IBN AL- HAITHAM J. FO R PURE & APPL. SC I VO L. 23 (1) 2010
Inner Tube o f AL-Diwanyia Tyre Based on Natural
Rubber Blends
M. .A. Motar
Departme nt of Chemistry, College of Education, Al-Qadisiya
Unive rsity
Abstract
M ost tubes are made from buty l rubbers, but certain ty p es, such as giant tubes,
are based on natural rubber because very high green st rength is required when handling
the uncured comp ound. By using blends of natural rubber (NR) and brominated buty l
rubber (BIIR), it is p ossible to maintain high green st rength in the uncured comp ound
and improve impermeability and heat resist ance of the cured tube.
The best formulations are obtained in the p resence of 50 p hr of (BIIR) to
achieve desired mechanical p rop erties. Improved imp ermeability was obt ained by using
50 and 75 p hr of (BIIR) rubber in comp ounds. Blending of brominated buty l rubber
(BIIR) with natural rubber (NR) enhances air retention with accep table sacrifices in
green st rength.
When using blends of natural rubber and brominated buty l rubber it is necessary
to reduce the sulfur as the brominated buty l rubber (BIIR) content is increased.
Introduction
The use of halogens to modify p olymers has fascinated research workers from
the earliest days of the rubber industry . The utility of halogenation was first realized
when chlorinated natural rubber was developed, followed by the introduction of
neoprene by Du Pont[1].
A wide range of p olymers, involving either halogenation of the monomer p rior
to p olymerization or of the p olymer after p olymerization, was developed and introduced
to the rubber and p last ics industry . Included are fluoroelast omers, chlorinated
p olyethy lene, chlorosulp honated, chlorinated buty l and, more recently , brominated
buty l rubber[2].
Desp ite its early limitations, brominated buty l rubber offered some p otential
advantages over chlorinated buty l rubber in cure rate and adhesion. Poly sar limited
concentrated research and development effort towards develop ing a continuous solution
p rocess by which a highly st able and uniform brominated buty l rubber could be
manufactured on a large scale. The result was the construction and bringing on st ream
of the first commercial brominated buty l rubber p lant[3].
In this p aper we have studied the sy nthesis giant tubes by using blends of natural
rubber (NR) and brominated buty l rubber (BIIR). High green st rength in the uncured
comp ound , imp ermeability and heat resistance of the cured tube were imp roved by
using brominated buty l rubber.
IBN AL- HAITHAM J. FO R PURE & APPL. SC I VO L. 23 (1) 2010
Experime ntal
Materials
The p olymers used as a matrix in this st udy are NR (SM R 20), and p olysar
bromobuty X2.T he tetramethy lthiuram disulfide was used as accelerator and sulfur
donor.
Preparation of the Rubber Compounds
Four rubber comp ounds with different loading amounts of bromobuty l rubber
were prepared. For rubber comp ounding, we used a laboratory mill, rolls dimensions are
outside diameter 150mm, working distance 300mm, sp eed of the slow roll 24 rp m and
gear ratio 1.4. Compound recipes are summarized in Table (1). Aft er mixing, the
comp ounds were carefully remilled into flat sheets on a two-roll mill.Rheocurves were
recorded by using a M onsanto Rheometer ODR 2000 at 160
°
C. The t90 time, which
denotes t he time for 90% cure.
Permeability was recorded by using Const ant Volume M ethod. The constant
volume for the measurement of p ermeability is covered by ISO 1399. The app aratus
consists of a metal cell having two cavities sep arated by the test p iece. The high-
p ressure cavity is filled with the test gas at the required p ressure, which must be
measured to an accuracy of 1%. The low-p ressure side is connected to a p ressure
measuring device, usually cap illary U tube manometer with an adjust able height
reservoir. The test cell must be maintained to within±0.5°C of the required temp erature
because the p ermeability of gasses extremely sensitive to temp erature.
The test p iece is a disk between 50 min and 65 mm diameter and 0.25 mm to 3
mm thick, with a free testing surface of 8 to 16 cm
2
. Aft er the cell and test p iece were
assembled the high p ressure side is filled with gas at the test p ressure. The increase in
p ressure on the low p ressure side is t hen measured as a function of time, the manometer
being adjust ed to ensure that the measurements are taken at constant volume. Steady
st ate conditions are indicated by a linear relationship between p ressure changed and
time and may take at least an hour to be established.
