Evaluation of DISPERSIX in HCR Silicone Compounding

Transcription

1 Evaluation of DISPERSIX in HCR Silicone Compounding By Erick Sharp (Speaker) ACE Products & Consulting LLC, Uniontown, OH Miles Dearth The SEFA Group, Lexington, SC Bill Black The SEFA Group, Lexington, SC Presented at the 2016 International Silicone Conference A Rubber and Plastic News Event May 17 th & 18 th Akron, OH

2 Abstract A multi-factor, general factorial designed experiment was performed to investigate the processing of highly extended HCR silicone molding and extrusion compounds with aluminosilicate ceramic (ASC) microspheres. The factors selected for experiments are the presence, particle size, dose level and grade of microspheres. This study measured dependent variables of a) cycle time, b) MDR properties, c) dispersion, d) physical properties and e) mold release. Introduced in this study is DISPERSIX a new line of inorganic multi-functional process aids which the data in this study indicate have significant effects on processing efficiency and the balance of property improvements not previously available to silicone compounders.

3 Introduction of DISPERSIX Microspheres DISPERSIX aluminosilicates are recovered from various mining and post-industrial byproduct streams and converted to micro-spherical ceramics by a patented thermo-oxidative process. Once returned to their pristine mineral state they are size classified and modified with inorganic and organic reactants for faster processing and superior properties. Experiment Equipment All trials were mixed on a 5 liter tilt body lab mixer with tangential rotor configuration and milled on a 6x12 lab mill. Figure 1 Figure 2

4 Raw Materials Molding Trial Figure 3 Extrusion Trial Figure 4

5 Formulation Molding Trial Figure 5 Extrusion Trial Figure 6

6 Mix Procedure Molding Formulation 1. Add JFD 2041, JFD 0620, Precipitated Silica and DISPERSIX (except for control) a. Mix to 117 F 2. Add ACE-SD-BIO, ACE-SD-HS2, ACE-SD-MR1, VTEO and ½ Minusil10 a. Mix to 130 F 3. Add remaining Minusil Drop at 135 F 5. Ten passes on lab mill Extrusion Formulation 1. Add JFD 2041, JFD 2071, ACE-SD-HS9, ACE-SD-CaO, ACE-SD-MgO, ACE-SD-MMO a. Mix 30 seconds 2. Add ½ Minusil 10 and DISPERSIX (except for control) a. Mix to 125 F 3. Add remainder of Minusil 10 a. Mix to 150 F 4. Add DCBP a. Mix 60 seconds and drop 5. Ten passes on lab mill Measurable Values a. Mixing Cycle Time a. Seconds b. MDR a. Parameters i. Molding formulations: 6 at 355 F ii. Extrusion formulations: 6 at 250 F b. Values i. ML ii. TS2 iii. Tc50 iv. Tc90 v. MH

7 c. Physical Properties a. Parameters i. Molding formulations prepped 6 at 355 F ii. Extrusion formulations prepped 6 at 250 F b. Values i. Specific Gravity ii. Tensile (Mpa) iii. Elongation iv. 100% Modulus v. 200% Modulus vi. Tear die b vii. Compression Set (method B/ Plied) d. Other a. Amp Draw Cycle Times Results Total mixing cycle times were reduced by over 40% with the DISPERSIX microspheres in the molding formulation compound (Figure 7). Figure 7

8 FIG. 8 MDR Data Compared to the control, compounds containing DISPERSIX ASC microspheres exhibited lower Tc90 cure times by 6 seconds, 11.4 seconds and 9.6 seconds, respectively (Figure 9). This is thought to be due to the improved dispersion of the peroxide curing agent because DISPERSIX spheres act similarly to type II co-agents. It is likely that the amounts of peroxide could be reduced when using the DISPERSIX microspheres. Mooney-High (MH) as shown in FIG. 10 increases less than two Mooney units when DISPERSIX microspheres are present. Relative MH differences between versions of DISPERSIX microspheres are thought to be the result of differences in the cure network from different surface treatments.

