Facile Synthesis of Processable Semiaromatic Polyamides Containing

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Facile Synthesis of Processable Semiaromatic Polyamides Containing Thioether Units Gang Zhang,† Guang-Shun Huang,‡ Dong-Sheng Li,† Xiao-Jun Wang,† Sheng-Ru Long,† and Jie Yang*,†,§ †

Analysis & Testing Center, Sichuan University, Chengdu 610064, P. R. China College of Polymer Materials Science and Engineering of Sichuan University, Chengdu 610065, P. R. China § State Key Laboratory of Polymer Materials Engineering of China, Sichuan University, Chengdu 610065, P. R. China ‡

ABSTRACT: Semiaromatic polyamides containing thioether units were synthesized through the reaction of 4,40 -thiodibenzoyl chloride (TDC) and diamine by the method of interfacial polycondensation. The inherent viscosities of the resultant polyamides prepared with optimum synthesis conditions were 1.081.26 dL/g. These polyamides had excellent thermal properties with glass transition temperatures (Tg) of 119.8190.1 °C, melting temperatures (Tm) of 281.4355.5 °C, and initial degradation temperatures (Td) of 433.5466 °C. They had wider processing windows than traditional semiaromatic polyamides. At the same time, they had better tensile strengths of 62.186.5 MPa, better low-temperature mechanical properties, lower water absorption, lower dielectric constants of 3.163.81 at 100 kHz, and better melt flowability properties. The results suggest that these semiaromatic polyamides containing thioether units [poly(hexanelene 4,40 -thiodibenzoamide) (PA-6), poly(octanelene 4,40 thiodibenzoamide) (PA-8), and poly(decanelene 4,40 -thiodibenzoamide) (PA-10)] represent a promising type of heat-resistant and processable engineering plastic.

1. INTRODUCTION Nylons are types of engineering thermoplastics that play an important role in modern industrial and commercial applications. They can be easily produced by melt processing to form different kinds of structural parts or polymer fibers. At the same time, they can be made into nanofiltration membranes by a facile synthesis method: interfacial reaction.1 With increasingly stringent standards, applications of aliphatic polyamide are limited in some fields because of their poor dimensional stability and thermal properties, especially in surface mount technology (SMT) and the shells of automobile engines. To improve the thermal properties of polyamides, aromatic rings are incorporated into their backbones.27 The resultant aromatic polyamides such as poly(p-phenylene terephthalamide) (PPTA)8 and poly(m-phenyleneisophthalamide) (PMIA)9 have excellent mechanical and thermal properties, but they can be processed only by a special method.10,11 Then, semiaromatic polyamides were developed rapidly in the past 20 years. According to earlier reports, only several semiaromatic polyamides are commercially available. These include poly(hexamethylene terephthalamide) (PA6T),12 poly(nonamethylene terephthalamide) (PA9T), and so on.1316 These aromatic and semiaromatic polyamides have been noted for their high thermal stability, chemical resistance, strength, and modulus as fibers. However, it is impossible to produce them except for PA9T (Tg = 126 °C, Tm = 308 °C) and Zytel HTN (Tg = 141 °C, Tm = 300 °C) by a melting process because of their high melting temperatures (Tm of about 370 °C) and lower decomposition temperatures (Td ≈ 390 °C). However, the high cost of PA9T limits its applications. Usually, if the melting point of a semiaromatic polyamide is higher than 340 °C, it is not suitable for thermal processing.17 Therefore, several approaches have been developed through synthetic modifications such as incorporating long-chain diamines (Tm ≈ 290 °C, r 2011 American Chemical Society

Td ≈ 490 °C),1820 naphthalene rings (Tm = 320 °C, Td = 495 °C),21 benzylidene structure (Tm = 290 °C),22 cyclohexane and trifluoro groups (Tg ≈ 220 °C, Td ≈ 330 °C),23 bulky pendant groups (Tg ≈ 270 °C, Td ≈ 500 °C),24 and noncoplanar biphenylene moieties (Tg ≈ 300 °C, Td (10%) ≈ 510 °C)25 into the polymer backbones. It is known that the thioether bond is flexible. It can be incorporated into the polymer backbone and improve the resin’s processability, such as in poly(phenylene sulfide), poly(phenylene sulfide sulfone), and poly(phenylene sulfide ketone). The resulting materials have excellent processability and mechanical, thermal, and antioxidant properties.2630 Therefore, here, we incorporated a thioether group (S) into the main chain of semiaromatic polyamides to improve their processability. We prepared 4,40 -thiodibenzoic acid (TDA) and 4,40 -thiodibenzoyl chloride (TDC) by the reaction of sodium sulfide (Na2S 3 xH2O) with 4-fluorobenzoic acid. The interfacial polycondensation of TDC with 1,4-butanediamine (and ethylenediamine, 1,6-hexanediamine, 1,8-octanediamine, and 1,10decanediamine) resulted in thioether-containing semiaromatic polyamides. The chemical structures, thermal properties, thermal stabilities, mechanical properties, dielectric properties, water absorption properties, and processability characteristics of the resultant semiaromatic polyamides were studied and are presented in this article.

