Epoxy resin is one kind contains annulus the reactivity of oxygen radical group gets together beforehand content and polymer. This kind of material has a variety of industry use. Nowadays, there are various annulus oxygen adhesives on the market, can satisfy different requirement. Because system of epoxy resin adhesive basically is used at structural purpose, one of property that need a consideration are vitrification transition temperature (Tg) . Tg is the temperature that change produces between the vitreous condition of amorphous solid and oak colloidal state. Above is worth in this, polymer is behaved so that resemble balata material, and it is under this value, polymer catenary has relatively inferior mobility, and material becomes hard mix hard. Accordingly, tg is considered as to weigh a of dependability of adhesive of this kind of structure very useful measure. The element of Tg has adhesive of influence annulus oxygen a few: Degree of the type of agent of the chemical structure of epoxy resin, solidify, solidify and solidify condition (time and temperature (Tcure) . Had undertaken a lot of research will assess the impact between Tcure and Tg. The time that a few research focus in system of hot solid sex - temperature - change (TTT) on the graph, especially those systems that take aggregate mechanism solidify through the pace. On the other hand, in balmy amine - in epoxy resin system, solidify temperature and vitrification transition temperature can pass equation (1) undertake correlation. Their research concludes, the Tg that arises from this cannot compare 15-30°C of Tcure tower above.
The experience law of a long-term establish, namely Tg cannot exceed Tcure to exceed 25°C. This is why business limits the matter in 40–50°C from beginning to end with the Tg of adhesive of cold curing epoxy resin. On the other hand, the temperature of adhesive of epoxy resin of high temperature solidify is highest can amount to 160°C. Tg is taller, the performance of these structural adhesive systems is better; However, tall solidify temperature cannot apply at each substrate. Accordingly, scientific challenge depends on making up a kind to be able to acquire the adhesive system of tall Tg when the solidify below room temperature.
About this one problem, the annulus oxygen that the person such as Fernandez-Francos studied a kind to be based on catalysis of amine of father's younger brother newly / the double solidify system of sulfur mellow recipe. In existence excessive annulus the circumstance of oxygen radical group falls, sulfur is mellow - epoxy resin produces condensation in the first phase of solidify, and once sulfur is mellow base the group is extinct, excessive epoxy resin all gets together in the 2nd phase, increased the Tg of the recipe thereby. However, all these research are pass high temperature solidify or hind solidify craft undertakes. Accordingly, show without evidence whether this kind of aggregate process also allots in room temperature unripe. The possibility that leaves the Tg that raises recipe of adhesive of cold curing epoxy resin to study a kind of situation that using exterior heat source method, offerred a kind of new prescription. The compound solidify of the commercial adhesive that this kind of new recipe is based on Dr.Sails® to develop by a kind is not composition of adhesive of oxygen of chemical and metric annulus.
Study content:
1, study a system
2, the analyse of DSC motivation credit of solidify process
If the graph is shown 2 times, the first radiative peak that in 80°C the left and right sides appears (A) correspondence is mixed at epoxy resin the cross-linking reaction between agent of sulfur mellow cross-linking. In 120°C the left and right sides observes exothermic transforms the 2nd times (B) , because amine of father's younger brother exists in solidify system,the likelihood is. However, compare with the photograph of quantity of heat that releases in the first peak value, the quantity of heat that this reaction releases appears negligible not plan; Accordingly, it can be considered as reaction 2 times. The cross-linking that the epoxy resin place that makes up with amine cross-linking agent describes reacts (graph 2 medium curves (C) ) in 120°C the left and right sides appears remarkable radiative the greatest peak value.
The active when cross-linking agent base the rate between oxygen radical group is group and annulus chemical and metric than (D01) when, detect the reaction peak that departs to two. The reaction of the first kind of correspondence between annulus oxygen and agent of sulfur mellow cross-linking, the 2nd kind of correspondence at the reaction with amine cross-linking agent. As the epoxy resin in the recipe proportional increase, in 130°C the left and right sides detects the occurrence of the 3rd peak, with jackknife of amine solidify peak. This kind of phenomenon makes clear the 3rd reaction produced in solidify process, and this kind of reaction can be of the DGEBA as a result of excessive only all get together action (show like Scheme 1 place) . The other compound of reaction can be not caused in the recipe.
The 170 J·g−1 of prep above of total quantity of heat that D01, D02 and D03 recipe release in whole solidify process, but D04 recipe did not achieve 100 J·g–1 even (watch 2) . The proportion of DGBEA/ cross-linking agent is higher, the quantity of heat that releases in reaction process is lower; Accordingly, did not reach the enough temperature that uses Yu Junju. When DGEBA excessive, the system can diffuse the quantity of heat of generation, although still have link of quite a few,oxygen radical group needs response, but reachs temperature is insufficient. However, d03 recipe shows perfect balance it seems that, react with releasing enough quantity of heat to arise to all get together.
Agent of DGEBA epoxy resin, cross-linking and chemistry are metric the anticipation that after with blame chemistry metric recipe reacts, forms if the network pursues show 4 times. Below this kind of circumstance, reactivity stays after cold curing phase base round; Of adhesive hind the mechanical performance that solidify will enhance material. Otherwise, the preparation of solidify will keep insusceptible, maintain similar mechanical performance and identical Tg.
