Patent Application: US-73973396-A

Abstract:
dimensionally stable polyester fibers , webs and fabrics , comprising a nucleating agent incorporated into the fibers are disclosed . methods of incorporating the nucleating agent within the polyester are disclosed .

Description:
a solid state polymerized pet of intrinsic viscosity 0 . 9 was used for this study . the additives compounded with the polymer include an organic salt , an inorganic compound , a thermotropic liquid crystalline polyester and an ionomer . the chemical structure , trade name and source are given in table 1 . the additives were tested for their nucleating ability by injection molding with pet and characterizing the molded samples . the process conditions shown in table 2 were kept constant for all samples to make an absolute comparison . a total of 12 samples were produced as shown in table 7 , below . prior to the runs , pet and lcp were dried at 120 ° c . and the ionomer at 60 ° c . for 12 hours . at first , pet was injection molded without any additives . in the successive runs , pet was dry blended with different additives in appropriate weight percentages . in between the runs , neat pet was used to purge the materials in the screw to avoid any contamination . the injection molded samples were sealed air - tight for further characterization . the successful nucleation additives , sodium benzoate and lcp were compounded with pet pellets in a twin screw extruder . the conditions of extrusion were kept the same for all samples as shown in table 3 . a co - rotating twin screw type extruder was used to thoroughly melt mix pet with the nucleating additives . initial runs of pet dry blended with additives in the hopper of a six - inch melt blowing equipment yielded poor quality webs . this is the reason for thoroughly mixing the solid additives with pet in a twin screw extruder . the compounded materials were quenched in a water bath prior to pelletizing . the pelletized samples were tightly sealed to prevent moisture uptake . the compounded pet samples were melt blown into fine quality webs using a six - inch wide die . the process conditions as shown in table 4 were kept constant for different samples produced to make an absolute comparison between samples . prior to processing , the compounded pet pellets were dried at 120 ° c . for 12 hours . unlike our previous experience on injection molding machine and the twin screw extruder , processing problems like flies and change in web density were encountered on switching from pet to pet with additives . utmost care was taken to produce uniform and good quality webs . it was very difficult to control the web thickness and basis weight of the webs produced . this could be attributed to the poor draw down of the lcp component in the blends . when lcp was tried alone without any additives , poor quality mat with very large but strong fibers were obtained . in order to investigate the effect of process variables such as throughput rate , air pressure at the die , die temperature , air temperature and the die - to - collector distance on the properties of the melt blown webs , pet melt blown webs without any additives were prepared varying the above mentioned factors at two levels . the details of the melt blowing run are shown in table 5 . due to the complexity of the process like the interaction between the air temperature , air velocity and throughput rate , production of controlled samples was difficult . however , efforts were made to produce control webs of almost same thickness and density . a dsc 25 with mettler ta 4000 controller was used to characterize the injection molded specimens of almost same thickness and a sample mass of approximately 15 mg . an inert environment was maintained throughout the scan to avoid thermal degradation . both non - isothermal and isothermal kinetics were performed using the dsc . for non - isothermal studies , the samples were scanned at a rate of 20 ° c ./ min . pet samples were held at 300 ° c . in the dsc cell for 3 minutes for complete melting of crystals . cooling rates of 20 °, 40 °, 60 ° c ./ min . were used . isothermal studies were done by measuring the time taken for 50 % crystallinity to develop at 232 ° c . a cooling rate of 20 ° c ./ min . from the melt kept at 300 ° c . for 3 minutes was used to reach the desired isothermal temperature . a dsc 25 with mettler 4000 control system was used for the thermal characterization of as - produced melt blown webs without any additives . a nitrogen atmosphere was used throughout the study . a sample mass of 10 mg was used . samples were heated at a rate of 20 ° c ./ min . from 50 ° to 300 ° c . a dsc 20 was used for analyzing the melt blown samples with additives . the same conditions of testing was followed . the percent crystallinity from the heating and cooling dsc curves was calculated according to the formula where x c is the percent crystallinity ; δh ex is the experimental heat of fusion determined from the dsc curves ; δh th is the theoretical heat of fusion determined from athas tables 78 ! and b is the weight percent of the additive . where δh m is the heat of fusion of the melting endotherm in j / g and δh c is the heat of fusion of the crystallization exotherm in j / g . where h c is the enthalpy in j / g for a 100 % crystalline solid and h a is the enthalpy in j / g for a 100 % mobile amorphous liquid . the thermal shrinkage of melt blown pet webs was determined in the machine direction according to the formula samples were annealed without tension at 110 °, 150 ° and 190 ° c . for 3 minutes in a vacuum oven . in the case of melt blown pet with additives , because of the difference in thickness of the webs , the samples were kept in the oven for the duration corresponding to the thickness of the samples as shown in table 6 . the mean thickness of 5 samples was determined . the samples annealed at different temperatures were tightly sealed for further analysis . the shrunk samples were characterized using dsc to study the amount of different entities present in the fibers . the non - isothermal cooling behavior of pet from the melt is shown in fig3 . the polymer was cooled from 300 ° c . to 50 ° c . at a rate of 20 ° c ./ minute . as we know , ordering of polymer molecules results in a release of heat and thus the polymer crystallization is an exothermic process . as shown in the figure , two mechanisms become operative : the left hand portion of the curve is dominated by the nucleation mechanisms and the right hand portion of the curve by the growth and diffusion mechanisms ( viscosity dependent ). the effect of a nucleating additive is to shift the t cc , the temperature of maximum crystallization on cooling , to higher temperatures . the t cc values for injection molded pet samples with different additives are shown in table 7 . the samples were cooled at 20 °, 40 ° and 60 ° c ./ minute from 300 ° c . to 50 ° c . after being held at 300 ° c . for 3 minutes . there was a shift of about 16 . 5 ° c . for pet mixed with 2 % sodium benzoate . the trend is the same for increased cooling rates . thus , it is evident that sodium benzoate acts as an efficient nucleating agent in commercial pet processing where the cooling rate is of the order of several hundred degrees per minute . lcp , ionomer and copper sulfate pentahydrate alone did not show any significant nucleating ability . but , when lcp was combined with sodium benzoate , a synergism in nucleation was seen with a temperature shift of 15 . 5 ° c . at a cooling rate of 20 ° c ./ minute . lcp alone crystallized at a temperature much higher than that of pure pet . however , the heat of fusion value was negligible when compared to that of pet . fig4 illustrates the typical heating curve ( 20 ° c ./ minute ) for an injection molded amorphous pet sample . it consists of a t g at 80 ° c ., a crystallization exotherm at 129 ° c . and a broad melting endotherm with a melting point at 257 ° c . the effect of nucleating additive is to decrease t ch and increase t m . as can be seen from table 8 , a decrease of about 11 . 8 ° c . was observed for pet sample injection molded with 2 % sodium benzoate . the melting point increased by about 4 . 2 ° c . the synergistic effect of adding sodium benzoate with pet / lcp blends is also seen by the reduction of about 9 . 6 ° c . in t ch and an increase of 3 . 4 ° c . in t m . lcp , ionomer and copper sulfate pentahydrate alone did not haisotro visible influence on t ch or t m . lcp had an isotropization temperature ( t i ) of 276 ° c . where the crystal to nematic transition took place . table 8 also contains the percent crystallinity values from heating and cooling curves . a frequent mistake made in calculating the percent crystallinity is the assumption that δh th is constant over a wide range of temperatures . but , according to the athas table of thermal properties 80 !, δh th is in fact a function of temperature . fig5 illustrates the change in enthalpy of solid , a 100 % crystalline material and that of a liquid , a 100 % amorphous material with temperature . the liquid heat capacity is always higher than that of the solid because of the unrestricted motion of the molecular segments . the theoretical heat of fusion has a cubic function with temperature as shown in fig6 . since the difference between the transition points ( t m , t ch and t cc ) is only of the order of a few degrees , a linear function was assumed between consecutive points in calculating the percent crystallinity . a lower value of δh th was obtained at t ch . assuming a constant value for δh th would result in an error of over 20 %. this correction procedure was used for every temperature while calculating the percent crystallinity values . the contribution of additives in the calculation was eliminated by subtracting the weight percent of additives from the theoretical heat of fusion . this way , the crystallinity values obtained were that of the pet component only . as shown in table 8 , no crystallinity was detected for pure pet injection molded specimens , suggesting that the samples were essentially amorphous . the pet sample