2. EXPERIMENTAL SECTION 2.1. Materials. 4-Fluorobenzoic acid (4-FBA) and the catalyst were made in our laboratory. Sodium sulfide (Na2S 3 xH2O, Received: January 26, 2011 Accepted: April 26, 2011 Revised: April 20, 2011 Published: April 26, 2011 7056

dx.doi.org/10.1021/ie200192v | Ind. Eng. Chem. Res. 2011, 50, 7056–7064

Industrial & Engineering Chemistry Research Scheme 1. Synthesis Route of 4,40 -Thiodibenzoyl Chloride (TDC)

∼60% Na2S) (Nafine Chemical Industry Group Co., Ltd.), sodium hydroxide (NaOH) (AR, SiChuan ChengDu ChangLian Chemical Reagent Company), N-methyl-2-pyrrolidone (NMP) (JiangSu NanJing JinLong Chemical Industry Company), and other reagents and solvents were obtained commercially. 2.2. Monomer Synthesis. 2.2.1. 4,40 -Thiobenzoic Acid (TDA) (Scheme 1). TDA was prepared according to the following procedure: 150 mL of NMP, 30 mL of toluene, 13.0 g (0.1 mol) of sodium sulfide, 8 g (0.20 mol) of sodium hydroxide, 28 g (0.2 mol) of 4-FBA, and 2.5 g of catalyst31 were added into a 500 mL three-necked flask equipped with a water segregator, a reflux condenser, a mechanical stirrer, and a thermometer. The reactor was heated to 180 °C for 3 h and held at that temperature for 2 h; during this time, 40.6 mL of liquid was removed. Then, the reaction flask was heated to 190 °C and maintained for 3 h, and the reaction solution was poured into deionized water and filtered. The filter liquor was acidified with 1 mol/L HCl to precipitate a cottony crude product under stirring. The crude product was then washed several times with water to remove possible residual salts. Next, the purified product was filtered, dissolved in a solution of NaHCO3, filtered, acidified with hydrochloric acid, and then filtered again. This process was repeated three times. The material was then vacuum-dried at 80 °C for more than 12 h to yield a pale-yellow crystalline powder. Yield: 22.6 g, 82.5%. Elemental analysis (%): Found: C, 61.22; H, 3.68. Calculated: C, 61.3; H, 3.67. FT-IR (KBr, cm1): 3057 (CH aromatic ring), 1693 (COOH), 1590, 1471 (CdC aromatic ring), 1086 (CSC), 823 (para substituent of the aromatic ring). 1H NMR [600 MHz, deuterated dimethyl sulfoxide (DMSO-d6)/ tetramethylsilane (TMS), ppm]: 7.357.36 (d, 4H, H1), 7.957.96 (d, 4H, H2), 12.97 (s, 2H, H3). 2.2.2. 4,40 -Thiobenzoyl Chloride (TDC). A mixture of 13.7 g (0.05 mol) of TDA, 80 mL of thionyl chloride (SOCl2), and 0.5 mL of dry pyridine were combined and stirred in a roundbottom flask at room temperature under N2 atmosphere in the dark for 3 h, after which the mixture was refluxed for 24 h. The mixture was then distilled to dryness under reduced pressure. The resulting residue was extracted at 70 °C with dry petroleum ether (bp 6090 °C). Then, the solvent was evaporated under reduced pressure, and the product was dried under a vacuum at 56 °C. Yield: 14.25 g, 91.9%. m/z (Mþ): 311.24. Elemental analysis (%): Found: C, 53.90; H, 2.68. Calculated: C, 54.04; H, 2.59. 2.3. Polymer Synthesis (Scheme 2). A typical polymerization was performed as shown in Scheme 2. In a 250 mL graduated cylinder, 24.8 g (0.08 mol) of TDC was dissolved in 126 mL of dichloromethane, and then, 125 mL of a solution of 1,6hexanediamine (6 mol/L, HDA) and NaOH (6 mol/L) was added into the graduated cylinder, which slowly filled with TDC solution. After about 10 s, a thin white membrane layer appeared

