Preface, Introduction

Yan

J of Applied Polymer Sci

et al. 2012

Microstructure and damping characteristics were investigated for polycarbonate/multiwalled carbon nanotube (PC/MWCNT) composites. Dynamic mechanical analysis results show that the damping factor and the value of the energy loss fraction w are significantly increased. Especially, nearly 300% improvement in damping factor is observed in the temperature range from 140 to 150 C. Positron annihilation lifetime measurements indicate that both the o-Ps lifetime and the free volume increase with increasing MWCNT content, leading to decrease in the glass transition temperature and increase in the damping properties. The relationships among the damping, mechanical property, and the free volume have been first observed, that is, the increase of the free volume brings about a reduction in tensile strength and an increase in damping. The interfacial friction slipping of MWCNTs and the free volume play an important role in determining the damping property of PC/MWCNT composites.

Section: Resultsmentioning

confidence: 99%

Investigation of free volume and damping property for polycarbonate/multiwalled carbon nanotube composites by positron annihilation technology

Yan

J of Applied Polymer Sci

et al. 2012

J of Applied Polymer Sci

“…Thus, DMTA is an essential tool for appraising the morphology of polymer blends. Sound and vibration damping characteristics of polymers, polymeric blends, composites, or laminates are evaluated with the help of dynamic mechanical analysis 9…”

Section: Resultsmentioning

confidence: 99%

“…The effect of sliding velocity, normal load, surface roughness, and environmental factors on materials has also been studied widely for noise reduction 8. Various techniques have been adopted for arresting the squeaking and rattling noises 4–6, 9–13…”

Section: Introductionmentioning

confidence: 99%

Augmenting the performance of acrylonitrile–butadiene–styrene plastics for low‐noise dynamic applications

Ganguly

Saha

Bhowmick

et al. 2008

ABSTRACT:The main objective of this study was to enhance the performance of acrylonitrile-butadiene-styrene (ABS) plastics for dynamic structural applications, including those of automobile relevance. First, ABS was modified by blending with maleic anhydride grafted styrene-ethylene-butadiene-styrene block copolymer (MA-g-SEBS) in various proportions. Squeaking noise characteristics were evaluated by measurement of the frictional behavior in an in-house fabricated friction testing apparatus, and the results are explained on the basis of the change in surface energy upon modification. Detailed dynamic mechanical analyses (strain, frequency, and temperature sweep) revealed significant improvements in the damping characteristics of the modified ABS, especially that modified with 10 wt % MA-g-SEBS, without much sacrifice in its mechanical strength. The modulus values predicted with Kerner's model of the blends were well correlated with the morphological changes upon modification.

“…The earlier studies tackling this issue are roughly classified into the two approaches. One approach utilizes a large mechanical loss at the glass–rubber transition, and they tune the location of the glass transition temperature ( T g ) or broaden the transition region by blending the polymers with different T g . − A marked change in E ′ inevitably accompanies the glass–rubber transition, which often limits the availability of the materials in industrial use. The other approach introduces the relaxation components into elastomers.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Viscoelasticity of Poly(butyl acrylate) Elastomers Containing Dangling Chains with Controlled Lengths

et al. 2011

We demonstrate that the poly(butyl acrylate) (PBA) elastomers containing considerable amounts of dangling chains with uniform lengths exhibit pronounced viscoelastic relaxation (tan δ > 1) at characteristic frequencies. The elastomers are obtained by the copolymerization of monoacryloyl- and diacryloyl-terminated precursor PBA with narrow size distributions. The molecular weights of the precursors are smaller than the critical molecular weight for the onset of entanglement coupling. The relaxation time of the elastomers (τD) is proportional to the square of the molecular weight of the dangling chains equivalent to the monofunctional PBA (M D), and τD is about 2.5 times larger than the relaxation time of the corresponding free guest chains in the elastomers (τG). These observations are close to the expectations from the Rouse-chain dynamics without entanglement effect (τD ∼ M D 2 and τD = 4τG). These results provide an important basis for the understanding of the dynamics of the unentangled chains whose one end is tethered to the permanent networks. The results also offer a route of molecular control of characteristic frequency and strength of mechanical damping of elastomers.