| Epoxy resin adhesive(EP adhesive for short)is a kind of widely used engineering adhesives,it has the advantages of good adhesive property,low curing shrinkage rate,good chemical stability and excellent heat resistance,etc.It has been developed rapidly since the commercial production of EP adhesive had been applied in American industry in 1947.EP adhesive is widely used,but if it has not to be toughened and modified at first,then its cracking resistance is very poor after curing,the texture is hard and brittle,and the impact strength is low.These deficiencies limit the application of EP adhesive in some areas,so strengthening its toughening modification,broading its application field and improving its application value has great significant.This paper studied the one-step preparation of nano CaCO3 whisker in alcohol-water mixed system using intermittent bubbling carbonation method in the ordinary gravity field,and the modification of CaCO3 whisker,and finally using the modified nano CaCO3 whisker as an epoxy-polyamide EP adhesive toughening filling material.The effect of improving the mechanical properties of EP adhesive was explored.The main contents and conclusions are as follows:Using laboratory selfinade carbonization reactor which has a reflux function and intermittent bubbling carbonation method to explore the synthesis process conditions of calcium carbonate whisker respectively in pure water system,pure methanol system,ethylene gloycol-water mixed system,glycerol-water mixed system and methanol-water mixed system.Ultimately in methanol-water mixed system,under the process conditions of Ca(OH)2 initial slurry concentration was 3.5%,CO2 and N2 flow rate were 100 mLˇmin-1 and 200 mLˇmin-1,carbonization temperature was 75 0C,H3PO4 dosage was 2%,RVW/VA=5:1 and the mechanical stirring rate was 800 rˇmin-1,we synthetised the CaCO3 whisker which the average diameter was 195.18 nm and aspect ration was about 21.Respectively using aluminate coupling agent and boric acid ester agent on the surface dry modification of CaCO3 whisker,characterizing the modification effect by the main indexes of activity degree and oil absorption.On the basis of regarding the amount of modifying agent,modification temperature,modifica-tion time and mechanical stirring rate as experimental single variable in turn,designing the L9(34)orthogonal experiments to get the optimum process conditions of nano CaCO3 whisker modification by aluminate coupling agent and boric acid ester coupling agent.The optimum process conditions of aluminate coupling agent modified nano CaCO3 whisker were as follows:the amount of modifier was 3.5%,modification temperature was 90 0C,modifica-tion time was 25 min,mechanical stirring rate was 600 rˇmin-1.While the optimum process conditions of boric acid ester coupling agent were:the amount of modifier was 3.5%,modification temperature was 70 ?,modification time was 30 min,mechanical stirring rate was 600 rˇmin-1.After modification,the activity degree of CaCO3 whisker was 100%,and the oil absorption value was low to 27.12 gˇ100-1,the modification effect was good.Using the activity CaCO3 whisker as toughening filler,making it complex with pure epoxy resin through a three roller grinding machine,and finally adding curing agent to get the EP adhesive composive material.In this paper,the activity nano CaCO3 whisker modified by aluminate coupling agent toughened EP adhesive the best,the amount of activity CaCO3 whisker is 4%(calculated on the basis of pure epoxy quality).Compared with the blank sample without toughening,the tensile strength of EP adhesive composive material was increased by 57.35%,the compressive strength was increased by 58.70%,the bending strength was increased by 58.70%,and the non notched impact strength was increased by 44.40%.With the help of SEM,we observed the fracture appearances of EP adhesive blank sample and composive sample,It was found that fracture morphology of blank sample was smooth and regular,while it turned to be rough and covered with complicated and interlaced silve grain when it was toughened.This phenomenon indicated that the material changed from brittle fracture to plastic fracture,which meaned the EP adhesive has been successfully toughened. |
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