A Low Cost Tester of Glaze Melt Fluidity
A One-speed Lab or Studio Slurry Mixer
A Textbook Cone 6 Matte Glaze With Problems
Adjusting Glaze Expansion by Calculation to Solve Shivering
Alberta Slip, 20 Years of Substitution for Albany Slip
An Overview of Ceramic Stains
Are You in Control of Your Production Process?
Are Your Glazes Food Safe or are They Leachable?
Attack on Glass: Corrosion Attack Mechanisms
Ball Milling Glazes, Bodies, Engobes
Binders for Ceramic Bodies
Bringing Out the Big Guns in Craze Control: MgO (G1215U)
Ceramic Glazes Today
Ceramic Material Nomenclature
Ceramic Tile Clay Body Formulation
Changing Our View of Glazes
Chemistry vs. Matrix Blending to Create Glazes from Native Materials
Concentrate on One Good Glaze
Cone 6 Floating Blue Glaze Recipe
Copper Red Glazes
Crazing and Bacteria: Is There a Hazard?
Crazing in Stoneware Glazes: Treating the Causes, Not the Symptoms
Creating a Non-Glaze Ceramic Slip or Engobe
Creating Your Own Budget Glaze
Crystal Glazes: Understanding the Process and Materials
Deflocculants: A Detailed Overview
Demonstrating Glaze Fit Issues to Students
Diagnosing a Casting Problem at a Sanitaryware Plant
Drying Ceramics Without Cracks
Duplicating Albany Slip
Duplicating AP Green Fireclay
Electric Hobby Kilns: What You Need to Know
Fighting the Glaze Dragon
Firing Clay Test Bars
Firing: What Happens to Ceramic Ware in a Firing Kiln
First You See It Then You Don't: Raku Glaze Stability
Fixing a glaze that does not stay in suspension
Formulating a Clear Glaze Compatible with Chrome-Tin Stains
Formulating a Porcelain
Formulating Ash and Native-Material Glazes
Formulating Your Own Clay Body
G1214M Cone 5-7 20x5 Glossy Base Glaze
G1214W Cone 6 Transparent Base Glaze
G1214Z Cone 6 Matte Base Glaze
G1916M Cone 06-04 Base Glaze
G1947U/G2571A Cone 10/10R Base Matte/Glossy Glazes
Getting the Glaze Color You Want: Working With Stains
Glaze and Body Pigments and Stains in the Ceramic Tile Industry
Glaze Chemistry Basics - Formula, Analysis, Mole%, Unity, LOI
Glaze chemistry using a frit of approximate analysis
Glaze Recipes: Formulate Your Own Instead
Glaze Types, Formulation and Application in the Tile Industry
Having Your Glaze Tested for Toxic Metal Release
High Gloss Glazes
How a Material Chemical Analysis is Done
How desktop INSIGHT Deals With Unity, LOI and Formula Weight
How to Find and Test Your Own Native Clays
How to Liner-Glaze a Mug
I've Always Done It This Way!
Inkjet Decoration of Ceramic Tiles
Interpreting Orton Cones
Is Your Fired Ware Safe?
Leaching Cone 6 Glaze Case Study
Limit Formulas and Target Formulas
Low Budget Testing of the Raw and Fired Properties of a Glaze
Low Fire White Talc Casting Body Recipe
Make Your Own Ball Mill Stand
Making Glaze Testing Cones
Monoporosa or Single Fired Wall Tiles
Organic Matter in Clays: Detailed Overview
Outdoor Weather Resistant Ceramics
Overview of Paper Clay
Painting Glazes Rather Than Dipping or Spraying
Particle Size Distribution of Ceramic Powders
Porcelain Tile, Vitrified or Granito Tile
Rationalizing Conflicting Opinions About Plasticity
Ravenscrag Slip is Born
Recylcing Scrap Clay
Reducing the Firing Temperature of a Glaze From Cone 10 to 6
Single Fire Glazing
Soluble Salts in Minerals: Detailed Overview
Some Keys to Dealing With Firing Cracks
Stoneware Casting Body Recipes
Substituting Cornwall Stone
Super-Refined Terra Sigillata
The Chemistry, Physics and Manufacturing of Glaze Frits
The Effect of Glaze Fit on Fired Ware Strength
The Four Levels on Which to View Ceramic Glazes
The Majolica Earthenware Process
The Physics of Clay Bodies
The Potter's Prayer
The Right Chemistry for a Cone 6 MgO Matte
The Trials of Being the Only Technical Person in the Club
The Whining Stops Here: A Realistic Look at Clay Bodies
Those Unlabelled Bags and Buckets
Tiles and Mosaics for Potters
Toxicity of Firebricks Used in Ovens
Trafficking in Glaze Recipes
Understanding Ceramic Materials
Understanding Ceramic Oxides
Understanding Glaze Slurry Properties
Understanding the Deflocculation Process in Slip Casting
Understanding the Terra Cotta Slip Casting Recipes In North America
Understanding Thermal Expansion in Ceramic Glazes
Unwanted Crystallization in a Cone 6 Glaze
Variegating Glazes
Volcanic Ash
What Determines a Glaze's Firing Temperature?
What is a Mole, Checking Out the Mole
What is the Glaze Dragon?
Where Do I Start?
Why Textbook Glazes Are So Difficult

