acrylic pressure sensitive adhesives having controlled ... · acrylic pressure sensitive adhesives...

ACRYLIC PRESSURE SENSITIVE ADHESIVES HAVING CONTROLLED PLACEMENT OF FUNCTIONAL GROUPS Christopher L. Lester, Ph.D. Performance Adhesive Center, Avery Dennison William L. Bottorf, Performance Adhesive Center, Avery Dennison Abstract We report herein the synthesis of acrylic polymers with controlled molecular weight, architecture and placement of reactive functional groups. The influence of architecture and functional group placement on visco-elastic properties and corresponding pressure sensitive adhesive attributes are reported. The novel controlled architecture acrylic polymers allow for the development of high solids solution adhesives at low viscosities and 100% solids warm melt compositions with processable rheology. Furthermore, the controlled architecture polymers display enhancements in adhesive performance. Introduction (Meth)acrylic (co)polymers have been studied and used industrially for more than 50 years. Because there is such a broad array of (meth)acrylic monomers, a vast range of visco-elastic properties can be attained. Such a wide array of properties allows for these materials to function well in applications in adhesives and elastomers. Relative to other copolymers, (meth)acrylic copolymers have several significant advantages. Advantages include superior UV stability, excellent optical clarity, and oxidative/temperature resistance relative to natural rubber and styrenic block copolymers. (Meth)acrylic copolymers display excellent performance characteristics by macromolecular architecture i.e., molecular weight, degree of branching etc. and cross-linking reactions. The cross-linking reactions are afforded in a variety of ways due to the many different functionalities that are provided by the variety of commercially available functional (meth)acrylic monomers. High performance adhesives are often processed by casting films from relatively low concentrations in organic solvents. Regulatory pressures exist and continue to grow for the manufacturers of solution acrylic pressure sensitive adhesives (PSAs) to reduce the use of organic solvents. In addition to regulatory pressures, the economics of either collecting, or incinerating the evaporated solvents can be quite costly. Finally, certain applications requiring thick films of PSA can be difficult or slow to manufacture because of film defects caused by trapped residual solvents. The economic, regulatory, and quality issues with solvent acrylic PSAs could be significantly mitigated if the solids content could be increased dramatically without loss of PSA performance. Controlling polymer architecture has been a subject of significant research over the past 50 years. It has been well established that improved control of polymer architecture can lead to improved performance and has the capability to decouple countercurrent properties. Previously reported architectures include block copolymers, telechelic polymers, and random polymers of controlled molecular weight. While, the aforementioned architectures all provide unique properties, they also have disadvantages. Random copolymers often require significant amounts of cross-linking to attain adequate cohesive strength which ultimately reduces adhesion properties. Phase separated block copolymers when appropriately

