Study On New Bonding Systems Of UHMWPE And Influences Of Tribological Load On Their Bonding Properties

To develop bonding-type tribological composite materials with ultra-high molecular weight polyethylene(UHMWPE)for industrial application,it is important to solve a key problem of reliability of adhesion between UHMWPE and metallic materials.According to the bonding theory,the dissertation designed three kind of bonding system for UHMWPE,which is one of the low surface energy polymers,to search a way to bond UHMWPE reliably.They were:① a bonding system,in which man uses common commercial adhesives to bond UHMWPE pretreated by special chemical agent at room temperature,② a bonding system,in which man uses 2-cyanoacrylate adhesive and its special self-contained primer to bond UHMWPE and③ a bonding system,in which man uses a kind of special adhesive,that can self-etch interfaces of UHMWPE at that time of bonding,to bond UHMWPE.The dissertation has developed a kind of adhesive primer for treating UHMWPE at room temperature,which optimized formula contains 100wt.%methyl ethyl ketone peroxide and 6wt.%ferrocene.After pretreatment for UHMWPE with this adhesive primer at room temperature,common commercial adhesives,such as acrylic adhesive,could be used to bond UHMWPE.This was the first bonding system as above mentioned.Through this pretreatment the tensile shear bonding strength of UHMWPE bonded to UHMWPE(UHMWPE/UHMWPE)with acrylic adhesive was 3.59MPa,which was 2.6 times as much as that of UHMWPE/UHMWPE pretreated by sulfuric acid-potassium dichromate solution at 65℃～75℃.The mechanism of this adhesive primer treating UHMWPE at room temperature to enhance bonding strength was that the chemical process made UHMWPE surfaces to be corroded and etched and so that strengthened anchoring strength between the bonding layer and the UHMWPE.A long-term dipping in water or lubricating oil made a reduction of the tensile shear bonding strength of this bonding system less than 15%.The dissertation has also developed a kind of thickened 2-cyanoacrylate adhesive and its special self-contained primer for bonding UHMWPE.This was the second bonding system as above mentioned.A key to modify 2-cyanoacrylate was adding 1.5wt.%allyltrimethylolpropane in which.Heat resistance and water resistance of the modified 2-cyanoacrylate has been obviously improved.The optimal active principle in the primer was triphenylphosphine,which optimal concentration was 0.1 wt.%.An addition of 2wt.%N99 additive in the primer was effective for controlling increase of water in the primer during storage and made storage time of the primer to reach 6 months.It was important for improvement of wetting ability of the primer to choose 1,1,2-trichloro-1,2,2-trifluoroethane and acetone mixed solution(1:1)as solvent of the primer.Because surface energy of UHMWPE coated by the primer could be increased,2-cyanoacrylate adhesive could effectively wet the surface of UHMWPE and so that the bonding strength could be heightened obviously.Through this pretreatment the tensile shear bonding strength of UHMWPE bonded to UHMWPE with 2-cyanoacrylate adhesive could reach 7.80MPa.Lubricating oils had little influence on the bonding property of this bonding system,but water made it drop intensively.The dissertation has also developed a kind of bicomponent adhesive,which could self-etch interfaces of UHMWPE at that time of bonding UHMWPE.This special adhesive was named SEUMPE for short.This was the third bonding system as above mentioned.Component A of the SEUMPE was from acrylate structure adhesive,which formula has been optimized.A primary innovate of the formula was that a right amount of retarding agent from copper bromide was added in the component A.This could control the time for generation of free radical caused by evocating agent after the component A and B mixed,and thus delay possible operation time during bonding operation and not sacrifice bonding effect at the same time.The possible operation time of this bonding system reached 20 minutes,which was three and a half times as long as other domestic and foreign congeneric adhesives.Component B of the SEUMPE was evocating agent from triethylborane hexanediamine complex.A primary innovate of its formula was that optimal variety and dosage of polymerization inhibitor and antioxidant for the component B were obtained.With the