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Scheme 2. Synthesis Route of PA-2PA-10

on the interface. Then, the membrane was drawn out (shown in Figure 1ad). The collected polymer was washed with water and ethanol, pulverized to a powder, washed with water and ethanol again, and dried in a vacuum oven at 100 °C for 12 h to give PA-6 (yield: 26.8 g, 94.9%). PA-2, PA-4, PA-8, and PA-10 were prepared according to procedures similar to that used for PA-6. The yields were as follows: PA-2, 21.4 g (89.6%); PA-4, 24 g (92.3%); PA-8, 28.2 g (91.9%); PA-10, 30.6 g (92.7%). 2.4. Characterization. The inherent viscosities of PA-2PA10 were obtained in concentrated sulfuric acid at 30 ( 0.1 °C with 0.500 g of polymer dissolved in 100 mL of concentrated sulfuric acid, using a Cannon-Ubbelodhe viscometer. The resulting values were obtained by the one-point method (or SolomonCiuta equation) as follows qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2ðηsp ln ηr Þ ηinh ¼ C where ηr = η/η0 and ηsp = η/η0 1. The samples of monomer TDA, TDC, and PA-2PA-10 were measured with an elemental analyzer (EURO EA-3000). FT-IR spectroscopic measurements were performed on a Nexus670 FT-IR instrument. The mass spectral analysis was performed on a Bruker-Daltonics ESI instrument. 1H nuclear magnetic resonance (NMR) spectra were obtained on a Bruker-600 NMR spectrometer in deuterated chloroform, deuterated dimethyl sulfoxide, or deuterated trifluoracetic acid. X-ray diffraction (XRD) (Philips X0 pert Pro MPD) was used to study the polymers' aggregation structure. The samples were subsequently dried at 100 °C in a vacuum oven for 12 h and then heated at 200 °C for 4 h. Differential scanning calorimetry (DSC) was performed on a Netzsch DSC 200 PC thermal analysis instrument. The heating rate for the DSC measurements was 10 °C/ min. Thermogravimetric analysis (TGA) was performed on a TGA Q500 V6.4 Build 193 thermal analysis instrument with a heating rate of 20 °C/min under a nitrogen atmosphere. The water-absorbing capacities of the samples were measured according to standard GB/T1034. An Instron Corporation 4302 instrument was used to study the stressstrain behavior of the samples. Dynamic mechanical analysis (DMA) was performed on a TA-Q800 apparatus operating in tensile mode at a frequency of 1 Hz in the temperature range from 130 to 250 °C with a heating rate of 5 °C/min. A Haake Crake capillary rheometer (Haake MiniLab II) was used to measure the melt flow behavior of thermoplastics PA-6PA-10. Measurements were carried out at 320 °C (PA-6), 305 °C (PA-8), and 295 °C (PA-10) under a shear rate ranging from 20 to 1170 s1. (PA-2 and PA-4 experienced degradation during the measurement process, so results could not be detected.) Quantitative information for the 7057

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Industrial & Engineering Chemistry Research

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Figure 1. (a) Solution of diamine and TDC, (b) formation procedure of polyamide, (c) drawing of polyamides, and (d) collected polymer.

Figure 3. 1H NMR spectrum of TDC.

Figure 2. FT-IR spectrum of TDC.

melt flow of the samples could be obtained by recording the shear rate and apparent viscosities during processing. Dielectric constants were measured on a TH2819A instrument in the frequency range of 0.1100 kHz at 25 °C. The solubilities of the polymers in various solvents were tested at room temperature, and the boiling points of the solvents were used.

3. RESULTS AND DISCUSSION 3.1. Monomers. 3.1.1. Synthesis of TDC. The synthesis route of TDC is shown in Scheme 1. TDC was prepared through a twostep procedure. First, 4-FBA was reacted with sodium sulfide

under nitrogen to provide TDA. Then, TDA was converted to TDC through reaction with SOCl2.32 This procedure must be performed under anhydrous conditions, or the yield will be very low. 3.1.2. Chain Structure of TDC. Figure 2 shows the FT-IR spectrum of TDC. The characteristic absorptions near 1766 and 1727 cm1 suggest the formation of COCl. We observed the characteristic absorptions of benzene rings near 1579 and 1478 cm1, the characteristic absorptions of S near 1076 cm1, and the characteristic absorptions of para-substituted benzene rings near 833 cm1. Figure 3 shows the 1H NMR spectrum of TDC. Two groups of peaks appeared in the 1H NMR spectrum. (The chemical shifts of TDC are listed in Table 1.) Combining the FT-IR and elemental analysis results suggests that we prepared the monomer as depicted in Scheme 1. 3.2. Polymers. 3.2.1. Synthesis of PA-2PA-10. The polycondensation reaction of the diamine and TDC was conducted 7058



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Table 1. Chemical Shifts (δ) of TDC δ (ppm) H1

7.4597.473

H2

8.0728.086

Figure 5. 1H NMR spectrum of PA-2.

