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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 7, July 2017, pp. 172–182, Article ID: IJMET_08_07_021

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=7

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

FABRICATION AND PERFORMANCE

ANALYSIS OF FLAME RETARDANT AND

NATURAL FIBERS REINFORCED

COMPOSITES

Devendiran. S, Venkatesan. K, Bharath. KSJ, Sri Anurag Sai. A and Sai Mohan. VNRT

School of Mechanical Engineering, VIT University,

VIT-Vellore, Tamil Nadu. India

ABSTRACT

In the present work an attempt has been made to fabricate and investigate the

performance of flame retardant and natural fibers reinforced composites. The matrix is

polypropylene (PP); sodium bicarbonate (FR1) and monoammonium phosphate (FR2)

are flame retardant materials and mango seed (MSF) and zea mays (ZMF) extracted

from agricultural waste are considered as natural fibers. Six samples of composites are

fabricated using compression molding and their tensile properties, impact test along

with flame retardancy tests are performed on the composites. Among the six samples, it

observed that for a 77% and 23% increase in tensile strength for PP/MSF/FR1/FR2

and PP/ZMF/FR1/FR2 that of PP/ZMF. The designation PP/MSF composite shows

good impact strength of value 3.85 J/mm2 that of other composites. Finally, it is

concluded that flame resistant of 36.3% is observed for PP/MSF/FR1/FR2 and rated V-

0 that of other composites. From SEM results, it is observed that the all fibers are well

dispersed without clustering features of fibers

Key words: Polypropylene, Flame retardants, mango seed fiber and Zea mays fiber

Cite this Article: Fabrication and Performance Analysis of Flame Retardant and

Natural Fibers Reinforced Composites, Devendiran. S, Venkatesan. K, Bharath. KSJ,

Sri Anurag Sai. A and Sai Mohan. VNRT. International Journal of Mechanical

Engineering and Technology, 8(7), 2017, pp. 172–180.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=7

1. INTRODUCTION

The natural fiber-strengthened polymer composite is being attractive both in their modern

applications and central research. This might be an inexhaustible, modest, totally or partially

recyclable and biodegradable [1-4]. It is widely used in several engineering applications

because low cost, high strength to weight ratio, low energy consumption negligible pollutant

emissions. In aerospace about 50% of the airframe is made from composites due to their high

specific strength, light weight and stiffness [5, 6]. Natural fibers are widely considered that of



engineered fiber in transportation, for example, autos, railroad mentors and aviation. In certain

businesses, for example, building and transport, diminished material combustibility is a key

necessity. Learning of the combustibility of regular fiber-strengthened composites and the

techniques used to enhance their fire resistance is important to guarantee their utilization in

these ventures [7-11]. Amid preparation of mango, by-items, for example, peel and portion are

created. Preparing of mango by-items lessens squander transfer issue. A restricted measure of

writing has been distributed on the fire resistant strategies and combustibility variable of regular

fibers based polymer lattice composites [12,13]. There should be an optimum amount of flame

retardant percentage for good mechanical properties [14].Two different additives of flame

retardants are compounded with the composites. The loading of flame retardants is limited to

20 wt% in order to leave a space for natural fibers as well as the polymer and to keep the overall

composite mechanical properties. The flame retardants are added in the ratio of 1:1[15,16]. In

the present work an attempt has been made to fabricate the various combinations of six

composites with matrix of polypropylene reinforced with flame retardants and natural fiber

from agricultural waste. The fabricated composites by compression molding are tested for

tensile and impact properties and flame retardant properties in order to determine their

applications for various fields.

2. EXPERMENTAL PROCEDURE

2.1. Material Selection

Polypropylene (PP), Mango seed fiber (MSF) and Zea mays fiber (ZSF), supplied by Go green

products-Chennai, is used as composite matrix and natural fibers. MSF and ZSF are extracted

from the seed of the fiber and corn outer leaf. Fibers are extracted from the waste of the fruit.

Sodium bicarbonate (FR1) and monoammonium phosphate (FR2) are considered as flame

retardants materials. A hardener is used to bind the materials and a releasing agent is applied

initially to the mould.

