R1800-SK and R900A for flame-retardant dispersion without affecting flame retardancy

R1800-SK and R900A can be used with any flame retardant, and with any flame-retardant masterbatch, in any form: powder additives, liquid additives, granular flame-retardant masterbatch. The dispersion can be achieved, and flame-retardant performance is not affected. This is not a slogan. What follows sets out the mechanism and the measured data from the technical documentation that show why it holds.

1Start with the problem that has to be solved

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The flame-retardant masterbatch is produced, yet the UL94 grade jumps between V-2 and V-0; dripping behaviour is unstable and the colour mottles. The usual engineering lines of investigation are to change the flame-retardant batch, adjust the screw configuration or lengthen the residence time, but the problem is often not in the flame retardant itself.

The great majority of flame retardants are solid powders insoluble in the resin: brominated systems are crystalline powders, phosphorus systems are white powders or crystals, nitrogen systems are needle-like or plate-like crystals, and inorganic hydroxides are mineral powders. In the resin they must be "broken down to the level of primary particles and held there" before flame-retardant efficiency corresponds to the loading. Once the powder agglomerates, the same 15% loading leaves a much smaller effective surface area actually taking part in flame retardancy, and this shows up as "the same formulation giving a different grade from batch to batch".

A dispersant addresses exactly this: it keeps the particles at a spacing in the melt.

There is a usual concern here: a dispersant is an organic substance, so does adding one to a flame-retardant system drag down the flame-retardant performance? Kaicu answers this with mechanism and measured data, not with slogans.

2How R1800-SK opens up the powder

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The molecular structure of R1800-SK has two parts. The wording of the technical documentation is:

• Anchoring groups (-COOH) — polar groups that adsorb onto the powder surface through ionic bonds, hydrogen bonds and van der Waals forces. What the documentation emphasises is "tight adsorption" and "preventing desorption of R1800-SK".
• Solvating chains — extend into the medium and determine the stability after dispersion.

Temperature is the key. The documentation states: below 70℃ the coating layer does not melt; above 70℃ it begins to melt, converts into ionic coupling and improves compatibility with the resin.

This is not a detail written down casually. The powder stage requires "hold the particle firmly and allow no further agglomeration"; at the melting temperature it requires "let go and become compatible with the resin" — two opposite requirements, and R1800-SK meets both with a single temperature switching point.

The documentation is equally specific about the mechanism of stable dispersion: when pigment particles carrying adsorbed R1800-SK approach one another, the repulsion of the adsorption layers makes the particles push each other apart — the spacing is not maintained by continuous stirring but held open by the adsorption layers themselves.

3What these two dispersants are

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What these two…

Item	R1800-SK	R900A
Product positioning	Polyolefin ether hyperdispersant series	General product catalogue · liquid colour masterbatch route
Ionic type	Non-ionic	Non-ionic
Appearance	Blue paste-like substance	Not listed in the documentation
Density	1.190 g/cm³	Not listed in the documentation
Viscosity	980–3600 mPa·s	Not listed in the documentation
Acid value	6.8–7 mgKOH/g	Not listed in the documentation
Amine value	≦9 mgKOH/g	Not listed in the documentation
Flash point	285℃	Not listed in the documentation
Degree of dispersion	III	Not listed in the documentation
Compatibility	Very good compatibility with all rubbers and plastics	Applicable to the addition of almost any plastic or rubber

Both are non-ionic. This is the premise on which the article stands — a non-ionic product carries no charge and does not compete with the ionic components in a flame-retardant system.

4Which flame retardants exist, and why changing to another does not affect flame retardancy

X-axis = dimension ℃; colored band = target interval where the object can fall; points outside the band = portions that cannot be reached.

270297.5325352.5380℃Target band275300325350375Brominated335–345℃Inorganic300–320℃X-axis same dimension ℃ ·X-axis scale based on this article's max (300–345 ℃); do not directly compare lengths across articles.

• Target band
• Brominated
• 335–345℃
• Inorganic
• 300–320℃
• X-axis same dimension ℃ ·
• X-axis scale based on this article's max (300–345 ℃); do not directly compare lengths across articles.

• Brominated335–345 ℃
• Inorganic300–320 ℃

Chart data (source text verbatim)

Object	Range
Brominated	335–345 ℃
Inorganic	300–320 ℃

Source textScale 270–380 ℃

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This is the core question of the article. The engineering concern about whether a dispersant drags down flame retardancy usually comes from an implicit assumption: that there may be a chemical interaction between the dispersant and a given flame retardant. To judge whether that assumption holds, the flame retardants must first be separated by mechanism of action, and then it must be seen which step the dispersant intervenes in.

