Considerations for Developing 木器涂料

Wood has been used as a 建筑 material for thousands of years due to its availability, low weight to strength ratio and, in many applications, high aesthetic quality. 然而, as a 油漆able substrate, it also provides some unique challenges and considerations, as wood is a dynamic, porous (cellular structure) and hygroscopic material. A few considerations include:

  • Moisture content – kiln dried wood absorbs water until it reaches equilibrium with relative humidity. Moisture content can vary from about 6% to 30%.
  • Expansion and contraction -见表一
  • Age, wood cut geometry and type of wood – (e.g. hardwood or softwood etc.) – determines 油漆 receptivity (moderately aged wood > new wood or very old wood)

Table I – Percent Dimensional Change of Wood as Moisture Content Varies from 5 to 15%

wood涂料1

For a 10 cm thick wood section, a fluctuation in Relative Humidity of about 10% means a change in a tangential longitudinal wood piece of 3.5 mm (or 3,500 microns). 相应的, these relatively large dimensional changes produce cracks as the wood looses elasticity due to aging. Thus a properly designed wood 涂层 must have the requisite flexibility to accommodate these dimensional changes without cracking. Wood is comprised of about 75% cellulose and hemicellulose and 25% lignin, resins and low molecular weight phenolics. In exterior applications, wood is susceptible to degradation and subsequent erosion due to exposure to UV degradation, 氧气, moisture and biological activity. When exposed to the elements, the lower molecular weight materials will degrade to form water-soluble compounds that wash out whereas the more stable cellulosic molecules remain to form a white-grey color.

 

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无功 硅烷 for Enhancement of Coating Performance

无功 硅烷s (EU) can be used in multiple applications to enhance the performance of 涂料. They can improve adhesion to inorganic substrates, provide crosslinking, improve pigment dispersion, improve 疏水ity and scavenge moisture. A 硅烷 (EU) that contains at least one carbon silicon bond (CH3 – Si -) is called an 有机硅烷 (EU).无功 硅烷 is the term used to define compounds that have a trialkoxysilyl group and an alkyl group (R) containing a reactive constituent.

硅烷_SM2The trialkoxy 硅烷s that are discussed in this article are those that contain primarily trimethoxy (EU)组织, as these molecules are the most widely used to enhance 涂层 performance in a wide variety of applications, 如下:

  • Adhesion Promoter (EU)– 硅烷, when added to 油漆s, can enhance adhesion to inorganic surfaces including metals and glass.
  • 偶联剂 (EU) – 硅烷 are used for coupling organic polymers to inorganic materials, including pigments and 填料s.
  • Crosslinking Agent (EU) – Selective organofunctional alkoxy硅烷s can react with organic polymers to provide a trialkoxysilyl group into the polymer backbone. 反过来, the 硅烷 can then react with moisture to crosslink and form a three-dimensional siloxane cross-linked structure.
  • 分散剂 (EU) – Used to improve the 疏水ity of inorganic pigments, flow and the ability to be dispersed in organic polymers and solvents.
  • Moisture Scavenger (EU) – In moisture sensitive formulations, the three alkoxy硅烷 groups can scavenge water by reacting with moisture to form alcohol molecules.

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