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Effects Of Microorganisms On Composites

Jun 24, 2017

The higher the content of wood, the faster the microbial degradation rate; the higher the water content, the faster the microbial degradation rate; the greater the content of biological antimicrobial agent, the slower the degradation rate of microorganisms.

Wood - plastic composite materials in the mineral play a shielding role, to prevent the microbial cellulose hydrolase contact with cellulose fibers. The higher the density of the composite material (the smaller the void), the smaller the water absorption, the lower the microbial degradation probability of the composite material. The use of antioxidants or the use of exhaust extruders can achieve higher density. Another way to increase the density is to slow down the extrusion speed, but this is clearly uneconomical.


The effect of microbes on wood-plastic composites has three "levels". The first stage, when the mold in the plating plate surface to form colored colored spots but did not degrade the material, the plate still maintain a good structure. In this case, the mold by dust, air pollen and other particles to survive. The second level, mold and other fungi significantly engulfed some of the components of the composite material as a nutrient, vitamins and so on. The third level, when the fungus specifically, quickly eroded the wood / cellulose in the composite material, causing mechanical properties of the material decreased. These fungi are called rot fungi cellulolytic bacteria.

Since many fungi only cause discoloration of wood, they are classified as mold or wood chromophores, rather than wood degradation fungi. Molds generally do not reduce the strength of cellulose or composite pairs. But the growth of mold and rot fungi the same conditions, the emergence of mold can be seen as a potential decay of a signal. In addition, many molds can cause allergies and are therefore harmful to health.


There are three types of microorganisms that can pollute, erode and degrade wood, plastic and WPC materials, which are fungi, bacteria and algae. Fungi are often referred to as mold, specifically degrading lignin called wood rot fungi (and mushroom), or divided into brown rot fungi and white rot fungi. Fungi are aerobic microorganisms, and their growth requires oxygen, which is particularly active in a temperature environment of about 30 ° C to about 40 ° C. They are active in the water, more than 85% of the temperature conditions are more active, like weak acid environment, generally dependent on sporulation.


Bacterial metabolites often cause the surface of the composite to be contaminated. Bacteria through the split propagation, only in the absence of things when its fast unrestricted breeding was interrupted. They often need more water for growth and metabolism. Many species of bacteria can live at higher temperatures (hi temperature bacteria).


Unlike fungi, algae represent microbes that promote photosynthesis and require light, favorite neutral pH environment.