Enhanced viscosity EVM elastomers for GP molded and extruded applications.EVM EVM Earned Value Management EVM Evaluation Module EVM Error Vector Magnitude EVM Electronic Voting Machine EVM Expert Group on Vitamins and Minerals EVM Economic Value Management EVM Extraneous Vegetable Matter EVM Extra-Value Meal EVM Electronic Voltmeter (ethylene-vinyl acetate Polyethylene vinyl acetate (CAS# 24937-78-8, also known as EVA or sometimes simply as "acetate") is the copolymer of ethylene and vinyl acetate. The weight percent vinyl acetate usually varies from 10 to 40% with the remainder being ethylene. copolymer copolymer: see polymer. ) elastomers have traditionally been used in wire and cable industry applications, such as heat resistant insulation and conductive conductive having the quality of readily conducting electric current. conductive flooring flooring or floor covering made specially conductive to electrical current, usually by the inclusion of copper wiring that is earthed easy-peel layers. However, their outstanding resistance to weathering and ozone, excellent heat resistance (175 [degrees] C maximum service temperature), good oil resistance and low compression set at high temperatures should allow them to be used in other applications such as molded mold 1 n. 1. A hollow form or matrix for shaping a fluid or plastic substance. 2. A frame or model around or on which something is formed or shaped. 3. Something that is made in or shaped on a mold. and extruded goods. In addition, EVM based compounds offer processing advantages, including no need for post-cure operations. Unfortunately, their low viscosity results in compounds with poor sag resistance - a problem when trying to extrude extrude /ex·trude/ (ek-strldbomacd´) 1. to force out, or to occupy a position distal to that normally occupied. 2. in dentistry, to occupy a position occlusal to that normally occupied. hose - and with a tendency to blister blister, puffy swelling of the outer skin (epidermis) caused by burn, friction, or irritants like poison ivy. A response of the body to protect deeper tissue, blisters generally contain serum, the liquid component of blood. during molding due to the inability to push air out of the mold mold, name for certain multicellular organisms of the various classes of the kingdom Fungi, characteristically having bodies composed of a cottony mycelium. The colors of molds are caused by the spores, which are borne on the mycelium. . This study evaluates two free radical controlled partial crosslinking (CPC (1) (Central Processing Complex) An IBM mainframe that has two or more central processors (CPs) that share memory. It is the collection of processors, memory and I/O subsystems manufactured with a single serial number, typically all contained in one cabinet. ) approaches for raising the viscosity of the finished compounds to a point where they can be molded successfully. These improvements should open up many new applications which can take advantage of the elastomer's properties. A third method, gamma radiation gamma radiation, high-energy photons emitted as one of the three types of radiation resulting from natural radioactivity. It is the most energetic form of electromagnetic radiation, with a very short wavelength (high frequency). , was studied by Bayer AG Bayer AG German chemical and pharmaceutical company. Founded in 1863 by Friedrich Bayer (1825–1880), it now operates plants in more than 30 countries. Bayer has originated scores of pharmaceuticals, chemicals, and synthetic materials; it was the first developer and . The mechanism is similar to that of E-beam; details are summarized in various internal reports. The influence of various factors on the viscosity enhancement process was evaluated, and an attempt was made to define the mechanism responsible for the increase based on observations and literature. Experimental results indicate that viscosity can be raised successfully by irradiation irradiation /ir·ra·di·a·tion/ (i-ra?de-a´shun) 1. radiotherapy. 2. the dispersion of nervous impulse beyond the normal path of conduction. 