Droplet–surface impact at high pressures

The present work is a study of droplet–surface collisions at high pressures.A technique adapted from Lagrangian particle tracking is presented. The tracking technique is a hybrid between traditional high-speed, high-resolution photography used for drop studies and particle tracking velocimetry. It is suitable for high pressure systems with very short relaxation distances and with a non-steady background fluid.Collisions of droplets towards dry and wet walls were studied for systems of liquid decane with CO₂ or N₂ as gas phase, and a single component, two phase pure CO₂ system at saturation. At low impact velocities, higher deposition efficiencies were observed for collisions against the dry wall compared to the wet wall. The events are described in terms of micro-scale mechanisms. Additionally, deposition efficiency maps are given, and it is shown how to use these in two different modelling frameworks.     

Blends containing core–shell impact modifiers. Part 5 – Ductile–brittle transition temperatures in impact and slow bending

Abstract

Dart drop, Charpy impact and single edge notched bending fracture tests were conducted over a range of temperatures on blends of polycarbonate (PC), poly(methyl methacrylate) (PMMA), poly(styrene-co-acrylonitrile) (PSAN), and poly(vinyl chloride) (PVC) with two core–shell impact modifiers, which were based, respectively, on polybutadiene and poly(butyl acrylate-co-styrene). The T _g values of the two rubbers were ?75 and ?8°C, respectively. The transition from fully brittle to partially or fully ductile behaviour occurred at various temperatures T _BD depending upon a number of factors, which included the T _g of the rubber phase, the choice of thermoplastic matrix, and the type of test. In disc specimens subjected to dart drop impact, ductility was observed at lower temperatures than in sharply-notched specimens tested in slow three-point bending. It is concluded that the T _g of the rubber phase generally marks a lower limit for ductility in rubbertoughened blends, but that other factors can shift the brittle–ductile transition to higher temperatures.     

Do ruminant trans fatty acids impact coronary heart disease risk?

Unlike TFAs produced industrially in partially hydrogenated vegetable oils (primarily elaidic acid, 18:1, trans‐9), evidence suggests that trans fatty acids from ruminant food sources (e. g. 18:1, trans‐11; i. e. trans‐vaccenic acid and 18:2, cis‐9, trans‐11; i. e. rumenic acid) do not increase the risk of coronary heart disease. The amount of trans fatty acids in ruminant milk fat varies from 1% to 6% by weight depending on the composition of the ruminants diet. In the U.S., milk fat trans fat levels averages 3.56 wt% (range of 3.20–4.47 wt%). In general, ruminant trans fat accounts for about 20% of the total trans fatty acids intake in the U.S. and consists of approximately 86% from milk fat and 12% from ruminant meat sources.     

The impact of synthetic biology in chemical engineering—Educational issues

This paper describes the development of synthetic biology as a distinct entity from current industrial biotechnology and the implications for a future based on its concepts. The role of the engineering design cycle, in synthetic biology is established and the difficulties in making and exact analogy between the two emphasised. It is suggested that process engineers can offer experience in the application of synthetic biology to the manufacture of products which should influence the approach of the synthetic biologist. The style of teaching for synthetic biology appears to offer a new approach at undergraduate level and the challenges to the education of process engineers in this technology are raised. Possible routes to the development of synthetic biology teaching are suggested.     

Exploring temperature dependence of the toughening behavior of β-nucleated impact polypropylene copolymer

In this study, the effects of α- and β-nucleating agents (α-NA and β-NA) on the toughening behavior of impact polypropylene copolymer were ascertained with respect to three test temperatures (23, 0 and ?15 °C). The addition of α-NA impacted the toughness slightly for all test temperatures. However, the tendency of impact strength vs. β-NA content at 0 °C significantly differs from that of the other two temperatures. Importantly, a close correlation between toughness at 0 °C and chain mobility of the amorphous portion has been well revealed for the first time by achieving a linearly fitting between impact strength at 0 °C and β-relaxation peak intensity in DMA spectrum. A comparative investigation between the situations containing α-NA or β-NA offers new insights into the physical origin of the toughening behavior for a multiphase multicomponent polyolefin system. The chain mobility of matrix amorphous portion plays a dominant role on toughening.     

Vinylidene fluoride- and trifluoroethylene-containing fluorinated electroactive copolymers. How does chemistry impact properties?

