Soundproofing and Damping Properties of Polynorbornen Compounds Filled with Large Amounts of Lead Powder

Polynorbornen (PNR) filled with a large amount of lead (Pb) powder was prepared in the presence of aromatic process oils. The mechanical loss tangent (tan δ) and sound transmission loss (TL) were studied for the PNR-Pb compound sheets. The mechanical tanδ, measured as a function of temperature, had a high peak. Although the peak value of tan δ decreased with the increase of Pb content, it still remained at 0.7 for the specimen with 7000 Pb phr. Increased amounts of Pb content shifted the peak to the higher temperature side. The peak frequencies of tan δ of PNR-Pb compound sheets, estimated using the WLF equation, were 2200 Hz and 800 Hz at 5000 and 7000 Pb phrs, respectively. The sound transmission loss (TL) of the sheet was high, i. e., over 30 dB at 500 Hz for the specimen with 9000 Pb phr. The results indicated that TL obeys a mass law, while no coincidence effect appears in the audio frequency region. Furthermore, the extensional strength and Young's modulus were measured at room temperature. The PNR-Pb sheets can be expected to find applications as a material having high damping and good soundproofing.