RE-CAPSULATION OF STYRENE BUTADIENE STYRENE (SBS), STYRENE BUTADIENE (SB) BLOCK CO-POLYMER WITH CROSS-LINKING AGENT FOR ASPHALT MODIFICATION

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1 RE-CAPSULATION OF STYRENE BUTADIENE STYRENE (SBS), STYRENE BUTADIENE (SB) BLOCK CO-POLYMER WITH CROSS-LINKING AGENT FOR ASPHALT MODIFICATION BY G. MOHAMMED MEMON * * Phaltech Corporation, Zulla Chase Place, Ashburn, Virginia Abstract Polymer modification of asphalts (PMA) with SB and SBS polymers is picking up speed worldwide at a growth rate of 5-7% annually. This raises interesting points concerning world manufactures ability to produce sufficient SB and SBS quantity to meet the demand in the paving market and secondly, the economic effects of PMA manufacturing costs. PhalTech Corporation of Ashburn, Virginia has developed and produced a worldclass cross-linking additive for SBS. The combing of PhalTechs cross-linking agent with SB and SBS generates a storage stable PMA with compatible and non-compatible asphalts utilizing compatible/non-compatible polymers and /or linear/radial polymers. PMA manufacturing typically is a four-step process: 1) addition of SB or SBS 2) dispersion of SB or SBS 3) addition of the cross-linking additive 4) stabilization. Each step plays a part in increasing the costs of PMA production and decreasing the production rate. If somehow any of the processing steps can be eliminated or improved, then the PMA production process can be made more economically viable. This will give the PMA producer a distinct market advantage i.e.: lower manufacturing/production costs. PhalTech s novel new approach will put the PMA manufacturing company ahead of the competition in his market. This new method has been designed and checked by

2 PhalTech s technical team in the laboratory and proved that it will reduce one full step of the PMA manufacturing process. It also helps on the second step i.e. faster dispersion of polymer. It also helps to acquire the desired rheological and PG plus properties faster as compared to normal PMA process. This novel new method is known as the re-capsulation of SB or SBS with the crosslinking agent. The cross-linking agent is a low melt chemical, which aids in the dispersion of the SB or SBS into asphalt, as opposed to polymer dispersion times without the cross-linking agent. The reduction of one full step in the PMA manufacturing process and quick dispersion of the SB or SBS will help save time to the PMA manufacturer, and as we all know, Time is Money. The polymer manufacturer who takes the lead in the re-capsulation process increases the value of their commodity product (SB or SBS) and can market this value added product at increased margins, without any additional capitol equipment into their currently available equipment for polymer manufacturing process. Introduction The polymer modification is well known in the asphalt industry, using different kind of polymers, like Ethylene Propylene Rubber (EPDM), Styrene Isoprene Styrene (SIS), Styrene Butadiene Styrene (SBS), styrene butadiene (SB) block co-polymer etc are well known for polymer modification of asphalt for paving application. Recently Styrene Butadiene back bone polymers are picking up momentum in the polymer modification of asphalt. The current economic hardship all over the world is creating a challenge for the asphalt chemist to come up with the new solution towards polymer modification of asphalt 1 developed a new polymer (di-block) having one mol of mono vinyl aromatic hydrocarbon and one mol of conjugated diene, the di-block co-polymer so made has higher vinyl content and the author claimed that higher vinyl content helps to avoid the use of cross linking agent to cross-link polymer molecule with asphalt molecule. This will results in a storage stable polymer modified asphalt (PMA) without the use of cross-linking agent. The author claims that this high vinyl

3 content block co-polymer works very well with different kind of compatible and noncompatible asphalt with low or high wax contents. have invented Cross-linking of polymers like polyimide, polyester etc., which provides very efficient method for water permeable and impermeable coatings by water-in-oil silicone emulsions cross-linkable into elastomer. Cross-Linkable material by polymerization in the presence of a catalyst with a stabilizing agent to ensure the cross-linking. Modified asphalts including polymer modified asphalt is very well known in the art of asphalt modification, as reported by Memon s 3 patent No.6,444,731 B1, issued on Sept. 03, In the said patent it was disclosed that furfural or vegetable oil was used to the asphalt modifier material like butadiene back bone polymers or crumb rubber to form a treated material dispersed quickly into asphalt. As the quick dispersion of these modifiers help the PMA manufacturers to produce PMA at an economical price, because lesser time of dispersion is equivalent to increase in production rate and reduction in the overhead cost. In the second step the state of the art was to generate a homogenous PMA product with simultaneous improvement on both low and high temperature rheological properties of the PMA. This led the PhalTech technical team to find a solution to the major concerned is economics. That of cost of manufacturing PMA, realizing that this re-capsulation gives higher profit, lower cost of product, higher sales and higher profit again. PhalTech is now proposing a novel new approach for the manufacture of PMA that will put the PMA manufacturer a head of the competition. This new method has been designed and reviewed and tested by PhalTech team in the laboratory. The results prove that this new approach will reduce one full step in the process of manufacturing PMA. This process also give an assist to a second step i.e. faster dispersion of the polymer

