EC Show Preview 2015 Seite 22

Hinweis: Dies ist eine maschinenlesbare No-Flash Ansicht.
Klicken Sie hier um zur Online-Version zu gelangen.

Inhalt

Focus Challenges are alleviated Interest in all aspects of wood coatings Prof Voytek Gutowski Chief Research Scientist at CSIRO is interested in all aspects of wood coatings powder UV curing and waterbornes He is currently researching ad hesion to wood surfaces  What is the most in teresting development for wood coatings Prof Voytek Gutowski The most interesting are ze ro waste zero VOC coatings waterborne 1 component UV curable polyurethane dis persions and powder coat ings Both offer outstanding coating performance a tough scratch resistant sur face 10 15 year durability overspray recovery and no pot life issues Powder coating a dry sol vents process provides elec trostatically assisted coating transfer with 95 efficiency overspray recovery and zero solids waste or VOC emis sions The powder is baked via low heat curing that does not alter wood properties UV curable waterborne PUDs 30 40 solids are rapidly gaining market share due to ultra fast low energy UV curing Multiple coats physi cally dried by water flash off facilitate fast product handling before final coating cure in the factory or on site Sunshine cure coatings for outdoor applications that are cured by solar UV are anoth er exciting development  You recently worked on adhesion issues on wood What is the biggest chal lenge there Gutowski One of the big gest challenges of improv ing adhesion to wood and to hardwoods in particular is their complex randomly variable and dynamic bulk and surface chemistry in conjunction with a high con tent of low molecular polar phenolics and non polar lipophilic compounds ex tractives and high timber density When the wood is sanded machined or dried all extractives migrate Prof Voytek Gutowski CSIRO to the surface Lipophilic extractives free and esteri fied fatty acids and sterols lower the surface polarity reducing wood wettability by waterborne coatings The polar compounds e g tan nins other phenolics and water soluble carbohydrates diffuse to the surface during wood drying Both types being unattached to the lignocellulosic wood matrix create a weak boundary layer over the surface adversely affecting coating adhesion All these contribute to poor performance and deteriora tion in the appearance of wood products that rely on coating adhesion which is additionally hindered by variable wood structure Of particular concern is the poor durability of wood on exposure to solar UV due to rapid photo chemical de composition of lignin and the adverse influence of environ mental stresses on adhesion of paint to wood through UV exposure which dam ages the wood surface and subsurface zone due to UV penetration to a depth of 100 150μm that reduces wood strength by 50 Progressive loss of the integ rity of the uppermost wood layers due to lignin decom position exfoliation of lignin fibrils and cell structure col lapse  Even 1 week s exposure to UV accelerates paint peel off because the paint is then applied to a wood surface containing decom posed detachable lignin  Cyclic interfacial stresses paint timber contact zone due to temperature and moisture fluctuations These challenges are al leviated by multifunctional interphases that we have de veloped in our labs and that deliver 1 Excellent adhesion to wood surfaces 2 Interfacial zone tough ness and durability due to the formation of gradient interphase structure that minimises damaging mois ture and interfacial stress effects 3 Improved UV resistance of the wood surface These developments are expected to alleviate the key reasons for users perception that wood product have ex cessive maintenance needs and require repairs and re painting every 4 6 years This in turn will restore the competitiveness of exterior wood products windows doors sidings railings etc versus non wood alterna tives made of plastics com posites or metals  UV and waterborne technologies are both well established for wood Will in future just one technology survive or both Gutowski Such a hybrid technology is already avail able in the form of one com ponent UV curable PUDs Further modifications of PUD coatings by acrylics will fur ther improve the outstanding attributes of this technology Global regulations and consumer demands are stimulating the rapid growth of clean coatings such as waterborne powder and ra diation cure including UV In 2013 waterborne coatings were the clear market leader with a 52 share whilst powder coatings radiation cure and other 100 solids liquid coatings accounted for a further 7 by volume of the market xz Shamrock RecyclesTM ISO 9001 2008 CERTIFIED FACILITIES Newark NJ Henderson KY Tianjin China Tongeren Belgium sales shamrocktechnologies com www shamrocktechnologies com Particle Innovation Surface Solutions Particle Innovation Surface Solutions Hall 1 Stand 237 Amazing is PTFE PTFE is an amazing material When polymerized in pure water it is used to make machined or molded parts Electrical insulation and waterproof clothing are made from PTFE polymerized with a wetting agent Shamrock produces micropowders made from both raw materials and from modified grades of these We continue to develop PTFE micropowders for new applications Let s talk in Nuremberg about what PTFE can do for you ShamrockMicrographTree4 indd 1 11 18 14 11 18 AM www european coatings show com 22


Vorschau EC Show Preview 2015 Seite 22