| High Resilience Polyurethane Foam is a kind of polymer with light weight,excellent mechanical strength,high resilience,low hysteresis loss and strong shock absorption.It is widely used in automobiles,furniture,packaging and medical equipment.However,due to the depletion of petrochemical resources and the non-degradation of petroleum-based materials,more and more attention has been paid by researchers.The use of renewable vegetable oil polyols to prepare high-rebound polyurethane flexible foams was important and difficult research at home and abroad.But,the current use of vegetable oil polyols to prepare high resilience polyurethane flexible foam still has the following problems:(1)Recently,thiol-ene modification was a convenient method for preparing vegetable oil polyols among many vegetable oil modification methods.However,the thiol-ene reaction was a free radical reversible reaction,and the high double bond conversion rate needs to be achieved in a high temperature environment,resulting in formation of by-products and a low raw material utilization rate.(2)The use of vegetable oil polyols to completely replace petroleum-based polyols to prepare high-rebound polyurethane foams has poor properties such as resilience and static compression set.In view of the above scientific problems,the thiol-ene click reaction mechanism and the stepwise dropping method were considered to efficiently convert soybean oil into soybean oil polyol(MESO)at room temperature.Further,polyether polyol(L2000)was partially replaced by the self-made soybean oil polyol to prepare high resilience polyurethane flexible foam.As the amount of MESO added,the performance change of high resilience polyurethane flexible foam and the degradation characteristics were studied.The specific research content of this paper is as follows:Firstly,Fourier Red Transition(FT-IR)and Nuclear Magnetic Resonance(NMR)were applied to characterize the molecular structure of the synthesized vegetable oil polyol,and it was confirmed that mercaptoethanol was successfully introduced into the soybean oil molecular chain.The double bond conversion rate and the degree of functionalization were quantitatively calculated using the NMR H-spectrum(~1H NMR)area integration method.As the[Thiol]/[ene]ratio gradually increased,the reaction rate steadily increased.The hydroxyl functionalization degree was increased first,and the degree of functionalization was maximized when the[Thiol]/[ene]ratio reached to 4/1,It has been observed that with the prolong of the reaction time,the reaction rate gradually increased,and the degree of functionalization initially increased and then decreased.When the reaction time was 12 h,the degree of functionalization reached the maximum,meanwhile,the[Thiol]/[ene]ratio was 4/1.In addition,the conversion of mercaptoethanol and soybean oil double bond reached 99%,89%,respectively.The viscosity of the soybean oil polyol was measured by digital rotational viscometer and the obtained viscosity under the optimum process conditions was 3226 m Pa·s.The hydroxyl value of the soybean oil polyol was measured by the phthalic acid esterification titration method and the hydroxyl value of 230 mg KOH/g can be achieved under the optimum conditions.Secondly,the synthetic soybean oil polyol was replaced by petroleum-based polyol to prepare high resilience polyurethane flexible foam.The effect of addition certain amount of MESO on the foam structure and properties was studied.The preparation of polyurethane foam was determined and the molecular structure of polyurethane foam was characterized by FT-TR.It was observed that in the foaming rate test,the degree of foaming gradually decreased with the replacement ratio of MESO.In addition,the cross-linking degree test showed that the replacement ratio of MESO was gradually increased;consequently,the degree of cross-linking of the system was increased.Furthermore,the structure of the cell was characterized by scanning electron microscopy(SEM).The results showed that with the replacement ratio of MESO increases,the pore size of the foam decreases,and the opening ratio and quantity is reduced.To get more deep information,the thermal stability of the foam was characterized by thermogravimetric analysis(TGA).Results indicated that with the increase of the replacement ratio of MESO,the thermal decomposition temperature of the high resilience polyurethane foam moved toward the low temperature,which suggested that thermal stability can be improved.The mechanical properties were characterized by 40%compression experiments.The mechanical properties of foams were improved with the increasing the replacement proportion of MESO.The viscoelasticity of the materials was tested by dynamic thermomechanical experiments.The results showed that as replacement ratio of MESO increases gradually,the storage modulus gradually decreases,only one peak of Tg can be observed,and migrated towards the high-end direction,indicating the addition of MESO have not affected the compatibility of the system.As a result,the material processing performance was improved.The material resilience performance was tested by the small ball rebound and static compression permanent deformation test.The results showed that with the increase in replacement proportion of MESO,the instantaneous resilience energy and continuous resilience can be enhanced.Finally,the degradation of high resilience polyurethane foam containing MESO after 30,60 and 90 days of soil burial was studied.The molecular structure of polyurethane foam after soil burial was characterized by FT-TR.The FT-IR spectra described that the hydrocarbons were in the carbamate,fat chain and polyurethane were decomposed.The cross-linking degree and mass loss rate test showed that with the increaseing number of buried days,the degree of cross-linking and quality of the system decreased gradually.The structure of the cell was characterized by SEM.The results showed that as the number of buried days increased,the cells ruptured and the walls of the holes were rough and cracked.The mechanical properties of the cells were tested by 40%compression test.However,the compressive strength decreases with the increase of buried days.Moreover,the viscoelasticity of the material was tested by dynamic thermomechanical experiments,small ball springback and static compression permanent deformation experiments.The results showed that the storage modulus gradually increased with the number of buried days.So the instantaneous resilience and sustained resilience both were reduced.In summary,this paper utilizes the thiol-ene light click reaction mechanism and the stepwise dropping process to efficiently synthesize soybean oil polyol at room temperature,which improves the double bond conversion rate and functionalization degree of soybean oil.At the same time,the influence of reaction time and feed ratio on its conversion rate and functionalization degree was also discussed,which provided a new process for the preparation of vegetable oil polyol by thiol-ene method.Furthermore,the influence of reaction time and feed ratio on its conversion rate and functionalization degree was also discussed,which provided a new process for the preparation of vegetable oil polyol by thiol-ene method.The high-rebound polyurethane flexible foam was prepared by partially replacing the petroleum-based polyol with the self-made soybean oil polyol,and resilience and static compression deformation performance of the products were improved,and the industrial production cost was reduced and the product degradability was improved,which promoted energy conservation and emission reduction,environment protection,and took the road of sustainable development in line with the state. |
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