with 2 % sodium benzoate had the higher percent crystallinity values . no crystallinity was detected for samples with low weight percent lcp . samples with the copper sulfate additives were brittle indicative of crystalline fraction although it was much smaller than that containing sodium benzoate . all the samples with more than two components showed synergistic effect . the additives were chosen for compounding with pet based on their nucleation efficiency . thus it could be seen that sodium benzoate is the most successful additive followed by lcp , copper sulfate and the ionomer . the percent crystallinity values for different samples on cooling from the melt at 20 ° c ./ minute are almost the same indicative of the fact that although the nucleation rate increases in the case of additives , the growth rate remains the same . the non - isothermal and isothermal kinetics determined from dsc are shown in fig7 and 8 respectively . the sigmoidal shape of the curves is typical of polymer crystallization . the relative crystallinity values were calculated by partitioning the area under the crystallization peak on cooling from the melt , in this case , cooled at a rate of 20 ° c ./ minute , into small areas and dividing each area by the total area of the peak . it can be seen from the figure that pet with sodium benzoate had considerably higher percent crystallinity values by the time the other samples started to crystallize . this indicates the increase in overall crystallization rate of pet with sodium benzoate , and pet with lcp and sodium benzoate . all other additives fall in the same area as that of pure pet . isothermal kinetics were performed at 232 ° c . the exotherm was allowed to reach the base line before useful calculations were made . as can be seen from fig8 crystallization rate of pet with successful additives was much higher than that of the unsuccessful additives . the potential nucleating additives and their combinations were thus obtained from these experimental investigations using the kinetic studies . it was tactfully assumed that the higher crystallization rate of pet samples with additives would prevent the shrinkage of pet during further thermal treatment . table 9 and fig9 show the dsc results of different melt blown webs produced under identical processing conditions with nucleating additives . almost all the additives showed nucleating ability as can be seen from the shift in t ch . pet with 1 % sodium benzoate produced a moderately crystalline web with 9 . 82 percent crystalline fraction . other webs had essentially no detectable crystalline fraction . the additives , in fact , acted like diluents as can be seen from the reduction in t g values ( table 10 ). the crystals have a regular three - dimensional ordering with a definite melting point . the amorphous fractions have no order and become mobile at t g . the rigid amorphous fractions resemble the crystallite in properties and become mobile between t g and t m . the as - produced pet melt blown webs have a large fraction of rigid amorphous content that may be responsible for their high shrinkage values on further heat treatment . the least shrinkage value was obtained in the case of melt blown webs with pet and sodium benzoate although they had higher rigid amorphous content . thus the shrinkage behavior of melt blown pet webs was found to be very different depending on the type of additive used and the amount of crystalline , amorphous and rigid amorphous present in the sample . in the case of amorphous pet melt blown webs , the shrinkage could be attributed to the presence of large amount of oriented rigid amorphous fraction . there is no restriction on the motion of these rigid segments on exposure to heat because of the absence of crystallites as tie links . the crystallites already present in the web restrict the motion of the amorphous or the rigid amorphous molecules in the case of melt blown webs that contain pet in combination with sodium benzoate . in the case of pet melt blown fibers that contain lcp , the lcp component being of lower viscosity at the processing temperature range compared to pet , might encapsulate the pet phase forming a sheath - core composite structure . two model structures were proposed for melt blown fibers with pet and lcp as shown in fig1 . in both the cases , pet component is prevented from shrinking by the rigid lcp phase . thus the shrinkage values of the melt blown webs produced from blends were lower in all the cases with lcp as reinforcing phase . in fact , fracture studies performed on the melt blown fibers made of pet and pet / lcp blends revealed the evidence of a matrix - fibril type of composite fiber as shown in the sem pictures ( fig1 - 13 ). the droplets of the lcp component gets elongated into discontinuous fibrils within the matrix of pet as shown in the sem pictures . the shrinkage studies were also performed at 150 ° and 190 ° c . there was a considerable increase in the percentage shrinkage values in the case of pet fibers that contained no additives as shown in fig1 . even