Polymer Fillers and Stiffening Agents

Applications and Non-traditional Alternatives

Chris Defonseka

• Publisher: De Gruyter
• Year: 2020
• eBook ISBN: 9783110670103
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

This book presents both established and emerging technologies which show the immense possibilities of using non-traditional fillers and stiffening agents in the plastics industry. After an introduction to basic polymer chemistry, a range of non-petroleum-based fillers and stiffening agents for polymer products are identified and their optimal applications given.

1 Basic chemistry

1.1 Introduction

Chemistry is the study of the composition of matter and how it changes. The two broad areas of chemistry are organic and inorganic. Organic chemistry deals with matter that contains the element carbon, whereas inorganic chemistry is the study of matter, mineral in origin. The term ‘organic’ originally meant compounds of plants or animals but now it also includes many synthetic materials that have been developed through research. One such group of synthetic organic materials is called ‘plastics’.

Chemical theory is based on the fact that all matter consists of base substances called ‘elements’. Matter is defined as anything that has mass (weight) and occupies space and may exist in the form of a solid, liquid or gas. The structures of matter are composed of small particles called ‘atoms’, which combine to form larger particles called ‘molecules’, and when they combine, they form ‘compounds’. The smallest particle is an atom, and a molecule is formed by two or more atoms. Atoms consist of particles called ‘neutrons’, ‘protons’ and ‘electrons’. The atoms of each element differ in the number of particles they contain. Thus, no two elements will have identical atoms. Neutron is a particle with no electrical charge, whereas protons are positively charged. Both occupy the centre of an atom called the nucleus. Electrons are negatively charged particles and are in orbit around the nucleus. The negative charge of the electrons moving around the nucleus is equal to the positive charge of the protons in the nucleus. Therefore, for all elements, an atom is electrically neutral. If an atom gains an electron, it becomes electronegative (a negative ion) and if an atom loses an electron, it becomes electropositive (a positive ion). An ion is an atom that has gained or lost one or more electrons.

Each element has an atomic number, which is the number of protons in the nucleus. The atomic weight of an element is the mass of an atom of that element compared with the mass of an atom of carbon. The molecular weight mass or weight is the total atomic weights of the atoms making up the molecules. The periodic table lists all elements and also shows their atomic and molecular weights. When single elements join together, they form compounds. Some of the most common elements that join together to form plastics are hydrogen, oxygen, nitrogen, chlorine, fluorine, silicone, carbon, and so on.

1.2 Organic chemistry basis

Organic chemistry is the study of the structures, properties, compositions, reactions, preparation by synthetic or other means of carbon-based compounds, hydrocarbons, and their derivatives. These compounds may contain any number of other elements, including hydrogen, nitrogen, oxygen, the halogens as well as phosphorous, silicon, and sulphur. Organic compounds are structurally diverse. The range of applications of organic compounds is enormous. They form the basis or of constituents of many products such as plastics, drugs, food, petrochemicals, explosives, paints, and many more.

1.2.1 Properties

Physical properties of typical organic compounds of interest include quantitative and qualitative features. Qualitative data includes melting point, boiling point and index of refraction, whereas qualitative properties include door, colour, consistency and solubility.

1.2.2 Melting and boiling properties

In contrast to many inorganic compounds, organic materials melt and boil. These properties provide crucial information about the identity and purity of organic compounds. This information correlates with the polarity of the molecules and their molecular weights. Some organic compounds, especially symmetrical ones, undergo sublimation (transition from a solid phase to a gas phase without passing through an intermediate liquid phase). A well-known example of a sublime organic compound of this nature is p-dichlorobenzene, the odiferous constituent of modern-day mothballs. Organic compounds are usually not very stable at temperatures ≥ 300 °C (572 °F), although there are exceptions.

1.2.3 Solubility

Neutral organic compounds tend to become hydrophobic, meaning they are less soluble in water than in organic solvents. Exceptions include organic compounds that contain ionisable groups, as well as low molecular weight alcohols, amines and carbolic acids, where hydrogen bonding occurs. Organic compounds tend to dissolve in organic solvents. Solvents can be pure substances such as ether or mixtures. Mixtures can be paraffinic solvents such as the various petroleum or tar fractions obtained by physical separation or by chemical conversion. The degree of solubility in different solvents is dependent upon the solvent type and on the functional groups.

1.2.4 Structural presentation

Organic structures can be described by drawings, structural formulae, combinations of drawings and chemical symbols. The line-angle formula is simple and unambiguous. In such a system, the endpoints and intersections of each line represent one carbon atom, and hydrogen atoms can be notated explicitly or assumed to be present as implied by a tetravalent carbon. The depiction of organic compounds with drawings is greatly simplified by the fact that carbon in almost all organic compounds has four bonds, oxygen two, hydrogen one and nitrogen three.

1.2.5 Functional groups

The concept of functional groups is central to organic chemistry as a means to classify structures and for predicting properties. A functional group is a molecular model, and the reactivity of that functional group is assumed (within limitations) to be the same in various molecules. Functional groups can have a decisive influence on the chemical and physical properties of organic compounds. Molecules are classified on the basis of their functional groups.

For example, alcohols have the sub-unit C-O-H. All alcohols tend to be hydrophilic (usually from esters) and can be converted to the corresponding halides. Most functional groups feature heteroatoms (atoms other than carbon, functional groups and hydrogen). Organic compounds are classified according to their functional groups, alcohols, carbolic acids and amines.

1.2.6 Aliphatic compounds

Aliphatic hydrocarbons are sub-divided into three groups of homologous series according to their state of saturation as follows:

• Paraffin – which are alkanes without any double or triple bonds.
• Olefins and Alkenes – which contain one or more double bonds (e.g. polyolefin).
• Alkynes – which have one or more triple bonds.