Binders for Ceramic Bodies

Description

An overview of the major types of organic and inorganic binders used in various different ceramic industries. By Nilo Tozzi

Article

Binders are substances that improve the mechanical strength of green ceramic bodies so they can pass through production steps, before firing, without breakage. In many cases, binder additions to bodies are essential (without them some production processes would be impossible). For instance, in the pressing process of powders, adding organic binders makes possible a forming method that is independent of the plasticity).

There are a wide variety of binders used in traditional ceramics, including natural products, like cellulose or clays, and synthetic products, like polyacrylates or polyvinyl alcohol.

A normal body binder must have several characteristics:

Inorganic Binders

Inorganic binders have a couple of very important characteristics: they are inexpensive and are not subject to attack by microorganisms. Another big bonus is that they never cause black coring.

Sodium Silicate

Its main use is in slip deflocculation. However it also improves the mechanical strength of dry pieces when employed in pressing and extruding operations. Behavior does change according to chemical composition of sodium silicates but, in the case of pressed tiles, often it is the best when the properties range toward some tendency to black core.

Magnesium Aluminum Silicates

Available products have different compositions because they are obtained from extremely plastic natural minerals (called smectites). Particles are off-white with colloidal sizes. When we add these binders to slips in the range 0.5-5% the mechanical strength of pieces proportionally increases. These binders are less effective than others but they have an important characteristic: they don t migrate during drying so we have less problem during glazing procedures.

Bentonite

This is a very plastic natural material mineralogically known as montmorillonite. It is used in the range 0.5-3.0% however it raises the viscosity of slips during milling (the maximum allowed percentage depends on characteristics of the material and on the permissible viscosity value). It improves mechanical strength of green and dry bodies and it also does not migrate during drying.

Organic Binders

Often organic binders are made from polymers with more or less long chains where polar groups are present. Most organic binders are soluble in water and behavior is like a surfactant (it improves contact between liquid and solid phases). Short chain binders are adsorbed on the surface of particles and during drying water elimination from hydroxyl groups produces tridimensional hydrogen bonds (among the molecules of binder distributed on the surface of the particles). The development of chemical bonds contributes to a stronger tridimensional structure and mechanical strength improves proportionally to the amount of organic binder. Long chain binders have poor solubility in water but are emulsifiable. During drying they are not absorbed at the surface of particles but they are able to form tridimensional hydrogen bonds.

Usually organic binders do not improve the strength of green pieces before drying. Drying strength rises proportional to the added amount of binder (actually it can even reach values 30% higher). Theoretically, organic binders burn off on firing at low temperatures with minimal residue. Nevertheless, these binders are increasing the organic matter content in bodies, experience has shown that pressed tiles employing organic binders are quite subject to black coring problems.

Often organic binders are decomposed by bacteria and we have to add an anti-bacterial agent to stabilize slips. Organic binders are also used in glazes and engobes to ensure good adhesion to the ceramic surface, prevent sedimentation and improve rheological properties.

The most popular are:

Polyvinyl Alcohol

Usually it is used as a binder for glazes, during glazing operations, before the screen printer (a water solution of polyvinyl alcohol is sprayed on the surface to be decorated). It is a strong surfactant and binding power is connected to its ability to wet particles (products having a low molecular weight exhibit low viscosities and they have a minimal effect on the viscosity of glazes or body slips). It is stable because it does not ferment. Usually suppliers propose water solutions of polyvinyl alcohol.

