WO2021255707A1

WO2021255707A1 - A noise reduction article and method of manufacturing same

Info

Publication number: WO2021255707A1
Application number: PCT/IB2021/055406
Authority: WO
Inventors: Alex Varghese; Dhritisunder Bhattacharya; Deval Yogendra Vashistha; Satish Veerappa PALLED
Original assignee: 3M Innovative Properties Company
Priority date: 2020-06-18
Filing date: 2021-06-18
Publication date: 2021-12-23

Abstract

Embodiments of the present invention relates to a noise reduction article (300) and method of manufacturing same. The noise reduction article (300) comprises at least one of polymeric resins and inorganic fillers being deposited on a porous layer (304) and heat treated together to form a unibody, wherein the at least one of polymeric resins and inorganic fillers on the heat treatment forms an impervious layer (302), and the porous layer comprises at least one fiber forming polymer.

Description

A NOISE REDUCTION ARTICLE AND METHOD OF MANUFACTURING SAME

Cross Reference to Related Application

[0001] This Application claims the priority to the Indian Provisional Application No. 202041025681 dated 18 June 2020.

Technical Field

[0002] The present invention relates to a noise reduction article and a method for manufacturing the noise reduction article.

Background

[0003] Noise, vibration, and hardness (NVH) is one of the most in-demand fields in the automobile world. In today’s world, the NVH departments of automobile companies are mainly focusing on performance, weight, and cost. Research and development is actively finding new ways of testing and evaluating noise levels and predicting the noise path for effective noise treatments. The need of noise reduction materials along the noise path becomes very crucial for treatment and extensive assessments have been performed towards optimizing materials for their effective placement to suit performance, weight, and cost.

[0004] For NVH in vehicles, the main parameters under consideration are various sources of noise, or vibration generated through the engine, powertrain systems, exhaust and suspension systems etc. Further, due to emergence of electric vehicles and turbo-charged gasoline powertrain systems, the need for vehicle noise refinement is increasing to improve the vehicle sound signature and overall vehicle comfort levels. A sound pressure level (SPL) comparison of various noise sources from electric vehicle, diesel vehicle and petrol vehicle, is shown in Fig. 1. As can be seen from the data in Fig. 1, there can be three inferences, firstly the noise profile for all the three noise sources has different sound signature profiles, secondly the sound pressure levels follow similar profiles in the frequency zone 100Hz ~ 800Hz, thirdly the sound pressure level varies from 1000Hz ~ 8000Hz. Further the noise profile data, shows that the noise control treatment requirement should be specific to address the noise reduction for these different noise source profiles.

[0005] It is known that noise and vibrations can come from different sources. Some noises are generated by the engine, powertrain systems, exhaust, and suspension systems etc. Some of the products available may not have adequate noise reduction characteristics, high weight and inadequate confirmability leading to gaps between the noise reduction material and a frame of a vehicle through which there can be noise leakage. [0006] During vehicle design processes, the focus is to manage the NVH by minimizing the transfer of undesirable noises and vibration into the passenger cabin area. This can be accomplished by using noise control treatment solutions and NVH materials which improve the comfort, performance, and safety of the vehicle. There is constant analysis performed for various advanced light-weighted noise control treatments to improve overall vehicle level sound pressure levels and vehicle sound quality. Fig. 2 represents a typical vehicle acoustic situation with traditional noise control treatment materials. The parameters under consideration are vehicle sound pressure levels, vehicle sound quality and weight of the noise control treatment material used in the vehicle.

[0007] Therefore, there is a need to provide a lightweight noise reduction article that shows higher noise reduction characteristics. Further, there is also a need to provide such a noise reduction article which can attain complex 3-D shapes. Further, there is also a need to provide such a noise reduction article with superior noise reduction characteristics even after subjected to long term heat aged durability conditions. Further, there is also a need to provide such a lightweight noise reduction article that delivers high noise reduction through a combination of improved sound transmission loss and sound absorption properties.

Summary

[0008] Accordingly, the present invention provides a noise reduction article comprising: a porous layer; and at least one of polymeric resins and inorganic fillers being deposited on the porous layer and heat treated together to form a uni-body, wherein the at least one of polymeric resins and inorganic fillers on the heat treatment forms an impervious layer, and the porous layer comprises at least one fiber forming polymer.

[0009] Another aspect of the present invention relates to a method for manufacturing a noise reduction article, the method comprising: depositing at least one of polymeric resins and inorganic fillers on a porous layer; heat treating the at least one of polymeric resins and inorganic fillers and the porous layer together to form a uni-body, wherein the at least one of polymeric resins and inorganic fillers on the heat treatment forms an impervious layer, and the porous layer comprises at least one fiber forming polymer.

Brief Description of Drawings

[0010] The accompanying drawings, which are incorporated herein and constitute a part of this disclosure, illustrate exemplary embodiments of the present disclosure like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure and thus drawings should be considered illustrative. Also, the embodiments shown in the figures are not to be construed as limiting the disclosure, but the possible variants of present disclosure are illustrated herein to highlight the advantages.

[0011] Fig. 1 shows a SPL comparison of the various noise sources.

[0012] Fig. 2 shows a typical vehicle acoustic situation with traditional noise control treatment materials.

[0013] Fig. 3 shows a cross-sectional view of a noise reduction article, in accordance to an embodiment of the present invention.

[0014] Fig. 4 shows an exemplary application of a noise reduction article.

[0015] Fig. 5 shows the noise reduction article subjected to compression molding in order to obtain a complex 3-D shape.

[0016] Fig. 6 shows the noise reduction article with an additional absorber layer.

[0017] Fig. 7 shows a method of manufacturing of the noise reduction article, in accordance to an embodiment of the present invention.

[0018] Fig. 8 shows the noise reduction article with multiple impervious layers.