Shore A hardness was measured at room temp erature by using a Zwick
duromatic.
Tensile prop erties were determined by a tensile tester (tensometer 10) according
to ASTM D-412 .
Results and Discussion
Cure propertie s
The levels of the three ingredients (sulfur, zinc oxide, dibenzothiozoledisup hide
[M BTS]) used to p lay a significant role in optimizing heat resistance and set (or growt h)
of tubes op erating at service temperature. Zinc oxide p lus minor amounts of accelerator
is the p roffered curing sy st em. With zinc oxide, the choice of M BTS determines the
balance of heat resistance, scorch, and cure times. By adjust ing accelerator (M BTS), it
p ossible to keep cure time constant and vary the scorch time to suit given factory
p rocess conditions[4]. See Table (2)
Tetramethy lthiuram disulfide was used very successfully as the accelerator and
sulfur donor to p rovide good balance of scorch safety and better heat resist ance.
When using blends of natural rubber level as t he brominated buty l it is necessary
to reduce the sulfur level as the brominated content is increased. Because it exhibits
reversion and has only fair heat aging behavior[5].
Physi cal Properties of Inner Tube Compound Containing Bromobutyl Rubber
IBN AL- HAITHAM J. FO R PURE & APPL. SC I VO L. 23 (1) 2010
Bromobuty l rubber can be blended with natural rubber in all p rop ortions to obtain
desired comp ound p rop erties[6]. Phy sical prop erties data of inner tube comp ounds are
shown in Table (3). Insp ection of the data shows large variations in many of the
p rop erties. In p articular, tensile st rength (18.8-12.0 M Pa), elongation at break (510-
600%) and tear st rength (51-37 KN/m) values vary widely . Tensile st rength values are
lowest for those comp ounds having high bromobuty l content; this is associated with the
tendency of natural rubber to form cry st allites when it is strained. See comp ounds 3 and
4. However, elongation at break values are highest for those comp ounds having high
contents of bromobuty l, see comp ounds 3and 4. Tear st rength values are highest for
those comp ounds having high content of NR see comp ounds 1 and 2. Bromobuty l
rubber in blends with NR in inner tube comp ounds shows imp rovement in the air
retention for compounds having high content of bromobuty l.
Impermeabil ity
A fundamental requirement of a tire inner liner is to minimize intra-carcass
p ressure build up , thus minimizing the danger of belt or p ly sep arations[7].
To minimize intra-carcass p ressure, the liner should be comp ounded to have very low
p ermeability , mainly by the choice of p olymer, with black and oil levels in the
comp ound having a lesser effect. For op timum Imp ermeability , the bromobuty l content
should be as high as p ossible; carbon black level should be high, but at a level that will
ensure reasonably low modulus and good flex p rop erties. While oil, which increases
p ermeability , should be kept as low as p ossible[8]. The effect of brominated buty l
content on p ermeability is shown in Table (3).
Conclusions
Bromobuty l rubber can be used to imp rove the gas imp ermeability , energy
absorp tion, resist ance to heat, weather, and various chemicals. At the same time, natural
rubber provides the p rop erties in a brmobuty l comp ound mainly , higher green st rength
and tack; higher tensile prop erties; higher cured adhesion to NR comp ounds when using
blends of natural rubber and brominated buty l rubber it is necessary to reduce the sulfur
as the brominated buty l rubber (BIIR) content is increased.
Re frences
1. Ohm, R.F. Edit. (1990)"Vanderbilt Rubber Hand book", R.T. Vanderbilt Co.,
Inc., Norwalk.
2. Parent, J.S. ; Thom,D.J.; Whitney ,G. and Hop kins,W. (2001). J. Poly m. Sci., Part
A: Poly m. Chem. 39:2019.
3. Waddell, W.H.; Kuhr, J.H. and Poulter, R.R (2001) in ACS Rubber Division
M eeting, Cleveland, October.
4. Kuntz, I. ; Zapp ,R.L. and Panchrov, R.J. (1984).The Chemist ry of the Zinc
Oxide Cur e of Halobuty l. Rubber Chemistry and Technol. 57(4): 813-825.