Fluoropolymers are attractive niche polymers used in high added value materials for high-tech applications in aerospace, electronics, coatings, membranes, cables, and the automotive industries. Among them, VDF- and TrFE-based copolymers exhibit remarkable electroactive properties allowing their incorporation into a wide range of devices such as printed memories, sensors, actuators, artificial muscles, and energy storage devices. In a first section, a detailed overview of semi-crystalline poly(VDF-co-TrFE) copolymers and of their ferroelectric (FE) properties from the point of view of polymer chemists is supplied. In addition to the polymer microstructure that may sometimes be controlled or influenced by the synthesis strategies, physical properties such as the phase transitions, and electroactivity are also affected by processing, such as annealing for example, and film thickness for example. Building on the conclusions and understanding obtained from the first section, the effect of the introduction of a termonomer (leading to poly(VDF-ter-TrFE-ter-M) terpolymers) is detailed in a second section of this review. Modifying the terpolymer chain microstructure has a major impact on the crystalline phase of the terpolymers that may result in a relaxor-ferroelectric behavior (RFE). The distribution of the termonomer along the polymer chain, the capacity of the termonomer units to enter the crystal lattice, as well as its dipole moment govern in large part the terpolymer electroactive properties. Poly(VDF-ter-TrFE-ter-CFE) and poly(VDF-ter-TrFE-ter-CTFE) terpolymers appeared to be the best candidates for RFE properties and were thus the most studied. In two following sections, the block or graft architectures of VDF- and TrFE- based copolymers, and the various crosslinking strategies used so far for such copolymers are described. Chemical modification is indeed a very powerful tool to tune electroactive properties of copolymers or to impart additional properties. Finally, in the last section, a few examples of emerging applications for these fluorinated electroactive polymers (EAPs) are briefly discussed. This review aims to provide a comprehensive report on the use of polymer chemistry as a tool to produce better electroactive fluorinated polymers, and highlights possible opportunities and perspectives for future progress in this field. Research in this interdisciplinary field requires different kinds of expertise, ranging from organic and polymer chemistries, polymer films engineering, physics of semi-crystalline polymers and electroactivity, to the design and fabrication of electronic devices.     

Assessing the impact of augmented reality application on students’ learning motivation in chemical engineering

Application of augmented reality (AR) in education has recently grown in interest due to distant, online, and self-directed learning. In this study, the impact of implementing an AR application on chemical engineering students’ learning motivation and performance was assessed. Two interactive AR lessons on common industrial equipment (i.e., centrifugal pump and shell-and-tube heat exchanger) were developed on the EON-XR platform. A cohort of 50 undergraduate chemical engineering students participated in the AR lessons and evaluated its impact on students’ learning motivation and usefulness as a learning resource. The level of students’ learning motivation was assessed with a 16-item questionnaire based on the Instructional Materials Motivation Survey (IMMS) from Keller’s ARCS model, and qualitative questions related to the future of AR technology in chemical engineering education. Results show that 82% of respondents found AR lessons helpful compared to conventional lesson delivery modes, while 92% were supportive for AR lessons to be an additional resource to existing learning materials. These findings demonstrated that AR technology impacted students’ learning motivation positively across multiple constructs, namely ‘Attention’, ‘Relevance’, ‘Confidence’ and ‘Satisfaction’ and showed great potential as an innovative pedagogical advancement in chemical engineering education.     

The influence of nitric acid oxidation of low rank coal and its impact on coal structure☆

FT-i.r. was used to examine the behaviour of a Spanish lignite during its oxidative treatment with nitric acid with a view to assessing the different forms of sulphur reduction and the changes produced in the coal structure, as a result of the action of the reagent. Inorganic sulphur decreases rapidly and practically disappears, even under mild attack conditions (50 °C, 20% acid concentration). At first, organic sulphur undergoes a rapid decrease but more energetic conditions are required to maintain the reduction. Reduction may even reach 53% under such conditions.Unfortunately, energetic attacks (90 °C) lead to a high-level of coal organic matter solubilization and an increase in oxygen content. Basically, the oxygen appears as carbonyl group within the desulphurized coal.The nitric acid causes effective nitration of the coal, the nitrogen being incorporated especially as aromatic nitrogen. The substitution is easily produced (50 °C) when there are two adjacent aromatic hydrogens per ring. The isolated hydrogens in aryl- or polycyclic aromatic structures, are more resistant to attack under mild conditions but not so at 90 °C. As nitration progresses, more electrophilic molecules appear and aliphatic hydrogen tends to increase after initially decreasing under mild attack and increases more so under more energetic condition. This aliphatic hydrogen compensates for the decrease in aromatic hydrogen.     

