Soundproofing and Mechanical Properties of Nanofiller-reinforced Polypropylene Composites

Abstract

Noise generally refers to unwanted sound or sound pollution which can cause serious harm to the human body and society. To prevent noise with sound absorbing materials has attracted much attention in many engineering fields nowadays. Recently, polymer absorbing materials have been fabricated for soundproofing application in many aspects of daily life. The advantages of such polymer absorbing materials are their high performance on soundproofing effect and internal properties such as light weight, specific strength, and low cost.

A kind of nanocomposite with clay reinforced polypropylene (PP) has been developed in order to investigate and understand its soundproofing and mechanical property. Clay is used as the reinforcement filler due to its nanometer dimension layered silicate which can dramatically change the mechanical and other performances at even very low filler concentration after homogeneous dispersion inside the host matrix. PP is used as the matrix material due to its attractive combination of low density and high heat distortion temperature.

The specimens made of this PP/Clay composites by injection molding machine are tested for their soundproofing property through impedance tube for sound transmission loss (TL) measurement. An optimum concentration of clay for proper performance ratio inside PP matrix is investigated in detail. Soundproofing property of pure PP, PP/Clay(0.9wt%), PP/Clay(4.8wt%), PP/Clay(6.5wt%) composites is discussed as a function of clay content with 29mm diameter specimens for high sound frequency. The soundproofing efficiency increases with clay content increasing from 0 to 6.5wt%. Compared with pure PP, average 8~20dB sound TL increases for PP/Clay(6.5wt%) composites at 3200~6400Hz. In general, 6.5wt% clay is the optimal amount for reinforcement to PP and this PP/Clay(6.5wt%) composite shows the best soundproofing. For mechanical properties, more clay filler specimens have higher storage modulus and loss modulus which can show better plastic property.

A mathematical equation for expressing the affecting factors of soundproofing property is developed with variables of sound frequency and clay weight percentage. Moreover, this equation shows perfect fitting curves which are similar to the results from experiment data. In addition, this kind of PP/Clay composites can be used for real products fabrication such as relay package and automotive interior parts.