Table 2. Elemental Analysis Results for PA-2PA-10a

Figure 4. FT-IR spectra of PA-2PA-10. a

by an interfacial polymerization method at room temperature as shown in Figure 1ad. The polymer membrane was subsequently drawn out with interfacial polymerization. The polymerization temperature in this procedure cannot exceed 30 °C, or the interface can be destroyed, in which case it is difficult to obtain a high-molecular-weight resin. 3.2.2. Inherent Viscosity (ηinh) of PA-2PA-10. The molecular weights of PA-2PA-10 were determined by ηinh measurements. The ηinh values of PA-2PA-10 were in the range of 1.081.26 dL/g. This suggests that the resultant polyamides had higher molecular weights. 3.2.3. Chain Structure of PA-2PA-10. Figure 4 shows the FT-IR spectra of PA-2PA-10. Compared with the spectrum of the monomer (TDC), the characteristic absorptions near 3300 and 1640 cm1 suggest the formation of amide (CONH). At the same time, we observed the characteristic absorptions of benzene rings near 1580, 1540, and 1480 cm1; the characteristic absorptions of CH2 near 2930 and 2850 cm1; and the characteristic absorption of S near 1080 cm1, whereas the characteristic absorptions of COCl (1766 and 1727 cm1) disappeared. Figure 5 shows the 1H NMR spectrum of PA-2. Three groups of peaks appear in this spectrum. The aromatic protons can be observed at 7.5057.808 ppm. The ratio of the corresponding integral curves was H1/H2/H3 = 1:1:1. In combination with the FT-IR results, these three groups of peaks were ascribed to H1, H2, and H3. At the same time, the elemental analysis (shown as in Table 2) showed that the experimental results were similar to the calculated results. Above all, this suggests that the polymers were successfully synthesized as shown in Scheme 2. The structures of PA-4PA-10 were confirmed by elemental analysis and 1H NMR spectroscopy, as shown in Figures 69. (The chemical shifts of PA-2PA-10 are listed in Table 3.) The peak near 11.61 ppm in the 1H NMR spectrum is attributed to the bond of amide (CONH) and trifluoroacetic acid. Because of the strong polarization effects, we could not distinguish the proton peaks of the amide and trifluoroacetic acid.

polymer

C (%)

H (%)

N (%)

PA-2 PA-4

64.75 (64.41) 65.89 (66.23)

4.70 (4.73) 5.66 (5.56)

9.85 (9.39) 8.92 (8.58)

PA-6

67.85 (67.77)

6.26 (6.26)

7.92 (7.9)

PA-8

69.02 (69.08)

6.87 (6.85)

7.26 (7.32)

PA-10

70.19 (70.21)

7.36 (7.36)

6.77 (6.82)

Data in parentheses were those calculated.


3.2.4. Aggregate Structure of PA-2PA-10. X-ray diffraction patterns of PA-2PA-10 samples that had been annealed at 200 °C are shown in Figure 10. As shown in Figure 9, PA-6PA10 exhibited obvious crystalline peaks at about 8.5°, 20°, 20.9°, 22.3°, and 29.5°. This suggests PA-6PA-10 were semicrystalline. As the crystalline peaks of PA-2 and PA-4 were not stronger than those of PA-6PA-10, these results suggest that longer aliphatic chains are beneficial to the crystallinity of these polyamides. 3.2.5. Thermal Properties of PA-2PA-10. The thermal properties of PA-2PA-10 were examined by DSC and TGA. The results are displayed in Figures 11 and 12, respectively. As shown in Figure 10, the Tg values of PA-2PA-10 were in the range of 119.8190.1 °C (in Table 4). Following decreasing order of chain flexibility, PA-4 exhibited the highest Tg value (190.1 °C) in this series. However, PA-2 had a lower Tg value because it has a lower molecular weight than PA-4, and 7059



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Table 3. Chemical Shifts (δ) of PA-2PA-10 chemical shifts δ (ppm) polymer

H1

H2

PA-2 4.0404.061 7.505 PA-4 1.999

H3

H4

H5

7.808

3.7833.829 7.540

7.809

PA-6 1.4891.591 1.7771.877 3.6583.760 7.4387.545 7.6947.790 PA-8 1.3861.462 1.6271.820 3.6263.732 7.4207.516 7.6697.765 PA-10 1.4201.504 1.484

3.759

7.546

7.798


Figure 10. XRD profiles of PA-2PA-10.


Figure 11. DSC curves of PA-2PA-10 obtained at a heating rate of 10 °C/min.


