Structure–property relationship in copolymers of methacrylic acid esters. I. Thermal behavior

This article describes the synthesis and thermal characterization of copolymers of methyl methacrylate (MMA) and alkyl methacrylates. The copolymerization was carried out using different mol fractions (0.05–0.25) of alkyl methacrylates, i.e., octyl methacrylate (OMA)/decyl methacrylate (DMA)/lauryl methacrylate (LMA)/stearyl methacrylate (SMA), in the initial feed at 80°C. The copolymer composition was determined from ¹H-NMR. The thermal stability of the copolymers was investigated by thermogravimetric analysis and pyrolysis gas chromatography. A two/three-step degradation was observed in the copolymer samples. The monomers were the major product of degradation in most of the copolymers except in SMA/MMA copolymers where the product of side-group elimination was also observed. An attempt was also made to determine the yield of the monomers during degradation and then to evaluate the copolymer composition. © 1994 John Wiley & Sons, Inc.     

马来酸酐接枝改性氯化聚氯乙烯的制备及其在PVC中的应用

采用固相法制备马来酸酐接枝氯化聚氯乙烯(CPVC-g-MAH),得到了接枝率达2.91 %的CPVC-g-MAH,并对其进行了性能测试,探讨了聚氯乙烯(PVC)/CPVC-g-MAH共混物的冲击性能和加工性能,与PVC/氯化聚氯乙烯(CPVC)共混物进行对比以观察改性效果。结果表明,CPVC-g-MAH的热性能较CPVC有较大提高;PVC/CPVC-g-MAH共混物的冲击性能比PVC/CPVC共混物有所提高,而平衡转矩有所降低,说明CPVC-g-MAH相比于CPVC对PVC共混物加工性能改善效果更加明显。     

聚(对苯二甲酸-1,3-丁二醇酯/对苯二甲酸-1,4-丁二醇酯)/PEG嵌段共聚物的合成及性能研究

用熔融缩聚法合成了一系列聚(对苯二甲酸-1,3-丁二醇酯/对苯二甲酸-1,4-丁二醇酯)/聚乙二醇的嵌段共聚物。用FT-IR,1H-NMR,DSC,TGA,水降解测试等方法表征了材料的结构与性能。FT-IR和1H-NMR分析表明合成得到的共聚物为预期产物;DSC分析显示,共聚聚酯随着1,3-丁二醇在共聚物中比例的增大,熔点(Tm)逐渐降低,由158.24℃下降至104.19℃,玻璃化温度(Tg)逐渐升高,由4.86℃升至24.56℃,合成得到的共聚酯趋向于无定形态;TGA分析表明1,3-丁二醇在共聚酯中比例增大会使聚酯的热稳定性下降,但合成得到的共聚酯依然具有较好的热稳定性,初始分解温度大于310℃,不需要在反应过程中添加热稳定剂;水降解测试结果表明共聚物随1,3-丁二醇比例的增加,降解速率大幅提升。     

Copolymerizations of tetrafluoroethylene and perfluoropropylvinyl ether in supercritical carbon dioxide: Polymer synthesis,characterization, and thermal properties

Tetrafluoroethylene (TFE) and perfluoropropylvinyl ether (PPVE) were copolymerized in supercritical carbon dioxide (sc‐CO₂) with a perfluorodiacyl initiator bis(perfluoro‐2‐n‐propoxypropionyl) peroxide (BPPP). The resultant copolymers with stable perfluoroalkyl end groups were obtained, avoiding the decomposition during processing and applications. Reactivity ratios of TFE and PPVE were first reported. The r_TFE and r_PPVE values are about 8 and 0.08, respectively. Such parameters are significant for the modification of PTFE through copolymerization of TFE and PPVE. It is found that through increasing the reaction pressure from 8.5 to 25 MPa, while r_TFE increases by 12.0%, r_PPVE decreases by 9.0%, which should be ascribed to the enhancement of the polarity of CO₂ under high pressures. Because the reactivity of TFE is by two orders of magnitude higher than that of PPVE; on one hand, the copolymerization rate falls rapidly with the decrease of TFE feed ratio; on the other hand, TFE content in the copolymer decreases with the reaction time. All copolymers containing different fractions of PPVE enjoy outstanding thermal stability. The DSC result indicates that there exist two forms of crystals with highly regular molecular arrangement or less ordered chain packing which is disturbed by perfluoropropyl pendants. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Degradation kinetics of acrylonitrile/methyl vinyl ketone copolymers

