Lok Bianca, Mueller Gunnar, Buettner Andrea, Bartel Melanie, Erdmann Jens
Fraunhofer Institute for Process Engineering and Packaging IVV, Giggenhauser Straße 35, 85354 Freising, Germany.
Chair of Aroma and Smell Research, Department of Chemistry and Pharmacy, Friedrich-Alexander-Universität Erlangen-Nürnberg, Henkestraße 9, 91054 Erlangen, Germany.
Polymers (Basel). 2022 Jun 29;14(13):2660. doi: 10.3390/polym14132660.
The comprehensive use of natural polymers, such as lignin, can accelerate the replacement of mineral oil-based commodities. Promoting the material recovery of the still underutilized technical lignin, polyolefin-lignin blends are a highly promising approach towards sustainable polymeric materials. However, a limiting factor for high-quality applications is the unpleasant odor of technical lignin and resulting blends. The latter, especially, are a target for potential odor reduction, since heat- and shear-force intense processing can intensify the smell. In the present study, the odor optimization of kraft and soda HDPE-lignin blends was implemented by the in-process application of two different processing additives-5% of activated carbon and 0.7% of a stripping agent. Both additives were added directly within the compounding process executed with a twin screw extruder. The odor properties of the produced blends were assessed systematically by a trained human panel performing sensory evaluations of the odor characteristics. Subsequently, causative odor-active molecules were elucidated by means of GC-O and 2D-GC-MS/O while OEDA gave insights into relative odor potencies of single odorants. Out of 70 different odorants detected in the entirety of the sample material, more than 30 sulfur-containing odorants were present in the kraft HDPE-lignin blend, most of them neo-formed due to high melt temperatures during extrusion, leading to strong and smells. The addition of activated carbon significantly decreased especially these sulfurous compounds, resulting in 48% of overall odor reduction of the kraft blend (mean intensity ratings of 5.2) in comparison to the untreated blend (10.0). The applied stripping agent, an aqueous solution of polymeric, surface-active substances adsorbed onto a PP carrier, was less powerful in reducing neo-formed sulfur odorants, but led to a decrease in odor of 26% in the case of the soda HDPE-lignin blend (7.4). The identification of single odorants on a molecular level further enabled the elucidation of odor reduction trends within single compound classes. The obtained odor reduction strategies not only promote the deodorization of HDPE-lignin blends, but might be additionally helpful for the odor optimization of other natural-fiber based materials.
天然聚合物（如木质素）的综合利用能够加速矿物油基商品的替代。为推动仍未得到充分利用的工业木质素的材料回收，聚烯烃-木质素共混物是实现可持续聚合物材料的一种极具前景的方法。然而，高质量应用的一个限制因素是工业木质素及其制成的共混物存在难闻气味。尤其是后者，由于强烈的热和剪切力加工会加剧气味，因此是潜在气味降低的目标。在本研究中，通过在加工过程中使用两种不同的加工添加剂（5%的活性炭和0.7%的汽提剂）对硫酸盐法和烧碱法高密度聚乙烯-木质素共混物进行气味优化。两种添加剂均在双螺杆挤出机进行的混合过程中直接添加。由经过培训的人员组成的小组对所生产共混物的气味特性进行感官评估，从而系统地评估其气味特性。随后，通过气相色谱-嗅觉测定法（GC-O）和二维气相色谱-质谱-嗅觉测定法（2D-GC-MS/O）阐明产生气味的活性分子，而气味提取物稀释分析（OEDA）则深入了解单一气味物质的相对气味强度。在整个样品材料中检测到70种不同的气味物质，硫酸盐法高密度聚乙烯-木质素共混物中存在30多种含硫气味物质，其中大多数是由于挤出过程中的高熔体温度新形成的，产生强烈的[此处原文缺失具体气味描述]气味。活性炭的添加尤其显著降低了这些含硫化合物的含量，与未处理的共混物（平均强度评分为10.0）相比，硫酸盐法共混物的总体气味降低了48%（平均强度评分为5.2）。所应用的汽提剂是一种吸附在聚丙烯载体上的聚合物表面活性物质的水溶液，在减少新形成的含硫气味物质方面效果较差，但在烧碱法高密度聚乙烯-木质素共混物（平均强度评分为7.4）的情况下，气味降低了26%。在分子水平上对单一气味物质的鉴定进一步有助于阐明单一化合物类别中的气味降低趋势。所获得的气味降低策略不仅促进了高密度聚乙烯-木质素共混物的除臭，而且可能对其他天然纤维基材料的气味优化也有帮助。
