Molecular weight distribution, morpholog

Mechanical properties of a polymer depend on many variables— molecular weight, molecular weight distribution, morphology, additives, temperature, time, and so on. Mechanical properties of polymers are... 

Polypropylene is not one or even 100 products. Rather it is a multidimensional range of products with properties and characteristics interdependent on the type of polymer (homopolymers, random, or block copolymer), molecular weight and molecular weight distribution, morphology and crystalline structure, additives, fillers and reinforcing fillers, and fabrication techniques. 

There are many different approaches to setting up QC. For example, mechanical properties can be considered the most important of all properties, and there are many factors that determine the mechanical behavior of plastics. As reviewed throughout this book, the factors that influence properties include the resin composition (fillers, molecular weight distribution, morphology, etc.), the processing method and machine controls, the capability of auxiliary equipment, and part performance requirements. 

Their properties depend on a great number of parameters, such as molecular structure, tacticity, composition of copolymers and modified polyolefins, molecular weight and molecular weight distribution, morphology, environment, and so on. 

Advanced computational models are also developed to understand the formation of polymer microstructure and polymer morphology. Nonuniform compositional distribution in olefin copolymers can affect the chain solubility of highly crystalline polymers. When such compositional nonuniformity is present, hydrodynamic volume distribution measured by size exclusion chromatography does not match the exact copolymer molecular weight distribution. Therefore, it is necessary to calculate the hydrodynamic volume distribution from a copolymer kinetic model and to relate it to the copolymer molecular weight distribution. The finite molecular weight moment techniques that were developed for free radical homo- and co-polymerization processes can be used for such calculations [1,14,15]. 

Diblock copolymers PEO-fo-PS have been prepared using PEO macroinitiator and ATRP techniques [125]. The macroinitiator was synthesized by the reaction of monohydroxy-functionalized PEO with 2-chloro-2-phenylacetyl-chloride. MALDI-TOF revealed the successful synthesis of the macroinitiators. The ATRP of styrene was conducted in bulk at 130 °C with CuCl as the catalyst and 2,2 bipyridine, bipy, as the ligand. Yields higher than 80% and rather narrow molecular weight distributions (Mw/Mn < 1.3) were obtained. The surface morphology of these samples was investigated by atomic force microscopy, AFM. 

Even though the first report about the synthesis of crystallizable ABC triblock copolymers was published in 1978 for PS-fo-PB-fo-PCL copolymers [114], in that work only a preliminary study of the tensile properties was performed, without considering the crystallizability of the materials. It was only 20 years later, when the preparation of these materials was reconsidered and optimized, that triblock copolymers with relatively narrow molecular weight distributions were obtained [115], a requisite which is indispensable for the generation of well-defined morphologies. To illustrate the complexity and richness of semicrystalline ABC triblock copolymers, PS-fc-PB-fc-PCL triblock copolymers have been chosen. These copolymers have been prepared with a wide composition range (with PCL contents from 11 to 77%) and they have been compared with PS-fc-PCL and PB-fo-PCL diblock copolymers [29,98, 115-118]. 

The balance of both terms affects the morphology and molecular weight distribution of the particles. If there is no unpredictable aggregation the particles grow together and the particle size distribution narrows down. 

The formation of carbon-carbon cross-links is by far the most important effect and is the basis of the applications in wire and cable industry and for heat-shrinkable products. The factors affecting the changes of polyethylene by irradiation are the molecular weight distribution, branching, degree of unsaturation, and morphology. °... 

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