optimal formula storage stability of the component B increased obviously and its chemical structure did not changed at the same time.The storage time of this evocating agent from triethylborane hexanediamine complex with special formula was 18 times as long as foreign congeneric evocating agent given in correlative patents.The SEUMPE was very suitable for bonding UHMWPE without any pretreatment for UHMWPE.Through bonding with the SEUMPE the tensile shear bonding strength of UHMWPE bonded to UHMWPE(UHMWPE/UHMWPE)was 8.70MPa,UHMWPE/45#steel 8.85MPa,UHMWPE/aluminum 8.68MPa,UHMWPE/ceramics 8.62MPa and UHMWPE/stainless steel 8.28MPa.After a long-term dipping in water or lubricating oil for 240 hours drop rate of the tensile shear bonding strength of all the above mentioned bonding pairs was less than 21%.When the SEUMPE was used for bonding other low surface energy plastics,excellent bonding effect could be also obtained.The obtained test data of tensile shear bonding strength were higher than that of domestic and foreign congeneric adhesives reported in literatures.Based on experimental and theoretical studies,the dissertation has explained the mechanism of the SEUMPE bonding UHMWPE to obtain excellent bonding effect as follows.When the component A and B of the SEUMPE mixed,a chemical process of initiation of polymerization of acrylate structure adhesive(component A)took place.The evocating agent was triethylborane hexanediamine complex(component B).During the chemical process,at the same of bonding UHMWPE a series of physical and chemical change took place on the bonded surface of UHMWPE.Those changes,which were of benefit to improving bonding effect,included etched surface,yielded carboxylic acid group,enhanced polarity and elevated surface energy.Moreover,the initiation reaction caused by triethylborane hexanediamine complex was a unique interfacial polymerization reaction,which polymerization shrinkage was in the direction of the interface.When the adhesive-banded joints of UHMWPE was exposed to external force,it tended toward rather cohesive damage than interface damage.This was the principal factor of the SEUMPE supplying excellent bonding ability to low surface energy materials.The dissertation designed a special test to investigate influence of tribological load formed by reciprocating friction on bonding properties of UHMWPE.Another special test to investigate influence of tribological load formed by ultrahigh pressure water jet erosive wear on bonding properties of UHMWPE was also designed.Two kinds of adhesive-banded joint of UHMWPE bonded to 45#steel with 2-cyanoacrylate adhesive and its special self-contained primer and the SEUMPE respectively were put into test.During whole reciprocating friction test the interfaces of adhesive-banded joints underwent 1.08×106 times reciprocating shearing cycle.But influences of tribological load formed by reciprocating friction under the condition of oil lubrication on tensile shear bonding strength of the above mentioned two kinds of adhesive-banded joint were limited.The drop rate of tensile bonding strength of them was less than 21%.This meant that those two kinds of bonding-type tribological composite material with UHMWPE could be used for reciprocating friction situation under the condition of oil lubrication.But reliability of the latter was higher.Every ultrahigh pressure water jet erosive wear test was carried out for 4 cycles(400 hours).In every cycle(100 hours)ultrahigh pressure water jet erosive wear test took up 1 hour and dipping specimens in water took up the rest 90 hours.But influences of tribological load formed by ultrahigh pressure water jet erosive wear on tensile shear bonding strength of the adhesive-banded joint of UHMWPE bonded to 45#steel with the SEUMPE were limited.After such whole cycle test the drop rate of tensile bonding strength of it was only 9%.This meant that this kind of bonding-type tribological composite material with UHMWPE could be used for ultrahigh pressure water jet erosive wear situation.On the contrary,influences of tribological load formed by ultrahigh pressure water jet erosive wear on tensile shear bonding strength of the adhesive-banded joint of UHMWPE bonded to 45#steel with 2-cyanoacrylate adhesive and its special self-contained primer were great.It could not be used for ultrahigh pressure water jet erosive wear situation.