The rest of the groups are classified according to the functional groups present. Such compounds can be straight-chained, branch-chained or cyclic. The degree of branching affects characteristics such as the octane number as in the petroleum industry. Saturated compounds and unsaturated compounds exist as cyclic derivatives. The most stable rings contain five or six carbon atoms but large rings such as macro-cycles, and smaller rings are also common.

1.2.7 Aromatic compounds

Aromatic hydrocarbons contain double bonds. The most important example is benzene, the structure of which was formulated by a chemist who first proposed delocalization (also known as resonance principle) to explain its structure. For conventional cyclic compounds, aromaticity is conferred by delocalized electrons. Particular instability (anti-aromaticity) is conferred by conjugated electrons.

1.2.8 Polymers

One important property of carbon is that it forms chains or networks that are linked by carbon–carbon bonds. This linking process is called ‘polymerization’, whereas the chains or networks are called ‘polymers’. The starting source compounds are called ‘monomers’, the basic unit of a plastics being a ‘mer’. There are two main groups of polymers: synthetic and biopolymers. Synthetic polymers are made artificially, and commonly referred to as ‘industrial polymers’, while biopolymers occur within natural environments or with human intervention. Since the invention of the first synthetic polymer product called Bakelite, many others have been invented and continue to be researched and produced to this day. Some common synthetic organic polymers are polyethylene, polystyrene, polypropylene, nylon, poly vinyl chloride, and so on. Synthetic and natural rubbers are also polymers.

Varieties of synthetic polymers are specifically made for different products. Changing the conditions at the time of polymerization, alters the chemical structure of the final polymer and its properties. These changes include chain lengths, branching or tacticity. If the product is from a single polymer, it is called a ‘homopolymer’, and if it is from two different polymers, they are called ‘copolymers’. If three different polymers are combined, then the resulting product is called a ‘terpolymer’. When end products are made with these polymers, physical properties such as hardness, density, mechanical or tensile strength, abrasion, heat resistance, transparency, colour, and so on are achieved with a combination of additives to achieve pre-determined end properties.

1.3 Inorganic chemistry

Inorganic chemistry is the branch of chemistry dealing with the properties and behaviour of non-carbon compounds. The distinction between organic and inorganic chemistry is far from absolute, and there is much overlap, mostly in the sub-disciplines of organometallic chemistry.

Many inorganic compounds are ionic compounds of cations (positively charged ions) and anions (negatively charged ions) joined by ionic bonding. Examples of ionic compounds are salts, such as magnesium chloride, which consists of magnesium cations, and chlorine anions. Another example is sodium oxide, which consists of sodium cations, and oxide anions. In any salt, the proportions of ions are such that the electric charges cancel out, so that the bulk compound is electrically neutral. Ions are described by their oxidation state. Their ease of formation can be inferred by the ionization potential (cations) or from the electron affinity (anions) of the sourcing elements.

Important classes of inorganic salts are oxides, carbonates, sulfates, and halides. Many inorganic salts are characterized by high melting points. Inorganic salts are poor conductors in the solid states. Another important feature is their solubility in water and ease of crystallization. Some salts such as sodium chloride are very soluble in water but some others are not. The simplest inorganic reaction is double displacement in the mixing of two salts, the ions are swapped without a change in oxidation state. The net result is an exchange of electrons. Electron exchange can also occur indirectly, for example, in batteries, which is a key concept in electrochemistry.

Inorganic compounds are found as minerals. Soil may contain iron sulfide as pyrite or calcium sulfate as gypsum. Inorganic compounds are also found ‘multitasking’ as biochemicals such as electrolytes (sodium chloride) in energy storage or in construction (polyphosphate). The first important man-made inorganic compound was ammonium nitrate for soil fertilization. Inorganic compounds are synthesized for use as catalysts, such as vanadium and titanium chloride or as reagents in organic chemistry, such as lithium aluminium hydride. Subdivisions of chemistry are organometallic chemistry, cluster chemistry and bio-inorganic chemistry. These fields are active areas of research in inorganic chemistry aimed at finding new catalysts, superconductors and therapies.

1.3.1 Industrial inorganic chemistry

Inorganic chemistry has traditionally played a major role in the production of industrial chemicals. Some of the most essential inorganic chemicals manufactured in many countries are ammonia, aluminium sulfate, ammonium nitrate, carbon black, chlorine, hydrochloric acid, hydrogen, hydrogen peroxide, nitric acid, nitrogen, oxygen, phosperic acid, sodium carbonate, sodium chlorate, sodium hydroxide, sodium silicate, sodium sulfate, sulphuric acid and titanium dioxide. Manufacture of fertilizers is another major sector of industrial inorganic chemistry.

1.3.2 Organometallic compounds

Organometallic chemistry is the study of chemical compounds containing bonds between carbon and metals. They are considered to be a special category, because organic ligands (ions or neutral molecules) are sensitive to hydrolysis or oxidation. Thus, organometallic chemistry employs more specialized preparative meth...

Table of contents

• Title Page
• Copyright
• Contents
• Preface
• 1 Basic chemistry
• 2 Polymer chemistry
• 3 Polymer material science
• 4 Non-traditional fillers and stiffening agents for polymers
• 5 Processing polymers and composite resins
• 6 Formulating with non-traditional fillers and stiffening agents
• 7 Manufacturing special polymeric products with non-traditional fillers and stiffening agents
• 8 Recommendations for operating efficiency in a manufacturing plant
• Appendix A
• Appendix B
• Appendix C
• Glossary
• Index