emollientandrheologicaladditives-200720174604.pptx

Good

1. Dept. of Pharmaceutics, Vishal Institute of pharmaceutical education and research Ale PREPARED BY: Omkar mandlik M.Pharm RHEOLOGICAL ADDITIVES , CLASSIFICATION AND APPLICATION

2. CON T EN T S Rheological additives Introduction Classification Application 2

3. Rheology is the science of flow. Every time a lotion is poured, a cream squeezed from a tube or a lipstick applied, rheology is involved. Even when products are at rest, it plays an important part in controlling stability and suspension. Understanding a formulation’s rheological needs enables to create the best possible products 19

4. The rheology of a system is described in terms of its viscosity Viscosity is the resistance to flow and defined as the force applied by the resulting rate Shear stress is the force per unit area applied and shear rate is the resulting velocity gradient 20

5. 21 A material which maintains a constant viscosity, regardless of shear rate, has Newtonian flow (Fig.2). Dilatant flow (Fig.2) is a form where viscosity increases with shear, sometimes encountered in highly pigmented/filled systems.

6. The rate of recovery of a system when stress is removed is also very important. When a shear thinning system shows delayed viscosity recovery, it is described as thixotropic (Fig.3). 22

7. Pseudoplastic flow (Fig. 4), also known as shear thinning behaviour, and typical of many commercial systems, is when viscosity decreases with increasing shear rate. 23

8. Cosmetics experience shear rates varying from 0.001 s-1, from gravitational forces; to over 20,000 s-1, when a cream is spread or an aerosol antiperspirant sprayed (Fig 1) 24

9. ELEMENTIS Specialties Rheological Additives for Cosmetics ELEMENTIS Specialties rheological additives can be broadly divided between aqueous-phase thickeners and non-aqueous-phase thickeners. But it is important to remember the advantages of oil- phase viscosity modification that can greatly improve emulsion based products. ELEMENTIS Specialties additives for cosmetics are based on naturally occurring materials: highly refined and beneficiated hectorite clay or castor oil derivative 25

10. 1. Aqueous-phase thickeners Rheoluxe Associative Thickeners The Rheoluxe family of rheology modifiers are non-ionic polymeric thickeners designed specifically for the personal care market. Rheoluxe consists of urethane based and Polyether Polyol based associative thickeners with superior performance in difficult systems such as those containing high salt levels or with extremes in pH. Due to its structure, Rheoluxe is soluble in water, but associates with lipophilic materials to build viscosity. 26

11. Associative thickeners – mechanism of action Associative thickeners increase the viscosity of aqueous systems through a system of molecular associations and interactions. The thickeners consist of water soluble polymeric chains modified with hydrophobic caps. The hydrophobic caps of the polymer associate, that is build a structured network with other hydrophobes in the formula. This results in micelle type structures that form a network resulting in significant viscosity build. 27

12. HECTORITE Hectorite is a unique swelling clay offering several advantages. hectorite’s special properties, compared with bentonite, are: lower iron content lighter colour higher swelling capacity greater gel strength no crystalline silica Due to its small size, platelet shape and large surface area, hectorite is able to form strong, stable viscous gels. 30

13. BENTONE hydrophilic Clays BENTONE MA, EW, and LT rheological additives provide thixotropy and suspension control to the aqueous phase. BENTONE MA and EW additives form gels by producing an open, 3-dimensional network of the individual clay platelets as shown in Figure5 31

14. 2. Non-Aqueous-Phase Additives Surfactants can influence the rheological behaviour of hydrophilic clays. Non-ionic surfactants, if they are highly ethoxylated, can adsorb onto the clay surface. This rarely causes problems either in flow control or activity of the formulation. Anionic surfactants can act as dispersing agents and weaken the gel structure. Alternatives that eliminate or minimise any problems can normally be found. Cationic surfactants interact strongly and should be avoided. Organic and silicone-based liquids used in oil and wax-based cosmetics, and as the non-aqueous-phase in emulsions, benefit greatly from ELEMENTIS Specialties rheological additives. Outstanding rheological properties are developed using BENTONE organoclay rheological additives in their powder form or, even better, with BENTONE GEL additives, their predispersed forms. 33

15. ADVANTAGES thermostable viscosity control thixotropic flow suspension control of pigments and actives emulsion stabilisation silky skin feel BENTONE organophilic Clays Hectorite is now reacted with special vegetable quaternary ammonium salts to produce organoclays able to thicken and gel organic liquids. The correct choice of BENTONE additive is determined largely by the polarity of the system to be thickened. 34

16. BENTONE organoclays form thixotropic gels by dev e l opi n g h y drogen bond bridges between the edges of adjacent platelets as shown in Figure 35

17. Thixcin R Rheological Additive For the highest degree of thixotropy in aliphatic liquids, Thixcin R additive is the product to use. In addition to its effective rheological properties, it gives water repellence, stabilises emulsions and acts as a stiffening agent in lipsticks and ointments. It can also be used as a dry binder in pressed powder systems. It is a castor oil derivative. It requires temperature-controlled activation within the range 55-60°C (130-140°F) and high-shear mixing to develop its full structure. 37

18. APPLICATION Stick products (lipstick and antiperspirant) m a i n t a i n ho m og e n eit y i n m o l t e n a nd s e t ti n g stages gain improved pay-out increase high-temperature integrity eliminate oil migration reduce “creasing” around lips and eyes Mascara improve film-build increase water-resistance eliminate oil migration 38

19. Emulsions e l ev a t e d r o p - po i n t t e m p e r a t u re o f w a t e r - i n - o i l creams eliminate syneresis improve emulsion stability enable cold-process emulsification create novel viscosity effects UV Sunscreen eliminate ultrafine Ti02 skin-whitening problems enhance sun protection factor (SPF) optimise use of sunscreen actives reduce separation and settlement 39

20. Antiperspirants aerosols uniform distribution of active ingredients soft and dry skin feel significant less whitening reduced separation and settlement 40 REFERED: http://www.elementisspecialties.com/esweb/webprodliterature.nsf/allbydo cid/3BCB996F45DEBB93852575FB004C77BA/$FILE/Rheology%20cosmet ics%20brochure%20Dec-2013.pdf