activated rubber crumb in waterborn surface coating

Macromol. Symp. 2012, 315, 205–211 DOI: 10.1002/masy.201250525 205

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Activated Rubber Crumb in Waterborn Surface Coating

K. K. Suma,1,2 Sinto Jacob,2,3 Rani Joseph*2

Summary: This study investigates the properties of a matt finishing paint formulated

using Vinyl acetate (VAc) - Butyl acrylate (BuA) copolymer latex (water based resin

system) and activated rubber crumb (matting agent). Vinyl acetate - Butyl acrylate

copolymer prepared by semicontinuous emulsion polymerization. The copolymer

emulsion mixed with dispersion of rubber crumb to make the surface coating.

Presence of rubber crumb may actively resist the attack of chemicals and climate

conditions.

Keywords: butyl acrylate; coatings; copolymer, rubber; vinyl acetate

Introduction

Matt paints are used on large areas such as

walls and ceilings, including plaster boards,

hard board, brick, cement rendering,

foamed polystyrene and most wall papers,

where the easy application, quick dry, and

lower odour of water-borne dispersion

paints are major advantages. The conse-

quences of poorer flow and lapping are not

readily visible and never seen as an

insurmountable disadvantage.[1] The con-

sequences of flow deficiencies were more

visible, and durability requirements more

demanding, e.g. for cleaning in corridors of

schools, hospitals, factories, and in areas of

high condensation such as kitchens and

bathrooms.[2–4] Consequently, this sector

split to water-based and solvent-based

technologies.

Matt formulations contain a resin system

and a matting agent. The matting agent has

a surface moiety. Paints with low amounts

of binder have a high ratio of pigment

volume to binder volume, a condition

epartment of Chemistry, Maharajas College Erna-

lam, Cochin-682011, India

epartment of Polymer Science & Rubber Technol-

y, Cochin University of Science &Technology

chin- 682022, India

mail: [email protected]

J. Murphy Research Centre, Rubber Park India (P)

d., Kochi, Kerala, India

yright � 2012 WILEY-VCH Verlag GmbH & Co. KGaA

referred in the coatings literature as a high

pigment volume concentration (high PVC).

These paints may have poor cohesive and

adhesive properties. They normally have a

matte appearance and are often in a

powdery, friable, and flaking condition.

Their treatment requirements differ from

paints containing higher proportions of

binder (such as commonly encountered

linseed oil or acrylic paints) in that

consolidants are easily absorbed into the

paint and fill voids between the pigment

particles. However, cohesion of the paint

and adhesion to the substrate increased by

the presence of resin, filling of void spaces

between the pigment particles may cause

changes in the final appearance of the paint

that is practically irreversible. The matte

paint is to use a consolidation system that

distributes the consolidant in a manner that

minimizes changes in appearance, intro-

duces the minimum quantity necessary to

achieve effective cohesion of the paint and

adhesion of the paint to the substrate, and is

compatible with the paint and support

materials in the long term.[5–11]

Present study utilizes crumb rubber

powder as matting agent. Crumb rubber

essentially has two effects, i.e. interaction

effect (IE) and particle effect (PE). Inter-

action effect is the absorbing of aromatic

oils from the binder. The PE is the action of

crumb as filler. As with any filler, the

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Macromol. Symp. 2012, 315, 205–211206

addition of crumb affects the rheology of

the binder by increasing the viscosity and

reinforcing the binder to some extent.

Crumb rubber can modify by using sur-

face-active agents. Surface activation not

only improves the dispersion of crumb

rubber particles but also increase the

adhesiveness. In some applications, surface

activated crumb rubber used for moulding

by itself, without using any binders or

additives.[12–22] Surface activation of rubber

powder by water also reported.[23] Surface

activation improves the surface area of

the powder compared to ordinary rubber.

The water activation has not a great effect

on the surface morphology. Removal of

light oils from the crumb rubber particles is

the main aim of this procedure.

