ABSTRACT
Studies on solution of polystyrene /poly(methyl methacrylate) and poly(vinyl chloride) /poly(methyl methacrylate) were carried out to ascertain the compatibility of the polymer-polymer blends at temperature of 300C using chloroform as solvent. Viscometric values of relative viscosity (È rel) versus concentration of PS/PMMA were plotted, which gave S-shape indicating a heterogeneous mixture, whereas PVC/PMMA plot was observed to be homogenous mixtures indicating some level of linearity on different composition such as 0.4:1.6, 1.6:0.4, and 1.8:0.2 which may be used in polymer industry based on its area of applications. The experimental density of PS/PMMA blends were observed to be lower than the calculated values attributed to less chain packing in the blend solution as evidence of incompatibility, whereas PVC/PMMA showed an increase in experimental values than the calculated values which proved some level of compatibility. In addition, Fourier Transforms Infrared Spectroscopy method reveals that, PS/PMMA blend spectrum indicated no change in the position of either peak of aromatic ring of PS or lone pair peak of PMMA indicating incompatibility of the blend. Whereas there is existence of interaction between the carbonyl group (C=O) of PMMA and hydrogen atom of CHCl group of PVC in the entire composition indicating evidence of compatibility of the blend. Physiochemical analysis by use of FTIR method also reveals that poly (vinyl chloride)and Poly (methyl methacrylate) exhibited a positive molecular characteristics of apolymer blends. The viscometric and density methods have proved to be easy and reliable ways for determiningcompatibility of polymer blends in solution.
CHAPTER ONE
1.0 INTRODUCTION 1.1 Background of the study The field of polymer science and technology has undergone the fastest development in polymer blends through research and development. Polymers are macromolecules with a wide range of applications depending on their properties (high strength, light weight, good flexibility, special electrical properties, and resistance to chemicals, amenability for quick and mass production and for fabrication into complex shapes in a wide variety of colors). An outstanding array of polymers that have the potential to be used in fibers, adhesives, coatings, gels, foams, films, thermoplastics and thermoset resins abound in nature (Yu and Lin, 2006). Today, the applicability of these polymers has been extended beyond the range that can be obtained from single polymers due to the emerging field of blending. In the years ahead, polymers will continue to grow, and the growth from all indications will be not only from the development of new polymers, but also from the chemical and physical modifications of the existing ones. Besides, improved fabrication techniques will result in low-cost products.. Eventually, the challenges of recycling posed by environmental problems have led to further developments involving alloying and blending of plastics to produce a diversity of usable materials from what have hitherto been considered as wastes.
Blending of two or more polymers has become an important technique and is a well-established strategy for achieving and improving the cost performance ratio of polymeric products without the need to synthesize specialized polymer system (Janqueline and
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Kroschwizi,1997).Polymer blends generate new materials with a combination of properties not found in the pure polymers and blending is often a faster and more effective way of achieving the required properties with reduced cost of an expensive engineering thermoplastic as a determinant factor in loading-bearing applications. Most of the earlier work in this field was based on observation and experience, which many blends produced were of academic rather than commercial interest (Cheremisinaff and Nicholas,1990).The main advantages of the blended systems are simplicity of preparation and ease of control of physical properties by compositional changes (Acosta and Morales, 1996, Rocco et al, 2001). The concept of blending is about the use of good properties (favorable) of some polymers to correct the deficiencies (unfavorable properties) of other polymers. The process requires different knowledge and techniques than that used to develop new polymers as it requires, less input compared to synthesis of new product. The concept is all about the physical mixture of two or more structurally different homo or copolymers into a single continuous product(Janqueline and Kroschwizi, 1997)