2.2. Treatment of fibers (MSF and ZSF)

Soluble treatment is the most preferred method amongst the most utilized synthetic treatment

of normal fibers when used to strengthen thermoplastics and thermosets. The critical

modification done by basic treatment is the interruption of hydrogen holding in the system

structure, in this way expanding surface harshness. This treatment evacuates a specific measure

of lignin, wax and oils covering the outer surface of the fiber cell divider, depolymerizes

cellulose and uncovered the short length crystallites. Expansion of watery sodium hydroxide

(NaOH) to regular fiber advances the ionization of the hydroxyl gathering to the alkoxide. In

this manner, basic handling straightforwardly influences the cellulosic fibril, the level of

polymerization and the extraction of lignin and hemicellulosic mixes [18]. Fibers are drenched

in NaOH solution for 5h. The treated fibers were washed and left to dry at a room temperature

for two days. This method is chosen because it is cost effective.

2.3. Composites Preparation

Composites were made using a stainless steel mould measuring 330 x 330 x 3 mm length, width

and depth, respectively. A releasing agent was sprayed and applied evenly onto the surface of

the mould. A mixture of polypropylene, natural fibers and flame retardants are distributed into

the mould and then placed between the electrically heated plates of a hot press at 50°C. The

two flame retardants of monoammonium phosphate and sodium bicarbonate are added in the

ratio 1:1 [19]. Table 1 shows the experimental plan for the preparation of six composites. Six

combinations of composites are: i) polypropylene with sodium bicarbonate and

monoammonium phosphate (PP/FR1/FR2), ii) Polypropylene with mango seed fiber

Fabrication and Performance Analysis of Flame Retardant and Natural Fibers Reinforced Composites


(PP/MSF), iii) polypropylene with Zea mays fiber (PP/ZMF), iv) polypropylene and mango

seed fiber with sodium bicarbonate and monoammonium phosphate (PP/MSF/FR1/FR2), v)

polypropylene and zea mays fiber with sodium bicarbonate and monoammonium

phosphate(PP/ZMF/FR1/FR2), vi) polypropylene, mango seed fiber and zea mays fiber with

sodium bicarbonate and monoammonium phosphate (PP/MSF/ZMF/FR1/FR2) were prepared.

Figure 1 shows the prepared six various combination of composites.

Figure 1 shows the photograph of the composites a) PP/FR1/FR2 b) PP/MSF c) PP/ZMF d)

PP/MSF/FR1/FR2 e) PP/ZMF/FR1/FR2 f) PP/MSF/ZMF/FR1/FR2

Table 1 Experimental plan for six combinations of composites

Composites

NO

Polymer/

fiber

Polymer

(wt%)

Fibers

(wt%)

FR mix

(wt%)

1 PP/FR1/FR2 80 0 20

2 PP/MSF 75 25 0

3 PP/ZMF 75 25 0

4 PP/MSF/FR1/FR2 65 15 20

5 PP/ZMF/FR1/FR2 65 15 20

6 PP/MS+ZMF/FR1/FR2 70 10 20

3. RESULTS AND DISCUSSIONS

3.1. Thermogravimetric analysis (TGA)

Figure 2 exhibits the outcome of TGA performed on the composites materials. The primary

thermal decomposition of all the six specimens occurs between 300 and 450ْC. The

decomposition of the composites takes place in the amorphous region where the weight loss

occurs due to decomposition of heavy components of the fiber [17]. The higher the degradation

temperature shows the increased thermal stability of the material. Hence, mango seed fiber

a) b) c)

d) e) f)



combined with flame retardants in polymer resin exhibits higher thermal stability that of other

composites.

Figure 2 TGA analysis for composites (A) PP/MS/FR1/FR2, (B) PP/FR1/FR2, (C)

PP/MSF+ZMF/FR1/FR2, (D) PP/MSF, (E) PP/ZMF/FR1/FR2, (F) PP/ZMF

3.2. Tensile strength

The tensile properties such as tensile strength, tensile modulus of the six combinations of

composites are performed on the developed specimen with 150*10*4mm were determined by

using the universal testing machine (UTM –ASTM D3039) with a cross head speed of 2mm/min

at room temperature. Figure 3 (a) and (b) show the relative tensile strength and young’s modulus

value of the six compositions.

