Rheological, Thermal, and Mechanical Properties of Phosphorus-Containing Wholly Aromatic Thermotropic Liquid Crystalline Polymer-Filled Poly(butylene terephthalate) Composites Zhi Yang, 1 Bo Cao, 1 Jiaming Zhu, 1 Jiabin Shen, 1 Jiang Li, 1 Shaoyun Guo, 1 Yuzhong Wang 2 1 State Key Laboratory of Polymer Materials Engineering, Polymer Research Institute of Sichuan University, Chengdu, Sichuan 610065, China 2 Center for Degradable and Flame-retardant Polymeric Material, Sichuan University, Chengdu 610064, China Phosphorus-containing wholly aromatic thermotropic liquid crystalline polymer (TLCP) reinforced poly(buty- lene terephthalate) (PBT) composites were prepared. Dynamic rheological analysis displayed that the addition of TLCP led to the decrease of the complex viscosity of PBT. While the thermal stability and tensile modulus were found to be increased distinctly, the results of dynamic mechanical analysis, isothermal crystallization, and morphological observation indicated that these changes were related to the rigid chains and in situ fibrillation of TLCP phase, and the interfacial adhesion between PBT and TLCP. POLYM. COMPOS., 33:1432–1436, 2012. ª 2012 Society of Plastics Engineers INTRODUCTION As an important semicrystalline engineering thermo- plastic, poly(1,4-butylene terephthalate) (PBT) has been widely used in automotive, electrical, and other engineer- ing applications because of its good electrical insulation properties, lubricity, water resistance, and good surface appearance, etc [1–3]. However, in some special fields, PBT generally needs to be modified for bearing higher mechanical and thermal performances. The incorporation of mineral fillers has been proved to be an effective method. Kim [4] has stud- ied the properties of carbon nanotube (CNT)-filled PBT composites and found that the tensile strength and the heat distortion temperature (HDT) were increased about 35 and 20%, respectively, by adding 2 wt% CNTs. How- ever, the complex viscosity was increased about 10 times simultaneously at 10 2 rad/s. Similarly, decreased flowabil- ity and molding problems are also emerged with the addi- tion of other inorganic fillers [5–7]. Thermotropic liquid crystalline polymer (TLCP) is considered as a promising option for developing high- performance polymers because of its good thermal sta- bility, high strength and modulus, as well as low linear viscosity [8]. Various types of TLCP have been reported to blend with polypropylene, polycarbonate, and poly(ethylene terephthalate), etc [9–11]. The so- called in situ fibrillation is generally formed as a rigid phase in the polymeric matrix under the shear deforma- tion, leading to the distinct increase of the mechanical and thermal properties. However, different from the case of inorganic filler-filled system, the addition of TLCP generally brings positive assistance to the proc- essability of the matrix. In this study, a phosphorus-containing wholly aromatic TLCP is used for replacing glass fibers as a disperse phase in PBT matrix. The rheological, thermal, and me- chanical properties have been examined as a function of the concentration of the TLCP. EXPERIMENTAL Materials The PBT from DuPont (Crastin S600F10 NC010) has a reported density of 1.3 g/cm 3 and a melt index of 13 g/ 10 min (2308C/2.16 kg). TLCP used in this study was Correspondence to: Jiabin Shen; e-mail: shenjb@scu.edu.cn. Shaoyun Guo; e-mail: nic7702@scu.edu.cn Contract grant sponsor: The National Natural Science Foundation of China; contract grant numbers: 50933004, 51121001. Contract grant sponsor: The Ministry of Education Priority Funding Areas; contract grant number: 20110181130004. Contract grant sponsor: Innovative Research Team in University; contract grant number: IRT. 1026. DOI 10.1002/pc.22270 Published online in Wiley Online Library (wileyonlinelibrary.com). V V C 2012 Society of Plastics Engineers POLYMERCOMPOSITES—-2012