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1.
A series of new aliphatic/aromatic copolyesters [poly(hexylene terephthalate‐co‐hexylene adipate) (PHTA)] were synthesized on the bases of 1,6‐hexanediol, adipic acid, and dimethyl terephthalate and characterized by gel permeation chromatography, 1H‐NMR, wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and compost testing. 1H‐NMR results show that the compositions of the copolyesters were in accordance with the feed molar ratios. The WAXD patterns indicated that the crystal structures of the PHTA copolyesters were determined by the dominant crystal units, and the copolyesters became less crystallizable, even amorphous, with increasing comonomer content. The DSC curves showed that the glass‐transition temperatures (Tg′s) of the PHTA copolyesters decreased linearly, and both the melting temperature (Tm) and heat of fusion decreased first and then increased with increasing hexylene adipate unit content. Under compost conditions, PHTA copolyesters with less than 60 mol % aromatic units were biodegradable. Particularly, compared with the copolyester poly(butylene terephthalate‐co‐butylene adipate), the PHTA copolyester with the same aliphatic/aromatic composition possessed a lower Tg and Tm and better biodegradability. Additionally, the biodegradability of the copolyesters could be predicted by the number‐average sequence length of aromatic units, Tg, and the temperature difference between Tm and the temperature at which biodegradation took place. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 相似文献
2.
Zhongfu Zhao Zhanyue Wang Chunqing Zhang Yongzhao Wang Zhansheng Li Yanming Hu Xuesong Xiao 《应用聚合物科学杂志》2014,131(11)
Polar polystyrene‐isoprene‐styrene (SIS) copolymers having epoxide groups and long polybutadiene (PB) branches were synthesized via the combination of in situ epoxidation, anionic polymerization and graft‐onto reaction. They were characterized with 1H NMR, GPC, FT‐IR, DSC, and contact angle test. Their polarity was determined by the epoxidation degree and graft efficiency. The epoxidation degree linearly increased with the epoxidation time. The graft efficiency decreased with the branch length, but increased with the epoxidation degrees. Although their glass transition temperature (Tg) of diene blocks and flexibility properties had been negatively affected by in situ epoxidation, they could be modulated by the epoxidation degree, branch length, and branch density. Their Tg could be tailored by the branch length and branch density since they fitted the Fox equation very well, especially as the longer branches were grafted. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40303. 相似文献
3.
Poly(ethylene naphthalate) (PEN) copolymers were prepared by melt polycondensation of dimethyl naphthalate and excess ethylene glycol with 5–40 mol % (in feed) of 1,3‐propanediol or 2,2‐dialkyl‐1,3‐propanediols, where the dialkyl groups are dimethyl, diethyl, and butyl‐ethyl. No significant depression of reduced specific viscosity was observed. The comonomer contents in the copolymers are considerably higher than those in the feed. The effects of the copolymer composition on the structures of the films were investigated using thermal analyses, density measurements, X‐ray diffraction methods, and other physical tests. The crystallinities and densities of heat‐treated films decreased with increasing content of comonomer and length of alkyl side chain in the comonomer. The glass transition temperature (Tg) and melting temperature (Tm) were decreased by the copolymerization, while an increase in the length of the alkyl side chain hardly affected Tms of the heat‐treated films. Alkali resistance, moisture resistance, dye ability, and thermal shrinkage were increased by the incorporation of comonomer having an alkyl side chain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2754–2763, 2001 相似文献
4.
The crystallization and morphology of some metallocene polyethylenes with well‐controlled molecular weight and branching content were investigated by DSC, WAXD, PLM and SALS. The banded spherulites observed in linear PE are not seen in crystallization of branched PEs. The small spherulites with small lamellae or fringed micelle crystals are formed when branching content is higher, as suggested by PLM and SALS. The expansion of the unit cell was observed by WAXD as the molecular weight and branching content increased. At even higher branching content (more than 7 mol%), a shrinkage of the unit cell was seen, probably due to a change of crystal morphology from lamellar‐like crystals to fringed micelle‐like crystals. Crystallization temperature, melting point and crystallinity are greatly decreased for branched PEs compared with linear PEs. The equilibrium melting temperature cannot be determined via the Hoffman–Weeks approach for branched PEs since Tm is always 5–6 °C higher than Tc and there is no intercept with the Tm = Tc line. Our results show a predominant role of branches in the crystallization of polyethylene. © 2003 Society of Chemical Industry 相似文献
5.