at 190 ° c . the fibers made of pet and additives had exceptional dimensional stability with shrinkage values less than 10 %. the fibers made of pet / lcp / sodium benzoate had higher shrinkage values compared to the rest of the samples in the figure that contained additives . dsc was used to determine the relative amounts of crystalline , amorphous and rigid amorphous contents of the shrunk melt blown fibers . fig1 illustrates the change in the percent rigid amorphous content with increase in shrinkage temperature . in all the cases , the samples were annealed with no constraint for the same period of time . pet fibers had considerably higher amount of oriented amorphous fraction compared to pet fibers that contained additives . among the fibers that contained additives , pet / lcp had the lowest value suggestive of very low shrinkage values . although , the rigid amorphous content was higher in the case of fiber that had pet / sodium benzoate , shrinkage was prevented by the crystallites present in the as - produced fibers . the competing mechanisms of shrinkage and crystallization are very evident from the above figures . the reduction in the rigid amorphous content of all samples at temperatures at 110 ° c . is due to the disorientation of the oriented amorphous chains . at 110 ° c ., this is presumed to be the dominant mechanism . at 150 ° c ., the material is already crystalline ( tch being 130 ° c . ), there is a further reduction in the rigid amorphous content . fig1 illustrates the increase in crystallinity content of different samples on annealing . crystallinity was detected only in the case of as - produced pet fibers that had sodium benzoate . the increase in crystallinity at 110 ° c . of all the samples other than pet is due to the presence of a greater number of nucleating sites on heating from the glassy state . this is also responsible for higher percent crystallinity values in the case of fibers that contained additives at higher shrinkage temperatures . thus in the case of pet fibers that had no additives , the shrinkage is mainly due to disorientation at 110 ° c . and above and the level of shrinkage is determined by the shrinkage and crystallization temperatures and times during annealing . presence of nuclei / additives influence a lot on the shrinkage and crystallization behavior the fibers . thus having a crystalline material to begin with is crucial in further heat treatments like annealing to prevent thermal shrinkage . a statistical correlation between percent shrinkage at 110 ° c . versus crystalline , amorphous and rigid amorphous contents of the fiber was obtained as shown in table 11 . although the data points were limited , a clear trend was observed between percent shrinkage values and different entities present in the fiber structure . shrinkage was found to be negatively correlated with the amount of crystalline and amorphous fractions present in the fiber . the rigid amorphous fraction was positively correlated with shrinkage indicating that an increase in rigid amorphous content would result in an increase of thermal shrinkage of the melt blown pet webs . this result was found to be significant at the 90 % confidence level . rigid amorphous content also had higher correlation values with shrinkage compared to crystalline and amorphous fractions . several statistical models were analyzed for the observed data points and the one with significant f - value , in this case an exponential model was chosen as shown in table 12 . the observed trends were also plotted along with the predicted model in fig1 - 19 . shrinkage studies were also performed at 150 ° and 190 ° c . the results are shown in fig2 . three sets of samples are shown to have similar percent shrinkage values . the presence of crystallites in the as - produced fibers has considerable influence on the percent shrinkage values of fibers . the shrinkage was found to increase with shrinkage temperature in the case of fibers that had no detectable crystallinity . the shrinkage values remained the same in the case of fibers that had crystallites in the as - produced material . the rigid amorphous content was found to decrease on annealing as shown in fig2 . the reason being the participation of oriented amorphous molecules in shrinkage and disorientation at 110 ° c . and 190 ° c . at 150 ° c ., the lowest values for the rigid amorphous content was observed . participation of rigid amorphous material in the crystallization process is the reason for this reduction in the rigid amorphous content . at 150 ° c ., the fibers undergo competing mechanisms of shrinkage and crystallization . the change in the rigid amorphous content is also determined by the initial status of the material such as the relative portions of the crystalline and rigid amorphous segments . thus the trend observed is similar to the one observed in the case of pet fibers with nucleating additives . no appreciable crystallinity was detected in the case of essentially amorphous fibers annealed at 110 ° c . for 3 minutes . however , the crystallinity