9 Minutes FIG. 9 MOLDING SCORCH DATA Control Dispersix Dispersix 4PC 4PC 3 Ts Dispersix 4PC 4 Tc Tc FIG. 10 MH - MOLDING Control Dispersix 4PC Dispersix 4PC 3 Dispersix 4PC 4 MH

10 FIG. 11 ML - MOLDING Control Dispersix Dispersix Dispersix 4PC 4PC 3 4PC 4 ML

11 EXTRUSION COMPOUNDS Total mixing cycle times (Figure 13) were reduced by over 12% with the DISPERSIX microspheres in the extrusion formulation compound (figure 12). Figure 12 FIG. 13

12 Minutes FIG. 14 EXTRUSION SCORCH DATA F Ts2 Tc50 Tc90 Control PC FIG. 15 ML - EXTRUSION ML Control PC 2.51

13 FIG. 16 MH - EXTRUSION MH Control PC 9.84

14 SHORE A Physical Properties Conventional process aids are typically designed to improve productivity but sometimes result in a sacrifice in physical properties. The research done by SPHERIX Mineral Products has focused on the development of aluminosilicate ceramified microspheres that improve productivity while maintaining or improving physical properties at low dosages. Surface modification of these microspheres optimizes adhesion and crosslinking to the matrix elastomer for enhanced mixing, dispersion, and flow efficiencies along with reinforcement in the cured state without significant changes in hardness, scorch and cure rate. Molding formulations containing 5 phr DISPERSIX microspheres outperformed the control compound on every physical property measured. The experimental extrusion formulations exhibited physical properties that were comparable to the control with a notable improvement in mixing efficiency. FIG. 17 Molding Hardness Durometer Control 76 Dispersix 4PC 77 Dispersix 4PC 3 78 Dispersix 4PC 4 77

15 % PSI FIG. 18 Molding Tensile Tensile, psi Control Dispersix 4PC Dispersix 4PC Dispersix 4PC FIG. 19 Molding Elongation % Control Dispersi x 4PC Dispersi x 4PC 3 Dispersi x 4PC 4 Elongation %

16 FIG Molding Modulus 100% Modulus 200% Modulus Control Dispersix 4PC Dispersix 4PC Dispersix 4PC FIG. 21 Molding Tear Tear Die B, lbs Control 93.8 Dispersix 4PC Dispersix 4PC Dispersix 4PC

17 FIG. 22 Molding Compression Method B, Plied Control 33.6% Dispersix 4PC 27.1% Dispersix 4PC % Dispersix 4PC %

18 FIG. 23A Extrusion Physical Properties Duromete r Elongation % 100% Modulus 200% Modulus Tear Die B, lbs Control PC FIG. 23B Extrusion Physical Properties Specific Gravity Tensile, (Mpa) Control PC

19 Energy Consumption The physical dispersive action of the microspheres is enhanced by surface chemistry and improved silica reinforcement while the Amperage draw during compounding decreased by up to 50% compared with the control. FIG. 24 Amp Draw - Molding Average AMP Draw Control 12 Dispersix 4PC 6 Dispersix 4PC 3 7 Dispersix 4PC 4 7

20 Dispersion By visual observation the compounds with the DISPERSIX microspheres had better dispersion and less powder agglomerations in the milled slab. FIG. 25 Control Batch FIG. 26 DISPERSIX Batch

21 Conclusions HCR silicone compounds containing DISPERSIX microspheres consistently processed cleaner, quicker and with better dispersion. The mixer body was cleaner and the batch discharged better with the DISPERSIX microspheres compounds. The DISPERSIX microspheres acted in a ball bearing like effect to break down the raw materials and improve dispersion. This had a dramatic improvement on the mixing cycle time. The cycle time improvement seems to be greater on formulations that have a higher level of reinforced filler being added. When molding slabs for testing the compounds with DISPERSIX microspheres had better release from the mold. This was a consistent observation throughout the entire study. The development objectives of SPHERIX Mineral Products as demonstrated by the foregoing experimental mixes in obtaining process improvements without an adverse effect on the rheology and physical properties have been apparently achieved. The better dispersion apparently further enhanced the rheology. It is likely that the peroxide level could be slightly reduced when used in DISPERSIX compounds. In molding compounds with a high level of precipitated and ground silica, significant improvements in physical properties and process efficiency were demonstrated. Experiments with predispersed fumed silica-containing extrusion compounds showed comparable physical properties with processing efficiency benefits in the use of DISPERSIX microspheres. Further study in the dispersion of fumed silica in silicone base compounds is warranted. The data in the foregoing studies supports the general conclusion that DISPERSIX microspheres provide substantial cycle time improvements, enhanced dispersion and reduced power load, while maintaining equal or better physical properties in the finished compound. Acknowledgements A special thanks to John Summers and Polychem Dispersions for their assistance in running these trials. A special thanks to HB Chemical for providing raw materials for these trials.