Study On The Preparation And Properties Of The Thiourea Modified Diethylenetriamine

Epoxy resin is to be claimed the fast growing synthetic resin product in our country. It has been widely used in civil construction, ship production and other fields. Curing agent is a essential constituent for the application of epoxy resins and determines the performance of epoxy resins in a large degree. Therefore, epoxy resins must be used together with curing agents to obtain the best performance of fast curing, good bonding properties, high temperature resistance, solvent resistance, good mechanical properties and corrosion etc. At the earliest time, the widely applied curing agent for epoxy resins was the polyamine curing agent, which has been proved having many disadvantages such as having a certain degree of toxicity, poor consolidation for epoxy resins at room temperature, poor mechanical properties without reaching the requirement for practical application and poor temperature resistance. So the traditional polyamine curing agent needs to be modified to overcome the shortcomings.As diethylenetriamine, a widely used polyamine, causes many disadvantages when used for curing epoxy resins, this paper designs to introduce thiourea to modify diethylenetriamine. A new type of epoxy curing agent was synthesized through introducing the new functional groups on diethylenetriamine. When this new epoxy curing agent was applied for curing epoxy resins, the obtained product had many enhanced performance such as viscosity, toughness, mechanical performance and high temperature resistance. The detailed content as follows.The new type of thiourea modified diethylenetriamine curing agent was prepared with thiourea and diethylenetriamine as raw materials and controlling of the experiment conditions. The structure of the curing agent was characterized by HPLC and NMR. In order to determine the curing technology, thiourea modified curing agent and epoxy resin E-51 was chose to conduct curing experiments. Factors of material proportion, temperature, time were measured by single factor experiments. The results proved that the thiourea modified curing agent had an optimum physical index, operability and performance when factors was chose as follows: material proportion of thiourea to diethylenetriamine was 1.5 : 1, temperature was 130 oC, time was 3.0 h.Scale-up experiments were also proceeded refer to the data obtained by the lab scale experiments. Feed method was investigated in detail and technological process was well designed in the scale-up process. Optimum rectification measures were proposed for the potential safety hazard. Detailed operational procedure was drawn up to guarantee the experiments. The influence of the ratio of warming and cooling on the property of the products was studied. At last, optimum solution refer to the byproducts produced by the experiments were proposed.Thermal performance was tested in the curing process. The effect of the curing agent dose and type on the performance of the curing product was studied through the testing of tensile strength, bending strength, impact resistance, high temperature resistance and water absorption ability, etc. The testing results proved that the curing process was milder and easier to operation and the curing product was harder to crack when thiourea modified curing agent was used instead of diethylenetriamine curing agent. In addition, the curing product undertook ductile fracture under impact when thiourea modified curing agent was used, which indicated that the toughness of the curing product was enhanced. Even more exciting, after curing agent modification, the obtained curing product owned better elongation at break, strength, impact toughness and so on.