Insufficient Cure

Cheesy appearance Often MDI systems Low green strength Insufficient cure Off ratio Poor mixing Incorrect temperatures... 

It is quite probable that the resin is insufficiently cured at the junction between latewood surfaces because the water has not been efficiently removed from the film. One observation which substantiates this is that when the specimens are heated, the sheer strength and wood failure values both increase, and the distinction between earlywood and latewood disappears. This definitely indicates that the problem is due to under cure. 

Each one of the previous issues can influence the performance of the processing technique and the resulting composite in a variety of ways. Insufficient cure may result in a low and a consequent creep under stress. Inadequate flow may result in high levels of porosity or large voids. Online sensor systems permit process control [19] and are a useful tool toward improved quality in composites manufacture. Dielectric techniques have achieved the greatest success as commercial in-process monitoring systems. Optical-fiber methods show promise for further development, most notably where distinct features in chemical spectra can be obtained. 

EFFECTS OF CONCENTRATION. Analyses of cured films have often indicated that most of the photolnltlator remains unreacted (19. 20). Surprisingly, the use of lower concentrations often result in insufficient cure. The concentration of a photoinitiator is not simply or directly related to curing efficiency. If the selection of initiator and lamp are held constant, the net effect of varying the concentration of the photo initiator will be to determine the distribution of the initiating radicals throughout the coating. 

Insufficient cure time or temperature, leaving unreacted resin or hardener or excessive cure conditions, resulting in embrittlement. 

The corrosion of polymer matrix composites is also affected by two other factors the nature of the laminate, and in the case of thermoset resins, the cure. Improper or insufficient cure will adversely affect the corrosion... 

Similar errors in drillrag setup can cause rough hole walls, loose fibers, or burrs. These defects are not serious in and of themselves, but can lead to rough plating or copper nodules, which introduce stress concentrations. Rough walls are typically associated with an incorrect feed rate or drill speed, or insufficiently cured material. Loose fibers may be caused by incorrect drilling parameters or improper cleaning. Burrs are usually associated with too fast a drill feed or a dull drill. 

Paste that has been insufficiently cured is easily broken. The uncured paste is pale in color and soft. If the plate has been insufficiently cured, it can be rewetted and reheated to force the paste to cure. Another way is to dip the partially cured paste into dilute sulfuric acid, which is called pickling. The pickling curing process is also used for curing of powder-filled tubular positive plates. 

These techniques involve the analysis of the changes in the chemical and physical properties of a molded specimen as a function of temperature. They are not generally used for production or quality control but are quite useful in resolving problems that could be the result of insufficient cure and that are not readily detected by the more common visual or chemical tests. There is a rule-of-thumb test procedure that is a fairly reliable cure test, and it is based upon a visual inspection of the molded article for obvious defects such as... 

The resin is insufficiently cured. Although there is sufficient curing agent (and accelerator) available, the reaction temperature is not sufficient to finish curing. By postcuring at elevated temperatures, such molding compounds can be completely cured. 

Feng, L., Carvalho, R., and Suh, B.I. (2009) Insufficient cure under the condition of high irradiance and short irradiation time. Dent. Mater., 25 (3), 283-289. 

Blistering, shown as large swollen areas on a moulding surface may usually be traced to an insufficient cure or a low tool temperature. Blistering with the effect of small swollen areas, descriptively resembling small pimples or a rash, may very well be attributed to a tool running at an elevated temperature. 

Poor gloss finish on one or more faces of the moulded part indicates uneven temperatures of the tool, an insufficient cure time, or by attempting to mould with low moulding pressures. 

Internal voids are not visible to the eye but can be seen upon cutting through the moulding. Causes are usually insufficient cure or gas being trapped without adequate means of escape. 

Soft mouldings which are prone to distortion and often have a dull finish can normally be associated with an insufficient cure or low tool temperatures. 

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