The thermal properties of a set of experimental aliphatic–aromatic polyamides containing ether linkages were examined as a function of their chemical structure. Variations of the glass transition temperature (Tg) and melting temperature (Tm) could be correlated with the length of the aliphatic spacers and with the orientation of the phenylene rings. Polymers with a high concentration of p-oriented phenylene units showed a higher Tg than those containing mainly m-oriented ones; Tg values ranged from 110 to 155°C. Surprisingly, a negligible dependence of Tgs on the nature of flexible spacers was observed. For all of the polymers, the thermal stability was virtually the same, about 440°C, when tested by dynamic thermogravimetric analysis (TGA). However, quite different levels of thermal stability were found by isothermal TGA analysis for polyamides with different flexible spacers. Moreover, the poly(ether-amide)s described here compare fairly well with wholly aromatic polyamides when measured by dynamic TGA; but isothermal TGA measurements clearly demonstrated that they decompose faster than aromatic polyamides. Treatment of the TGA curves by the method of McCallum provided kinetic data that confirmed a better long-term stability for poly(ether-amide)s with a higher proportion of para-oriented phenylene rings. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:975–981, 1998 相似文献
6.
Shingo Hadano Seiji Maehara Kenjiro Onimura Hirohito Yamasaki Hiromori Tsutsumi Tutomu Oishi 《应用聚合物科学杂志》2004,92(4):2658-2664
Benzylated waste pulps (PBzs) were synthesized from treated waste pulp (Pulp), and benzyl chloride with phase transfer catalyst (PTC), and graft copolymers (PBz‐g‐LA) were synthesized from PBzs and L‐lactic acid (LA). Thermal properties, solubility, crystallinity, and biodegradability of the obtained PBzs and graft copolymers were investigated. PBzs with the degree of substitution (DS) higher than 1.5 showed Tg and Tm in DSC measurement. All PBz‐g‐LA exhibited no Tm. However, the graft copolymers obtained from lower DS PBzs having no Tg, exhibited Tg. The solubility of PBzs enhanced with increasing DS, and the crystallinity of PBzs reduced with increasing DS because of hydrophobicity and steric effect of benzyl groups. The solubility of graft copolymers was similar to that of original PBzs. Biodegradation tests for PBzs, Pulp, and graft copolymers were performed using cellulase in 0.1 M acetate buffer solution (pH 5.5) at 37°C. All samples showed biodegradability though the biodegradation rate decreased with increasing DS of PBz. In PBz‐g‐LA, the initial biodegradation rate was faster than that of original PBz because of hydrolysis of LA units. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2658–2664, 2004 相似文献
7.
Phan Trung Nghia Niti Siripitakchai Warunee Klinklai Takayuki Saito Yoshimasa Yamamoto Seiichi Kawahara 《应用聚合物科学杂志》2008,108(1):393-399
Reaction after mixing of liquid epoxidized natural rubber/poly(L ‐lactide) blend was performed to enhance the compatibility of the blend. The liquid epoxidized natural rubber was prepared by epoxidation of deproteinized natural rubber with peracetic acid in latex stage followed by depolymerization with peroxide and propanal. The resulting liquid deproteinized natural rubber having epoxy group (LEDPNR) was mixed with poly(L ‐lactide) (PLLA) to investigate the compatibility of the blend through differential scanning calorimetry, optical light microscopy, and NMR spectroscopy. After heating the blend at 473 K for 20 min, glass transition temperature (Tg) of LEDPNR in LEDPNR/PLLA blend increased from 251 to 259 K, while Tg and melting temperature (Tm) of PLLA decreased from 337 to 332 K and 450 to 445 K, respectively, suggesting that the compatibility of LEDPNR/ PLLA blend was enhanced by a reaction between the epoxy group of LEDPNR and the ester group of PLLA. The reaction was proved by high‐resolution solid‐state 13C NMR spectroscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
8.
