木材塑膠再生成形複合材的基本性質探討

Abstract

木材塑膠複合材料（Wood Plastic Composites,WPC）因其具有完全回收、良好強度與低吸水性等優點，在現今高油價的趨勢下，而成為備受矚目的環保材料，以本試驗所做出的WPC為例，固碳量在塑膠/木粉=1:1為68％，對於減碳有正面的效果。雖然WPC兼具塑膠與木材的優點，但複合材料也容易導致多元的變數，故本試驗探討不同塑膠基材、木粉種類與大小、塑膠基材/木粉比例、添加劑與製程等條件對WPC性質的影響，包含抗拉強度、抗彎強度、動態性質、吸濕澎潤性、電磁波屏蔽效應與微觀結構。 試驗結果顯示：塑膠基材與木粉比例以略近1:1的機械性質較好，其中塑膠基材因其流動性而影響試片的機械性質甚鉅，木粉選擇以混合樹種和小於180 μm徑級為佳，若木粉能先以NaOH處理，則對WPC性質有極顯著提升；比較不同添加劑含量，MAPP以3 ％、4.5 ％有良好的強度表現，製程上而言，以射出成形的試片較押出成形與熱壓成形優良；此外，50%含木炭率之4.3 mm厚WPC具有約22dB的平均電磁波遮蔽效果，1.72 cm厚WPC具有約54dB電磁波的遮蔽效果，也就是等級2與3的遮蔽量。

Wood Plastic Composites (WPC) is one of highly attracting materials because of its recycling resource, great mechanical strength and low water absorption. Considering the trend of high fuel price, WPC, one of green materials, becomes more and more important. For instance, WPC of 47% wood can fix 68% carbon so WPC has positive effect of carbon conservation. The character of WPC not only combines the advantages from wood and plastic but also brings complex and various factors. So the purpose of the study was to investigate the effects of plastic based, wood based, plastic/wood ratio, additives and manufacturing process on the tension strength, modulus of rupture, dynamic mechanical property, water absorption, E.S.E (Electromagnetic Shielding Efficiency) and microstructure of WPC. The results showed that in the based material part, with the ratio of plastic/wood about 1, WPC had the greater mechanical properties. The rheology of plastic based played an important rule. The wood flour having smaller size than 180μm and mixed species had better properties. If the wood flour was treated 8%NaOH before manufacturing process, WPC had obviously improved properties. In the manufacturing process part, WPC of injection process had superior properties to extrusion and hot pressing process. Besides, in the additives part, comparing different weight concentration of MAPP, WPC of 3% and 4.5 % had greater properties. Adding 50% the charcoal of 1000℃ Taiwan Paulownia could give WPC a great E.S.E.. When the thickness was 4.3 mm WPC had about 22dB and when the thickness was 1.72 cm, WPC had about 58 dB, respectively was 2 and 3 shielding level.