Toughened polystyrene composites by the concentrated emulsion pathway

Rubber–styrene solutions of various compositions and containing a suitable initiator have been polymerized starting from concentrated emulsions in which the above solutions constitute the dispersed phase and solutions of sodium dodecylsulfate in water the continuous phase. Latexes of rubber-modified polystyrene composites have been thus obtained. Solutions of rubber–styrene have been also polymerized by bulk polymerization for comparison purposes. The molecular weights have been determined from intrinsic viscosity measurements, and the mechanical properties of the composites have been studied via tensile testings. Because of the lower mobility of the high-molecular radicals in the concentrated emulsions, higher molecular weights have been obtained by the concentrated emulsion polymerization than by the bulk polymerization method. The tensile properties and toughness of the composites have been determined. While the two polymerization methods provide high, comparable toughness, the concentrated emulsion method generates latexes that can be easily processed in any desirable shape. © 1994 John Wiley & Sons, Inc.     

Semiinterpenetrating polymer network latexes via concentrated emulsion polymerization

Latexes of semiinterpenetrating polymer networks (SIPN) of polyurethane (PU) and poly(methyl methacrylate) (PMMA) were prepared via the concentrated emulsion polymerization. In this procedure, a partially cross-linked PU was first prepared in a low polarity solvent from the appropriate precursors. Subsequently, MMA and an initiator were introduced into the solution, and the solution was used as the dispersed phase of a concentrated emulsion in water. Finally, SIPN latexes were obtained via the polymerization of the concentrated emulsion. For comparison purposes, SIPN materials have been also prepared via bulk polymerization. The studies with differential scanning calorimetry and transmission electronic microscopy showed that partial interpenetration was achieved in the SIPN latexes. The tensile behavior and particle morphology of the SIPN materials were investigated by changing the proportion of PU, the molar ratio of NCO/OH, the theoretical cross-link density, and the concentration of the initiator. The SIPN latexes prepared possess a high toughness. © 1995 John Wiley & Sons, Inc.     

超浓聚合物乳液及其研究进展

与传统聚合物乳液相比,超浓聚合物乳液不仅聚合物含量高,而且有许多特殊的性能和应用,是聚合物乳液领域的一个重要分支.本文简要概述了超浓聚合物乳液及其制备方法,综述了当前的研究进展和面临的挑战,并对超浓聚合物乳液的前景进行了展望.     

用浓乳液法制备PS/PBMA/PEGD自相容高分子合金

用浓乳液聚合方法，将可聚合大分子单体与其他单体通过原位共聚合生成增容剂，制备了PS/PBMA/PEGO自相容高分子合金。结果表明，凝胶质量分数低于43.4%的高分子合金具有较好的加工性能。     

Tough reinforced open porous polymer foams via concentrated emulsion templating

Low-density but very resilient and robust polymer foams possessing an interconnected open porous network have been synthesised by the polymerisation of the continuous phase of concentrated or high internal phase emulsions containing polyethylene glycol dimethacrylate (PEGDMA) as main crosslinker. The synthesised polymer foams did not display the undesirable properties, such as brittleness and chalkiness, which are commonly observed for highly crosslinked porous polymer monoliths synthesised by the polymerisation of high internal phase emulsions. An effective way to improve the mechanical performance of open porous polymer foams is to raise the apparent foam density. Therefore, the continuous phase of the emulsions was increased up to 40 vol.%. The mechanical properties can be further increased by the incorporation of silica particles into the polymer. Methacryloxypropyltrimethoxysilane was added to the continuous phase to ensure that the silica particles were covalently bonded into the inorganic polymer network formed by the hydrolytic condensation of the silane groups. The addition of reinforcement increased the mechanical properties. The Young's modulus and the crush strength of the polymer foams increased by up to 360% and by up to 300%, respectively, in comparison to non-reinforced samples.     