Starches

Starches are powdered forms of a group of carbohydrates producing colloidal emulsions in water having strong binding properties (however some times modified starches are supplied as liquids).

Often they are not fully soluble in water because of their high molecular weight (this characteristic prevents migration during drying). It is possible to mix starch and dry ceramic powders (after which the mix can be wetted, formed and dried). Starches quickly ferment. Chemical derivatives have properties like esters of cellulose but are not stable against bacteria.

Carboxymethylcellulose

It is a white-yellow powder soluble in water. It can migrate during drying (thus the distribution in the body matrix may not be uniform). There are different types with different molecular weights. Carboxymethylcellulose products with medium or high molecular weights are stronger binders but they increase viscosity of slips so they cannot be used above certain percentages (thus not fully developing their binding properties). These products improve the plasticity and mechanical strength of dry bodies and completely burn out during firing, however they are expensive.

Dextrin

A yellowish powder obtained by treating certain starches with small amounts of acid. Dextrin is a strong binder and is some times used to prepare glaze grains for dry application or as a "glue" for glaze slips to improve adherence to the ceramic body. Dextrin also improves the plasticity of clay slips.

Wax Emulsions

Wax emulsions behave like inter-particle lubricants when bodies are wet and like binders when dry. They are widely used for the production of technical alumina components.

Polyethylene Glycols

Polyethylene glycols having low molecular weights are viscous liquids often used as plasticizers or lubricants. Those having high molecular weights are waxy solids that are used as binders and plasticizers in pressing. They are water soluble and often used as basic mediums for the preparation of printing colors.

Lignosulfonates

Lignosulfonates are yellowish powders having variable compositions and also variable molecular dimensions (because they are polymers that can be modified by the addition of organic or inorganic groups to the molecule). They are anionic derivatives of lignin, water soluble and surfactants. Lignosulfonates are very effective in increasing mechanical green and dry strength in ceramic pieces. In addition, they act as lubricants during extrusion or pressing operations. Additions of lignosulfonates to ceramic slips can vary from 0.1 to 2.0% and they are relatively inexpensive. For pressed tiles, 1% lignosulfonate can double mechanical strength (however often a black core appears). Lignosulfonates are often used to reduce shrinkage yet maintain after-forming mechanical strength (because reduced amounts of plastic clays are needed).

Methylcellulose

A derivative of cellulose (when treated with methylene chloride and alkali under pressure). The composition is variable depending on the length of chains and methylcelluloses are non-ionic polymers, water soluble at low temperature. They are very stable against microorganisms but they have tendency to form foam. Methylcelluloses have different viscosities in water (depending the length of chains) and strong deflocculating properties. Often methylcelluloses are used as temporary binders in refractory production and other technical ceramics because they are at the same time lubricant and wetting agents and plasticizers. Hydroxyethilcellulose is a similar product having less tendency to form foam.

Paraffins

Mixtures of paraffins and carnauba wax are widely used as binders for the production of special pieces obtained by cold isostatic or normal pressing. The nature of mixtures is determined by the dimensional tolerance needed and the shapes of edges. Mixtures as liquid emulsions are blended for specific purposes and they also have binding, plasticizing and lubricating properties.

Polyacrylates

Sodium and ammonium salts of polyacrylate acid are water soluble and they are mainly used as strong deflocculants. They can also act like binders but their cost curtails usage for this purpose. Polyacrylate esters are not soluble but they have a similar behavior.

Related Information

Links

People Nilo Tozzi
Materials Starch
Materials Carboxymethylcellulose
Materials Wax Emulsion
Materials Polyethylene Glycol
Materials Lignosulfonate
Materials Methylcellulose
Materials Paraffin Wax
Materials Sodium Polyacrylate
Materials Polyvinyl Alcohol
Materials Veegum
Materials Dextrin
Materials Sodium Silicate
Materials Bentonite
Materials Additive 'A'
Materials Darvan
Glossary Ceramic Binder
Binders harden ceramic powders as they dry. They enable the use of less plastic material mixes that can still adhere and be dry durable.
Tests Modulus of Rupture - Dry
Tests Dry Strength (kgf/cm2)
Tests Dry Strength (Square Bars)
Tests Dry M.O.R. (50% Silica)
Typecodes Ceramic body and glaze binders, plasticizers

By Nilo Tozzi


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