地下粮仓塑料-混凝土防水体系抗水压试验

地下粮仓具有节能、节地、低温和绿色环保等优点,但由于地下水的影响,防水防潮一直是安全储粮的技术难题,为此提出以聚丙烯塑料(Polypropylene Plastic,PP)作为内衬材料的塑料-混凝土防水体系,其中,塑料板与混凝土采用塑料栓钉连接。考虑不同栓钉间距200、300和400mm,设计制作了3个用于地下粮仓的塑料-混凝土水压试件,进行了水压加载试验,分析了塑料构件在水压作用下形态、破环机理、内力和变形。试验结果表明:在水压作用下,塑料板内应力和位移都随水压的增大而增大,节点位置承受较大拉力且应力最大值分布不均,跨中位置承受应力较小且最大值分布均匀;塑料板内跨中位置的位移值随水压增大呈线性增加,节点位置的位移值变化较小。在试验分析的基础上,在10mm厚塑料板和给定连接节点条件下,提出了塑料-混凝土防水体系优化设计措施,塑料-混凝土防水体系达到水压承载力时其破坏模式随栓钉间距的变化而不同,在栓钉间距为200 mm时,其水压承载力达到180 kPa时发生节点焊缝强度破环,此类构件可通过增强节点处焊缝强度提高塑料构件的整体水压承载力;在栓钉间距为300 mm时,其水压承载力达到80 k...     

麦秸/聚丙烯复合材料的动态力学和微观性能分析

以麦秸、废旧聚丙烯为主要原料,采用动态力学热分析仪(DMA)及扫描电子显微镜(SEM)等现代分析测试手段,研究麦秸/聚丙烯(PP)复合材料热力学性能及界面结合特性。结果表明:只使用马来酸酐的复合材料性能较差,没有达到刨花板国家标准指标;只使用异氰酸酯或同时使用马来酸酐和异氰酸酯的复合材料力学性能指标均达到了刨花板国家标准指标。通过对力学内耗与界面粘接参数的分析,预测了使用不同偶联剂的麦秸/聚丙烯复合材料的力学性能,结果与实际测试结果基本吻合。用扫描电镜观察的麦秸/PP复合材料微观结构,与DMA分析的结论相同。     

Comparison of water absorption and mechanical properties of wood–plastic composites made from polypropylene and polylactic acid

Abstract

This study focuses on the water absorption and mechanical properties of composites made from softwood sawdust and plastics, such as virgin and recycled polypropylene and polylactic acid (PLA). The composites were processed by extrusion, and their properties were investigated by a water immersion test, mechanical tests and a cyclic test for moisture resistance. Scanning electron microscopy was used to study the morphology of the fracture surfaces of the composites. The composites made with recycled polypropylene had the lowest water absorption and thickness swelling of the studied composites. The PLA composites made with heat-treated sawdust showed the highest flexural strength. Of the polypropylene based composites, virgin polypropylene resulted in composites with higher flexural strength. The Charpy impact strength of the composites was found to have an inverse trend compared to flexural strength. Cyclic treatment of the studied composites resulted in 20–60% loss of flexural strength, depending on type of composite.     

Evaluation of a canine small intestinal submucosal xenograft and polypropylene mesh as bioscaffolds in an abdominal full-thickness resection model of growing rats

We evaluated the biological scaffold properties of canine small intestinal submucosa (SIS) compared to a those of polypropylene mesh in growing rats with full-thickness abdominal defects. SIS is used to repair musculoskeletal tissue while promoting cell migration and supporting tissue regeneration. Polypropylene mesh is a non-resorbable synthetic material that can endure mechanical tension. Canine SIS was obtained from donor German shepherds, and its porous collagen fiber structure was identified using scanning electron microscopy (SEM). A 2.50-cm² section of canine SIS (SIS group) or mesh (mesh group) was implanted in Sprague-Dawley rats. At 1, 2, 4, 12, and 24 weeks after surgery, the implants were histopathologically examined and tensile load was tested. One month after surgery, CD68+ macrophage numbers in the SIS group were increased, but the number of CD8+ T cells in this group declined more rapidly than that in rats treated with the mesh. In the SIS group, few adhesions and well-developed autologous abdominal muscle infiltration into the SIS collagen fibers were observed. No significant differences in the tensile load test results were found between the SIS and mesh groups at 24 weeks. Canine SIS may therefore be a suitable replacement for artificial biological scaffolds in small animals.     