[0019] Fig. 9 shows sound transmission loss comparison of the noise reduction article sample versus the non-woven thermal bonded web matrix from 200Hz to 5000Hz using Impedance tube as per ASTM E2611 standard.

[0020] Fig. 10 shows sound absorption coefficient comparison of the noise reduction article from 200 Hz to 5000 Hz for noise source directed towards the impervious membrane and non-woven thermal bonded web matrix facing conditions using Impedance Tube as per ASTM El 050 standard. [0021] Fig. 11 shows sound absorption coefficient comparison of the noise reduction article for noise source directed towards the non-woven thermal bonded web matrix and the noise reduction article with absorber for noise source directed towards the absorber using Impedance Tube as per ASTM E1050 standard.

[0022] Fig. 12 shows sound absorption coefficient comparison of the noise reduction article for noise source directed towards the non-woven thermal bonded web matrix and the noise reduction article with absorber for noise source directed towards the absorber from 200 Hz to 5000 Hz using Reverberation chamber as per ASTM C423 standard.

[0023] Fig. 13 shows sound transmission loss comparison of the noise reduction article at normal condition and the noise reduction article sample after heat-aged condition (120 degree Celsius for 500hrs) from 200Hz Hz to 5000 Hz using Impedance tube as per ASTM E2611 standard.

[0024] Fig. 14 shows sound transmission loss performance of the noise reduction article with absorber sample from 100 Hz to 8000 Hz in Reverberation chamber as per JIS A1441 standard. [0025] Fig. 15 shows mass ratio to sound transmission loss (STL) gain rate of the noise reduction article [0026] Fig. 16 shows SEM & optical microscopy images of different magnifications for the noise reduction article.

[0027] Fig. 17 shows thermal conductivity results of the noise reduction article.

[0028] Fig. 18 shows air flow resistivity test comparison of the impervious membrane sample and the non-woven thermal bonded web matrix.

[0029] Fig. 19 shows loft retention test results under static load condition of the noise reduction article.

[0030] Fig. 20 shows simple description of DMA as applying an oscillating force to a sample and analyzing the material’s response to that force.

[0031] Fig. 21 shows the Tan Delta, storage modulus and loss modulus of the impervious membrane.

[0032] Fig. 22 shows surface roughness results of the impervious membrane.

[0033] Fig. 23 shows tensile strength & elongation results of the impervious membrane.

Detailed Description

[0034] For the purpose of the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Thus, it is to be understood that this invention is not limited to particularly exemplified systems or embodiments that may, of course, vary. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0035] As used herein, the singular form "a" "an" and "the" include plural references unless the context clearly dictates otherwise. The term "and/or" mean one or all of the listed elements or a combination of any two or more of the listed elements.

[0036] The term "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that the other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the invention.

[0037] When the term "about" is used in describing a value or an endpoint of a range, the disclosure should be understood to include the specific value or end point referred to.

[0038] As used herein the terms "comprises", "comprising", "includes", "including", "containing", "characterized by", "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. [0039] The term "incident sound wave" refers to a random sound wave within the audible frequency range emitted from a sound source towards a noise reduction article.

[0040] The term "inorganic fillers" as used herein refers to compounds selected from the group consisting of mica, calcium carbonate, silica bubbles (glass bubbles), cenospheres and combinations thereof. These fdlers behave as particulate reinforcement in the matrix to provide resistance to sound propagation.

[0041] The term "additives" as used herein refers to compounds that lower the surface tension or interfacial tension between two liquids or between a liquid and a solid. These additives may act as surfactants, detergents, wetting agents, emulsifiers, foaming agents, dispersants, and combinations thereof. These additives help in enhanced wetting of fillers with binders.

[0042] The term "binders or binding agents" as used herein refers to any material or substance that holds or draws other materials together to form a cohesive whole mechanically, chemically, by adhesion or cohesion.

[0043] As used herein below, a noise source may be, but not limited to, a combustion engine, an electric vehicle, and an automotive/traction/air-bome transmission system or combination of all in case of a hybrid powertrain system.

[0044] The terms “uni-body noise reduction article” and “noise reduction article” hereinafter may be interchangeably used. Similarly, “impervious layer” and “impervious membrane” hereinafter may be interchangeably used.

[0045] The present invention relates to a noise reduction article which is a uni-body and a method of manufacturing the same.

[0046] As shown in Fig. 3, a noise reduction article 300 comprises an impervious layer 302 formed over a porous layer 304. The porous layer 304 may be a non-woven thermal bonded web matrix layer. The non-woven thermal bonded web matrix layer acts as an acoustic absorber. The non-woven thermal bonded web matrix layer may be made of, but not limited to, at least one fiber forming polymer. The at least one fiber forming polymer may be, but not limited to, Nylon6, Nylon 66, cotton, polyethylene, polyester, polypropylene and polyolefin-based fiber. The porous layer 304 may be made of at least three distinct fibers having different denier in the range about 2D to 20D. The different denier fiber may be adjusted with low melting fibers (10%~30%) thermally bonded to form a uniform web matrix having loft retention and sound absorption properties. The fibers having different deniers help in achieving the loft retention characteristics of the noise reduction article. The porous layer 304 may lie in the range of 15-40 mm thickness or 300-1000 grams per square meter (GSM) value.

