Poly vinyl chloride, which is normally abbreviated as PVC, is widely used because it is cheap, lasting, and flexible. There are many utilizations of PVC. As a difficult thermoplastic, PVC is used as edifice stuffs, pipe, plumbing, and many other applications. The thing should be considered in utilizing PVC is safety and environmental issues. Blending PVC with natural fibers is an interesting option. This could cut down the environmental incommodiousness while conserving its advantages. The chief challenge in the research on natural fibre/Polymer complexs is the hapless compatibility between the fibers and the matrix. The reinforcement consequence of natural fibers in PVC matrix depends on the compatibility. When they are assorted with PVC, some natural fibers may move as reenforcing stuffs while other natural fibers merely act as filler, which are non lending to mechanical strength betterment. However, by and large the natural fibers give positive facet to the stiffnes of the complexs while diminishing the denseness. Hence, beside the environmental friendliness, the natural fiber reinforced PVC complexs have a great stiffness to burden ratio compared to the original PVC.
Keywords: natural fiber, poly ( vinyl chloride ) , complexs
Polymers have substituted many of conventional stuffs, particularly metals, in assorted applications due to the advantages of polymers over conventional stuffs. They are used in many applications because they are easy to treat, high productiveness, and low cost in combination of their versatility. However, for some specific utilizations, some mechanical belongingss, e.g. , strength and stamina of polymer stuffs are unequal. Assorted attacks have been developed to better such belongingss. In most of these applications, the belongingss of polymers are modified utilizing fillers and fibers to accommodate the high strength/high modulus demands. Fibre-reinforced polymers have better specific belongingss compared to the conventional stuffs and happen applications in diverse field, runing from contraptions to spacecraft ( Saheb and Jog 1999 )
There are many utilizations of PVC. As a difficult thermoplastic, PVC is used as edifice stuffs, pipe, plumbing, and many other applications. It besides can be made softer and more flexible by the add-on of plasticiser. Beside the cost of the natural stuffs, there are several grounds why PVC has the broadest scope of application and its usage has grown more quickly than of other plastics. It is because PVC is easy to manufacture and it can last for long clip. PVC has outstanding chemical opposition to broad scope of caustic fluids and offer more strength and rigidness than most of the other thermoplastics. It is besides unambiguously antiphonal to functional additives which permit the coevals of stiff and flexible merchandises, utile in designed technology application ( Nass 1985 and Willoughby 2002 )
On the other manus, there are several safety and environmental issues on PVC. Vinyl-chloride ( VC ) is reported can do serious wellness job. The anesthetic belongings of VC was recognized in early 1930s and has been investigated by several workers. At concentration much above 8 to 12 % , it may kill animate beings quickly. If an surplus of VC is inhaled, the liver capacity is overwhelmed and leting tumour formation to happen. It is besides reported as carcinogen ( Nass 1985 ) . PVC is besides presently suspected as a contaminant stuff. When it is processed, or when it decomposes, it produces some substances that can damage the ambiance, for illustration H chloride and dioxins. The issues have provoked environmental groups to knock refering its mass use ( Ayora et al. 1997 ) .
Blending PVC with natural fibers, as natural fibres/PVC complexs, is an interesting option due to the “ ecological friendliness ” of natural fiber. This could cut down its incommodiousnesss while conserving its advantages ( Ayora, et Al. 1997 ) . Furthermore, during the last decennary natural fibers have late attracted the attending of scientists and engineers because of the advantages that these fibers provide over conventional reinforcement stuffs, glass-fibres. The advantages are ( Bledzki and Gassan 1999 ) :
Natural fibers are a renewable natural stuff and that will be available continuously.
When they are subjected to a burning procedure or landfill at the terminal of their life rhythm, the released sum of CO2 of the fibers is impersonal with regard to the assimilated sum during their growing.
The scratchy nature of natural fibers is much lower compared to that of glass-fibres, which leads to advantages with respect to proficient, material recycling or procedure of composite stuffs in general.
The denseness of natural fibers is much lower compared to glass-fibres. It means there is possible advantage of weight economy.
In this reappraisal, the potency of PVC as natural fiber composite matrix and some attempts to better the mechanical belongingss of natural fibres/PVC complexs will be discussed.