The purpose of this work is the devel-

opment of new matt finished surface coat-

ing using rubber crumb as filler. This will

reduce the coast of the paint and increase

the resistance of external attack. The main

advantage of this work is the effective

utilization of waste rubber crumb to reduce

the environmental pollution.

Matt finished surface coatings prepared

by varying the amounts of rubber crumb.

Optimum level of rubber crumb addition

selected according to the easy of brushing and

good dispersion formation. The performance

of formulated matt finished paint compared

with paint without rubber crumb and com-

mercially available emulsion paint.

Table 1.Composition of rubber crumb.

Ingredients Percentage

Natural rubber 35%Synthetic rubber 15%Carbon black 30%Oil 10%Accelerators, Antiozonants, etc. 10%

Experimental Part

Rubber crumb powder was purchased from

M/s. Rubzen Aggrigates, Rubber Park,

India. CaCO3, Propylene glycol, Carboxy-

methyl cellulose, Potassiumtripolyphosphate

and Sodiumhexameta phosphate were AR

grade obtained from Merck. Commercial

grade Kaoline, Volcastab and Triton-X100

were used. Conventional TiO2 (particle size

�0.2mm and surface area �8.07m2/g) pur-

chased from Travancore Titanium product

Ltd. Vinyl acetate (VAc)-n-butyl acrylate

(BuA) co-polymer latex prepared as per the

procedure described by Suma et al.[24]

Copyright � 2012 WILEY-VCH Verlag GmbH & Co. KGaA

Activation of Crumb Rubber

Rubber powder (from used rubber pro-

ducts) used as matting agent for the present

study. It contain 50% rubber hydrocarbon

and the rest is carbon black, oil etc. Table 1

shows typical composition of crumb rubber.

400 g of crumb rubber mixed with 800 g

of distilled water. The mixture then heated

up to 85 8C and blended for a period of

60min. The slurry filtered and dried at

29 8C for a period of 5 hour. Hot water

removes the excess oils and chemicals

present in crumb rubber particles.[23] The

rubber crumb dispersed in different med-

iums such as water (H2O), aqueous solu-

tions of carboxymethyl cellulose (CMC),

sodium hexametaphosphate (HMP) and

dodecyl benzene sulphonicacid (DS-10) to

study the dispersion stability. Aqueous

solution of carboxy methyl cellulose found

to be stable even after 1 week. Figure 1

shows the dispersion stability of rubber

crumb powder in various mediums after

one week.

Development of Surface Coating

Dispersion of rubber crumb in aqueous

solution of carboxy methylcellulose and

Vac-BuA latex mixed with various ingre-

dients to prepare latex paint (PB) and matt

finished paint (PBR) as described in Table 2.

VAc-BuA copolymer of 45% solid content

used for making all formulations.[24]

Tests for Paint Evaluation

Sample Preparation

Mild steel panels were used for the

preparation of tests samples according to

BS specification 1449 (6 in.� 4 in.). Panels,

free from surface imperfection such as

rolling marks, scores and corrosion, thor-

, Weinheim www.ms-journal.de

Figure 1.

Appearance of dispersions of rubber crumb in water and aqueous solutions of various dispersing agents after

one week.

Macromol. Symp. 2012, 315, 205–211 207

oughly degreased with trichloroethylene

and dried. The panels were then abraded on

the test side with 180 grade silicon carbide

paper and then wiped with SBPS 40/65

(special boiling point solvent which is the

volatile fraction derived from petroleum at

Table 2.Paint formulation with rubber crumb.

Ingredients Weight (g)

�PB ��PBR

Water 35 35Triton-X100 0.42 0.42Potassium tripolyphosphate 0.42 0.42Sodium hexametaphosphate 0.42 0.42Volcastab 0.42 0.42Silicone emulsion 1.34 1.34Propylene glycol 4 4Acticid SPX 0.32 0.32

Above ingredients intimately mixed using a low speedball mill. Then following ingredients added and mixedusing high-speed mechanical stirrer.

Kaolin 17 17Calcium carbonate 18.64 18.64TiO2 (Rutile) 44.6 44.6

After 20 minutes following ingredients added bystirring.