3. techniques, such as electron beam A stream of electrons, or electricity, that is directed towards a receiving object. See electron beam imaging and electron beam lithography. , or by chemical means using organic peroxides Organic peroxides are organic compounds containing the peroxide functional group (ROOR'). If the R' is hydrogen, the compound is called an organic hydroperoxide. Peresters have general structure RC(O)OOR. . We believe this viscosity increase equates to an increase in molecular weight. Experimental Raw polymer treatment with peroxide peroxide (pərŏk`sīd), chemical compound containing two oxygen atoms, each of which is bonded to the other and to a radical or some element other than oxygen; e.g. The initial studies involved the use of the Haake Rheocord, System 90, fitted with two wing mixing rotors: * Polymer only - the polymer was added directly to the mixer mixer, either of two electronic devices in which two or more signals are combined. In the type of mixer used in radio receivers, radar receivers, and similar systems, a signal is translated upward or downward in frequency. followed by the peroxide and additives. The rotor rotor: see generator; motor, electric. speed (45 rpm) and temperature (isothermal i·so·ther·mal adj. Of, relating to, or indicating equal or constant temperatures. isothermal, isothermic having the same temperature. ) were fixed for each run. Following the specified time for mixing, the mix was dropped and quickly cooled, and the Mooney determined (tables 1-4 and figures 1-4). [Figures 1-4 ILLUSTRATION OMITTED] Table 1 - initial feasibility study Formulation 32 40% VA EVM 100 Control Peroxide A 1 -- Temperature ([degrees] C) 120 Time (min.) 6 Mooney (MML 1+4 @ 100 [degrees] C) 66 20 Table 2 - DOE with peroxide B Formulation 30 31 32 33 36 40% VA EVM 100 100 100 100 100 Peroxide B 0.3 0.8 1.3 0.8 1.30 Temperature 100 110 100 110 120 Time 6 6 6 6 6 Mooney (MML +4@ 100 [degrees] C) 18(1) 20 19 20 44(2) (1) See figure 1 (2) See figure 2 Table 3 - DOE with peroxide C Formulation 57 58 40% VAEVM 100 100 Peroxide C 0.25 1.25 Temperature ([degrees]) C) 100 100 Time (min.) 6 2 Mooney (MML 1+4@ 100 [degrees] C) 20 36 Formulation 59 60 61 62 40% VAEVM 100 100 100 100 Peroxide C 0.25 1.25 0.75 0.75 Temperature 120 120 110 110 Time 2 6 4 4 Mooney (MML 1+4@ 100 [degrees] C) 23 53 40 45 Table 4 - evaluation of a coagent and peroxide activator Formulation 84 85 40% VAEVM 100 100 Peroxide C 0.75 0.75 TMPTM -- 0.75 Cobalt octoate -- -- Temperature ([degrees] C) 110 110 Time (min.) 4 4 Mooney (MML 1+4@ 100 [degrees] C) 36 37 Formulation 86 87 88 89 40% VAEVM 100 100 100 100 Peroxide C 1.0 0.75 1.0 1.0 TMPTM 0.75 -- -- 1.0 Cobalt octoate -- 0.1 0.1 -- Temperature 110 110 110 110 Time 4 4 4 4 Mooney (MML 1+4@ 100 [degrees] C) 42 54 73 49 Minimum value from coagent; large impact from activator activator /ac·ti·va·tor/ (ak´ti-va?ter) 1. a substance that combines with an enzyme to increase its catalytic activity. 2. a substance that stimulates the development of a specific structure in the embryo. . Polymer treatment recipe 40% and 70% vinyl acetate (VA) EVM 100 Peroxide Variable Cobalt octoate (peroxide activator) Variable TMPTM Variable * Subsequent mixes were conducted in a 1.6L intensive mixer to validate To prove something to be sound or logical. Also to certify conformance to a standard. Contrast with "verify," which means to prove something to be correct. For example, data entry validity checking determines whether the data make sense (numbers fall within a range, numeric data the results from the Rheocord and to determine the shear shear: see strength of materials. Shear A straining action wherein applied forces produce a sliding or skewing type of deformation. stability of the resultant This article is about the resultant of polynomials. For the result of adding two or more vectors, see Parallelogram rule. For the technique in organ building, see Resultant (organ). In mathematics, the resultant of two monic polynomials polymer. The following conditions were employed:
Fill factor 73%
Rotor rpm 40-77 rpm
Temperature 30 [degrees] C start
Ram pressure 0.2 MPa
0 min. Add polymer to the mixer and mix for 30
sec.
0.5 min. Add peroxide and coagent and mix.
3 min. Brush down
Dump after 6 min. mix time and cool on mill (an antioxidant antioxidant, substance that prevents or slows the breakdown of another substance by oxygen. Synthetic and natural antioxidants are used to slow the deterioration of gasoline and rubber, and such antioxidants as vitamin C (ascorbic acid), butylated hydroxytoluene shear stabilizer stabilizer: see airplane. and a peroxide activator were added to selected mixes).