4 This innovative PhalTech procedure is defined as the re-capsulation of SBS with our cross-linking agent. The cross-linking agent is a low melt chemical which aids in the process of the dispersion of the SBS into asphalt. The dispersion time without this crosslinking agent is considerably longer, thus time consuming in dispersion is more expensive. As all business leaders know that time is money. The PhalTech product and process is a definite money saver, there is an additional attractive feature to the PhalTech re-capsulation, no additional equipment will be required to be purchased for this polymer manufacturing process. Experimental Three compatible asphalts, PG 64-22, and as well as three different types of compatible re-capsulated polymers SB, SBS (linear) & SBS (radial), were used in this study. The PMA was produced by a patented process by Memon 3, the re-capsulated or modified or treated polymer SB or SBS (linear) and or SBS (Radial) was added into the hot asphalt at C with continuous stirring. A high sheer mixer with a speed of around 5000 rpm (Silverson L4 R high sheer mixer) was used to disperse the recapsulated polymer (SB, or SBS (linear), or SBS (radial) into the various types of asphalts. This new step of re-capsulation was used to link the polymer with asphalt functional groups and the interaction time for dispersion and linking was around one hour to one and half hour for desired PG grade polymer modified asphalt (PMA). In this way of using the re-capsulated polymer makes the process easy and helps in making the PMA or its concentrate PMA without adding an extra or separate crosslinking activator or agent. The modified asphalts so obtained were then subjected for further rheological and other Superpave plus testing as follows: High temperature stiffness by Dynamic Sheer Rheometer (DSR) [4]. Low temperature rheological properties by Bending Beam Rheometer (BBR) [5].

5 Homogeneity or separation characteristics by PP5-93 [6] and by Fluorescent Microscopy method. Viscosity by Brooke Field Viscometer [7]. Ductility and Elastic recovery [8] Separation by Fluorescent Microscopy: A microscopic slide was prepared by placing a small amount of asphalt onto the slide and then covering it with a cover slip. It is then smeared by heating at the slide at C for 15 seconds. Turn on the fluorescent light in the microscope and then adjust the image under different levels of magnification (normally 400 magnification power), after the adjustment of the image capture it within the digital camera. The captured image is then transferred to the computer screen and then saved for further analysis. Results & Discussion. Asphalt Activator Feed Polymer Feed Wetting Tank High Shear Mixer Storage Tank Storage Tank Figure 1: Old way of making PMA Or PMA With Un-capsulated System

6 Polymer modification of asphalts (PMA) with SBS polymers is accelerating worldwide at a growth rate of 5-7% annually. This increase raises two interesting points for production and sale 1) A manufacturers ability to produce sufficient SBS quantity to meet the demand in the paving market and 2) The economic effects of PMA manufacturing costs. PMA manufacturing typically is a four-step process: 1) addition of SBS 2) dispersion of SBS 3) addition of the cross-linking additive 4) stabilization or polymer net-working with asphalt molecule. Each step plays a part in increasing the costs of PMA production and decreasing the production rate. Figure 1 & 2 are showing that the PMA made out of non-capsulated polymer is a four step process, whereas, the PMA made out of re-capsulated polymer is a two step process. Therefore, the two step process will take lesser time to make the PMA and also will be more economical way to make the PMA, not only that it will also increase the rate of PMA manufacturing for both one time and or concentrate. Asphalt Re-Capsulated Polymer Step I Cross-Linking Step II High Shear Mixer Storage Tank Storage Tank