PA-6PA-10 had relatively lower Tg values because of their longer aliphatic chains and flexible thioether components. The DSC curves of PA-4PA-10 exhibited obvious melting endothermic peaks at 281.4, 293.8, 313.6, and 355.5 °C, respectively. Thus, the DSC measurements also revealed the semicrystalline

nature of PA-4PA-10. That agrees with the results of X-ray diffraction. The curve of PA-6 showed a double-melting endotherm, which is a common phenomenon for semicrystalline polymers.3335 Moreover, the Tg and Tm values for PA-6 and PA-8 were found to be close to those for PA9T (Tg= 126 °C, Tm= 308 °C),23 which suggests that incorporating a flexible thioether unit into the polymer backbone can improve the processability significantly. As shown in Figure 12, the initial degradation temperatures (T5%) of PA-2PA-10 in nitrogen were 430, 433.5, 466, 462, and 464.6 °C, which are close to those of PA9T (Td = 464 °C) and PA10T (Td = 472 °C). These results suggest that the thermal stability was also improved by inserting a thioether linkage into the polymeric backbone. At the same time, we found that these polyamides had a small amount of 7060



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decomposition (shown in the magnified section of Figure 12) near 340 °C. Combined with the results of DSC, this indicates that PA-6PA-10 have suitable melting point (Tm) for processing, whereas the Tm value of PA-4 was higher than 340 °C, and PA-2 did not have a melting endothermic peak below 400 °C. This indicates PA-6PA-10 are suitable for thermal processing (but not PA-2 and PA-4). 3.2.6. Water Absorption. The water-absorbing capacities of PA-4PA-10 (PA-2 could not be processed) were measured according standard GB/T1034. The results are summarized in Table 4. As shown in Table 4, the water-absorbing capacities of PA-4PA-10 were found to be 0.20%, 0.21%, 0.18%, and 0.13%, respectively, which are close to that of the commercial product PA9T (0.17%). The water absorption decreased with lengthening of the aliphatic chain of the polyamides. Therefore, the results indicate that these polyamides have lower water-absorbing capacities, which is good for their dimensional and mechanical stability. 3.2.7. Tensile Properties. The average tensile strength values of PA-6PA-10 are given in Table 5. (PA-2 and PA-4 were so weak that mechanical properties could not be measured because they underwent degradation during the melting process, especially

PA-2.) As shown in Table 5, the average tensile strengths of PA-6PA-10 were 73.8, 86.5, and 62.1 MPa, respectively. The elongation at break was in the range of 9.813.7%. This suggests that PA-6PA-10 have better tensile properties, although they are not as good as those of the commercial product PA9T.22,36 3.2.8. Dynamic Mechanical Analysis. DMA was used to characterize the resulting polyamides. As shown in Figure 13, two obvious transition behaviors can be observed; they are defined as R and β relaxation, respectively. It is well-known that the glass transition temperature (Tg) of a polyamide can be determined by R relaxation, as it is usually related to the segment movements in the noncrystalline area.21,37 The β relaxation reflects the mobility of carbonyl group of amorphous region, The temperatures of R relaxation of these polyamides were found to be 142.6, 132, and 119.8 °C, respectively. The corresponding temperatures of β relaxation were found to be 64.8, 55.2, and 58.5 °C. Usually, semiaromatic polyamides have three relaxations denoted R, β, and γ relaxation. Here, PA-6PA-10 have lower β-relaxation temperatures, so one can calculate that they have low γ-relaxation temperatures and fine low-temperature mechanical properties. The R-relaxation temperatures (glass transition temperature) decreased with increasing amount of flexible-chain methylene in the polymeric backbone. Figure 14

Figure 12. TGA curves of PA-2PA-10 obtained at a heating rate of 20 °C/min in N2.

Figure 13. Dynamic mechanical analysis curves of PA-6PA-10.

Table 4. Physical Properties of the Obtained Polyamides Compared to Those of PA9T and PA10T polymer

Tg (°C)

Tm(°C)

Td (°C)

inherent viscosity (dL/g)

water absorption (%)

430 433.5

0.87 1.08

0.2

PA-2 PA-4

181.3 190.1

355.5

PA-6

166.7

300.3, 313.6

466

1.12

0.21

PA-8

161

293.8

462

1.24

0.18

PA-10

152.2

281.4

464.6

1.26

0.13

PA9T

126

308

464

1.96

0.17

PA10T

118

302

472

2.07

0.15

Table 5. Tensile Properties of PA-6PA-10 Compared to Those of PA9T polymer

tensile strength (MPa)

elongation at break (%)

storage modulus at 110 °C (GPa)

