“…In the crystallization process, non‐isothermal crystallization is more important because of its practicality, especially in construction materials 18 . Although more and more polymers, such as epoxy resin (EP), 19 polyethylene (PE), 20 and PVC, 21 are being used in construction materials to improve the performance of composites, there are few studies on the non‐isothermal crystallization and morphology of PP systems incorporating sodium dodecylbenzene sulfonate (SDBS) modified clays.…”
The crystalline behaviors of polymers have a large impact on their physical and mechanical properties, especially as reinforcing and toughening materials in the construction industry. This work investigates the crystallization behaviors of polypropylene (PP) composites with layered double hydroxide (LDH) by using differential scanning calorimeter and a polarizing optical microscope (POM), and analyzed the non‐isothermal crystallization kinetics of PP composites by Avrami model and Mo's method. The results show that the entire process of non‐isothermal crystallization is appropriate for Mo′s method instead of Avrami model due to the offset of the curves in initial nucleation and secondary crystallization stages. The addition of LDH and modified LDH (SLDH) can increase the crystallinity (Xc) of PP despite decreasing the crystallization rate in the non‐isothermal crystallization process. The migration activation energy (∆E) indicates that LDH acts as a heterogeneous nucleating agent, which is consistent with POM results. The values of ∆E and semi‐crystallization time (t1/2) reveal that the nucleation capacity of PP/LDH is greater than that of PP/SLDH, but the crystallization rate of PP/LDH is slower than that of PP/SLDH, resulting in a decrease in Xc.
“…In the crystallization process, non‐isothermal crystallization is more important because of its practicality, especially in construction materials 18 . Although more and more polymers, such as epoxy resin (EP), 19 polyethylene (PE), 20 and PVC, 21 are being used in construction materials to improve the performance of composites, there are few studies on the non‐isothermal crystallization and morphology of PP systems incorporating sodium dodecylbenzene sulfonate (SDBS) modified clays.…”
The crystalline behaviors of polymers have a large impact on their physical and mechanical properties, especially as reinforcing and toughening materials in the construction industry. This work investigates the crystallization behaviors of polypropylene (PP) composites with layered double hydroxide (LDH) by using differential scanning calorimeter and a polarizing optical microscope (POM), and analyzed the non‐isothermal crystallization kinetics of PP composites by Avrami model and Mo's method. The results show that the entire process of non‐isothermal crystallization is appropriate for Mo′s method instead of Avrami model due to the offset of the curves in initial nucleation and secondary crystallization stages. The addition of LDH and modified LDH (SLDH) can increase the crystallinity (Xc) of PP despite decreasing the crystallization rate in the non‐isothermal crystallization process. The migration activation energy (∆E) indicates that LDH acts as a heterogeneous nucleating agent, which is consistent with POM results. The values of ∆E and semi‐crystallization time (t1/2) reveal that the nucleation capacity of PP/LDH is greater than that of PP/SLDH, but the crystallization rate of PP/LDH is slower than that of PP/SLDH, resulting in a decrease in Xc.
“…As Figure 3b shows, the MRT of the EPU-WG system was 148 °C , which was higher than the PU-WG system. This is because the addition of epoxy resin increased the content of the hydroxyl group (-OH), which could react with free isocyanate (-NCO) in the system [18]. However, due to the heat generated by the reaction of -OH in epoxy resin and -NCO was partly released in the process of the prepolymer, the MRT of EPUP-WG-1 was lower than that of EPU-WG-1.…”
Polyurethane (PU) grouting materials possess excellent fluidity and strong injectability. However, the high heat release during the reaction process restricts its application. In this study, with the addition of water glass (WG), a prepolymer was prepared by epoxy resin reacted with isocyanate to form modified polyurethane. The effects of epoxy resin and water glass on the compressive properties, expansion rate, structure of the cell, and maximum reaction temperature of the grouting materials were also investigated. The results showed that the cell size of modified PU was smaller and more regular, the maximum reaction temperature of the modified PU was reduced to 89 °C, and the compressive strength and expansion rate went up to 0.27 MPa and 57, respectively. This investigation will expand the application of PU grouting materials in underground engineering.
“…It could be seen from the viscosity-time curve that as time increased (the time range was 0–400 s), the viscosity was almost stable between 17 and 19 mPa.s in Figure 5 and its viscosity was much lower than the commonly used E51 resin whose viscosity was 11,000–14,000 mPa.s and other epoxy resins. 44,45 Due to its small molecular weight, DVBDO had low viscosity and good fluidity, which was convenient for molding and processing.Figure 5.The viscosity-time curve of DVBDO.…”
To explore thermal and mechanical properties of epoxy material, difunctional aromatic epoxy--divinylbenzene dioxide (DVBDO) had been synthesized by epoxidizing divinylbenzene, using the metal acetylacetone compound grafted Fe3O4 particles as the catalyst. The catalyet had high conversion and epoxy selectivity and could be recyclable. Then the polymerization of DVBDO with different diamine curing agents were reported. The structure and viscosity of DVBDO were firstly characterized. Because it had low molecular weight and viscosity, DVBDO had excellent liquidity and formability. Subsequently to clarify the properties of epoxy thermosets, experiments to determine thermal and mechanical performances were carried out, such as differential scanning calorimetry (DSC), thermal gravimetric (TGA), dynamic mechanical analysis (DMA) and tensile test. It could be observed that the thermoset polymers using DVBDO as epoxy matrix had excellent thermal (Tg was about 201°C) and mechanical properties (tensile strength was 131.99Mpa). Possibly considering that this kind of thermoset polymers had higher rigidity and crosslink density. In conclusion, a new type of one-component liquid epoxy encapsulant material with low viscosity, good filling fluidity, strong heat resistance and excellent storage performance had been developed.
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