Polymer treatment recipe
40% VA EVM 100
Peroxide Variable
Cotsalt octoate Variable
TMPTM Variable
Stabilizer A (antioxidant
shear stabilizer) Variable
Viscosity measurements were determined on a Mooney viscometer viscometer Instrument for measuring the viscosity (resistance to internal flow) of a fluid. In one type, the time taken for a given volume of fluid to flow through an opening is recorded. , MML MML - Human-Machine Language. A language from ITU-T for telecommunications applications. It has a complex natural-language syntax. [CCITT Recommendations Z.311-Z.318, Z-341, Nov 1984]. 1 +4 @ 100 [degrees] C using ASTM ASTM abbr. American Society for Testing and Materials D 1646. Peroxide treatment of the compound master batch The polymer was massed and cut into strips prior to introduction to the Haake System 90 mixer. The order of addition was the polymer followed by the balance of the ingredients. The mixer speed was fixed (45 rpm) and the temperature programmed from a selected starting point Noun 1. starting point - earliest limiting point terminus a quo commencement, get-go, offset, outset, showtime, starting time, beginning, start, kickoff, first - the time at which something is supposed to begin; "they got an early start"; "she knew from the to the desired final temperature in about three minutes "Three Minutes" is the 46th episode of Lost. It is the twenty-second episode of the second season. The episode was directed by Stephen Williams, and written by Edward Kitsis and Adam Horowitz. It first aired on May 17, 2006 on ABC. . The mix was dumped when the final mix time was reached. The time temperature relationship was varied in order to define practical mixing parameters (tables 6-9).
Table 6 - evaluation of peroxide C in black masterbatch
Formulation 107 108 109 110
40% VAEVM 100 100 100 100
Peroxide Aide 1 2 2 2 2
Low MW P.E. 2 2 2 2
Stearic acid 1 1 1 1
FEF (N550 black) 50 50 50 50
Cobalt octoate 0.1 0.2 0.2 1
Peroxide C 1.0 1.0 2.0 2.0
Temperature ([degrees]C) 130 130 130 130
Programmed from 100 [degrees] to
130 [degrees] over 3 min.,
then held at130 [degrees] C
Time (min 6 6 6 6
Mooney (MML 1+4@100 [degrees]C) 45 46 46 47
No peroxide acitivity evident.
Formulation 111 112
Control
40% VAEVM 100 100
Peroxide Aide 1 2 2
Low MW P.E. 2 2
Stearic acid 1 1
FEF (N550 black) 50 50
Cobalt octoate 0.1 0
Peroxide C 1.5 0
Temperature 130 130
Programmed from 100 [degrees] to
130 [degrees] over 3 min.,
then held at130 [degrees] C
Time (min 6 6
Mooney (MML 1+4@100 [degrees] C 46 48
No peroxide acitivity evident.
Table 7 - determination of peroxide in black
masterbatch
Formulation 145 146 147 148 149
Control
40% VAEVM 100 100 100 100 100
Peroxide aide 1 2 2 2 2 2
Low MW P.E. 2 2 2 2 2
Stearic acid 1 1 1 1 1
FEF (N550 black) 50 50 50 50 50
Peroxide C 3
Peroxide B 3
Peroxide A 3
Peroxide F 3
Temperature ([degrees] C) 150 150 150 150 150
Programmed from 100 [degrees]C to final temp.
over first 3 min., then held at 150 [degrees] C
Time (min.) 7 7 7 7 7
Mooney(MML 1+4@100 [degrees] 47 78 73 63 49
Table 8 - DOE with peroxide B to establish time/temp. conditions
for black masterbatch
Formulation 169 170 171 172
40% VAEVM 100 100 100 100
Peroxide aide 1 2 2 2 2
Low MW P.E. 2 2 2 2
Stearic acid 1 1 1 1
FEF(N550black) 50 50 50 50
Peroxide B 1 3 2 2
Temperature ([degrees]C) 140 140 125 125
Programmed from 100 [degrees]C to final temp.
over first 3 min., then held at final temperature
Time (min.) 7 7 7 7
Mooney (MML 1+4@100 [degrees]C) 61 86 70 71
Formulation 173 174
40% VAEVM 100 100
Peroxide aide 1 2 2
Low MW P.E. 2 2
Stearic acid 1 1
FEF(N550black) 50 50
Peroxide B 1 3
Temperature ([degrees]C) 110 110
Programmed from 100 [degrees]C to final temp.
