Preparation And Properties Of Polyphenylene Oxide-based Composites With Low Dielectric Constant

With the development of mobile communication technology to a new generation, the world has raised the technical requirements for each communication industry chains;significantly,the standards of copper-clad laminates applied for printed circuit board to convey high-frequency and high-rate communication signals has been improved,while the traditional resin copper-clad laminate can not meet the strict requirements.In this context,copper-clad laminates used for high frequency and speed communication need to meet the requirements of low dielectric constant,low dielectric loss,excellent thermal and mechanical strength,suitability for molding processing and etc.Therefore,to devise a new material and conduct research on it to meet the high standards and strict requirements of high frequency and speed era has become a hot and complicated topic in the global related research field.Based on the above background,this paper aimed at studying low-dielectric-constant composites applied as the matrix resin of copper-clad laminates.And in many kinds of copper-clad laminate matrix resin,polyphenylene oxide（PPO）has quite excellent comprehensive performance,showing the ideal thermal stability,electrical insulation and mechanical strength,and the most important point is that PPO possesses low dielectric constant and dielectric loss.However,the application of polyphenylene oxide resin in the field of copper-clad laminates is faced with many problems,for example,polyphenylene oxide as a thermoplastic resin soluble in organic solvents,does not meet the requirements of the production process of copper-clad laminates;Secondly,polyphenylene oxide has most of the common problems of polymer materials,such as poor thermal conductivity and its flame retardancy is not high enough;in order to meet the requirements of production and processing,it is bound to need to improve the polyphenylene oxide materials applied for copper-clad laminates.Therefore,this paper focuses on the design and preparation of polyphenylene oxide composites to meet the requirements of high-frequency and high-speed mobile communication technology.The detailed researching work is as follows:First,polyphenylene oxide was cross-linked by hot pressure with dicyclopentadiene epoxy resin（DCPD）.Thermodynamic analysis（TGA and DSC）and dielectric property analysis were used to explore the optimal mixing ratio of polyphenylene oxide and epoxy resin.The results showed that,Sample（PPO:DCPD=60 wt%:40wt%）as the best resin mixing ratio had good curing reactivity under the premise of maintaining excellent dielectric properties.At the same time,in order to improve the thermal conductivity of the resin,the hexagonal boron nitride filler was added,and the thermoplastic polyphenylene oxide was successfully synthesized into thermosetting polyphenylene oxide composites.The dielectric properties and thermal conductivity of composite materials were studied.The results revealed that the composites had good electrical insulation,thermal conductivity with low dielectric constant.Sample PPO-DCPD2-HBN2 displayed the best comprehensive performance,and the dielectric constant and dielectric loss maintained at 3.32 and 0.0077respectively at 10⁴Hz,which could be a low loss material in line with the requirements of high-frequency-and-speed era.And its thermal conductivity reached0.51 W·m^-1·K^-1,2.1 times higher than that of common thermoplastic polyphenylene oxide.In order to improve the performance of the composite,hexacylglyceryl cyclotriphosphonitrile（HGCP）with multiple reactible functional groups was synthesized from phosphonitrilic chloride trimer and Oxiran-2-ylmethanol.Using it as a part of the resin matrix could be conducive to the completion of crosslinking reaction and improving the peeling strength.Several groups of composite samples and copper-clad laminates were prepared according to different proportions of hexamethylene glyceryl cyclotriphosphonitrile.Among them,sample PPO-DCPD-HGCP4-HBN and its copper-clad laminate showed the best comprehensive properties,with dielectric constant and dielectric loss of 3.72 and 0.0075（10⁴Hz）,peeling strength of 3.2 N/mm,oxygen index of 30.2%,and UL-94 grade of V-0.These results indicated that polyphenylene oxide composites containing HGCP may provide a new idea for the development of high performance copper-clad laminates.