Preparation And Properties Of Ablative Polysiloxanes Materials

Polysiloxane-based materials have a good prospect in the field of ablative materials.In this thesis,ablative polysiloxane-based materials and modified ablative polysiloxane-based materials were prepared using polysiloxanes as a matrix polymer.Triethoxysilyl-terminated polysiloxanes were synthesized.The structure and molecular weights of triethoxysilyl-terminated polysiloxanes were characterized by FT-IR,'H NMR and GPC.The bulk viscosity of triethoxysilyl-terminated polysiloxane was 9.42 Pa s(10 r/min,25 C).Ablative polysiloxane-based materials were prepared by hydroxyl-terminated polysiloxanes and silica,calcium carbonate or Filler H.The mechanical properties,thermostability,ablation properties and char structure of ablative polysiloxane-based materials were characterized by TGA,gas-oxygen torch test,SEM,XRD and FT-IR.The TGA results showed that thermostability of the prepared ablative polysiloxane-based materials containing Filler H decreased.The ablation rates of ablative polysiloxane-based materials were tested by gas-oxygen torch test method(960 C).The results showed that fillers of silica and calcium carbonate decreased the ablation rates of the ablative polysiloxane-based materials.When calcium carbonate content was 40 phr,the ablation rate was 3.12 mm/min.When Filler H was used to prepare polysiloxane-based materials(CAPS-H),the ablation rate of CAPS-H increased.However,the ablation rate of CAPS-H became decreasing when the content of Filler H was more than 20 phr.The maximum ablation rate of CAPS-H was 11.88 mm/min.Lamella structure and rodlike structure were found in the chars of ablated polysiloxane-based materials containing silica and calcium carbonate.The chars formed a layer to prevent heat and flame.This char decreased the ablation rates of the prepared materials.A loose and fragile char was formed when CAPS-H was ablated.Triethoxysilyl-terminated polysiloxanes was used as the matrix to prepare a kind of modified ablative polysiloxane-based material.The mechanical properties,thermostability,ablation properties and char of the modified ablative polysiloxane-based material were studied by TGA,gas-oxygen torch test,XRD and FT-IR.The results showed that the ablation rate increased when a content of 10 wt%modified agent was used.The maximum ablation rate was 10.0 mm/min and the formed char was loose.Silica used as a filler could significantly decrease the ablation rate of modified ablative polysiloxane-based material.Two additives were studied to regulate the ablation rate of the modified ablative polysiloxane-based materials.