[0047] The impervious layer 302 may act as a barrier layer or a reflective layer to the noise. The impervious layer 302 impedes transmission of an incident sound wave by reflecting the sound wave. The impervious layer 302 may be a homogenous, flexible, thermal and acoustic reflective barrier formed using a combination of polymeric resins and inorganic fillers. The impervious layer 302 may be formed by heat treating the at least one of polymeric resins and inorganic fillers placed on the porous layer. The at least one of polymeric resins and inorganic fillers may act as visco-elastic layer (having coating viscosity of 800 to 1400 cps) having lower and higher glass transition temperature (Tg) binders (polymeric resins), suitably adjusted with a range of lightweight in-organic particles and /or slurries (0.01-50 micrometers), thermal stabilizers and processing aids. Due to viscoelastic properties, if the impervious layer 302 is subjected to any tensile stress, this layer stretches and elongates compared to its original state. The impervious layer (for example, the impervious layer 302) may comprise 15-25% by weight, relative to the overall weight of the impervious layer, the low glass transition temperature (Tg) polymer. The impervious layer may also comprise, 10-50% by weight, relative to the overall weight of the impervious layer, a high glass transition temperature (Tg) polymer, and one or more additives and inorganic fillers. Further, the inorganic filler may be 70-75% by weight and the polymeric resins may be 25-30% by weight of the impervious layer, pursuant to heat treatment.

[0048] Further, the thickness of the impervious layer (for example, the impervious layer 302) may be at least 1.0 mm. The impervious layer 302 may be at least 1.5 times higher in basis weight compared to the porous layer. Furthermore, the thickness ratio of the impervious layer is in range of l/20th - 1/lOth of overall thickness of the noise reduction article. The impervious layer may have an air flow resistance exceeding 10000 mks rayls. The impervious layer may have the air flow resistivity at least 1400 times higher than the porous layer. Furthermore, in an embodiment, a rate of reduction in loss factor of the impervious layer obtained at 80°C compared to loss factor obtained at 27°C is about 50%, across a frequency of about 1 Hz to 100 Hz. This is further described in conjunction with Table 14, below.

[0049] The obtained noise reduction article (for example, the noise reduction article 300) is light in weight (about 1800 - 4000 GSM) and has superior acoustic performance having a very high Sound Transmission Loss and Absorption properties in the entire frequency spectrum from 100 Hz - 8000 Hz. This light weighted noise reduction article having a simplified construction functions to maximize the overall sound pressure level reduction and enhance the overall sound quality levels for the application as shown in Fig. 4. The noise reduction article has superior thermal insulation and thermal management properties. The article also maintains the acoustic performance after long term heat aged durability condition at 120°C for 500 hours.

[0050] Furthermore, the noise reduction article is suitable for acoustic applications in high temperature prone areas typically in a firewall application of an automobile. The article is also suitable for applications that need to have acoustic materials near to the noise source typically in a firewall of an automobile. The article is capable of taking complex shapes and design achieved through compression molding suitable for various applications such as in automobile dash application and meets a flammability standard Federal Motor Vehicles Standard Safety (FMVSS302). Further, the article is also suitable in deriving complex 3D Shapes- suitable for certain automotive noise reduction treatment applications as shown in Fig. 5 according to an embodiment. The noise reduction article can be subjected to compression molding to obtain the desired complex shape that is needed for a particular application using compression plates (500 and 502) as represented in Fig. 5. It is desirable to attain a shape that can conform to a profile or shape of a surface separating the vehicle cabin from engine compartment. Other moldable applications include e-motor wraps and engine encapsulations.

[0051] Further, the corresponding gain in the STL using impedance tube as per ASTM E2611 standard of the noise reduction article compared to non-woven thermal bonded web matrix (without impervious membrane) is about 10 times, 9 times, 8 times, 6 times, 4 times and 2 times at 200Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz and 5000 Hz respectively. The noise reduction article also controls overall noise reduction generated from a noise source such that the sound absorption coefficient using impedance tube as per ASTM El 050 standard for noise source directed towards non-woven thermal bonded web matrix (porous layer) facing condition has 23% absorption at 200 Hz; 28% absorption at 500 Hz; 43% absorption at 1000 Hz; 81% absorption at 2000 Hz; 81% absorption at 4000 Hz and 76% absorption at 5000 Hz.

[0052] The noise reduction article has comparatively low performance in the sound absorption coefficient using impedance tube as per ASTM El 050 standard for noise source directed towards impervious layer facing condition. This exhibits the noise blocking attribute of the impervious layer and thus not allowing much sound waves to pass through its surface (200 Hz: 19% absorption; 500 Hz: 18% absorption; 1000 Hz: 7% absorption; 2000 Hz: 14% absorption; 4000 Hz: 2% absorption; 5000 Hz: 9% absorption). [0053] The impervious layer along with the underlying non-woven thermal bonded web matrix fiber material (porous layer) have both sound transmission loss (STL) and sound absorption coefficient (SAC) properties across the desired frequency spectrum.

[0054] Further, when the noise reduction article is applied with a static load of 6 kN/m², leading to around 56% thickness compression to its original thickness (32 mm) for 7 continuous days, the rebound of thickness (loft gain) immediately after removal of load was about 86% for the article.

[0055] In an embodiment, the noise reduction article is placed in a vehicle cabin or engine compartment. The article matrix is placed in such a way that the porous layer touches the firewall/sheet metal and the impervious layer faces the cabin of the vehicle. Similarly, the noise reduction article can be placed in the engine/motor compartment such that the porous layer touches the firewall/sheet metal and the impervious layer faces the engine/motor. Similarly, the combination can also be placed on the base of the driver and pillion compartment such that the porous layer touches the sheet metal/base of the vehicle front and rear floor and the impervious layer faces the cabin of the vehicle. The noise reduction article can be used in many applications including, automotive, aerospace, marine, locomotives, building acoustics including concrete slab insulation, appliances, and other potential product application requiring acoustic properties.

[0056] As shown in Figure 6, an absorber layer 602 may be attached to the porous layer 304 of a noise reduction article 600 to get enhanced sound absorption properties according to an embodiment. The noise reduction article 600 refers to combination of the impervious layer 302 and the porous layer 304 acting as a barrier and an absorber layer. The absorber layer 602 may be, but not limited to, bonded or thermally bonded on the porous layer. The absorber layer 602 may lie in the range of 200-500 GSM. The material of the absorber layer may be, but not limited to, melt-blown nonwoven fibrous web and any other polyolefin based fibrous web matrix. In an embodiment, this additional absorber layer may be a nonwoven fibrous web [Polypropylene + Polyethylene terephthalate (PET)] made from for example, a melt blown process. This whole combination (noise reduction article 600 having the absorber) delivers desired thermal and noise reduction properties. The noise reduction article 600 with absorber may lie in the range of 2000 - 4500 GSM.

