Study On Controllable Synthesis And Properties Of Vegetable Oil Based Waterborne Polyurethanes

Waterborne polyurethane?WPU?has been one of the hotspots of polyurethane research in recent years because of its environmental protection characteristics as a new type of material using water as dispersant.Introducing hydrophobic segments and making them post-crosslinkable is one of the ways to solve the poor water resistance of WPU.The structure of tung oil?TO?in natural vegetable oil is the ideal raw material to meet this requirement. Converted TO to hydroxylated TO?HTO?,tung oil has potential for valuable uses in the specialty polyurethanes industry,since the HTO,prepared using ester aminolysis,features two primary hydroxyl groups and a long branched hydrocarbon chain containing three conjugated double bonds.By utilizing its two primary hydroxyl groups,HTO can be readily incorporated into thermoplastic polyurethane or WPU compositions,and the long unsaturated hydrocarbon chain it carries can be expected to confer unique properties into WPUs.The thought in the present work is that since polyurethane is a segmented polymer composed of hard and soft segments.HTO can be confined to either the hard or soft segment structures of final polyurethanes by selection of polymerization sequence.When incorporated into the hard segment,HTO may have a great influence on the regularity of the original?that is,unmodified by HTO?hard segment of the polyurethane.And,if the HTO was introduced into the soft segment of the polyurethane to form the"large soft segment"comprised of the usual macromolecular polyols along with HTO,then the modified chain structure may lead to different phase separation behavior,which may then affect the microstructure and properties of the final WPU.This is an innovation in the basic research of polyurethane,and thus important to provide information about these building blocks and polymer structures,for guiding the design of HTO based WPUs into the future.Therefore,in the present work,two polymerization methods were for the first time used to synthesize a series of WPUs having known HTO structural content locations,in order to explore their intermolecular interactions,phase structure characteristics and properties.The two other hydroxylated vegetable oils?HVO?,including hydroxylated linseed oil?HLO?and hydroxylated palm oil?HPO?with different amounts of double bonds and double bond position,were used to prepare HLO and HPO based WPU for comparison.Polypropylene oxide?PPG?,with molecular weight similar to HTO,was also used to replace HTO for preparing control samples.All the HVO based WPUs were prepared by using polytetrahydrofuran?PTMG?as macromolecule polyol,dicyclohexylmethane diiscyanate?HMDI?and isophorone diiscyanate?IPDI?as diisocyanate,dimethylolpropionic acid?DMPA?as water-borne chain extender and ethylenediamine?EDA?as chain extender.Various instruments including FTIR,NMR,MS,DSC,DMA,Instron tester and AFM etc were employed to study the structure,the intermolecular interaction and mechanical properties.The main work and conclusions are as follows:1.HTO,HLO and HPO with different amounts of double bonds were obtained by aminolysis of vegetable oil.The target products with single structure were isolated and PUrified.The structure was confirmed by FTIR and NMR.The mechanism of double bond crosslinking reaction was studied.The opening speed of double bond under aerobic condition was HTO> HLO>HPO.With the increase of drying agent dosage,the time needed for HTO to open conjugated triene bond decreased,and gradually slowed down when drying agent content was3.99%.2.Model compounds display unique spectral characteristics.The FTIR bands and NMR resonance peaks assigned in the prepared samples provide a reliable database and starting point for investigating the relationship between hard segment structure and the crystallization and hydrogen bonding?H-bonding?behaviour in more complex-segmented PU compositions.3.HTO,containing a long branched hydrocarbon chain and conjugated double bonds,has been successfully incorporated into segmented APUD.At the same time,PPG,with similar molecular weight,has also been introduced into APUD to replace HTO in control samples, which highlights not only the structural characteristics of the HTO-APUD,but also the changes in H-bonding interactions and hard-soft segment compatibility,caused by incorporating HTO exclusively into either the hard or soft segment of the polymer.4.When the R value of the prepolymer was 1<R<2.5,the emulsion was stable.Temperature has little effect on the storage stability of HPO.When the HTO content is less than21%,the storage stability of WPU is better.When the DMPA content is in 4%<DMPA<10%,WPU has better water absorption and storage stability.5.The mechanical properties of HMDI based polyurethane are better than IPDI based polyurethane when HTO was incorporated into hard segment,while the mechanical properties of IPDI based polyurethane are better than HMDI based polyurethane when HTO was introduced into soft segment.The structure of the diisocyanate determines the height of the DMA dissipation peak?Tgh?,while the molecular H-bonds determine the changes in hard-soft compatibility resulting from different HTO locations in the polymer molecule.6.Confining HTO incorporation only into the large soft segment will leave the regularity of the hard segment undisturbed,thus the hard segment T_gh remains relatively high.Incorporating HTO into the hard segment causes a significant decrease in T_gh.Findings of this study indicate that the location of HTO incorporation has a bigger influence on the T_gh of the studied compositions than does the structure of the diisocyanate;7.The sequence of hard segment T_gh when HTO was incorporated into APUD is HTO-HMDI-WPU>HTO-IPDI-WPU>PPG-HMDI-WPU The sequence of soft segment T_gs when HTO was incorporated into APUD is PPG-HMDI-WPU>HTO-HMDI-WPU>HTO-IPDI-WPU8.The amide ? and amide ? bands in the infrared spectrum can be used as an important supplement to the carbamate carbonyl and urea?C=O bands to study the H-bonding interaction between hard segments as well as between hard and soft segments of APUD.9.The ether linkages present in PPG contribute additional H-bond receptors when incorporated into either the hard or soft segments,thus significantly improving the H-bonding strength between these segments,which significantly improves phase compatibility?reduces phase separation?of the PPG-APUD polymers.10.When HPO was introduced into the hard segment,its WPU heat resistance was generally higher than that in the soft segment,and the maximum decomposition temperature was also different.When HLO was added into the WPU soft segment,the maximum decomposition temperature decreased with the increase of HLO content,while when HLO was added into the WPU hard segment,the maximum decomposition temperature did not change much with the increase of HLO content.When HVO was incorporated into the WPU soft and hard segments,thermal decomposition can be roughly divided into three stages.In the first stage,polyurethane was degraded in the range of 190-250?,mainly in the hard segment;in the second stage, polyurethane was degraded in the range of 250-380?,mainly in the soft segment;and in the third stage,in the range of 380-500?,mainly in the carbon-carbon bond of polyurethane molecular chain.The average volume diameter of WPU is smaller when HVO was in soft segment than that of WPU when HVO was in hard segment.The mean volume and particle size of PPG based WPU were smaller than that of HVO based WPU when PPG or HVO are in both soft and hard segments.This study is of great significance to enrich and develop the understanding of HVO based WPU.In addition to academic innovation,it can provide basic theoretical data for the further development of HVO based WPU,so as to promote the development and application of new WPU materials in China...