Minoru Nagata Tsuyoshi Kiyotsukuri Susumu Minami Naoto Tsutsumi Wataru Sakai 《Polymer International》1996,39(2):83-89
Poly(ethylene terephthalate) copolymers were prepared by melt polycondensation of dimethyl terephthalate and excess ethylene glycol with 10–40mol% (in feed) of poly(ethylene glycol) (E) and poly(tetramethylene glycol) (B), with molecular weight (MW) of E and B 200–7500 and 1000, respectively. The reduced specific viscosity of copolymers increased with increasing MW and content of polyglycol comonomer. The temperature of melting (Tm), cold crystallization and glass transition (Tg) decreased with the copolymerization. Tm depression of copolymers suggested that the E series copolymers are the block type at higher content of the comonomer. Tg was decreased below room temperature by the copolymerization, which affected the crystallinity and the density of copolymer films. Water absorption increased with increasing content of comonomer, and the increase was much higher for E1000 series films than B1000 series films. The biodegradability was estimated by weight loss of copolymer films in buffer solution with and without a lipase at 37°C. The weight loss was enhanced a little by the presence of a lipase, and increased abruptly at higher comonomer content, which was correlated to the water absorption and the concentration of ester linkages between PET and PEG segments. The weight loss of B series films was much lower than that of E series films. The abrupt increase of the weight loss by alkaline hydrolysis is almost consistent with that by biodegradation. 相似文献
9.
A series of soy-based polyamides with different dimer acids and diamines were synthesized using a condensation polymerization technique. The molecular weight of polyamides prepared from 1,4-phenylenediamine increases greatly with a reaction temperature above 260°C. The physical properties of the polyamides, such as glass transition temperature (Tg), melting point (Tm), decomposition temperature (Td), crystalline behavior, and mechanical strength strongly depend on their molecular weight and flexibility of diamines used. The aromatic-based polyamides have a higher Tg, Tm, Td, and stronger mechanical strength than that of aliphatic-based polyamides. X-ray diffraction patterns of the samples indicate that all of the resins synthesized present a typical semicrystalline morphology. Polyamides made from hydrogenated dimer acid possess lower Tg and higher mechanical strength, compared with polyamides from unsaturated dimer acid with different dimer and trimer ratios. These results are analyzed and discussed in accordance with the influence of rigid aromatic segments and the microstructure of different dimer acids. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:305–314, 1998 相似文献
10.
Andrei Jitianu Guadalupe Gonzalez Lisa C. Klein 《Journal of the American Ceramic Society》2015,98(12):3673-3679
Melting gels are hybrid gels that have the ability to soften and flow at around 100°C for some combinations of mono‐ and di‐substituted alkoxysiloxanes, where substitutions are either all aromatic or all aliphatic. In this study, melting gels were prepared using phenyltriethoxysilane (PhTES) and dimethyldiethoxysilane (DMDES), meaning both an aromatic and aliphatic substitution. Differential scanning calorimetry was performed to identify glass‐transition temperatures, and thermal gravimetric analysis coupled with differential thermal analysis (TGA‐DTA) was performed to measure weight loss. The glass‐transition temperatures (Tg) ranged from ?61°C to +5.6°C, which are between the values in the methyl only system, where all Tg values are less than 0°C, and those values in the phenyl only system, where Tg values are greater than 0°C. The Tg decreased with an increase in the DMDES fraction. Below 450°C, the gels lost little weight, but around 600°C there was a drop in weight. This temperature is lower than the temperature for gels prepared with only aromatic substitutions, but higher than that for gels prepared with only aliphatic substitutions. Final heat treatment was carried out at 150°C for the gel with 80%PhTES‐20%DMDES (in mol%), and the consolidation temperature increased with increasing DMDES content to 205°C for the gel with 50%PhTES‐50%DMDES. After this heat treatment, the melting gels no longer soften. 相似文献
11.