PA-6 PA-8

73.8 86.5

9.8 11.3

2.67 2.55

PA-10

62.1

13.7

2.18

PA9T

92

20

2.6

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Table 6. Dielectric Constants of PA-4PA-10 Compared to Those of PA9T dielectric constant

Figure 14. Storage modulus and loss modulus curves of PA-6PA-10.

polymer

thickness (mm)

0.1 kHz

1 kHz

10 kHz

100 kHz

PA-4

1.156

3.50

3.36

3.43

3.17

PA-6

1.100

3.43

3.34

3.46

3.16

PA-8

1.148

3.46

3.41

3.55

3.29

PA-10

1.144

4.29

4.14

4.18

3.81

PA9T

1.137

4.06

3.78

3.92

3.64

Table 7. Corrosion Resistance Behaviorsa of PA-4PA-10 Compared to That of PA9T polymers solvent

Figure 15. Plot of apparent viscosity versus shear rate for PA-6PA-10.

displays the storage modulus curves of PA-6PA-10. As listed in Table 5, the polyamides exhibited high storage moduli beyond 2.1 GPa at 110 °C, which indicates that these polyamides have excellent mechanical properties. 3.2.9. Rheological Properties. A rheological study was used to evaluate the effects of the structure of the resulting polyamides on the flow properties of the materials. The apparent viscosities of PA-6PA-10 measured in a crack capillary rheometer are shown in Figure 15. The measurements for the polymers were readily recorded in the shear rate range of 701170 s1. The melts of the polyamides exhibited much more stability under high shear rates. The viscosities ranged from 24.8 to 372.3 Pa 3 s at different shear rates. This suggests that the resultant polyamides have good flowability. When a long aliphatic chain was introduced into the main chain of the polyamide, the apparent viscosity of the polymer increased, and the longer the polyamide aliphatic chain, the higher the viscosity. This result mainly arises because the interactions between molecules become stronger as the polymer molecular chains become longer. Consequently, more entangled points should exist, and the apparent viscosity of the polymer melts should get higher. Thus, the polymers' apparent viscosity variation at different shear rates became larger for longer aliphatic chains of the polyamide. This indicates that these resins become more shear-sensitive as the polymers’ aliphatic chains become longer. 3.2.10. Dielectric Constant. Table 6 summmarizes the dielectric constants of PA-4PA-10, which are in the range of 3.163.81 at 100 kHz. These low dielectric constants can be

a

PA9T PA-2 PA-4 PA-6 PA-8 PA-10

concentrated sulfuric acid

þ

þ

þ

þ

þ

þ

formic acid

NMP

CF3COOH HCl

þ

þ

þ

þ

þ

þ

acetone

chloroform

DMSO

1,4-dioxane

toluene

phosphoric acid

þ

(

(

phenol þ tetrachloroethane

þ, soluble at room temperature; (, swelling; , insoluble with heating.

attributed to the low polarizability of the CH bonds of the alkyl groups and the low water-adsorbing capacities of the polymers. 3.2.11. Corrosion Resistance. Table 7 reports the solubilities of PA-2PA-10. These materials were found to be soluble in concentrated sulfuric acid and trifluoracetic acid at room temperature, but they were insoluble in NMP, DMF, formic acid, toluene, 1,4-dioxane, HCl, concentrated phosphoric acid, and so on. Compared to alkyl polyamides and PA9T, PA-2PA-10 show better corrosion resistance.

4. CONCLUSIONS PA-2PA-10 were prepared by an interfacial polycondensation reaction. The chemical structures, thermal performances, low-temperature mechanical properties, rheological properties, and dielectric properties were investigated. It was found that the structure of semiaromatic polyamides has an obvious effect on the melting point, water absorption, and rheology. Moreover, the performance of the polyamides could be improved by changing the structure of the aliphatic diamine. The resultant semiaromatic polyamides are suitable for melting processes when the number of repeat units (methylene) in the aliphatic diamine that is reacted with TDC is greater than 4. One can obtain resins that exhibit excellent performance from more affordable diamines (such as 1,6-hexanediamine) than PA9T. The melting point and water absorption were found to decrease and the melt processing window to become wider with increasing aliphatic chain length in the polymers. In contrast, the 7062


Industrial & Engineering Chemistry Research apparent viscosity of these polyamides continuously increased. All of the polyamides exhibited good thermostability, corrosion resistance, low-temperature mechanical properties, and low dielectric constants, almost the same as the properties of PA9T.

’ AUTHOR INFORMATION Corresponding Author

*E-mail: [email protected]. Fax: 86-28-8541-2866.