The impact of bonite aggregate on the properties of lightweight cement-bonded bonite–alumina–spinel refractory castables

The lightweight bonite–alumina–spinel (CA₆–Al₂O₃–MA) refractory castables with bonite aggregate and different spinel sources (pre-formed and in situ formation) were prepared in this study. The phase composition, microstructural features, and mechanical and thermo-mechanical properties of CA₆–Al₂O₃–MA castables treated at various temperatures were investigated by techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending method, and thermal shock test. The results indicated that the incorporation of bonite aggregate had a positive influence on the strength, thermal shock resistance and slag corrosion resistance. It especially decreased the thermal conductivity and had a slightly negative influence on the refractory under load and slag penetration resistance of the castables. For the in situ spinel-containing castable, the formation of in situ spinel with finer particle sizes and acicular CA₆ grains led to higher overall volume expansion, resulting in higher thermal expansion (∆L/L₀), linear change and the apparent porosity of castables. Also, the heat insulation, thermal shock and slag penetration resistance of castables with in situ spinel improved, while the strength, displacement, refractory under load and slag corrosion resistance decreased sharply.     

Preparation of core–shell impact modifier particles for PVC with nanometric shell thickness through seeded emulsion polymerization

The improvement in toughness of rigid polymers like poly(vinyl chloride) (PVC) has been of great interest for developing their applications. This could be provided by designing impact modifiers which could be blended with the polymeric matrix. Here, core–shell type impact modifier particles with different glass transition temperatures of the shell and specifically, with nanometric shell thickness were prepared through seeded emulsion polymerization. The core consisted of polybutadiene particles and the shell was made of poly(methylmethacrylate-co-butyl acrylate) that was grafted onto the surface of the seed particles. The polymerization reaction was optimized and the resulting latex particles were well characterized by several techniques such as DSC, DLS, SEM, and TEM. It was found that the core–shell particles have diameters of about 350–360 nm, including the shell with thickness of almost 20–30 nm and glass transition temperatures ranging between 70 and 120 °C. The prepared particles were blended with PVC and the corresponding impact strengths of the moldings were measured by means of Izod impact test. The impact results revealed that by decreasing T _g of the shell in impact modifier particles, the impact resistance of the molded sheets increased remarkably. Also the brittle–ductile transition temperatures (BDTT) of the prepared blends were studied and an increase in BDTT was found with lowering T _g of the shell.     

Investigating the impact of Cloisite® 15A nanoclays on the diffusivity of Irganox 1035 antioxidant in high-density polyethylene nanocomposite

Knowing the diffusion coefficients of antioxidants in packaging materials is essential to assess their effectiveness in protecting materials against oxidation, but also to prevent their eventual migration to food. In this work, the diffusion of a commercial phenolic antioxidant (Irganox 1035) was measured experimentally in pristine high-density polyethylene (HDPE) and in HDPE nanocomposite filled with 3 wt% of nanoclays (Cloisite® 15A). Diffusion experiments were performed using the Roe's method between 60 and 100°C. The local concentration of Irganox1035 in each film was measured by UV–Vis spectroscopy from the UV absorbance at 282 nm. The adjustment of the experimental data by Fick's second law allowed us to deduce the values of the diffusion coefficient of Irganox1035 at each temperature and to show that the temperature dependence of this coefficient obeys an Arrhenius' law. It is shown that the incorporation of 3 wt% of Cloisite®15A into HDPE significantly hinders the diffusion of Irganox 1035 and increases its activation energy. Several mechanistic assumptions could explain this result, first the increase in the tortuosity of diffusion paths, but also the possible establishment of strong intermolecular interactions between the antioxidant and some chemical groups on the nanofiller surface, or even the formation of an interphase with reduced molecular mobility around the nanofillers.     

Effects of the molecular weight and CC functionality of poly 1-hexene on the properties of poly 1-hexene-based high impact polystyrene

Here we are aimed to unravel the effects of CC functionality and molecular weight of the rubber on the final properties of poly1-hexene-based high impact polystyrenes (HIPS). In this regard, various HIPS samples were synthesized by free radical polymerization of styrene in the presence of different weight fractions of various poly1-hexene-based impact modifiers including: (i) high molecular weight poly1-hexene (PHex), (ii) low molecular weight poly1-hexene (Olig), and (iii) 1-hexene/1,5-hexadiene copolymer (Copolym). Results showed that by increasing CC functionality from PHex to Oligm and Copoly, the degree of grafting increases which has its influence on the mechanical, thermal and morphological perspectives of the synthesized HIPSs. Besides CC unsaturation degree, the effect of rubber molecular weight on the final HIPS properties was studied as well. According to the results, molecular weight has significant effect on the final HIPS performance, too. Finally, our obtained results suggest new HIPS/Copolym sample as the one with the highest mechanical and thermal properties which is comparable well with commercial HIPS/polybutadiene grades. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47169.     

