Chemical recycling of thermoset composites has been focused largely on recovering high-value carbon fibers with property retention, while recovery and reuse of decomposed polymer matrix residues is generally overlooked, despite the fact that matrix recycling constitutes an essential component of a sustainable approach to the overall problem. Our previous study demonstrated that oxidative acid digestion can be deployed effectively to recover near-virgin quality carbon fibers from amine-cured epoxy composites. In the present study, we investigate the viability of recovery and reuse of the decomposed amine/epoxy residue after acid digestion of the matrix, effectively closing the recycling loop. We find that polymer matrix residues recovered from acid digestion solutions via neutralization and precipitation contain molecular components of the epoxies in which aromatic regions are preserved. The recovered matrix residues are blended into virgin resin formulations and two approaches are evaluate for potential reuse. Approach I utilizes the matrix residue as an accelerator for a virgin anhydride/epoxy formulation that contains no accelerator and thus cannot be self-catalyzed. We discover that adding matrix residue produces catalytic effects on the curing reaction. In general, anhydride/epoxy samples blended and cured with recovered matrix residues are homogenous and exhibit thermal and mechanical properties comparable to specimens cured with a commercial accelerator. Approach II deployed the matrix residue as a filler for virgin anhydride-based epoxies with a commercial accelerator to produce blended formulations. In such cases, blended formulations yielded acceptable retention of thermal and mechanical properties, provided the fraction of matrix residue added did not exceed 10 wt%.

热固性复合材料的化学回收主要集中在保留特性的高价值碳纤维的回收上，而分解的聚合物基质残留物的回收和再利用通常被忽略，尽管事实是基质回收是整体可持续发展方法的重要组成部分问题。我们之前的研究表明，可以有效地利用氧化酶消化来从胺固化的环氧复合材料中回收接近原始质量的碳纤维。在本研究中，我们研究了酸消化基质后回收和再利用分解的胺/环氧残基的可行性，有效地关闭了循环回路。我们发现，通过中和和沉淀从酸消解溶液中回收的聚合物基质残留物包含环氧树脂的分子成分，其中保留了芳香族区域。将回收的基质残留物掺入纯净的树脂配方中，并对两种方法进行了潜在的再利用评估。方法I利用基质残余物作为不含促进剂的天然酸酐/环氧制剂的促进剂，因此不能自我催化。我们发现添加基质残留物对固化反应产生催化作用。通常，与回收的基质残留物共混和固化的酸酐/环氧树脂样品是均质的，其热和机械性能与使用市售促进剂固化的样品相当。方法II使用工业促进剂将基质残留物用作纯酸酐基环氧树脂的填料，以生产混合配方。在这种情况下，如果添加的基质残留物比例不超过10 wt％，则混合制剂可以保持可接受的热和机械性能。