Mechanical and Physical Properties of Poly ( vinyl chloride )
PVC is a member of vinyl polymers. It has the vinyl group ( CH2=CH- ) . The other illustration of group members are polyethylene, polypropene, polystyrene, polyvinyl ethanoate, polymethyl methacrylate and polyvinylidene chloride. Through common use, the word vinyl by and large refers to PVC and its copolymers. Vinyl chloride ( VC ) monomer, CH2=CHCl, is a colourless gas possessing a faintly sweet smells which can do anesthesia at high concentrations ( Sarvetnick 1977 ) .
Although there is guess that acetylene derived from coal may go the major hydrocarbon used, the beginning of hydrocarbon for VC has been ethylene in recent times. The production of VC besides needs Cl, produced chiefly from common salt ( NaCl ) . On a weight footing, Cl histories for 56.8 % of the entire weight. PVC is therefore less affected by the cost of crude oil and natural gas so other polymer. Since the monetary values of crude oil and natural gas likely will be still lifting in the hereafter more quickly than Cl monetary values, PVC will still less expensive compared to other polymers ( Nass 1985 ) .
Beside the cost of the natural stuffs, there are several grounds why PVC has the broadest scope of application and its usage has grown more quickly than of other plastics. It is because PVC is easy to manufacture and it can last for long clip. PVC has outstanding chemical opposition to broad scope of caustic fluids and offer more strength and rigidness than most of the other thermoplastics. Tensile emphasis of PVC is 40-60 MPa, its modulus of snap is 2-7 GPa with denseness of 1380-1410 kg/m3. PVC is besides unambiguously antiphonal to functional additives which permit the coevals of stiff and flexible merchandises, utile in designed technology application ( Willoughby 2002 ) .
Many writers have reported the belongingss of PVC-natural fiber complexs. So far, at least there are nine discrepancies of natural fibers that have been used for filler/reinforcing stuffs. They are wood ( Mengeloglu, Mauana and King 2000 ; Zhao, et Al. 2006 ; Jiang et Al. 2004 ) , bamboo ( Ge, Li and Meng 2004 ) , pine ( Ge, Li and Meng 2004 ) , rice straw ( Kamel 2004 ) , sisal ( Djidjelli, et Al. 2007 ) , oil thenar ( Abu Bakar, Hasan and Yusof 2006 ) , sugarcane bagasse ( Zheng, et Al. 2007 ) , banana ( Zainudin, et Al. 2007 ) , and coconut ( Leblanc, et Al. 2007 ) .
Mechanical and Physical Properties of Natural Fibres
Natural fibers may be classified in two wide classs: Non-wood fibers and wood fibers. Non-wood fibers divided into ( Mohanty, et Al. 2005 ) :
Straw, illustrations: maize, wheat, and rice straw ;
Bast, examples: deccan hemp ( Hibiscus cannabicus ) , flax ( Linum usitatissimum ) , jute ( Corchorus ) , ramie ( Boehmeria nivea ) , and hemp ( Cannabis sativa ) ;
seed/fruit, illustrations: sisal ( Agave sisalana ) , pineapple ( Ananas comosus ) foliage, and henequen ( Agave fourcroydes ) fibre ;
grass fibers, illustration: bamboo fiber, exchange grass ( Panicum virgatum ) , and elephant grass ( Erianthus elephantinus ) ;
Natural fibers in the signifier of wood flour have besides been frequently used for readying of natural fiber complexs. The characteristic values of natural fibers vary from one fiber to another. Some of the characteristic values are the cellulose content in the fiber, the grade of polymerisation of the cellulose and the microfibrils angle fibers. Higher cellulose content, higher grade of polymerisation and a lower microfibrillar angle will impact higher tensile strength and modulus. The fluctuations in the characteristic value exhibit the fluctuations in mechanical belongingss both along the length of an single fiber and between fibers ( Jayaraman 2003 ) .