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formulated can display excellent PSA performance but are known to have high melt viscosities which require high processing temperatures. The high processing temperature can then limit the types of functional groups used in the system. Telechelic polymers by definition have reactive functional groups placed exactly at the end-groups and nowhere else in the backbone. They often have the disadvantage of requiring multiple steps in their synthesis and there are limits on the degree of functionality achieved at a given molecular weight. The functional groups then serve solely to increase linear molecular weight and/or form networks in which free polymer chain ends are eliminated. Telechelic polymers consequently yield high strength elastomeric materials but lack the viscous liquid character critical to PSA performance. In the past 15-20 years a variety of controlled radical polymerization techniques have been developed to afford good architectural control of (meth)acrylic monomers. These techniques typically are tolerant to a wide variety of monomers and functional groups as opposed to previous techniques like anionic or group transfer polymerization. A substantial amount of fundamental research has been performed to understand these types of polymerization and a thorough review has been edited by Matyjewski.1 Reversible Addition Fragmentation chain Transfer (RAFT) polymerization is one such technique that has been shown to work exceedingly well with a wide variety of (meth)acrylic monomers yielding excellent control of molecular weight and polydispersity.2 The RAFT mechanism for controlled polymerization is well understood and reported extensively.1-3 While some examples of controlled architecture acrylic PSAs have been reported very little work has been done to explore the influence of reactive functional group placement. It is reported herein the use of controlled radical polymerization for the synthesis of novel acrylic polymers of controlled molecular weight and placement of reactive functional groups. The influence of polymer architecture and particularly the placement of reactive functional groups used for subsequent cross-linking on visco-elastic properties and PSA performance are reported. These types of architectured acrylic polymers afford the development of high performance pressure sensitive adhesives at high solids in organic solvents at moderate to low viscosities. Furthermore, with either complete removal of the solvent or via bulk polymerization 100% solids, warm melt compositions are possible. Experimental Base acrylic esters such as 2-Ethylhexyl Acrylate (EHA), Butyl Acrylate (BA), tert-Butyl Acrylate (tBA), and Isobornyl Acrylate (IBOA) were obtained from various commercial suppliers. Prior to use in controlled radical polymerizations the inhibitor was removed with alumina packed columns. Functional monomers such as Methacrylic Acid (MAA), Isobutoxymethylol acrylamide (IBMA), and Methacryoloxypropyl Tri-methoxysilane (MPtMS) were all obtained from commercial suppliers and used as is. Dibenzyl trithiocarbonate (DBTTC) was used as received and is shown in Scheme 1. Also in Scheme 1 is a depiction of how monomers are incorporated upon sequential addition. All of the polymerizations were initiated with Azobis(isobutyronitrile) (AIBN). The polymers were all made in organic solvents, most typically Ethyl Acetate. Unless otherwise stated all MAA containing polymers were formulated with a stoichiometric equivalent (relative to equivalents of MAA) of a multifunctional aziridine cross-linker (Trimethylol Propane Tris (N-methyl Aziridinyl) Propionate (TMP)). All samples were coated at approximately 2.0mil adhesive thickness onto 2.0mil mylar. The coatings were all air dried for 10 minutes and placed in a forced air oven for 5 minutes at 130oC and closed with 100% solids platinum cured silicone paper liner.

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Molecular weights were measured using a Polymer Standards Services GPC outfitted with a refractive index detector and calibrated using polystyrene standards. Solution viscosities were measured using a Brookfield RVT viscometer. Spindle and spindle speeds were selected such that a torque value of 40-80% was achieved for optimal accuracy. A Buchi Rotavap R-200 was used to yield a solvent free copolymer by heating the copolymer to 65°C and by pulling a vacuum to <25mbars. Meltflow viscosity was measured on a TA Instrument AR 1000 rheometer configured with a cone and plate clamp. This experiment was performed with a temperature sweep starting at 25°C and finishing at 99.8°C. The Temperature ramp rate was set to a constant 1°C/minute and a shear rate(1/s) of .02864. Dynamic mechanical analysis (DMA) was performed on a TA Instrument AR-1000 rheometer using parallel plate clamps. 1.0mm thick samples were placed in the clamp and annealed at 50oC for 10 minutes to ensure good adhesion. The samples were then cooled to -80oC for 10 minutes and ramped at 3oC per minute up to 180oC. During the temperature ramp the sample was oscillated at a frequency of 10 rad/s. Unless otherwise noted, the following test methods were used for evaluating the adhesive properties of the acrylic polymers. PSA PERFORMANCE TEST METHODS Test Condition 180° Peel a, b, 15 Minute Dwell 24 Hour Dwell Shear Strength c Shear Adhesion Failure Temp.(SAFT) d

Scheme 1. Chemical structure of dibenzyl trithiocarbonate (DBTTC) and polymers

after a single monomer addition followed by a subsequent monomer addition.

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(a) Peel, sample applied to a stainless steel panel with a 5 pound roller with 1 pass in each direction. Samples conditioned and tested at 23°C. (b) Peel, sample applied to a high density polyethylene or polypropylene panel with a 5 pound roller with 5 passes in each direction. Samples conditioned and tested at 23°C. (c) Shear: 1 kg weight with a 1/2 inch by 1 inch overlap. Sample applied to a stainless steel panel with a 10 pound roller with 5 passes in each direction. Samples conditioned and tested at 23°C. (d) SAFT: 1000 gram weight, 1 inch by 1 inch overlap (2.2 pounds/square inch). Sample applied to a stainless steel panel with a 10 pound roller with 5 passes in each direction. Samples conditioned for 1 hour at 23°C and 15 minutes at 40°C. Temperature increased by 0.5°C/min. until failure.