over first 3 min., then held at final temperature
Time (min.) 7 7
Mooney (MML1+4@100 [degrees]C) 51 66
Table 9 - evaluation of peroxide C in white
masterbach
Formulation 113 114 115
40% VAEVM 100 100 100
Peroxide aide 1 2 2 2
Clay 1 50 50 50
Clay 2 -- -- --
Low MW P.E. 2 2 2
Stearic acid 1 1 1
PeroxideC 1.0 1.0 2.0
Cobaltoctoate 0.1 0.1 0.1
TMPTM -- 1.0 --
Temperature ([degrees]C) 130 130 130
Programmed from 100 [degrees] C
to final temp. over first 3 min.,
then held at 130 [degrees]C
Time (min.) 6 6 6
Mooney(MML 1+4@100 [degrees]C) 45 52 57
Control @ 27MU
Formulation 116 117 118
40% VAEVM 100 100 100
Peroxide aide 1 2 2 2
Clay 1 -- -- --
Clay 2 50 50 50
Low MW P.E. 2 2 2
Stearic acid 1 1 1
PeroxideC 1.0 1.0 2.0
Cobaltoctoate 0.1 0.1 0.1
TMPTM 1.0 -- --
Temperature ([degrees]C) 130 130 130
Programmed from 100 [degrees] C
to final temp. over first 3 min.,
then held at 130 [degrees]C
Time (min.) 6 6 6
Mooney(MML 1+4@100 [degrees]C) 42 40 57
Control @ 22MU
White formulation Black formulation
40% VA EVM 100 40% VA EVM 100
Process aid 2 Process aid 2
Clays 50 FEF (N550) black 50
Stearic acid 1 PE AC-617 2
Cobalt octoate 0.1 Stearic acid 1
Peroxide(*) Variable Peroxide(*) Variable
TMPTM 0.5 TMPTM 0.5
Cobalt octoate Variable
(*) Peroxides types are defined in tables 6-9. Viscosity measurements were determined on a Mooney viscometer, MML 1+4 @ 100 [degrees] C. E-beam treatment of raw polymer Laboratory quantities of polymers for this study were Ebeam treated by a toll converter (1) A device that changes one set of codes, modes, sequences or frequencies to a different set. See A/D converter. (2) A device that changes current from 60Hz to 50Hz and vice versa. (ref. 1). The electron beam equipment is comprised of a high voltage The term high voltage characterizes electrical circuits, in which the voltage used is the cause of particular safety concerns and insulation requirements. High voltage is used in electrical power distribution, in cathode ray tubes, to generate X-rays and particle beams, to power supply, an accelerator to accelerate the electrons to their full energy potential and a scanning system to insure uniform distribution of the electrons over the polymer surface. The level of irradiation is based on sample thickness and exposure time at a specific power setting. In this study, due to voltage capacity limitations of the unit, multiple passes were required to obtain a high dosimetry dosimetry /do·sim·e·try/ (do-sim´e-tre) scientific determination of amount, rate, and distribution of radiation emitted from a source of ionizing radiation, in biological d. . The electron beam irradiation experiments in this study were conducted using EVM polymers with 40% and 70% vinyl acetate Vinyl acetate, also known as VAM for vinyl acetate monomer, has the chemical formula CH3COOCH=CH2 and is a colorless liquid with a sweet flavor. Systematic names include 1-acetoxyethylene and acetic acid ethenyl ester. content. These polymers were irradiated at dosage dosage /dos·age/ (do´saj) the determination and regulation of the size, frequency, and number of doses. dos·age n. 1. Administration of a therapeutic agent in prescribed amounts. levels from 2.5 kGy to 35 kGy which resulted in polymers with Mooney viscosity levels ranging between 28 and 100. The relationship between radiation level and polymer viscosity is illustrated in figures 5-6. [Figure 5-6 ILLUSTRATION OMITTED] Peroxide treated polymer shear stability studies An experiment was conducted using a 40% VA EVM polymer and benzoyl peroxide benzoyl peroxide n. A flammable white granular solid used as a bleaching agent for flour, fats, waxes, and oils, and in pharmaceuticals. benzoyl peroxide, n 1. to increase the polymer viscosity in the 1.6L intensive mixer. The antioxidants Antioxidants Substances that reduce the damage of the highly reactive free radicals that are the byproducts of the cells. Mentioned in: Aging, Nutritional Supplements antioxidants, n. tris-(nonylphenyl) phosphate phosphate, salt or ester of phosphoric acid, H3PO4. Because phosphoric acid is tribasic (having three replaceable hydrogen atoms), it forms monophosphate, diphosphate, and triphosphate salts in which one, two, or three of the hydrogens of the (TNPP TNPP Telocator Network Paging Protocol (PCIA) ) and Stabilizer A were used to stabilize stabilize See peg. the polymer. The EVM was added to the intensive mixer and mixed for 30 seconds. After 30 seconds the peroxide and the coagent were added. These materials were mixed for six-minutes. At six minutes the antioxidants were added and mixed for an additional 30 seconds and then the batch was discharged and cooled. The formula for the 1.6 L intemal mixer was as follows:
40% VA EVM 100.00
Luperco ACP 0.75
TMPTM 0.50
Antioxidants Variable (details are summarized in
the discussion section).
