Thermal Properties Of Aliphatic Polyester Polyester(PBS、PLA) Composite Modified By Boron Nitride And Sepiolite

The use of synthetic nondegradable polymers has led to a series of serious environmental pollution,a hot issue is to exploit the functionalized biodegradable materials to ease pressure on the environment.Research of composite materials has focused on modifying the polymer with inorganic particles to prepare material with excellent performance that general engineering material fails to attain. In this thesis, polybutylene succinate(PBS), polylactide(PLA) matrix were blended with micron hexagonal boron nitride(h-BN) and sepiolite(SP) particles respectively. Inorganic/aliphatic polyester composites were prepared through melt blending and rolling mill process. The reasons of different properties of divergence crystal inorganic modified polyester composites were also analysised. Furthermore, the h-BN and SP particles were treated with coupling agent KH550 and KH560. The influence on crystal types, fracture morphologies, thermal and mechanical properties of PBS-based and PLA-based composites by the inorganic particles films was investigated. The conclusions of this study were as follows:1. The influence on properties of polyester-based composites modified by h-BN and SP particles1) Compared with pure PBS, the tensile properties and elongation at break of the h-BN/PBS and SP/PBS composites were enhanced.With the exaltation of h-BN and SP content, tensile strength and elongation at break first were increased and then decreased. When the h-BN, SP contents were 6wt% and 2wt%, the comprehensive mechanical properties are optimal. However, when the amount of h-BN and SP particles were higher, mechanical properties of the composite material were declined due to reunion phenomenon.2) Compared with PLA, with the exaltation of h-BN and SP content, the tensile properties of the h-BN/PLA and SP/PLA composites first were increased and then decreased, and elongation at break were decreased. When 10wt% thermoplastic polyurethane(TPU) was added to PLA, tensile strength of composites almost remain the same, but elongation at break increased significantly. Furthermore, when blended with h-BN or SP particles significantly improved, the compatibility of ternary blends composite was significantly improved.2. The influence on properties of polyester-based composites modified by h-BN and SP particles handled by KH550 and KH560 coupling agent1) When KH550, KH560 was grafted on h-BN and SP particle surface,the compatibility between particles and the PBS substrate was improved, and agglomerate phenomena had been obviously improved. Furthermore PBS crystal shape was not changed with the addition of h-BN, SP particles. Compared with PBS, elongation rate at break and tensile strength of composites was obviously improved. The comprehensive mechanical and thermal properties of composite materials were optimal, when KH550 handled h-BN and SP content was 6wt% and 3wt% respectively. However, when the content is higher, particles in PBS matrix may reunite.2) When h-BN and SP particle were treated by KH550 and KH560, the compatibility between particles and the PLA substrate was also improved.In addition the crystal structure of PLA was not changed with the addition of h-BN and SP particles. With the count of h-BN and SP increased, elongation rate at break and tensile strength of composites showed increased and then decreased. When KH550 treated h-BN and SP content were 3wt% and 2wt% respectively, the comprehensive mechanical and thermal properties of composite materials were optimal. However the content is higher, agglomerate phenomena may occur in PLA matrix.3. The thermal decomposition dynamics research of h-BN and SP/polyester composite1) The PBS, PLA/TPU-based composites’ thermal stability were increased with the addition of modified h-BN and SP particles. Because the thermal decomposition temperature of h-BN and SP particles is too high, thus polyester-based composite material only occurs own thermal decomposition. When the h-BN-KH560 dosage is 3wt%,the thermal property of PBS was optimal.Thermal decomposition kinetics show that PBS matrix composites’ apparent activation energy was improved 24.62 k J/mol adding h-BN, and ln A increased. When the SP-KH550 dosage is 3wt%, the thermal property of PBS was optimal. The apparent activation energy of PBS composites was improved 24.48 k J/mol, and ln A had no significant change.2) PLA composites thermal decomposition process had PLA and TPU two stages in the thermal decomposition, respectively. When h-BN-KH560 dosage is 4wt%, the thermal property of PLA was optimal. The apparent activation energy of composites was improved 25.49KJ/mol, and ln A increased. When the SP-KH550 dosage is 3wt%, the thermal property of PLA-based composites was optimal. The apparent activation energy of composites was slightly increased.3) The results show that h-BN, act as nucleating agent in the polyester matrix, accelerated the crystallization rate. PBS polyester grain refinement was obtained as well as PLA. Furthermore, the composites thermal stability was improved duing to the development of polyester crystallinity. While the SP nucleation effect was not so dramatic, it merely served as inorganic high temperature reinforced material and enhanced the system thermal stability.