| In recent years,with the development of thermoplastic vulcanizate(TPV)industry,many functional TPV have been gradually introduced to meet the special properties requirements in certain fields.Silicone rubber(SiR)/polyurethane(TPU)thermoplastic vulcanizate(TPSiV)has a very broad prospect in the wearable equipment industry due to its good skin touch feel and coating properties.Based on the viscosity matching,mechanical properties and elastic properties of raw materials,suitable SiR and TPU materials were selected out to prepare TPSiV.By solving the compatibility problems,designing dynamic vulcanization system and process,TPSiV were prepared successfully.The main research contents and conclusions are as follows:(1)In the process of dynamic vulcanization,the viscosities of SiR and TPU are required to be as close as possible in order to achieve a more fully premixed blend and consequently form a fine phase structure.Meanwhile,TPU with stronger mechanical properties and better elasticities is also needed so as to obtain TPSiV with better mechanical and elastic properties.Based on the rheological properties,mechanical properties and elastic properties of raw materials,two types of TPU and two types of SiR were selected out to prepare TPSiV.The viscosity ratio of SiR and TPU at different temperatures ranges from 0.4 to 0.6;the tensile strength of TPU is between 20MPa and 25MPa;the elongation at break exceeds 500%;the tear strength is greater than 150N/mm;the compression set(23?×22h)of the two types of TPU is 21%and 15%,and the hardness is 82A and 89A,respectively.Based on the result of materials selection,TPSiU compatibilized SiR and TPU have achieved some results.It's found that when the concentration of TPSiU,in which the mass ratio of TPU/SiR is 70/30,is 10 phr,the domain size is reduced to 1.2 ?m.However,unlike traditional small molecular weight compatibilizers,TPSiU has a larger molecular weight so that its capacity increasing effect is not so good.(2)Two types of dynamic vulcanization processes were developed-hightemperature sulfurized dynamic vulcanization process and master batch method dynamic vulcanization process.The former was carried out under the premise of full premix.With the vulcanizer(Si-H)/catalyst(Pt catalyst)mass ratio of 10/1,TPSiV with a dispersed phase particle size of 2.5?m was prepared,whose tensile strength,elongation at break and compression set(23?×22h)are 4.1MPa,304%and 27%,respectively.Except tensile strength,all the properties have met the requirements of use basically;The latter improves the utilization rate of Si-H and Pt catalyst by adopting the feeding method of pre-prepared Pt catalyst/SiR master batch and cold sulfurization,reducing the amount of Si-H and Pt catalyst by 50%.And the dispersed phase particle size of TPSiV prepared by this process is about 2.3?m.Compared with high-temperature sulfurized TPSiV,various properties have been improved differently:tensile strength,elongation at break,and compression set(23?×22h)are 5.2MPa,306%and 24%,respectively.However,the biggest problem of this process is its poor repeatability.(3)Based on the comparison of two types of dynamic vulcanization processes,high-temperature sulfurized dynamic vulcanization process with better repeatability was selected out to prepare TPSiV,and the compatibility of TPU and SiR is further enhanced by adding self-synthetic nano-compatibilizer(CDs).As a result,the dispersed phase particle size was reduced to 1.4?m,and the tensile strength,elongation at break,and compression set(23?×22h)have been greatly improved,which are 6.3MPa,338%and 18%,respectively.The results indicate that self-synthetic nano-compatibilizer CDs has a pretty good compatibilizing and reinforcing effect in the system.(4)With reference to foreign TPSiV products,TPSiV/TPU blends with different hardness grade between 60A and 80A are prepared by blending selfmade TPSiV and TPU,which realizes the control of the structure and properties of TPSiV. |
PDF Full Text Request