Results and Discussion Figure 1 depicts the general relationship between molecular weight and solution/melt viscosity. From a processing standpoint, it would be desirable to have a lower molecular weight in order to achieve higher solids at a lower viscosity or a manageable melt viscosity. However the performance of the material dictates that the molecular weight of typical PSAs be much higher. This is illustrated in Figure 2 by displaying the typical relationship between molecular weight and generic PSA performance.4 Typical acrylic PSAs observe an increase in peel adhesion and cohesive strength with increasing molecular weight to some maximum at which the cohesive strength exceeds the adhesive strength. Then subsequent increases in molecular weight result in higher cohesive strength at the expense of adhesion.

Molecular Weight

Vis

cosi

ty (c

ps)

105 107

103

105

Molecular Weight

Vis

cosi

ty (c

ps)

105 107

103

105

Figure 1. Viscosity as a function of molecular weight

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High molecular weight Low molecular weight

a. b.

Figure 3. Typical PSA performance as a function of cross-linking level for a. high molecular weight polymer and b. low molecular weight polymer.

Figure 3 shows generic PSA performance as a function of cross-link density for a low and a high molecular weight PSA. One can see that the higher molecular weight polymer displays a broader range of cohesion/adhesion properties while the lower molecular weight material is much more limited. One potential route to break this paradigm is to be able to control the cross-link density by placing reactive

Figure 2. Typical PSA performance as a function of molecular weight.

Molecular Weight

PeelShear

Molecular Weight

PeelShear

Peel

/She

ar

Molecular Weight

PeelShear

Molecular Weight

PeelShear

Peel

/She

ar

Cross-linking

PeelShear

Cross-linking

PeelShear

Cross-linking

PeelShear

Cross-linking

PeelShear

Peel/Shea

Peel/Shea

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functional groups towards the polymer end-groups. This leaves mobile polymer in the middle and free chain ends for wet out.

b.

a.

= Acids, hydroxyls, anhydrides, epoxides, hydroxy acrylamides, alkoxy-silanes, benzophenone…..

b.

a.



Figure 4. Depiction of polymers with functional groups distributed a. in the end regions

of the polymer and b. randomly distributed throughout the polymer

Figure 4 is a simple depiction of the types of polymers being discussed in this study. Drawing a. is a representation of a polymer made by RAFT in which functional monomers are added in such a way to result in placement in the outer regions of the polymer. Drawing b. is a representation of a polymer made by RAFT or standard free-radical techniques in which the functional monomers are incorporated randomly along the polymer.

Table 1.

Backbone Composition 68% BA/ 32% tBA, 8 MAA per chain total (4 MAA per end)

RAFT/Architectured RAFT/Random Standard/Random Mn 56,700 52,562 99,000 Mw 69,600 69,860 863,000 PDI 1.2 1.32 8.7

Solids 71.9% 71.7% 35.6 Solution viscosity

10,300 cps 9,760 cps 9,700 cps

Melt viscosity (100oC)

<10,000 cps <10,000 cps NA

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Table 1 describes the various polymers used in the study with regards to molecular weight, solids, solution viscosity, and where applicable melt viscosity of devolatilized polymers. Copolymers of BA, tBA, and MAA at the same weight ratios were synthesized using RAFT and standard free radical techniques to provide three distinct architectures. The first column labeled RAFT/Architectured is a low molecular weight low polydispersity polymer in which the acid groups have been segregated into the end regions of the polymer as depicted in Figure 4b. The amount of MAA used and the theoretical molecular weight of the polymer yield an average of 8 MAA moieties per chain or 4 per end region. In this case the MAA is polymerized in the first 5000g/mole of the polymer. The second column entitled RAFT/Random is another low molecular weight low polydispersity polymer in which the acid groups have been randomly distributed through the entire polymer as shown in Figure 4b. The third column is the composition polymerized with standard techniques to provide a high molecular weight broad polydispersity control. The RAFT examples display solids contents in excess of 70% with viscosities at approximately 10,000cps. Additionally these polymers upon devolatilization exhibit processable melt viscosities. By contrast the Standard/Random high molecular weight polymer displays a viscosity of 10,000cps or less only when diluted to a solids content of 35.0%. Furthermore upon devolatilization the Standard/Random high molecular weight polymer becomes an intractable solid that doesn’t have a relevant melt viscosity.

-50.0 -25.0 0 25.0 50.0 75.0 100.0 125.0 150.0 175.0 200.0temperature (°C)

0

0.2500

0.5000

0.7500

1.000

1.250

1.500

1.750

2.000

2.250

2.500

tan(

delta

)

RAFT ArchitecturedRAFT RandomStandard High Mw Random

Figure 5. Tan delta as a function of temperature for BA/tBA copolymers with eight MAA moieties per chain of varying architecture.