Methyl vinyl ketone (MVK) was first used to successfully copolymerize with acrylonitrile (AN). This was achieved by using azobisisobutyronitrile as the initiator. Differential scanning calorimetry results of the degradation of AN/MVK copolymers in air are presented. The apparent activation energy of degradation of the copolymers was calculated with Kissinger method. Effects of copolymerization conditions on the apparent activation energy of the copolymers were studied. It has been found that increasing dimethyl sulfoxide concentration in the solvent mixture leads to a rapid increase in the degradation apparent activation energy of AN/MVK copolymers. The apparent activation energy decreases quickly along with increase in the comononer MVK concentration, and this change becomes less prominent as the weight ratio of MVK/AN goes beyond 7/93. The apparent activation energy shows a trend of increase as the copolymerization temperature increases. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1386–1390, 2007     

Thermal analysis of solution copolymers of styrene with N‐phenylmaleimide

Free‐radical–initiated copolymerization of N‐phenylmaleimide (NPMI) with styrene (St) at 110°C in a toluene solution initiated by AIBN was carried out by a semibatch method. The compositions of the copolymers were determined by using an elemental analyzer. The glass‐transition temperatures of the copolymers were measured by differential scanning calorimetry. All the semibatch copolymers show a single glass‐transition temperature that increases markedly with increasing NPMI content in the copolymers. The thermal stabilities of the copolymers were studied by using a programmed thermogravimetric analysis technique. Copolymers show a considerable increase in thermal stability and different degradation reaction mechanisms with increasing content of NPMI. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 417–422, 2002     

Thermal behavior of cellulosic graft copolymers. II. Cotton grafted with binary mixtures of vinyl acetate and methyl acrylate

Thermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate-methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate-methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate-methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.     

Thermal stability and dynamic mechanical properties of acetal copolymers

By copolymerization of trioxane with 1,3-dioxacycloheptane (DOCH) or 1,3-dioxacyclooctane (DOCO) acetal copolymers were synthesized with comonomer units which, in contrast to customary 1,3-dioxolane/trioxane copolymers, consist of sequences with four or five methylene groups, respectively. In comparison with 1,3-dioxolane/trioxane copolymers these copolymers show a significantly higher thermal stability due to the larger sequences of thermically stable C—C-bonds. Torsion pendulum measurements show that the difference of the comonomer nature influences the storage modulus, G′, which is a measure for the rigidity of the material, and the loss tangent tan δ. Obviously, G′ is dependent on the crystallinity of the sample, which again is influenced by the kind and concentration of the incorporated comonomer. Also the peak locations of the α- and γ-relaxation indicate a direct connection to the comonomer nature and content in the different copolymers. The α-maxima are shifted to lower temperatures with increasing number of methylene groups as well as with growing comonomer content. However, the γ-maxima appear at higher temperatures with increasing comonomer content, but at lower temperatures with growing length of the comonomer unit. Additionally, branched acetal copolymers were synthesized by using comonomers in which the hydrogen atom at the 4-position of 1,3-dioxolane has been substituted by alkyl groups of different length (methyl to tetradecyl). In these copolymers the nature of comonomer neither improves the thermal stability of the copolymers nor influences the α- and γ-relaxation.     

Halogen-induced chemical copolymerization of pyrrole with N-methylpyrrole

Simultaneous chemical copolymerization and oxidation of pyrrole and N-methylpyrrole by bromine an iodine has been carried out. The composition of the copolymes can be effectvely controlled by varying the monomer feed ratio. From elemental analysis the copolymer composition and the monomer reactivity ratios have been determined. As the copolymer composition changes, the IR absorption spectra show changes in the intensity of certain bands. In bromineinduced polymerization, the electrical conductivity, the electrical conductivity, thermal stability, and bromine content of the copolymer complex decrease with increase in N-mthylpyrrole fraction. X-ray photoelectron spectroscopy data suggest that a fixed fraction of bromine is incroporated as covalent bromide in the copolymer complex. When iodine is used the halogen content do not show substantial differences among the copolymers but the electricdal conductivity and thermal stability of the copolymers also decrease with increase in N-methylpyrrole fraction.     