Two series of samples, one of PET and another of PBT, were received after chain extension at different reaction times with two new chain extenders (diimidodiepoxides). These samples showed different intrinsic viscosity and degree of branching or crosslinking. The effect of this differentiation on thermal properties was studied by thermomechanical analysis (TMA). The parameters studied were the glass transition temperature (Tg), melting temperature (Tm), and the linear expansion coefficient (α). It is remarkable that in the case of PET amorphous or semicrystalline samples, two peaks appeared next to the Tg in the TMA thermogram. The first peak appeared at a temperature very close and lower to the Tg, and the other peak, at higher temperature into the “cold crystallization region.” The presence of two such peaks was not detected in the DSC thermogram of PET samples either in the TMS or DSC thermograms of PBT. The Tg values were found to agree to within ±1°C of those obtained from DSC; on the contrary, the Tm values varied significantly from those received from DSC. The linear expansion coefficient of samples was found to increase with the degree of chain extension. © 1996 John Wiley & Sons, Inc. 相似文献
12.
Ni(II)-α-diimine catalyst [(2,6-i-Pr)2C6H3-DAB(An)]NiBr2 plus methylaluminoxane was successfully used in the homopolymerization of ethylene, 1-hexene, and 1-octene and the copolymerization
of ethylene with 1-hexene and 1-octene in n-hexane. The polymerization of 1-octene was conducted in a controlled manner with a narrow molecular weight distribution (M
w/M
n = 1.2–1.5) and with the weight-average molecular weight increasing linearly with the monomer conversion. The molecular weights,
T
g, T
m, branching degree, and density of the obtained (co)polymers were greatly controlled by ethylene pressure and polymerization
temperature. Compared with that of ethylene homopolymer, the branching degree of the copolymers prepared by the copolymerization
of ethylene with 1-hexene or 1-octene increased, whereas the molecular weight, density, T
m, and catalyst activity decreased. However, compared with those of the homopolymer of 1-hexene or 1-octene, the copolymer
density, T
m, and catalyst activity increased, whereas the branching degree declined. 相似文献
13.
Styrene-acrylic acid copolymers exhibit miscibility with various aliphatic, crystalline polyamides (e.g., nylon 6, 11, and 12) at 20% acrylic acid content in the copolymer. At 8% acrylic acid, phase separation is observed with the crystalline polyamides. At 14% acrylic acid, partial miscibility is observed with each polyamide, resulting in the Tg's of the constituents shifted toward the other constituent. The miscibility of the styrene-acrylic acid copolymers ( > 14 wt % AA) can be ascribed to hydrogen bonding interactions with the polyamides. Styrene-acrylic acid (20% AA) copolymers are miscible with other nylons with alternating amide orientation along the chain (e.g., nylon 6,6 and nylon 6,9). These samples tend to crosslink upon exposure to temperatures above the polyamide melting point unlike the nylon 6, 11, and 12 blends in which branching may only occur. Nylon 11/styrene-acrylic acid blends were chosen for crystallization rate studies. A melting point depression of nylon 11 occurs with addition of the styrene-acrylic acid (20% AA). The Flory-Huggins interaction parameter from the melting point depression is calculated to be -0.27. The crystallization rate of nylon 11 is significantly reduced with the addition of the miscible SAA copolymers (20% AA). The spherulitic growth rate equation predicts this behavior based on a Tg increase with SAA addition. 相似文献
14.
Liuchun Zheng Chuncheng Li Dong Zhang Guohu Guan Yaonan Xiao Dujing Wang 《Polymer International》2011,60(4):666-675
In this exploration of novel biodegradable polyesters, multiblock copolymers based on poly(butylene succinate) (PBS) and poly(1,2‐propylene terephthalate) (PPT) were successfully synthesized with hexamethylene diisocyanate as a chain extender. The amorphous and rigid PPT segment was chosen to modify PBS. The structures of the polymers were characterized using 1H NMR and 13C NMR spectroscopy, gel permeation chromatography and wide‐angle X‐ray diffraction; the physical properties were investigated using thermogravimetric analysis, differential scanning calorimetry, mechanical testing and enzymatic degradation. The results indicate that the copolymers possess satisfactory mechanical and thermal properties, with impact strength 186% higher than that of PBS homopolymer, while tensile strength, flexural strength, thermal stability and melting point (Tm) are slightly decreased. Crystallization and biodegradation rates are still acceptable at 5 wt% PPT, although they are decreased by the introduction of PPT. The addition of appropriate amounts of PPT can improve the impact strength effectively without an obviously deleterious effect on tensile strength, flexural strength, thermal stability, Tm, crystallization rate and biodegradability. This study describes a convenient route to novel multiblock copolymers comprising crystallizable aliphatic and amorphous aromatic polyesters, which are promising for commercialization as biodegradable materials. Copyright © 2011 Society of Chemical Industry 相似文献
15.
