湿热处理对制动夹钳尼龙衬套材料性能的影响

为自主化研制制动夹钳单元用尼龙衬套,通过实验测试研究调湿处理、烘干热处理、硅油热处理等后工艺对尼龙6的力学性能、摩擦磨损性能、吸水性能的影响。结果表明,硅油热处理后尼龙6的拉伸、摩擦磨损性能、吸水性能明显改善,为衬套材料的改性提供依据。     

注塑工艺及调湿处理对半芳香透明尼龙力学性能的影响

研究了模具温度、注塑压力和注射速率对半芳香(SA)透明尼龙拉伸强度、断裂伸长率、弯曲强度、弯曲弹性模量和缺口冲击强度等力学性能的影响,并对SA透明尼龙调湿处理前后的力学性能进行了比较。结果表明,当料筒温度为240～245℃,注塑压力为70-130MPa,模具温度为40—80℃时,SA透明尼龙能顺利注塑,其力学性能随注塑压力的增大呈提高趋势,而模具温度和注射速率对其力学性能影响不太明显;经过调湿处理后,SA透明尼龙的缺口冲击强度有所提高。     

湿热环境下HTPB推进剂的吸湿性能

在60℃/75%RH、60℃/85%RH、70℃/75%RH和70℃/85%RH环境下对HTPB推进剂进行了吸湿试验,测定了吸湿率和力学性能参数,分析了吸湿规律、吸湿影响因素和力学性能恢复能力。结果表明,HTPB推进剂在湿热环境下的吸湿不同于常温吸湿;不同湿度下的吸湿率变化规律具有明显差异,75%RH环境下吸湿率呈现出先上升后下降的变化规律,而85%RH环境下吸湿率只呈现出上升规律。高温和高湿环境对推进剂吸湿性能影响显著,去湿处理后推进剂力学性能不能完全恢复。     

湿热循环对PMI泡沫/3218-1环氧树脂夹层结构性能影响的研究

通过对PMI泡沫/3218-1环氧树脂夹层结构进行湿热处理,测定夹层复合材料的吸湿、脱湿曲线,研究湿热对夹层复合材料的吸湿性能的影响,同时对湿热循环处理前后的夹层复合材料试样进行力学性能和介电性能的测试,以研究湿热循环对两种PMI泡沫/3218-1环氧树脂夹层结构的吸湿性能、力学性能及介电性能的影响。     

硫酸钙晶须短玻纤协同增强尼龙6复合材料的力学性能

以尼龙6为基体树脂,硫酸钙晶须和短玻纤为增强材料制备了硫酸钙晶须/短玻纤/尼龙6复合材料,研究了不同晶须含量对复合材料力学性能的影响。结果显示,晶须含量不超过10%时,晶须与短玻纤对尼龙6有协同增强作用,拉伸强度、弯曲强度和弯曲模量分别提高了8.7%、7.5%和8%;经过表面处理的晶须增强效果好于未经表面处理晶须;采用侧向加入增强材料方式制备的复合材料力学性能远优于主料口加入方式。     

吸湿行为对PMI泡沫性能及应用的影响

研究了在不同条件处理下，聚甲基丙烯酰亚胺（PMI）泡沫的密度、孔径和厚度对其吸湿行为的影响，并实验验证PMI泡沫吸湿后对其力学性能、烘干可逆性及粘接性能的影响。结果表明，PMI泡沫密度越大，吸湿速率越小；孔径越大，吸湿速率越大；厚度越大，吸湿速率越小，饱和吸湿率越低；吸湿后，PMI泡沫刚性下降，韧性增强，粘接时易出现缺陷；在短期的高湿环境或浸水下，PMI泡沫性能烘干可逆，长期在高湿环境或浸水条件下处理后，PMI泡沫性能出现不可逆下降。     

非连续湿热作用下树脂基复合材料性能变化及机理的研究

为研究非连续湿热作用对树脂基复合材料性能的影响及其湿热老化机理,对碳纤维增强环氧树脂基复合材料T700/TR1219B进行了湿热环境因素对比实验及循环吸湿实验,对比了经历不同吸湿-脱湿历程试样的弯曲和层间剪切性能及微观断口形貌。结果表明,单一湿度因素使T700/TR1219B体系力学性能降低,单一温度因素使其弯曲性能降低,层间剪切性能增强,湿热耦合作用会加剧材料性能的劣化;材料的吸湿和脱湿过程均满足Fick定律;随着循环次数的增加,材料的吸湿和脱湿速率均有所加快;吸湿后T700/TR1219B体系力学性能降低,出现树脂脱落等现象,脱湿后弯曲性能无法恢复未老化状态,但层间性能略有增加,且界面脱黏情况得以改善,层间裂纹不再明显。     

聚丙烯酸酯内墙调湿涂料的性能研究

以聚丙烯酸树脂为调湿剂，制备内墙调湿涂料。经调湿性能测试，涂膜可以在高湿度环境下吸湿，在低湿环境下放湿，具有调湿功能，当调湿剂用量为14％时，调湿涂料综合性能最佳。     