5. Waddell ,W.H and Rodgers,M .B. (2004). Rubber Comp ounding. In Kirk-
Ot hmer Ency clop edia of Chemical Technology , 5
th
Edition.
6. Waddell ,W.H. and Rodgers,M .B (2004) .Tyre App lication of Elast omers 2.
Casing Presented at a M eeting of the American Chemical Society , Rubber
Division, Grand Rap ids, M I.
7. Fusco, J.V. and Hous, P. (1987). Butyl and Halobuty l Rubbers. In Rubber
Technology , 3
rd
Edition Editor, M .M orton. Van Nost rand Reinhold.
8. Waddell, W.H. and Rodgers, M .B. (2005).The Science of Rubber Comp ounding.
In Science and Technolo gy of Rubber, 3
th
Edition. John Wiley and Son, NY.
IBN AL- HAITHAM J. FO R PURE & APPL. SC I VO L. 23 (1) 2010
Table(1):Recipes of inne r tube compounds with various bromobutyl loading
Ingredients 1 2 3
4
Phr p hr
p hr p hr
NR 100 75 50 25
Poly sar Bromobuty l X2 - 25 50 75
Zinc oxide 4 4 4 4
Stearic acid 2 2 2 2
Sulfur - 1.1 0.55 0.55
M BTS 4 4 4 4
TMTD 1.5 0.5 0.2 0.2
Treated whiting 12.5 12.5 12.5 12.5
Paraffinic oil 10 17.5 17.5 17.5
SRF N774 40 60 60 60
Table(2): Inner tube compounds cure propertie s
Compound 1 2 3 4
TS2
a
, min. 6.5 6.3 7.5 7.8
T90
b
, min. 4 6 8 8
a Time requir ed for 2% cure .
b Time required for 90% cure.
Table(3):Effect of inner tube compounds with various bromobutl loading on
physical propertie s
Compound 1 2 3 4
Hardness, Shore 53 53 52
49
Elon gation, % 510 510 550
600
Tensile strength, Mp a 18.8 15.5 13.4
12.0
300 % modulus, Mp a 1390 1100 890
770
Tear st rength (KN/m) 51 40 40
37
Permeability to air ( m
2
/s.p a ) 9×10
-17
11×10
-17
13×10
-17
14×10
-17
2010) 1( 23مجلة ابن الھیثم للعلوم الصرفة والتطبیقیة المجلد
على مزائج المطاط الطبیعي دأألنبوب الداخلي إلطار الدیوانیة المعتم
محمد علي مطر
جامعة القادسیة، كلیة التربیة، قسم الكیمیاء
الخالصة
األحجـام يولكن بعض األنـواع مثـل األنابیـب ذ، تیلیتم تصنیع معظم األنابیب المطاطیة من مطاط البیو
green st)الكبیـرة تعتمــد علــى المطــاط الطبیعــي وذلـك الن القــوة الخضــراء العالیــة rength) تكــون مطلوبــة عنــد
وجـد (BIIR)والبیوتیـل البرومـي (NR)مـزائج مـن المطـاط الطبیعـي المعوعنـد اسـت. معاملة الخلطة غیر المفلكنـة
كن الحصول على القوة الخضـراء العالیـة فـي الخلطـة غیـر المفلكنـة وتحسـین عـدم النفاذیـة ومقاومـة الحـرارة من المم هأن
p ویمكـن الحصـول علـى افضـل الصـیغ بوجـود.لألنبوب غیر المفلكـن hr 50 مـن مطـاط(BIIR) للحصـول علـى
p م كما تم تحسین عدم النفاذیة باسـتخدا. الخواص المیكانیكیة المرغوبة hr 50 مـن مطـاط البیوتیـل البرومـي 75و
(BIIR) ومن جهة أخرى یؤدي مزج . في العجنات(BIIR) مع المطاط الطبیعـي(NR) إلـى تحسـین االحتفـاظ
مـع (NR)مـزائج مـن المطـاط الطبیعـي المعمن الضروري عند اسـت.بالهواء مع تضحیات مقبولة في القوة الخضراء
. (BIIR)تخفیض الكبریت كلما ازداد محتوى البیوتیل البرومي (BIIR)البیوتیل البرومي