不同NCO含量的反應型聚胺酯熱熔膠特性研究與探討

The Characteristics and Studies on the PU Reactive Hot Melt Adhesives with Different NCO Contents

反應型聚胺酯熱熔膠 （polyurethane reactive hot melt adhesives, PUR） 為一種環保、無溶劑的高性能接著劑。本研究以4,4'-二苯基甲烷二異氰酸酯（pure-MDI）、聚酯多元醇 （PHA） 及聚醚多元醇 （PPG） 為原料，並固定PHA與PPG 之間的比例，藉由pure-MDI 的不同添加量製備出不同NCO 含量之PUR，並對下列特性進行比較與探討：（1） 以ATR-FTIR 觀察PUR 預聚物之熟化程度，並量測其熔融黏度、開放時間和固著時間；（2） 以DSC 觀察PUR 熟化後的玻璃轉移溫度與熱焓值；（3） 不同NCO 含量之PUR 以PC 試片進行貼合，探討其於4 小時及168 小時的搭接強度 （lap shear strength） 及破壞模式。研究結果顯示PUR 預聚物隨著NCO 含量提高，則熔融黏度降低、可操作時間延長。由DSC 得知其在不同NCO 含量的PUR 於熟化後的熱焓值比較依序為PUR42 > PUR30 > PUR10 > PUR17 ≈ PUR23。以拉力試驗機檢測PUR 薄膜，得知其隨著NCO 含量的提高，當完全熟化後的薄膜，其抗張強度也隨之增加；由接著強度測試的結果得知，當NCO 含量增加，可提高其微相分離的程度，並阻礙軟段的聚集，致使PUR 的初期強度較低，並且以PUR42 的膠膜有較高的內聚力，因此在搭接強度測試有較大的界面破壞。

Polyurethane reactive hot melt adhesives (PUR) are isocyanate-cappedprepolymers prepared from polyester and/or polyether glycols and adiisocyanate monomers or polyisocyanate. The different NCO content ofPUR have been synthesized by polyhexanediol adipate (PHA), polypropyleneglycols (PPG), and 4,4'-methylene diphenyl diisocyanate (pure-MDI)as the main ingredient. The PUR prepolymers are NCO-terminated, andthey will be cured in the presence of moisture to generate highly crosslinkedstructure.The PUR with different isocyanate (NCO) content was studied onrheology, thermal and mechanical properties of PUR film. The effects ofNCO/OH molar ratio on the morphology and physical properties of PURwere investigated by attenuated total reflectance Fourier transform infraredspectroscopy (ATR-FTIR), differential scanning calorimetry (DSC) anduniversal testing machine. The results showed that the PUR had a highdegree of micro phase separation and the hydrogen-bonded urea signalincreases significantly under the higher NCO content. As the NCO contentincrease, the degree of hydrogen bonding of the hard segments and theglass transition temperature (Tg) increase. PUR prepolymer with highercrystalline content showed better green strength and the slower adhesionrate. Because the higher degree of crosslinking can prevent moisturediffusion into the PUR film, so leading to incomplete curing and hinder thecrystalline behavior of the soft segment. It hence causes a lower initialadhesive strength.