Epoxy resin Long continuous

With exactly equal amounts of bisphenol A and epichlorohydrin, this polymerization would continue until the polymer chains were very long and the material would be a solid polymer. In making epoxy resins, however, excess epichlorohydrin is added to form short chains with epichlorohydrins on both ends. More epichlorohydrin gives shorter chains and a runny prepolymer. Less epichlorohydrin gives longer chains (containing up to 25 epichlorohydrin/bisphenol A units) and a more viscous prepolymer. 

Fig. 2.4 The signal measured in a HD-OKE experiment on a epoxy resin (phenyl glycidyl ether) [28]. We show the OKE data obtained with laser pulses of different durations. In the long scan (dotted line) we used laser pulses of 1 ps, in the short scan (continuous line) the pulses were of 50 fs. In the inset figure, we show the same data in a very short time window. The dashed line is the instrumental response, obtained performing the OKE experiment on a sample with only instantaneous response, typically a quartz plate...

Compression set resistance can be improved considerably in all types of polychloroprene by effecting a very tight cure. Thus, long cure times, high curing temperatures and high accelerator concentrations are beneficial. While acceleration with ethylene thiourea (1 phr) or diethyl thiourea (1 phr) for fast continuous vulcanisation will meet most requirements, for the most demanding specifications it may be necessary to use trimethyl thiourea (2 phr) and epoxy resin (1 phr) or tributyl thiourea (3-4 phr). 

Epoxy adhesives are generally limited to continuous applications below 300°F (149°C). However, there are epoxy formulations that can withstand short terms at 500°F (260°C) and long-term service at 300-350°F (149-177°C). A combination epoxy-phenolic resin has been developed that will provide an adhesive capability at 700°F (371°C) for short-term operation and continuous operation at 350°F (177°C). 

Epoxy adhesives are generally limited to applications below 121 °C. Some epoxy adhesives tolerated short-term service at 260°C and long-term service at 149-260°C. These systems were formulated especially for thermal environments by incorporation of stable epoxy co-reactants or high-temperature curing agents into the adhesive. One of the most successful epoxy co-reactants is an epoxy-phenolic alloy. The excellent thermal stability of the phenolic resins is coupled with the adhesion properties of epoxies to provide an adhesive capable of 371 C short-term operation and continuous use at 177°C. "... 

In order to take advantage of the new abrasive grit materials, new and improved bond systems had to be developed. Subsequently, adhesive systems have also come a long way, progressing from fish and animal hide glues to urea-formaldehyde resins, epoxies, phenolic, and radiation-curable systems. This evolution has placed a continuing demand on the adhesive systems used in the manufacturing of abrasive products. 

---