增韧剂，是指能增加胶黏剂膜层柔韧性的物质。某些热固性树脂胶黏剂，如环氧树脂、酚醛树脂和不饱和聚酯树脂胶黏剂固化后伸长率低，脆性较大，当粘接部位承受外力时很容易产生裂纹，并迅速扩展，导致胶层开裂，不耐疲劳，不能作为结构粘接之用。因此，必须设法降低脆性，增大韧性，提高承载强度。凡能减低脆性，增加韧性，而又不影响胶黏剂其他主要性能的物质即为增韧剂。可分为橡胶类增韧剂和热塑性弹性体类增韧剂。
Toughening agent is the material that can increase the flexibility of adhesive film. Some thermosetting resin adhesives, such as epoxy resin, phenolic resin and unsaturated polyester resin adhesive, have low elongation and high brittleness. When the adhesive part bears the external force, it is easy to produce cracks and expand rapidly, resulting in the cracking of the film, fatigue and cannot be used as a structural adhesive. Therefore, we must try to reduce brittleness, increase toughness and increase bearing strength. Any substance that can reduce brittleness and increase toughness without affecting other main properties of adhesives is a toughening agent. It can be divided into rubber toughening agent and thermoplastic elastomer toughening agent.
增韧剂一般都含有活性基团，能与树脂发生化学反应，固化后不完全相容，有时还要分相，会获得较理想的增韧效果，使热变形温度不变或下降甚微，而抗冲击性能又明显改善。一些低分子液体或称之为增塑剂之物加入树脂之中，虽然也能降低脆性，但刚性、强度、热变形温度却大幅度下降，不能满足结构粘接要求，因此，增塑剂与增韧剂是完全不同的。
The toughening agent generally contains active groups, which can react with the resin. After curing, the toughening agent can not be completely compatible, and sometimes it is also phase separation. The toughening agent will get a better toughening effect, make the thermal deformation temperature change or decrease slightly, and the impact resistance performance is obviously improved. Some low-molecular-weight liquids or plasticizers are added to the resin, although they can also reduce brittleness, but the rigidity, strength and thermal deformation temperature drop greatly, which can not meet the requirements of structural adhesion. Therefore, plasticizers and toughening agents are completely different.
有些线型高分子化合物，能与树脂混溶，含有活性基团，可以参与树脂的固化反应，提高断裂伸长率和冲击强度，但热变形温度有所下降，这种物质称之为增柔剂（flexibizer），常用的有液体聚硫橡胶、液体丁腈橡胶，由于它们与树脂适量配合，可以制成结构胶黏剂，所以也将增柔剂归入增韧剂之类。增柔与增韧虽是相互关联又不相同的概念，但实际上却很难严格区分开来。从理论上讲增韧与增柔不同，增韧它不使材料整体柔化，而是将环氧树脂固化物均相体系变成一个多相体系，即增韧剂聚集成球形颗粒在环氧树脂的交联网络构成的连续相中形成分散相，抗开裂性能发生突变，断裂韧性显著提高，但力学性能、耐热性损失较小。
Some linear polymers, which can be mixed with the resin, contain active groups, can participate in the curing reaction of the resin, improve the elongation at break and the impact strength, but the thermal deformation temperature decreases. This substance is called the softening agent (flexibizer), and the common liquid polysulfide rubber and liquid nitrile rubber are commonly used because of them. With the proper amount of resin, it can be made into structural adhesives, so the softening agent is added to toughening agent. Although softening and toughening are interrelated and different concepts, they are hard to distinguish strictly. In theory, toughening and softening are different, and toughening it does not make the whole material softened, but the homogeneous phase system of the epoxy resin solidified into a multiphase system, that is, the toughening agent is formed into a dispersed phase in the continuous phase of the epoxy resin crosslinking network, and the cracking resistance is mutated and the fracture toughness is significantly raised. It is high, but the loss of mechanical property and heat resistance is less.
增韧机理
Toughening mechanism
不同类型的增韧剂，有着不同的增韧机理。液体聚硫橡胶可与环氧树脂反应，引入一部分柔性链段，降低环氧树脂模量，提高了韧性，却牺牲了耐热性。液体丁腈橡胶作为环氧树脂的增韧剂，室温固化时几乎无增韧效果，粘接强度反而下降；只有中高温固化体系，增韧与粘接效果较明显。端羧基液体丁腈橡胶增韧环氧树脂，固化前相容，固化后分相，形成“海岛结构”，既能吸收冲击能量，又基本不降低耐热性。T-99多功能环氧固化剂固化环氧树脂使交联结构中引进了柔性链段，不产生分相结构，在提高韧性的同时基本不降低耐热性。
Different types of toughening agents have different toughening mechanisms. Liquid polysulfide rubber can react with epoxy resin, introduce a part of flexible segments, reduce the modulus of epoxy resin, improve toughness, but sacrifice heat resistance. Liquid NBR, as a toughening agent for epoxy resin, almost had no toughening effect at room temperature, and the bonding strength decreased, and the toughening and bonding effect was obvious only in the medium and high temperature curing system. The carboxyl liquid NBR toughened the epoxy resin, which is compatible before curing and solidified to form a "island structure", which not only absorbs the impact energy, but also basically does not reduce the heat resistance. The T-99 multifunction epoxy curing agent solidified the epoxy resin by introducing a flexible chain section in the crosslinking structure, which does not produce a phase separation structure, and does not reduce the heat resistance at the same time.
