Evaluation of imbedded fiber retraction phenomenological models for determining interfacial tension between molten polymers

In this work, the interfacial tension for several polymer pairs, namely polypropylene/polystyrene (PP/PS), PP/polycarbonate (PC), PP/polyamide 6 (PA-6) and low density polyethylene (LDPE) and ethylene vinyl alcohol copolymer (EVOH) was evaluated as a function of temperature using the imbedded fiber retraction method (IFR). Two phenomenological models were used and compared to infer the interfacial tension from the evolution of the imbedded fiber back into a sphere: [Carriere CJ, Cohen A, Arends CB. J Rheol 1989;33:681-9. [1] and Tjahjadi M, Ottino JM, Stone HA. AIChE J 1994;40:385-94. [2]]. It was shown that Carriere et al.'s model overestimates the value of interfacial tension whereas Tjahjadi et al.'s model leads to results that corroborate the ones obtained using other experimental methods. A method to further increase the accuracy of Tjahjadi et al.'s model was proposed. Using this method the interfacial tension for the different polymer pairs studied was evaluated and shown to decrease linearly with increasing temperature.     

Interfacial tension of polycaprolactone/polystyrene blends by the imbedded fiber retraction method

Polycaprolactone (PCL) is a biodegradable polyester that is widely used in blends with synthetic and natural polymers for various applications. PCL is blended with biopolymers such as starch to improve its wet mechanical properties without impairing the biodegradability and other useful properties of starch. In spite of its importance, little is known about the interfacial tension of PCL blends. Indirect estimates of the room‐temperature interfacial tension of PCL blends using wettability methods have been reported. However, direct measurements of the interfacial tension of PCL blends have not been achieved until now, mainly because of the unsuitability of existing equilibrium methods for measuring the interfacial tension of high viscosity blends. We have measured the interfacial tension of PCL/PS blends using the imbedded fiber retraction (IFR) method. The IFR is a dynamic method that allows for the measurement of interfacial tension of high viscosity polymer blends in a relatively short period of time. The interfacial tension of PCL/PS blends was measured from 160 to 200°C. In this temperature range, the interfacial tension of PCL/PS blends is independent of temperature and has a value of 7.6 ± 1.8 dyn/cm. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3145–3151, 2002; DOI 10.1002/app.10178     

Comparison between five experimental methods to evaluate interfacial tension between molten polymers

In this work, an experimental comparison between five different techniques to measure interfacial tension between molten polymers is presented. The five techniques include two equilibrium methods: the pendant drop (PD) and the sessile drop (SD); two dynamic methods: the breaking thread (BT) and imbedded fiber retraction (IF); and a rheological method based on linear viscoelastic measurements of the blend (RM). The polymer pairs studied were polystyrene/polypropylene (PS/PP); and PP/high density polyethylene (PP/HDPE). It was possible to determine the interfacial tension between PP/PS with all the methods tested and the results corroborated within 20%. However, the interfacial tension between PP and HDPE could be evaluated only using rheological methods because of a too‐small difference of index of refraction between both polymers. The experimental precision increased in the following order: RM < SD < BT < IF < PD. The rheological method had the advantage of being simpler and faster than dynamic and equilibrium methods. However, when using the rheological method, care should be taken because the results obtained may depend upon the concentration of the blend used for the measurements. It was observed that the pendant drop and breaking thread methods cannot be used for polymers with high viscosity (above 5 × 10⁵ Pa.s).     

Interfacial tension measurement between immiscible polymers: improved deformed drop retraction method

This paper describes an improvement of the technique to measure interfacial tension in immiscible polymer blends. Our method is based on the droplet retraction method, in which one relates the kinetics of relaxation of a deformed droplet to the interfacial tension between the matrix and droplet. Previously, the problem with this technique has been the difficulty in preparing axisymmetric ellipsoidal droplets. In our work, we demonstrate that perfect axisymmetric ellipsoidal droplets are produced at a later stage of relaxation of short imbedded fibers. With this technique, we utilize the strengths of both the deformed droplet method and the imbedded fiber retraction method while overcoming their shortcomings. The interfacial tension value thus obtained was compared to that by conventional methods. Additionally, the effect of confinement by external walls on the interfacial tension measurement was studied. Confinement affects interfacial tension measurement when the gap between the walls is less than two times the equilibrium drop size.     

Determination of interfacial tension between PA/PP and LCP/PP by IFR method and effect of compatibilization on interfacial tension

The dynamic imbedded fiber retraction (IFR) method was used to measure the interfacial tension between two molten polymers. The aim was to evaluate the applicability of this method for polypropylene (PP) used as matrix, and two polyamide (PA6, PA66) and thermotropic main-chain liquid crystalline polymer fibers. The effect on the interfacial properties of modifying the PP matrix with compatibilizers was studied as well. The IFR method was found to be suitable for evaluating the interfacial properties of these polymer blends. The measured interfacial tensions correlated well with the morphology and mechanical properties of the blends and values calculated from the harmonic mean equation. Although the measured interfacial tensions were generally lower than the theoretical ones, the order of the values for the different polymer pairs was similar. © 1995 John Wiley & Sons, Inc.     