was found to rapidly increase at 150 ° c ., the tch being 129 ° c . or so and remained almost at the same value at 190 ° c . as shown in fig2 . here again , the value of final percent crystallinity was dependent on the initial status of the material such as the presence of detectable crystallites / nuclei present in the fiber . the mean , standard deviation and cv % of fiber diameters for pet melt blown fibers produced with nucleating additives are shown in table 13 . mechanical and physical properties of melt blown webs with additives are shown in tables 14 and 15 . it was not possible to keep a constant basis weight and thickness of the samples because of the poor drawing action when lcp was blended with pet . however , loftier webs were produced in the case of blends . webs that contained lcp had higher air permeability values because of larger fiber diameters . it is very evident that the lower fiber diameters is the reason for lower air permeability values and thus higher filtration efficiency of the pet melt blown webs that contained sodium benzoate . bursting strength was observed to be lower in the case of webs that contained the additives . pet melt blown webs produced under different processing conditions with no additives in order to investigate the mechanism of shrinkage , pet samples were melt blown varying the process conditions such as the throughput rate , die - to - collector distance , air pressure at the die , air temperature and die temperature . the results from the as - produced fibers are shown in tables 16 and 17 and also in fig2 - 27 . an ice cooled amorphous pet film was taken as the reference material . the effect of orientation during melt blowing could be seen from the increase in the t g and the rigid amorphous content of the processed fibers . there was no appreciable difference in the t ch and t m values of the webs produced under different conditions . the crystalline fraction was found to slightly increase on increasing the air pressure at the die . this also resulted in a slight decrease in the rigid amorphous content . interestingly , the shrinkage values were found to be much lower in the case of melt blown webs produced at 4 psi air pressure at a throughput rate of 0 . 3 ghm . thus it can be seen that dimensional stability of webs could also be improved by processing pet at suitable conditions without any nucleating additive . increasing the cooling distance , i . e . the die - to - collector distance resulted in a decrease in crystallinity and an increase in the rigid amorphous content . the shrinkage value was found to be close to 40 %. an increase of about 20 ° c . in air temperature was not influential in reducing the shrinkage values . although there was a reduction in rigid amorphous content , no on - line thermal crystallization or annealing was found to occur . the web crystallinity was found to increase slightly on reducing the throughput rate to 0 . 15 ghm from 0 . 3 ghm . however , only a slight reduction in shrinkage was observed . the slight increase in crystalline and rigid amorphous fraction at low throughput rate could be due to the increase in elongation rate due to reduction in velocity of polymer at the die tip for the same air pressure . it is not clear whether this would result in any on - line stress induced crystallization . the ideal condition for processing pet of 0 . 9 i . v . could be the last segment as shown in fig2 . the crystallinity was found to increase with reduction in rigid amorphous fraction and a simultaneous decrease in shrinkage on processing the polymer at equal die and air temperatures , in this case , 271 ° c . the effect of changing different processing variables on the mechanical properties of the melt blown pet webs is shown in table 18 . it is evident that an increase in strength was obtained by increasing the air pressure at the die for the same throughput rate pet # 1 to pet # 3 !. this is due to the orientation of the molecular chains and finer fibers . finer the fibers , there are more number of fibers in a given cross section of the webs . this results in improved tenacity values . a slight increase in elongation and breaking energy indicates that the webs become tougher on increasing the air flow rate for the same throughput rate . a slight decrease in modulus was observed in the case of pet # 3 . an increase in cooling length or collection distance would reduce the thermal sticking or bonding between the fibers in the melt blown web . similar results were obtained on increasing the air temperature . although , the values of initial modulus were comparable , the webs became tougher as indicated by the higher breaking elongation and breaking energy values . the breaking tenacity showed a maximum for lower throughput rate samples . almost all the samples produced had ductile failure except pet # 8 . the failure behavior of pet # 8 webs was observed to be laminar type . there was very minimal thermal sticking between fibers that resulted in poor elongation and breaking energy values . although , pet # 8 is the ideal