Study On The Synthesis Of Carbamate Compounds And Their Modification On Epoxy Resin

Bisphenol A epoxy with low molecular weight has been used in coating,adhesive,potting,casting and compound material fileds because of its small molecule,good flowability at room temperature and convenient operation with differnet hardeners,accelerators and various additives.It posseses excellent formulation designability and processibility.It can be found that rheology control and toughness improvement are the basic tech-requiresments in its various applications.However,the control ways on the rheological behavior of formulated epoxy resin being used now are all based on the scope of“Up to Bottom”.These methods are always inefficient and costful,which makes the application of epoxy resin limited somewhat.But the current researches still mostly focus on the ways based on the original powders,like surface modification for silica and using additives for powder materials.Toughning is an eternal topic for epoxy application.It is always the hot research topic since the commercial production of epoxy resin.The topic numbers on this field can be about more than 50%.The commonly reported methods on toughning are to use flexibility agents,polymer rubers,cage-silica,epoxy resins and hardeners with high molecular weight.The hot research method is base on IPN idea to combine epoxy system with PU and organic silicone.But these methods all result in the worsening of the thermal behaviors of cured resin and their processing are not so convenient.Some of them are considerable costly and lack of operability.Recently,the toughning researchs focus on using thermalplastical materils.But this method has not been widely applied in practical applications because of the high melting temperature of applied thermalplastical materils.Therefore,toughing epoxy polymer is still the hot research topic within recent ten years.In this work,we tried to control the rheology behaviors of epoxy resin by the means of self-assembly of carbamates materials and to tough the cured epoxy resin through the reaction induced phase separation of carbamates materials in epoxy/amine system based on the strategy of“Bottom to Up”.Strong H-bonding donor-acceptor of-NHCOO-is introduced into the carbamates with some end-alkyl chains which are good for van de Waals interaction by the reaction of-NCO and-OH.The contribution of these two intermolecular interactions is controlled by managing the length of alkyl chains and-NHCOO-numbers.The rheology behaviors of formulated epoxy resin are designed to be controlled by the self-assembly of different carbamates.And thermal reversibility of rheology behaviors is caused by the phase change performance of the systhesized carbamates.Moreover,-NHCOO-is introduced into PTMEG based carbamates to manage the intermolecular interaction and intramolecular interactons between PTMEG and PTMEG,PTMEG and other molecules for their reaction induced phase separation in epoxy/amine system.Cured resin is toughed by the micro-phase induced by cured reaction.There are four sections in this work.1)Synthesis of dicarbamates and modification research on bisphenol A epoxy resinDicarbamates?HB?with two end alkyl chains were synthesized by reaction of HDI and different monohydroxl alcohols with different chain length.FT-IR was used to tell the effect of chain length of end alkyl chains on the intermolecular interactions between HB itself and in epoxy matrix.Polarized optical microscope?POM?was used to record the crystallizaiton morphologies of different HB and HB in epoxy resin.DSC was used to measure the thermal performance on the phase change of HB.Rheometer was used to measure the rheology behaviors of epoxy composites with different HB at different contents and temperatures.Thermal test was done to observe the thermal reversibility of epoxy composites containing HB.The cured performance with HB was tested and thermal shock tests were done.SEM was used to observe the morphology of HB in cured resin.The results were summarized as following.HB is phase change material which can be heated to be liquid and back on the solid after cooling down.There are two main intermoleculare interactions of H-bonding and van de Waals interactions in HB itself and in epoxy matrix.The different contribution of H-bonding and van de Waals is cause for the different crystallization morphology of HB and HB in epoxy which resultes in the better rheology behaviors of shear-thinning than common fumed silica of RY200.The rheology behaviors of epoxy composites with HB are thermal reversible because HB possesses phase change performance.Epoxy resin results in the different morphology of self-assembling of HB