Thermal and Flammability Properties of Polypropylene Filled Rice
Bran/Sepiolite Composite
SITI NADIA AINI GHAZALI1,a, ZURINA MOHAMAD1,b
1
Department of Polymer Engineering, Faculty of Chemical Engineering Universiti Teknologi
Malaysia, 81310 Skudai Johor, Malaysia
a
[email protected], [email protected]
Keywords: Propylene, Sepiolite, Rice Bran, Thermal Properties, Flammability, Composites
Abstract. Polypropylene that consist of different loading of rice bran (RB) (0wt%, 10wt%, 20wt%,
30wt%, 40wt%) and sepiolite (SEP) (0phr, 1phr, 2phr, 3phr, 4phr, 5phr) were prepared by twinscrew extruder followed by compression moulding. The effect of RB and SEP loading on the
thermal properties and flammability properties were studied through thermal gravimetric analysis
(TGA) and UL94 horizontal burning test (UL94HB) respectively. The result from TGA revealed
that RB content at 40%wt and SEP content at 4phr showed good thermal stability. The sepiolite
used for flammability properties had improved the flammability matrix; however, the amount of
SEP use in this study is not enough to improve the flammability of PP/RB composite.
Introduction
Polypropylene is a semi crystalline engineering thermoplastic and is known for its balance of
strength, modulus, and chemical resistance. It also has ability to carry heavy filler loadings such as
glass fibers, flame retardants or colorants. It has many potential applications in automobiles,
appliances; packaging, textile industry and other commercial products in which creep resistance;
stiffness and some toughness are demanded in addition to weight and cost savings. However, PP
has to overcome some drawbacks such as its maximum service temperature of 82˚C, high
flammability, thermal oxidation, and limited impact strength [1].
The effect of filler on the properties of composites depends on their level of loading, shape and
particle size, aggregate size, surface characteristic and degree of dispersion [2]. The incorporation
of inorganic particulate fillers into polymer matrix has been proved to be effective way of
improving the mechanical properties, thermal properties and in particular the toughness of PP. For
over 3000 years, natural fibers have been used to reinforce material. These natural fibers have
advantage that they are low cost fiber with low density and high specific properties. However, the
major issues of producing natural fiber polymer composite are the reduction in thermal stability and
increased in flammability properties [3].
The development of nanocomposites based on sepiolite (SEP) can be the subject of great interest
due to special physicochemical characteristic of sepiolite. Sepiolite, as a special needle-like clay
species of nanofiller that can be more easily dispersed in polymeric matrices due to its relatively
low external specific contact surface area compared with plateled-like clay of the same expect ratio
[4] and it exhibits extraordinary performance on the mechanical properties, thermal stability, flame
retardancy and barrier properties derived from its special structure [4-6].
Experimental
Materials
PP (TitanPro H6331) was purchased from Titan (M) Sdn. Bhd in resin form. The melt flow rate
(MFI) at 230˚C is 14 g/10 min and density is 0.9g/cm3. The rice bran used in this study was
obtained from local paddy field in Malaysia. The sepiolite nanofiber was purchased from
Shijiazhuang Kedahua Imp & Exp. Trade Co. Ltd. (Hebei, China). The sepiolite was in form of
white powder and its size was 44µm. Coupling agent used to compatibilized polypropylene matrix
and the fillers was maleic anhydride polypropylene (MAPP).
PP/RB/SEP Composite Preparation
The polymer composites were prepared by using different filler loading. Both formulations of
PP/RB composite and PP/RB/SEP composite is given in Table 1 and Table 2 respectively.
Table 1: Formulation of PP/RB loading
No.
1
2
3
4
5
PP [wt %]
100
90
80
70
60
RB [wt %]
10
20
30
40
Table 2: Formulation PP/RB with different SEP concentration
No.
1
2
2
3
4
5
6
PP [wt %]
100
70
70
70
70
70
70
RB [wt %]
30
30
30
30
30
30
SEP [phr]
1
0
1
2
3
4
5
Testing and Characterization
Thermal Gravimetric Analysis. The testing was carried out according to ASTM E1131 using
Perkin-Elmer TGA7 to study the thermal stability and thermal degradation behavior of the
composites. 5 to 10 milligram (mg) of the sample was placed in the specimen holder and raised the
furnace. Scanning rate used at 20˚C/min from 30˚C to 600˚C and the result was obtained in a plot of
weight loss versus temperature.
