Diaphragm Design Manual - Simrit

Nervy – This refers to the excess stress imparted to the diaphragm by rubber that has beenscorched, begun to cure, or is too old to use even though it may still be moldable.Oil Resistance – Ability to withstand swelling by a specified oily liquid for specified time andtemperature, expressed as percentage swelling or volume increase of specimen. Oil Resistance –as applies to vulcanized elastomer compositions: resistance to change in size and shape andresistance to loss in physical (mechanical) properties due to contacts with or immersion in oil.Optimum Cure – The physical properties of a rubber compound vulcanized at a giventemperature for increasing periods of time undergo continuous change. For example, tensilestrength may rise to a maximum, continue on a plateau, and then decline, whereas breakingelongation may continuously decrease.Therefore, it is impossible to choose any one time of cure at whichever property will be at itsoptimum. Hence, optimum cure is a compromise and may be considered as that time required inobtaining the combination of properties that are most desirable for the article underconsideration.Over cure – A state of excessive vulcanization resulting from overstepping the optimum cure.Manifested by softness, brittleness, or impairment in the age resisting quality of the curedelastomer.Oxidation – Active oxygen degrades organic materials. This is called oxidation.Rate of degradation will increase with rising temperatures.Ozone – Is an allotropic form of oxygen, (03), produced by the action of electrical discharges inair. It is a gas with a characteristic odor, and is a powerful oxidizing agent. Rubber compoundsin a stretched condition are susceptible to the deteriorating action of ozone in the atmosphere,which results in a cracking.Permanent Set – Sometimes referred to, as compression set, it is the amount by which anelastic material fails to return to its original form after a deformation.Plasticizer – A substance that softens another substance through its solvent action.Polymer – A polymer is a very long chain of units of monomers prepared by means of anaddition and/or a condensation polymerization. The units may be the same or different. Thereare copolymers, dipolymers, tri- or terpolymers, quadripolymers, high polymers, etc.Post Curing – An extended curing cycle after molding usually done to enhance the physicalproperties of the rubber.Precure – Typically done to coated fabrics. This process leaves some molding properties in thematerial but allows the fabric to remain better centered in the rubber coating especially in“aggressive” convolution shapes.Processing Aids – Waxes, low molecular weight polyethylene, metal soaps, petroleum oils andother agents, which dissolve or lubricate rubbers, soften them and act as processing aids.Reinforcing Agent – In rubber compounding, a finely-divided substance or filler which whenproperly dispersed in rubber produces improved physical properties in the vulcanized product, i.e.greater energy of resilience, greater resistance to abrasion, higher modulus of elasticity andtensile strength.© Copyright FNGP 200953