塑料袋闷杀柑桔大实蝇虫果死亡率调查(英文)

[目的]探索经济、高效、无污染的杀死柑桔大实蝇幼虫的科学方法。[方法]选择塑料袋加某一浓度的杀虫剂和不加杀虫剂闷处柑桔大实蝇幼虫的方法,得出幼虫死亡数据,并进行方差分析。[结果]处理5 d后,塑料袋封口不加药处理和塑料袋封口加药处理幼虫死亡率无明显差异;与加药不封闭处理相比,在隔绝空气的条件下更易杀死柑桔大实蝇幼虫。[结论]塑料袋封口不加药处理更经济有效,且不污染环境。     

Chemical modification of isotactic polypropylene by melt blending

The branched polypropylene (b-PP) was prepared by melt blending process with initiator, antioxidant, and functional monomers to improve the melt strength through the melt grafting. The melt flow index (MFI) of theb-PP was increased with increasing the initiator content. On the introduction of the alkylamine as the branching agents the MFI of theb-PP was increased, while that of theb-PP with the pentaerythritol triacrylate (PT) was decreased. It may be caused by the chain scission of thei-PP backbone due to the reduced thermal stability of thei-PP on the melt blending. The MFI of theb-PP without the antioxidant was increased due to the chain scission occurred during the melt processing, while on the introduction of the antioxidant, the MFI of theb-PP was decreased. The crystallization temperature of theb-PP was higher than that of PP, which was attributed to the branched chain structure. It was found that the PT was the most effective functional monomers for enhancing the melt properties of theb-PP.     

Comparative evaluation of metallic skin staples or polypropylene sutures for primary closure of teat wounds in sheep

ABSTRACT

Aims

To compare stainless steel staples and polypropylene suture material for primary closure of wounds after teat amputation in ewes and to assess progress of healing in the presence or absence of intramammary infection (IMI).     

特殊支链聚丙烯酸高碳醇酯的合成及降凝性能评价

对国内外多种聚丙烯酸高碳醇酯原油降凝剂分子结构及其降凝效果进行了分析和评价,美国贝克休斯公司生产的A4115对大庆管输原油降凝效果较好,该聚合物为具有特殊支链结构、分子量及分布较大的聚丙烯酸高碳醇酯.以丙烯酸、高碳醇(C18、C20、C22醇)为原料,以对苯二芬等为阻聚剂,浓硫酸为催化剂,在100～130℃条件下酯化4～6h,制得合成单体丙烯酸高碳醇酯.在不同反应条件下合成出具有特殊支链的丙烯酸高碳醇酯聚合物,并与国内外聚丙烯酸高碳醇酯原油降凝剂进行了对比试验.     

竹粉／聚丙烯塑料复合材料转矩流变特性研究

利用转矩流变仪研究了竹粉／聚丙烯塑料复合材料的转矩流变行为。使用正交试验设计分析了竹粉含量、马来酸酐添加量以及转矩转速3因素对复合材料转矩流变行为的影响。试验结果表明,竹粉／聚丙烯塑料复合材料是一种假塑性流体即剪切变稀流体。在给定的试验条件下,3种因素对复合材料转矩流变行为的影响中,竹粉含量的影响最显著,其余的2因素的影响则不显著。     

Analysis of Impervious Performance about Tunnel Polypropylene Fiber Concrete and the Experimental Comparison

Recently, most impermeability seudies of polypropylene fiber concrete, as a new sort of tunnel lining waterproof material,are limited to the impervious mechanism and unable to be satisfied with the engineering need. On the basis of fracture mechanics and the micro structure mechanics, the resistance of fiber to the crack extension inside concrete and it’s SIF were deduced, the analytical formula of fiber resistance effect to the opening mode crack extension was presented as well. Meanwhile, the impervious performance of polypropylene fiber concrete was explained reasonably by the numerical calculation of the resistance effect. On the other hand, for comparing the impervious performance of polypropylene fiber concrete with that of UEA concrete, the impervious performance experiments of four groups of different types of concrete were carried out, it is presented that the former is superior to the latter. More than that, adding double polypropylene fiber and UEA to the concrete with proper proportion will make the impervious performance much better.