Increase in the State of Cure in Vulcanizates After Removal From the Mold

Abstract

The progress of cure reactions was observed for rubber sheets during the cooling period after their extraction from the mold. The study was performed by considering either motionless air at 125°C and water at 12°C for cooling the rubber previously cured in a mold kept at 160eC. A significant increase in the state of cure was calculated with the help of a numerical model for the vulcanizates, especially in the case of air at 125°C. An improvement in physical properties such as the swellling in toluene, and mechanical properties measured either under static or dynamic conditions, was determined. Some parameters were found of interest, especially the kind of cooling fluid and its temperature, and the state of cure of the vulcanizate at the time of extraction out of the midplane of rubber sheets where the state of cure was lower, cooling in air at 125°C was responsible for a development of the profiles of state of cure through the sample leading to a more homogeneous material.

Simulation of the effect of variation in the cooling cycle on the state of cure in a rubber component

“…The heat conduction equation and the initial and boundary conditions are given in equations (1)- (5).…”

“…For some components, the cure accumulated during the cooling phase can be a significant fraction of the overall cure at some locations within the component. 5 The convection cooling and the resulting state of cure distribution of a onedimensional (1D) rectangular component that has been ejected from a mold after attaining a specified minimum state of cure has been successfully modeled and validated. 5 In that work, both air 5,6 and water 6 convection cooling of a sheet of rubber removed from a mold at a target minimum state of cure were investigated.…”

“…5 The convection cooling and the resulting state of cure distribution of a onedimensional (1D) rectangular component that has been ejected from a mold after attaining a specified minimum state of cure has been successfully modeled and validated. 5 In that work, both air 5,6 and water 6 convection cooling of a sheet of rubber removed from a mold at a target minimum state of cure were investigated. Further work 7 in this line of investigation considered the effect of ambient air temperature as well as component thickness on the resulting temperature and state of cure profiles.…”

“…The majority of the work pertains to understanding the sensitivity of the distribution of state of cure to potentially variable ambient conditions that typically occur during the convection cooling of a component after removal from a mold. This work is an extension of the prior research [4][5][6] in that in the present work the simulation is used to determine the cure time required so that the minimum cure in the component after cooling to ambient conditions is equal to the target cure for the compound. The model used herein is similar to that in the prior work, [4][5][6] with the exceptions that in this work the exothermic heat of reaction is not included and the cure is accumulated past the point of 100% cure to evaluate the excess thermal history that occurs in portions of the component.…”

Simulation of the Distribution of State of Cure for Multi-stage Curing Processes

“…The effect of initial elastomer temperature on the transient temperature profiles and the resulting cure times for a molded component have been investigated previously [1]. Research has been reported concerning the temperature and state of cure profiles that occur within a component during cooling after demolding [2] and also for simulation of the state of cure profile in a tire during molding using variable thermal conductivity and time varying boundary conditions [3]. More comprehensive general information on heat transfer in the processing of rubber is available [4].…”