Carboxymethyl cellulose 0.74 0.74Silicone emulsion 0.92 0.92

The whole mixture stirred for 10 minutes at highspeed. Then polymer emulsion added.

Polymer emulsion 75 75Rubber crumb 0 3

�PB-Paint without crumb rubber.��PBR-Paint withcrumb rubber.


the range 40–65 8C) to remove any con-

taminates. Care should be taken that there

should not be any time gap between

degreasing and painting. The coated panels

were air dried as required without any

contamination.

Water Resistance

This test uses to assess the resistance of

paint towards water. It referred as blister

resistance. Blister formation during the test

assessed by ASTM D 714-56 standard. A

thermostatically controlled rectangular

water bath of 5 L capacity equipped with

mechanical stirring used for this test.

Salt Spray

This test is to assess corrosion resistance of

the surface coatings. The test conducted

according to British standards Institution

Method BS 3900 standards.

Alkali and Resistance

Resistance towards three types of alkalies

(Na3PO4 at 75 8C, Na2CO3 at 65 8C and

NaOH at 28 8C) assessed according to

ASTM D 714-56 standards. Temperature

for the test and duration of test selected as

per the same ASTM standard.

Scotch Test

The cross-cut adhesion test (scotch test)

was carried out according to ASTMD3359-

02. An area free of blemishes and minor

surface imperfections selected for the test.


Figure 2.

Appearance of specimens before and after water

resistance test.

Macromol. Symp. 2012, 315, 205–211208

A die with a number of close-set parallel

blades pressed on the test specimen in two

directions, at right angles to each other. The

second pressing superimposed on the first,

giving a pattern of squares. A strip of self-

adhesive tape (3M Scotch Blue Painters

Tape) stuck over the pattern then removed,

and the adhesion of the film is assessed from

the amount of the coating removed. The

tape keeps in contact for 10 seconds and

then stripped by pulling the tape back on

itself at an angle of approximately 1208.

Viscosity

Viscosity and shear thinning behaviour of

surface coatings carried out using rotational

viscometer (Brookfield type – RV series)

with shear rate varying from 0.1 to 50 sec�1.

The test conducted according to ASTM

D2196-05 at room temperature (28 8C).

Table 3.Blister formation in water resistance test at 38 8C.

Time interval Number and size of the blister

PB PBR Commercial

24 hrs Nil Nil Nil4 days Nil Nil Nil1 week Nil Nil Nil3 week Nil Nil Few12 week Few Nil Medium

Results and Discussion

Durability, adhesion and viscosity of the

matt finish paint (PBR) evaluated and

compared with the paint formulated with-

out rubber crumb (PB) and commercially

available emulsion paint (commercial).

Specimens for the tests prepared by coating

the paint samples on mild steel panels of

size 6 in� 4 in (BS specification).

Time periods used for various tests and

the observations during the tests are

summarised in Tables corresponding to

each test. The appearance (photographs) of

the samples before (initial) and after the

tests (final) are shown under respective

tests. Properties of the formulated paints

compared with a commercially available

paint.

Water Resistance Test

Water resistance tests conducted for

12 weeks. Initial (before the test) and final

(after 12 weeks) appearance of the surface

coatings are given in Figure 2. Observations

during the test period is summarised in

Table 3. PBR not showed any blister even

after 12 weeks (Figure 2 & Table 3) but PB

and commercially available paint showed


little blistering. This shows that PBR is

highly resistant to water. This is due to the

increase of hydrophobicity of paint film by

rubber crumb.

Salt Spray Test

Appearance of the samples before the test

and after 12 weeks is given in Figure 3.

Table 4 shows the blister formation on

various paint films during the test period.

PBR not affected by salt spray even after

12 weeks but PB and commercially avail-

able paint showed little attack by salt water.

Alkali Resistance Test

Resistance towards Na3PO4 at 75 8C,Na2CO3 at 65 8C and NaOH at 28 8Cevaluated as per the period specified in

ASTM D 714-56. Tables 5,6 and 7 describe

the observations during the test period.