Ultrasound assisted in situ emulsion polymerization for polymer nanocomposite: A review

This review covers an ultrasound assisted synthesis of polymer nanocomposites using in situ emulsion polymerization. First of all, surface modification of core nanoparticles with a coupling agent and surfactant has been employed for the synthesis of core–shell polymer nanocomposites. In addition to application of ultrasound for the synthesis of core–shell polymer nanocomposites, due to its influential efficiency, sonochemistry has been extensively used not only as an aid of dispersion for inorganic nanoparticles and organo-clay, but also acts as an initiator to enhance polymerization rate for synthesis of polymer nanocomposites. In situ emulsion polymerization of hydrophobic monomers, such as methyl methacrylate, butyl acrylate, aniline, vinyl monomers and styrene, using surfactant and water soluble initiator were carried out for a synthesis of core–shell polymer nanocomposite. This technique assists in preparation of stable and finely dispersed polymer nanocomposite with the loading of inorganic particles up to 5 wt.%. Recent developments in the preparation of core–shell polymer nanocomposites using an ultrasound assisted method with their physical characteristics such as morphology, thermal, and rheological properties and their potential engineering applications have been discussed in this review.     

A new concentrated emulsion polymerization pathway

To ensure the stability of the concentrated emulsions that are employed as precursors for polymerization, a two-step concentrated emulsion polymerization pathway is described. In the first step, the monomer is partially polymerized by heating at 50°C until a certain conversion is reached. Subsequently, the partially polymerized monomer is used as the dispersed phase to prepare a concentrated emulsion in which water constitutes the continuous phase. The concentrated emulsion has a large volume fraction of the dispersed phase (0.74–0.99) and the appearance of a gel. Several typical monomers are employed to correlate the stability of the concentrated emulsion and the extent of partial polymerization of the dispersed phase. It was found that monomers, which cannot lead to stable concentrated emulsions, can generate them after partial polymerization. Subsequent polymerization of the concentrated emulsion leads to latex particles. Copolymers and polymer composites were also prepared by the two-step procedure. In the latter case, water was replaced with a solution of a hydrophilic monomer in water as the continuous phase. © 1992 John Wiley & Sons, Inc.     

A novel approach in preparing polymer/nano-CaCO composites

An novel compounding process using nano-CaCO₃ aqueous suspension for preparing polymer/nano-CaCO₃ composites with nanoparticles dispersed at the nanoscale is reported. The process is called the mild mixing method. In this method, the pre-dispersed nanoparticle suspensions are blended with melting polymers in a weak shearing field using an extruder, followed by removing the water from the vent. The four typical polymeric nanocomposites were prepared by mild mixing method. The dispersion of nano-CaCO₃ in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy (SEM). The molecular weights of polycarbonate (PC) and its nanocomposite showed that the degradation had not occurred during the mild mixing processing. The mechanical properties of the composite with 1.5 wt-% nano-CaCO₃ improve slightly. It proved that this approach is suitable for the preparation of nanocomposites based on both polar and non-polar polymers.     

Nanocellulose-based polymer composites for energy applications—A review

With rapid fossil fuel consumption and ecological concerns, alternative options of green energy development and its efficient storage technology is an emergent area of research. Nanocellulose is observed to be a very-promising sustainable and environmentally friendly nanomaterial for green and renewable electronics for advanced electrochemical energy conversion/conservation devices. This review begins with a basic introduction on the sources and properties of nanocellulose. It provides an overview of the recent advancements made by researchers in integrating nanocellulose with active materials to form a flexible film/aerogel/3D structures as a substrate for powering portable electronics, electric vehicles, etc. The review highlights the use of nanocellulose-based composites in energy conversion devices such as solar cells, piezoelectric materials, and lithium ion batteries. Recent research shows that the power conversion efficiency of solar cells and the piezoelectric performance of piezoelectric materials can be increased when the matrix is reinforced with nanocellulose. The review also focuses on the updates of nanocellulose-based composites in separators, binders, and electrodes of energy conservation devices such as supercapacitors, and energy capture devices such as CO₂ separators. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48959.     

