聚乙烯醇添加量及添加時機對間苯二酚──甲醛樹脂性質之影響

The influence of the timing and amount of polyvinyl alcohol added on the properties of resorcinol-formaldehyde resin

間苯二酚甲醛樹脂（Resorcinol-formaldehyde resin; RF）為木材工業最重要的膠合劑之一，主要應用於常溫硬化的集成材製造。本研究在添加福馬林之前（RF-A）、添加福馬林之後（RF-B）及反應終止前（RF-C）導入聚乙烯醇（Polyvinyl alcohol; PVA）進行RF樹脂合成反應，探討PVA添加時機及添加量對所合成RF樹脂性質及其膠合性能之影響。由試驗結果得知，RF樹脂的粘度隨PVA添加量增加而提高，添加時機之影響則不明顯。FTIR（Fourier transform infrared spectroscopy）分析顯示RF樹脂與PVA樹脂並未發生化學反應，兩者之間為物理的摻合。添加PVA可縮短RF樹脂的膠化時間，然其硬化RF樹脂的彎曲強度及破壞撓曲量降低，但熱抵抗性提高。合成時先添加PVA再加入福馬林進行反應（RF-A系列）可提高RF樹脂的膠合強度，其中並以RF-A-4有最大的膠合強度。

Resorcinol-formaldehyde resin (RF) is one of the most important adhesives in the wood industry. It is mainly used in the manufacture of laminated wood that sets at room temperature. In this study, polyvinyl alcohol (PVA) was added before adding formalin (RF-A), after adding formalin (RF-B) and at the time of reaction termination (RF-C) of the RF resin synthesis. The influence of the timing and amount of PVA addition on the properties and bonding performance of RF resin were investigated. The results showed that the viscosity of the RF resin increased with the increase of the amount of PVA added, and the effect of the timing of the addition of formalin was not obvious. FTIR (Fourier transform infrared spectroscopy) analysis showed that there was only physical blending between RF resin and PVA without chemical reaction. Addition of PVA shorten the gel time of the RF resin, but the bending strength and fracture deflection of the cured resin were reduced, while the heat resistance was improved. During synthesis, adding PVA first, followed by adding formalin for reaction (RF-A series) increased the bonding strength of RF resin. Among the RF-A series, RF-A-4 exhibited the highest bonding strength.