[0057] This noise reduction article with an additional absorber layer controls overall noise reduction generated from a noise source such that the sound absorption coefficient using impedance tube as per ASTM El 050 standard for the noise source directed towards the absorber delivers excellent sound absorption coefficient across the entire frequency spectrum having 29% absorption at 200 Hz; 67% absorption at 500 Hz; 100% absorption at 1000 Hz; 88% absorption at 2000 Hz; 91% absorption at 4000 Hz; and 87% absorption at 5000 Hz. The addition of the absorber to the noise reduction article enhances the absorption performance in the entire frequency spectrum (200 Hz ~ 5000 Hz) which will benefit in improving the sound quality metrics in vehicular level conditions.

[0058] The noise reduction article with absorber (e.g. the noise reduction article 600) controls overall noise reduction generated from a noise source such that the sound absorption coefficient using Reverberation Chamber as per ASTM C423 standard for noise source directed towards the absorber delivers excellent sound absorption coefficient across the entire frequency spectrum having 45% absorption at 200 Hz; 100% absorption at 500 Hz; 100% absorption at 1000 Hz; 87% absorption at 2000 Hz; 87% absorption at 4000 Hz and 85% absorption at 5000 Hz.

[0059] Further, the maximum growth trend of STL for the various GSM sample of the noise reduction article with absorber is in the frequency zone of 250 Hz -500 Hz ranging 18.9 dB-20.2 dB as the STL gain per octave. This is further described in conjunction with Table 8.

[0060] Further, the maximum STL gain for Mass Ratio of 1.5 of the noise reduction article with absorber is seen across the frequency zone of 250 Hz-800 Hz ranging with 5.5 dB -6.1 dB. This is further described in conjunction with Table 9.

[0061] In another embodiment, the absorber layer (placed inside the driver’s compartment) touches the sheet metal/firewall, and the impervious layer faces the cabin of the vehicle. Similarly, the absorber (placed inside the engine/motor compartment) touches the sheet metal/firewall whereas the impervious layer faces the engine/motor. Furthermore, the absorber layer touches the sheet metal/base of the vehicle and the impervious layer faces the cabin of the vehicle.

Method of Manufacture

[0062] The present invention also relates to a method of manufacturing the noise reduction article as shown in Fig. 7. The method initiates with feeding a roll of the porous layer and unwinding the porous layer as may be provided in a roll form at step 702. Subsequently, the at least one of polymeric resins and inorganic fillers may be placed on the porous layer at step 704. For instance, a homogeneous mixture of the at least one of polymeric resins and inorganic fillers used. In an embodiment, a spray coating method may be used to place the layer of the at least one of polymeric resins and inorganic fillers on the porous layer. This method provides a uniform layer of the impervious layer over the porous layer. The at least one of polymeric resins and inorganic fillers may be deposited by spray coating, screen coating, gravure coating, die coating, brush coating, dip coating and other methods of depositing these materials. Any process known to a person skilled in the art may also be used to place at least one of polymeric resins and inorganic fdlers on the porous layer. Subsequently, the at least one of polymeric resins and inorganic fdlers and the porous layer are heat treated together at step 706. The heat treatment may be done in a hot air oven using convection or radiation heating methodology. During the heat treatment process, cross-linking of polymer occurs to form the impervious layer, and fuses to the porous layer, and water evaporates. Subsequently, post heat treatment, the uni-body noise reduction article is obtained and collected at step 708.

[0063] The noise reduction article can include multiple layers of impervious layer and porous layer. Fig. 8 shows a noise reduction article 800 having impervious layers on both sides of a porous layer 802. A first impervious layer 804 is positioned or formed on the porous layer 802 on one side and a second impervious layer 806 on the other side of porous layer. The first and second impervious layers (804 and 806) may be deposited on the porous layer (802) using the methods described earlier and in conjunction with Fig. 7. The first impervious layer (804) may have different properties and size (e.g. thickness), or configuration as compared to the second impervious layer 806. In an embodiment, the thickness of the first and second impervious layers (804 and 806) may be at least 1.0 mm. The impervious layers may be at least 1.5 times higher in basis weight compared to the porous layer. Additionally, and /or alternatively, the first and / or second impervious layers (804 and 806) may have different thickness and different basis weight compared to the porous layer. Depending on the various type of noise treatment requirement that may arise from aerospace, cryogenics, locomotives or commercial vehicle, such constructions may be applicable to address thin caliper packaging of noise control treatments demanding extreme noise control needs.

[0064] In an alternate embodiment, there may be one or more impervious layers positioned in a stacked manner on the porous layer. Each of these impervious layers may have different properties and size or configuration. The properties, size and configuration of the impervious and porous layers can be varied to obtain the noise reduction article having desired acoustic properties and performance parameters for various applications. The multiple layers can be formed sequentially by laying one of the impervious layers on another layer through any known manufacturing processes.

[0065] Further, in another embodiment, an absorber layer may be positioned on or adjacent to the second impervious layer (e.g. the second impervious layer 806) of the noise reduction article 800 shown in Fig. 8. The absorber layer may be bonded or thermally bonded on to the second impervious layer.

[0066] To establish the NVH performance improvements and thermal properties of the noise reduction article, the following tests were carried out: [0067] Sound transmission loss (STL) - Noise measurements using Impedance Tube as per ASTM E2611 Standard (Normal Incidence) [0068] Fig. 9 shows the Sound transmission loss comparison of the noise reduction article sample

(Sample B) versus the non-woven thermal bonded web matrix without impervious membrane (Sample A) from 200 Hz to 5000 Hz. Sample B used here was around 3000 GSM with 32 mm thickness and Sample A used was around 1000 GSM with 30 mm thickness. Key observations:

Sample B exhibits high Sound transmission loss (STL) compared with Sample A across entire frequency spectrum. The STL results is represented in Table 1.