Upon drying and cross-linking the three polymers dynamic mechanical analysis was performed to understand the differences in the visco-elastic properties and adhesive performance. Figure 5 is a plot of tan delta as a function of temperature for the different materials. All of the polymers display an identical peak tan delta at approximately 0 oC which means that they are all equal in glass transition temperature. At temperatures greater than the Tg the materials begin to differ substantially. For example the two low molecular weight low polydispersity polymers display nearly equivalent tan delta values at 25 oC while the high molecular weight random copolymer displays substantially lower values. The lower tan delta

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values are indicative of a higher molecular weight and consequently higher modulus or stiffer material. The random copolymer made via RAFT begins to display substantially lower tan delta values at temperatures greater than 30 oC. In fact the low molecular weight random copolymer has tan delta values equivalent to that of the high molecular weight polymer at approximately 100 oC indicating equivalence in aggregate crosslink density. In contrast the architectured RAFT polymer displays a much different tan delta profile. The tan delta values remain higher than either random copolymer control throughout the temperature range which is indicative of higher molecular weight between cross-links. The differences in bulk rheology manifest in markedly different pressure sensitive adhesive performance. Table 2 displays the pressure sensitive results below. The RAFT/Architectured polymer displayed high initial adhesion to steel with significant build observed to the point the adhesive was cohesively splitting. Both random copolymers displayed relatively low initial adhesion with much lower ultimate adhesion than the architectured version. The adhesion to olefin substrates was markedly higher for the architectured RAFT polymer relative to the random controls. Interestingly, no cohesive strength has been sacrificed with the enhancement in adhesion observed as evidenced by equivalent shear and SAFT values. In order to understand the influence of the concentration of acid groups in the end region of the polymer a series of polymers were synthesized in the same manor as that of the aforementioned RAFT/Architectured.

Table 2 High Strength Pressure Sensitive Adhesives.

Test RAFT Architectured

RAFT Random

Standard High Mw

Random 180! Peel to Stainless Steel 15 min Dwell (lbs/in)

3.56 2.08 1.82

180! Peel to Stainless Steel 72hr Dwell (lbs/in)

7.52 sp Tr 3.06 2.00

180! Peel to HDPE 72hr Dwell (lbs/in)

0.5 0.2 0.29

180! Peel to Polypropylene 72 hr Dwell (lbs/in)

1.9 0.58 0.94

SAFT, 1kg/Sq. In (Failure Temperature, ºC)

>200 >200 >200

Shear, 1kg/Sq. In (Failure Time , Mins)

>10000 >10000 >10000

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Table 3

Backbone Composition 68% BA/ 32% tBA Varying MAA Number MAA per end

1 2 4 8

Weight % MAA 0.28 0.56 0.92 1.84 Mn 51,921 53,600 56,700 55,300 Mw 69,587 68,800 69,600 67,900 PDI 1.34 1.30 1.20 1.20 Solids 72.5% 74.5% 71.9% 66.5% Solution viscosity 9,000 cps 16,680 cps 10,300 cps 7,200 cps

Table 3 describes polymers and physical characteristics of these polymers in which the number of MAA groups were varied from one through eight (two to sixteen per polymer chain). The molecular weight and PDI of the polymers were all similar and largely the solution viscosities were the same. However upon cross-linking the polymers the bulk rheology and pressure sensitive adhesive performance changed dramatically. Figure 6 is a plot of tan delta as a function of temperature for the polymers described in Table 3. All of the polymers display identical peak tan delta temperatures because of the identical backbone compositions. The polymer with one MAA per end region exhibits substantially higher tan delta values at all temperatures above the glass transition indicating that the material has a very low cross-link density. Upon increasing the MAA level to two per end significantly lower tan delta values are observed which correlates to a more cross-linked material. This trend is continued in the polymer with four acids per end region. However when increasing from four to eight MAA groups per end region, further increases in the cross-link density are not apparent.

-55.0 200.0temperature (°C)0

0.5000

1.000

1.500

2.000

2.500

3.000

tan(delta)

1248

Figure 6. Tan delta as a function of temperature for architectured BA/tBA

copolymers with varying amounts of MAA in polymer end regions.