相容剂对聚丙烯/聚酰胺体系界面张力的影响

采用断裂纤维丝线法和变形液滴回缩法两种方法相结合,在线观察聚酰胺6(PA6)液滴在聚丙烯(PP)中的回缩过程,研究不同相容剂对该体系界面张力的影响。结果表明,PA6液滴在剪切场下发生变形,然后在界面张力的作用下逐渐回缩成球形,并测得该体系的界面张力为7.16 mN/m。添加相容剂可以显著降低体系的界面张力。不同相容剂[聚丙烯接枝马来酸酐(PP-g-MA)、聚丙烯接枝丙烯酸(PP-g-AA)、氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)]对体系界面张力影响不同,满足以下关系:γ_(PP/PA6)>γ_(PP/SEBS/PA6)>γ_(PP/PP-g-AA/PA6)>γ_(PP/PP-g-MAH/PA6)。     

改性海泡石与金属氧化物对膨胀阻燃PP燃烧性能的影响

采用极限氧指数、垂直燃烧、TGA、FTIR和SEM等方法研究了改性海泡石(SP)及金属氧化物(ZnO、Ni2O3)对聚丙烯(PP)/马来酸酐接枝三元乙丙橡胶(EPDM-g-MAH)/膨胀阻燃剂(IFR)体系燃烧性能的影响。极限氧指数和垂直燃烧结果表明:SP及金属氧化物均对IFR有一定的协效作用,能提高体系的极限氧指数和阻燃性能。TGA结果表明:SP可以提高燃烧残余炭层的稳定性和残炭率。SEM观察表明:SP与ZnO复配体系的燃烧残余炭层更致密和连续。FTIR测试发现SP、金属氧化物促进了IFR在PP体系中的交联成炭作用,较快生成连续的保护性炭层。     

Fabrication of barium titanate nanoparticles‐epoxy resin composite films and their dielectric properties

A method for fabricating epoxy resin films dispersing the surface‐modified barium titanate (BT) particles (BT‐epoxy resin composite films) are proposed. BT particles with a size of 7.8 nm and a crystal size of 8.6 nm were synthesized with a complex alkoxide method. To introduce epoxy groups on the BT particle surface, the BT particles were surface‐modified with 2‐(3,4‐epoxycyclohexyl)‐ethyltrimethoxysilane. A precursor solution, which was prepared by prereacting 2,2‐bis(4‐glycidyloxyphenyl)propane (BGPP) and phthalic anhydride in 4‐butyrolactone and adding the surface‐modified BT particles to the prereacting solution, was spin‐coated on glass substrates to fabricate the composite films. An increase in BT volume fraction in film increased dielectric constant of the composite film while keeping dissipation factor below 0.03. The dielectric constant attained 10.8 at a BT volume fraction of 30% in film that was around twice higher than pure epoxy resin film. POLYM. COMPOS., 31:1179–1183, 2010. © 2009 Society of Plastics Engineers     

纳米SiO2改性PE-Xa记忆环的制备及性能研究

主要针对普通过氧化物交联聚乙烯(PE-Xa)记忆环回缩慢、回缩力小、安全可靠性差等问题,制备出一种新型纳米二氧化硅(SiO₂)改性PE-Xa记忆环。首先研究了交联度对记忆环性能的影响,结果表明,记忆环回缩速度和回缩力均随交联度的提高而提高。其次研究了纳米SiO₂的表面处理及添加量对记忆环性能的影响,结果表明,采用硅烷偶联剂KH-570对纳米SiO₂进行表面处理,并且在线速度1 km/min以上的超高速搅拌下混合,纳米SiO₂的分散性较好。添加1.5%表面处理的纳米SiO₂能大幅提高记忆环回缩速度、回缩力和抗蠕变性能。对制备的记忆环进行性能测试,其回缩速度,回缩力均优于市售记忆环,且通过了交联聚乙烯(PE-X)管标准中规定的静液压状态下的热稳定性试验和系统适用性中规定的静液压试验。     

Studies on some factors influencing the interfacial tension measurement of polymers

To improve the accuracy of polymer interfacial tension measurement using deformed drop retraction method (DDRM), we examined some factors, such as the shape parameter, the retraction scale D₀, and the distortion criterion γ by means of dissipative particle dynamics (DPD) simulation with 6 different models and analysis with three observation data, and proposing a new shape parameter P. Results show that the shape parameter order of suitable to various retraction scales and larger distortion is P>(a²−b²)>D. This study found that choosing a suitable retraction scale is very important, and that D₀≅0.15 is the most suitable retraction scale in DDRM measurement. In the scale, the three shape parameters cannot make much difference on the measurement deviation from the standard. This study also found that the distortion criterion γ varies with different shape parameters. We also found here when D₀≅0.15 the distortion criterion becomes γ<0.15, and one has a reliable measurement with any shape parameter.     

