Studies on the formulation and mechanical and dynamic properties of natural rubber/chloroprene rubber blend for rubber bushing application
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Date
2006
Authors
Sethu, Puspalatha
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Abstract
A systematic investigation, based on natural rubber and chloroprene rubber
(NR/CR) blend formulations, were carried out to develop a suitable formulation for
rubber bushing. Both static properties and dynamic properties were considered. The
important properties considered for rubber bushing application were good compression
set, good ageing resistance and good vibration isolation with low transmissibility. The
starting and reference compound used is a typical 100% NR formulation used for
vibration mounting.
Based on Formulation 1, the investigation of gum vulcanizates of 100% NR,
100% CR and NR/CR blends of 65/35, 70/30, 75/25, 80/20 and 85/15 by ratio were
carried out. The cure rate of 100%CR is slower than 100% NR and displays low
hardness, tensile strength and high compression set. Better cure characteristic was
observed for the NR/CR blends and higher amount of NR gaves better resilience,
tensile strength, M300 and compression set.
Filled vulcanizates of 100% NR, 100% CR and NR/CR blends were
investigated based on Formulation 2 i.e. by adding 40 phr of carbon black filler and 5
phr of processing oil into Formulation 1. Addition of filler reduces the vulcanization
time and higher amount of NR increases the tensile strength and modulus 300 while the
compression set and ageing resistance are better with higher amount of CR. Based on
the overall properties of tensile strength, resilience, compression set and ageing
resistance, the blend of NR/CR at 75/25 ratio was chosen for a subsequent study by
varying the carbon black loading at 0, 10, 20, 30, 40, 50, 60, 70 and 80 phr. Increased
in amount of carbon black increases the efficiency of vulcanization and hardness, and
decreases the resilience and elongation at break. Tensile strength value passes through a
definite maximum with the increased in carbon black loading and the optimum was
achieved at 40 phr of carbon black.
Formulation 3 was developed from Formulation 2, with the presence of special
accelerator Rhenogran ETU-80. The amount of carbon black was increased in
Formulation 3 compared to Formulation 2 accordingly and the required hardness of 50,
60, 70 and 80 Shore A were achieved by adding processing oil. Better tensile strength,
elongation at break, hysteresis, compression set and ageing resistance were obtained
with Formulation 3 compared to Formulation 2 due to presence of ETU which gives
more permanent linkages during vulcanization.
Rubber bushings were made based on Formulation 2 and Formulation 3 at
hardness of 70 Shore A, and the static and dynamic properties were determined. Axial
and radial compression tests showed that bushing based on Formulation 3 requires
more force at high deflection, and give better rubber to metal bonding than Formulation
2. Dynamic test was carried out at radial direction for about 10 000 cycles. The results
shows that bushing based on Formulation 3 gives higher isolation degree and lower
transmissibility (lower transmission of vibration) compared to Formulation 2.
It can be concluded that a suitable formulation was successfully developed for
bush mounting that gives an overall good balance in terms of mechanical properties,
compression set, and ageing resistance with good isolation and transmissibility
characteristics.
Description
PhD
Keywords
Industrial technology , Natural rubber , Rubber bushing