The enhanced viscosity polymer stability test was conducted in the Haake Rheocord Mixer (System 90) according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. ASTM D 3182: Polymer weight 45 grams Test temperature 140 [degrees] and 160 [degrees] C Mixer rpm 50 Test duration 25 min. Stability indicator Rate of torque decay Compounding and molding studies Utilizing the correlation curve developed for electron beam radiation, appropriate treatment levels were chosen to give polymers with Mooney viscosities of 40 and 60 for the 40% VA EVM polymer. Twenty pounds of polymer at each viscosity were produced by the E-beam toller (ref. 1) and compounded into both black-filled and clay/silica-filled automotive injection molding injection molding n. A manufacturing process for forming objects, as of plastic or metal, by heating the molding material to a fluid state and injecting it into a mold. compounds, see tables 10 and 11. Table 10 - black formulation Ingredients PHR EVM 40% VA 100 Zn [(F/A).sub.2] High MW 2 N990 carbon black 40 TCP plasticizer 15 Zinc borate 5 Low MW polyethylene 2 Polycarbodiimide 3 Stearic acid 1 Peroxide F 5 TAIC 3 Table 11 - white formulation Ingredients PHR EVM 4O% VA 100 Calcium stearate 3 Carnauba wax 2 MgO 2 Precipitated silica 30 Talc 25 Ca(F/A) soap 1.5 Vinyl silane 1.6 DOS 8 Paraffinic oil 8 Hard clay 25 TAC 1.2 Peroxide E 5 For the molding verification study, preliminary work was done to establish the peroxide level necessary to produce a 60 Mooney viscosity polymer. A similar study was done to determine the peroxide level necessary to produce, in-situ, a compound masterbatch with viscosity similar to the masterbatches made from the 60 Mooney viscosity electron beam radiated ra·di·ate v. ra·di·at·ed, ra·di·at·ing, ra·di·ates v.intr. 1. To send out rays or waves. 2. To issue or emerge in rays or waves: Heat radiated from the stove. and peroxide treated polymers. Curatives were added on the mill to each of these masterbatch compounds for subsequent molding observations. During the mixing of these compounds, processing was evaluated to determine whether the method of viscosity enhancement had an effect on this characteristic, tables 12 and 13.
Table 12 - molding studies - white compound
Comp no. FC108 FC109 FC110 FC111/212
Treatment None E-beam E-beam ROOR MB
ML 1+4@ 100
[degrees]C
Polymer 20 60 40 20
Compound 11 25 19 10(3)
Rating (1) 5 2.5(2) 3 4.50
1. 1 = No blisters to 5 = severely blistered molded parts.
2. Some mold flow marks due to high viscosity polymer.
3. Peroxide inactivated by carbon black
Comp no. FC220 FC221 FC222 FC223 FC224
Treatment None ROOR ROOR ROOR ROOR
polymer polymer polymer polymer
ML 1+4@ 100
[degrees]C
Polymer 20 72 40 66 56
Compound 11 33 20 30 25
Rating (1) 5 1(2) 1.50 1(2) 1(2)
1. 1 = No blisters to 5 = severely blistered molded parts. 2. Some mold flow marks due to high viscosity polymer.