Photographs of samples before the test


Figure 3.

Appearance of specimens before and after salt spray

test.

Table 4.Blister formation in salt spray test at 28 8C.


PB PBR Commercial

48 hrs Nil Nil Nil1 week Nil Nil Nil4 week Nil Nil Few12 week Few Nil Medium dense

Table 5.Blister formation in Na3PO4 resistance test (75 8C).


PB PBR Commercial

4 hrs Nil Nil Nil8 hrs Few Few Few16 hrs Medium Medium Dense24 hrs Dense Medium Peeled

Table 6.Blister formation in Na2CO3 resistance test (65 8C).


PB PBR Commercial

4 hrs Nil Nil Nil8 hrs Few Nil Few16 hrs Medium Few Dense24 hrs Dense Few Peeled

Table 7.Blister formation in NaOH resistance test (28 8C).


PB PBR Commercial

4 hrs Nil Few Nil8 hrs Medium Medium Dense16 hrs Dense Dense Peeled


Macromol. Symp. 2012, 315, 205–211 209

(initial appearance) and after the test (final

appearance, 24 h for Na3PO4, 24 h for

Na2CO3, & 16 h for NaOH) are shown in

Figure 4. The figure shows that commercial

sample easily attacked by alkalies and

peeled off from the coated panel. Sample

Figure 4.

Appearance of specimens before and after alkali

resistance test.


Figure 5.

Appearance of specimens before and after scotch test.

Table 9.Shear thinning index of specimens.

Sample Shear thinning index

PB 8.67PBR 7.84Commercial 5

Macromol. Symp. 2012, 315, 205–211210

PB showed dense blisters but PBR showed

very few. Presence of crumb rubber makes

PBr more alkali resistant.

Scotch Test

The cross cut adhesion test is carried out to

know the adhesion of paint films on the

substrate. Figure 5 shows the appearance of

samples before and after the test. Adhesion

rating assessed as per ASTM D3359-02 is

given in Table 8. PBR showed higher scotch

resistance compared to PB and commercial

sample. The presence of matting agent

(activated rubber crumb) may not allow the

scotch tape to adhere on the surface of

paint. This test shows that PBR can strongly

adhere to the substrate and the impurities

cannot adhere firmly on the surface of matt

finished paint film. This makes the cleaning

of paint surface easy.

Viscosity of Paint

Viscosity and shear thinning behaviour is

an important property of paint to measure

Table 8.Adhesion rating assessed by scotch test.

Sample name Classification % removal

PB 4B Less than 5%PBR 5B 0%Commercial 3B 5–15%


the ease of application. It depends on the

size and concentration of the colloidal

particles in paint. The viscosity of newly

formulated paint found to be independent

of the presence of activated rubber crumb,

since it uniformly distributed in the paint.

Shear thinning index of the specimens

(Table 9) and variation of viscosity with

shear rate (Figure 6) shows that all paints

are in the easy application range.

Durability tests such as water resistance,

salt spray resistance, and alkali resistance of

surface coatings showed that PBR is more

durable compared to other paints. Presence

of rubber crumb may actively resist the

attack of chemicals and climate conditions

due to the inherent resistance of rubber

crumb. It is due to the presence of ZnO and

cross-linked nature of rubber vulcani-

zate.[26–28]

Conclusion

A new matt finished paint formulated with

Vinyl acetate - Butylacrylate copolymer

using activated tyre crumb as matting

Figure 6.

Variation of viscosity with shear rate.


Macromol. Symp. 2012, 315, 205–211 211

agent. This paint has better water resis-

tance, alkali resistance and salt spray

resistance compared to latex paint &

commercial grade emulsion paint. It has

good adhesion towards the substrate and

viscosity is in the easy application range for

paint. Waste rubber crumb can be success-

fully utilised to make a low cost and eco-

friendly surface coating.

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activated rubber crumb in waterborn surface coating

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