Flammability Test. The flammability test was conducted in horizontally test bar. The specimen
sizes that will be used for UL 94 standard are 125mm long x 13 mm wide. The specimens were
supported in a horizontal position and were tilted at 45˚ to the flame from a Bunsen burner for a
specified time. The specimen that burn slowly or self extinguish and do not drips flaming will rank
highest in the UL classification scheme.
Results and Discussion
Thermal Gravimetric Analysis. TGA was done to determine the thermal stability of the PP
composite that has been prepared. Figure 1 (a) revealed that the increasing of RB content had
increased the thermal stability on PP composite. For the SEP loading, it was found that the thermal
stability of the composite increase at 0 to 4 phr as showed in Figure 1 (b) but reduced at 5phr that
might due to the poor distribution and dispersion of SEP in composite material. 4 phr sepiolite
recorded the highest thermal stability of PP/RB composites.
(a)
(b)
Figure 1: The effect of (a) RB loading and (b) SEP loading on the thermal stability of PP
composites
Flammability. The increasing in RB loading had increased the flammability properties of PP/RB
composite as showed in Table 3 that represent the time taken for the specimen to burn from 25mm
mark to the 100mm passing mark . However, due to the silica content at higher RB loading at
30wt% had reduced the flammability properties of the composite. It is expected that, increase in
SEP loading will reduced the flammability properties. However, it is showed that the increasing in
SEP content up to 5phr have no improvement in the flammability of PP/RB composites. It is
believed that the amount of SEP was not enough. In addition, addition of sepiolite is proven to
enhance the flammability of the polymer as can be seen on the result of PP/ SEP even in 1 phr
loading as compared to virgin PP.
Table 3: Effect of (a) RB loading and (b) SEP loading on the flammability properties of
PP/RB/SEP composites
Formulation
100%PP 0%RB
10%RB
20%RB
30%RB
40%RB
(a)
Time [s]
129
114
111
127
120
Formulation
0phr
1phr
2phr
3phr
4phr
5phr
100%PP 1phr
Time [s]
127
114
116
123
123
117
145
(b)
Conclusion
To see the effectiveness of sepiolite as flame retardant in the PP/RB composites, the effect of
rice bran and sepiolite content of PP/RB composite on thermal and flammability properties were
studied. The result of thermal properties shows that the optimal amount of sepiolite in PP/RB
composites were obtained at 4phr sepiolite as it has higher thermal stability.
Acknowledgement
Great appreciations offered to Universiti Teknologi Malaysia (UTM) and Ministry of Education,
Malaysia (MOE) under the research Vot. No. Q.J130000.2544.06H05 for the supports and funding.
References
[1] Vargas, A. F., V. H. Orozco, F. Rault, S.Giraud, E. Devaux and B.L. Lopez, Influence of
Fiber-Like Nanofillers on the Rheological, Mechanical, Thermal and Fire Properties of
Polypropylene an application to Multifilament Yarn. Composites Part a-Applied Science and
Manufacturing. 41 (12) (2010) 1797-1806.
[2] Xie, X. L., R. K. Y. Li, Structure-Property Relationships of In-situ PMMA Modified Nano-sized
Antimony Trioxide Filled with Poly Vinyl Chloride Nanocomposites. Polymer, 45 (8) (2004) 27932802.
[3] Chapple, S. and R. Anandjiwala, Flammability of Natural Fiber-Reinforced Composites and
Strategies for Fire Retardancy: A Review. Journal of Thermoplastic Composite Materials. 23 (6)
(2010) 871-893.
[4] Bilotti, E., H. R. Fischer, T. Peijs, Polymer Nanocomposites based on Needle-Like Sepiolite
Clays: Effect of Functionalized Polymers on the Dispersion of Nanofiller, Crystallinity, and
Mechanical Properties. Journal of Applied Polymer Science. 107 (2) (2008) 1116-1123.
[5] Toldy, A. and P. Anna., Intrinsically Flame Retardant Epoxy Resin – Fire Performance and
Background- Part I. Polymer Degradation and Stability. 92 (12) (2007) 2223-2230.
.
[6] Xie, S. B. and S. M. Zhang, Preparation, Structure and Thermomechanical Properties of Nylon6 Nanocomposites with Lamella-Type and Fiber-Type Sepiolite. Composites Science and
Technology. 67 (11-12) (2007) 2334-2341.