A novel approach in preparing polymer/nano-CaCO3 composites

An novel compounding process using nano-CaCO₃ aqueous suspension for preparing polymer/nano-CaCO₃ composites with nanoparticles dispersed at the nanoscale is reported. The process is called the mild mixing method. In this method, the pre-dispersed nano-particle suspensions are blended with melting polymers in a weak shearing field using an extruder, followed by removing the water from the vent. The four typical polymeric nanocomposites were prepared by mild mixing method. The dispersion of nano-CaCO₃ in the matrix of the polymer at the nanoscale was confirmed by scanning electron microscopy (SEM). The molecular weights of polycarbonate (PC) and its nanocomposite showed that the degradation had not occurred during the mild mixing processing. The mechanical properties of the composite with 1.5 wt-% nano-CaCO₃ improve slightly. It proved that this approach is suitable for the preparation of nano-composites based on both polar and non-polar polymers. __________ Translated from Acta Polymerica Sinica, 2007, (1): 53–58 [译自: 高分子学报]     

A new approach to continuous emulsion polymerization

The application of a continuous Couette-Taylor vortex reactor to continuous emulsion polymerization was studied. First, the mixing characteristics of the reactor were examined by the stimulus-response method. It was found that the reactor performance was similar to that of a continuous flow reactor consisting of more than 60 well-stirred tanks in series if the reactor was properly designed and operated near the critical Taylor number. It was also demonstrated by a comparison of the particle size distributions of the latexes produced in a batch reactor and in the continuous Couette-Taylor vortex reactor that the continuous reactor could produce latex particles with fairly narrow size distribution. Furthermore, since no stirrer is involved, this continuous reactor is suited for the purpose of avoiding coagulation of latex particles that are very sensitive to mechanical shear.     

Modification of thermosetting resins and composites through preformed polymer particles: A review

A review is presented that focuses on preformed particle modification of high performance thermosetting resins and composite systems. The modifiers reviewed consist of thermoplastic and rubber preformed particles with no size limitations. Both organic and inorganic preformed polymer particles are considered but not glass or hollow spheres. In this text, preformed particles are defined as those which do not require phase separation and remain in the shape in which they were added to the neat resin or composite. Therefore, these particles may be developed prior to the resin formulation and then added to the thermosetting resin or developed in situ (during resin formulation) before the resin is catalyzed or cured. This technical review of preformed particle modification of thermosetting resins and composite systems summarizes the utilization of these materials and their performance.     

Temperature effects on structural integrity of fiber-reinforced polymer matrix composites: A review

Fiber-reinforced polymer matrix composites (FRPMCs) are the most promising and valuable material developed in the last few decades. In response to the increased research and publications concerning the thermal stability of FRPMCs, this review has culled typical journals for publications relevant to structural stability. In this review, the effects of temperature on the structural integrity of FRPMCs are discussed from the perspective of matrix types, fiber types, nanoparticle (NP) modifications on resin matrix, and various related mechanical properties. For NP-modified FRPMCs, characterization of all anisotropic properties under various strain rates and temperatures becomes essential for analysis, design, and numerical simulations. Improving the structural stability of FRPMCs at different temperatures is an important direction. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48206.     

A new approach to increase weld line strength of incompatible polymer blend composites: selective filler addition

A ternary blend composite composed of two immiscible organic phases, polypropylene (PP) and polyamide-6 (PA), and talc as inorganic filler is studied in terms of weld line properties and morphology. Effects of different filler levels as well as compatibilizer on weld line strength under tensile loading condition of each polymeric phase are investigated. Special attention is paid to relate the nature of dispersed domains especially in weld line regions with final performance. It is observed from scanning electron microscopy (SEM) studies that addition of talc filler which is selectively wetted by dispersed PA phase dramatically reduces the elongated domain size in the weld line region and causes to much more homogeneous microstructure. The selective wetting of talc particles by PA phase, therefore, seems to be beneficial in increasing weld line strength via increasing the viscosity of the PA dispersed phase and consequently decreasing the elongated domains at weld line region. Compared to uncompatibilized blend composites, compatibilized ones represent much higher weld line strength for all levels of talc loading.     