尼龙制件吸湿变形及预防措施研究

尼龙66暴露在空气中会吸水,这会影响其制件的尺寸稳定性。以空客A320登机门尼龙66抓手为例,对吸湿后产生的变形及如何通过人工加速增湿处理控制和预防变形以稳定产品尺寸进行了研究。     

利用吸湿材料制备建筑多孔调湿陶瓷的研究

现代建筑中的干湿问题对人居环境的影响越来越明显,因此,具有调湿功能的建筑材料已成为国内外生态建材发展的重点之—。本文利用抛光废渣、陶瓷用普通原料,以及吸湿材料硅藻土、海泡石等制备多孔吸湿陶瓷材料,并研究了吸湿材料的外加量对吸湿性能的影响。同时,探讨了最佳制备工艺及烧成制度。本文利用基础料与吸湿材料的不同颗粒级配均匀混合,可制备出吸湿性较好的多孔调湿陶瓷,其吸湿率平均在175 g/㎡。     

环境湿度对聚酰胺力学性能的影响及其微观机理探讨

从环境湿度角度对聚酰胺(PA)的力学性能进行了研究。选用PA66进行一系列的有关湿度试验。通过不同湿度环境下与时间相关的力学性能试验,研究了环境湿度对PA66力学性能的影响。发现,在老化初期PA66的力学性能下降,但随着时间的延长,力学性能有所回升,有的甚至略微超过原始性能。同时,也探讨了引起PA性能变化的微观机理。     

汽车用增韧尼龙6的热氧老化研究

分别研究了马来酸酐接枝(乙烯/辛烯)共聚物(POE)、铜盐抗氧剂和受阻酚类抗氧剂1010、1098及其与亚磷酸酯类抗氧剂626复配体系对增韧改性尼龙(PA)6材料抗热氧老化性能的影响,研究了不同抗氧剂体系和热老化时间对材料拉伸强度、简支梁缺口冲击强度的影响。结果表明,在增韧PA6材料中添加合适的抗氧剂可以满足材料在160℃条件下热氧老化24 h后力学性能保持率在90%以上的要求,该材料可以应用于汽车燃油管路系统。     

Effect of Polyamide 66 on the Mechanical and Thermal Properties of Post-Industrial Waste Polyamide 6

Post-industrial waste (PIW) polyamide 6 is successfully used in lieu of commercial virgin polyamide 6, in several automotive applications. The presence of polyamide 66 in the final formulation may affect the mechanical and thermal properties of the PIW polyamide 6 materials. Using unreinforced polyamide 6 from PIW and commercial sources, it was found that the addition of polyamide 66 (below 10 wt.%) lowered the crystallization rate and crystallinity level of all polyamide 6 materials. The thermal and mechanical properties of glass fiber (GF) reinforced PIW polyamide 6 compounds with and without polyamide 66 were also studied. Differential scanning calorimetry (DSC) showed that reinforced materials without polyamide 66 had a higher level of crystallinity. Furthermore, dynamic mechanical analysis (DMA) showed that reinforced compounds without polyamide 66 also had a faster storage modulus buildup immediately after injection molding. Reinforced PIW polyamide 6 compounds without polyamide 66 also exhibited higher tensile and higher vibration weld strengths as well as a thicker heat affected zone (HAZ) than those with polyamide 66, leading to the conclusion that polyamide 66 had a detrimental effect on crystallinity level and consequently on the mechanical properties of GF-reinforced PIW polyamide 6 materials.     

Experimental investigation of the effect of hygrothermal aging on the mechanical performance of carbon nanotube/PA6 nanocomposite

The effect of hygrothermal aging on the mechanical behaviour of polyamide 6 (PA6) material filled with 10 wt % multi-walled carbon nanotubes (MWCNTs) has been investigated experimentally. Young’s modulus and flexural modulus of the materials are decreased by more than 30% for the conditions of 25°C/85% RH, compared to the reference conditions of 25°C/55% RH (RT), while the flexural strength by 6–17%. The decrease is larger for the conditions of 40°C/85% RH, which reveals that the effect of combined elevated temperature and moisture is more severe. The decrease in the properties is smaller for the MWCNT/PA6 specimens, which shows that the presence of MWCNTs mitigates the effect of hygrothermal aging. Finally, it is observed that the increase in the properties of the MWCNT/PA6 material is so large, for the specific MWCNT concentration, that it compensates the negative effect of hygrothermal aging.     

Study on the damage behavior of carbon fiber composite after low-velocity impact under hygrothermal aging

In this article, T800 carbon fiber/epoxy resin composite was subjected to hygrothermal aging. By analyzing the mass change, surface morphology before and after aging, infrared spectra, and dynamic mechanical properties, the effect of hygrothermal aging on the composite properties was studied. The hygrothermal aging of the composite after low-velocity impact, the effects of environmental factors on the damaged area, and the post-impact compression properties of composites were studied. The results showed that the saturation moisture absorption rate of the composite after aging (71°C constant temperature) was 0.88%. Upon increasing the impact energy, an indentation appeared before the inflection point at 35 J. When the impact energy was less than 15 J, aging did not affect invisible damage. Above this, the damaged area and number of internal cracks and defects in the composite were increased. After aging, the compressive strength of composite laminates with impact damage decreased obviously. During the aging stage, the residual compressive strength of the sample was the lowest in the moisture saturated state, and hygrothermal aging had little effect on the compression failure mode after impact.     