Table 1 : Sound Transmission Loss Data

The corresponding gain in the STL of the noise reduction article compared to non-woven thermal bonded web matrix (without impervious membrane) is about 10 times, 9 times, 8 times, 6 times, 4 times and 2 times at 200 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz and 5000 Hz respectively.

[0069] Sound absorption coefficient (SAC) — Noise measurements using Impedance Tube as per ASTM El 050 Standard (Normal Incidence)

[0070] Fig. 10 shows the Sound absorption coefficient comparison of the noise reduction article from 200 Hz to 5000 Hz for noise source directed towards the impervious layer (Sample B) and non- woven thermal bonded web matrix (Sample A) facing conditions. The noise reduction article used here was around 3000 GSM with 32 mm thickness. Key Observations: a) The noise reduction article has excellent overall (200 Hz ~ 5000 Hz) sound absorption coefficient for noise source directed towards non-woven thermal bonded web matrix facing condition. (200 Hz: 23% absorption; 500 Hz: 28% absorption; 1000 Hz: 43% absorption; 2000 Hz: 81% absorption; 4000 Hz: 81% absorption; 5000 Hz: 76% absorption) b) The noise reduction article has comparatively low performance for noise source directed towards impervious membrane facing condition. This exhibits the noise blocking attribute of the impervious membrane and thus not allowing much sound waves to pass through its surface. (200 Hz: 19% absorption; 500 Hz: 18% absorption; 1000 Hz: 7% absorption; 2000 Hz: 14% absorption; 4000 Hz: 2% absorption; 5000 Hz: 9% absorption)

The SAC result is represented in Table 2. The porous layer faced the noise source in Sample A and the impervious layer faced the noise source in Sample B.

Table 2: Sound Absorption Coefficient data

[0071] Sound absorption coefficient (SAC) — Noise measurements using Impedance Tube as per ASTM El 050 Standard (Normal Incidence)

[0072] Fig. 11 shows the Sound absorption coefficient (SAC) comparison of the noise reduction article (Sample A) for noise source directed towards the non-woven thermal bonded web matrix and the noise reduction article with absorber (Sample B) for noise source directed towards the absorber from 200 Hz to 5000 Hz.

The noise reduction article (Sample A) used here was around 3000 GSM with 32 mm thickness and the noise reduction article with absorber (Sample B) used here was around 3340 GSM with 69 mm thickness.

Key Observations: a. The noise reduction article with absorber for noise source directed towards the absorber delivers excellent sound absorption coefficient across the entire frequency spectrum. (200 Hz: 29% absorption; 500 Hz: 67% absorption; 1000 Hz: 100% absorption; 2000 Hz : 88% absorption; 4000 Hz: 91% absorption; 5000 Hz: 87% absorption) b. The addition of absorber to the noise reduction article has advanced the absorption performance in the entire frequency spectrum (200 Hz ~ 5000 Hz) which will benefit in improving the sound quality metrics in vehicular level conditions. The SAC result is represented in Table 3. The porous layer faced the noise source in Sample A and the absorber layer faced the noise source in Sample B. Table 3 : Sound Absorption Coefficient data

[0073] Sound absorption coefficient (SAC) — Noise measurements using Reverberation Chamber as per ASTM C423 Standard (Random Incidence)

[0074] Fig. 12 shows the Sound absorption coefficient (SAC) comparison of the noise reduction article (Sample A) for noise source directed towards the non-woven thermal bonded web matrix and the noise reduction article with absorber (Sample B) for noise source directed towards the absorber from 200 Hz to 5000 Hz.

[0075] Sample A used here was around 3000 GSM with 32 mm thickness and Sample B used here was around 3340 GSM with 69 mm thickness.

Key Observations: a) The noise reduction article with absorber for noise source directed towards the absorber delivers excellent sound absorption coefficient across the entire frequency spectrum. (200Hz: 45% absorption; 500 Hz: 100% absorption; 1000 Hz: 100% absorption; 2000Hz: 87% absorption; 4000Hz: 87% absorption; 5000 Hz: 85% absorption) b) The noise reduction article for noise source directed towards the non-woven thermal bonded web matrix has the following performance. (200Hz: 36% absorption; 500 Hz: 74% absorption; 1000 Hz: 89% absorption; 2000Hz: 87% absorption; 4000Hz: 73% absorption; 5000 Hz: 68% absorption) c) The addition of absorber to the noise reduction article has advanced the absorption performance in the entire frequency spectrum (200 Hz - 5000 Hz) which will benefit in improving the sound quality metrics in vehicular level conditions. The SAC result is represented in Table 4. The porous layer faced the noise source in Sample A and the absorber layer faced the noise source in Sample B.

Table 4: Sound Absorption Coefficient data

[0076] Sound transmission loss (STL) — Noise measurements using Impedance Tube as per A STM E2611 Standard (Normal Incidence)

[0077] Fig. 13 shows the Sound transmission loss (STL) comparison of the noise reduction article (Sample B) at normal condition and the noise reduction article sample (Sample A) after heat-aged condition (120 degree Celsius for 500hrs) from 200 Hz to 5000 Hz. The noise reduction article used here was around 3000 GSM with 32 mm thickness.

