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Product development for green productivity a case study

Development of algae resistant surface coating for building facades in the humid tropics

2nd APO World Conference on GP

Manila 9-12 Dec 2002

LOH Wah Sing

Institute of High Performance Computing

Singapore

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Outline of presentation

• Paint failure on painted building facades with respect to microbial fouling – site survey

- pattern of fouling- algae vs. fungus

• Causes of paint failure• Climate of tropics vs. sub-tropics• New paint quality attributes + environmental

consideration• Screening of algal resistance in field• Full field test• New product standardisation• Implication of project to green productivity

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About Singapore

• Urban island nation near the equator• Area : 660 sq km• Population : 4 million; 6000 people/sq km• 860,000 public apartments (Ave 70

sqm/unit) housing 3 million population• Mass construction of public housing by

Housing and Development Board started from early 1960s

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General microbial fouling on building facades

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Finishing on building facades

• Paint finish widely used on residential buildings• Problem of unsightly disfigurement of paint by

microbial fouling became serious from 1970s • Microbial fouling on facades was caused by

algae, not by fungus – latter advocated by paint manufacturers

• Main fouling algal species : Trentepohlia odorata• Conventional emulsion paint short lived – 3 yrs• Frequent repainting caused social disruption for

urban living• HDB tried solvent-based paint for repainting fobs

from early 1980s – emission of 900 tons of solvent per year

7Fouling on porous surface (right)

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9Microbial growth along cracks

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Algae - Growth on both inorganic and organic substrate- Photosynthesis capability, presence of chlorophyll

Fungus- Live on organic substrate as source of food

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Causes of paint failure

• Climatic stress – temperature, humidity, rainfall, UV radiation

• Detailing of buildings – consider tropical features?• Quality of substrate – porosity• Quality of paint• Painting specification• Painting workmanship

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Climate - Singapore vs. Miami

Singapore: 103 oE, 1 oNMiami : 80 oW, 26 oN

Temperature, oC Minimum Maximum Mean

1 Q

S’pore 23 31 26

Miami 14 26 20

2 Q

S’pore 24 31 27

Miami 21 32 25

3 Q

S’pore 24 31 27

Miami 24 34 28

4 Q

S’pore 24 30 26

Miami 18 28 23

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Climate - Singapore vs. Miami

Singapore: 103 oE, 1 oNMiami : 80 oW, 26 oN

Humidity, % Minimum Maximum Mean

1 Q

S’pore 63 96 84

Miami 55 95 75

2 Q

S’pore 64 97 84

Miami 52 92 72

3 Q

S’pore 64 96 83

Miami 55 90 73

4 Q

S’pore 66 97 86

Miami 57 94 76

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Climate - Singapore vs. Miami

Singapore: 103 oE, 1 oNMiami : 80 oW, 26 oN

Rainfall, mm Singapore Miami

1 Q 599 289

2 Q 529 605

3 Q 513 767

4 Q 732 376

Total 2,373 2,037

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Climate – solar radiation

• A Davis & D Sims, “Weathering of polymers” (1983), Applied Science Publishers

• L.R. Koller, “Ultraviolet radiation”(1965), Wiley

Total solar radiation shows maximum intensity at latitude 15 deg Solar UV radiation shows

* max intensity at equator, decreases with increasing latitude

* max intensity at noon of day

* max intensity in summer of year

Combination of UV and moisture (humidity) accelerates degradation (S.P. Pappas, “Weathering of coatings – formulation and evaluation” (1989), Prog in Organic Coatings, vol 17, No.2, pg89)

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Product development – attributes considered

• Cost effectiveness• Service life of 6 years or more under humid tropical climate• Environmental consideration – water-based paint to be

developed• Rule 66, smog, VOCs, fire & health hazards etc• Formulation for weather durability – binder/pigment ratio, type of

binder, biocides, additives

* High pigmentation level causes chalking/erosion

* Binder susceptible to moisture and alkali will not last

* Hygroscopic additives will affect moisture sensitivity of paint

* Low pigmentation characterised by appearance of sheen on

dry paint surface

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Weathering test – crack-present and crack-free quality

20Screening test against algal resistance at field

21Screening against algal resistance at field

22Field test on 8 buildings for 8 yrs; Example – Changi Telecoms Building

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Field test – algal growth on glass window due to

condensation

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Product standardisation – for purchasing specification

S.S. 345

1990

S.S. 150

1976

Gloss, 85 deg 15 – 50 Max 20

Appearance Sheen Matt

Wet scrub resistance, No. cycles passed

3,000 1,500

Accelerated weathering, hours

1,000 500

Algal resistance Pass test NR

Fungal resistance NR Pass test

NR: not required

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Life cycle costing

Tender option A B B/A

No. blocks for repainting 455 455

Types of paint S.S. 150 S.S 345

Total tender price S$29.2m S$38.2m 1.3

Warranty period 3 years 6 years 2.0

Expected service life of

paintwork

4 years 7 years 1.75

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Impacts and benefits

• Product commercialisation

* 11(14) paint manufacturers in S’pore

* Adopted in Brunei and Hong Kong

• Changing marketing concept of paint

* Partnership of paint manufacturers and painters

* Sell paint (semi-product) sell paintwork (finished product)

• Cost effectiveness

* Extended service life longer repainting cycle

* Life cycle costing savings of S$2 million/year

• Green productivity

* Waste reduction savings of labour (paint production and painting),

scaffolding, water, paint materials, logistics and administration….

* VOCs elimination savings of 900 tons solvent/year

* Reduced ESH impact

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Thank you