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三元类水滑石化合物的制备及其对PVC的热稳定作用研究
Alternative TitleStudy on Preparation of Ternary Layered Double Hydroxide and its Effect on Thermal Stability of PVC
王公领
Subtype博士
Thesis Advisor王丹
2013-05-01
Degree Grantor中国科学院研究生院
Degree Discipline化学工程
Keyword水滑石   层状复合金属氢氧化物   zn掺杂   pvc热稳定剂   热稳定性能   刚果红试验   热老化试验
Abstract聚氯乙烯(PVC)是世界五大通用树脂之一,具有价廉、强度高、耐腐蚀、难燃烧、绝缘性好、透明性好等优点,广泛应用于建筑、化工、包装等行业。但是PVC分子链上存在不稳定的氯原子,在加工过程中受热易脱出HCl,导致PVC颜色发生变化、物理化学性能下降,因此在加工时必须添加热稳定剂。目前使用的热稳定剂主要有铅盐热稳定剂、有机锡热稳定剂、金属皂热稳定剂等。随着生产生活中人们要求的不断提高,无毒无害、高效、经济的多功能热稳定剂成为人们研究的重点。 类水滑石化合物(LDHs)是一种阴离子型层状化合物,其碱性层板可吸收中和PVC分解释出的HCl,层间CO32-阴离子可与Cl-进行离子交换,抑制HCl的的催化降解作用,从而提高PVC的热稳定性能。LDHs的层板元素组成和层间阴离子种类可调,并且无毒无害、制备方法简便,是一种非常有前途的PVC热稳定剂。 本论文用均相共沉淀法合成了Zn掺杂的MgAl-LDHs。研究了不同实验参数,包括Zn含量、pH值、反应时间和总金属离子浓度对LDHs的结构和性能的影响。将合成LDHs与PVC及其它助剂共混,通过测定共混物的热稳定性能研究了LDHs结构和性能的变化对PVC热稳定效果的影响。 (1)产物的金属元素摩尔比与投料比相符,平均粒径约为90nm,呈片状形貌且结晶性良好。调变实验参数可影响合成LDHs的晶体结构和热稳定性,LDHs层板中Zn的含量以及反应初始pH值的影响较大,而反应时间和原料浓度的影响较小。 (2)向LDHs层板引入Zn元素以及层间水的氢键作用影响了LDHs片层与层间域分子的作用力。在Zn含量增加和更多层间水的综合作用下,LDHs吸收HCl的能力增强,提高了PVC的热稳定性。由于Zn掺杂LDHs与PVC热降解释出的HCl反应所生成的ZnCl2对PVC具有催化降解作用,综合考虑当LDHs层板中的Mg/Zn = 1.0时对PVC的热稳定效果最好。 (3)实验参数pH值、反应时间以及总金属离子浓度可影响LDHs的晶体结构。层板尺寸和层间距的增大提高了LDHs吸收HCl的能力,对PVC的长期热稳定性有明显的提高。综合考虑pH值为10,反应时间24h,总金属离子浓度0.45M时合成的LDHs对PVC的热稳定效果最好。 (4)利用工业原料合成了LDHs,并研究了其对PVC热稳定性能的影响,其对PVC的热稳定效果与用分析纯原料合成的LDHs相当,表明该方法合成相关产品有较好的市场化前景。
Other AbstractAs one of the five general resins world widely used, polyvinylchloride (PVC) pocesses numerous advantages such as cheapness, high mechanical strength, corrosion resistance, flame retardance, good insulation and transparence and is applied in fields including construction, chemical and packing industries, etc. However, due to its unstable chloride atoms in molecular chains of PVC, it is liable to get rid of hydrogen chloride when suffering heat during processing, which results in discolor and degradation of physical and chemical performance. Therefore, it is crucial to add thermal stabilizer during processing. The main species of thermal stabilizers currently used are lead salts, organo-tin compounds and metal soaps. With increasing concerns on human healthiness and environmental protection, recently much attention has been focused on thermal stabilizers for PVC resins with properties of non-toxicity, high efficiency, environmental friendliness and economy. Layered double hydroxides (LDHs) are a kind of anionic type layered clays. Its basic layers can react with HCl gas formed during degradation of PVC, and the interlayer carbonate anions can be ion exchanged with chloride anions, thus inhibiting the catalytic degradation of HCl on PVC and improving the thermal stability of PVC. LDHs can be a kind of promising thermal stabilizer for PVC as its properties of adjustable composition of layers and species of interlayer anions, no-toxic, and simplicity of preparation method. In this thesis, Zn doped MgAl-LDHs were prepared using homogeneous precipitation method. The influences of experimental parameters including the amount of Zn doping, pH value of initial reaction solution, reaction time, and total cation concentration on the structure and properties of LDHs were investigated. The as-prepared LDHs were mixed with PVC and other additives, then the static dynamic thermal stability of the mixture were measured to study the effects of the changes of structure and properties of LDHs on thermal stability of PVC. (1) The molar ratios of as-prepared LDHs are all close to feed ratio. The as-prepared plate-like, well crystallized LDHs have an average particle size of 90nm. Among the experimental parameters, the amount of Zn doping and pH value of initial reaction solution have more influences on the structure and thermal stability of LDHs than reaction time and total cation concentration. (2) As the cationic radius and electronegativity of Zn2+ are larger than that of Mg2+, the interaction forces of layers with interlayer region were affected by the introduction of Zn with into layers and the hydrogen bonding of interlayer waters. The ability of LDHs absorbing HCl was strengthened by the comprehensive effect of increasing amount of Zn in layers and water in interlayer regions, thus improving the thermal effect on PVC. However, ZnCl2 formed by reaction of Zn doped LDHs with HCl can lead to catalytic degradation of PVC. LDHs with Mg/Zn = 1.0 was found to have best thermal stabilizing effect on PVC. (3) Experimental parameters including pH value of initial reaction solution, reaction time and total cation concentration influence the crystal structure of LDHs. The ability of absorbing HCl was enhanced when increasing the lamella size and basal spacing; hence the long term thermal stability of PVC was improved. It was concluded that LDHs prepared at conditions of pH = 10, reaction time 24h, and total cation concentration 0.45M have optimum thermal stabilizing effect on PVC. (4) LDHs were prepared using raw materials of technical grade and its effect on thermal stability of PVC was studied. The thermal stabilizing effect of LDHs prepared from raw materials of technical grade was roughly the same as that of LDHs prepared from analytical grade materials, indicating promising market prospect for scale-up production.
Pages86
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8261
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
王公领. 三元类水滑石化合物的制备及其对PVC的热稳定作用研究[D]. 中国科学院研究生院,2013.
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