Table 2 shows the tensile test results of all the compositions. The tensile properties of

composites are strongly depend on the matrix interface adhesion, stress/ strain behavior of the

fibers, flame retardants and or the matrix, and weight percentage ratio of the composite loading.

It is observed that the tensile strength is found to maximum of about 33.01MPa for the mango

seed fiber specimen where the fiber content is 15% and FR is 20%. The tensile strength of Zea

mays fiber reinforced polypropylene composite shows lower of 17.69MPa that of mango seed

fiber of same fiber content. The developed composites contain well bonded MSF, good MSF

dispersion and strong polypropylene/MSF adhesion for effective transfer of stress. This

observation is in agreement with earlier research. From the Table 2, the specimen PP/FR has

lowest tensile stress when compared to other specimen. This shows that the addition of fibers

increase the tensile property of the composites. It can be seen that addition of flame retardants

of limited amount also increases the tensile properties of the composites. From the Figure 9, it

is observed that there is 77.1% increase in tensile strength value of PP/MSF/FR1/FR2 when

compared to the PP/MSF whereas it is 23.6% for PP/ZMF/FR1/FR2 when compared to the

PP/ZMF.

Table 2 shows the young’s modulus results of all the compositions. The increase of tensile

modulus for the polypropylene matrix to 1107 MPa that of other composites may be attributed

to the higher crosslink density of the polypropylene and good distribution of MSF/flame

retardant in polypropylene matrix. The uniformity of MSF distribution has efficiently hinders

the chains movement during deformation leading to high fibers orientation. This mechanism

will help to increase the toughness of the composite as well as the tensile modulus. These results

are in agreement with the earlier research. The tensile strain of the developed composites

increases marginally from 2.98 to 1.84 with the addition of the MSF+ZMF (Table 3) this is

MSF+ZMF because as the present weight of MSF+ZMF additions decreases, the tensile strain

of the MSF+ZMF and the polypropylene/MSF interface is sufficient. This means that the MSF



could pin down the crack formed effectively there by the velocity if crack propagation through

the PP/MSF+ZMF/ FR1/FR2increases. Similarly, the tensile modulus is found to be decrease

from 1107.75 MPa to 1046.57 MPa this is because as the weight percent of MSF+ZMF

additions found to be decreased. From the analysis of tensile test, the PP/MSF/FR1/FR2

provided the better properties than that of other composites with a maximum load of 1287.49N.

Figure 3 Variation of tensile strength (a) and tensile modulus (b) with weight percent of fiber and

flame retardant additions

Table 2 Tensile test results for six combinations of composites

COMPOSITES

NO

POLYMER/

FIBER

LOAD AT

PEAK (N)

ULTIMATE

STRESS

(STANDARD) (MPA)

TENSILE STRAIN

AT MAXIMUM

LOAD (%)

TENSILE

MODULU

S (MPA)

1 PP/FR1/FR2 674.99 17.305 1.94 892.01 2 PP/MSF 727.02 18.639 1.94 960.77 3 PP/ZMF 690.34 17.697 2.00 884.85 4 PP/MSF/FR1/FR2 1287.49 33.011 2.98 1107.75 5 PP/ZMF/FR1/FR2 853.71 21.886 2.00 1094.30 6 PP/MS+ZMF/FR1/FR2 751.16 19.257 1.84 1046.57

3.3 Impact strength

The impact properties of polymer composites depend strongly on resin matrix with the natural

fiber interface adhesion, behavior of the matrix and volume of composite. The impact properties

vary with the weight percentage of the fiber to the flame retardants are shown in Figure 4. The

composite of composition with polypropylene and flame retardants is 2.29 (J/mm2), whereas

the composite included with zea mays resulted as 3.31(J/mm2). As the mango seed fiber is

a)

b)



stronger than the zea mays fiber, in this test it is observed, the highest impact strength resulted

for the composite of composition of polypropylene and mango seed fiber as 3.85 (J/mm2).

Though the flame retardants decrease the impact strength they were used as resistant for the

flame.

