ACS Applied Polymer Materials
·
2020
·
IF 0
Yang Gao,Haijun Dong,Licheng Liu,Yingfeng Yu,Zhengming Tang,Chenyan Bai,Thorsten Schmidt,Yanli Feng,Hongyu Chen
For many applications, polyurethanes (PUs) need to have a fast curing speed and long pot life. Latent catalysts are seen to be one of the approaches that can fulfill this need. In this article, we have synthesized a series of copolymers with n-alkyl acrylates and a reactive tin catalyst, dibutyltin maleate, by conventional free radical polymerization using azodiisobutyronitrile (AIBN) as an initiator and dodecanethiol as a chain transfer agent. The copolymers with crystalline side chains were characterized by gel permeation chromatography (GPC), 1H NMR, 13C NMR, differential scanning calorimetry (DSC), and ion chromatography. The tin-containing copolymers showed high crystallinity. The melting temperature of the copolymers decreases slightly with the decrease of molecular weight (Mw), while the crystallinity remains almost unchanged. The catalytic performance and latency of the crystalline copolymers with different particle sizes were characterized by rheological measurement and Fourier transform infrared spectroscopy (FTIR). The crystalline copolymers showed quite good latency at 30 °C and high reactivity above the melting point. Both the particle size and the Mw of the copolymers had effects on the latency of crystalline catalysts. The PU adhesive with copolymers showed a higher peel strength at the initial stage than the noncatalyzed one and comparable final properties as compared with the samples with dibutyltin dilaurate and dibutyltin maleate.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
JOURNAL OF APPLIED POLYMER SCIENCE
·
2020
·Vol. 138
·期 4
·49730
·
IF 2.52
Kunxiang Shi,Yucai Shen,Yunxu Yang,Tingwei Wang
A series of latent curing agents were developed by replacing the hydrogen atom on secondary amine in imidazole with methoxy polyethylene glycol maleate diesters via Michael addition reaction. Methoxy polyethylene glycol maleate diesters with different molecular weight also restrained the reactivity of tertiary amine in imidazole ring. The curing properties and pot-life of the modified imidazole/epoxy systems were measured by differential scanning calorimeter and rotational rheometer. The modified imidazole/epoxy system could be cured quickly at 175°C. The modified imidazole shows good latency. After stored for more than 1 month, viscosity of modified imidazole/epoxy system remains unchanged. The longer chain polyether had the better thermal latency these curing agents had. Compared with unmodified imidazole, the novel latent curing agents led to better impact strength for cured epoxy. However, the compatibility between epoxy and latent curing agent will get worse if the molecular weight of polyether unite is over 750.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
EUROPEAN POLYMER JOURNAL
·
2023
·
IF 6
Yanlin Liu,Yueran He,Zhen Yu,Jianfeng Tong,Sican Zhou,Wanding Chen,Zixian Ye,Zhaobin Tang
Thermoset carbon fiber reinforced polymer (CFRP) composites are widely used and in increasing demand in composites industries. Among them, CFRP with one-component epoxy matrix can optimize the preparation process. However, high-value carbon fiber (CF) is difficult to recover and no cases of latent CFRP with CF recyclability have been reported. In this study, long aliphatic chains were innovatively introduced into amino acid type latent curing agents to improve the latent performance and the solubility in organic solvents. The latent performance of curing agents improved with the increase of chain length due to the difficulty in proton transfer of ammonium ions along to the long chain. The latent curing agent derived from 1,10-diaminodecane exhibited good solubility in ethanol and good compatibility with epoxy monomers, making it had the potential for industrial use in the preparation of CFRP. Moreover, amide bonds in the synthetic amino acid were prone to form hydrogen bonds to improve the thermal and mechanical properties of cured resin, while ester bonds in the amino acids imparted the resin with degradability in alkaline environments, thereby endowing CFRP with CF recyclability without damaging surface morphology and chemical structure. This work will open a door for the recycling research of latent CFRP.