Key Observations: a) The noise reduction article exhibits high performance in Sound transmission loss (STL). b) There is not much deterioration of Sound transmission loss (STL) performance of the noise reduction article after heat aging for 120 degree Celsius for 500 hrs. c) The overall Average STL is represented in below Table 5. The noise reduction sample was heat aged at 120°C for 500 hours in Sample A and not heat aged in Sample B. Table 5 : Sound Transmission Loss Data

[0078] Sound transmission loss (STL) — Noise measurements using Reverberation Chamber as per JIS A 1441 Standard (Random Incidence)

[0079] Fig. 14 shows the Sound transmission loss (STL) performance of the noise reduction article with absorber sample from 100 Hz to 8000 Hz.

[0080] The noise reduction article with absorber used here was around 3340 GSM with 68 mm thickness.

Key Observations: a) The noise reduction article with absorber exhibits superior performance in Sound transmission loss across entire frequency spectrum. (500 Hz: 42.6 dB; 1000 Hz: 57.6 dB; 2000 Hz: 71.1 dB; 8000 Hz: 94 dB) b) The sound transmission loss performance for the various GSM of noise reduction article with absorber sample was tested in Reverberation chamber as per JIS A1441 standard as shown in the Table 6. The various GSM samples of the noise reduction article with absorber was achieved by increasing the GSM of the Impervious membrane only and keeping the GSM constant for the non- woven thermal bonded web matrix and absorber.

Table 6: Sound Transmission Loss (Reverberation Chamber data)

Region- 1 is the low frequency range, Region - II is the mid frequency range and Region -III is the high frequency range.

[0081] The data from the Table 6 shows that there is increase in the STL across the Low/Mid and High frequency zones with the increase in the GSM of the noise reduction article with absorber which is mainly contributed by the increase in the GSM of impervious membrane.

[0082] Further, the average sound transmission loss ratio at low, mid and high frequency zones across various mass ratio is shown in Table 7.

Table 7: Sound Transmission Loss Ratio at frequency zones across various mass ratio (Reverberation chamber data)

[0083] The data from the Table 7 shows that the average STL ratio is consistent at low, mid and high frequency zones for various mass ratio of the noise reduction article with absorber.

[0084] Further, the sound transmission loss gain per octave performance for the various GSM of noise reduction article with absorber sample is shown in Table 8.

Table 8: Sound Transmission Loss gain per Octave for various GSM (Reverberation chamber data)

[0085] The data from the Table 8 shows that the maximum growth trend of STL for the various GSM sample of the noise reduction article with absorber is in the frequency zone of 250 Hz to 500 Hz ranging with 18.9 dB to 20.2 dB as the STL gain per octave. Per octave gain remains uniform across the observed GSMs.

[0086] Further, the sound transmission loss gain for Mass Ratio of 1.5 for the noise reduction article with absorber sample is shown in Table 9.

Table 9: Sound Transmission Loss gain for Mass ratio of 1.5 (Reverberation chamber data)

[0087] The data from the Table 9, shows that the maximum STL gain for Mass Ratio of 1.5 of the noise reduction article with absorber is seen across the frequency zone of 250 Hz to 800 Hz ranging with 5.5 dB to 6.1 dB. As per the mass law criteria for a double mass 6 dB gain in STL is achieved, however from the above data this shows that the maximum STL gain for Mass Ratio of 1.5 of the noise reduction article with absorber is seen across the frequency zone of 250 Hz to 800 Hz ranging with 5.5 dB to 6.1 dB. [0088] Further the mass ratio to STL gain rate as shown in Fig. 15 can be understood from several experiments that in the given noise reduction article the relative gain of mass with respect to the corresponding gain in STL follows a 2-degree polynomial function and the slope of this function at any point differs by 9 times when three different masses are relatively compared in pairs. For example if ml, m2 & m3 are three different masses and si= f(mi), S2=f(ni2), S3= f(ms) then, S2.si v/s S3.S2 in relation with m2:mi & ms.mi will exhibit a ratio of 9: 1 in their corresponding slopes at

Qs any given point , where in the slopes are expressed as the differential —

. Where in s represents the STL function and m represents the masses. [0089] Morphology analysis of the homogenous impervious membrane and the non-woven thermal bonded web matrix.

[0090] The homogenous impervious membrane and the non-woven thermal bonded web matrix was subjected to Scanning Electron Microscopy (SEM) analysis and Optical microscopy analysis and evaluated for surface appearance.

[0091] Fig. 16 shows the SEM and Optical Microscopy images of different magnifications, images, a uniform homogenous impervious membrane deposition is clearly visible on top of the non-woven thermal bonded web matrix resulting in a noise reduction article composition. Also seen is the top layer non-woven thermal bonded web matrix fibers have merged well with the impervious membrane to form a fiber reinforced structure adding to additional impedance to sound waves.

[0092] Flammability Resistance as per FMVSS302 Standard Test Procedure:

The test is conducted inside a test chamber where the test specimen is mounted horizontally. The exposed side of the test specimen is subjected to a gas flame from underneath. The burnt distance and the time taken to bum this distance is measured during the test. The result, the burning rate, is expressed in mm/min. The noise reduction article was found passing the Horizontal Flammability standard as per FMVSS 302 and is represented in Table 10. The noise reduction article used here was around 3000 GSM with 13 mm thickness. The impervious membrane of the noise reduction article faced upward on test frame during the flame test in Sample A and downward in Sample B.

Table 10: Flammability Test Results

[0093] Thermal Conductivity as per ASTM C518 Standard (Average Temp: 225 degree Celsius^') [0094] Fig. 17 shows the thermal Conductivity Results of the noise reduction article tested at 22.5°C. The noise reduction article sample shows a thermal conductivity of 0.038 W/mK. The noise reduction article used here was around 3000 GSM with 32 mm thickness.

[0095] Further the thermal conductivity value remains independent of any change in the coating thickness of noise reduction article.

[0096] Hot Odor as per SAE J1351 Test Procedure:

Test specimens were representative of the material or composite being evaluated. Test specimens had a surface area (including all surfaces) of 250 cm² ± 25 cm² (0.28 ft² ± 0.028 ft²). Test specimens were cut to any dimension compatible to the dimensions of the jar, provided the specimen surface area is maintained at 250 cm².

