Robert R. Matheson

Structure, crystallization and morphology of poly (aryl ether ketone ketone)☆

Abstract The structure, crystallization and morphology of poly (aryl ether ketone ketone)s (PEKKs) prepared from diphenyl ether (DPE), terephthalic acid (T) and isophthalic acid (I) and having different T/I ratios have been investigated. As prepared, these copolymers can be thought of as consisting of ‘phthalate diads’ containing -DPE-T-DPE-T-(TT) and/or -DPE-T-DPE-I-(TI). Melt-crystallized PEKKs (all T/I ratios) form a structure similar to that observed in other poly(aryl ether ketone)s (form 1; a = 0.769 nm, b = 0.606 nm and fibre axis c = 1.016 nm). However, depending on composition, both TT and TI crystals were observed. All PEKK materials grow in the form of spherulites having negative birefringence. The incorporation of isophthaloyl moieties is observed to increase the chain flexibility and decrease the rate of crystallization. The equilibrium melting temperatures of various PEKKs were estimated using the Hoffman-Weeks approach, and showed a linear correlation with the meta isomer content. In contrast to other poly(aryl ether ketone)s, a form 2 crystalline modification ( a = 0.393 nm, b = 0.575 nm and c = 1.016 nm) can be induced either by exposure to solvents or by cold crystallization. The two crystalline modifications differ from each other in the placement of the chains and, consequently, the interchain interactions.

Living polymerization: Rationale for uniform terminology

Polymer chemistry textbooks (e.g., B. Vollmert, Polymer Chemistry, Springer-Verlag: New York, 1973, p 37; G. Odian, Principles of Polymerization, 3rd ed., Wiley: New York, 1991, p 8; H. G. Elias, An Introduction to Polymer Science, VCH: Weinheim, 1997, p 51) classify polymerization reactions as chain, step, and living according to the dependence of their degree of polymerization ( ) or molecular weight ((M) over bar) on conversion. This article discusses the rationale for uniform terminology in living polymerization

A new approach to characterize scratch and mar resistance of automotive coatings

Mar damage is a major customer concern of the automotive coatings industry. Our study of mar performance can be separated into two distinct areas, a detailed understanding of the damage formation mechanism, and an investigation of the relationship between the damage morphology and appearance. We have developed a nanoscratch technique that can measure important physical quantities, such as penetration depth, normal force and tangential force during the formation of the scratch. Mar resistance of three coatings was evaluated and compared based on the damage mechanisms: plastic flow and fracture. The different deformation mechanisms result in different damage morphologies and a corresponding change in visual impact of the scratch. Statistical surveys of appearance of well-defined scratches indicate that in very short observation times, scratches where fracture has occurred are much more visible than those made by plastic deformation alone. However, with sufficient time and strong illumination a significant percentage of observers could see plastic deformation as well.

Oligomers in the evolution of automotive clearcoats: mechanical performance testing as a function of exposure

Automotive coatings must provide excellent resistance to chemical and mechanical damage in order to maintain a vehicles long-term appearance and the owners long-term satisfaction. The Automotive Industry and coating suppliers are partners in design and delivery of future coatings capable of meeting customer demanded performance. As a result of this partnership, new coating materials are being explored based on oligomer chemistry that show promise in providing improvements in both physical and chemical properties/performance and the long-term maintenance of those properties. Oligomeric systems are also useful in design of low VOC coatings. These supersolids coatings will be capable of meeting current and future air quality standards. In this paper measurement techniques for monitoring chemical and mechanical property changes, including cure rate, crosslinking, tensile properties, rheology and scratch and mar performance, were explored. Laboratory mar tests, wet and dry rub tests, which have been validated by commercial experience, are currently used as the basis for comparison of a coatings mechanical performance. QUV accelerated weathering was combined with micro-scratch experiments, atomic force microscopy, optical microscopy, image analysis and IR surface characterization techniques to provide correlations between chemical composition and mechanical performance, and an indication of service life.

A simple thermodynamic analysis of solid-solution formation in binary systems of homologous extended-chain alkanes

Abstract Binary mixtures of n-alkane chains of comparable length are treated within the Bragg-Williams approximation. A simple model is developed to explain which pairs will form a continuous series of solid solutions (close to their respective melting points). Results are fit very well by the empirical rule that c t ⩽ 1.22 c s ensures such a continuous, mutual solubility. Here, c t is the number of carbon atoms in the longer alkane and c s the smaller number. Close analogies are found to the well known Hume-Rothery and Vegards Law generalizations for metallic systems. The issue of crystal similarity as a requirement for solid solubility is successfully treated as a minor, possibly spurious complication.

Quantitative characterization of scratch and mar behavior of polymer coatings

Abstract Scratch and mar damage of automotive topcoats is of increasing concern to the automobile industry and its customers. To better characterize and understand the scratch and mar behavior, we developed a nanoscratch technique to measure important mechanical quantities with high precision. With this technique, mar behavior can be studied in two steps: the damage formation process and the relationship between damage morphology and visual impact. The scratch and mar performance can be evaluated based on plastic and fracture resistance of coatings. In this paper, we will focus on micro-mechanical aspects of scratch deformation. A detailed investigation suggests that the oscillation of measured quantities during scratch damage results from fracture not stick-slip events. For the case discussed here, cracks start in the scratch direction and then gradually propagate 30° away from the direction, which suggests cracks were initiated by tensile stress in front of the indentor.

Simulation of Spray Transfer Processes in Electrostatic Rotary Bell Sprayer

A numerical study of the spray transfer processes in an electrostatic rotary bell applicator (ESRB) has been conducted utilizing code for a newly developed simulation code. This code consists of three modularized solvers: a fluid flow solver, a spray dynamics solver, and an electrostatic solver. The development of the code consisted of the following steps. First, the flow solver designed for an unsteady three-dimensional Navier-Stokes equation was developed to simulate the shaping airflow with the initial condition and the boundary condition supported by experimental data. Second, the particle trajectory solver, which interacts with the airflow by momentum coupling, was developed to apply the spray transport processes. Finally, the electrostatic solver was developed to calculate the electrostatic field within the two phase flow field. The integrated code created by combining those three solvers was then applied to simulate the paint spray transport processes according to the operating conditions of interest

Paint and Coatings Technology: Current Industrial Trends

General trends in industrial coatings research and development are categorized and described. Appearance, workability, durability, environmental footprint, and cost targets are broadly chracterized. The particularly well publicized efforts concerned with nanomaterials and non-petrochemical components are explicitly given context.