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The PSA test data are shown in Table 4 for the polymers with varying amounts of acids. As one would expect from the rheology data, the polymer with one MAA per end resulted in an adhesive that exhibits cohesive failures on all test substrates with modest peel values and low shear. The material with two MAA per end yielded significantly improved performance in that it displayed high peels on stainless steel building to cohesive failure and moderate adhesion on olefins. Higher shear is observed and it narrowly misses passing the maximum SAFT. The four MAA per end polymer displayed slightly lower peel adhesions than the one with two MAA groups but still displayed values that would be considered high while passing both the shear and SAFT tests. Upon increasing to eight MAA per end region the SAFT and shear performance are maintained but the peel performance on steel begins to decrease transitioning to an adhesive failure. Also the adhesion to olefin has been adversely affected.

To illustrate the versatility of synthesizing acrylic polymers and adhesives with controlled radical techniques Table 5 describes a variety of other polymer compositions and types of cross-linking. The pressure sensitive adhesive performances of these formulations are displayed in Table 6 below. The polymers described display high solids with relatively low viscosities. Sample 1 is a BA homopolymer polymerized with three self condensing methylol acrylamide (IBMA) monomers per end region and formulated with 20% of a terpene phenolic tackifier. Sample 1 exhibits moderate adhesion to stainless steel, average adhesion to olefin substrates with relatively high shear. Sample 2 is an EHA homopolymer with three self condensing alkoxysilane monomers per end region and formulated with 40% of a polyterpene tackifier. Interestingly, this particular formulation displays high adhesion across all substrates with moderate shear and SAFT results. Sample 3 is a similar composition to the polymers described in Table 4 but differs in that it utilizes one self condensing alkoxysilane monomer per end region in place of the acid aziridine crosslinking. It is interesting to note that only one alkoxy-silane functionality yielded substantially higher shear than the analogous MAA containing polymer. Finally

Table 4

High Strength Pressure Sensitive Adhesives.

Test 1

2 4 8

180! Peel to Stainless Steel 15 min Dwell (lbs/in)

3.28 cohesive 4.73 mixed 3.56 2.23


3.59 cohesive 8.11 cohesive 8.11 cohesive 4.81


3.36 cohesive 0.57 0.5 0.18


3.0 cohesive 1.25 zipping 2.0 NA


NA 193.0 >200 >200


2.4 cohesive 8942.6 mixed >10000 >10000

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Sample 4 is an EHA/IBOA copolymer with four methacrylic acids per end region with aziridine crosslinking. Sample 4 as a consequence of its low surface energy backbone displays excellent adhesion to not only the steel substrates but to the olefin substrates as well while exhibiting relatively high cohesive strength as evidenced by the shear and SAFT numbers.

Table 5

Various Backbone compositions, formulations and cross-linkers Sample 1 2 3 4 Backbone composition

BA EHA 68BA/32tBA 65EHA/35IBOA

Cross-linking monomer/# per end

IBMA/3 MMtMS/3 MMtMS/1 MAA/4

Tackifier level/type

20% Terpene phenolic

40% Polyterpene

NA NA

Mn 62,840 35,000 87,100 54,600

Mw 86,520 61,950 130,000 87,360 PDI 1.38 1.77 1.5 1.6 Solids 71.6 73.6 65.8 71.5 Solution Viscosity

4,800 cps 2,850 cps 9,800 cps 8,700 cps

Table 6


Test BA

EHA 68BA/32tBA 65EHA/35IBOA

180! Peel to Stainless Steel 15 min Dwell (lbs/in)

2.5 6.84 cohesive 4.20 8.20 cohesive


4.5 7.11 cohesive 5.96 mixed 8.70 cohesive


1.2 6.44 cohesive 0.41 3.11


1.5 zipping 6.26 cohesive 1.59 zipping 5.5 cohesive zipping


NA 88.0 adhesive 89.0 94.0


>10000 2460.2 cohesive

773 5844

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All of the aforementioned systems consisted of a single functional monomer and corresponding cross-linking system. The acid/aziridine systems offer advantages such as the adhesion promotion of the acid groups and the facile covalent cross-linking. However, these systems have the disadvantage of being two part systems. The self condensing systems in particular the alkoxy silane monomers are advantageous in that they are one part systems but lack the speed of cure of an acid aziridine reaction. Materials that incorporate both types of functionalities could provide for the desired properties of both systems. Table 7 describes polymers of the same backbone composition with varying amount of self condensing alkoxysilane monomer and architecture.

