Bonding properties and crystallization kinetics of thermoplastic polyurethane adhesive

ABSTRACT The advantages of heterophasic thermoplastic polyurethanes (TPUs), such as their phase behavior and mechanical properties, make these materials an important class of adhesives. Whereas the amorphous phase contributes to good adhesion properties, the crystalline phase is responsible for the cohesive force of TPU adhesives. This work investigates the performance of a polyester based TPU and its potential for being applied as adhesive in the shoe industry. The TPU was formulated with three different additives. The crystallization kinetics of the TPU was evaluated by Differential Scanning Calorimetry and the Avrami equation was used to assess the influence of the additives on the geometry of crystal growth and nucleation conditions. It was found that the additives had no effect on the nucleation process, whereas the polymer chains had reduced mobility, mainly in the TPU comprising polyisocyanate ε-caprolactam. The best T-peel strength on a poly(vinyl chloride) (PVC) substrate was determined for the TPU with polycarbodiimide, which improved the adhesive bonding from 3.23 N/mm to 3.32 N/mm.

摘要：多相热塑性聚氨酯（TPUs）凭借其相行为与力学性能等优势，成为一类重要的胶粘剂材料。无定形相可赋予材料优异的粘附性能，而结晶相则决定了TPU胶粘剂的内聚强度。本工作研究了一种聚酯基TPU的性能及其在制鞋业中作为胶粘剂的应用潜力，该TPU复配了三种不同的添加剂。研究采用差示扫描量热法（Differential Scanning Calorimetry）对TPU的结晶动力学进行了表征，并借助阿夫拉米方程（Avrami equation）评估了添加剂对晶体生长形貌与成核条件的影响。结果发现，添加剂对成核过程并无影响，但聚合物链的迁移率有所降低，尤以添加聚异氰酸酯ε-己内酰胺的TPU最为显著。最终，在聚氯乙烯（poly(vinyl chloride), PVC）基材上，添加聚碳化二亚胺的TPU展现出最优的T型剥离强度，将胶粘剂粘接强度从3.23 N/mm提升至3.32 N/mm。