By chemical composition and mechanism of action, industrial flame retardants can be grouped into the families below. The mechanism column gives only the recognised flame-retardant pathway of the family, not formulation details irrelevant to this article.

Which flame re…

Family	Representative grades (common abbreviation)	Main components	Main flame-retardant pathway	Processing temperature range
Brominated	Decabromodiphenyl ethane (DBDPE)	Aromatic bromide, bromine content about 82%	Gas phase: releases bromine radicals on heating and interrupts the combustion chain reaction	Melting point about 335–345℃, 1% thermal weight loss ≥ 350℃
Brominated	Brominated polystyrene (BPS)	Brominated polystyrene, about 66% bromine	Gas-phase termination of halogen radical chains	1% thermal weight loss ≥ 300℃
Brominated synergist	Antimony trioxide (Sb₂O₃)	Antimony oxide	Reacts with hydrogen halide to form antimony halide, strengthening gas-phase termination	Does not decompose itself, follows the system
Phosphorus	Aluminium diethylphosphinate (ADP)	Organic aluminium phosphinate salt, about 23–24% phosphorus	Condensed phase: catalyses dehydration and crosslinking into char	Decomposition temperature > 370℃ (activated type)
Phosphorus	Ammonium polyphosphate (APP)	Nitrogen-containing phosphate, phase I / phase II	Condensed-phase char formation plus gas-phase dilution, the main acid source in intumescent systems	Phase II has low water solubility and suits high-temperature processing
Phosphorus	DOPO and its derivatives	Phosphaphenanthrene oxide	Reactive type, covalently incorporated into the epoxy network	Curing systems, not melt processing
Nitrogen	Melamine cyanurate (MCA)	Addition salt of melamine and cyanuric acid	Endothermic sublimation on heating plus dilution of combustible gas	Stable at 300℃, endothermic decomposition at about 350℃
Nitrogen	Melamine polyphosphate (MPP)	Melamine phosphate	Phosphorus–nitrogen synergy, char formation plus expansion	Same order as APP
Inorganic	Aluminium hydroxide (ATH)	Aluminium trihydrate	Endothermic decomposition releasing water of crystallisation, diluting and cooling	Starts dehydrating at about 200℃, loadings often 50–65%
Inorganic	Magnesium hydroxide (MDH)	Magnesium hydroxide	Same as ATH but higher temperature resistance	Endothermic decomposition at about 300–320℃
Inorganic	Zinc borate / expandable graphite	Borate / layered graphite	Char formation, smoke suppression, anti-dripping	Follows the system
Intumescent	IFR composite system	APP + pentaerythritol + melamine	Acid source / carbon source / gas source form an intumescent char	Follows the system

This table makes only one point: the working position of every family above lies at the level of "the flame retardant itself decomposing on heating or taking part in char formation or gas-phase reaction". The dispersant is not on that chain — its anchoring groups adsorb on the powder surface and its solvating chains extend into the melt; both actions are interfacial physical behaviour. They do not enter the decomposition pathway of the flame retardant, do not consume halogen radicals, do not take part in dehydration and char formation, and do not change the conditions under which the intumescent layer forms.

So the answer to "does changing the flame retardant affect flame retardancy" depends on whether the dispersant undergoes a chemical reaction with that family, not on whether the family is brominated or phosphorus-based. R1800-SK and R900A are both non-ionic and carry no dissociable groups: they are not treated as a reaction partner by halogen systems, nor do they compete for adsorption with the acidic sites of phosphorus systems — their role in every family is the same: to disperse the powder.

Kaicu's own eight flame-retardant masterbatches are a real-world sample of this judgement: eight grades, different flame-retardant systems and base resins, all formulated with the same dispersant.

How to read this table needs to be stated: the addition levels and flame-retardant ratings of the first four grades (R911 / R912 / R912B / R915) are found in the current public technical documentation and can be quoted directly; for the last four grades (M911 / M915 / M918 / M830) the current public documentation confirms only one item, "the dispersant used in the formulation is R1800-SK"; their addition levels and flame-retardant ratings do not appear in the public documentation and are recorded as "not listed"; this article makes no inference about them.