Prior to the test, the specimens were conditioned for 24 hours at 23°C ± 2°C (70 °F ± 2 °F) and 50% RH ± 5% RH.

Samples were tested dry and in the presence of moisture. For the dry test, a test specimen was placed in a jar and covered with the lid and ring. For the wet test, 2 cc of distilled water was put directly on the specimen after the specimen has been placed in the j ar and cover with the lid and ring . One empty jar was included for control use purposes closed with a lid and ring.

Jars were placed in an oven preheated to 65°C ± 3°C (149°F ± 5°F) for 1 hour (±5 minutes). This temperature was selected to be representative of automotive applications.

The jars were removed after one hour of oven heating time. A first panelist positioned his head near the control jar (approximately 15 cm away) and removed the lid. Then, with a cupped hand, the first panelist drew the air from the jar to their nose and slowly inhaled. The first panelist immediately repeated the procedure for the first test specimen (dry) and recorded the appropriate rating (as odor scale listed in below). Lids were removed from the jars longer for not longer than 5 seconds. Tests were conducted in an environment free from drafts and contaminant odors. Results of the testing are represented in Table 11. A 3000 GSM noise reduction article was tested (Sample A)

ODOR SCALE -Rating Description

1 No noticeable odor

2 Slight, but noticeable odor

3 Definite odor, but not strong enough to be offensive 4 Strong offensive odor

5 Very strong offensive odor

Table 11 Hot Odor Test Results

The noise reduction article does not exhibit any objectionable odor.

[0097] Air Flow Resistivity as per ASTM C-522

[0098] Fig. 18 shows the Air flow resistivity test comparison of the impervious membrane sample and the non-woven thermal bonded web matrix. The Impervious membrane used here was around 2000 GSM with 1.7 mm thickness (Sample A) and the non-woven thermal bonded web matrix

(Sample B) used was around 1000 GSM with 30 mm thickness.

Key observations: a) The Impervious membrane exhibits high air flow resistivity. The Air Flow resistance value exceeds 10,000 mks rayls which exhibits that the material is non- porous and highly impervious. b) The overall gain in the air flow resistivity of the impervious membrane compared to the non-woven thermal bonded web matrix is around > 1400 times. c) The overall AFR data is represented in Table 12. Table 12: Air Flow Resistivity mks rayl/m

[0099] Loft Retention Test under static load condition [0100] Fig. 19 shows the loft retention test under static load condition results of the noise reduction article. The noise reduction article used here was around 3000 GSM with 32 mm thickness. The static load considered here was 6 kg for a sample size of 10 cm x 10 cm. The initial thickness was measured for the noise reduction article which was about 32 mm. The static load of 6 kg was applied to the sample size of 10 cm x 10 cm and was kept under load condition for 7 days. The thickness under load was measured and was about 14 mm which was about 56% compression of the original thickness. After seven days the load was removed, and the thickness regained immediately and was about 26 mm. Further the sample was kept at normal condition without any load for 2 days and the thickness regained to 29 mm. Key Observations: a) The noise reduction article exhibits excellent loft retention properties after static load conditions. b) The loft retention property of the noise reduction article will help to maintain the sound absorption properties post molding conditions. c) The Loft retention performance details is shown in Table 13

[0101] Dynamic Mechanical Analysis (DMA) of the Impervious membrane

[0102] Dynamic Mechanical Analysis of the Impervious membrane was conducted to evaluate the Storage modulus, loss modulus and the derived tan delta values at frequency ranging from 0.1 to 100 Hz at 2 different temperature viz, RT and 80 degree Celsius. DMA can be simply described as applying an oscillating force to a sample and analyzing the material’s response to that force as shown in Fig. 20. From this, one calculates properties like the tendency to flow (called viscosity) from the phase lag and the stiffness (modulus) from the sample recovery. These properties are often described as the ability to lose energy as heat (damping) and the ability to recover from deformation (elasticity). One way to describe what we are studying is the relaxation of the polymer chains. Another way would be to discuss the changes in the free volume of the polymer that occur. Both descriptions allow one to visualize and describe the changes in the sample. In general DMA is an instrument that mechanically deforms a sample and measures the sample response. The response to the deformation can be monitored as a function of temperature or time. [0103] DMA measures the mechanical properties of a sample as it is deformed over a range of stress, strain, time and temperature. It can either apply Stress (Force) and measure Strain (Displacement), or apply Strain and measure Stress and Determines the Modulus of the material (Stress/ Strain) and can controls the Frequency (Time) of the deformation to measure viscoelastic properties (Storage Modulus, Loss Modulus, Tan Delta) at temperature controlled in heating, cooling, or isothermal modes. The modes of Deformation are Tension, Bending, Compression and Shear.

[0104] The Impervious membrane used here was around 2000gsm with 1.7mm thickness. The Tan Delta, Storage modulus and Loss modulus is shown in Fig. 21. Key Observations: a) The Impervious membrane exhibits > 0.4 Tan Delta values uniformly maintaining across 1 Hz to 100 Hz at RT (indicates Room Temperature - 27°C) b) Whereas the Impervious membrane exhibits > 0.2 Tan Delta values uniformly maintaining across 1 Hz to 100 Hz at 80deg C. c) The DMA performance details is shown in Table 14. As shown in Table 14, a rate of reduction in loss factor of the impervious layer obtained at 80°C compared to loss factor obtained at 27°C is about 50%, across a frequency of about 1 Hz to 100 Hz.

