Terpenes as a sustainable monomer source for 3D printable inks and resins

添加制造(AM)是一种层层构建3D结构的过程，通常由聚合物油墨、树脂或纤维制成。与其他制造技术相比，这些技术通常会产生更少的废品量。AM特别适用于医疗、汽车和航空航天行业的复杂和定制3D部件的生产。然而，随着石化单体来源的枯竭和全球塑料垃圾数量的持续增加，开发这些油墨和树脂的可再生来源和可回收替代品是关键。因此，AM领域在可持续性方面面临两个基本挑战，适合AM油墨的可再生来源聚合物范围有限，以及依赖聚合物链之间的化学交联剂快速固化阻碍了印刷品的可回收利用。目前适合AM的可再生来源聚合物的缺乏可归因于足够长的印刷时间所需的快速反应活性以及单体、预聚体和印刷聚合物所需的严格粘度范围。在AM中，通常依赖化学交联剂作为一种快速获得能够支撑后续层的高分子量聚合物的方法，然而，交联剂往往是不可逆的，这给在产品寿命结束时实现化学循环带来了重大挑战。萜烯及其衍生物为可再生来源的聚合物提供了一类特别有前途的分子构建块。首先，萜烯可以从一系列基于生物的原料中获得，例如，从松节油和造纸和纸浆工业的大量废油中可以很容易地获得Pinene和-Pinene。其次，通过萜类骨架的官能化，可以衍生出一系列用途广泛的聚合物，包括聚烯烃、聚(甲基)丙烯酸酯、聚酯和聚丙烯酰胺。最后，通过“玻璃状”环萜烯和“橡胶状”非环萜烯的共聚，可以获得一系列具有不同玻璃化转变温度的不同材料。活性阴离子聚合(LAP)提供了合成具有高度定义的质量、分散性、组成和结构的聚合物的机会，使其成为生产高度定义的粘度的预聚体的理想候选者。基团转移聚合(GTP)表现出极快的反应动力学，可以产生没有交联剂的高分子量聚合物，因此是AM中常用的交联化学的一种引人注目的替代方法。因此，本项目将研究基于萜类单体的LAP及其相对于自由基聚合的优势，特别是分子量分布如何影响粘度。然后将评估这些萜烯预聚体的印刷适宜性，从而导致通过光引发或双组分印刷技术来印刷一些基于萜烯的新型配方。AM技术中的GTP还将使用基于萜类的单体和预聚体进行跟踪，以生产具有有限交联性的印刷聚合物，特别是改善一些以前反应缓慢的单体的反应动力学。

Additive manufacturing (AM) is the process by which 3D structures are built layer-by-layer, commonly from polymer based inks, resins or filaments. These techniques generally generate a reduced quantity of waste compared to other manufacturing techniques. AM is particularly useful for the production of complex and custom 3D parts across medical, automotive and aerospace industries. However, as petrochemical sources of monomer deplete and the worldwide quantity of plastic waste continues to increase, it is key that renewably sourced and recyclable alternatives to these inks and resins are pioneered. The field of AM is therefore faced with two fundamental challenges with respect to sustainability, there is a limited range of renewably sourced polymers suitable for AM inks and a reliance on chemical crosslinking between polymer chains to rapidly induce cure hinders recyclability of printed products.The current lack of renewably sourced polymers suitable for AM can be attributed to the rapid reactivities necessary for sufficient print times and the strict viscosity range required of monomers, pre-polymers and printed polymers. Chemical crosslinks are commonly relied upon in AM as a method of rapidly obtaining high molecular weight polymers capable of supporting subsequent layers, crosslinks however tend to be irreversible which presents major challenges for achieving chemical circularity at the end of product life-time. Terpenes and their derivatives offer a particularly promising class of molecular building blocks for renewably sourced polymers. Firstly, terpenes can be sourced from a range of biobased feedstocks, for example -pinene and -pinene are readily obtainable from turpentine an abundant waste oil from the paper and pulp industry. Secondly, a versatile range of polymers can be derived through the functionalisation of terpene skeletons, including polyolefins, poly(meth)acrylates, polyesters and polyacrylamides. Finally, through copolymerisation of "glassy" cyclic terpenes with "rubbery" acyclic terpenes, a range of different materials with varying glass transitions temperature's can be achieved.Living anionic polymerisation (LAP) offers opportunity to synthesise polymers with highly defined mass, dispersity, composition and architecture making it an ideal candidate to produce pre-polymers of highly defined viscosity. Group transfer polymerisation (GTP) displays extremely fast reaction kinetics producing high molecular weight polymers without crosslinks, and therefore presents a compelling alternative to the crosslinking chemistries commonly used across AM.Thus, this project will investigate the LAP of terpene based monomers and the advantages it provides over radical polymerisations, particularly how molecular weight distribution impacts viscosity. The printability of these terpene pre-polymers will then be assessed, leading on to the printing of some novel terpene based formulations through either photoinitiated or two component printing techniques. GTP within a AM technique will also be trailed using terpene based monomers and pre-polymers to produce printed polymers with limited crosslinking, with a particular focus improving the reaction kinetics of some previously slow reacting monomers.