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Growth continues despite market scares
FOCUS ON P O W D E R C O AT I N G S A MONTHLY REPORT FROM SID HARRIS
GROWTH CONTINUES DESPITE MARKET SCARES
SEPTEMBER 2011
In this issue
TECHNICAL
2-3
Powder coating SMC by the mould technique Factors affecting the scratch performance of powder coatings
INDUSTRY NEWS
3-7
DSM takes control of Taiwanese company AGI AkzoNobel India: results for 1Q 2011-2012 AkzoNobel expands paint and coating activities AkzoNobel opens more RD&I facilities
LITERATURE
7
Fillers for paints – 2nd edition
NEW PRODUCTS
7
Cytec patents radiation curable low gloss powder coating
MARKETS
7-8
Russian output of polymer-based coatings reaches 448,000 tonnes in 1H 2011
EVENTS
AN INTERNATIONAL NEWSLETTER MONITORING TECHNICAL AND COMMERCIAL DEVELOPMENTS IN POWDER COATINGS ISSN 1364–5439
8
At this quiet time of the year there is little apparent improvement in the perennial problems facing the coatings industry – ever-increasing energy and raw material prices. For some reason these are not matters that concern global investors. It seems that the investors who support our businesses and economies are more alarmed by their perception that previously strong economies are heading towards another recession, and they are experiencing a knee-jerk reaction by seeking to off-load their investments. There is no cause for concern for the global markets are stable at present, with positive signs of growth in most areas of manufacturing industry. If evidence is required, the industry news section in this issue details the increased annual returns and expansion plans of the major coatings producers. This is the true indicator of industrial growth and it is significant that powder coatings are leading the way to recovery. An interesting paper presented at the recent European Coatings Congress in March describes the updating of an established powder coating application method to meet the more demanding needs of the automotive industry. Powder in mould-coating of SMC profiles is considered by researchers at DSM to be the most effective method for priming the surface of automotive
components and they present a comprehensive development programme to justify their conclusions. I am, however, concerned that the powder producer is expected to hot melt compound formulations containing a mixture of peroxide compounds. In addition the total processing seems to be a time-consuming operation, which will not meet the speed required on car production lines. Perhaps a better alternative would be to spray the warm SMC components straight after moulding with a UV curable powder coating and cure the coating within seconds. It would give greater savings in powder reclaim, better control over film thickness and faster turnaround of coated components. Professor Barletta continues to evaluate the performance of powder coating systems and suggest ways in which commercial products could be improved. His latest published work (see p2-3) compares the scratch resistance of a thermoset powder to that of a thermoplastic powder when both are subjected to different application and curing techniques. While the effect of curing thermoset powders by hot dipping fluidized bed is entirely predictable, this programme did reveal some unexpected changes in crystallinity content when the thermoplastic was given the slower and more even heat intake of a convection oven. The
POWDER COATINGS POWDER COATINGS POWDER COATINGS POWDER COATINGS
FOCUS performance of the thermoset in HD application was reminiscent of the problems experienced by pipeline coaters in the early years of fusion bonded epoxy pipe protection. The uneven heat distribution often resulted in a “curates egg” variation in cure throughout the film with consequent embrittlement and loss of adhesion to the metal substrate. Sid Harris
TECHNICAL Powder coating SMC by the mould technique Glass reinforced sheet moulding compound is a thermoset composite comprising well dispersed long glass fibres in an unsaturated polyester resin. The high structural strength of SMC parts, coupled with their lower weight compared to equivalent steel automotive components, makes them attractive to car manufacturers seeking to improve fuel efficiency. The current practice for coating SMC is a multi-layer liquid painting process using predominantly solvent based systems, which has a high reject rate of 20-25%. Powder coating would be a more attractive alternative since the overspray can be recycled. The main problem is the microporous structure of SMC, which is engineered by incorporating additives to prevent shrinkage during the chemical curing of SMC. The cured compound contains moisture and entrapped air causing “paint popping” and surface blistering during the powder curing process. Some modifications have been made to enable powder to be applied shortly after the moulding process but this still causes some problems. Powder in-mould coating (PIMC) could be the answer. It has been successfully applied to sanitary items, but the demands 2
ON
POWDER