Table 14: DMA performance results

[0105] Surface roughness analysis of the Impervious membrane [0106] Fig. 22 shows the Surface roughness results of the impervious membrane. Surface roughness often shortened to roughness, is a component of surface texture. It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. The Impervious membrane used here was around 2000 GSM with 1.7 mm thickness (Sample A). The results of the Surface roughness of the impervious membrane indicates that it has rough surface with Ra/Rz aspect ratio of 1:4 based on the observed value of Ra as 14.02 pm and Rz value as 53.07 pm. The results of the Surface roughness of the Impervious membrane is shown in Table 15. Further for various coating thickness of the impervious membrane has consistent Ra/Rz aspect ratio range of 1:4 - 1:5.

Table 15: Surface Roughness results of the Impervious membrane

[0107] Tensile Strength & elongation of the Impervious membrane

[0108] Fig. 23 shows the tensile strength & elongation results of the impervious membrane. The impervious membrane used here was around 2000 GSM with 1.7 mm thickness (Sample A). The force at tensile strength is 7.2 Kgf with displacement of 33mm. The result of the tensile strength and elongation of the impervious membrane is shown in Table 16.

Table 16: Tensile strength and elongation of impervious membrane

[0109] Although, the present invention has been described in considerable detail with reference to certain preferred embodiments and examples thereof, other embodiments and equivalents are possible. Even though numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with functional and procedural details, the disclosure is illustrative only, and changes may be made in detail, within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms. Thus, various modifications are possible of the presently disclosed system and process without deviating from the intended scope and spirit of the present disclosure. Accordingly, in one embodiment, such modifications of the presently explained disclosure are included in the scope of the present disclosure.

Claims

What is claimed is:

1. A noise reduction article, the article comprising: a porous layer; and at least one of polymeric resins and inorganic fdlers being deposited on the porous layer and heat treated together to form an uni-body, wherein the at least one of polymeric resins and inorganic fdlers on heat treatment forms an impervious layer, and the porous layer comprises at least one fiber forming polymer.

2. The article as claimed in claim 1, wherein the impervious layer and the porous layer acts as an acoustic barrier and an acoustic absorber respectively whereby the noise reduction article controls the noise reduction through sound transmission loss and sound absorption properties.

3. The article as claimed in claim 1 , wherein basis weight of the noise reduction article is about 1800 to about 4000 GSM.

4. The article as claimed in claim 1, wherein the at least one of polymeric resins and inorganic fillers act as a viscoelastic layer.

5. The article as claimed in claim 4, wherein the inorganic filler is 70-75% and polymeric resin is 25-30% by weight of the impervious layer, pursuant to heat treatment.

6. The article as claimed in claim 4, wherein thickness of the impervious layer is at least 1.0 mm.

7. The article as claimed in claim 5, wherein a rate of reduction in loss factor of the impervious layer obtained at 80°C compared to loss factor obtained at 27°C is about 50%, across a frequency of about 1 Hz to 100 Hz.

8. The article as claimed in claim 1, wherein the impervious layer comprises 15-25% by weight, relative to the overall weight of the impervious layer, of a low glass transition temperature (Tg) polymer.

9. The article as claimed in claim 1, wherein the impervious layer comprises 10-50% by weight, relative to the overall weight of the impervious layer, of a high glass transition temperature (Tg) polymer, and one or more additives and in-organic fdlers.

10. The article as claimed in claim 1, wherein the at least one of polymeric resins and inorganic fdlers has a viscosity in range of 800- 1400 cps.

11. The article as claimed in claim 1, wherein the inorganic fdlers are in the range of 0.01-50 micrometers.

12. The article as claimed in claim 1, wherein the impervious layer is at least 1.5 times higher in basis weight compared to the porous layer.

13. The article as claimed in claim 1, wherein the thickness ratio of the impervious layer is in range of l/20th - 1/lOth of overall thickness of the noise reduction article.

14. The article as claimed in claim 1, wherein the porous layer, is a non-woven thermal bonded web matrix layer, having a thickness of at least 15 mm.

15. The article as claimed in claim 1, wherein the at least one fiber forming polymer is at least one of Nylon6, Nylon 66, cotton, polyethylene, polyester, polypropylene, polyolefin-based fibers.

16. The article as claimed in claim 1, wherein the porous layer comprises at least three distinct fibers having different denier in the range about 2D to 20D.

17. The article as claimed in claim 1, wherein the impervious layer has an air flow resistance exceeding 10000 mks rayls.

18. The article as claimed in claim 1, wherein the impervious layer has the air flow resistivity at least 1400 times higher than the porous layer.

19. The article as claimed in claim 1, further comprising an absorber layer being attached to the porous layer, wherein the absorber layer is a non-woven fibrous material.

20. The article as claimed in claim 19, wherein the absorber layer lies in the range of 200-500 GSM.

21. The article as claimed in claim 19, wherein the sound transmission loss gain per octave of the noise reduction article is in the range of at least 18.9 dB to 20.2 dB for the frequency range of 250 Hz to 500 Hz, wherein basis weight of the noise reduction article is in the range of about 2840 GSM to 4340 GSM.

22. A method for manufacturing a noise reduction article, the method comprising: depositing at least one of polymeric resins and inorganic fillers on a porous layer; and heat treating the at least one of polymeric resins and inorganic fillers and the porous layer together to form an uni-body, wherein the at least one of polymeric resins and inorganic fillers on the heat treatment forms an impervious layer, and the porous layer comprises at least one fiber forming polymer.

23. The method as claimed in claim 22, wherein basis weight of the noise reduction article is about 1800 to about 4000 GSM.

24. The method as claimed in claim22, wherein the at least one of polymeric resins and inorganic fillers acts as a viscoelastic layer.

25. The method as claimed in claim 22, wherein the at least one fiber forming polymer is at least one of Nylon6, Nylon 66, cotton, polyethylene, polyester, polypropylene, polyolefin-based fibers.

26. The method as claimed in claim 22, further comprising attaching an absorber layer to the porous layer, wherein the absorber layer is a non-woven fibrous material.

27. The method as claimed in claim 26, wherein the absorber layer lies in the range of 200-500 GSM.