| Water-borne polyurethane(WPU)is a kind of widely used materials in the field of water-borne polymers.Compared with the traditional solvent-based polyurethane(WPU),WPU has the advantages of cleaner,safer and more efficient production and application,which is in line with the development trend of green chemistry and the social needs of environmental protection.In order to further improve the comprehensive properties of waterborne polyurethane,hybrid modification of WPU with various organosilicon is one of the hot research fields in the field of WPU.In this paper,hydroxypropyl polydimethylsiloxane(HP-PDMS)was introduced into the copolymerization system of isoflurone diisocyanate(IPDI)and polycarbonate diol(PC2000).DMBA was used as hydrophilic monomer.WPU emulsion with good dispersion stability and excellent properties such as water resistance and mechanical properties was prepared by introducing crosslinking structure with small molecule trifunctional monomer and silane coupling agent.The effects of copolymers composition and synthetic variables on the stability,structure and properties of emulsion films were studied.The main contents of this thesis are as follows:(1)Three different methods were designed to prepare HP-PDMS copolymerized modified WPU.Through the study of emulsion process,particle size and storage stability,the preparation method was optimized.By two-step feeding method,under the conditions that the dosage of DBMA is 5 wt%and the proportion of HP-PDMS is from 10wt%to 30wt%and the content of solid is 30%,the particle size WPU emulsion with the number of average diameter of 50nm can be obtained.(2)The self-crosslinking modification of PDMS modified WPU system was carried out by sealing end reaction.It was found that the sealing reaction efficiency of 5-hydroxy2-pentanone was low,and its introduction would lead to the instability of WPU emulsion.The monomers ?-aminopropyltriethoxy silane(KH550)have excellent sealing effect on the PDMS polyurethane prepared in this paper.The stable modified PU emulsion can be prepared when the dosage of DBMA is 5 wt%and the dosage of HP-PDMS is between 10wt%and 30wt%and the dosage of KH550 is between 3wt%and 15wt%.The influence of the introduction of alkoxy silane structure and its self-crosslinking reaction on the properties of the emulsion films were studied.The behavior of microphase separation in the films was characterized by FTIR and dynamic mechanical analysis(DMA).It is found that the WPU film with good properties can be obtained when the dosage of KH550 is between 6wt%and 9wt%,with 20wt%HP-PDMS,and it is found that heat treatment has a great effect on the decrease of water absorption of the film.The effects of emulsifying temperature,neutralization degree,dispersion power and solid content on the particle size and stability of WPU emulsion were systematically studied.It was found that the introduction of organosilicon structure had a significant effect on the self-emulsifying ability and emulsion stability of WPU.The results show that the response of emulsion particle size to storage time,temperature,neutralization degree,dispersion power and so on is obviously different with the composition of silicon.(3)In order to further improve the crosslinking efficiency in WPU film formation,further improve the mechanical properties of the film and reduce water absorption.In this paper,a moderate amount of trimethylolpropane(TMP)was added to the synthesis of silicon-containing self-crosslinked WPU,and the effects of TMP copolymerization on the emulsion properties and film properties were studied.The results showed that when the amount of TMP was controlled from 0.5 wt%to 3 wt%,the introduction of TMP had no significant effect on the dispersing process of WPU,but the tensile strength and water absorption of the emulsion film at room temperature crosslinking and thermal crosslinking were significantly improved. |
PDF Full Text Request