Figure 4 Variation of impact strength with weight percent of fiber and flame retardant additions

3.4 Flammability Test

Limited oxygen index (LOI) and Underwriters laboratory test (UL94) are done to ensure the

flame retardancy of the composites. LOI gives very important information about relative

flammability of composites. Table 3 describes the LOI and UL94 vertical burn test results of

the composites. The size of the specimen for UL94 vertical burn test is 125 mm long x 13 mm

wide x 3mm thickness. For the vertical UL94 burn test, there are three flame ratings namely V-

0, V-1 and V-2. V-0 flame rating is considered more flame resistant than the other two ratings.

It can be seen that PP/MSF/FR1/FR2 is having highest LOI value when compared to other

fibers. Addition of flame retardants significantly improved the flame retardant properties of

natural fiber reinforced polypropylene composites. The addition of flame retardants to the

mango seed fiber increased the LOI value from 31.6% to 36.3%. Even for zea mays fiber it

increased from 23.8% to 30.1%. But for the sample PP/MSF+ZMF/FR1/FR2 the LOI value is

32.4% and is less than the PP/MSF/FR1/FR2. This shows that addition of zea mays fiber to

mango seed fiber reduce the flame retardant property of the composite. Here FR is limited to

20% for all the samples as increase in the flame retardants may reduce other mechanical

properties [20]. Figure 5 shows that there is 12.9% increase in LOI value of PP/MSH/FR when

compared to the PP/MSF whereas it is 26.4% for PP/ZMF/FR1/FR2 when compared to the

PP/ZMF. Figure 5 shows that PP/FR1/FR2, PP/MSF/FR1/FR2 and PP/MSF+ZMF/FR1/FR2

exhibits V-0 rating, PP/MSF and PP/ZMF/FR exhibits V-1 rating and PP/ZMF exhibits V-2

rating. This concludes that PP/ZMF is the least flame resistant when compared to the other

composites and the composites which exhibitV-0 rating are good flame resistant.



Figure 5 The LOI values and UL-94 results of all the compositions

Table 3 LOI and UL94 test results

COMPOSITES

NO

POLYMER/

FIBER LOI (%) DRIPPING UL94 RATING

1 PP/FR1/FR2 34.8 NO V-0 2 PP/MSF 31.6 NO V-1 3 PP/ZMF 23.8 YES V-2 4 PP/MSF/FR1/FR2 36.3 NO V-0 5 PP/ZMF/FR1/FR2 30.1 NO V-1 6 PP/MS+ZMF/FR1/FR2 32.4 NO V-0

Figure 6 shows the photograph of the flammability Test (a) PP/FR1/FR2 (b) PP/MSF (c) PP/ZMF (d)

PP/MSF/FR1/FR2 (e) PP/ZMF/FR1/FR2 (f) PP/MSF/ZMF/FR1/FR2

The surface finish was observed for the six compositions by the microscopic structural

analysis and as shown in Figure 6. It is observed that the surface finish of the natural fiber are

found be better in texture. Scanning electron microscope (SEM) of all the six combination

composites is taken and shown in Figure 7. It is observed that the good polymer impregnation

around the fibers without any lack of adhesion between the mango fibers, zea mays fibers,

polymer matrix. Also the fibers are well dispersed without clustering features of fibers.

a) b) c)

d) e) f)



Figure 7 SEM micrograph for Zea mays and mango seed fiber reinforced composite

5. CONCLUSION

In the present work tensile, impact and flammability experiments were conducted on various

combinations of six composites to find the effect of flame retardant and natural fibers on

Polypropylene. The parameters such as tensile properties, tensile modulus, limited oxygen

index (LOI) and Underwriters laboratory test (UL94) were measured. A tensile property of

polypropylene is increased of about 77% with addition of mango seed (MSF) and sodium

bicarbonate (FR1) and monoammonium phosphate (FR2) on polypropylene. Impact strength

results are quite opposite to the tensile properties where the addition of flame retardants

decreases the impact strength of the composites. Mango seed fiber shows good flame retardant

properties when compared to the zea mays fiber on the addition of flame retardants. The flame

retardants are added in the ratio 1:1 and change in FR ratio gives different results. From SEM

results, it is observed that the good polymer impregnation around the fibers without any lack of

adhesion between the mango fibers, zea mays fibers, polymer matrix. Also the fibers are well

dispersed without clustering features of fibers.

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