Melting temperature depression for low ether content polyether-polyester block copolymers with amide linkages

Melting behavior of a series of polyether-polyester block copolymers with low ether contents was studied. Significant melting-reorganization-remelting was suggested by means of differential scanning calorimetry. The equilibrium melting temperature of the copolymers was obtained by using the Hoffman-Weeks extrapolation. It has been found that the use of the on-set melting temperature for the Hoffman-Weeks plots is less reliable than the use of the corrected peak melting temperature. Copolymerization of polyetheramides with polyesters leads to a significant melting temperature suppression for the polyester crystal. We hypothesize that the locations of the junction points between blocks can be treated as chain ends for the crystallizable polyester blocks: the polyether-polyesters grow to form extended chain-like crystals with lamellar thickness limited by the polyester block length. For comparison, the nonlinear Hoffman-Weeks treatment, recently proposed by Marand, has also been applied to examine the behavior of melting temperature depression. Although the T _m ^o obtained from nonlinear extrapolation is much higher than the T _m ^o obtained from the Hoffman-Weeks extrapolation, similar trend regarding the composition dependence of T _m ^o have been found.     

Melting and Glass Transformation of One‐Component Systems

Melting of solid chemical elements has recently been explained by electronic transitions. Due to such transitions into higher energy levels the wave‐functions and their local charge distributions are changed. Since the occupation of the electronic states and the corresponding charge distribution change at random with time, the core ions are continuously driven to new positions. If the forces are strong enough and the core ions relax to their new positions within the lifetime of the excited states, the changing arrangement of the core ions corresponds to a melt. These considerations are extended from elements to chemical compounds as one‐component systems. The melting entropy and the specific heat capacities near the melting temperature have been normalised to the number of atoms in the formula unit of the one‐component systems. The heat capacities exceed 3R, which is the value expected for vibrations, and accumulate surprisingly at special values as well as the melting entropies. This seems to support the idea of melting as an electronically induced effect. The distributions of the electronic energy levels in the molten state and in the crystalline solid are different. If the forces of the electronic distribution in the relaxed low energy states of the undercooled melt are too weak to attract the core ions to regular lattice positions, the disorder is frozen‐in during cooling and a glass transition takes place. Sufficiently strong directional bonds between neighbouring ions and low melting entropy per particle favour such a transition.     

Melting, Oxidation, Evaporation of Particle in-Flight in Plasma Spray Processes

A comprehensive numerical model has been developed to investigate the transient behaviors of particle characteristics, such as temperature, melting, evaporation, and oxidation status during argon-hydrogen DC plasma spraying.This model includes heat, momen     

Development of smooth finishes in electrostatic fluidized bed (EFB) coating process of high-performance thermoplastic powders (PPA 571 H)

This paper deals with the analysis of the evolution of the surface morphology of metal substrates coated with high-performance thermoplastic powders, namely PPA 571 H, by using electrostatic fluidized bed (EFB) process. Attention has been particularly focused on the relationship between baking time and temperature of EFB coated substrates and the morphological characteristics of the resulting polymeric films.

First, thermal behaviour of PPA 571 H polymeric powders was characterized by using standard calorimetric techniques. Accordingly, PPA 571 H melting kinetic was experimentally deduced. Based upon experimental findings, predictive analytical model was also developed and employed to trace ‘iso-conversion’ curves out.

Second, metal substrates, made from low carbon steel (AISI 1040), were EFB coated and baked at several baking time and temperatures. Combined analyses of scanning electron and confocal microscopes were led to measure the evolution of the films surface morphology under different baking conditions. Accordingly, a relationship between film morphologies and melting degree was sought. Consistent trends of roughness parameters versus baking parameters were found, with smoother finishes of the polymeric films being achieved for higher degrees of melting, that is, for higher baking temperature and time. Full maps and related analytical models of the finishing levels according to baking parameters were also built up, hence providing first useful indications to powder coaters on how to best deal with their settings.     

冲天炉熔制高铬磨球的探讨

介绍了适应冲天炉熔炼高铬磨球的生产工艺、化学成分。在几年生产实践中取得了较好的效果。具有明显的经济效益。     

紫铜熔铸工艺中吸气的思考

简述了氢和氧对铜液的溶解能力；熔铸紫铜时的吸气条件；气孔形成的机理；气孔对铜管质量的影响；以及防止吸气的措施。     

牙轮轴承的渗碳缺陷和失效分析

钎焊在牙轮轴承上的减磨材料Ag 1 5Mn合金 ,在井式炉渗碳时发生了熔化 ,在钻井使用过程中发生块状剥落。经分析 ,防渗碳涂料中的铜元素在高温下挥发沉积在Ag 1 5Mn合金上 ,形成了低熔点的Ag Cu共晶相 ,导致了减磨合金在渗碳过程中的熔化。渗碳又使Ag 1 5Mn合金形成Ag Mn C三元相 ,降低了减磨合金的润滑减磨性以及造成块状剥落。渗碳前取消钎焊工序 ,渗碳后改用镶嵌减磨合金的方法 ,解决了Ag 1 5Mn合金的熔化和块状剥落问题。     

Operation performance of a pilot-scale gasification/melting process for liquid and slurry-type wastes

A gasification/melting facility that can operate up to 10 bar and 1,550 °C with a maximum 1 ton/day capacity was developed for liquid and slurry-type combustible wastes. The main focus of the system development was minimal use of expensive fuel for maintaining the reaction temperature by replacing it with cheap waste oil for energy input. The carbon conversion obtained was 97% while the cold gas efficiency reached 77.6% for the refined waste oil. When the feed was refined oil mixed with fly ash from a municipal waste incinerator, the carbon conversion and cold gas efficiency were 93% and 71.9%, respectively, with a slag conversion ratio of 0.93. The slag produced from fly ash exhibited environmentally acceptable heavy-metal leaching values and thus can be applicable as road material and for other purposes. The optimal O₂/feed ratio was 0.9–1.0 when only the refined waste oil was gasified, whereas the O₂/feed ratio had to be higher than 1.2 when fly ash was mixed. In addition, data showed that gasifier temperature can be estimated by on-line methane concentration measurements.     

(AgCu28)80InxSn(20-x)钎料的熔化特性及其铺展性研究

采用差示扫描量热仪研究了合金的熔化特性。结果表明：该合金在489～496℃处具有554～604℃两个明显的吸热带，添加11wt％的In时，其只存在496℃与603．6℃两个吸热峰。润湿与铺展性能测试表明该合金能很好地润湿紫铜，在In添加量大于12wt％时，随着In含量的增加铺展率变大。     

The crystallization morphology and melting behavior of polymer crystals in nano-sized domains

The crystallization morphology and the melting behavior of the phase-separating poly(?-caprolactone) (PCL) and poly(ethylene oxide) (PEO) blends were studied using atomic force microscopy. Two blends consisting of PCL and PEO with weight ratios of 10/90 and 90/10 were prepared to form the isolated spherical domains by the phase-separating process. The results show that the melting temperatures of the PCL and PEO lamellae in the confined domains increased as the lamellar length increased, and the melting behavior of the PCL and PEO lamellae in the matrix and confined domains was also studied.