Table 13 - molding studies - white compound
([dagger])
Comp no. FC202 FC203 FC204
Treatment None E-beam E-beam
ML 1+4@ 100
[degrees]C
Polymer 20 60 40
Compound 17 40 26
Rating (1) 1.50 1 1
1.1 = No blisters to 5 = severely blistered molded parts
Comp no. FC202 FC205 FC206 FC207
Treatment None Roor Roor Roor
2.0/0.1/0(2) 4.0/0.1/0(2) (4.0/0.1/.05(2)
ML 1+4@ 100
[degrees]C
Polymer 20 20 20 20
Compound 17 22 33 38
Rating (1) 1.50 1 1 1
1.1 = No blisters to 5 = severely blistered molded parts. 2. PHR PHR Personal Health Record PHR Physicians for Human Rights PHR Professional in Human Resources PHR Public Health Reports PHR Partnerships for Health Reform Phr Phrygian (linguistics) PHR Presse Hebdomadaire Régionale ratio of peroxide/activator/stabilizer in masterbatch. Discussion The objective of this study was to develop a practical method to increase the viscosity of compounds based on EVM polymers in order to resolve processing problems and the blistering blis·ter·ing n. See vesiculation. usually encountered during molding. Based on previous work and on a search of literature databases (ref. 2), three methods were identified which looked promising toward meeting this objective - gamma radiation, electron beam radiation and the use of organic peroxides. Gamma radiation Treating EVM with gamma radiation is summarized in various internal reports from Bayer AG. Although known to be effective toward enhancing the polymer viscosity, no efforts were undertaken in this study to evaluate the gamma radiation process. Electron beam Electron beam irradiation of polymers can cause controlled partial crosslinking (CPC) and chain scission scis·sion n. 1. A separation, division, or splitting, as in fission. 2. See cleavage. to occur simultaneously (ref. 2). Radiation dosage and the type of polymer used determine which of these two competing reactions is dominant. For EVM, it appears that the CPC reaction (figure 7) is dominant, and is initiated by abstraction In object technology, determining the essential characteristics of an object. Abstraction is one of the basic principles of object-oriented design, which allows for creating user-defined data types, known as objects. See object-oriented programming and encapsulation. 1. of an [Alpha]-hydrogen on the backbone of the polymer. The reactivity re·ac·tiv·i·ty n. 1. The property of reacting. 2. The process of reacting. reactivity, n the degree to which a being responds to a stimulus. of the polymer is dependent upon its vinyl acetate content - higher VA levels increase the concentration of the [Alpha]-hydrogen atoms, making these polymers more reactive reactive /re·ac·tive/ (re-ak´tiv) characterized by reaction; readily responsive to a stimulus. re·ac·tive adj. 1. Tending to be responsive or to react to a stimulus. 2. under electron beam irradiation. This was supported by the experimental results illustrated by Mooney viscosity measurements and by molecular weight and gel determinations as shown in internal work by H. Meisenheimer dated 8/19/1996. NMR NMR: see magnetic resonance. measurements were not successful in indicating a path or mechanism for the branching process In probability theory, a branching process is a Markov process that models a population in which each individual in generation n produces some random number of individuals in generation n ; higher resolution NMR would have been needed to delineate. [Figure 7 ILLUSTRATION OMITTED] Statistical analysis of experimental results indicates a very high first order correlation between electron beam dosage and the increase in polymer viscosity. The correlation coefficient Correlation Coefficient A measure that determines the degree to which two variable's movements are associated. The correlation coefficient is calculated as: for the 40% vinyl acetate polymer treatment was 0.9641 and 0.9869 for the 70% vinyl acetate polymer treatment as shown in figures 5 and 6. This high degree of correlation allowed very accurate prediction of the dosage requirement necessary to obtain specific Mooney viscosity level polymers for subsequent compounding studies. Furthermore, the high correlation levels confirm that CPC is the dominant reaction and that chain scission is of minimal consequence in this situation. The experimental results from this study confirmed the hypothesis that the efficacy of the electron beam process increases with increasing vinyl acetate level in the polymer, as seen in figure 8. [Figure 8 ILLUSTRATION OMITTED] Peroxide Similar to treatment with electron beam radiation, the use of organic peroxides promotes CPC via creation of a free radical by extraction of the [Alpha]-hydrogen atoms on the polymer backbone. Combination of these free radicals causes an increase in molecular weight resulting in higher viscosity. The plot of Mooney viscosity against peroxide addition level (figures 3 and 4) shows a first order correlation similar to that seen with electron beam radiation. This suggests that the two mechanisms are the same. Since the objective of this study was to find a practical means to enhance the viscosity of the EVM polymers, a range of peroxides was evaluated. The very low viscosity of the polymers limited the selection of peroxides to those with activation activation /ac·ti·va·tion/ (ak?ti-va´shun) 1. the act or process of rendering active. 