fabric for its improved thermal properties , it had poor mechanical properties . these samples also had much higher coefficient of variation when compared to the rest of the webs produced . the mean , standard deviation and cv % of fiber diameters for pet melt blown fibers produced without nucleating additives is shown in table 19 . the physical properties of pet melt blown webs produced under different processing conditions without any type of additive are shown in table 20 . an increase in the air pressure at the die was found to decrease the basis weight and thickness of webs . decrease in fiber diameter caused also a reduction in the air permeability and an increase in filtration efficiency . bursting strength increased with an increase in air pressure at the die . the basis weight and thickness were found to increase on increasing the cooling length or collection distance . the air permeability increased and the bursting strength decreased . similar results were obtained on increasing the air temperature for the same throughput rate , die to collector distance and air pressure at the die . a decrease in fiber diameter at lower throughput rate is manifested as a decrease in basis weight , thickness and air permeability when compared to webs produced at a higher throughput rate except in the case of pet # 8 . the web construction of pet # 8 is quite different from webs produced at the same throughput rate . the webs were loftier and permeable with very soft hand and high bursting strength . the references listed hereunder form part of the disclosure of this specification and are herein incorporated expressly by reference . the methods and products of the invention are exemplified herein by use of pet and of the illustrated nucleating additives . these exemplified methods and products are for illustration purposes only . the methods of the invention can be practiced using other suitable polyesters , such as homologues and co - polymers of pet , including poly ( propylene ), poly ( ethylene ), poly ( amide ), poly ( butylene terephthalate ) and poly ( isopropyl terephthalate ), and other suitable nucleating agents , as determined by a suitable screening test , such as the test described herein . table 1__________________________________________________________________________material , structure , trade name and sourcematerial chemical repeat unit trade name source__________________________________________________________________________pet ## str1 ## ssp hoechst celaneselcp ## str2 ## vectra hoechst celaneseionomer ## str3 ## surlyn dupontsodium benzoate ## str4 ## -- aldrich chemicalscopper cuso . sub . 4 . 5h . sub . 2 o -- aldrich chemicalssulfatepentahydrate__________________________________________________________________________ table 2______________________________________injection molding conditions______________________________________machine type arburg model no : 221 - 55 - 250die temperature 300 ° c . mold temperature 25 ° c . screw speed 200 rpm______________________________________ table 3______________________________________compounding conditions______________________________________machine type leistritz twin screw extruder with co - rotating screws ( 34 mm diameter ) pelletizer killiondie temperature 215 ° c . screw speed 200 rpmhead pressure 600 to 700 psicooling distance 4 to 5 &# 34 ; in water______________________________________ table 4______________________________________melt blowing conditions for pet withnucleating additives______________________________________samples produced :( 1 ) pet ( 2 ) pet + 10 % lcp ( 3 ) pet + 1 % sodium benzoate ( 4 ) pet + 10 % lcp + 1 % sodium benzoate ( 5 ) pet + 10 % lcp + 1 % ionomerconditions : throughput rate 0 . 4 grams / hole / min . die - to - collector distance 9 inchesair pressure 3 psidie temperature 274 ° c . air temperature 264 ° c . ______________________________________ table 5______________________________________melt blowing conditions for pet webs withoutany additives produced under differentprocess conditions die - to - air pressure throughput collector at air tem - die tem - sample rate distance the die perature peratureid ( ghm ) ( inches ) ( psi ) (° c .) (° c . ) ______________________________________pet # 1 0 . 3 4 1 . 5 282 282pet # 2 0 . 3 4 3 . 0 282 282pet # 3 0 . 3 4 4 . 0 282 282pet # 4 0 . 3 8 4 . 0 282 282pet # 5 0 . 3 8 4 . 0 304 282pet # 6 0 . 15 8 4 . 0 304 282pet # 7 0 . 15 8 4 . 0 288 276pet # 8 0 . 15 8 4 . 0 271 271______________________________________ table 6______________________________________shrinkage studies oven type - scientific products dk 63 temperature - 105 ° c . original length - 12 . 7 cm average treatmentmaterial thickness ( μ ) time ( min . ) ______________________________________pet 211 3pet + 1 % sod . benzoate 248 3pet + 10 % lcp 863 12pet + 10 % lcp + 1 % sod . benzoate 1195 17pet + 10 % lcp + 1 % ionomer 1479 21______________________________________ table 7______________________________________crystallization temperatures of injectionmolded pet and pet with additives at differentcooling rates cooling rates 20 ° c ./ 40 ° c ./ 60 ° c ./ material min . min . min . ______________________________________pet 208 . 