木材塑膠再生複合材之潛變與耐候特性探討

Abstract

本試驗目的為探討長時間載重之下，不同塑膠基材（PP, polypropylene; RPP, recycled polypropylene）、不同塑膠與木粉比例（30/70, 50/50, 70/30）、不同載重水準（30%, 50%, 70%）以及不同的耐候條件（室外耐候5、9個月與加速耐候360, 1080, 2040 hr）對於混煉後射出成型的木材塑膠複合材的標準試片之潛變量、機械性質、明亮度與粗糙度的影響。 試驗結果顯示：在長時間的重複載重模式下，潛變量的總變化會隨著重複載重次數的增加而呈現對數趨勢上升，並且受材料中的黏彈性部份影響較大；在長時間載重至破壞的模式下，不同塑膠基材潛變量的變化有顯著差異，當塑膠基材與木粉比例為50/50時，強度皆能保持在700 kgf/cm2左右；不同塑膠木粉比例潛變量的變化會隨著木粉比例的增加，潛變撓曲會呈現下降的趨勢，強度則以木粉比例佔50%時能保有最高強度（708 kgf/cm2），而木粉比例佔70%時殘餘的強度最低（523 kgf/cm2）；不同載重水準潛變量的變化會隨著載重水準的增加，潛變撓曲會呈現上升的趨勢。 此外，耐候試驗對於木材塑膠複合材的性質影響包含：在室外耐候試驗及加速耐候試驗初期，明亮度皆有明顯的增加；試片之抗彎、抗拉強度皆會隨著木粉含量的增加，而降低其強度。在粗糙度的比較，試片在經過加速耐候試驗之後，其粗糙度皆會隨著加速耐候時間的增加，而呈現顯著的增加。

The purpose of this study is to discuss different factors of long-term loading, including different plastic bases (PP, polypropylene; RPP, recycled polypropylene), ratios of plastic/wood flour (30/70, 50/50, and 70/30), load levels (30%, 50%, and 70%), and conditions of weathering (5 and 9 months outdoor weathering; 360, 1080, and 2040 hours accelerated weathering), affect on creep deflections, mechanical properties, lightness, and roughness of wood plastic composites’ standard test specimens by injection machine. The results of the experiment showed: under the creep recovery model, creep and creep recovery increase along with the number of repeat loading times in fixed time, and present the logarithm relationships. Besides, the viscoelasticity of the material has much influence to the creep deflections. Under the creep rupture model, creep deflections have significant difference between different plastic bases. When the ratio of plastic/wood flour is 50/50, residual MOR can keep at about 700 kgf/cm2. The contents of wood flour have negative relationship with creep deflections. When the content of wood flour is 50%, residual MOR can keep at the highest about 708 kgf/cm2. And residual MOR keep at the lowest about 523 kgf/cm2 when the content of wood flour is 70%. The load level has positive relationship with creep deflections. In addition, the affections of weathering to the wood plastic composites’ properties showed: lightness increase obviously in the initial periods of out-door weathering and accelerated weathering. MOR and tensile strength have negative relationship with the contents of wood flour. Roughness have positive relationship with the time of accelerated weathering.