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聚甲醛在沸水中的老化行为 总被引:1,自引:1,他引:1
本文考察了聚甲醛在沸水中的老化行为。结果表明,在沸水处理过程中,因沸水所引起的聚甲醛化学性质的变化较小。其老化现象主要表现为,试样表现的龟裂,添加剂的析出,变色以及拉伸断裂伸长率的下降等力学性能方面的变化。 相似文献
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光屏蔽剂对聚甲醛耐老化性能的影响 总被引:7,自引:2,他引:7
采用炭黑和纳米级氧化锌两种光屏蔽剂对共聚甲醛进行耐老化改性,对比了改性前后聚甲醛耐紫外光、耐热氧及耐热水老化性能的变化。结果表明,紫外光老化对聚甲醛性能影响最显著,两种光屏蔽剂均能减缓聚甲醛的光降解过程。炭黑的光屏蔽效果优于氧化锌,但会加速聚甲醛热氧降解。聚甲醛试样表面层相对分子质量的变化规律基本上与试样断裂伸长率、冲击强度以及色差变化规律保持一致。 相似文献
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为进一步提高聚甲醛的摩擦性能,加入超高分子量聚乙烯等材料进行改性,摩擦系数由纯聚甲醛的0.26降为0.20,磨耗由3.5mg降为1.0mg。同时,在不同负荷及转速下对含有不同固体润滑剂(如聚四氟乙烯、石墨等)的改性聚甲醛的摩擦性能进行了测试。 相似文献
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通过测定聚甲醛的熔融指数、拉伸强度及断裂伸长率,分析、比较其热老化的速度;同时应用扫描电镜、X-射线光电子能谱观察和分析了聚甲醛(POM)的表面形貌、表面官能团的类型。试验结果表明:120%热老化试验条件下,随着老化时间的延长,熔融指数逐渐增大,说明发生了缓慢的热氧化降解过程;20天短期热老化对聚甲醛拉伸强度及断裂伸长率影响不是很明显,说明POM的热老化应该有一个相当长的过程;扫描电镜显示:105天热老化后,聚甲醛表面出现龟裂和粉化现象;X-射线光电子能谱显示:老化前后样品中C1s谱均含有C-C和C-02个峰,但老化后C-C含量降低,C-O含量增加,说明POM的热老化以C-C断裂降解为主,原始试样O1s/C1s为56.98%,105天老化后为72.92%。 相似文献
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聚甲醛是具有优良性能的工程塑料之一。它有较高的模量、热变形温度、韧性、耐湿热性和低功率损耗等,但聚甲醛也存在一定的缺点,如加工收缩率大,制品尺寸稳定性差,要得到性能优异的制品必须控制聚甲醛的分子排列、分子量及其分布、熔流特性和膨胀收缩特性。本文用热分析方法研究了共聚甲醛及其改性聚合物的结晶特性,并用DSC法导出聚甲醛分子量测定的方法。从TMA和DMA法可研究聚甲醛的膨胀和收缩特性,指出了收缩较小的树脂在热分析中的表征,可以作为聚甲醛制件质量控制的依据。聚甲醛是结晶型聚合物,结晶性能可决定制件性能的优劣。Hamme… 相似文献
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Bin You Guibo Wu Shiling Zhang Fan Yang Xiancheng Ren 《Polymer Engineering and Science》2012,52(11):2403-2409
A core–shell polyacrylate elastomer containing ultraviolet (UV) stabilizer was synthesized via semicontinuous seeded emulsion polymerization from butyl acrylate (BA), methyl methacrylate (MMA), and a polymerizable UV stabilizer 2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxylproroxy)benzophenone (BPMA). The core–shell poly(MMA‐BA‐BPMA) was investigated by Fourier transform infrared spectroscopy, gel permeation chromatography UV–visible (UV–vis) absorption spectroscopy, and transmission electron microscope. Furthermore, the obtained core–shell poly(MMA‐BA‐BPMA) elastomer was used as a modifier to enhance the UV resistance and impact resistance of polyoxymethylene (POM). As studied by scanning electron microscope, the core–shell poly(BA‐MMA‐BPMA) elastomer could be well dispersed in POM matrix, indicating that the elastomer had good compatibility with POM. In addition, the POM/poly(MMA‐BA‐BPMA) blend was examined by differential scanning calorimetry before and after UV irradiation. The results showed that the melting point decreased as the irradiation time increased; however, the crystallinity culminated at 500‐h UV irradiation slightly decreased and at last leveled off. The mechanical properties of POM/poly(BA‐MMA‐BPMA) before and after UV irradiation were also studied. It revealed that the photostabilizing fragments in the elastomer could provide long‐term UV resistance to POM. Besides, the impact strength was also improved when compared with pure POM. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers 相似文献
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In this study, an acrylate elastomer with light‐stable functional groups was synthesized by methyl methacrylate (MMA), butyl acrylate (BA), and a polymerizable UV stabilizer 2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxylproroxy) benzophenone (BPMA) via emulsion polymerization, and the product was poly[methyl methacrylate‐co‐butyl acrylate‐co‐2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxylproroxy) benzophenone] [poly(MMA‐co‐BA‐co‐BPMA)]. The composition and characteristics of poly (MMA‐co‐BA‐co‐BPMA) were determined by using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H‐NMR), and ultraviolet–visible absorption spectroscopy (UV–vis). Further, the obtained poly(MMA‐co‐BA‐co‐BPMA) was blended with polyoxymethylene (POM) to modify its photostabilization, as well as the mechanical properties of POM composite were tested before and after UV irradiation. The result showed that poly(MMA‐co‐BA‐co‐BPMA) can be dispersed well in the POM matrix, which could play a role of improving compatibility with and toughening for POM, and its light‐stable functional groups could increase the UV resistance of POM composite. Mechanical properties of modified POM were kept well with higher impact strength and elongation at break than pure POM after UV irradiation. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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In order to improve the photostability of polyoxymethylene (POM), a core‐shell acrylate elastomer with UV stabilization, i.e. poly[(methyl methacrylate)‐(butyl acrylate)‐2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxypropoxy)benzophenone] (core‐shell poly(MMA‐BA‐BPMA)), was added into the POM matrix using a melt‐mixing method. The effect of the modification with core‐shell poly(MMA‐BA‐BPMA) on POM was compared with that of poly(MMA‐ co ‐BA‐ co ‐BPMA) copolymer. Scanning electron microscopy, metallographic microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X‐ray diffraction and X‐ray photoelectron spectroscopy were employed to characterize POM blends before and after UV irradiation, and the mechanical properties of the POM blends were investigated. The results showed that core‐shell poly(MMA‐BA‐BPMA) improved well the compatibility with and toughness of the POM matrix, and its light‐stable functional groups could increase the UV resistance of POM blends. During UV aging, the impact strength and elongation at break of POM/core‐shell poly(MMA‐BA‐BPMA) blends were retained, the growth rate of surface cracks of POM was inhibited effectively by core‐shell poly(MMA‐BA‐BPMA) and the degree of photo‐oxidation of POM blend surfaces was improved to a certain extent. Compared with poly(MMA‐ co ‐BA‐ co ‐BPMA), core‐shell poly(MMA‐BA‐BPMA) had a better UV stabilization effect on the POM matrix. Our results indicate that the core‐shell acrylate elastomer with toughening and UV stabilization functions can significantly improve the long‐term UV stability of POM. Copyright © 2012 Society of Chemical Industry 相似文献
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Core–shell nanoparticles chemically functionalized by hindered amine stabilizer (HAS), poly(BA‐MMA‐co‐PMPA) (PBMP), were prepared by two‐stage emulsion polymerization from butyl acrylate, methyl methacrylate, and 1,2,2,6,6‐pentamethylpiperidin‐4‐yl acrylate. The incorporation of HAS into the particles was confirmed by nuclear magnetic resonance (1H‐NMR) and the core–shell microstructure of PBMP particles was revealed by transmission electron microscopy. Furthermore, PBMP capable of one‐step toughening and photostabilizing, was melt‐blended with polyoxymethylene (POM), and its dispersion in POM was investigated by scanning electron microscope. The results showed that the core–shell nanoparticles could be well dispersed in POM matrix, indicating its good compatibility with POM. The UV resistance and impact resistance of POM were obviously improved by the HAS‐functional core–shell nanoparticles simultaneously. In addition, the core–shell nanoparticles could confer excellent protection to the surface of POM from UV‐light damage, regardless of the adverse effects on the thermal‐oxidative stability of POM, as investigated by thermogravimetry analysis under aerobic condition. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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Toughened polyoxymethylene by polyolefin elastomer and glycidyl methacrylate grafted high‐density polyethylene
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Wenqing Yang Xuan‐Lun Wang Xingru Yan Zhanhu Guo 《Polymer Engineering and Science》2017,57(10):1119-1126
Ternary blends of polyoxymethylene (POM), polyolefin elastomer (POE), and glycidyl methacrylate grafted high density polyethylene (GMA‐g‐HDPE) with various component ratios were studied for their mechanical and thermal properties. The size of POE dispersed phase increased with increasing the elastomer content due to the observed agglomeration. The notched impact strength demonstrated a parabolic tendency with increasing the elastomer content and reached the peak value of 10.81 kJ/m2 when the elastomer addition was 7.5 wt%. The disappearance of epoxy functional groups in the POM/POE/GMA‐g‐HDPE blends indicated that GMA‐g‐HDPE reacted with the terminal hydroxyl groups of POM and formed a new graft copolymer. Higher thermal stability was observed in the modified POM. Both storage modulus and loss modulus decreased from dynamic mechanical analysis tests while the loss factor increased with increasing the elastomer content. GMA‐g‐HDPE showed good compatibility between the POM matrix and the POE dispersed phase due to the reactive compatibilization of the epoxy groups of GMA and the terminal hydroxyl groups of POM. A POM/POE blend without compatibilizer was researched for comparison, it was found that the properties of P‐7.5(POM/POE 92.5 wt%/7.5 wt%) were worse than those of the blend with the GMA‐g‐HDPE compatibilizer. POLYM. ENG. SCI., 57:1119–1126, 2017. © 2017 Society of Plastics Engineers 相似文献