Preparation And Characterization Of Powder Epoxy Adhesives

In this study,a series of fast-curing powder epoxy adhesives were prepared by melt blending method with epoxy resin,curing agent and catalyst.Powder epoxy adhesives have many advantages,such as non-toxicity,ease of use,and high recycling rate.Recently,with the diminishing petroleum oil reserves and serious environment pollution issues becoming more prominent,as well as sustainable development is the the main trend at present,material scientists are increasingly interested in using bio-based renewable resources to make bio-based products and chemicals.Bio-based epoxy resin and epoxy hardener were used to replace the petroleum-based epoxy resin.Considering the above aspects,this thesis would focus on the two main problems of curing powdery epoxy adhesive at medium temperature and toughening of epoxy,aiming at developing the powder epoxy adhesive with medium temperature curing and high toughness.The main contents of this thesis are as follows:?1?with the introduction of 2-MI into the E-20/HMTA systems have a higher impact strength,tensile strength,glass transition temperature?T_g?and thermal stability in comparison with the E-20/HMTA systems.The best mechanical properties were obtained at 100/8/0.6 weight ratio of E-20/HMTA/2-MI systems.DSC experiments revealed that the exothermic peak of E-20/HMTA/2-MI system was about 55? lower than that of E-20/HMTA system.The activation energy of the cure reaction was determined by both Kissinger's and Ozawa's methods at any heating rates.The activation energy,pre-exponential factor and the order of curing reaction are calculated to be about 100.3KJ/mol,3.57×10¹¹s^-11 and 0.94 respectively.Optimal curing parameters were predicted by evaluating a relationship between curing temperature and curing time.In order to achieve medium temperature curing,optimal curing parameter was recommended to be from 130? for 10 min.?2?The effect of 2-methylimidazole content on mechanical properties and curing properties of E-12/DDS/2-MI systems were studied.The result showed that impact strength and tensile strength of-12/DDS/2-MI systems increases and then decreases after adding 2-MI.when the content of 2-MI is0.2 wt%,the best mechanical properties were obtained,The impact strength and tensile strength of E-12/DDS/2-MI systems are 11.2 MPa,43.54Mpa respectively,which were 28.7%increase in impact strength with respect to E-12/DDS systems.With the incorporation of 2-MI could decrease the activation energy,which contribute to reduce the curing temperature and shorten the curing time.The activation energy,pre-exponential factor and the order of curing reaction are calculated to be about 64.27KJ/mol,6.3×10⁸ s^-11 and 0.91 respectively.?3?CATA as a bio-based hyperbranched toughener is prepared and subsequently introduced into the E-12/MPA/2-MI system,non-phase-separated hybrids with significant toughening effect are obtained.With such a mechanism,CATA is added into the E-12/MPA/2-MI system can simultaneously enhance toughness,glass transition temperature?T_g?,and tensile properties under a lower loading amount.CATA contains a large amount of terminal carboxyl groups,which can provide a better interfaceinteractionbetweentheepoxyresinsandCATA.Theimpactstrengthof E-12/MPA/2-MI/CATA systems with only 1.0wt%CATA loading up to the maximum of 16.7 KJ/m²,which is twice of those of E-12/MPA/2-MI system?7.9 KJ/m²?.In addition,thermal properties,fracture surfaces and curing behaviors are also studied.?4?The gallic acid-based epoxy resin was toughened by the carboxylic acid-functionalized tannic acid?CATA?as toughener,2,4-EMI as accelerator and MeHHPA as curing agent.The effect of CATA amount on the properties of epoxy materials was investigated using FTIR,¹³C-NMR,SEM,TGA and mechanical tests.The results showed that compared with neat system,the best overall performance occur in the GA-EP/MEHHPA/2,4-EMI/CATA systems containing 1.0wt%CATA,which are 74.8%increase in impact strength,23.2%increase in tensile strength,and 43.1%increase in fracture elongation.SEM reveal that CATA is incorporated into the E-12/MPA/2-MI system have no traces of phase separation and improve the toughness as evident from fibril formation.