Costanzo Andrea, Poggi Alice, Looijmans Stan, Venkatraman Deepak, Sawyer Dan, Puskar Ljiljana, Mcllroy Claire, Cavallo Dario
Department of Chemistry and Industrial Chemistry, University of Genoa, 16146 Genova, Italy.
Department of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 Eindhoven, The Netherlands.
Polymers (Basel). 2022 Jul 8;14(14):2792. doi: 10.3390/polym14142792.
There has been extensive research in the field of material-extrusion (Mat-Ex) 3D printing to improve the inter-layer bonding process. Much research focusses on how various printing conditions may be detrimental to weld strength; many different feedstocks have been investigated along with various additives to improve strength. Surprisingly, there has been little attention directed toward how fundamental molecular properties of the feedstock, in particular the average molar mass of the polymer, may contribute to microstructure of the weld. Here we showed that weld strength increases with decreasing average molar mass, contrary to common observations in specimens processed in more traditional ways, e.g., by compression molding. Using a combination of synchrotron infra-red polarisation modulation microspectroscopy measurements and continuum modelling, we demonstrated how residual molecular anisotropy in the weld region leads to poor strength and how it can be eradicated by decreasing the relaxation time of the polymer. This is achieved more effectively by reducing the molar mass than by the usual approach of attempting to govern the temperature in this hard to control non-isothermal process. Thus, we propose that molar mass of the polymer feedstock should be considered as a key control parameter for achieving high weld strength in Mat-Ex.
在材料挤出（Mat-Ex）3D打印领域，为改善层间粘结工艺已开展了广泛研究。许多研究聚焦于各种打印条件如何对焊接强度产生不利影响；人们研究了许多不同的原料以及各种添加剂以提高强度。令人惊讶的是，很少有人关注原料的基本分子特性，特别是聚合物的平均摩尔质量，如何对焊缝微观结构产生影响。在此我们表明，与通过压缩成型等更传统方式加工的试样中的常见观察结果相反，焊接强度随平均摩尔质量的降低而增加。通过结合同步加速器红外偏振调制显微光谱测量和连续介质建模，我们证明了焊缝区域的残余分子各向异性如何导致强度不佳，以及如何通过缩短聚合物的弛豫时间来消除这种情况。与在这个难以控制的非等温过程中试图控制温度的常规方法相比，降低摩尔质量能更有效地实现这一点。因此，我们建议应将聚合物原料的摩尔质量视为在Mat-Ex中实现高焊接强度的关键控制参数。