2 144 . 6 69 . 9pet + 1 % liquid crystalline 207 . 5 139 . 1 57 . 8polyester ( lcp ) pet + 10 % lcp ( trade name - 203 . 9 145 . 7 57 . 4vectra ) pet + 1 % ionomer ( trade name - 208 . 3 139 . 2 57 . 6surlyn ) pet + 10 % ionomer 207 . 2 137 . 8 59 . 9pet + 2 % sodium benzoate 224 . 7 171 . 8 99 . 2pet + 2 % copper sulfate 206 . 3 147 . 7 58 . 2pentahydrate ( cu s ) pet + 1 % lcp + 2 % sodium 223 . 7 171 . 9 109 . 4benzoatepet + 10 % lcp + 1 % ionomer 210 . 3 144 . 6 53 . 8pet + 10 % lcp + 3 % ionomer 204 . 1 140 . 6 55 . 7pet + 10 % lcp + 2 % cu s 203 . 4 132 . 4 37 . 6lcp 234 . 0 190 . 5 139 . 3______________________________________ note : the samples were held at 300 ° c . for 3 minutes and then cooled at rates of 20 , 40 and 60 deg . c ./ min . the samples were also heate to 300 ° c . from 50 ° c . at a rate of 20 ° c ./ min . table 8__________________________________________________________________________transition temperatures and percentcrystallinity of injection molded pet with additives dsc parameters % crystallinity % crystallinity on heating on coolingmaterial t . sub . ch t . sub . m ( δh . sub . m - δh . sub . ch ) ( δh . sub . cc ) __________________________________________________________________________pet 129 . 2 257 . 0 n . d . 44 . 60pet + 1 % liquid crystalline polyester ( lcp ) 129 . 0 254 . 3 n . d . 46 . 66pet + 10 % lcp ( trade name - vectra ) 127 . 7 255 . 9 5 . 86 43 . 37pet + 1 % ionomer ( trade name - surlyn ) 127 . 8 255 . 8 2 . 43 45 . 95pet + 10 % ionomer 134 . 1 258 . 3 n . d . 46 . 76pet + 2 % sodium benzoate 117 . 4 261 . 2 23 . 74 46 . 82pet + 2 % copper sulfate pentahydrate ( cu s ) 134 . 8 258 . 1 8 . 21 47 . 16pet + 1 % lcp + 2 % sodium benzoate 119 . 6 260 . 4 10 . 8 48 . 66pet + 10 % lcp + 1 % ionomer 129 . 0 261 . 2 2 . 83 49 . 49pet + 10 % lcp + 3 % ionomer 129 . 0 255 . 9 2 . 03 44 . 11pet + 10 % lcp + 2 % cu s 124 . 3 261 . 2 9 . 02 50 . 47lcp -- ( t . sub . i ) negligible negligible 276 - 280__________________________________________________________________________ note : the samples were heated to 300 ° c . from 50 ° c . at a rate of 20 ° c ./ min . n . d . not detected ti temperature of isotropization table 9______________________________________transition temperatures and percentcrystallinity of pet melt blown webs with additives dsc parameters % crystallinity on heatingmaterial t . sub . ch t . sub . m ( δh . sub . m - δhch ) ______________________________________pet 130 . 4 258 . 6 n . d . pet + 10 % lcp ( trade name - vectra ) 124 . 1 256 . 3 n . d . pet + 1 % sodium benzoate 116 . 2 259 . 2 9 . 82pet + 10 % lcp + 1 % sodium benzoate 120 . 3 258 . 2 n . d . pet + 10 % lcp + 1 % ionomer 127 . 0 257 . 1 n . d . ______________________________________ note : the samples were heated to 300 ° c . from 50 ° c . at a rate of 20 ° c ./ min . n . d . means not detected table 10__________________________________________________________________________tg , percent crystalline , amorphous andrigid amorphous fractions and shrinkage for pet withnucleating additives percent percent percent rigid tg crystalline amorphous amorphous shrinkagematerial (° c .) fraction fraction fraction (%) __________________________________________________________________________pet 80 . 9 n . d . 18 . 30 81 . 7 30 . 70pet + 10 % lcp 74 . 3 n . d . 64 . 74 35 . 25 3 . 31pet + 1 % sodium benzoate 72 . 2 9 . 82 21 . 31 68 . 87 2 . 68pet + 10 % lcp + 75 . 8 n . d . 54 . 75 45 . 24 7 . 091 % sodium benzoatepet + 10 % lcp + 78 . 3 n . d . 31 . 07 68 . 93 2 . 831 % ionomer__________________________________________________________________________ table 11______________________________________correlation between shrinkage anddifferent structural entities present in pet meltblown webs produced with no additives ( annealing temperature - 110 ° c .) correlation coefficients shrink cryst amr rigid______________________________________shrink 1 . 0000 -. 4804 -. 4020 . 6172 ( 8 ) ( 8 ) ( 8 ) ( 8 ) p = . p = . 228 p = . 323 p = . 103cryst -. 4804 1 . 0000 -. 0591 -. 5161 ( 8 ) ( 8 ) ( 8 ) ( 8 ) p = . 228 p = . p = . 889 p = . 190amr -. 4020 -. 0591 1 . 0000 -. 8245 ( 8 ) ( 8 ) ( 8 ) ( 8 ) p = . 323 p = . 889 p = . p = . 012rigid . 6172 -. 5161 -. 8245 1 . 0000 ( 8 ) ( 8 ) ( 8 ) ( 8 ) p = . 103 p = . 190 p = . 012 p = . ______________________________________ ( coefficient /( cases )/ 2 - tailed significance ) &# 34 ;.&# 34 ; is printed if a coefficient cannot be computed table 12__________________________________________________________________________different statistical models and theirsignificanceindependent : rigid upperdependentmth rsq d . f . f sigf bound b0 b1 b2__________________________________________________________________________shrinklin . 381 6 3 . 69 . 103 - 107 . 90 1 . 6723shrinklog . 389 6 3 . 81 . 099 - 558 . 68 133 . 452shrinkinv . 396 6 3 . 94 . 095 159 . 038 - 10616shrinkqua . 434 5 1 . 91 . 241 - 1020 . 2 24 . 7888 -. 145shrinkcub . 434 5 1 . 91 . 