This can be cross-checked in three places in the documentation: the "core component — dispersion aid" column of the R912B technical data gives the dispersant as a non-ionic surfactant; the compatibility entry for R1800-SK states "very good compatibility with all rubbers and plastics"; and R900A states "applicable to the addition of almost any plastic or rubber". None of the three restricts the scope of application to a particular flame retardant or a particular base resin.

5The dosage turning point: 1.6%, and it reverses

This is the only set of point-by-point measured data in the article, taken from the surface-treatment experiment of R1800-SK on titanium dioxide: seven dosage points under constant conditions of pH 6.8 and 70℃.

Dosage %	Lightness L	Tünber whiteness	Yellowness YI
0	88.27	75.15	4.63
0.5	88.89	75.76	4.21
1.0	89.12	76.31	4.34
1.2	89.87	76.35	4.23
1.6	90.18	77.76	3.84
1.8	88.26	75.81	3.97
2.0	87.83	75.79	3.89

All three indices reach their optimum at 1.6% at the same time: highest lightness 90.18, highest whiteness 77.76, lowest yellowness 3.84.

4Data figure 4

Thin film optical density (hiding power)R1800-SK dosage %00.10.20.30.40.3%0.5%1%1.6%2%1.6% · 0.386Range start 0.3%Range end 2.0%

• Measured point1 point
• Trend (dashed line, not measured)0.3%–2%

5Data figure 5

90.18Lightness L77.76Tünber whiteness3.84Yellowness YI0%0.5%1%1.6%2%R1800-SK dosage %

• Lightness L88.27 → 90.18 (peak) → 87.83
• Tünber whiteness75.15 → 77.76 (peak) → 75.79
• Yellowness YI4.63 → 3.84 (minimum) → 3.89

The mechanism given in the documentation is: as the dosage increases, more anchoring groups adsorb onto the pigment surface, reaching saturation at 1.6%, where the optical density is at its maximum (0.386); as the dosage increases further, the R1800-SK molecules interact with one another and entangle through their solvating chains to form "bridging flocculation", and the optical density falls sharply instead.

The conclusion as worded in the documentation:

A dosage of 1.6% of the R1800-SK hyperdispersant gives the best result when treating titanium dioxide

This is a counter-example to "the more the better". An excess of hyperdispersant bridges the pigment particles by itself, and the result gets worse.

In addition, the addition level given in the documentation is 0.5%–1% of the final plastic product. Note that this 0.5%–1% and the 1.6% above have different denominators — the former is the finished plastic, the latter is a treatment level relative to the pigment, and the two numbers cannot be interchanged.

6Why it does not affect flame retardancy

The documentation lists four functions of the hyperdispersant in the masterbatch:

1. 01Preventing agglomeration of pigment and filler — it wets and bonds with the powder and, as the temperature falls, forms a coating layer that blocks further agglomeration
2. 02Raising the distribution of the filler in the resin — it is compatible with the resin during extrusion and joins the coated powder and the resin into one body
3. 03Ensuring good melt flow and improving the surface gloss of the part
4. 04Fusing with the resin more effectively

All four point to "physical dispersion" and "processing performance"; none points to chemical participation or to a flame-retardancy mechanism.

The boundary of the conclusion must be stated: the "does not affect flame retardancy" of this article rests on the dispersant's mechanism of action not intervening in the flame-retardant reaction; it is not based on a family-by-family comparative UL94 test covering all flame-retardant families. The direct evidence in Kaicu's public technical documentation is that in the R912B formulation the dispersant is also listed as a "dispersion aid", and that the compatibility statements for R1800-SK / R900A cover "all rubbers and plastics" and "any plastic or rubber"; the documentation gives no separate comparative test data for families such as brominated systems or inorganic hydroxides, and this article makes no inference.

7How to read 113 times and 26 times

The technical data for R1800-SK gives two relative multiples: dispersing performance 113 times and lubricating performance 26 times.

The object of comparison for both figures is wax; they are relative statements within the same technical documentation, and the documentation gives neither the corresponding test method nor a third-party report. The correct reading is "the dispersing / lubricating performance relative to wax", not "113 times can be achieved in any system", and the figures cannot be converted directly against the 1.6% turning point — the denominator of one is a performance comparison, the denominator of the other is a pigment treatment level.

8A few practical judgements for formulators

A dispersant is not a flame retardant and should not be evaluated as one. Its delivery criterion is "whether the powder is uniformly dispersed and held that way", and that criterion is the same thing in brominated, phosphorus, nitrogen, inorganic and intumescent systems.