Eli M. Pearce

X-ray diffraction

X-rays diffraction (XRD) is a powerful tool in the study of the structure of polymers. The wavelengths of X-rays are often comparable to the interatomic distance in crystals. XRD and scattering experiments involve placing the sample in the path of a monochromatized X-ray beam of low divergence. The scattered X-rays from the regularly placed atoms interfere with each other, giving strong diffraction signals in particular directions. Two primary diffraction methods commonly used to study polymers include wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS). Over the years, WAXS technique is extensively used to study the structural properties of polymers. The value of angles used in WAXS is from 5° to 120°. WAXS is also used to provide information on the number of repeat units per turn in helical structures that are typical of linear polymers, the length of the repeat unit along the fiber axis, and the degree of orientation. The value of angles used in SAXS is from 1° to 5°. SAXS is useful in detecting larger periodicities in a structure.

Suspension polymerization of methyl methacrylate

This chapter illustrates suspension polymerization method by using methyl methacrylate. The apparatus essentially includes: three-necked flask, reflux condenser, sealed stirrer with stainless-steel stirring rod and appropriate stirring motor, thermometer, calibrated addition funnel, water bath, balance, weights, weighing paper, or dishes, graduated cylinder, cheesecloth or nylon chiffon, and laboratory hood. The chapter also describes the reagents, safety precautions, and the procedure as implicated in suspension polymerization technique.

Differential scanning calorimetry

Thermal analysis refers to a group of techniques in which a physical property of a substance and its reaction product is measured as a function of temperature. This chapter provides an overview of differential thermal analysis (DTA), emphasizing on its quantitative development and differential scanning calorimetry (DSC). It is observed that DSC curves reflect changes in the energy of the system, changes that can be either physical or chemical in origin. DSC measures the heat required to maintain the same temperature in the sample versus an appropriate reference material in a furnace. Enthalpy changes due to change of state of the sample are also discussed. In DTA, temperature difference is determined, rather than enthalpy differences between the sample and the reference material, which is done in DSC. DSC is also used to measure a number of important physical changes in a polymer. These include the glass transition temperature (T g ), the crystallization temperature (T c ), the melt temperature (T m ), and the degradation or decomposition temperature (T D ).

Preparation of polystyrene by an emulsion polymerization process

The chapter describes the preparation of polystyrene by emulsion polymerization method. It describes the apparatus, reagents, safety measures, and the procedure. The emulsion polymerization process essentially consists of water, 1–3% of a surfactant, and a water-soluble free-radical generator. The monomer is added gradually or is present from the start. The particles in the emulsion polymerization are essentially of the order of 10 -5 to 10 -7 m in size. It is observed that the locus of polymerization is a micelle and only one free radical can be present at a given time. The monomer is fed into the locus of reaction by diffusion through water, where the reservoir of the monomer is found. If in case another radical enters the micelle, it results in termination because of the small volume of the reaction site. The polymer in emulsion polymerization is isolated by either coagulating or spray drying.

Dynamic mechanical analysis

Polymers vary from liquids and soft rubbers to very hard and rigid solids. Many structural factors determine the nature of the mechanical behavior of such materials. In considering structure-property relationships, polymers can be classified into several regimes. Dynamic mechanical analysis (DMA) or dynamic mechanical thermal analysis (DMTA) provides a method for determining elastic and loss moduli of polymers as a function of temperature, frequency or time, or both. Visco-elasticity describes the time-dependent mechanical properties of polymers, which can behave as either elastic solids or viscous liquids. DMA can be applied to a wide range of materials using the different sample fixture configurations and deformation modes. By comparison to known materials, this procedure can be used to evaluate degree of phase separation in multicomponent systems, amount type, dispersion of filler, degree of polymer crystallinity, effects of certain pretreatment, and stiffness of polymer composites. Dynamic mechanical experiments effectively yield both the elastic modulus of the material and its mechanical damping, or energy dissipation characteristics.

Preparation of polystyrene by a free radical polymerization process

This chapter provides an overview of preparation of polystyrene using a free radical polymerization process. The most common initiators of the polymerization process include acyl peroxides, hydroperoxides, or azo compounds. Free radical polymerization processes are generally carried out in bulk, solution, suspension, emulsion, or by precipitation techniques. It is noted that in all cases the monomer used should be free of solvent and inhibitor or else a long induction period can be generated. Bulk polymerization essentially consists of heating the monomer without solvent with initiator in a vessel. The monomer-initiator mixture polymerizes to a solid shape fixed by the shape of the polymerization vessel. The apparatus for the polymerization process includes balance, heavy-walled polymer tube, stopper for polymer tube, buchner funnel, filtration flask, and filter paper. The polystyrene produced has a broad molecular weight distribution and poor mechanical properties. The residual monomer in the ground polymers can be removed by using efficient devolatilization equipment.

Preparation of poly(1,4-butylene isophthalate)

This chapter illustrates the preparation of poly(l,4-butylene isophthalate). It also describes the apparatus, reagents, safety precautions, and procedures as implicated. The apparatus include a glass ampoule equipped with a septum, with a syringe needle, and another syringe, a heating bath or electric heating mantle, and a balance.

Preparation of poly(hexamethylenesebacamide) (nylon 6–10) by an interfacial polymerization technique

This chapter illustrates interfacial polymerization method to prepare polyamides. It involves the reaction of a diacid dichloride with a diamine between two immiscible liquids as the reaction zone, with or without stirring. The method is generally useful where the reactants are sensitive to high temperature and where the polymer degrades before the melt point is reached. Some important variables involved in interfacial polymerization include the organic solvent, reactant concentration, and use added detergents. The chapter also describes the apparatus, reagents, safety precautions, and procedure as implicated by the polymerization method.

Redox emulsion polymerization of ethyl acrylate

This chapter describes the redox emulsion polymerization technique by using ethyl acrylate. The chapter specifically describes the apparatus, safety measures, reagents and materials, and the procedure followed. The reagents and materials include deionized water, sodium lauryl sulfate, nitrogen, ethyl acrylate, a solution freshly prepared from ferrous sulfate heptahydrate dissolved in deionized water, sodium persulfate, sodium metabisulfite, few drops of 70% commercial tert-butyl hydroperoxide, ice, and a few crystals of hydroquinone.

Preparation of a cured epoxy resin by the room temperature reaction of bisphenol a diglycidyl ether with polyamines

This chapter describes the preparation of a cured epoxy resin with the help of room temperature reaction of bisphenol A diglycidyl ether with polyamines. The chapter describes the apparatus, reagents, safety precautions, and procedures as implicated. The apparatus include aluminum weighing dishes, test tubes, salt plates for infrared (IR) spectrophotometer, nuclear magnetic resonance (NMR) tubes, deuterated dimethyl sulfoxide for NMR, IR spectrophotometer, NMR, balance, and spatula.