Interfacial interactions in calcium carbonate–polypropylene composites. 2: Effect of compounding on the dispersion and the impact properties of surface-modified composites

This study was carried out to investigate the influences of compounding process and surface treatment on calcium carbonate (CaCO₃) filled polypropylene. The compounding process is discussed with reference to a twin-screw extruder and an internal mixer. The calcium carbonate filler was surface-treated with a liquid titanate coupling agent (LICA 12) and stearic acid. Composites of different weight fractions were prepared by both compounding processes, and their impact properties were evaluated. The notched Izod impact strength increased with CaCO₃ content up to a maximum at about 10 vol%, and then decreased. Surface treatment of CaCO₃ filler generally yielded composites of higher impact strength than untreated system. Though LICA 12 was more effective than stearic acid in modifying the filler, the low-cost stearic acid proved to be more effective when dealing with the impact properties of composites. Moreover, the composites from a Brabender Plasti-corder exhibited better gross uniformity than that from the twin-screw extruder. However, good filler dispersion and uniform microscopic morphology, as revealed by SEM microscopy, was observed in the samples from the twin-screw extruder. Polym. Compos. 25:451–460, 2004. © 2004 Society of Plastics Engineers.     

Nano-Calcium carbonate (CaCO3)/Polystyrene (PS) core-shell nanoparticle: It’s effect on physical and mechanical properties of high impact polystyrene (HIPS)

Rheological, thermal, mechanical and morphological properties of core-shell [Calcium carbonate (CaCO₃)/Polystyrene (PS)]/High impact polystyrene (HIPS) as well as bare nano-CaCO₃/HIPS nanocomposites with different wt% loading were investigated in this paper. All composites were prepared individually by incorporating nano-CaCO₃/PS hybrid nanoparticles and bare nano-CaCO₃ with 0.10–5.0 wt% loading on Brabender Plastograph. It was shown from the experimental results that rheological, thermal, mechanical and morphological properties were improved as hybrid nano-CaCO₃/PS particles reinforced in HIPS matrix. The interaction between nano-CaCO₃ particles and HIPS matrix was significantly improved when the nano-CaCO₃ nanoparticles were grafted with PS. FESEM (field emission scanning electron microscope) and AFM (atomic force microscope) images showed a perfect dispersion of nano-CaCO₃ particles in polypropylene (PP) matrix.     

Toughening of poly(l-lactide) with poly(ε-caprolactone): Combined effects of matrix crystallization and impact modifier particle size

Enhancing matrix crystallization has been demonstrated to be an effective method to simultaneously improve the impact toughness and heat resistance of poly(l-lactide) (PLLA) modified with flexible polymers, such as poly(ε-caprolactone) (PCL). Unfortunately, increasing PLLA matrix crystallinity alone cannot guarantee the enhancement of impact toughness in most cases, so other structural parameters should be considered. In this work, taking PLLA/PCL (80/20) blend as an example, the combined roles of matrix crystallization and impact modifier particle size in the toughening have been investigated. PLLA matrix crystallinity was controlled by adding a highly effective nucleating agent and PCL particle size was tailored by varying processing conditions while maintaining constant interfacial adhesion. It is interesting to find that toughening is efficient only if matrix crystallinity and particle size are well matched. With the significant increase of matrix crystallinity, an evident decrease of optimum particle size for toughening PLLA has been identified for the first time. Therefore, suitable particle size is the precondition for highly crystalline matrix to work effectively in the toughening because only small particles (0.3–0.5 μm) are effective in trigger shear yielding mechanism of the matrix needed for good toughness, whereas relatively large particles (0.7–1.1 μm) are only capable of toughening amorphous matrix effectively by initiating multiple crazing of the matrix. Importantly, our findings can be used to well explain the reason for the different roles of matrix crystallization in the toughening of different PLLA blends reported in the literature. Furthermore, the heat resistance of the blend with a highly crystalline matrix is much better than that of the blend with an amorphous one as expected. This work could not only provide a new insight into the synergistic roles of matrix crystallization and modifier particle size in the toughening of PLLA but also set up a universal framework for designing high-performance PLLA products with both good impact toughness and high heat resistance.