’ ACKNOWLEDGMENT This work was supported by research grants from the National High Technology Foundation of China (863 program Grant 2007AA03Z561). ’ REFERENCES (1) Ahmad, A. L.; Ooi, B. S.; Mohammad, A. W.; Choudhury, J. P. Composite nanofiltration polyamide membrane: A study on the diamine ratio and its performance evaluation. Ind. Eng. Chem. Res. 2004, 43, 8074–8082. (2) Ellis, T. S. Aromatic polyamide blends: Enthalpy relaxation and its correlation with phase phenomena. Macromolecules 1990, 23, 1494–1503. (3) Persyn, O.; Miri, V.; Lefebvre, J. M.; Ferreiro, V.; Brink, T.; Stroeks, A. Mechanical behavior of films of miscible polyamide 6/polyamide 6I6T blends. J. Polym. Sci. B: Polym. Phys. 2006, 44, 1690–1701. (4) Endo, M.; Morishima, Y.; Yano, S.; Tadano, K.; Murata, Y.; Tsunashima, K. Miscibility in binary blends of aromatic and alicyclic polyamides. J. Appl. Polym. Sci. 2006, 101, 3971–3978. (5) Liu, Y.; Donovan, J. A. Miscibility and crystallization semicrystalline nylon 6 and amorphous nylon 6IcoT blends. Polymer 1995, 36, 4797–4803. (6) Brisson, J.; Breault, B. Miscibility of polyamide blends. 1. Molecular modeling of poly(n-methyleneisophthalamide)poly(metaphenyleneisophthalamide) blends. Macromolecules 1991, 24, 495–504. (7) Shibayama, M.; Uenoyama, K.; Oura, J. I.; Nomura, S.; Iwamoto, T. Miscibility and crystallinity control of nylon 6 and poly(m-xylene adipamide) blends. Polymer 1995, 36, 4811–4816. (8) Rao, Y.; Waddon, A. J.; Farris, R. J. Structureproperty relation in poly(p-phenylene terephthalamide) (PPTA) fibers. Polymer 2001, 42, 5937–5946. (9) Ferreiro, J. J.; dela, C. J. G.; Lozano, A. E.; de, A. J. Polyisophthalamides with heteroaromatic pendent rings: Synthesis, physical properties, and water uptake. J. Polym. Sci. A: Polym. Chem. 2005, 43, 5300–5311. (10) Wang, F. D.; Peng, T.; Cui, X. J.; Li, L. Y.; Li, X. Q. Polyphenylene terephthalamide fibre and preparation method thereof. Chinese Patent CN101724935A, 2010. (11) Song, C. Y.; Song, X. Q.; Wang, Y. C.; Wang, X.; Gao, D. Production method of high-strength high-modulus PMIA super-short fiber. Chinese Patent CN101736431A, 2010. (12) Ballistreri, A.; Garozzo, D.; Giuffrida, M.; Maravigna, P. Thermal decomposition processes in aliphatic-aromatic polyamides investigated by mass spectrometry. Macromolecules 1986, 19, 2693–2699. (13) Uddin, A. J.; Ohkoshi, Y.; Gotoh, Y.; Nagura, M.; Hara, T. Influence of moisture on the viscoelastic relaxations in long aliphatic chain contained semiaromatic polyamide, (PA9-T) fiber. J. Polym. Sci. B: Polym. Phys. 2003, 41, 2878–2891. (14) Uddin, A. J.; Ohkoshi, Y.; Gotoh, Y.; Nagura, M.; Hara, T. Melt spinning and laser-heated drawing of a new semiaromatic polyamide, PA9-T fiber. J. Polym. Sci. B: Polym. Phys. 2004, 42, 433–444. (15) Uddin, A. J.; Gotoh, Y.; Ohkoshi, Y.; Nagura, M.; Endo, R.; Hara, T. Hydration in a new semiaromatic polyamide observed by