3, of solidify process stream change credit analyse
If the graph is shown 5 times, content of the DGBEA in preparation is higher, gel time is longer. Metric to chemistry recipe (D01) , gel time comes true very easily, react namely happen very quickly, material reachs good consistency (G'>G“ ) . As the addition of the quantity of DGBEA, detect the defer that realizes gel time. Reaction happens slower; However, important is to should point out, recipe D01, D02 and the G’ value that D03 obtains are almost same. In these systems, stream change the curve shows two phase reaction: The first phase, as a result of the tall reactivity of solidify system composition, g’ increases quickly; With pass an imperial examination 2 phase, among them the addition of G’ becomes slower, this but because ascribe is in what the quantity of heat that releases during the first phase brings about excessive epoxy resin to all get together. Can observe, because cross-linking process is medium,the quantity of heat that release can't activation to all get together, d04 presents a remarkable low G’ to be worth. Because the scale of cross-linking agent is apparent inferior, the cross-linking density that obtains accordingly is very low, g’ value is very accordingly little also.
4, DMA is thermomechanical token
As the addition of content of the epoxy resin in the recipe, the Tg of end item moves to higher temperature, and need not raise solidify temperature (graph 6) . The value of D01 is 40°C, and the value of D02 and D03 is 58°C and 70°C respectively. Accordingly, through increasing the proportion of the epoxy resin in the recipe one times, tg can increase 30°C. The solidify reaction that must study considering place allots in room temperature unripe.
Recipe of develops to obtain tall Tg most epoxy resin must pass course of high temperature solidify. Below current condition, do not need such measure, because heat further,won't cause further reaction. Those who prove this is, d03 sample issues solidify 2 hours in 80°C, be in next the solidify after 120°C falls 1 hour, acquisition Tg value did not change almost (72°C, graph 7) . Can observe from acquisition DMA result (graph 7) , the change of Tg is negligible almost. Mountain peak moves right a little; However, observed change is indemonstrable measure of the solidify after the adhesive that is this kind of type is added is reasonable. Be in when adhesive below room temperature when solidify, reaction is complete, and do not need add aftertreatment measure, this assumed the additional cost of this kind of product.
5, physical characteristic
Graph the 8 representative data that showed tensile test. In the apparent difference that can observe stress is worth between sample. Although D01 adhesive recipe has 5MPa rupture tensile strength, but D03 adhesive recipe obtains higher cost, achieve 14MPa. In the watch 3 in can observe more detailed value. Accordingly, d03 recipe is in stress or be out of shape next capacity that have higher counteractive load, as a result of,this is of excessive epoxy resin all get together reaction produced harder polymer network. However, the percentage elongation of D01 and D03 preparation keeps changeless. Ascribe of this kind of phenomenon a such facts, changing to what be not chemical and metric recipe from chemical and metric recipe namely is the quantity of epoxy resin, is not the quantity of cross-linking agent or type. What the solidify system of this adhesive recipe aims to obtain tenacity to increase is flexible annulus oxygen adhesive. Notable is, metric to be not chemistry recipe, tenacity increased 56% , confirmed the structure that makes assumes thereby.
D01 and D03 adhesive recipe show adhesive lose effectiveness. If the graph is shown 9 times, build when what D01 adhesive achieves 2MPa when receiving shear strength, d03 was not the value of chemical and metric recipe to break up one time. Hydroxyl (OH) to annulus the chemical agglutinate function in oxygen radical is in charge of, the wear that the adhesive that and hydroxyl chroma affects annulus oxygen forms between adhesive and metallic surface combines. Accordingly, more hydroxyl show better agglutinate performance. This comes true through be not chemical and metric recipe just about. Epoxy resin content is higher, the hydroxyl chroma in final polymer structure is more, because they won't intervene as reagent,all get together reaction.
Study conclusion:
1, the compound solidify system that studied a kind of cold curing, the chemistry that this system is based on catalysis of amine of father's younger brother is metric with blame chemistry metric sulfur is mellow / amine epoxy resin recipe.
2, the annulus in existence excessive oxygen radical is round (be not chemical and metric system) below the circumstance, sulfur is mellow - epoxy resin and amine - condensation of epoxy resin happening, and the epoxy resin of excessive all gets together in the 2nd phase. The solidify rate that sends unripe the 2nd response below room temperature is far under sulfur alcohol / amine - the solidify speed that annulus oxygen condensation reacts. This differentia different should react through two kinds the different reaction mechanism of an experience will explain, because on one hand, annulus oxygen amine and the cent condition that alcohol of annulus oxygen sulfur experienced a kind to undertake quickly at the beginning grow aggregate mechanism. On the other hand, the epoxy resin of excessive passes the chain group mechanism of catalysis of amine of father's younger brother, ability of content of tall initator of need of amine of father's younger brother is fast activation. The difference of response rate makes clear between two kinds of craft, in all get together before reaction ends, can part two solidify phase with custom-built and final data.
3, optimize the scale between epoxy resin and cross-linking agent, will in order to produce enough exothermic activation to all get together (D03 recipe) , this increased the Tg of child, and do not need any aftertreatments. This recipe produced Tg to be the recipe of epoxy resin adhesive of 70°C, can last what utmost land increased data working temperature, broke the established experience law of Tg≈Tcure+25°C.
4, the product of development is more close together, harder, but maintained chemical and metric recipe (D01) flexibility, this is to enhance pair of concussion force, thermal shock and the strength that heat up a loop.
Document information:
Oiane Ruíz De Azúa1, núria Agulló1, jordi Arbusà2 And Salvador Borrós, improving Glass Transition Temperature And Toughness Of Epoxy Adhesives By A Complex Room-Temperature Curing System By Changing The Stoichiometry, polymers 2023, 15(2) , 252
Doi: 10.3390/polym15020252