of the automotive industry require higher standards of durability and increased processing speeds. A special type of powder coating has been applied successfully by PIMC to components for trucks and agricultural machinery since the PIMC effectively prevents moisture popping by combining with the SMC substrate. A paper presented at the recent European Coatings Congress examines the potential for using PIMC in interior automotive applications. The integrated process for combining PIMC and SMC is performed in a specially designed metal moulding tool with an upper and a lower mould segment. The materials are pressed at a constant temperature between 130-155°C. In the PIMC process the interior of both mould segments is covered with a layer of powder coating before the SMC compound is added. The combination of heat and high pressure cures and bonds the coating to the SMC. A release compound added to the powder coating (zinc stearate) assists an easy and quick mould release. The powder coating is based on an unsaturated polyester resin binder with a crosslinker that reacts by radical initiated polymerization in three stages: initiation, propagation and termination. In the first stage of initiation the organic peroxide curing agent decomposes to create oxygenated radicals, which propagate the reaction of the double bonds in the polyester chain. Termination can occur between the initiating radicals to form a stable covalent bond or, alternatively by oxygen inhibition. This effectively terminates the crosslinking and stabilizes the coating film. In their laboratory tests the authors used a binder system comprising an unsaturated polyester mixed with a semicrystalline vinylether urethane and a mixture of organic peroxides. All formulations were pigmented with 22 weight percent of titanium
C O AT I N G S dioxide. Full formulations are detailed in the paper. An SMC formulation is also fully described. Tests on prepared specimens of each PIMC/SMC combination included: rheological measurements, abrasion resistance, flexibility testing, adhesion and hardness. A smell test similar to the VDA 270 method was also carried out on each specimen. This latter test demonstrated the efficiency of the powder coating in reducing the strong odour of volatiles emitted by the SMC. Four further formulations were prepared to examine the effect of varying the resin to co-resin ratios and their influence on coating properties and cure behaviour. The semi-crystalline co-resin has a strong influence on melting properties by lowering the melt viscosity, which increases the speed of cure. The influence of varying the amount of peroxide was also investigated. In conclusion, it was also found that different ratios of resin to coresin can alter the mechanical coating properties, and varying the type of commercially available peroxide influences melt viscosity and the curing reaction. The barrier properties of the PIMC make it a good primer for subsequent coating with liquid paints. While this work concentrated on SMC, the authors consider that the same PIMC could be used for other moulding applications. Paper entitled “Powder in Mould Coating as a Superior Finishing Solution for SMC in Automotive Applications” by researchers at DSM BV, presented at European Coatings Congress held in Nuremberg on 28-30 Mar 2011. Copies of the Congress papers are available in CD format from the organizers, Vincentz Network. Website: www.europeancoatings-show.com
Factors affecting the scratch performance of powder coatings Another work programme by Professor Barletta and his dedicated team of powder enthusiasts examines scratch SEPTEMBER 2011
GROWTH CONTINUES DESPITE MARKET SCARES
SEPTEMBER 2011
In this issue
TECHNICAL
2-3
Powder coating SMC by the mould technique Factors affecting the scratch performance of powder coatings
INDUSTRY NEWS
3-7
DSM takes control of Taiwanese company AGI AkzoNobel India: results for 1Q 2011-2012 AkzoNobel expands paint and coating activities AkzoNobel opens more RD&I facilities
LITERATURE
7
Fillers for paints – 2nd edition
NEW PRODUCTS
7
Cytec patents radiation curable low gloss powder coating
MARKETS
7-8
Russian output of polymer-based coatings reaches 448,000 tonnes in 1H 2011
EVENTS
AN INTERNATIONAL NEWSLETTER MONITORING TECHNICAL AND COMMERCIAL DEVELOPMENTS IN POWDER COATINGS ISSN 1364–5439
8
At this quiet time of the year there is little apparent improvement in the perennial problems facing the coatings industry – ever-increasing energy and raw material prices. For some reason these are not matters that concern global investors. It seems that the investors who support our businesses and economies are more alarmed by their perception that previously strong economies are heading towards another recession, and they are experiencing a knee-jerk reaction by seeking to off-load their investments. There is no cause for concern for the global markets are stable at present, with positive signs of growth in most areas of manufacturing industry. If evidence is required, the industry news section in this issue details the increased annual returns and expansion plans of the major coatings producers. This is the true indicator of industrial growth and it is significant that powder coatings are leading the way to recovery. An interesting paper presented at the recent European Coatings Congress in March describes the updating of an established powder coating application method to meet the more demanding needs of the automotive industry. Powder in mould-coating of SMC profiles is considered by researchers at DSM to be the most effective method for priming the surface of automotive
components and they present a comprehensive development programme to justify their conclusions. I am, however, concerned that the powder producer is expected to hot melt compound formulations containing a mixture of peroxide compounds. In addition the total processing seems to be a time-consuming operation, which will not meet the speed required on car production lines. Perhaps a better alternative would be to spray the warm SMC components straight after moulding with a UV curable powder coating and cure the coating within seconds. It would give greater savings in powder reclaim, better control over film thickness and faster turnaround of coated components. Professor Barletta continues to evaluate the performance of powder coating systems and suggest ways in which commercial products could be improved. His latest published work (see p2-3) compares the scratch resistance of a thermoset powder to that of a thermoplastic powder when both are subjected to different application and curing techniques. While the effect of curing thermoset powders by hot dipping fluidized bed is entirely predictable, this programme did reveal some unexpected changes in crystallinity content when the thermoplastic was given the slower and more even heat intake of a convection oven. The
