Polypropylene-lignocellulosic material composites as promising sound absorbing materials

Abstract

Polypropylene-lignocellulosic material composites as promising sound absorbing materialsSummary -Composites made from polypropylene and lignocellulosic materials derived from plants were subjected to acoustic and mechanical investigations. Sound absorption coefficients for these composites were measured using the acoustic standing wave method in the frequency range from 1000 to 6500 Hz. This work shows that the frequency dependence of the sound absorption coefficient obtained for pure polypropylene can be modified by proper choice of the filler added to the polypropylene matrix. Fillers derived from hemp plant cause significant increase in the absorption coefficient starting from the frequency above 3000 Hz. The fillers obtained from rapeseed straw, beech and flax are recognized to suppress the sound in the frequency range from 3000 to 4000 Hz. The investigated composites can be recommended for application in the automotive industry and building as the construction materials absorbing the undesired noise. KOMPOZYTY POLIPROPYLENU Z NAPE£NIACZAMI LIGNOCELULOZOWYMI JAKO MATE-RIA£Y POCH£ANIAJ¥CE D WIÊKStreszczenie -W pracy przedstawiono wyniki badañ w³aoeciwooeci akustycznych i mechanicznych kompozytów z³o¿onych z matrycy polipropylenowej i materia³ów lignocelulozowych uzyskanych z rooelin konopi, lnu, rzepaku i drzewa bukowego. Wspó³czynnik poch³aniania dŸwiêku wyznaczono metod¹ akustycznej fali stoj¹cej w zakresie czêstotliwooeci od 1000 do 6500 Hz w uk³adzie pomiarowym Standing Wave Apparatus 4002 firmy Brüel&Kjaer (rys. 1). Zale¿nooeae czêstotliwooeciowa wspó³czynnika poch³aniania dŸwiêku α dla czystego polipropylenu mo¿e byae modyfikowana przez odpowiedni dobór nape³niacza lignocelulozowego. Nape³niacze uzyskane z rooeliny konopi powoduj¹ znaczny wzrost absorpcji dŸwiêku w zakresie czêstotliwooeci powy¿ej 3000 Hz (rys. 2). Wspó³czynnik poch³aniania dŸwiêku kompozytów z tymi nape³niaczami wzrasta do~25 % i utrzymuje siê na tym poziomie wraz ze wzrostem czêstotliwooeci. Natomiast dodanie nape³niaczy otrzymanych z lnu, s³omy rzepakowej i drewna bukowego do matrycy polipropylenowej przyczynia siê do bardziej rezonansowej charakterystyki poch³aniania dŸwiêku z wyraŸnym maksimum absorpcji (α powy¿ej 20 %) w zakresie czêstotliwooeci od 3000 do 4000 Hz (rys. 3). Wykonane badania potwierdzaj¹ mo¿liwooeae zastosowania kompozytów zawieraj¹cych materia³y lignocelulozowe w budownictwie oraz przemyoele samochodowym z uwagi na korzystn¹ w³aoeciwooeae poch³aniania dŸwiêku. S³owa kluczowe: kompozyty, nape³niacze lignocelulozowe, wspó³czynnik poch³aniania dŸwiêku, absorbery dŸwiêku.

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