241 - 1020 . 2 24 . 7888 -. 145shrinkcom . 445 6 4 . 82 . 071 . 0032 1 . 1166shrinkpow . 456 6 5 . 03 . 066 3 . 6e - 16 8 . 8149shrinks . 466 6 5 . 23 . 062 11 . 8722 - 702 . 18shrinkgro . 445 6 4 . 82 . 071 - 5 . 7574 . 1103shrinkexp . 445 6 4 . 82 . 071 . 0032 . 1103shrinklgs . 445 6 4 . 82 . 071 . 316 . 514 . 8956__________________________________________________________________________ table 13______________________________________mean , standard deviation and cv % offiber diameters for pet melt blown fibers producedwith nucleating additives standard coefficient of mean deviation variationsample id ( μ ) ( μ ) (%) ______________________________________pet 4 . 3 2 . 4 56pet + 1 % sb 1 . 6 1 . 4 88pet + 10 % lcp 17 . 7 10 . 3 58pet + 10 % lcp + 1 % sb 6 . 7 6 . 5 97pet + 10 % lcp + 1 % 28 . 0 9 . 8 35ionomer______________________________________ table 14______________________________________mechanical properties of pet meltblown webs produced with nucleating additives breaking initial breaking tenacity elongation modulus energysample id ( mn / tex ) (%) ( n / tex ) ( kg - m ) ______________________________________pet 16 . 2 42 . 0 0 . 68 0 . 097pet + 1 % sb 16 . 2 3 . 4 0 . 73 0 . 003pet + 10 % lcp 2 . 0 4 . 8 0 . 18 0 . 001pet + 10 % lcp + 1 % 2 . 1 5 . 1 0 . 10 0 . 003sbpet + 10 % lcp + 1 % 0 . 5 14 . 9 0 . 05 0 . 001ionomer______________________________________ table 15__________________________________________________________________________physical properties of pet melt blown webswith nucleating additives theoretical basis air bursting bending filtration weight thickness permeability strength rigidity efficiencysample ( gsm ) ( μ ) ( m . sup . 3 / m . sup . 2 / sec ) ( kpa ) ( mg - cm ) (%) __________________________________________________________________________pet 45 . 27 211 0 . 38 35 . 94pet + 1 % sb 23 . 16 248 0 . 29 11 . 06pet + 10 % lcp 43 . 14 863 5 . 84 8 . 99pet + 10 % lcp 137 . 62 1195 1 . 29 6 . 91 + 1 % sbpet + 10 % lcp 105 . 95 1479 4 . 19 13 . 13 + 1 % io__________________________________________________________________________ table 16______________________________________transition temperatures and percentcrystallinity values of pet melt blown websproduced under different processing conditions % crystallinity on heatingmaterial t . sub . ch t . sub . m ( δh . sub . m - δh . sub . ch ) ______________________________________pet ( ice cooled amorphous film ) 133 . 5 258 . 1 n . d . pet # 1 130 . 5 254 . 2 n . d . pet # 2 129 . 4 254 . 1 1 . 95pet # 3 129 . 3 254 . 1 4 . 43pet # 4 130 . 3 255 . 1 1 . 00pet # 5 132 . 5 254 . 1 n . d . pet # 6 132 . 5 255 . 3 4 . 35pet # 7 135 . 3 254 . 2 4 . 42pet # 8 131 . 1 255 . 4 8 . 13______________________________________ note : the samples were heated to 300 ° c . from 50 ° c . at a rate of 20 ° c ./ min . n . d . means not detected table 17______________________________________glass transition temperatures and amountof different structural entities present in as - produced pet melt blown webs produced with noadditives percent percent percent rigid tg crystalline amorphous amorphous shrinkagesample id (° c .) fraction fraction fraction (%) ______________________________________pet film 81 . 4 n . d . 70 . 79 29 . 21 -- pet # 1 83 . 5 n . d . 19 . 47 80 . 53 20 . 94pet # 2 83 . 4 1 . 95 14 . 61 83 . 44 19 . 37pet # 3 84 . 1 4 . 43 21 . 86 73 . 71 3 . 94pet # 4 83 . 8 1 . 00 12 . 16 86 . 84 37 . 95pet # 5 83 . 3 n . d . 24 . 35 75 . 65 36 . 69pet # 6 82 . 5 4 . 35 14 . 64 81 . 01 33 . 39pet # 7 83 . 8 4 . 42 14 . 59 80 . 99 36 . 85pet # 8 85 . 3 8 . 13 19 . 37 72 . 50 8 . 98______________________________________ table 18______________________________________mechanical properties of pet meltblown webs produced with nucleating additives breaking initial breaking tenacity elongation modulus energysample id ( mn / tex ) (%) ( n / tex ) ( kg - m ) ______________________________________pet # 1 11 . 0 27 . 3 0 . 55 0 . 028pet # 2 14 . 7 27 . 2 0 . 64 0 . 032pet # 3 19 . 7 30 . 9 0 . 44 0 . 050pet # 4 14 . 0 78 . 3 0 . 52 0 . 102pet # 5 13 . 9 112 . 0 0 . 46 0 . 133pet # 6 20 . 0 57 . 4 0 . 57 0 . 062pet # 7 20 . 8 36 . 5 0 . 64 0 . 032pet # 8 11 . 0 9 . 0 0 . 67 0 . 002______________________________________ table 19______________________________________mean , standard deviation and cv % offiber diameters for pet melt blown fibers producedwithout nucleating additives coefficient of mean standard deviation variationsample id ( μ ) ( μ ) (%) ______________________________________pet # 1 19 . 4 9 . 8 50pet # 2 6 . 6 2 . 4 36pet # 3 4 . 7 1 . 8 38pet # 4 6 . 7 3 . 0 45pet # 5 7 . 7 3 . 6 57pet # 6 4 . 4 2 . 4 54pet # 7 3 . 2 1 . 5 36pet # 8 4 . 4 1 . 7 38______________________________________ table 20__________________________________________________________________________physical properties of pet melt blown webswith no additives theoreticalbasis air bursting bending filtrationweight thickness permeability strength rigidity efficiencysample ( gsm ) ( μ ) ( m . sup . 3 / m . sup . 2 / sec ) ( kpa ) ( mg - 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