Copolyesters containing poly(ethylene terephthalate) and poly(hexamethylene terephthalate) (PHT) were prepared by a melt condensation reaction. The copolymers were characterised by infrared spectroscopy and intrinsic viscosity measurements. The density of the copolyesters decreased with increasing percentage of PHT segments in the backbone. Glass transition temperatures (Tg). melting points (Tm) and crystallisation temperatures (Tc) were determined by differential scanning calorimetry. An increase in the percentage of PHT resulted in decrease in Tg, Tm and Tc. The as-prepared copolyesters were crystalline in nature and no exotherm indicative of cold crystallisation was observed. The relative thermal stability of the polymers was evaluated by dynamic thermogravimetry in a nitrogen atmosphere. An increase in percentage of PHT resulted in a decrease in initial decomposition temperature. The rate of crystallisation of the copolymers was studied by small angle light scattering. An increase in percentage of PHT resulted in an increase in the rate of crystallisation. 相似文献
16.
A series of graft polymers having polypropylene (PP) backbone and poly(ethylene‐co‐propylene) (EPR) side chains was prepared. PP backbone molecular weight (Mn) was 28–98 kg/mol, EPR side chain Mn was 2.6–17 kg/mol, and EPR content was 0–16 wt %. In this work, thermal analysis of the copolymers was performed using differential scanning calorimetry (DSC). Nonisothermal crystallization was performed at different cooling rates. The DSC thermograms revealed multiple melting peaks for slowly cooled samples, most likely the result of the melting of thinner tangential lamellae followed by the melting of thicker radial lamellae. Equilibrium melting temperature (Tm0) was determined using the linear Hoffman–Weeks method. Another approach was also used for determining Tm0: melting temperature (Tm) and crystallization temperature (Tc) were plotted as functions of logarithmic cooling rate. Linear relationships were observed for all samples with the cross points as Tm0's. As cooling rate decreased, Tc, Tm, and enthalpy of fusion (ΔHf) increased. Tm and Tm0 increased with increasing PP Mn. Tc and Tm were unaffected by the grafting of EPR onto the PP backbone. Tm0 and ΔHf decreased as EPR content increased. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3380–3388, 2006 相似文献
17.
Different routes for preparing poly(aryl ether ketone)s (PEKKs) are presented and compared. The properties of PEKKs are related to the content of metaphenyl links in the molecular main chains, the molecular chain branching degree, the gelation content by molecular crosslinks, and, especially, the relative content of crystal form II to crystal form I of the PEKK polymorphism. When the molecular T/I ratio of 50/50 in the polymer chains is reached, the obtained PEKK has a lower melting point and gelation content (2% or so). The PEKKs prepared from the electronical substitution route (E route) often have a 0–30% content of crystal form II (relative to the mixed form I and form II), which is much more than that in PEKKs from the nucleophilic substitution route (N route, form II accounts for 0–20%). The relatively unstable crystal form II resulted in the unstable and difficultly predicted thermal properties of PEKKs. PEKKs from different routes provide samples with melting points from 360 to 397°C (Tm) and glassy transition temperatures (Tg) from 167 to 176°C and the equilibrium melting point of 411°C for para-PEKK, while the tensile strength of the homopolymer PEKK and copolymers of PEEKK (poly(aryl ether ether ketone ketone)–PEKK can reach 100 MPa prepared by the N route. The high Tg makes PEKK polymers practically useful while too high Tm and a very small difference between Tm and Td (degradation temperature) produce obstacles to its wide application. The reaction mechanisms of both electrophilic and nucleophilic routes are investigated and discussed in detail. Results show that the molecular chain branched by solvents and monomers with many activated points may be partly reduced to some extent by the oligomer and extruding route. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 659–677, 1998 相似文献
18.
