Microfliuidics to measure wetting properties of untreated/chemically treated steel and wood strands substrates

传统上，甲醛基树脂用于制造工程木制品（EWP），但该行业正在转向使用聚合物二苯基甲烷二异氰酸酯（pMDI）结合树脂。这种转变既是由于使用甲醛的安全问题，也是由于使用pMDI的显著优势，包括：降低浓度和成本；快速固化;通过形成强化学键提高面板性能；增强了强度和抗水性。然而，由于其优越的粘合性能，pMDI的使用有一个缺点，这需要应用有效的脱模剂（RA）。RA防止生产板粘在压板/皮带上，导致停机时间，昂贵的清洁和生产损失。嘉德此前已开发了一系列Pressguard RA系列pMDI粘结复合木制品，并受到专利保护。虽然取得了成功，但最近的行业趋势，如压力机温度升高以及竞争激烈的市场压力，要求我们在这一领域重新开展研究工作，以重新获得失去的市场份额，并解决不断变化的压力机操作条件。高效RA的开发需要深入了解其物理特性以及与所涉及的固体基材（包括不锈钢/软钢和木丝）的润湿/粘合相互作用。这个联合项目的主要目标是使用微流控通道和实时高分辨率显微镜来识别和测量控制热金属板和pMDI树脂制造的复合木板之间粘附/释放的关键物理特性。实验方案包括测定pMDI树脂、水、硅油和专有脱模剂（RA）共混物的动态表面张力和动态接触角。微流体通道将被设计和制造，试图作为微模型来模拟木材多孔结构中液体的吸收。采用不同的涂覆剂改变通道的亲疏水性，系统研究基材润湿性对动态接触角和毛细流动的影响。

Traditionally, formaldehyde based resins were used for manufacturing of engineered wood products (EWP)however the industry is shifting to the use of polymeric diphenylmethane diisocyanate (pMDI) binding resins.This shift is due to both the safety concerns with the use of formaldehyde, but also due to the significantadvantages with the use of pMDI including: reduced concentration and cost; fast curing; increased panelperformance through the formation of strong chemical bonds; increased strength and water resistance.However, there is a drawback limiting the use of pMDI due to its superior adhesive properties which requiresthe application of effective release agents (RA). RA prevents the sticking of the produced boards to the pressplates/belts resulting in downtime, costly cleaning and production losses. Guardian has previously developed aseries of Pressguard RA for pMDI bonded composite wood products which are protected by patents. Whilesuccessful, recent industry trends such as increased press temperatures as well as competitive market pressurerequires that we renew our research efforts in this field to regain lost market share and address the changingpress operating conditions. Development of efficient RA requires in depth understanding of their physicalproperties and wetting/adhesive interactions with the involved solid substrates, including stainless/mild steeland wood strands. The main objective of this joint project is to use microfluidic channels along with real-timehigh resolution microscopy to identify and measure the key physical properties that govern the adhesion/releasebetween hot metal plate and composite wood panels manufactured with pMDI resins. The experimental schemeincludes determination of dynamic surface tension, dynamic contact angles of pMDI resins, water, silicone oiland proprietary release agent (RA) blends. Microfluidic channels will be designed and fabricated in an attemptto act as micromodels to mimic the absorption of liquids in the wood porous structure. Different coating agentswill be used to change hydrophilicity/hydrophobicity of the channels to systematically study the effects ofsubstrate wettability on dynamic contact angle and capillary flow.