2. the transformation of a proenzyme into an active enzyme by the action of a kinase or another enzyme. 3. temperatures at or below 100 [degrees] C, which is an easily attainable temperature during the intensive mixer cycle. Most peroxides commonly used in the rubber industry have activation temperatures above 120 [degrees] C, and were therefore deemed unsuitable for use. Dichloro-benzoyl peroxide (Kadox TDP TDP (thymidine diphosphate): see thymine. ) was identified as the most practical choice. However, this peroxide, as a result, of its low activation temperature, required shipment and storage under refrigerated re·frig·er·ate tr.v. re·frig·er·at·ed, re·frig·er·at·ing, re·frig·er·ates 1. To cool or chill (a substance). 2. To preserve (food) by chilling. conditions. Additionally, the efficiency of this peroxide was not as high as the others evaluated, and the use of an activator (cobalt Cobalt, town, Canada Cobalt (kō`bôlt), town (1991 pop. 1,470), E Ont., Canada, NE of Sudbury, near Lake Timiskaming. Once a center for cobalt and silver mining, the area is now economically depressed. octoate) was necessary to obtain satisfactory viscosity enhancement at low peroxide usage levels. In addition to the studies evaluating peroxide enhancement of raw polymer viscosity, work was done to determine whether the increase could be created in-situ in the compounded masterbatch. Experimental data showed that the dichloro-benzoyl peroxide (as well as benzoyl peroxide), while promoting viscosity enhancement in mineral-filled compounds, was not effective in raising the viscosity in black-filled compounds. Similar work utilizing more commonly used peroxides did not show this phenomenon (table 7). The scope of this study did not permit the determination of its cause; additional work must be done to identify the interfering factors. Polymer stability experiments During the preparation of 40% VA EVM with increased viscosity using the peroxide method it was discovered that the Mooney viscosity dropped from 55 to 39 during subsequent processing under high shear conditions. This 16 unit decrease was thought to be the result of residual peroxide inhibiting in·hib·it tr.v. in·hib·it·ed, in·hib·it·ing, in·hib·its 1. To hold back; restrain. See Synonyms at restrain. 2. To prohibit; forbid. 3. recombination recombination, process of "shuffling" of genes by which new combinations can be generated. In recombination through sexual reproduction, the offspring's complete set of genes differs from that of either parent, being rather a combination of genes from both parents. which results from thermal-mechanical induced chain scission. It was further speculated that the addition of an antioxidant would scavenge scav·enge v. scav·enged, scav·eng·ing, scav·eng·es v.tr. 1. To search through for salvageable material: scavenged the garbage cans for food scraps. 2. the residual peroxide radicals and allow recombination to occur. Table 14 shows the antioxidant combinations and amounts, along with the resulting Mooney viscosity values. Table, 15 shows the Haake stability data (torque in mg) for the polymers treated with the antioxidant combinations shown in table 14. (1 Newton-meter = 101.97 meter-grams). Table 14 - polymer stability experiments Experimental 072 073 074 075 076 077 Number TNPP 0.05 0.08 0.03 0.05 0.00 0.00 Stabilizer A 0.0 0.0 0.0 0.1 0.1 0.1 ML/4@ 100 [degrees] C 32.9 43.2 46.7 45.2 47.3 46.4 Table 15 Haake stability at 140 [degrees] C Minutes 072 073 074 2.5 1,125 1,350 1,454 12.5 900 1,073 1,108 25.0 796 900 952 Haake stability at 160 [degrees] C Minutes 072 073 074 2.5 1,073 1,142 1,142 12.5 588 727 744 25.0 554 658 623 Haake stability at 140 [degrees] C Minutes 075 076 077 2.5 1,350 1,350 1,488 12.5 1,038 1,108 1,246 25.0 935 969 1,142 Haake stability at 160 [degrees] C Minutes 075 076 077 2.5 1,194 1,142 1,177 12.5 831 900 900 25.0 727 762 813 Based on these stability measurements and Mooney viscosity, it appears that Stabilizer A would be the preferred antioxidant. Figure 9 is a Haake Rheocord graph which shows enhanced viscosity EVM with and without antioxidant. One can see from this graph that the decay slope for the polymer with antioxidant is much less than that from the polymer which does not contain an antioxidant. [Figure 9 ILLUSTRATION OMITTED] We can conclude from this data that it is necessary to add an antioxidant to EVM that is treated with peroxide. We did not see this phenomenon with electron beam irradiated EVM which gives further evidence that it is the residual peroxide which causes the Mooney