GB1569316A

GB1569316A - Vibration damped articles comprising partially chlorinated polymeric materials

Info

Publication number: GB1569316A
Application number: GB52953/76A
Authority: GB
Original assignee: Forces Armees Francaises
Current assignee: Forces Armees Francaises
Priority date: 1975-12-23
Filing date: 1976-12-17
Publication date: 1980-06-11
Also published as: FR2336418B1; FR2336418A1

Description

(54) VIBRATION DAMPED ARTICLES COMPRISING PARTIALLY CHLORINATED POLYMERIC MATERIALS (71) We, ETAT FRANCAIS represented by the ministerial Delegate for Armaments, of 14, Rue Saint-Dominique, 75997 Paris Armees, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularl) described in and 4y the following statement:- This invention relates to vibration-damped articles.

The technical sphere with which the invention is concerned is inter alia, the damping of vibrations from a sound source situated in a fluid. In such a sphere, in addition to the technique of insulation in which the vibration-generating source is isolated by an elastic element, and the technique of absorption in which reactive masses are associated with elastic and dissipative elements, it is known to fix the vibration source on a structure having a damping effect. In this last case, some of the vibratory energy is converted into heat by that structure. A structure such as this is known as a composite structure and may assume one of three forms, namely a simple coating, a sandwich structure and an insert structure.

A simple coating may be obtained by depositing a layer of anti-vibratory material (a vibration damping element) onto a layer of metal, and functions by traction and compression; a sandwich structure may be obtained by depositing a layer of metal onto the above mentioned simple coating structure so that the material functions by shearing; and an insert structure may be obtained by placing the anti-vibratory material in cavities of any shape in the structure.

Generally speaking, an anti-vibratory material is required to have three properties. First, the anti-vibratory material should have a high damping coefficient over the widest possible temperature and frequency ranges. (Damping coefficient is defined as being the tangent of the phase displacement angle (a) between the stress and the deformation when the material is subjected to a sinusoidal stress).

Second, the material should have a high adaptability of Young's modulus. Thus, in the case of a sandwich structure, optimum performance is obtained with high modulus values. Third, the anti-vibratory material should show high stability under static loads.

Various synthetic organic polymers are known to be suitable for use as antivibratory materials. Polymers such as these include plasticised polyvinyl chloride and polyvinyl acetate.

Unfortunately, these polymers are attended by a certain number of disadvantages which make them unsuitable for wide-spread use in industry. They generally show a low Young's modulus and significant flow at the operating temperature; in addition, the temperature range in which they are effective is narrow. In order to avoid flow, the use of other polymers has been proposed.

French Patent No. 2,255,313 for example describes the use of polyisoprenes having a large number of vinyl units. Unfortunately, these polyisoprenes can only be used in the temperature range from -300C to +300C and have to be vulcanised in order to improve their stability under load.

Thus there is a need to provide vibration-damped articles incorporating a vibration-damping material which may be used in a temperature range from -5"C to +130 C, and which has a high Young's modulus, for example greater than 107 N/M2 at 20"C.

These requirements are surprisingly achieved by employing as vibration damping element an anti-vibratory material formed primarily by the chlorination product of a polymer containing more than 50% of 1,2-polybutadiene structures.

Accordingly the present invention provides a vibration-damped article which comprises a substrate contacted with a vibration damping element comprising a polymeric material, at least 50 -Ó of the structural units of which are based on 1,2polybutadiene which is at least partially chlorinated.

In the context of the invention, a polymeric material with a I ,2-polybutadiene structure is a polymer with the following 1,2-structure:

Preferably from 75 to 100% of the structural units of the polymeric material are based on 1,2-polybutadiene.

The polymer may be chlorinated by any known method. In particular, the polymer may be dissolved in methylene chloride and the reaction carried out by introducing chlorine in a stoichiometric quantity. Preferably, the polymeric material has a chlorine content of from 6 to 56% by weight, based on the chlorinated polymer.

The chlorinated polymeric materials employed as vibration damping elements of articles according to the invention have high damping coefficients over a range of standard frequencies extending from 10Hz to 1MHz. They may be used either on their own or in admixture with mineral or organic fillers such as carbon black or vermiculite, or in the form of copolymers. In addition they may readily be converted into sheet-form elastomers. The polymeric materials, which may optionally be used in vulcanised form, show increased fire resistance by virtue of the presence in them of chlorine.

In accordance with the invention the vibration-damped article may simply be the substrate coated with the polymeric material. Alternatively the article may comprise two layers of the substrate, which may be, for example, metallic, with the polymeric material disposed between'the substrates as vibration damping element.

In yet another form the polymeric material may be disposed in cavities provided in the substrate of the article.

In the articles according to the invention it is preferred to ue as vibration damping element a polymeric material which has a damping coefficient (as hereinbefore defined) of at least 0.5 over the frequency range of 10 Hz to 1 MHz.

The material is preferably stable over the temperature range-50C to +1300C, and preferably has a Young's Modulus which is greater than 107 N/m2 at 200 C.

