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），然而工业正在转向使用聚合二苯基甲烷二异氰酸酯（pMDI）粘合树脂。这种转变是由于使用甲醛的安全性问题，但也由于使用pMDI的显著优点，包括：降低浓度和成本;快速固化;通过形成强的化学键来提高板的性能;提高强度和防水性。然而，由于其上级的粘合性能，需要施加有效的脱模剂（RA），因此存在限制pMDI使用的缺点。RA可防止生产的板材粘在压板/传送带上，从而导致停机、昂贵的清洁和生产损失。Guardian以前开发了一系列Pressguard RA，用于pMDI粘合复合木材产品，这些产品受专利保护。虽然成功，最近的行业趋势，如增加新闻温度以及竞争激烈的市场压力，要求我们重新在这一领域的研究工作，以夺回失去的市场份额，并解决不断变化的新闻工作条件。高效RA的发展需要深入了解其物理特性和润湿/粘合剂与所涉及的固体基质，包括不锈钢/轻度钢和木材股的相互作用。该联合项目的主要目标是使用微流体通道沿着与实时高分辨率显微镜来识别和测量控制热金属板和用pMDI树脂制造的复合木板之间的粘附/释放的关键物理特性。实验方案包括测定pMDI树脂、水、硅油和专利脱模剂（RA）共混物的动态表面张力、动态接触角。微流体通道将被设计和制造在一个实验室作为微观模型，以模仿木材多孔结构中的液体吸收。采用不同的涂层剂来改变通道的亲/疏水性，系统地研究了基底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.