Influence of polymer–filler interactions on retraction behaviors of natural rubber vulcanizates reinforced with silica and carbon black

In general, silica‐filled rubber compounds contain a silane coupling agent to improve the filler dispersion and polymer–filler interactions. The silane coupling agent modifies the silica surface and makes crosslinks between the rubber and the silica. Influence of the modification of silica on the retraction behaviors of natural rubber (NR) vulcanizates reinforced with silica and carbon black was studied. Variation of the retraction behaviors of NR vulcanizates with filler composition was also investigated. The vulcanizates containing the silane coupling agent were recovered faster than those without the silane coupling agent. The recovery difference between the vulcanizates without and with the silane coupling agent increased with increased silica content. For the vulcanizates containing the silane coupling agent, the retraction behaviors were nearly the same, irrespective of filler composition. But, for the vulcanizates without the silane coupling agent, the vulcanizate was recovered more and more slowly as the silica content increased. The experimental results are explained with the polymer–filler interactions, modification of silica surface, and formation of crosslinks between silica and rubber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 691–696, 2006     

改性聚磷酸铵对三嗪类膨胀阻燃聚丙烯性能的影响

由改性聚磷酸铵(APP)、自制的三嗪类成炭发泡剂(CFA)等复配制成膨胀型阻燃剂(IFR),以二氧化硅、二氧化钛等为协效剂阻燃聚丙烯(PP)。研究了不同组分的IFR及协效剂对阻燃PP复合材料阻燃性能、力学性能和耐水性能的影响。结果表明:改性APP的亲水性下降;由改性APP/CFA(4/1)、二氧化硅协效剂复配的PP复合材料阻燃性能、力学性能优良,助剂在PP基体中分散性好,热水浸泡后氧指数为32.5%,仍能达到UL94V—1级,失重率为2.92%。     

Modification of lignin and its application as char agent in intumescent flame‐retardant poly(lactic acid)

Urea‐modified lignin was prepared according to the Mannich reaction and well characterized by Fourier transform infrared spectrometer, elemental ananlyses, and scanning electron microscopy (SEM). Ammonium polyphosphate (APP) and urea‐modified lignin were added into poly(lactic acid) (PLA) as a novel intumescent flame‐retardant (IFR) system to improve flame retardancy of PLA. The flammability of IFR–PLA composites was studied using limiting oxygen index, UL‐94 vertical burning method and cone calorimeter test, and their thermal stability was evaluated by thermogravimetric analysis. The results showed that the urea‐modified lignin combined with APP exhibited much better flame retardancy and thermal stability than that of the combination of virgin lignin and APP. The improvement may be attributed to the better char morphology with more phosphoric char evidenced by SEM and X‐ray photoelectron spectroscopy. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Synergistic effect of organophosphate functionalized montmorillonite on properties and water resistance of intumescent flame‐retarded SEBS

Polystyrene‐b‐(ethylene‐co‐butylene)‐b‐styrene (SEBS) is a widely used thermoplastic elastomer. However, it suffers from poor flame retardancy. Proper combination of organic‐modified montmorillonite and intumescent flame retardant (IFR) works but is not stable due to easy absorption of moisture. In this study, a novel and stable halogen‐free flame‐retardant system is demonstrated by encapsulating a hydrophobic organophosphate, ie, bisphenol A bis (diphenyl phosphate) (BDP) into a stable micelle and then “attaching” the BDP micelles to the montmorillonite (called: side‐intercalation). The resulted BDP modified montmorillonite (BMMT) has a large inter‐platelet spacing and demonstrated synergistic effect with IFR on flame retardancy, tensile property, and water resistance for the composite with SEBS. In addition to more homogeneous dispersion of IFR and BMMT, a longer‐lasting interfacial interaction between IFR and SEBS matrix with addition of small amount of BMMT also plays the role. The results suggest that BMMT can serve as an effective additive for formulating novel halogen‐free flame retardants for the SEBS to meet increasingly stricter environmental requirements.     

