淀粉基非异氰酸酯聚氨酯胶黏剂的制备及性能研究

Preparation and Properties of Starch-based Non-isocyanate Polyurethane Adhesives

在无溶剂、无催化剂的条件下,采用两步法合成淀粉基非异氰酸酯聚氨酯(DPHU)胶黏剂。以二元胺和双(六元环碳酸酯)(BCC)为原料,合成氨基封端的聚羟基聚氨酯(NPHU)预聚物;进一步以双醛淀粉(DAS)为主要原料,与NPHU预聚物进行希夫碱反应合成DPHU胶黏剂,详细探讨了二元胺的相对分子质量和结构以及DAS添加量对其性能的影响。研究结果表明:随着(二元胺)聚醚胺相对分子质量的增加,NPHU预聚物的粘合性能降低,当聚醚胺相对分子质量为230时,NPHU-D230预聚物的搭接剪切强度最高可达5.35 MPa;酰胺键的存在会提高其粘合性能。随着DAS添加量的增加,DPHU的搭接剪切强度呈现先上升后下降的趋势,当DAS添加量(以质量分数计)为30%时,DPHU-30的搭接剪切强度最高达到6.26 MPa。力学性能分析表明:通过调节DAS添加量,可使DPHU在韧性和刚性材料之间进行转化,DAS添加量为70%时制得的样品DPHU-70的拉伸强度高达6.74 MPa,断裂伸长率可达12.59%。DPHU还具有良好的热稳定性、自愈合性能及形状记忆特性。当DAS添加量从0增加到70%时,DPHU-0~DPHU-70的玻璃化转变温度(T_(g))从16.14℃升高至31.56℃;当DAS添加量为0~50%时,DPHU-0~DPHU-50的表面划痕在50℃下、3 min内的自修复效率可达90%以上;将DPHU-30样条进行折叠,重复加热-冷却循环过程,样条可在短时间内恢复原状。

A starch-based non-isocyanate polyurethane(DPHU)adhesive was synthesized by a two-step process under solvent-free and catalyst-free conditions.A mine-blocked polyhydroxy urethane(NPHU)prepolymers was synthesized from diamine and bis(six-membered ring carbonate)(BCC),and the prepolymers were further reacted with dialdehyde starch(DAS)by a Schiff-base reaction to synthesize DPHU adhesives.The molecular weight and structure of diamines as well as the effect of DAS addition on their properties were investigated in detail.The results showed that the adhesive properties of NPHU prepolymers decreased with the increase of the molecular weight of the polyether amine.When the relative molecular mass of polyether amine was 230,the lap shear strength of NPHU-D230 prepolymer was up to 5.35 MPa.The presence of the amide bond improved the adhesive properties of NPHU prepolymers.With the increase of DAS addition,the lap shear strength of DPHU showed a tendency of increasing first and then decreasing,and the lap shear strength of DPHU-30 reached up to 6.26 MPa when the DAS addition(in terms of mass fraction)was 30%.The mechanical properties analysis showed that DPHU could be transformed between toughness and rigidity materials by adjusting the DAS addition amount.The DAS addition amount reached up to 70%,the tensile strength of prepared DPHU-70 was as high as 6.74 MPa,and the elongation at break was up to 12.59%.In addition,DPHU had good thermal stability,self-healing properties,and shape memory properties.The glass transition temperature(T_(g))of DPHU-0-DPHU-70 increased from 16.14℃to 31.56℃when the DAS addition increased from 0 to 70%.When the DAS addition was 0-50%,the self-repairing efficiency of the surface scratches of DPHU-0-DPHU-50 could reach more than 90%in 3 min at 50℃.The DPHU spline was folded and the heating-cooling cycle was repeated,and the spline could be restored to its original state in a short time.