Natural fibers besides have non-uniformity and fluctuation of dimensions, even between single workss in the same cultivation. To bring forth fibers suited for specific terminal merchandises, the assorted types of natural stuff are separated. Bast or root fibers, for illustration, are chiefly used in the fabric or rope industries because of the length of the fibers. Bast straw is non separated into individual fibers but into fibre packages, which may incorporate 1000s of individual fibers. In contrast with it, wood is normally separated into individual fibers or really little fiber packages accommodating the peculiar demands of the mush, paper or board industries. Therefore, there are a great figure of challenges for choosing fibers in different dimensions and belongingss ( Olesen and Plackett 1999 ) .
By and large, the denseness of natural fibers is much less than that of E-glass fiber. The specific strength and specific modulus of natural fibers are comparable or even superior to E-glass fibers. Many natural fibers have higher specific modulus compare to E-glass fibers. Hence, there is an chance for utilizing the natural fibers to replace the E-glass fiber ( Drzal, et Al. 2004 )
The challenge now is how to do the natural fibers compatible plenty with the PVC. When they are used as supports of man-made polymers, there is a major drawback of the application. Due to the presence of hydroxyl and other polar groups on the surface and throughout natural fiber, wet soaking up can be high. It leads to hapless wet-ability by the polymers and weak interfacial bonding between fibers and hydrophobic polymers, as the matrix ( Brouwer 2000 ) . In order to develop complexs with better mechanical belongingss, it is necessary to work out the jobs by suited interventions to heighten the compatibility between fibers and the matrices ( Brouwer 2000 and Drzal et Al. 2004 ) .
Compatibility and Reinforcement Effect of Natural Fibre in Polymer Matrix
Development sugar cane bagasse reinforced PVC complex will confront a major challenge in using natural fiber as reenforcing stuff in man-made polymer complex, which is compatibility issue. Due to the presence of hydroxyl and other polar groups on the surface and throughout natural fiber, wet soaking up can be high. It leads to hapless wet-ability by the polymers and weak interfacial bonding between fibers and hydrophobic polymers, as the matrix ( Drzal, et Al. 2004 ) .
Many attempts have been carried out to work out this job. By and large, surface intervention should be carried out in order to heighten the compatibility. Alkali, acrylic acid, maleic anhydride, and other acids and anhydrides intervention are the illustration of the surface interventions ( Kokta, et Al. 1990a ; Vilay, et Al. 2008 ) . Another surface intervention is a matching agent add-on. Poly [ methylene poly ( phenyl isocyanate ) ] ( PMPPIC ) has been reported as one of suited matching agents for natural fiber reinforced PVC complexs. The -N=C=O group of isocyanate may undergoes a chemical reaction with -OH group of cellulose or it counterpart lignin to develop strong interface between PMPPIC and natural fibers. On the other manus, the non-polar benzine ring of PMPPIC can interact with PVC ( Maldas, et Al. 1989 ; Joseph, et Al. 2002 ) . Figure 1 shows conjectural chemical construction of cellulose fibre-PMPPIC-PVC in the interfacial country.
Figure 1 Conjectural chemical construction of cellulose-PMPPIC-PVC
Due to the compatibility issue, regulation of mixtures fail to demo sensible understanding with most experimental tensile belongingss of natural fiber complexs. The regulation of mixture is normally used to depict the strength of unidirectional uninterrupted fiber reinforced complexs. It is assumed that unvarying strain status exist in both matrix and fibers ( Kalaprasad, et Al. 1997 ) . In another word, the regulation of mixture will hold the experiment consequence merely if unidirectional uninterrupted fibers are used and there is a good compatibility between fibers and matrix.
The emphasis transportation in a composite depends mostly on fibre orientation, stress concentration at the fiber ends, fibre length, interfacial shear strength and compatibility between fiber and matrix, etc. Kalaprasad et Al. ( 1997 ) reported that there are two theoretical accounts show really good correlativity with experimental consequence of natural fiber reinforced polymer complexs. They are Hirsch theoretical account and modified Bowyer and Bader theoretical account.
Harmonizing to Hirsch theoretical account, modulus of snap and tensile strength are calculated utilizing the undermentioned equations ( Kalaprasad, et Al. 1997 ) :
( 1 )
( 2 )
where ten is a parametric quantity which determines the emphasis transportation between fiber and matrix.
The undermentioned equations are used for ciphering modulus and tensile strength in modified Bowyer and Bader Model ( Kalaprasad, et Al. 1997 ) :
( 3 )
( 4 ) where k1 is fibre orientation factor and K2 is fibre length factor, which is depending on critical fiber length.