Poly(phenylene sulfide) (PPS) made via the melt polymerization of p-diiodobenzene and sulfur has previously been reported to increase in melt viscosity with time during rheological testing. Analysis of the oligomer from cleavage of PPS chains at the disulfide bonds via solution in 1-chloronaphthalene demonstrated that the disulfide content of the polymer decreased with rheological testing time. DSC of the polymer before and after rheological testing in combination with the Tcc and Tm of the chain fragments after the dissolution/cleavage in 1-chloronaphthalene showed that many samples exhibited primarily chain extension rather than chain branching, whereas for many others, some degree of chain branching occurred. This is currently only qualitatively understood. Chain branching as the exclusive mechanism of melt viscosity increase during rheological testing appears untenable in light of the Tm, in particular, of the chain fragments and also the polymer prior to chain cleavage. © 1993 John Wiley & Sons, Inc. 相似文献
19.
The plasticizing effect of benzenesulfonamides (BSAs) on an amorphous aliphatic polyamide (AAPA) has been studied using dynamic mechanical analysis of copper‐supported spin‐coated mixtures. It follows that N‐(n‐butyl)BSA (BBSA), an amorphous liquid hydrogen bonding BSA, is fully miscible with AAPA because their mixtures are characterized by a single glass transition (Tg) throughout the compositional range. The Tg–composition dependence, however, is not linear because experimental results suggest a 20 K fall in Tg occurring around 0.65 BBSA units per amide unit, which coincides with the system shifting from a polymer‐like to a liquid‐like glass‐forming material. When considering a crystallizable hydrogen‐bonding plasticizer such as ethylBSA (EBSA), AAPA/EBSA mixtures become fully crystalline at a 1.3 EBSA unit per amide group. Nevertheless, melting point depression together with the single Tg observed throughout the compositional range on quenched (and therefore amorphous) samples confirms the miscibility of AAPA chains with the plasticizer. N,N‐DialkylBSAs, which lack the sulfonamide proton and therefore the possibility of hydrogen bonding with amide groups, quickly phase separate from AAPA, the glass transition of the latter staying mainly unaffected apart from a small (9 K) decrease at 10–15 mol% plasticizer. © 2001 Society of Chemical Industry 相似文献
20.
Ching-hsien Huang 《Lipids》2001,36(10):1077-1097
It has long been established that diacyl phospholipids isolated from animal cell membranes are predominantly of a mixed-chain
variety, meaning that the sn-1 and sn-2 acyl chains are saturated and unsaturated acyl chains, respectively. In general, monoenoic and dienoic acids are found
in the sn-2 acyl chain of phosphatidylcholine (PtdCho), whereas polyenoic acids are in phosphatidylethanolamine (PtdEth). These unsaturated
chains contain only cis-double bonds, which are always methylene-interrupted. In recent years, the structures and the chain-melting behavior of mixed-chain
PtdCho and PtdEth have been systematically studied in this laboratory. Specifically, we have examined the effects of chain
unsaturation of the sn-2 acyl chain on the phase transition temperature (Tm) of many PtdCho and PtdEth by high-resolution differential scanning calorimetry (DSC). The Tm values, for instance, obtained from all-unsaturated mixed-chain PtdEth derived from a common precursor can be grouped together
according to their chemical formula to form a Tm-diagram. Hence, all the Tm values can be compared simply, systematically, and simultaneously using the Tm-diagram. In addition, the energy-minimized structures of mixed-chain phospholipids containing different numbers/positions
of methylene-interruped cis-double bonds have been simulated by molecular mechanics calculations (MM). In this review, the results of our MM and DSC
studies carried out with various mixed-chain phospholipids are summarized. In addition, we emphasize that the combined approach
of MM and DSC yields unique uniformation that can correlate the various Tm-profiles seen in the Tm-diagram with the structural variation of mixed-chain lipids as caused by the introduction of different numbers/positions
of methylene-interrupted cis-double bonds. 相似文献