The invention is illustrated by the following Examples in which reference is made to the accompanying drawings, wherein: Figure 1 shows the variation in tg for four excitation frequency values in dependence upon the service temperature of a 6% by weight chlorinated polymer; Figure 2 shows this same variation in tg S for a 20n e by weight chlorinated polymer; Figure 3 shows this same variation in tg a for 31% by weight chlorinated polymer; Figure 4 shows this same variation in tg a for a 38% by weight chlorinated polymer containing 75% by weight of 1 ,2-polybutadiene structures; ; Figure 5 shows the variation in tg a and in the elasticity modulus of a chlorinated and filler-containing polymer as a function of temperature: and Figure 6 shows the excitation response of a vibration-damped article according to the invention.

Examples I to 6 relate to the production of polymeric materials which may be employed as vibration damping elements in articles according to the invention; Example 7 relates to one such article according to the invention.

EXAMPLE 1.

A polymer containing 90% by weight of 1,2-polybutadiene structural units was chlorinated. To this end, the polymer was dissolved in methylene chloride and chlorination was carried out at OOC by reaction of a stoichiometric quantity of chlorine gas. Since the yields are quantitative, the reaction was terminated when all the chlorine has been consumed.

The amount m of chlorine to be introduced is calculated in accordance with the following formula: x M m =71. . ~ 56.9 54 where M represents the amount of polymer to be chlorinated and x represents the percentage af chlorine to be fixed.

For 5i g polymer, complete chlorination requires the introduction of 71 g of chlorine which corresponds to a chlorine content of 56.9% by weight.

The tg a and Young's modulus values of the material produced were measured by means of the apparatus marketed under the name "RHEOVIBRON-RV 2B".

Table 1 gives the values of the temperature of the damping maximum, the maximum tg 8 and the effective temperature range at 110 Hz (tg S > 0.5) for three chlorination levels of the polymer.

T110 ("C) represents the temperature of the damping maximum at 110 Hz whilst Tl and T2 define the temperature range in which tg a > o.s.

TABLE 1

1 Product % Cl (by weight) T110 (CC) tgA max T1. C T20C 1 6 11 1.65 2 28 2 20 105 0.65 92 115 3 31 110 0.90 78 122 It may be seen with reference to Figures 1, 2 and 3 that the damping effectiveness range of the chlorinated polymer is greater, the higher the percentage of fixed chlorine.

Comparison of these results with those obtained with a polyisoprene containing more than 60% of vinyl linkages shows that the effective range of the polymeric materials used as damping elements according to the invention is much greater because the polyisoprenes can only be used at a temperature above +30"C whilst products 2 or 3 above can be used at temperatures above +100"C.

EXAMPLE 2.

A polymer containing 75% by weight of 1,2-polybutadiene structures was chlorinated to a 38% by weight chlorine content by the method described in Example 1.

The mechanical characteristics of the product obtained are as follows: Temperature of the damping maximum at 3.5 Hz: 22"C Temperature of the damping maximum at 111 Hz: 33"C Temperature of the damping maximum at 1000Hz: 4l0C Maximum value of tug a 1.0 Elasticity modulus at 200C (110Hz) 3.86 x lO8N/m2 Figure 4 shows that the effectiveness range of this polymer (tg8 > 0.5) for example at a frequency of 110Hz, extends from +12"C to +68"C. A polymer of this type may therefore form part of vibration-damped articles which are widely used in industry.

Another characteristic of this polymer is that a high modulus is obtained.

Accordingly, this polymer may be used with advantage in articles where the damping element is a simple coating on the substrate.

EXAMPLE 3.

A polymer containing 60% by weight of 1 ,2-polybutadiene structures was chlorinated to a 550so by weight chlorine content by the method described in Example 1.

The mechanical characteristics of the product obtained are as follows: Temperature of the damping maximum at 110Hz : +600C Maximum value of tg a : 1.2 Effectiveness range at 1 10Hz : from 30 to 900C Elasticity modulus at +200C : 1.1 x 10Ñ/m2 Elasticity modulus at +500C : 3.2x 10'N/m2 Accordingly, this polymer has a high modulus at ambient temperature.

EXAMPLE 4.

The polymer obtained in accordance with Example 2 was vulcanised with the following components (parts by weight): Polymer 100 parts Cadmium stearate I part Zinc oxide 5 parts stearic acid 1 part MBT (2-mercaptobenzothiazole) 0.66 parts DPG (diphenyl guanidine) 1.33 parts Sulphur 2.6 parts The following results were obtained: Temperature of the damping maximum at 1000Hz : 400C Temperature of the damping maximum at 100Hz : 330C Maximum value of tg ô : 0.95 Elasticity modulus at 200C : 4.2x 10'N/m2 Elatticity modulus at 600C : 9x 10'N/m2 Accordingly, it is seen to be possible by vulcanisation to improve the stability under load of the chlorinated polymer without significantly altering its other properties.In particular, the damping coefficient of the vulcanised polymer at 20"C is substantially identical with that of the unvulcanised polymer.

EXAMPLE 5.

100 Parts by weight of the chlorinated polybutadiene obtained in accordance with Example 2 were filled with 50 parts of ISAF.HS black and vulcanised, the proportions of the other constituents of the vulcanisate being identical with those nf Example 4.

The following results were obtained: Temperature of the damping maximum at 110Hz : 300C Valueoftgaat 1 10Hz/300C : 0.50 Elasticity modulus at 200C : 2.4x 109N/mZ Elasticity modulus at 500C 1.6 x 109N/m2 Figure 5 shows the variations in the tg 8 and elasticity modulus of the material obtained as a function of temperature at 110Hz. It can be seen that the damping maximum is low (0.5) whereas the modulus is very high. Acbordingly, it is possible with this filled polymer to produce effectively vibration-damped articles of the simple coating type.

EXAMPLE 6.

A vulcanisation mixture of the polymer obtained in accordance with Example 2 filled with moulded vermiculite was prepared. The composition of the mixture was as follows (parts by weight): polymer 100 parts Zinc Oxide 5 parts Stearic acid 3 parts Cadmium stearate 2 parts Vermiculite 50 parts Paraffin 5 parts Sulphur 3.5 parts MBT 0.66 parts DPG 1.33 parts Vulcanisation was carried out in a press for 30 minutes at 1500C.

The characteristics of the filled vulcanisate are as follows: Temperature of the damping maximum at 110Hz 300C Maximum value of tug : 0.95 Elasticity modulus at 200C : 3.2x 109N/m2 It can be seen that both the elasticity modulus and the maximum tg value are very high. Accordingly, the material is particularly suitable for use in vibrationdamped articles of the simple coating type.

EXAMPLE 7.

A vibration-damped article of the simple coating type was produced with the polymer described in Example 5.

This article was produced from a steel plate measuring 1 mmx 15 mmx 100 mm to which a 2 mm thick layer of polymer was bonded.

The damping properties of the article obtained were measured by means of a viscoelasticimeter marketed under the name "BRUEL and KJAER". The plate was excited in its fixed-free position and the composite tg a value was measured by the method at three decibels.

Table 2 gives the tg a values for the three vibration modes: TABLE 2

Vibration mode Hz tga first mode 69.8 0.103 second mode 468.5 0.107 third mode 1218.9 0.112 The response of the damped article is shown in Figure 6. It can be seen that the resonance frequencies were attenuated by approximately 25 dB relative to those of the undamped plate as shown in dotted lines.

WHAT WE CLAIM IS: 1. A vibration-damped article which comprises a substrate contacted with a vibration damping element comprising a polymeric material, at least 50% of the structural units of which are based on 1 ,2-polybutadiene which is at least partially chlorinated.

2. An article according to claim 1 wherein the substrate is coated with the polymeric material.

3. An article according to claim 1 which comprises two layers of the substrate having the polymeric material disposed therebetween.

4. An article according to claim 1 wherein the substrate is provided with cavities and the polymeric material is disposed therein.

5. An article according to any one of the preceding claims wherein the substrate is metallic.

6. An article according to any one of the preceding claims wherein the polymeric material has a damping coefficient (as hereinbefore defined) of at least 0.5 over the frequency range 10Hz to lMHz.

7. An article according to any one of the preceding claims wherein the polymeric material is stable over the temperature range -5" to +1300C.

8. An article according to any one of the preceding claims wherein the polymeric material has a Young's Modulus of greater than 107N/m2 at 200 C.

9. An article according to any one of the preceding claims wherein from 75 to 100% of the structural units are based on 1,2-polybutadiene which is at least partially chlorinated.

10. An article according to any one of the preceding claims wherein the polymeric material has a chlorine content of from 6 to 56% by weight, based on the chlorinated polymer.

I I. An article according to any one of the preceding claims wherein the polymeric material is a copolymer.

12. An article according to any one of the preceding claims wherein the polymeric material contains a filler.

13. An article according to claim 12 wherein the filler is carbon black or vermiculite.

14. An article according to any one of the preceding claims wherein the polymeric material is vulcanised.

15. An article according to claim 1 substantially as described in Example 7.

16. An article according to claim 1 substantially as described with reference to Figure 6 of the accompanying drawings.

17. An article according to any one of the preceding claims in combination with a vibration source, and suitable for damping the same.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. TABLE 2 Vibration mode Hz tga first mode 69.8 0.103 second mode 468.5 0.107 third mode 1218.9 0.112 The response of the damped article is shown in Figure 6. It can be seen that the resonance frequencies were attenuated by approximately 25 dB relative to those of the undamped plate as shown in dotted lines. WHAT WE CLAIM IS:

1. A vibration-damped article which comprises a substrate contacted with a vibration damping element comprising a polymeric material, at least 50% of the structural units of which are based on 1 ,2-polybutadiene which is at least partially chlorinated.

15. An article according to claim 1 substantially as described in Example 7.