| Purpose:This experiment is to add different mass fraction of graphene oxide(GO)to acrylic self-curing soft lining materials,and test its mechanical properties,water absorption and solubility before and after thermal cycling,so as to observe whether different content of graphene oxide can improve the related properties of self-curing soft lining materials and delay aging,and analyze the action principle according to the observation results of scanning electron microscope.It provides a new research idea for the application of carbon nano materials in soft lining materials.Method:After ultrasonic dispersion,graphene oxide(GO)powder was added to the self-curing soft lining material according to the mass ratio of 0%,0.5%,1%,1.5% and2%.The soft lining material without graphene oxide powder was used as the blank control group,and the other groups were the experimental groups.After full mixing,it was added to the pre-prepared PTFE mold according to the relevant national standards,and the test pieces with different specifications and sizes of relevant test items were made.(1)Shore hardness: 36 mm × 15 mm × 6mm standard specimens were made according to GB/T 531-1992,each group of 12,a total of 60;(2)Tensile strength:according to GB/T 528-2009,we made dumbbell shaped standard specimens,12 in each group,60 in total;(3)Bond strength: 120 samples of 50 mm × 10 mm × 3mm thermosetting PMMA base resin were made,and 10 mm × 10 mm × 2mm soft lining materials with different mass ratios of GO were filled between the two resin blocks,then pressed and solidified;(4)Water absorption and solubility: 60 specimens with a diameter of 25 mm and a height of 3mm were made,12 in each group.After the specimens were fully solidified and formed,all the other specimens were soaked in artificial saliva at 37℃ and taken out for use after 24 h,except those tested for water absorption and solubility.The specimens of each group were divided into two groups:before the thermal cycling and after the thermal cycling.The hardness of the samples before the thermal cycling was tested by LX-A shore hardness tester,the tensile strength and bond strength were tested by universal testing machine.The water absorption and solubility of the materials were tested after soaking in artificial saliva for 7 days,14 days and 28 days.The dispersion of different content of GO powder in the self-curing soft lining material was observed by SEM.The specimens in the after thermal cycling group were put into the hot and cold cycle apparatus for 5000 times,and then the shore hardness,tensile strength,bond strength,water absorption and solubility were tested.The fracture surface morphology of the specimens before and after the thermal cycling was observed by SEM.By comparing the experimental groups and the control group,and comparing the performance before and after thermal cycling,we observed whether different content of GO could improve the related properties of the self-curing soft lining materials and delay aging,which provides a new research idea for the application of carbon nano materials in soft lining materials.Result:1.Dispersion of GO under SEMA specimen that was completely broken in the tensile test was randomly selected from each group.The results of SEM showed that the surface of the control group was smooth,and the GO powder in 0.5% GO group was more evenly dispersed.However,significant agglomeration phenomenon could be observed in 1.5% GO and 2% GO groups.It can be seen that when GO content exceeds a certain range,its dispersion in self-curing soft lining material is poor.2.Effect of GO on mechanical properties of soft lining materialsThrough the analysis of performance test results,with the increase of GO content,shore hardness showed a trend of increasing,compared with the control group,there were significant differences(P<0.05).With the increase of GO content,the tensile strength showed a downward trend,compared with the control group,except 0.5%GO group,there was no significant difference(P>0.05),the other groups had significant differences(P<0.05).With the increase of GO content,there were no significant differences in bond strength between the experimental groups and the control group(P>0.05).3.Effect of GO on water absorption and solubility of soft lining materialsCompared with the corresponding control group in the same soaking time,except the water absorption of 0.5% GO group on 7 days,0.5% GO group and 1% GO group on 14 days,there were no significant differences(P>0.05),the water absorption and solubility of the other groups were higher than the control group,with statistical significances(P<0.05).In the same group,with the increase of artificial saliva soaking time,the water absorption and dissolution rate increased except for individual groups.4.Effect of GO on mechanical properties of soft lining materials after the thermal cyclingAfter the thermal cycling,with the increase of GO content,shore hardness showed a downward trend,compared with the control group,except for 0.5% GO group,there was no significant difference(P>0.05),the other groups had significant differences(P<0.05).With the increase of GO content,the tensile strength increased first and then decreased.When GO content was 0.5%,the tensile strength was the highest,but the tensile strength of other groups decreased significantly compared with the control group(P<0.05).With the increase of GO content,the bond strength increased first and then decreased,reaching the maximum value of 1.04 ± 0.12 MPa in the 1% GO group.There was no significant difference between the 1.5% GO group and the control group(P>0.05),while there were significant differences between the other groups and the control group(P<0.05).5.Effect of GO on water absorption and solubility of soft lining materials after the thermal cyclingThe results show that the water absorption and solubility of GO modified soft lining materials change obviously after the thermal cycling.With the increase of GO content,the water absorption and solubility increased respectively.However,compared with the control group,there were no significant differences in water absorption of the 1% GO group and the 2% GO group(P>0.05),the other groups had statistical significances(P<0.05).6.Comparison of mechanical properties of materials before and after thermal cyclingIn the same GO content group,the shore hardness of each group was significantly increased after the thermal cycling,with significant differences(P<0.05).The tensile strength of the control group decreased significantly after the thermal cycling(P<0.05),but there was no significant difference in the tensile strength of the experimental groups before and after thermal cycling(P>0.05).The bond strength of each group decreased significantly after the thermal cycling(P<0.05).From the change range of values before and after thermal cycling,with the increase of GO content,the change range of shore hardness in each group decreased,indicating that the loss of hardness decreased.The tensile strength of the experimental groups had no significant change before and after thermal cycling.In addition,when the GO content was 0.5% and 1%,the change range of bond strength before and after thermal cycling was small,indicating that the loss of bond strength in these two groups was less.7.SEM observation of fracture surface before and after thermal cyclingA specimen that was completely broken in the tensile test was randomly selected from each group.After spraying gold,the change of fracture surface characteristics before and after thermal cycling was observed under SEM.GO is dispersed as flake particles on the fracture surface of the materials,which is not easy to distinguish.After the thermal cycling,the structure of the material is partially lax,the number of pits is increased,and the morphology is irregular.Conclusion:1.It can be concluded that the addition and amount of graphene oxide affected the mechanical properties,water absorption and solubility of acrylic self-curing soft lining materials.In the range of 0%-2%,with the increase of graphene oxide content,the shore hardness of the composites increased,the tensile strength decreased,the water absorption and solubility increased,but the bond strength had no significant change.2.From the short-term effect,the addition of graphene oxide can reduce the loss of shore hardness,tensile strength and bond property to a certain extent,but it had adverse effect on water absorption and solubility.3.In the range of mass ratio of this experiment,the best addition of graphene oxide was 0.5%,at this time,the properties of the composite were better,and from the short-term effect,the loss of tensile strength and bond strength were less,which can delay the aging of the material properties. |
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