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1.
An efficient, convenient and quantitative method for characterising polyester end-groups is described. We have found that trichloroacetyl isocyanate (TAI) reacts rapidly and quantitatively with both carboxyl [C(O)OH] and hydroxyl (OH) chain ends to form derivatives that can be readily determined by 1H NMR spectroscopy. The TAI capped end-groups give rise to characteristic imidic NH resonances in a normally clear region of the 1H NMR spectrum [δ∼10-11.5 for C(O)-O-C(O)-NH-C(O)CCl3 from C(O)OH, δ∼8-9 for O-C(O)-NH-C(O)CCl3 from OH]. The method has been successfully applied to quantitative determination of the end-groups of a wide variety of oligomeric polyesters. It has also been applied to higher molecular weight polyesters including commercial, bottle grade, poly(ethylene terephthalate) (PET) and PET based copolyesters (e.g. PETG). 相似文献
2.
The paper describes the synthesis of N-2/4-toluyl methacrylatoethyl carbamates using 2/4-toluyl isocyanate and 2-hydroxyethyl methacrylate. Homopolymerisation and copolymerisation of these novel monomers with methyl methacrylate was carried out using benzoyl peroxide as an initiator and tetrahydrofuran as solvent. Photopolymerisation of N-4-toluyl methacrylatoethyl carbamate could be carried out without the use of photosensitiser. Structural characterisation of copolymers was done using 1H-NMR. Thermal stability of copolymers was evaluated in a nitrogen atmosphere by dynamic thermogravimetry. 相似文献
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4.
Environmental etch damage to automotive coatings, and scratch and mar of these coatings are an important element of customer satisfaction as well as a significant warranty repair consideration for automotive companies. The conditions that result in environmental etch are examined and a laboratory test proposed. Data from this test are compared to automotive hoods exposed in Florida. The performance of various crosslinking chemistries is discussed and the requirements for improved environmental etch are outlined. Scratch and mar performance of these systems is also reviewed. We have found that coatings respond to physical stress by elastic recovery, by plastic flow and by brittle fracture. Classifying types of damage in this way is important for understanding the chemistry needed for improved scratch and mar of coatings. 相似文献
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6.
Emulsion polymer isocyanate (
), polyvinyl acetate (
) and resorcinol-formaldehyde (
) adhesives were used to produce single lap shear specimens using resinous and non-resinous apitong (Dipterocarpus spp.) timbers. Tests showed that joints made with highly resinous apitong were about 40% weaker than similar joints made with non-resinous apitong. The resinous apitong was treated with different solvents to yield five different extractives which were characterized by infra-red analysis. Apitong extractives were then added to
and
adhesives and joints made with buna (Fagus crenata), a timber known to be low in extractives and easy to bond. Joints prepared using extractive-containing adhesives were generally weaker than those made with the unmodified adhesives. RF adhesives containing extractives cured more slowly than unmodified
. It is thought that the acidic nature of the extractives changes the pH of the system sufficiently to affect the curing mechanism 相似文献
7.
全水发泡硬质聚氨酯泡沫塑料技术研究进展 总被引:12,自引:1,他引:12
对CFC 11发泡替代技术中全水发泡技术路线进行了分析 ,指出水作为发泡剂存在的优点与不足。着重阐述了全水发泡中几种主要因素如水的用量、聚醚多元醇性质和结构以及异氰酸酯指数对泡沫性能的影响 ,并对国外近些年来全水发泡用聚醚多元醇研究现状进行了详细论述 相似文献
8.
采用有机无机复合的方式,制得异氰酸酯增强的SiO2气凝胶。将硅酸甲酯(TMOS)、甲基三甲氧基硅烷(MTMS)、3-氨丙基三乙氧基硅烷(APTES)配成混合硅源,经水解缩聚后形成凝胶,老化后浸泡在含六亚甲基二异氰酸酯单体(HDI)的乙腈溶液中,最后经CO2超临界干燥,获得了具有良好机械性能的SiO2气凝胶。制备过程中引入的MTMS增加了凝胶与有机物间的浸润性,与使用有机物低聚体相比,使用单体可使有机物更易进入凝胶网络,反应更充分,形成纳米尺度更均匀的复合气凝胶。复合后的气凝胶密度为330 mg/cm3、比表面积为446.3 m2/g、热导率为0.068 W•m-1•K-1,该气凝胶良好的力学性能(压缩强度为19.96 MPa、压缩模量为82.37 MPa)使气凝胶的机械加工成为可能。 相似文献
9.
10.
TPU增韧改性POM的研究 总被引:1,自引:0,他引:1
利用双螺杆挤出机制备了聚甲醛(POM)/热塑性聚氨酯弹性体(TPU)和POM/TPU/异氰酸酯预聚物(Z)共混物.采用力学性能测试方法、偏光显微镜(PLM)、傅立叶转换红外线光谱 (FTIR)、扫描电子显微镜(SEM)等研究了共混物的力学性能、结晶行为及形态结构.结果表明,不同种类TPU增韧的共混物的缺口冲击强度和断裂伸长率都随TPU含量的增加而增加,TPU(95A)增韧的POM/TPU共混物的刚性较好,TPU(250)增韧的POM/TPU共混物的韧性较好;Z能促进TPU在基体树脂中的均匀分散,增强两相界面的粘结力,并能细化球晶. 相似文献