Velásquez Eliezer, Patiño Vidal Cristian, Copello Guillermo, López de Dicastillo Carol, Pérez C J, Guarda Abel, Galotto María José
Packaging Innovation Center (LABEN-Chile), University of Santiago of Chile (USACH), Santiago 9170201, Chile.
Center for the Development of Nanoscience and Nanotechnology (CEDENNA), University of Santiago of Chile, Santiago 9170124, Chile.
Polymers (Basel). 2023 Feb 24;15(5):1142. doi: 10.3390/polym15051142.
Collection and mechanical recycling of post-consumer flexible polypropylene packaging is limited, principally due to polypropylene being very light-weight. Moreover, service life and thermal-mechanical reprocessing degrade PP and change its thermal and rheological properties according to the structure and provenance of recycled PP. This work determined the effect of incorporating two fumed nanosilica (NS) types on processability improvement of post-consumer recycled flexible polypropylene (PCPP) through ATR-FTIR, TGA, DSC, MFI and rheological analysis. Presence of trace polyethylene in the collected PCPP increased the thermal stability of the PP and was significantly maximized by NS addition. The onset decomposition temperature raised around 15 °C when 4 and 2 wt% of a non-treated and organically modified NS were used, respectively. NS acted as a nucleating agent and increased the crystallinity of the polymer, but the crystallization and melting temperatures were not affected. The processability of the nanocomposites was improved, observed as an increase in viscosity, storage and loss moduli with respect to the control PCPP, which were deteriorated due to chain scission during recycling. The highest recovery in viscosity and reduction in MFI were found for the hydrophilic NS due to a greater impact of hydrogen bond interactions between the silanol groups of this NS and the oxidized groups of the PCPP.
消费后柔性聚丙烯包装的收集和机械回收受到限制，主要原因是聚丙烯重量非常轻。此外，使用寿命和热机械再加工会使聚丙烯降解，并根据回收聚丙烯的结构和来源改变其热性能和流变性能。本工作通过ATR-FTIR、TGA、DSC、MFI和流变分析，确定了两种气相纳米二氧化硅（NS）对消费后回收柔性聚丙烯（PCPP）加工性能改善的影响。收集到的PCPP中痕量聚乙烯的存在提高了聚丙烯的热稳定性，并且通过添加NS显著最大化。当分别使用4 wt%的未处理NS和2 wt%的有机改性NS时，起始分解温度提高了约15℃。NS作为成核剂，提高了聚合物的结晶度，但结晶温度和熔融温度不受影响。观察到纳米复合材料的加工性能得到改善，相对于对照PCPP，其粘度、储能模量和损耗模量增加，对照PCPP由于回收过程中的断链而性能恶化。由于这种NS的硅醇基团与PCPP的氧化基团之间的氢键相互作用影响更大，亲水性NS的粘度恢复最高，熔体流动指数降低最多。