reduction under subsequent high shear processes. Compounding and molding verification studies Only subjective measurements were performed on the compounds molded as macro-slabs and compression set buttons. The imperfections, or lack of, were taken as a measure of the processability improvement attributed to the enhanced viscosity as shown in tables 12 and 13. Results and discussion E-beam treated Levapren Electron beam treatment of EVM successfully increases the Mooney viscosity to controlled values. Typical dosage levels from 2.5 to 35 kGy increased the Mooney viscosity from 28 and 100 Mooney units. Statistical analysis shows a high first order relationship between electron beam dosage and Mooney viscosity. Results also confirm that the efficiency of electron beam dosage improves with increased vinyl acetate content of the EVM materials. Peroxide treated Levapren Peroxides were also shown to be effective at raising the Mooney viscosity of EVM materials. Benzoyl peroxide, when used in conjunction with cobalt octoate, was shown to have the lowest activation temperature (below 100 [degrees] C) and shows a good first order correlation to the E-beam treatment. Mooney enhancement of the polymer alone or in situ In place. When something is "in situ," it is in its original location. in the white compound masterbatch was possible with benzoyl peroxide. The benzoyl benzoyl /ben·zo·yl/ (ben´zo-il) the acyl radical formed from benzoic acid, C6H5CO—. benzoyl peroxide a topical keratolytic and antibacterial used in the treatment of acne vulgaris. type peroxides were inactive in·ac·tive adj. 1. Not active or tending to be active. 2. a. Not functioning or operating; out of use: inactive machinery. b. in the presence of carbon black. Therefore, there was no viscosity enhancement with the masterbatch treated black compound. Peroxide treated EVM polymers showed a viscosity decrease with time due to chain scission from the residual peroxide remaining in the compound. Addition of shear stabilizers (radical scavengers) at low levels successfully stabilized sta·bi·lize v. sta·bi·lized, sta·bi·liz·ing, sta·bi·liz·es v.tr. 1. To make stable or steadfast. 2. the viscosity. E-beam treated EVM did not show this lowering of viscosity phenomenon with subsequent processing involving high shear. Molding trial conclusions The subjective visual ratings from the molding study, indicated an improvement in molding using enhanced viscosity EVM. Molding defects, i.e., blisters were reduced as polymer and compound viscosity increased. * The peroxide treated polymer showed advantages in molding behavior relative to the E-beam treated polymer in the black compound. * The white compound molded better overall than the black compound. This would suggest that compound characteristics contribute to moldability and should be considered along with the use of the enhanced viscosity EVM. * The addition of 0.05 phr of the Stabilizer A improved the compound viscosity of the peroxide treated white compound by 15% (increased viscosity). This further suggests that peroxide treated EVM needs stabilization Stabilization The action undertakes a country when it buys and sells its own currency to protect its exchange value. Actions registered competitive traders undertake by on the NYSE to meet the exchange requirement that 75% of their traded be stabilizing, meaning that sell orders . Table 5 - initial evaluation of peroxide D Formulation 84 85 86 40% VA EVM 100 100 100 Peroxided 1.0 2.0 3.0 Cobalt octoate -- -- -- Temperature ([degrees]C) 100 100 100 Time (min.) 10 10 10 Mooney (MML 1+4@100 [degrees]C) 26 34 34 Formulation 87 88 89 40% VAEVM 100 100 100 Peroxided 1.0 2.0 3.0 Cobalt octoate 0.05 0.05 0.05 Temperature ([degrees]C) 100 100 100 Time (min.) 10 10 10 Mooney (MML 1+4@100 [degrees]C) 30 35 47 References (1.) Treatment of the polymers in this study was done by Radiation Dynamics, Inc. (Edgewood, NY). (2.) Electron Beam Initiated Grafting grafting, horticultural practice of uniting parts of two plants so that they grow as one. The scion, or cion, the part grafted onto the stock or rooted part, may be a single bud, as in budding, or a cutting that has several buds. and Crosslinking of Ethylene ethylene (ĕth`əlēn') or ethene (ĕth`ēn), H2C=CH2, a gaseous unsaturated hydrocarbon. It is the simplest alkene. Vinyl Acetate Copolymer. Part I: Structural Characterization A rather long and fancy word for analyzing a system or process and measuring its "characteristics." For example, a Web characterization would yield the number of current sites on the Web, types of sites, annual growth, etc. , Sujit Datta, Tapan Chaki and Anil Bhowmick, Rubber Technology Center, Indian Institute The Indian Institute in central Oxford, England is located at the north end of Catte Street on the corner with Holywell Street and faching down Broad Street from the east.[1] of Technology.3 |
|
||||||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion