SURFACE MODIFICATION OF SILICONES

Abstract

A process for modifying a silicone elastomeric-based surface of an article where the coefficient of friction (COF) of the silicone elastomeric-based surface is generally reduced by at least 5% is disclosed. The process comprises subjecting the silicone elastomeric-based surface of the article to vacuum ultraviolet (UV) radiation.

Claims

1. A process for modifying a silicone elastomeric-based surface of an article, said process comprising: subjecting the silicone elastomeric-based surface of the article to vacuum ultraviolet radiation; wherein the coefficient of friction of the silicone elastomeric-based surface is reduced by at least 5%.

2. The process according to claim 1, wherein the silicone elastomeric-based surface of the article consists of silicone elastomer.

3. The process according to claim 2, wherein the silicone elastomer is the reaction product of a hydrosilylation or peroxide cure of an alkenyl-functional organopolysiloxane and a SiH functional organopolysiloxane.

4. The process according to claim 1, wherein the article is a molded article made of silicone elastomer.

5. The process according to claim 4, wherein the molded article is a case for an electronic device, an optical device, a medical device, a sport and leisure device, or a toy.

6. The process according to claim 4, wherein the molded article is formed by extrusion.

7. The process according to claim 4, wherein the molded article comprises tubing.

8. The process according to claim 4, wherein the molded article is a car part or a case for an electronic device and wherein the silicone elastomer is overmolded over at least part of the article.

9. The process according to claim 1, wherein the article is a silicone elastomer coated article.

10. The process according to claim 1, wherein the article is coated, overmolded, molded or extruded, and is subsequently subjected to vacuum ultraviolet radiation.

11. The process according to claim 1, wherein the vacuum ultraviolet radiation is performed using an excimer lamp.

12. The process according to claim 1, wherein the vacuum ultraviolet radiation is performed using a low-pressure mercury lamp.

13. The process according to claim 1, wherein the vacuum ultraviolet radiation is performed on a conveyor belt.

14. An article having a silicone elastomeric-based surface, which surface is modified by the process according to claim 1.

15. The article according to claim 14, wherein the silicone elastomeric-based surface has a modified surface layer of less than 1 mm in thickness.

16. The article according to claim 14, wherein the article is a molded silicone article free of a non-silicone elastomeric coating layer.

17. (canceled)

18. A case for an electronic device or an optical device or a medical device or a sport and leisure device or a toy formed by the process according to claim 1.

Description

EXAMPLES

[0067] Silicone elastomer (or silicone rubber) pieces were prepared from commercially available liquid silicone rubber compositions, Xiameter RBL-9200-30 LSR, Xiameter RBL-9200-50 LSR and Xiameter RBL-9200-70 LSR. These compositions represent general-purpose injection-molding materials, which are suitable for a wide range of typical silicone rubber applications. The digits 30, 50 and 70 indicate the Shore A hardness of the cured materials obtained from these compositions. Typically, these compositions are provided in two parts form (parts A and B), which are combined prior to curing (reacting).

[0068] Equivalent amounts of the Part A and B of the individual LSR have been mixed, de-aired and poured into a 20210832 mm (LWH) mold and press-cured for 10 min at 120 C. The cured plates have been then irradiated with a low pressure mercury lamp (wavelength 185 nm and 254 nm) of type Heraeus Noblelight, Soluva 4.20 VUV Modul (UV Intensity 140 mW/cm2, for a wave length of 254 nm, at distance of 10 mm; providing for an irradiation area of 230140 mm), for either 3 min or 5 min respectively.

[0069] The cured plates (with and without irradiation) have been tested for change in coefficient of friction. The results are listed in Table 1.

[0070] The static and dynamic coefficients of friction were measured using a Zwick device, set up according to ISO8295 from Jan. 10, 1995, where a sliding reinforcing plate is moved along the test specimen and friction is measured. The parameters were set as follows: sliding trail of 300 mm length and 150 mm width, a moveable device of 200 g having a Teflon surface, moving at a speed of 150 mm/min, with a force of 200 N.

[0071] The coefficients of friction, both static and dynamic are evidenced to be reduced by more than 10% of the initial value, and even more than 50% when comparing the untreated materials and the materials that were irradiated for 5 minutes. The untreated materials Comparative examples 1 and 2 have defects in sliding because the surface is not slippery and some friction and elasticity interaction prevent the moving device from sliding smoothly on the surface.

TABLE-US-00001 Irradiation Static Dynamic time coefficient of coefficient of (seconds) friction friction Comparative RBL-9200-30 0 15.8* (high (10.0 s)- example 1 variability) defects in sliding Example 1 RBL-9200-30 180 7.5 4.8 Example 2 RBL-9200-30 300 1.9 2.2 Comparative RBL-9200-50 0 15.1* (high (8)-defects in example 2 variability) sliding Example 3 RBL-9200-50 180 1.3 1.5 Example 4 RBL-9200-50 300 1.8 0.3 Comparative RBL-9200-70 0 9.4 6.8 example 3 Example 5 RBL-9200-70 180 3.0 2.1 Example 6 RBL-9200-70 300 0.7 1.0