Methylene curing agent

Cyanamide and its aromatic derivative, such as 4,4 -methylene bis(phenyl cyanamide), were reported to cure an epoxy resin at elevated temperatures.(4) It is also well known that the dimer of cyanamide (dicyandiamide) is the most important epoxy curing agent in one-package epoxy compounding.(5) Unfortunately, this dimer precipitates from the dispersion causing uneven mixing upon standing. 

Sample Preparation. The sample series was prepared by varying the ratio of Epon 828 to the methylene dlaniline (MDA) curing agent. The compositions tested contained 0%, 23.1%, 50.0% and 100% excess MDA over the stoichiometric amount. The MDA and diepoxide were heated to 100°C and mixed. The mixture was cast onto one side of a sheet of aluminum 5.5 cm. x 24.5 cm. x 5 mils, which had first been wiped with acetone to degrease the bonding surface. The final coating thickness was controlled at approximately 60 mils. 

The DGEBA based epoxies were reacted with various curing agents. These spectra were than compared to the solution spectra of unreacted epoxy. It was shown that the peaks due to the epoxide carbons were not present in the polymerized DGEBA. In their previous study, Sojka and Moniz 481 showed that DGEBA partially cured with piperidine, exhibited a peak near the methylene peak that increased in intensity and complexity with the curing reaction. This peak was assigned to the carboxyl-methine ether carbon and the methylene carbon near the reaction site. These studies addressed the questions ... 

MDI MEK MOCA (MBOCA) Therefore, a two-part mold would have two master patterns. An abbreviation for diphenylmethane-4,4 -diisocyanate. Methyl Ethyl Ketone Trade name for methylene bischloroaniline, which is a widely used curing agent for hot cure polyurethane elastomers. There are... 

Fig. 17. Effect of the number of methylene groups (n) in the curing agent on the dynamic modulus at 20 °C.

Liquid crystalline thermoset system 1. Liquid crystalline thermoset prepolymer dihydroxy methylstilbene epoxy (Mn, 3600) 2. Curing agent 4,4 -methylene dianiline ... 

The materials used were Epon 828 epoxy resin and methylene dianiline (Tonox), both from the Shell Chemical Co. The resin and curing agent were melted together, mixed, degassed, and cast between glass plates. The cure cycle was as follows 45 min at 60 C, 30 min at 80 C, and 2.5 hr at 150 C then slow cooling to room temperature. The amine to epoxy ratio (A/E) was varied from 0.7 to 2.0 (in terms of equivalents). Compositions are given in Table I. 

Seven polyurethane adhesives have been developed at Lawrence Livermore National Laboratory (LLNL). These adhesives, designated Halthanes were synthesized because of OSHA restrictions on the use of the curing agent methylene bis(2-chloroani1ine). Four of the Halthanes were made fromLLNL-developed 4,4 -methylene bis(phenylisocyanate) terminated prepolymers cured with a blend of polyols three were made from an LLNL-developed prepolymer terminated with Hylene W and cured with aromatic diamines. In this paper we report the dynamic mechanical and thermal behavior of these seven segmented polyurethanes. 

A significant effort has been carried out in recent years on chain extenders for urethane elastomers. This has been prompted primarily by the search for a suitable replacement for 4,4 -methylene bis(o-chloroaniline) (MOCA), a widely used chain extender and curing agent which gives a positive Ames test (screening test for mutagenicity). 

Resin II contains tetraglycidyl methylene dianiline (TGMDA) as the principal epoxide with small amounts of a cresol novolac and DGEBA. DICY as curing agent is present in an amount such that the amine epoxy ratio is 0.25. Diuron is the accelerator. The supplier s recommended standard cure is the same as for SP250. However, in this system approximately 20 percent of the epoxide remains unreacted following the cure cycle (1 ). Selected resin plates were subjected to additional cure at 170°C and 220°C. The samples post cured at 220 C for forty minutes showed no residual epoxide absorbance in the IR spectrum. 

Dytek A. PuPont] 2-Methylpenta-methylene diamine epoxy curing agent also used in polyurethanes, wet strength resins, scale and corrosion inhibitors, gasoline additives, polyamide plastics, fflms, adhesives, and ii. ... 

Novolaks are soluble resins that melt without chemical change (no heat curing). They are polynuclear phenols with methylene cross-link bridges and molecular weights of 600-1500. Although they can be converted into insoluble resins by means of curing agents such as formaldehyde, heat alone is not effective. 

Novolaks cannot undergo a spontaneous curing, because they are polyfunctional phenols cross-linked by methylene bridges. Therefore the curing agents must be at least bifunctional compounds. Curing can be carried out without the elimination of water with compounds that are easily converted into methylene carbonium ions for example, hexamethylene tetramine, which is widely used commercially (Urotropin, Hexa). Dihydroxy-benzyl amine and trihydroxybezyl amine structures are also formed with the elimination of ammonia, e.g.. 

Hexamethylenetetramine (Hexamine) - te-tr9- inen [ISV hexa- + methylene + tetra-+ amine] (1888) (HMT, methenamine, and urotropine) n. (CH2)6-N4. A bicyclic compound, the reaction product of ammonia and formaldehyde. It is used as a basic catalyst and accelerator for phenolic and urea resins, and a solid, catalytic-type curing agent (hardener) for epoxies See image). 

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