Benincasa Paolo, Dominici Franco, Luzi Francesca, Governatori Catia, Pauselli Mariano, Tosti Giacomo, Sarasini Fabrizio, Puglia Debora
Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno, 74, 06123 Perugia, Italy.
Department of Civil and Environmental Engineering, University of Perugia, Strada di Pentima 4, 05100 Terni, Italy.
Polymers (Basel). 2025 May 15;17(10):1347. doi: 10.3390/polym17101347.
Previous research has demonstrated the possibility to produce wheat flour-based thermoplastics, whose tensile properties depend on flour characteristics that are affected by wheat variety and crop nitrogen (N) fertilization management. This work further investigates the reinforcing effect on thermoplastic composites determined by wheat straw obtained from two wheat varieties (Bologna, BL; Bora, BR) grown under four N fertilization treatments differing in rate and application timing as follows: (1) always well N fed (N300: fertilized with 300 kg N ha and split into five applications of 60 kg N ha each across the growing cycle), (2) N fed only very early (N60+0: fertilized only in one early application of 60 kg N ha), (3) N fed only very late (0+120: fertilized only in one application of 120 kg N ha at pollination) and (4) never N fed (N0). The finely cut straw was added by 15% () to the flour of treatment N300 of each corresponding wheat variety to produce thermoplastic bulk samples. We performed the analysis of straw composition, FESEM imaging of straw stems, X-Ray diffraction analysis of flours and straws, thermal analysis of straw, and tensile tests on bulk samples. The results demonstrate that, for both cultivars, the reinforcing effect of the straw was maximum when the straw came from crops grown with low and early N availability (i.e., N0 and N60+0) and minimum when the straw came from crops grown with high and late N availability (i.e., N300 and N0+120). The greater reinforcing effect of straw from N0 and N60+0 was likely due to greater stem compactness, higher cellulose proportion and higher crystalline fractions. The reinforcing effect decreased for all plasticized composites when they were stabilized for 48 h at higher ambient humidity (53% RH vs. 11% RH) before performing the tensile tests. Overall, our results confirm that plant-based materials engineering needs to carefully consider the variability of source material characteristics as affected by crop growing conditions.
先前的研究已经证明了生产基于小麦粉的热塑性塑料的可能性，其拉伸性能取决于受小麦品种和作物氮（N）肥管理影响的面粉特性。这项工作进一步研究了由两种小麦品种（博洛尼亚，BL；博拉，BR）收获的小麦秸秆对热塑性复合材料的增强效果，这两种小麦在四种施氮处理下生长，施氮量和施用时间不同，如下所示：（1）始终氮肥充足（N300：每公顷施300千克氮，并在整个生长周期内分五次施用，每次60千克氮/公顷），（2）仅在很早的时候施氮（N60 + 0：仅在一次早期施用60千克氮/公顷），（3）仅在很晚的时候施氮（0 + 120：仅在授粉时一次施用120千克氮/公顷），以及（4）从不施氮（N0）。将切碎的秸秆以15%（）添加到每个相应小麦品种的N300处理的面粉中，以生产热塑性块状样品。我们进行了秸秆成分分析、秸秆茎的场发射扫描电子显微镜成像、面粉和秸秆的X射线衍射分析、秸秆的热分析以及块状样品的拉伸试验。结果表明，对于两个品种来说，当秸秆来自低氮且早期施氮的作物（即N0和N60 + 0）时，秸秆的增强效果最大，而当秸秆来自高氮且晚期施氮的作物（即N300和0 + 120）时，增强效果最小。来自N0和N60 + 0的秸秆具有更大增强效果，可能是由于茎更致密、纤维素比例更高和结晶度更高。在进行拉伸试验之前，当所有增塑复合材料在较高环境湿度（53%相对湿度与11%相对湿度）下稳定48小时后，其增强效果降低。总体而言，我们的结果证实，基于植物的材料工程需要仔细考虑受作物生长条件影响的原材料特性的变异性。
