Polymerisation Tensile strength

Polymerisation of a diol with a dicarboxybe acid is exemplified by the production of a polyester from ethylene glycol and terephthabc acid either by direct esterification or by a catalysed ester-interchange reaction. The resulting polyester (Terylene) is used for the manufacture of fibres and fabrics, and has high tensile strength and resibency its structure is probably ... 

The parameter most commonly monitored in this research is the extent of hydrogen peroxide decomposition. Measurement of tensile strength and/or the degree of polymerisation can be useful indicators of fibre damage. The effect of iron(III) ion concentration in accelerating the rate of peroxide decomposition is shown in Figure 10.23,... 

Kevlar has the highest tensile strength and is often used as a reinforcing fibre in composites with, e.g., epoxy, PEEK. The thermotropic liquid crystal polymer Vectran is made by melt polymerisation of p-acetoxybenzoic acid and 6-acetoxy-2-naphthoic acid, (the corresponding hydroxy acids decompose on melting). Because of its liquid crystal properties the polymer can be spun into fibres from the melt. Kevlar is spun from a solution in concentrated sulfuric acid, and can be melt drawn to give a high modulus (stiff) polymer. Vectran ... 

Polystyrene is brittle. Rubber (5-15%) is added to improve this property. This is known as impact polystyrene. It is obtained by polymerising styrene in the presence a rubber. This impact polystyrene is having reduced clarity, softening point and tensile strength but better impact strength. 

The PP is produced by melt-kneading PP, an isoprene monomer and a radical polymerisation initiator, which has a high melt viscosity and a high melt tensile strength and is difficult to cause drawdown. Foamed articles made therefrom have a low density, high closed cell content, good appearance and excellent heat resistance. 

Another striking example concerns the polymer poly(p-xylylene) (PPX). It is obtained by condensation at room temperature of the gaseous monomer. A clear foil may be obtained in that way. The melting point of PPX is 427 °C and it crystallises immediately after polymerisation, so that entanglement cannot be formed. Van der Werff and Pennings (1988, 1991) have shown that hot drawing of such a material at 420 °C yields a material with a tensile strength of 3 GPa and a tensile modulus of 100 GPa. 

Corn oil-based polymer resin, prepared by the cationic polymerisation of conjugated corn oil, styrene and divinylbenzene, using boron trifluoride diethyl etherate modifled by Norway fish oil as the initiator with 4-vinylbenzyl triethylammonium cation modified montmorillonite clay (VMMT) nanocomposites were reported. The resultant nanocomposites with 2-3 wt% VMMT exhibited significant around two-fold improvements in tensile modulus, tensile strength and toughness when compared to the pristine polymer. There is an improvement in thermal stability up to 400°C in the nanocomposites. ... 

Flame-retardant polymers can be obtained by co-polymerisation of phosphazenes with styrene or urethane [11,95,96]. Phenyl-phosphor resins, made by incorporating (PNCl2) into phenol plastics, have high tensile strength and can be used up to 260°C. 

PHA polymers are thermoplastics that are soluble in halogenated solvents such as chloroform and dichloromethane. Depending on their chemical composition (homo- or copolymer, the hydroxy fatty acids contained), they differ in their physical properties, eg, ductility and elasticity. PHA can be processed on conventional processing equipment. The processability as well as some mechanical properties like impact strength and flexibility can improve when a monomer/comonomer with longer aliphatic chain is used in polymerisation. One of the commercially available types of PHA is polyhy-droxybutyrate (PHB). PHB is similar to polypropylene in some characteristics like melting temperature, tensile strength, moismre resistance, and odour barrier properties (Pouton and Akhtar, 1996). 

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