Study on flame‐retardancy and thermal degradation behaviors of intumescent flame‐retardant polylactide systems

Two intumescent flame‐retardant (IFR) additives, IFR‐I and IFR‐II, were synthesized and their structure was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Polylactide (PLA) was modified by the two IFRs to obtain flame‐retardant composites. The flammability of the PLA/IFR composites was characterized by the vertical burning test UL‐94 and limiting oxygen index. The limiting oxygen index values of the PLA composites increased with increase of IFR content. The PLA composite with 20 wt% IFR‐I could pass the UL‐94 V0 rating, while the composite with 30 wt% IFR‐II could not. The results of pyrolysis combustion flow calorimetry showed that the heat release capacity of PLA composites with 30 wt% IFR‐I decreased 43.1% compared with that of pure PLA. The thermal degradation and gas products of PLA/IFR‐I systems were monitored by thermogravimetric analysis and thermogravimetric analysis infrared spectrometry. Scanning electron microscopy was used to investigate the surface morphology of the char residue. Copyright © 2011 Society of Chemical Industry     

The surface modification of BaTiO3 and its effects on the microstructure and electrical properties of BaTiO3/silicone rubber composites

Interfacial interaction and compatibility between the ceramic dielectric and polymer matrix have strong impact on the dielectric constant and dielectric loss of their composites. In this work, the BaTiO₃ (BT) nanoparticles were modified by (1) stearic acid (SA); (2) aluminate coupling agent (ACA); (3) the combination of SA and coupling agent aluminate, and then incorporated them with silicone rubber (SR) matrix to prepare BT/SR nanocomposites. The effects of the surface modification methods of BT on the microstructure and electrical properties of BT/SR nanocomposite films were studied. The results showed that SA and ACA were beneficial to the dispersion of BT and resulted in the strong interfacial interaction. The composite of BT modified by SA not only had high dielectric constant of 10.5, 2 times higher than that of the unmodified BT/SR nanocomposite (4.7), at the same time showed lower dielectric loss. J. VINYL ADDIT. TECHNOL., 24:288–294, 2018. © 2017 Society of Plastics Engineers     

不同膨胀型阻燃剂改性聚丙烯/聚乳酸复合材料

用两种不同的膨胀型氮磷阻燃剂(IFR1和IFR2)阻燃改性聚丙烯(PP)/聚乳酸(PLA)复合材料。结果表明:两种阻燃剂在PP/PLA基体中都具有良好的分散性和界面粘合性。阻燃剂的加入降低了材料的力学性能,而含有25%阻燃剂的PP/PLA复合材料就能到达垂直燃烧试验(UL-94)的V0等级。燃烧过程中阻燃剂通过在材料表面形成致密的炭层来提高材料的阻燃性,其中IFR1对PP/PLA体系的阻燃改性效果更好。从力学性能和阻燃效果的双重考虑,质量含量25%的阻燃剂适合于PP/PLA材料的阻燃改性。     

硅烷偶联剂在膨胀阻燃聚丙烯复合体系中的应用

用乙烯基硅烷偶联剂(A-172)对膨胀阻燃剂(IFR)进行表面改性,研究了该阻燃剂对聚丙烯(PP)体系力学性能和阻燃性能的影响。结果表明:当A-172/IFR/PP为0.5/22.5/77.5时,体系的力学性能基本不变,但阻燃性能得到了改善。其中氧指数同比提高了22.5%,体系的热释放速率峰值和烟释放速率峰值同比分别下降了9.7%和98.75%。     

含磷钛酸酯偶联剂改性膨胀型阻燃剂及其阻燃聚丙烯的研究

采用含磷钛酸酯偶联(剂PTCA)对由三聚氰胺焦磷酸(盐MPP)和季戊四(醇PER)复配组成的膨胀型阻燃(剂IFR)进行表面改性,并用其制备阻燃聚丙烯(PP)。研究了PTCA用量对PP/IFR共混物力学性能和阻燃性能的影响,并通过热重分析和扫描电镜对共混物进行了表征。结果表明:PTCA有效改善了IFR与PP基体的相容性,提高了PP/IFR共混物的力学性能及阻燃性能。当PTCA用量为1.0%时,共混物的拉伸强度和缺口冲击强度为27.3 MPa和3.2 kJ/m2,分别比未改性的PP/IFR提高了18.7%和6.7%;LOI从未改性PP/IFR的28.5%提高到31.5%,且通过UL94 V-0级;此外,共混物的热稳定性也明显提高,700℃时的残炭率由未改性PP/IFR的8.2%提高到12.1%。     

膨胀型阻燃剂在聚丙烯中的应用

对自制的膨胀型阻燃剂(IFR)进行了预处理并添加了协效阻燃剂等助剂,形成一种高效的膨胀型阻燃体系。通过氧指数、热重分析和扫描电子显微镜等检测手段,考察了该阻燃体系的阻燃性能和添加量。IFR、硼酸锌和其他助剂最佳质量比为25：2：2。改进后的膨胀型阻燃体系用于聚丙烯,不仅阻燃性能优良,同时还具有较好的力学性能。