Table 7 51 EHA 45 BA 4 AA

Type RAFT/Architectured Commercial Control # of MMtMS 1 0 Mn 80,060 61,531 Mw 127,540 380,961 PDI 1.6 6.2 Solids 69.0 50.0 Solution Viscosity 16,000cps 5,000cps

-100.0 -50.0 0 50.0 100.0 150.0 200.0temperature (°C)

10000

1.000E5

1.000E6

1.000E7

1.000E8

1.000E9

1.000E10

G' (d

yne/cm

^2)

RAFT ArchitecturedCommercial Control

Figure 7. Storage modulus as a function of temperature for a RAFT Architectured and

Commercial Control version with 51 EHA/ 45BA/ 4AA backbones

Because these polymers contain acrylic acid as part of the backbone composition and self condensing alkoxysilane monomers in the end regions the opportunity exists to have two independent cross-linking reactions. The polymers described in Table 7 are all formulated with aluminum acetoacetonate (AAA) at

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0.5% on solids andpentanedione as a stabilizer. The AAA serves to rapidly cross-link the acid moieties as well as serving as a Lewis acid catalyst for the alkoxysilane functionalities. Figure 7 is a plot of storage modulus (G’) as a function of temperature. All of the polymers display an identical drop in storage modulus at approximately -35 oC which roughly corresponds to the glass transition temperature. The RAFT/Architectured polymer displays a relatively flat plateau modulus that extends past 150 o C and is overall higher in modulus than the random copolymer commercial control. The random commercial control displays markedly different behavior in that the plateau modulus is not flat and slopes significantly down with increasing temperature. Furthermore at temperatures exceeding 150 oC the decrease in G’ has accelerated such that the material could be characterized as free flowing.

Table 8

Test RAFT/Architectured

Commercial Control


180! Peel to Stainless Steel 15 min Dwell (Lbs/in)

3.5 3.8

180! Peel to Stainless Steel 72 hr Dwell (Lbs/in)

8.4 cohesive 7.5 cohesive

180! Peel to HDPE 72 hr Dwell (Lbs/in)

0.3 .5

180! Peel to Polypropylene 72 hr Dwell (Lbs/in)

2.35 1.20 zipping


>200 90


1200 400

The influence of the bulk rheology is evident in the pressure sensitive adhesive properties of the polymers that are detailed in Table 8. The polymers all exhibit nearly identical peel performance on all substrates. However as the rheology would predict the architectured polymers display an enhancement in cohesive strength and high temperature performance as evidenced by the shear and SAFT results. Conclusions This study has shown that through the use of controlled radical polymerization the placement of reactive functional groups can be achieved to yield novel visco-elastic properties and pressure sensitive adhesive performance. Criticality of the type, position, and number of functional groups was demonstrated with a wide variety of acrylic compositions. It has been demonstrated that high performance pressure sensitive adhesives can be made while maintaining low molecular weight which yields high solids low viscosity solutions or even low melt viscosity 100% solids polymers.

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References 1. Matyjaszewski, K., Ed. ACS Symposium Series, Controlled Radical Polymerization: Progress in

ATRP, NMP and RAFT; American Chemical Society: Washington DC, 2000; Vol. 768. 2. Le, T.P.; Moad, G.; Rizzardo, E.; Thang, S.H. Int. Patent Appl.

WO 9801478, 1998 3. Moad, G.; Solomon, D. H. The Chemistry of Free Radical Polymerization; Elsevier: Amsterdam,

2006. 4. Satas, D. Ed. Handbook of Pressure Sensitive Adhesive Technology 3rd Edition; Satas and

Associates: R.I. 1999.

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TECH 32 Technical Seminar Speaker Acrylic Pressure Sensitive Adhesives Having Controlled Placement of Functional Groups Christopher L. Lester, Ph.D., Avery Dennison

Christopher L. Lester, Ph.D., is a senior research associate at Avery Dennison’s Performance Adhesives Center located in Mill Hall, Pennsylvania. He received his doctorate in polymer science and engineering from the University of Southern Mississippi in 2001. He worked as a senior scientist at the Rohm and Haas Company before joining Avery Dennison in 2004. He can be reached at [email protected].

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