Polymer blends are formed by the combination of two or more polymers with specific properties to produce a material with a compromise property. Thus, blending of polymers enables the production of new materials and composites with tailored properties for application in industries ranging from engineering to medicine. Apart from producing new materials with better properties for industrial applications, polymer blends have also proved to be economically and ecologically important (Vancover, 1993). Polymer blends have become a very important subject for scientific investigation in recent years because of their growing commercial acceptance. The enhanced activities of polymer blends are of producing
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advanced high performance polymeric materials and also the need for basic knowledge on their phase behavior. (Rhooet al, 1997, Oh and Kim, 1999) Determination of compatibility in polymer blends is important because manifestation of their superior properties depends on compatibility of homo polymers at a molecular level. Blending of polymers is widely accepted in the industry for the production of a polymeric materials with specific applications through an inexpensive route which otherwise is not attainable with a single polymer. One of the important controlling parameter in this case is the degree of compatibility of the polymers blended. However, the degree of compatibility is very much dependent over the interaction between the polymeric phases of the polyblend (Hirotsu et al., 2000)
Compatibilization is the process of modification of interfacial properties in immiscible polymer blends. It results in the formation of polymer alloys and is accomplished by physical or chemical means. Blends have traditionally been produced from different thermoplastics and thermosets obtained from both non-renewable and renewable sources. However, in the last two decades, blends from polymers from renewable resources have attracted an increasing amount of attention due to environmental concerns and the problem of non-biodegradability of thermoplastics such as polystyrene, poly (methyl methacrylate), polyethylene, poly (vinylchloride), poly (vinyl acetate) etc., which are almost impossible to deal with in our everyday life. Some of the disadvantages of biodegradable polymers and blends obtained from renewable sources are their dominant hydrophilic character, fast degradation rate and, in some cases, unsatisfactory mechanical properties, particularly under wet environments (Yu et al., 2006). Also, overdependence on polymers from renewable
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sources has greatly increased pressure on food sources as most renewable sources of polymers are sources of food and as a result food prices have increased and might continue to increase. (Rhooet al., 1999) In principle of this work, it is obvious to say that, the properties of synthetic polymers can be significantly improved by blending with natural polymers (Yu et al., 2006) The need, therefore for more compatibility research on improving the biodegradability and functional properties of traditional and versatile plastics like polystyrene, poly (vinyl chloride) and poly (methyl methacrylate) by blending them using viscometric, Fourier Transforms Infrared Spectroscopy and density method. These methods are quick and simple for compatibility studies in polymer blends because they require with no expensive equipment and yet offer a classification of the blends into compatible or incompatible(Rhooet al, 1997, Oh and Kim, 1999).
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Plates of polymer samples
I II III I = Polystyrene (PS) II = Poly (vinyl chloride)(PVC) III = Poly (methyl-methacrylate)(PMMA) 1.2:1 Polystyrene (PS): Polystyrene (PS) is a synthetic aromatic polymer made from the monomer styrene, a liquid petrochemical. It is a high molecular linear thermoplastic and is produced by free radical polymerization in bulk or suspension with peroxides or trace oxygen as initiators. It is an exothermic reaction(Fried, 2010).
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Polystyrene can be in rigid form and the presence of phenyl ring of benzene group introduces stiffness into the polymer chain. They are randomly packed in the chain, because of these the molecules are not aligned in the chain rather they are scattered and they are said to be amorphous. Styrene polymers have some unique properties which make them useful in a wide range of products. The single most important characteristic of general purpose styrene is that it is a glasslike solid below 1000C. (SimonE, 1939) The high heat of polymerization of styrene has greatly influenced the commercial development of the polymer as it has an excellent thermal stability which allows for high temperature fabrication. Above a glass- transition temperature of 100oC, the polymer chain (on a molecular level) has rotational freedom which allowslarge chain segment mobility, thus fluid enough to be easily shaped into useful forms.Below glass transition temperature (Tg), polystyrene possesses considerable mechanical strength, allowing it to be used in load bearing tasks.
