Sains Malaysiana 42(4)(2013): 429–4

Sains Malaysiana 42(4)(2013): 429–434

Flame Retardancy and Mechanical Properties of Kenaf Filled Polypropylene (PP)

Containing Ammonium Polyphosphate (APP)

(Kerencatan Nyalaan dan Sifat Mekanik Kenaf Berpengisi Polipropilena

yang Mengandungi Ammonia Polifosfat (APP))

Atikah Ismail, Azman Hassan*, Aznizam Abu Bakar & M. Jawaid

Abstract

The effects of ammonium polyphosphate (APP) as flame retardant and kenaf as fillers on flammability, thermal and

mechanical properties of polypropylene (PP) composites were determined. Test specimens were prepared by using a co-
rotating twin screw extruder for the compounding process followed by injection molding. The flame retardancy of the

composites was determined by using limiting oxygen index (LOI) test. Addition of flame retardant into kenaf-PP composites

significantly increased the LOI values that indicated the improvement of flame retardancy. Thermogravimetric analysis

was done to examine the thermal stability of the composites. The addition of kenaf fiber in PP composites decreased

the thermal stability significantly but the influence of APP on thermal properties of the kenaf-filled PP composites was

not significant. The flexural strength and modulus of the composites increased with the addition of APP into kenaf filled

PP composite. The addition of APP into kenaf filled PP causes increase in the impact strength while increasing the APP

content in the kenaf filled PP composite show decrease in impact strength.

Keywords: Flame retardancy; mechanical properties; natural fiber polymer composites

Kesan ammonia polifosfat (APP) sebagai rencatan nyalaan dan kenaf sebagai pengisi ke atas sifat-sifat kebolehupayaan

nyalaan, terma dan mekanik bagi komposit polipropilena (PP) telah dikaji. Spesimen ujian telah disediakan dengan

menggunakan alat penyemprit skru berkembar untuk proses penyebatian dan diikuti dengan alat acuan suntikan.

Kerencatan nyalaan bagi komposit juga telah ditentukan dengan menggunakan alat ujian pengehad indeks oksigen (LOI).

Penambahan perencat kebakaran ke dalam komposit kenaf-PP meningkatkan nilai LOI yang menunjukkan kemajuan dalam

keupayaan rencatan nyalaan. Analisis termogravimetri dilakukan untuk memeriksa kestabilan terma bagi komposit.

Penambahan serat kenaf ke dalam komposit PP menurunkan kestabilan terma secara ketara tetapi sebaliknya, kesan APP ke

atas sifat-sifat terma bagi kenaf berpengisi komposit PP tidak mempunyai perubahan yang ketara. Kekuatan dan modulus

lenturan bagi komposit meningkat dengan penambahan APP ke dalam kenaf yang berpengisi komposit PP. Penambahan

APP ke dalam kenaf berpengisi PP juga menyebabkan peningkatan dalam kekuatan hentaman manakala peningkatan

kandungan APP di dalam kenaf berpengisi komposit PP menunjukkan penurunan di dalam kekuatan hentaman.

Kata kunci: Rencatan nyalaan; serat semula jadi komposit polimer; sifat-sifat mekanikal

Abstrak

Introduction

Recently, the acceptance of natural fiber as fillers in the

plastic industry has been growing extensively because of

their high specific properties, biodegradability, low cost

and environment friendly. The increasing utilization of

natural fiber composites in various applications such as

automotive components and aerospace industry is due to

economic advantage as compared with other conventional

filler or fiber. Kenaf also known as Hibiscus cannabinus is

a fast growing annual growth plant cultivated for its fiber

has been investigated as filler in thermoplastic composites

(Rowell et al. 1999).

Represents as a large fraction of world polymer usage,

polypropylene (PP) has been widely used in thermoplastic

industry due to its low cost and ease processing. Higher

stiffness at lower density and resistance to a higher

temperature when not subjected to mechanical stress are

the key properties for PP. Previous study has reported

that the addition of fiber reinforcement can enhance

the modulus and strength of PP (Sameni et al. 2003).

The use of reinforced polypropylene in electrical and

automotive engineering has increased due to its excellent

high modulus which enables it to replace conventional

materials in demanding engineering applications. There

are drawbacks in PP, when natural fiber was added in PP

due to poor compatibility between fiber and PP chances of

agglomeration while processing (Nabi Saheb & Jog 1999).

Compatibilizing agent required to be added into composite

to increase the interfacial bond between PP and natural

fiber. It is due to PP which consists of hydrophobic matrix

has less tendency to form interfacial bond with hydrophilic

properties of kenaf (Srebrenkoska et al. 2009). The

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addition of compatibilizing agent can accommodate polar

interaction such as acid-based interaction and becomes a

bridge to the hydroxyl groups on a natural fiber.

Nowadays, the demand of flame retardant materials

is increasing. PP burns rapidly with a relatively smoke-
free flame and without leaving a char re