However, there is a possibility that fiber is merely moving as filler, non as reenforcing stage as reported by Vazquez et Al. ( 1999 ) . The strength of untreated bagasse fibre-polypropylene complexs decreased when fibre content increased. The strength of the complexs was even lower than the matrix entirely. In this instance, all of expression ( 1 ) to ( 4 ) can non be used. The application of Nicolais-Narkis equation is preferred:
( 5 )
where K is a parametric quantity that depends on fibre/matrix adhesion.
Reinforcement Effect of Natural Fibre in PVC Matrix
Previous research studies represented in table 1 show that besides PMPPIC treated wood-PVC and benzoic acid treated sugarcane bagasse-PVC complexs, the natural fibers act merely every bit filler in PVC complexs. Fibre content gives negative consequence to the tensile strength of the complex. The PMPPIC intervention seems suited for wood-PVC complex as it can alter the fiber content support consequence from negative to positive. It means, with PMPPIC intervention, the strength of composite is increasing with the increasing of the fiber content, as a consequence of chemical reaction between the -N=C=O group of isocyanate with -OH group of cellulose or it counterpart lignin:
-NCO + HO-A®NH-COO-
Hence, the strong interface between fibers and PVC were developed as described in figure 1.
It can besides be seen that by and large the fiber content gives positive consequence to the stiffness ( E ) of natural fiber PVC complexs.
Table 1. Consequence of fiber content to mechanical belongingss of natural fiber PVC complexs
Fibre Content Reinforcement Effect*
Kokta et Al. 1990a ; Djidjelli et Al. 2002 ; Ge et Al ( 2004 )
Maldas et Al. 1989 ; Kokta et Al. 1990b ; Saheb and Jog 1999
Ge et al. 2004
Djidjelli et Al. 2007
Abu Bakar et Al. 2005
Abu Bakar et Al. 2005
Crespo et Al. 2008
Zheng et Al. 2007
* + represents increasing of the belongings with the increasing of fiber content
– represents decreasing of the belongings with the increasing of fiber content
Applications and Ageing of Natural Fibre Reinforced PVC Composites
There are many possible applications of natural fiber reinforced PVC complexs. It can be straight moulded into a concluding form, or pelletised and sold to third party processors in bulge, injection, or compaction molding ( Jones, 2004 ) . In recent old ages, the tendency of natural fiber complexs use has moved from thermoset to thermoplastics, including PVC. Demand has taken off for several merchandises, such as decking, window/door profiles, fencing/siding/railings, furniture, flooring, automotive inside parts, pallets/crates/boxes, and marine constituents ( Kline & A ; Company, inc. , 2000 ) . Some of those merchandises are already being manufactured, whereas others are the positive result of feasibleness surveies ( Rijswijk et al. , 2003 ) .
It is common issue that there are alterations in polymer belongingss due to long-run ripening. However, it has been investigated that the elongation at interruption of PVC indoor profiles was non changed after 20 and 25 old ages of service life compared to the value when the profiles were new ( Yarahmadi et al. , 2003 ) .
With the broad scope possibility of applications and good belongings stableness due to long-run ripening, natural fiber reinforced PVC is a possible stuff to be developed.
The usage of natural fiber as reenforcing agent in PVC based complexs were reviewed from point of views of position and recent development in general, construction and belongingss of natural fiber, fibre surface alterations, and physical and mechanical belongingss of natural fibers based PVC complexs. Wood fibers have largely used as supports in PVC based complexs. Due to the low denseness and high specific belongingss of these natural fibers, complexs based on these fibers may hold really good deductions in the automotive and furniture industry. The usage of natural fibers as a beginning of natural stuff in PVC plastic industry non merely provides a renewable resource, but could besides bring forth a non-food beginning of economic development for farming and rural countries. However, to obtain a good interfacial bond between filler and matrix, it is necessary by the add-on of suited qualifier agent. Poly [ methylene poly ( phenyl isocyanate ) ] ( PMPPIC ) is one of suited matching agents can be utilized for natural fiber reinforced PVC complexs. Once the interfacial bonding job is solved, there is broad scope possibility of applications.