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humidity-controlled dynamic viscoelastometry and X-ray diffraction. J. Polym. Sci. B: Polym. Phys. 2005, 43, 1640–1648. (16) Uddin, A. J.; Ohkoshi, Y.; Gotoh, Y.; Nagura, M.; Endo, R.; Hara, T. Effects of take-up speed of melt spinning on the structure and mechanical properties of maximally laser drawn PA9-T fibers. Int. Polym. Process. 2006, 21, 263–271. (17) Yang, H. H. Aromatic High-Strength Fibers; Wiley: New York, 1989. (18) Spiliopoulos, I. K.; Mikroyannidis, J. A.; Tsivgoulis, G. M. Rigid-Rod Polyamides and Polyimides Derived from 4,300 -Diamino20 ,60 -diphenyl- or Di(4-biphenylyl)-p-terphenyl and 4-Amino-400 -carboxy-20 ,60 -diphenyl-p-terphenyl. Macromolecules 1998, 31, 522–529. (19) Liaw, D. J.; Liaw, B. Y.; Tseng, J. M. Synthesis and characterization of novel poly(amideimide)s containing hexafluoroisopropylidene linkage. J. Polym. Sci. A: Polym. Chem. 1999, 37, 2629–2635. (20) Yang, S. H.; Fu, P.; Liu, M. Y.; Wang, Y. D.; Zhang, Y. C.; Zhao, Q. X. Synthesis, characterization of polytridecamethylene 2,6-naphthalamide as semiaromatic polyamide containing naphthalene-ring. Express Polym. Lett. 2010, 4, 442–449. (21) Yang, S. H.; Fu, P.; Liu, M. Y.; Wang, Y. D.; Li, Z. P.; Zhao, Q. X. Synthesis, characterization and thermal decomposition of poly(decamethylene 2,6-naphthalamide). Express Polym. Lett. 2010, 4, 346–354. (22) Wang, W. Z.; Zhang, Y. H. Environment-friendly synthesis of long chain semiaromatic polyamides. Express Polym. Lett. 2009, 3, 470–476. (23) Li, P. H.; Wang, C. Y.; Li, G.; Jiang, J. M. Highly organosoluble and transparent polyamides containing cyclohexane and trifluoromethyl moieties: Synthesis and characterization. Express Polym. Lett. 2009, 3, 703–712. (24) Liaw, D. J.; Hsu, P. N.; Chen, W. H.; Lin, S. L. High glass transitions of new polyamides, polyimides, and poly(amideimide)s containing a triphenylamine group: Synthesis and characterization. Macromolecules 2002, 35, 4669–4676. (25) Liaw, D. J.; Chang, F. C.; Leung, M. K.; Chou, M. Y.; Muellen, K. High thermal stability and rigid rod of novel organosoluble polyimides and polyamides based on bulky and noncoplanar naphthalene biphenyldiamine. Macromolecules 2005, 38, 4024–4029. (26) Yang, J. PAS Resin and Its Applications; Chemical Industry Press: Beijing, China, 2006. (27) Xu, S. X.; Yang, J.; Long, S. R.; Chen, Y. R.; Li, G. X. Synthesis and characterization of poly(p-phenylene sulfide sulfone/ketone) copolymer. Polym. Bull. 2005, 54, 251–261. (28) Liu, Y.; Bhatnagar, A.; Ji, Q.; Riffile, J. S.; McGrath, J. E.; Geibei, J. F.; Kashiwagi, T. Influence of polymerization conditions on the molecular structure stability and physical behavior of poly(phenylene sulfide sulfone) homopolymers. Polymer 2000, 41, 5137–5146. (29) Wang, H. D.; Yang, J.; Long, S. R.; Wang, X. J.; Yang, Z.; Li, G. X. Studies on the thermal degradation of poly(phenylene sulfide sulfone). Polym. Degrad. Stab. 2004, 83, 229–235. (30) Yang, J.; Wang, H. D.; Xu, S. X.; Li, G. X.; Huang, Y. J. Study on polymerization conditions and structure of poly(phenylene sulfide sulfone). J. Polym. Res. 2005, 12, 317–323. (31) Yang, J.; Zhang, G.; Long, S. R.; Wang, X. J.; Liu, J.; Chen, Y. R. Polyarylene amide sulfides polymers and preparation method thereof. Chinese Patent CN101215379, 2008. (32) Zhang, G.; Zhang, M. L.; Wang, X. J.; Long, S. R.; Yang, J. Synthesis of high refractive index polyamides containing thio-ether units. J. Macromol. Sci. A: Pure Appl. Chem. 2010, 47, 892–902. (33) Li, Y.; Zhu, X.; Tian, G.; Yan, D.; Zhou, E. Multiple melting endotherms in melt-crystallized nylon 10,12. Polym. Int. 2001, 50, 677–678. (34) Ramesh, C.; Keller, A.; Eltink, S. J. Studies on the crystallization and melting of nylon 66: 3. Melting behaviour of negative spherulites by calorimetry. Polymer 1994, 35, 5300–5302. (35) Hybart, F. J.; Platt, J. D. The melting of 66 nylon: Observations by differential thermal analysis. J. Appl. Polym. Sci. 1967, 11, 1449–1453. 7063



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(36) Ma, J. M.; Song, S. W.; Guo, J. New heat resistance polyamide. Mod. Plast. Process. Appl. 2003, 15, 41–44. (37) Li, W. H.; Yan, D. Y. Synthesis and characterization of nylons based on hexadecane diacid. J. Appl. Polym. Sci. 2003, 88, 2462–2467.

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Facile Synthesis of Processable Semiaromatic Polyamides Containing

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