Study On Synthesis, Characterization And Application Of EO/PO Random Copolyethers

Copolymerization between ethylene oxide (EO) and propylene oxide (PO) could be initiated by alcohols and the hydrophilic-lipophilic property of resulted copolyethers could be tailored by adjusting EO/PO ratio. After being alkyl-end-capped, EO/PO copolyether would show fine properties of thermostability, chemical resistance, fast wetting, foam-reducing and biodegradation, and then could act as an important nonionic surfactant in a wide application field.In this paper, the attention has been focused mainly on a new system of the propylene glycol initiated EO/PO random copolyethers. Firstly, the polymerization kinetics has been studied and the controlling on copolyether molecular structures was successfully achieved based on the optimization design on the polymerization parameters. The copolyethers have been characterized by means of NMR, FT-IR, etc., and their thermostability, viscosity and surface tension were also tested. Moreover, the influence of molecular structure, concentration, adding of inorganic electrolytes, acids, alcohols and different surfactants on the cloud point (CP) of aqueous solution of random copolyethers has been discussed in detail. Furthermore, some block EO/PO copolyethers were synthesized for the purpose of comparison with the random counterparts. Secondly, the random copolyethers were alkyl-end-capped via Wiliamson method and the factors determining end-capping degree were discussed. The influence of end-capping on the properties of copolyethers as well as the rheology. CP, stability and wetting ability of end-capped copolyether solutions were also studied. Especially, a new one-step polymerization technology of alkyl-end-capped copolyethers has been developed. Finally, an attempt at the application of confected end-capped copolyethers on spinning finish was made, and the thermostability of alkyl- end-capped copolyethers along with their effects on the high speed spinnability of PA66 was discussed. The main conclusions were listed as follows.1. The polymerization rate could be accelerated by increasing the reaction temperature and the catalyst concentration, however, excessively high temperature would also result in the higher unsaturation level and darker color of the copolyethers. Moreover, with the increasing load ratio of EO/PO, the molecular weight (MW) of resulted copolyethers would reach closer to the desired one. After the optimization analysis of reaction parameters, random copolyether could be synthesized from propylene glycol initiated EO/PO mixture under the conditions of catalyst KOH content being 0.25%, temperature being 115℃, and pressure below 0.4MPa, resulting a product with an narrow MW distribution and a colorless appearance.2. The molecular structures of copolyethers impacted heavily on their properties. Generally, the viscosity, surface tension and emulsion ability increased while the thermostability decreased with the increasing EO/PO ratio and MW. However, a long alkyl chain of the initiator would reduce the viscosity and surface tension.3. A low EO content, high MW and high concentration (to some extent) of the copolyethers would result in a low CP. Furthermore, electrolytes, bases and insoluble alcohols would reduce but acids, water soluble alcohols and surfactants would improve the CP.4. With a similar composition, the thermostability of block copolyethers was higher than that of random ones however CP was almost the same.5. The random copolyethers mentioned above have also been alkyl-end-capped with KOH (in both bulk and aqueous solution state) as a catalyst, under which the end-capping degree for both ethyl and butyl could reach over 85%. After end-capping, the thermostability of copolyethers was improved evidently, which was demonstrated by the increased onset decomposition temperature with the increasing end-capping degree. The emulsion ability of ethyl-end-capped copolyether changed little however butyl-end-capped one decreased slightly. With the increscent end-capping degree, the CP and the viscosity of copolyethers would decrease and the temperature effect on viscosity became weaker.6. After the alkyl groups substituting the terminal hydroxyls, the influence of acids, bases and salts on water-solubility of copolyethers decreased and the stability of water solution increased, the wetting ability was also improved. End-capping degree has little effect on the concentration and temperature dependence of rheology except for the slight decreasing of viscosity, especially, the temperature effect on viscosity became weak under a high end-capping degree.7. An end-capping degree of 33% for ethyl group and 31% for butyl group could be achieved from the new one-step polymerization technique for preparing alkyl-end-capped copolyethers.8. Confected spinning finish obtained from alkyl-end-capped copolyethers showed a better thermostability and could reach to entire decomposition more quickly under a same heating rate.9. Confected spinning finish obtained from 33% ethyl-end-capped copolyethers could promise better high speed spinnability to PA66 than hydroxyl-ended ones, however, the as-spun fibers obtained from each kind of finish could satisfy the standard quality demands.