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Styrene polymers are non -polar, chemically inert, easy to fabricate and water resistant. These characteristics allow them to be used in many applications. Polystyrene has the following mechanical and electrical properties; Density 1.062g/cm3 Crystalline 2.61% Glass transition temperature 100oC Resistivity 1020 – 1022 (Ω.M) Tensile modulus 2600 – 4900 GPa (Fried J. 2010)
Pure polystyrene is brittle, hard,and hard enough that fairly high performance products can be made by giving it some of the stretched properties for the materials in case of poly-butadiene rubber. It is a very inexpensive resin per unit weight and it has rather poor barrier to oxygen and water vapour and has relatively low melting point. Polystyrene is chemically inert and resistant to acids and bases but dissolved by many organic solvents. Different types of styrenes aregeneral high purpose (GHPS), high impact polystyrene (HIPS), low impact polystyrene (LIPS), and expandable polystyrene (EPS). Its area of applications areGHPS is used in production of cup, spoon, plates, packaging, transparent containers. HIPS are used in higher strength product like electrical appliances, refrigerator,engineering construction work, etc. EPS is used in light insulating materials, disposable plates, packaging materials, cutlery, meat trays, soup bowls, and fabricated work and LIPS is used in low impact strength product like food packaging Styrofoam and plastic containers(Fried J., 2010)
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1.2:2 Poly(vinyl chloride)
PVC is one of the versatile manmade materials ever created and it is the third most widely
produced plastic. Theannual world production is estimated at about 31 million tons(Fried J.
2010).The widely used polymers are polyethylene, polypropylene before polyvinyl chloride.
PVC is polymers of vinyl chloride and they are among the largest volume commodity
thermoplastics. It is a white, brittle solid, but can be plasticized to make it more flexible, low
cost, very durable, light weight, non-corrosive and has many unique features, in that it
doesn‟t rot, it is weather resistant and retains its shape at room temperature. At a very high
temperature, PVC can be reshaped which means it has great recycling possibilities.
Applications of plasticized PVC include wire coating, upholstery, floor coverings, film,
tubing, ceiling, plumbing, weather boarding, stickers, car body stripes, tarpaulins, coats,
jackets, shoes, bags apron, sport wears etc. Commercial PVC is a clear moderately tough, low
crystallinity, (Tg=870C, Tm=2120C) material with low to moderate molecular weight(25,000
to 150,000) g/mol-1
H H H H
C C C C
H Cl H Cl
Vinyl chloride Poly (vinyl chloride)
n
Polymerization of commercial-grade PVC is conducted by free-radical polymerization
principally by suspension polymerization techniques, although emulsion polymerizations
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arecommonly used and bulk polymerization. The toughness of PVC can be improved by blending with high impact resins such as methyl methacrylate-butadiene-styrene, acrylonitrile-butadiene-styrene etc. Some alternative stabilizers and additives are required for this application, so that they can have high weather and UV resistance, along with the brilliant white colour they are also known for extreme sports wear (such as skiing and diving suits). (Fried J. 2010) 1.2:3 Poly(methylmethacrylate) Poly (methyl methacrylate) (PMMA) is one of the well-knownbrittle materials. In order to consider the chemical and mechanical properties of PMMA, numerous studies on the improvement methods have been extensively carried out in the many years. PMMA is among other commercially important vinyl polymers, but commercial grade PMMA is an amorphous polymer of moderate Tg (1050C) with high light transparency and good resistance to acid and environmental deterioration (Fried J., 2010). It is commercially polymerized by free radical initiator or anionic alloy at low temperature to give highly isotactic (Glass Transition Temperature, (Tg) = 450C,)and (Crystalline Melting Temperature, (Tm)=1600C) or highly syndiotactic (Glass Transition Temperature, (Tg)=1150C,) and(Crystalline Melting Temperature, (Tm)=2000C) polymers.
