide （DCP） was studied by isothermal rheological measurements at different temperatures and non-isothermal differential scanning calorimetry （DSC） technique with different heating rates. The kinetic parameters of crosslinking reaction were calculated by both rheological and DSC measurements. The results reveal that with the increase of DCP contents, the apparent activation energy, Ea, ranges from about 140 kJ/mol to 170 kJ/mol and the order of crosslinking reaction, n, approaches unity. The influence of measurement frequency, on crosslinking reaction was also investigated. It can be found that n does not change with the increase of ωand Ea decreases slightly with the increase of ω
