CTBN-modified epoxy

Siebeif, A.R., Tolle, L.L. and Drake, R.S., CTBN-modified epoxies work in poor bonding conditions. Adhes. Age, 29, 19 (1986). 

These differences in modulus may be at least partially explained by DSC data such as that in Fig. 10. It is seen that in general the glass transition regions of the ATBN-and CTBN-modified epoxies are broader and have a lower midpoint than those of the control and two siloxane-modified materials. This thermal data suggests that the butadiene oligomers are relatively more miscible with the epoxy and may act as plasticizers. As an additional point, it is likely that the higher molecular weight of the... 

The second noteworthy morphological feature is presented in Fig. 12b. This micrograph depicts the pre-crack front of 15-1500-70F, which had a value significantly above that of the control, as shown in Fig. 11 a. The holes may be examples of the dilatation effect observed in CTBN-modified epoxies l9,22> in which rubber particles dilate in mutually perpendicular directions under the application of a triaxial stress and then collapse into spherical cavities following fracture. Dilatation requires a mismatch in coefficients of thermal expansion of resin and rubber 11. This effect will therefore be most striking when the elastomeric phase is homogeneous, as is apparently the case here. 

The number of cycles of disk rotation required to initiate the wear track correlated positively with the weight percent of the siloxane modifier in the epoxy. However, the initiation times for the ATBN- and CTBN-modified epoxies showed no significant correlation with the percentage of the incorporated modifier. The initiation of the wear track is assumed to result from the fatigue of the epoxy hence initiation time is related to the surface stresses. Because the surface stresses are inversely related to the elastic modulus as predicted by the Hertzian elastic contact theory 52), the initiation time data at ION load were compared to the elastic moduli of the materials in Fig. 16. The initiation times for the siloxane-modified epoxies were negatively correlated with their elastic moduli while samples modified with ATBN and CTBN showed positive correlations with their moduli. At lower loads the initiation times for the siloxane-modified epoxies increased. The effect of load on the CTBN- and ATBN-modified epoxies was too erratic to show any significant trends. 

In summary, we can first say that there is no significant evidence that the low surface energy siloxane-modified epoxies reduce friction compared with the unmodified epoxy or the ATBN- and CTBN-modified epoxies. Based on the results of the steel ball-on-epoxy experiments, the most significant effect of the siloxane modifiers is the reduction of the elastic modulus associated with large closely spaced domains. The longer initiation times and lowest wear rates observed for the siloxane-modified epoxies were generally associated with a lower modulus. Epoxy modified with the CTBN of 18% AN content also showed lower wear rates with lower modulus but, in contrast with the siloxane-modified resins, had shorter initiation times with lower modulus. 

TABLE 8.5 Properties of a CTBN Modified Epoxy Adhesive17... 

Formulation components Unmodified epoxy CTBN modified epoxy... 

TABLE 8.6 Formulas for Two-Part CTBN Modified Epoxy Adhesive System Cured Two Week at 25°C18... 

Technical Bulletin, Hycar CTBN Modified Epoxy Adhesives, B. F. Goodrich Company, AB-8, Cleveland, OH, 1990. (Hycar products now manufactured by Noveon, Inc.)... 

CTBN modified epoxy resin (EPON 58034, Resolution Performance 20... 

Table 12.14 shows a comparison of dicyandiamide cured epoxy adhesives formulated with and without a CTBN adduct. When compared to the control epoxy, the toughened formulation exhibits significantly higher peel strength and moderately higher tensile shear strength. CTBN modified epoxy adhesives are generally one-part systems, cured with dicyandiamide at elevated temperature. 

EPI-REZ 3519-W-50 560-660 5,000-15,000 Waterborne dispersion of a CTBN modified epoxy resin Resolution... 

Formulas for two-part CTBN modified epoxy adhesive system... 

Typical formulations and properties of epoxy-terminated and nonterminated polysulfide-epoxy adhesive Formulation for a two-part CTBN modified epoxy adhesive system Starting formulation for a fast-setting, toughened epoxy adhesive... 

Obviously, adhesive performance was closely associated with compatibility between the PPU/ETBN blend and epoxy matrix as well as between PPU and ETBN. As in CTBN-modified epoxy adhesives (Figure 6), the nitrile content of CTBN played an important role. When PPU containing a polypropylene oxide) segment with Mn 2000 g/mol was blended with ETBN, both lap shear strength and T-peel strength increased with increasing nitrile content. The best results were obtained with ETBN derived from CTBN containing 26 wt% acrylonitrile. 

Ariga (45) disclosed developments with CTBN-modified epoxy acrylates which when prepared with other lower molecular weight dicarboxylic acids and select carboxyl-terminated oligopolyesters serve as novel oligomers for photocurable coatings. These systems have low uncured viscosity. In the cured state they possess excellent scratch and crosshatch adhesion, good direct and reverse impacts (duPont impact tester) and pass bending diameters of 2 mm. 

CHEMICAL RESISTANCE OF CTBN MODIFIED EPOXY COATINGS ... 

Addition of CTBN-DER 732 causes the interfacial zone to become much larger and more flexible. The micrograph is shown in figure 7 in which (a) contains CTBN endcapped with epoxy and (b) contains a mixture of CTBN and DGEBA epoxy. When 20 weight percent DER 732 (precombined with CTBN) is mixed with the DGEBA epoxy, the modification increases the fiacture energy fiom 5000 Jm to 6200 Jm as compared with the CTBN modified epoxy. 

BF Goodrich Chemical Group-Preliminary Data Sheets, (a) Hycar CTBN-Modified Epoxy Adhesives," (b) "Hycar ATBN-Modified Epoxy Adhesives," 8/1982. 

Figure 3.40. Specific fracture energy vs. CTBN or EXPANCEL content. CTBN modified epoxy system is denoted by A, EXPANCEL modified system by , hybrid system with a 5% of CTBN for various EXPANCEL contents by A, hybrid system with a 10% of CTBN for various EXPANCEL contents by O, and hybrid system with a 15% of CTBN for various EXPANCEL contents by [9]...

Table 3.4. Mechanical properties of CTBN modified epoxy systems [9]...

Figure 3.41. SEM images for fracture surfaces of slow cracking for CTBN modified epoxy systems (a) 5%, (b) 10%, and (c) 15% [9]...

Figure 10 Mechanical properties of a CTBN-modified epoxy (E)GEB A/piperidine). Rubber modification has its drawbacks, both yield strength and modulus are reduced.

Creed, K. E., CTBN Modified Epoxy Resin, Neutron Devices for US Energy, R D Administration Contract E (29-2)-656, August 1975. 

The co-reactants and curing condition for preparation of the CTBN modified epoxies are summarized in Table I and follow methods reported by Kalfoglou and Williams Micro-tensile specimens (ASTM Method D1708-66) are cut from the cured epoxy films while they are heated to rubbery state response at T 120°C and pulled in tension in an Instron TTB-M using the special line clamping previously described for thermomechanical analysis (TMA) testing. 

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