PMMA is an economical alternative to polycarbonate (PC) when extreme strength is not necessary. Additionally, PMMA is not potentially harmful and subunits of it are found in polycarbonate. It is often preferred to others polymer because of its moderate properties, easy handling, processing, and low cost. The non-modified PMMA behaves in a brittle manner
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when loaded, especially materials exerted with force, and is more prone to scratching than
conventional inorganic glass. However, the modified PMMA achieves very high scratch and
impact resistance.The most common method for promoting the toughness of PMMA is
blending with the PVC. Conflicting data have been presented in literature concerning the
compatibility of polyvinyl chloride (PVC) and poly (methyl methacrylate) (PMMA) (Schurer
et al, 1975).
nCH2 C
C
O OCH3
CH3
CH2 C
OCH3
O
C
H
n
Methylmethacrylate Poly (methyl methacrylate)
PMMA is commercially polymerized by free radical initiators such as peroxide and azo
compounds in suspension or bulk polymerization. Bulk polymerization process is mainly
used in the manufacture of sheets, rods, hard contact lenses etc. while suspension process is
used in injection moulding products. It is sometimes called glass polymer because it is glassy
in nature after processing.
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Molecular formula
(C5O2H8)n
Molar mass(g/mol)
varies
Density
1.18 g/cm3
Melting point
160 °C (320 °F)
Refractive index
587.6 nm. (Fried J., 2010)
PMMA has the following properties such as optical clarity (official glass), heat resistance, high impact strength, brittle, glassy, poor crash resistance, rarely attacked by mineral acid, amendable to some additives, polymer stabilizer, etc.PMMA swells and dissolves in many organic solvents, and it also has poor resistance to many other chemicals. Nevertheless, its environmental stability is superior to most other plastics such as polystyrene and polyethylene, and PMMA is therefore often the material of choice for outdoor applications and high light transmission (Robeson and Portofrei, 2007). Its area of applications are outdoor weathering, construction of aquarium, hand eye lens, orthopaedic surgery to fix implants and remodel lost bone, transparent glasses substitute etc. PMMA, in a purified form, CDs and DVCs, LCDs back lights, is used as the matrix in laser dye-doped solid-state gain media for solid state dye lasers.PMMA has also been used extensively as a hybrid rocket fuel.PMMA technology is utilized in roofing and waterproofing applications. By incorporating a polyester fleece sandwiched between two layers of catalyst-activated PMMA resin, a fully reinforced liquid membrane is created in situ (Ibrahim and Kadum, 2010).
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1.2Statement of Problem: Majority of known polymeric materials are expensive,sometimes scarce, most of the polymer mixtures are immiscible,problem of determination of degree of compatibility, most solvents used in blending are toxic, and the toxic effect do not only affect living organism but also poison the earth. 1.3Aims of the study The aim of the study is to have a thorough understanding of the effect of molecular interactionand functional properties of polymer blends which helps in determining compatibility or incompatibility of PS/PMMA and PVC/PMMA using viscometric, Fourier transforms infrared spectroscopy and density methods. 1.4Objectives of the study The objectives of the study is to
(i) Determine the compatibility in polymer blends (PS/PMMA and PVC/PMMA) of various compositions using viscometry, density and Fourier transforms infrared spectroscopy methods.
(ii) Determine relative, specific, reduced and intrinsic viscosities of blend solutions using Oswald suspend level viscometer.
(iii) To investigate the functional groups associated with the adsorption of the blends of polymers using FTIR.
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1.5 Justification of the research It is obvious to say that understanding the properties of polymer blends will increase its applicability and could create new materials for industrialuse and exportation. It could also help in solving the environmental problems posed by the non-biodegradability of these widely-used thermoplastics and also contributing to the drive for the conversion of waste to wealth in the country ((Robeson and Portofrei, 2007). In addition, there are conflicting data in some literatures about polymer blends, there is need for more research on improving more polymer blends and justification of some these conflicting data.
1.6 Limitations of the study Limitation of the study is to determine thecompatibility of the polymer blends (PS/PMMA and PVC/PMMA) of various compositions using viscometric, Fourier transform infrared spectroscopy and density methods.Determineof relative, specific, reduced and intrinsic viscosities of blend solutions using Oswald suspend level viscometer was anotherimportant factor, which helps to investigate the functional groups associated with the adsorption of the polymer blends by the use of Fourier transform infrared spectroscopy.The results obtained supported most of the work in the literature of the polymer blends, although a use of chloroform as solvent is a new discovery of the study.
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