Explore chapters and articles related to this topic
Solid–Liquid Phase Change Materials for Energy Storage
Published in Moghtada Mobedi, Kamel Hooman, Wen-Quan Tao, Solid–Liquid Thermal Energy Storage, 2022
A. Stamatiou, S. Maranda, L. J. Fischer, J. Worlitschek
For selected phase change materials, the addition of thickening agents, preventing density induced flow, to the aqueous solution helped to reduce irreversible segregation. These thickening agents are for example xanthan gum or carboxymethyl cellulose (CMC). However, adding thickening agents does not always solve the issue of segregation. It must be noted that the modification of segregating hydrated salt mixtures with thickeners has only been investigated with purely empirical methodologies based on trial and error. The exact mechanisms that allow for successful thickening in some materials but don’t work in others haven’t been elucidated in the framework of PCM research. Employment of multi-physics modeling as well as novel experimental techniques such as X-ray computed tomography which allows the in situ, non-invasive determination of the formation of new phases during thermal cycling, are expected to help in understanding the mechanisms of segregation and open new paths for the understanding of the key influencing factors and engineering of novel methodologies for the prevention of segregation.
Anaerobic Adhesives
Published in A. Pizzi, K. L. Mittal, Handbook of Adhesive Technology, 2017
Anaerobic adhesive chemistry is versatile and can accommodate the inclusion of a wide variety of materials designed to modify the properties of the adhesive. A number of additives have been employed to modify the viscosity and rheology. Examples of polymeric thickening agents that have been employed include polymethacrylates, polyesters, poly(vinyl acetate), polyacrylonitrile butadiene, and poly(vinyl chloride) [29]. The flow characteristics of anaerobic formulations can also be controlled by the addition of fumed silica, modified castor oil derivatives, and polyamides. These materials impart thixotropic properties.
Elements of Polymer Science
Published in E. Desmond Goddard, James V. Gruber, Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
E. Desmond Goddard, James V. Gruber
Polymers represent a significant share of raw materials used in the cosmetics industry. They are usually classified according to their use, such as thickening agents, film formers, resinous powders, and humectants. Thickening agents are used to adjust the viscosity of products to make them easy to use and to maintain the product stability. For example, they are used to ensure the stability of milky lotions and liquid foundations by preventing the separation of emulsified particles and powders. Thickening agents polymers are in widespread use for this specific purpose. Natural polymers, gums and resins, have been used in the industry since the early 1940s as water-soluble binders, thickeners, and film-forming agents. In today’s products they are added to many cosmetics formulations to fulfill these various functions, but often they are used simply because of the growing consumer demand for “natural products.” There are drawbacks, however, to the use of polymers isolated from natural sources: they vary in purity and physical appearance, and they are relatively expensive, compared to common synthetic polymers. Problems securing stable supplies coupled with variations in viscosity and microbial contamination led to a change to synthetic or semisynthetic substitutes. Synthetic or semisynthetic polymers, which are chemically modified natural polymers, have been developed to match the properties of gums and resins. Today, the industry is driven by a need of improved formulations, attainable through the use of current synthetic methodology and through the understanding of the molecular interactions between the polymers and the other components of a care product.
Synthesis, characterization, rheological and self-assembly behavior of polyelectrolytes hydrophobically modified with high styrene content: Effect of external parameters on thickening properties and nano-associations
Published in Journal of Dispersion Science and Technology, 2020
Hossein Khakpour, Mahdi Abdollahi
Thickening agents have attracted a lot of attention duo to industrial applications like enhanced oil recovery, drilling fluid, drag reduction, water treatment, coating and cosmetic area.[1–4] Water soluble copolymers such as polyacrylamides modified with a low amount of hydrophobic monomers, called as hydrophobically modified polyacrylamide (HMPAM), are one of the most important rheology modifier due to formation of hydrophobic nano-associations and physical networks.[2] The well-known method for HMPAMs synthesis is micellar technique, where micelles of the surfactant molecules create an appropriate place for association of the hydrophobic comonomer.[2,5,6] Depending on the emulsifier and hydrophobic comonomer concentrations, hydrophobic blocks with different lengths can be formed by penetration of radicals into the micelles, resulting in a multi-block copolymer microstructure with different hydrophobic block lengths.[1,7]
Effect of amphiphilic phosphate/octenylsuccinate starch on enhancing adhesion to hydrophobic polyester fibers in sizing
Published in The Journal of Adhesion, 2019
Modified starches have been considered as important products with advantageous properties which are used as additives due to their essential properties in food and non-food applications. [1] They have been used as thickening agent, sizing agent, emulsifier and stabilizer in a wide variety of products. [2–4] Recently, various amphiphilic polymers constituting both hydrophilic and hydrophobic segments [5–7] have received higher consideration. Amphiphilic polymers form spontaneous micelles which are enhanced by undergoing intra- or inter-molecular association between hydrophobic and hydrophilic segments. The design and characterization of novel modified hydrophobic polymers have received much attention due to their unique properties. As a result, in the recent years, many researches on hydrophobic modified starch and its derivatives have been conducted to offset the limitation in hydrophobic and/or hydrophilic starch for applicable use in many fields. [8] Such include amphiphilic benzyl and 2-hydroxypropyl-trimethylammonium starch. [6,7] They form micelles which enables them to be used in areas that involve hydrophobic and hydrophilic adhesion.
Double emulsion oil-in water-in oil (O/W/O) stabilized by sodium caseinate and k-carrageenan
Published in Journal of Dispersion Science and Technology, 2018
Tung Thanh Diep, Thoai Phan Dao, Hien T. Vu, Bao Quoc Phan, Duy Ngoc Dao, Tai Huu Bui, Vinh Truong, Viet Nguyen
However, using only SC is not enough to prevent completely the phase separation in O/W emulsions containing high water content. In this case, the large density discrepancy between two phases often leads to the sedimentation of the aqueous phase. K-carrageenan, a thickening agent, is a suitable support additive to limit this phenomenon since it can increase the viscosity of water. According to Figure 1, adding 0.5% KC prevented the phase separation in O/W emulsion (ratio 4/6) during 24 hours. However, using 1% KC contributed to lower surface tension of emulsion from 0.157 to 0.140 dyne/cm and led to the better results in droplet size (Table 2). Normally, in O/W emulsion, the smaller values of the average droplet size and the surface tension represented to a higher stability. Therefore, a combination of 0.5% SC and 1% KC was appropriate to stabilize the O/W emulsion with the ratio 4/6.