in epoxy from HB itself.HB is proved good for toughing the cured epoxy resin and subsequently good resistance for thermal shock.2)Synthesis of tricarbamates and modification research on bisphenol A epoxy resinTricarbamates?TB?with three end alkyl chains were synthesized by reaction of HTI-100and different monohydroxl alcohols with different chain lengthes.FT-IR,POM,XRD,DSC,rheometer,impact strength tester,universal test machine and SEM were used to characterize the molecular interaction,crystallization morphologies,rheological behaviors,thermal performances,cured mechanical strength and Tg for all samples,respectively.The results were summarized as following.TB is phase change material and there are two main intermoleculare interactions of H-bonding and van de Waals interactions in TB itself and in epoxy matrix.C₃ structure introduced into TB causes the spherulite crystallization morphology of TB and TB in epoxy resin which is different from that of HB,which resultes in the better rheology behaviors of shear-thinning for its epoxy composites than those with HB.The rheology behaviors of epoxy composites with TB are thermal reversible because TB possesses phase change performance.TB is proved good for higher impact strength without sacrificing Tg.3)Synthesis of tetracarbamates and modification research on bisphenol A epoxy resinTetracarbamates?HPB?with two end C₁₆ alkyl chains were synthesized by reaction of HDI and C₁₆ alkyl alcohol.FT-IR was used to characterize HPB and its epoxy composites.FT-IR,POM,XRD,DSC,rheometer,impact strength tester,universal test machine and SEM were used to characterize the molecular interaction,crystallization morphologies,rheological behaviors,thermal performances,cured mechanical strength and Tg for all samples,respectively.The results were summarized as following.HPB is phase change material.The flexibale PTMEG induces the poorer phase change performance of prepared HPB and the weaker intermolecular interactions including H-bonding and Van de Waals'force.The weak interaction of alkyl chains and PTMEG chains with epoxy resin causes the different self-assembling morphology of particle of HPB which makes the epoxy composites possess the similar rheology behaviors of shear-thinning as those with common fumed silica of RY200.The rheology behaviors of epoxy composites with HPB is proved thermal reversiblity because HPB shows phase change performance.HPB is proved good for keeping Tg due to the phase separation.4)Synthesis of tetracarbamates of PTMEG and modification research on bisphenol A epoxy resin.Tetracarbamates of PTMEG with two end PPG and glycidyl ether chains were synthesized by two steps of synthesizes,first to introduce-NCO as the end group of PTMEG,second for the reaction of modified PTMEG with PPG and glycidyl ethers.This section focused on the study on the viscoelastical behavior of the composite systems of PTMEG/YN1828/TETA and PTMEG tetracarbamates/YN1828/TETA,respectively.The results were summarized as following.Reactio induced phase separation happened in the cured resin system with pure and modified PTMEG.The introduction of strong-NHCOO-group and PPG and glycidyl epoxy chain which are compatible with bisphenol A epoxy was proved helpful for controlling the sperated phase morphologies like phase size and size distribution.Seperated phase size was able to be controlled by managing the content of modified PTMEG and curing temperature,which resulted in the different cured performances.The forming of microstructure by phase separation was proved be good for increasing the impact strength.And thermal shock test results showed that modified PTMEG was better than F-100 and CTBN-13 on improving the thermal shock resistance of cured resin.The synthesized carbamates in this work possess the good phase change behaviors which endows epoxy composites with carbamates the good and controllable rheological behaviors of shearing thinning with good thermal reversibility.Meanwhile,the impact strength of modified epoxy systems with carbamates can be effectively improved without sacrificing other cured performances through the reaction induced phase change by changing the molecular structures of carbamates,which results in the perfect crack resistance of modified YN1828/TETA systems with carbamates.This provides a new and controllable modifying technical method for managing the rheological behavior of liquid epoxy resin with high productivity.And this also expands the application of toughning technology of reaction induced phase separation in common liquid epoxy field.In a summary,these carbamates materials can be widely used in epoxy applications in the furture based on the above excellent performances.