Polymer physics
Fatima Mustafayeva; Najaf Kakhramanov; Khayala Allahverdiyeva
Abstract
The article presents the results of studies of the influence of aluminum hydroxide concentration on the crystallization process regularities of nanocomposites based on compatibilized polypropylene random copolymer and aluminum hydroxide (PP-R/PPH-g-MAH/Al(OH)3). The isothermal crystallization kinetics ...
Read More
The article presents the results of studies of the influence of aluminum hydroxide concentration on the crystallization process regularities of nanocomposites based on compatibilized polypropylene random copolymer and aluminum hydroxide (PP-R/PPH-g-MAH/Al(OH)3). The isothermal crystallization kinetics of compatibilized polypropylene random copolymer composites containing 1, 3, 5, 10, 20, 30 and 50 wt. % of aluminum hydroxide was determined by the stepwise dilatometry method using the Kolmogorov-Avrami equation. The crystallization behaviors of composites were investigated on an IIRT-1 device converted into a dilatometer, in the process of stepwise cooling of samples under a load of 5.3 kg. In this study, maleic anhydride functionalized homopolypropylene (PPH-g-MAH) was employed as a compatibilizer to enhance the compatibility between the PP-R and Al(OH)3. Considering the dependence of specific volume and free specific volume on temperature, the first-order phase transition was established and the glass transition temperature values of the composites were determined. The mechanism of formation and development of crystallization centers in the region of the first-order phase transition was investigated. The obtained values of “n” prove that the mechanism or nature of the growth of crystallization centers changes into three-dimensional spherulitic - two-dimensional disc-shaped - one-dimensional rod-shaped with an increase in the amount of aluminum hydroxide in composite. The study of the temperature dependence of the specific volume for the studied samples showed that the first order phase transition occurs at a temperature of 125°C. It was determined that the second order phase transition temperature (the glass transition temperature determined by the dilatometric method) increases with the increase in the amount of filler.
Wei Wang; Shuzhang Qu; Xinwei Li; Jian Chen; Xiaolei Wang; Cui Zheng; Min Guo; Ying Wang
Abstract
Cyclic olefin copolymer is a type of high-performance polyolefin material, which is prepared by using a single-site catalyst in solution polymerization. The common activator of this system is alkyl aluminoxane or organic boron/aluminum system. Among them, organic boron is mostly triphenylcarbenium ...
Read More
Cyclic olefin copolymer is a type of high-performance polyolefin material, which is prepared by using a single-site catalyst in solution polymerization. The common activator of this system is alkyl aluminoxane or organic boron/aluminum system. Among them, organic boron is mostly triphenylcarbenium tetrakis(pentafluorophenyl)borate or dimethylanilinium tetrakis(pentafluorophenyl)borate. In this study, ethylene and norbornene were copolymerized with metallocene catalyst activated with the combination of tris(pentafluorophenyl)boron and triisobutylaluminium. Compared with homopolymerization of ethylene, copolymerization shows high activity. The molecular weight of the polymer increased significantly with the increase of the insertion rate of norbornene. Fineman-Ross method was used to calculate the reactivity ratio, which showed that the reactivity ratio of norbornene was much lower than that of ethylene. The high copolymerization activity may indicate that, although norbornene has a lower coordination probability, its insertion rate is higher than ethylene. The copolymer with higher norbornene incorporation has a higher glass transition temperature, and the relationship between them is linear.
Catalysis
Lei Cui; Ji-Xing Yang; Yan-Guo Li; Yue-Sheng Li
Abstract
Novel cyclic olefin polymers (COPs) derived from bulky cyclic olefins, tricyclodipentadiene (TCPD) and tricyclo[6.4.0.19,12]-tridec-10-ene (TTE), with high glass transition temperature (Tg), excellent thermal stability, and high transparency, have been synthesized by ring-opening metathesis polymerization ...
Read More
Novel cyclic olefin polymers (COPs) derived from bulky cyclic olefins, tricyclodipentadiene (TCPD) and tricyclo[6.4.0.19,12]-tridec-10-ene (TTE), with high glass transition temperature (Tg), excellent thermal stability, and high transparency, have been synthesized by ring-opening metathesis polymerization (ROMP) and subsequent hydrogenation. ROMP of TCPD and TTE was carried out successfully without gel formation using a WCl6/i-Bu3Al/Et-OH/hexene catalyst system at room temperature. By changing the TCPD/TTE molar ratio, the optimized catalyst component ratio for the polymerization varied. Chemical structures of the unsaturated and hydrogenated polymers were characterized by 1H NMR technique. Thermal properties of these newly synthesized polymers were determined using TGA and DSC measurements. The degradation temperatures (Td) were all above 420°C in N2, indicating that all these copolymers had excellent thermal stability. After hydrogenation, Tg of ROMP polymers was decreased by 30-60°C. The Tg of h-pTCPD reached as high as about 230°C. The light transmittances of these polymer films were also analyzed using UV-Vis absorption spectroscopy. A high light transmittance of up to 92% was found by UV-Vis absorption spectra for these polymer films.