POWDER COATINGS POWDER COATINGS POWDER COATINGS POWDER COATINGS
FOCUS performance of the thermoset in HD application was reminiscent of the problems experienced by pipeline coaters in the early years of fusion bonded epoxy pipe protection. The uneven heat distribution often resulted in a “curates egg” variation in cure throughout the film with consequent embrittlement and loss of adhesion to the metal substrate. Sid Harris
TECHNICAL Powder coating SMC by the mould technique Glass reinforced sheet moulding compound is a thermoset composite comprising well dispersed long glass fibres in an unsaturated polyester resin. The high structural strength of SMC parts, coupled with their lower weight compared to equivalent steel automotive components, makes them attractive to car manufacturers seeking to improve fuel efficiency. The current practice for coating SMC is a multi-layer liquid painting process using predominantly solvent based systems, which has a high reject rate of 20-25%. Powder coating would be a more attractive alternative since the overspray can be recycled. The main problem is the microporous structure of SMC, which is engineered by incorporating additives to prevent shrinkage during the chemical curing of SMC. The cured compound contains moisture and entrapped air causing “paint popping” and surface blistering during the powder curing process. Some modifications have been made to enable powder to be applied shortly after the moulding process but this still causes some problems. Powder in-mould coating (PIMC) could be the answer. It has been successfully applied to sanitary items, but the demands 2
ON
POWDER
of the automotive industry require higher standards of durability and increased processing speeds. A special type of powder coating has been applied successfully by PIMC to components for trucks and agricultural machinery since the PIMC effectively prevents moisture popping by combining with the SMC substrate. A paper presented at the recent European Coatings Congress examines the potential for using PIMC in interior automotive applications. The integrated process for combining PIMC and SMC is performed in a specially designed metal moulding tool with an upper and a lower mould segment. The materials are pressed at a constant temperature between 130-155°C. In the PIMC process the interior of both mould segments is covered with a layer of powder coating before the SMC compound is added. The combination of heat and high pressure cures and bonds the coating to the SMC. A release compound added to the powder coating (zinc stearate) assists an easy and quick mould release. The powder coating is based on an unsaturated polyester resin binder with a crosslinker that reacts by radical initiated polymerization in three stages: initiation, propagation and termination. In the first stage of initiation the organic peroxide curing agent decomposes to create oxygenated radicals, which propagate the reaction of the double bonds in the polyester chain. Termination can occur between the initiating radicals to form a stable covalent bond or, alternatively by oxygen inhibition. This effectively terminates the crosslinking and stabilizes the coating film. In their laboratory tests the authors used a binder system comprising an unsaturated polyester mixed with a semicrystalline vinylether urethane and a mixture of organic peroxides. All formulations were pigmented with 22 weight percent of titanium
C O AT I N G S dioxide. Full formulations are detailed in the paper. An SMC formulation is also fully described. Tests on prepared specimens of each PIMC/SMC combination included: rheological measurements, abrasion resistance, flexibility testing, adhesion and hardness. A smell test similar to the VDA 270 method was also carried out on each specimen. This latter test demonstrated the efficiency of the powder coating in reducing the strong odour of volatiles emitted by the SMC. Four further formulations were prepared to examine the effect of varying the resin to co-resin ratios and their influence on coating properties and cure behaviour. The semi-crystalline co-resin has a strong influence on melting properties by lowering the melt viscosity, which increases the speed of cure. The influence of varying the amount of peroxide was also investigated. In conclusion, it was also found that different ratios of resin to coresin can alter the mechanical coating properties, and varying the type of commercially available peroxide influences melt viscosity and the curing reaction. The barrier properties of the PIMC make it a good primer for subsequent coating with liquid paints. While this work concentrated on SMC, the authors consider that the same PIMC could be used for other moulding applications. Paper entitled “Powder in Mould Coating as a Superior Finishing Solution for SMC in Automotive Applications” by researchers at DSM BV, presented at European Coatings Congress held in Nuremberg on 28-30 Mar 2011. Copies of the Congress papers are available in CD format from the organizers, Vincentz Network. Website: www.europeancoatings-show.com
Factors affecting the scratch performance of powder coatings Another work programme by Professor Barletta and his dedicated team of powder enthusiasts examines scratch SEPTEMBER 2011