Correspondence:
[*]
Corresponding author: Gabriele Milani, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy. E-mail:gabriele.milani@polimi.it
Abstract: The paper aims at studying the possible interaction between two different
accelerators (DPG and TBBS) in the chemical kinetic of Natural Rubber (NR)
vulcanized with sulphur. Two different numerical meta-models, which belong
to the family of the so-called response surfaces RS are compared. The first
is linear against TBBS and DPG and therefore well reproduces no interaction
between the accelerators, whereas the latter is quadratic with bilinear
term. The numerical meta-models are calibrated on the experimental data
obtained by using the same mixture with several DPG and TBBS concentrations,
varying the curing temperature in the range 150-180°C and obtaining
rheometer curves with a step of 10°C. In order to study any possible
interaction between the two accelerators - and eventually evaluating its
engineering relevance - rheometer data are normalized by means of the
well-known Sun and Isayev normalization approach and two output parameters
are assumed as meaningful to have an insight into the possible interaction,
namely time at maximum torque and reversion percentage. Both RSs are deduced
from standard best fitting of experimental data available. It is found that,
generally, there is a sort of interaction between TBBS and DPG, but that the
error introduced making use of a linear model (no interaction) is generally
lower than 10%, i.e. fully acceptable from an engineering standpoint.
Keywords: Natural Rubber NR vulcanization, accelerated sulphur, experimental rheometer curves, numerical meta model, interaction evaluation