7 F igure 2: Two step PMA Making System Using Re-Capsulated Polymer Table I shows the PG-Plus type properties of PMA made out of an asphalt (PG 64-22) and Re-Capsulated polymer (4%, normally used in case of un-capsulated PMA system) i.e without adding separate cross-linking agent. It also shows that except SB polymer (on the boundary line), both the SBS linear and radial passed whereas, SB failed by small margin. All three re-capsulated polymers showed significant improvement for both ductility and elastic recovery and as per protocol (PP5-93) showed very little separation between the top and the bottom portion of the tooth paste tube i.e. it is within the limit of the protocol. That means the PMA made by recapsulation can produce PG-Plus type polymer modified asphalts with storage stable capabilities. Polymer Cont PG- Viscosity Ductility Elastic Separation Re- Capsulated Grade Recovery (E.R) % (%) SB SBS Linear SBS Radial Table I: PMA Results using Re-Capsulated Polymer (4%) with PG Asphalt

8 Table II is another example of making PMA using different type of asphalt i.e. PG with lower amount of re-capsulated polymer (3%, as normally used for uncapsulated polymer system) and the trend for PG-plus and storage stability looks like same as un-capsulated system as well as with PG asphalt. Therefore, the recapsulated system works same for all rheological and PG-Plus properties of PMA that means the re-capsulated polymer is forming similar type of polymer networking as is formed by un-capsulated polymer in the PMA system. Polymer Cont PG- Viscosity Ductility Elastic Separation Re- Capsulated Grade Recovery (E.R) % (%) SB SBS Linear SBS Radial Table II: PMA Results using Re-Capsulated Polymer (3%) with PG sphalt Figure 3 is the fluorescent microscopic pictures of polymer modified asphalt with

9 Figure 3 : Un-linked/Storage un-stable PMA un-capsulated polymer at 150 minutes (un-linked/storage un-stable PMA). The picture is showing the fluorescent light in it, which is due to the double bond of butadiene of the polymer and the fluorescent light is a proof that the polymer molecule have not formed the net work with the asphalt molecule that means this kind of PMA will show heavy separation between the polymer and asphalt or in other words this kind of PMA is not storage stable and also it will not show significant improvements in PG- Pus properties. However, Figure 4 shows no fluorescent light that means the double bond of the butadiene is completely broken and allow the polymer molecule to get it linked with the asphalt molecule i.e. there is no more free polymer available in the asphaltic system, but the polymer is part of modified asphalt. These results were further confirmed by the cigar tube testing as is shown in Table I & II.

Figure 4: PMA made with Re-Capsulated Polymer showing proper networking & linking Conclusion Re-capulated polymer makes PMA faster with increased production rate.

10 Figure 4: PMA made with Re-Capsulated Polymer showing proper networking & linking Conclusion Re-capulated polymer makes PMA faster with increased production rate. Re-capsulated polymer makes PMA in two steps verses PMA made by uncapsulated polymer in four steps. Re-capsulated polymer makes the PMA with reduced processing steps. Re-capsulated polymer produces PMA more economical then PMA produced by un-capsulated polymer.. Re-capsulated polymer shows similar PG-Plus and Rheological properties. Re-capsulated polymer also produces Storage stable PMA as is PMA produced by un- capsulated polymer. Refrences

11 1. Keeping economics in mind Kulttz & Stephen Kluttz, R.Q., Stephen K.E., Process for preparing a bituminous binde composition USPTO , May 07, Barnlard, Deruelle, Giraud & Martin 2 (Branlard, P., Deruelle, Martial, Giraud, Y., Martin, N.,., Use of a crosslinkable silicone-based inverse emulsion for producing breathable water proof coatings USPTO , Nov..27, 2008) 3. Memon, G., M., Modified Asphalt USPTO#6,444,731 B1, issued on September, 03, The AASHTO Standard Test Method, no. TP5-93, Method for Determining the Rheological properties of Asphalt Binder, using a Dynamic Shear Rheometer (DSR). 5. The AASHTO Standard Test Method, no. TP1-93, Method for Determining the Flexural Creep Stiffness of Asphalt Binder, using the Bending Beam Rheometer (BBR). 6. The AASHTO Standard Test Method, no. PP5-93, Practice for the Laboratory Evaluation of Modified Asphalts (for separation ) 7. The ASTM Method no. D4402, using Brookfield Thermosel Apparatus, pp , V 04.04, The AASHTO Standard Test Method no.t , Ductility and Elastic Recovery, 2001.

Construction and Building Materials

Construction and Building Materials 36 (2012) 1001 1007 Contents lists available at SciVerse ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat Investigating