A review of vapor grown carbon nanofiber/polymer conductive composites

Vapor grown carbon nanofiber (VGCNF)/polymer conductive composites are elegant materials that exhibit superior electrical, electromagnetic interference (EMI) shielding effectiveness (SE) and thermal properties compared to conventional conductive polymer composites. This article reviews recent developments in VGCNF/polymer conductive composites. The article starts with a concise and general background about VGCNF production, applications, structure, dimension, and electrical, thermal and mechanical properties. Next composites of VGCNF/polymer are discussed. Composite electrical, EMI SE and thermal properties are elaborated in terms of nanofibers dispersion, distribution and aspect ratio. Special emphasis is paid to dispersion of nanofibers by melt mixing. Influence of other processing methods such as in-situ polymerization, spinning, and solution processing on final properties of VGCNF/polymer composite is also reviewed. We present properties of CNTs and CFs, which are competitive fillers to VGCNFs, and the most significant properties of their composites compared to those of VGCNF/polymer composites. At the conclusion of the article, we summarize the most significant achievements and address the future challenges and tasks in the area related to characterizing VGCNF aspect ratio and dispersion, determining the influence of processing methods and conditions on VGCNF/polymer composites and understanding the structure/property relationship in VGCNF/polymer composites.     

乳液聚合法制备聚合物/石墨烯复合材料研究进展

综述了近些年来使用乳液聚合法制备聚合物/石墨烯复合材料的国内外研究现状,详细阐述了制备聚合物/石墨烯复合材料的乳液聚合方法,总结了乳液聚合法中聚合物的种类和石墨烯的改性方法以及复合材料的性能改善,并对乳液聚合法制备聚合物/石墨烯复合材料的应用领域和研究方向进行了展望。     

A novel method to prepare high-resistivity polymer composites

A novel method was developed for the preparation of high-resistivity conductive polymer composites reproducibly. The conventional method which involves the simple mixing of a conductive filler and a polymer usually produces a conductive polymer composite having a loading curve with a region in which the resistivity changes rapidly as the filler concentration changes. Hence, it is very difficult to obtain reproducible materials in that region. This newly developed method involves the preparation of a conventional conductive polymer composite, which is prepared by the simple mixing of carbon black and a polymer as the first step. The resulting compound, which is crosslinked by either electron-beam radiation or a chemical-crosslinking agent, is ground into a fine powder (composite filler) with the particle size less than 250 microns. The composite filler is mixed with another polymer to form a conductive particulate composite which has a loading curve showing a more gradual change of resistivity as a function of filler concentration. The modification of the loading curve is controlled by the resistivity, the shape, and the size of the composite filler.     

The thermal shock behaviour of ductile particle toughened alumina composites

Over recent years, it has been established that the incorporation of metallic particles into a ceramic matrix can lead to enhanced fracture properties. Relatively few attempts, however, have been made to establish whether or not the improved fracture toughness typically observed in such composite systems can offer improved performance in demanding environments. The current study is concerned with the thermal shock behaviour of a ceramic matrix composite consisting of an alumina matrix containing 20 vol% of discrete iron particles. The composite material has been produced by both hot pressing and conventional sintering techniques. The hot pressed composite shows a greater resistance to thermal shock than the monolithic matrix, both in terms of the critical temperature differential and retained strength, whereas the sintered material has been found to behave as a typical low strength refractory ceramic. The calculation of thermal shock resistance parameters for the composites and the monolith has indicated possible explanations for the differences in thermal shock behaviour.