Study on the long‐term thermal‐oxidative aging behavior of polyamide 6

The long‐term thermal‐oxidative aging behavior of polyamide 6 (PA6) was studied by comparison with the stabilized sample in this work. The variation of mechanical properties of the pure and the stabilized samples of PA6 with aging time at 110°C, 130°C, and 150°C were investigated, respectively. The aging mechanism of PA6 under heat and oxygen was studied in terms of the reduced viscosity, crystallization behavior, dynamic mechanical behavior, and chemical composition through the methods of polarized light microscopy (PLM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X‐ray photoelectron energy spectrum (XPS), and so on. The results indicated that at the initial stage of aging, the molecular crosslinking reaction of PA6 dominated resulting in the increase of the mechanical strength, reduced viscosity, and the glass transition temperature of the sample. And the molecular degradation dominated in the subsequent aging process resulting in the decrease of the melting temperature, the increase of the crystallinity, and the formation of the oxides and peroxides products. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Stress–thermooxidative aging behavior of polyamide 6

The long‐term stress–thermooxidative aging behavior of polyamide 6 (PA6) was studied in terms of the creep behavior, mechanical properties, chemical structure, crystallization, and orientation behavior. During aging, a thermooxidation reaction occurred, which included molecular chain degradation and crosslinking, in PA6. Meanwhile, when the samples were subjected to stress, crystallization, orientation, and chain scission were induced. In the initial stages of aging, the stress‐induced crystallization and orientation dominated; this resulted in an increase in the creep deformation, mechanical strength, crystallinity, and orientation factor. Molecular degradation and chain scission dominated in the subsequent aging process and resulted in a decrease of the mechanical strength, reduced viscosity, crystallinity, and orientation factor and an increase in the formation of oxide and peroxide products. The stress may have promoted the chain scission of PA6 during thermal aging and resulted in a decrease in the reduced viscosity and an increase in the carboxylic acid concentration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of thermooxidative aging on the static and dynamic mechanical properties of long‐glass‐fiber‐reinforced polyamide 6 composites

The static and dynamic mechanical properties, thermal behaviors, and morphology of pure long‐glass‐fiber‐reinforced samples [polyamide 6 (PA6)/long glass fiber (LGF)] with different thermal exposure times at 160°C were studied by comparison with stabilized samples in this study. The aging mechanism of the PA6/LGF samples under heat and oxygen was studied with the methods of thermal Fourier transform infrared (FTIR), differential scanning calorimetry, dynamic mechanical analysis, scanning electron microscopy (SEM), and so on. The results indicate that the static mechanical strength, melting temperature, and crystallization temperature decreased because of the decomposition of the macromolecular chain of PA6 resin and the debonding of the interface between the glass fibers and matrix. The glass‐transition temperature and crystallinity also increased and decreased, respectively, after aging. The macromolecular chain decomposition dominated in the subsequent aging process; this resulted in many sharp and brittle microcracks appearing on the surfaces of the aged samples, as shown by SEM and the FTIR spectra. The existence of stabilizers endowed the PA6/LGF composites with better retention of static and dynamic mechanical properties. The reason was that the metal ions of the copper salt antioxidant acted as an anti‐aging catalyst in the reinforced PA6 system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39594.     

尼龙6在热氧老化中的性能与结构变化

通过挤出共混法制备了添加不同抗老化助剂的尼龙6(PA6),以改善PA6的耐老化性能。考察了PA6试样暴露在125℃的热空气中一定时间后其黄色指数(YI)、色差(△E)、热稳定性能和力学性能的变化;系统地研究了不同抗氧剂对PA6在这一热氧老化过程中的变色行为和力学性能的影响;以黄色指数值达到55作为失效的指标,对PA6热氧老化试样进行了静态使用寿命的分析与预测;使用红外光谱(FTIR-ATR)分析了PA6试样在热氧老化过程的结构变化。研究结果表明:使用胺类抗氧剂能明显地改善PA6的抗热氧老化变色性能,还能使其保持较高的热稳定性能和力学性能,并大大延长PA6的静态使用寿命;用酚类抗氧剂/亚磷酸酯抗氧剂组成(1:1)的稳定体系能对改善PA6的耐热氧老化性能产生协同效应。     

ABS/PA6共混体系的反应性增容研究

用少量苯乙烯-马来酸酐(SMA)作为相容剂改善ABS/PA6共混体系的相容性,研究了共混体系(固定ABS/PA6质量比为70/30)中相容剂的最佳用量,以及随相容剂含量变化引起的体系形态结构和力学性能变化情况,同时探讨了体系组成与性能关系的微观机理。还研究了环境因素对ABS/PA6共混体系性能的影响。