Additives for cementitious and plaster products

Additives for cementitious and plaster products

Wednesday, 15 June, 2016

Introduction

BYK additives are renowned for providing formulators with tools to improve the properties of formulae where it would otherwise be difficult with the raw materials they are composed of. This applies to rheology additives that are designed for this sector. They provide the rheology profile sought by the formulator and also offer many advantages including lubrication, increased open time during drying and controlled water retention. Moreover, two solid defoamers have been developed that adapt to incorporation needs. Their primary function is to act as air release additives and, as a result, they improve levelling and compressive strength.

Optibent and Optigel: rheology additives for the construction sector

BYK’s rheology additives for the construction sector are based on phyllosilicates (natural smectites). Their structure is based on hydrophilic bentonite platelets that swell in contact with water creating a 3D network (“house of cards”).

Optibent and Optigel are the families of these products, the range of additives which allow formulators to reach optimal performance and meet specific requirements in each case. Unlike other phyllosilicates, such as sepiolites or attapulgites, BYK products provide viscosity (shear-thinning) and they do not absorb water, meaning it remains available for system curing.

Optibent products may be used as synergistic additives with cellulose ethers. Celluloses and starches retain a large volume of water, providing a somewhat pseudoplastic profile. Its polymer-based nature gives rise to an often undesired effect: a reduction in open time with the consequent loss of adhesion. The laminar shape of Optibent additives facilitates pumping and lubrication during manufacture and application, whilst reducing the movement of water to create a barrier effect and improve application. Formulators must reach a compromise between maximising adhesion and minimising sagging. The optimal ratio of the two products is 1 (Optibent) : 3 (cellulose).

The Optibent family incorporates two distinct product types: natural activated smectites (Optibent MF and 987) and those treated with protective colloid (Optibent 602, 1008, 6042, 1248, NT 10). Below is a brief description of each of them:

OPTIBENT MF/987	Anti-settling, low impact on viscosity, levelling. Grouts and waterproofing.
OPTIBENT 987	Anti-settling, low impact on viscosity, substitutes inorganic fibres and provides levelling. Jointing and emulsion-based pastes.
OPTIBENT 1008	Medium viscosity, smooth workability, compatible with redispersible resins. EIFS coatings, renders, pastes.
OPTIBENT 616	Partial substitution for organic thickening agents. Coatings.
OPTIBENT 602	Open time, sagging control, easy workability.
OPTIBENT 6042	Thick cementitious coatings, cement-based mortar.
OPTIBENT NT10	Rheology additive imparting hydrophobicity. Joints, grouts, skim coats and adhesives.
OPTIGEL WA	Highly pseudoplastic rheology additive for adhesives and aqueous paste.

Byk-1690SD and Byk-1691SD: powder defoamer for the construction sector.

Both defoamers have been designed for dry blend. Aside from releasing the entrapped air in an efficient way, these defoamers have no impact on the curing rate, providing levelling properties and increasing compressive strength. Byk-1690 SD is based on hydrocarbons and is considered a standard defoamer. Byk-1691 SD is polymer-based and highly efficient. They are the first products in a family that is expected to expand in the future.

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