研究领域:
材料科学
·
复合材料工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2022
·Vol. 139
·期 41
·e52980
·
IF 3.057
Siyao Zhu,Tongtong Zheng,Fan Li,Li Wang,Qiuran Jiang,Yi Wei,Wanshuang Liu
In this study, a latent imidazole hardener (CPI) for epoxy resins was synthesized through the nucleophilic substitution reaction between 2-methyl imidazolium (2MI) and hexachlorocyclotriphosphazene (HCCP). The chemical structure of CPI was characterized by Fourier transform infrared, 1 H NMR, and 31 P NMR. Curing kinetic studies (Kissinger and Ozawa methods) manifest that epoxy systems cured by CPI show higher apparent activation energy and curing temperatures than those cured by 2MI. Compared with 2MI, CPI shows distinctly improved thermal latency toward epoxy groups at both room temperature and 80°C, owing to the steric hindrance and electron-withdrawing effects of the introduced cyclotriphosphazene group. The results of dynamic mechanical analysis (DMA) and three-point bending tests indicate that the epoxy resins cured by CPI exhibit higher glass transition temperatures and comparable flexural properties in comparison to the corresponding epoxy resins cured by 2MI. As expected, the epoxy resins cured by CPI also show improved flame retardancy ascribed to the introduction of phosphorus and nitrogen elements. Finally, the optimized CPI/epoxy system was used as the polymer matrix to fabricate carbon fiber reinforced composites (CFRCs), and the resulting CFRCs show superior mechanical performance compared with the CFRCs based on the 2MI/epoxy system.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2021
·Vol. 139
·期 14
·51911
·
IF 3.125
Wei Wei,Haolan Gou,Xin Sun,Xiaoma Fei,Xiaojie Li,Xiaoya Liu
One-component epoxy systems with long shelf life during storage or transportation, while high curing reactivity during molding as well as satisfactory mechanical and thermal performances after curing, are extremely essential for industrial application. Herein, we used salicylaldehyde and o -phenylenediamine to synthesize 2-(2′-hydroxyphenyl)-1 H -benzimidazole (HPBI), an imidazole derivative with an intramolecular hydrogen bond between the phenolic hydroxyl group and the pyridine-type nitrogen atom of imidazole ring, and further employed HPBI as a thermal latent curing accelerator for epoxy/phenolic resins. The intramolecular hydrogen bond endowed HPBI with inert activity toward resins at room temperature, making the one-component resin system a long-term storage stability (21 days of shelf life at 30°C). Once rising the temperature to a high degree, a rather high activity of HPBI to accelerate the curing process of epoxy/phenolic resins. It was attributed to the effective release of high activity of the pyridine-type nitrogen by breaking the intramolecular hydrogen bond at high temperature. In addition, the resulted thermosets from HPBI also possessed the comparable T g (>130°C, determined by DMA) and thermostability ( T d-5% > 380°C) with that from common curing accelerators. Therefore, HPBI was proved to be a promising thermal latent curing accelerator applied in electronic packaging field.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULES
·
2024
·
IF 5.1
Falin Li,Yi Wang,Qiu Wang,Binbo Wang,Shuai Du,Fengyuan Zhang,Songqi Ma
This work discloses a new strategy based on dynamic cross-linking chemistry to achieve advanced one-component thermosets combining ultralong storage life and fast cross-linking. One-component thermosets containing resin and cross-linker in one pot have the features of simple operation, stable quality, and low waste; however, an urgently needed one with long storage life at room temperature and fast cross-linking at medium–low temperatures (≤130 °C) remains an enormous challenge. Herein, we innovatively propose a strategy of dynamic cross-linking and controlled dissolution to address this issue. As an example, a dynamic cross-linked cross-linker (DCC) is synthesized via Diels–Alder reaction to hide the high activity of a commercial amine-type cross-linker. A one-component thermoset from a DCC and a commercial diepoxy monomer can be stored for an ultralong time at room temperature and cross-linked rapidly below 130 °C. Moreover, the DCC can also serve as a latent accelerator for epoxy/anhydride thermosets with the same storage life as the control system with no accelerator at room temperature and fast cross-linking at elevated temperatures. This work is beneficial for promoting the application of dynamic cross-linking chemistry and meeting the urgent need for advanced one-component thermosets in the fields of advanced composites, coatings, electronic packaging materials, automotive and electronic adhesives, etc.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）