硅烷交联聚氯乙烯的制备和性能

对由悬浮共聚合成的氯乙烯／乙烯基三乙氧基硅烷共聚树脂的水解交联行为和交联聚氯乙烯的性能进行了研究。结果发现，通过聚合过程添加pH调节剂可得到凝胶含量很低的氯乙烯／乙烯基三乙氧基硅烷共聚树脂；该类共聚树脂加工后有一定程度交联发生，凝胶含量随共聚树脂中乙烯基三乙氧基硅烷含量增加而增加；当加工样品在水中浸渍后凝胶含量又有较大幅度提高，说明水解交联的发生；交联后PVC高温力学性能和耐热变形性提高。     

Preparation and characterization of copolymers from methyl methacrylate and cardanyl methacrylate

Copolymers of methyl methacrylate (MMA) and cardanyl methacrylate (CMA) were synthesized, characterized and their physico-mechanical properties were investigated. The benzoyl peroxide-initiated copolymerization was carried out by using different mole fractions of CMA (0.02–0.10) in the initial feed at 80°C. Structural characterization of copolymers was done using FTIR and ¹H NMR spectroscopic techniques. The thermal stability of the copolymers was evaluated using dynamic thermogravimetry. Incorporation of CMA in the MMA backbone leads to an improvement in thermal stability.     

Synthesis of random and block copolymers of vinyl chloride and vinyl acetate by RAFT miniemulsion polymerizations mediated by a fluorinated xanthate

Reversible addition–fragmentation chain transfer miniemulsion (co)polymerizations of vinyl acetate (VAc) and vinyl chloride (VC) are conducted in the presence of a fluorinated xthanate (X1). VAc miniemulsion polymerization can be well controlled by X1, and PVAc with small polydispersity index (PDI, <1.20) are obtained. X1 also shows well mediative effect to VC‐VAc miniemulsion copolymerization, while the PDI of VC‐VAc copolymer is greater than that of PVAc since a chain transfer rate to VC is greater than that to VAc. PVAc‐b‐PVC copolymers are synthesized by VC miniemulsion polymerizations mediated by X1‐terminated PVAc. PDIs of PVAc‐b‐PVC copolymers are greater than that of PVAc and VC‐VAc random copolymers with close monomer compositions, and increase with the increase of VC conversion. This is caused by the increased chain transfer to monomer and the formation of monomer‐rich and polymer‐rich phases during the VC polymerization stage. As‐prepared PVAc‐b‐PVC copolymers exhibit a micro‐phase separated morphology. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45074.     

Effect of copolymers modifying PVC on its physical and mechanical properties and its UV-radiation resistance. III. Changes in thermal stability of PVC films modified by MMA/MA,VC/VAC,MBS or ABS induced by UV-irradiation

The influence of UV-radiation on thermal stability of PVC films, depending on the type and quantity of modifying copolymers, was studied. It was found that UV radiation can induce various changes in thermal stability of PVC decreasing its dehydrochlorination temperature T⁰₁ while increasing temperature of decomposition T⁰₂. Particularly distinct changes in sampels containing VC/VAC indicate that even 1% of this copolymer accelerates the photodehydrochlorination and the processes which decrease the temperature of decomposition of PVC. Smaller changes than in pure PVC in thermal parameters in samples containing ABS after irradiation show that this copolymer increases the PVC resistance to UV radiation. Films containing MBS, ABS, MMA/MA reveal the largest changes in T⁰₁ after irradiation in the case of a content of 1% of these copolymers in the samples. In the case of bigger quantity (3 to 10%) the changes are smaller and may even diversify their direction. These copolymers, contrary to VC/VAC, make PVC films a little turbid indicating the limited compatibility of both components. Hence, the conclution is that the structure of a film, depending on compatibility of components and changing with their differing concentration, has decisive influence on the thermal and photochemical processes.     

Polyblends of poly(vinyl chloride) with ethylene/vinyl acetate copolymers: Practical properties and morphology

Five to 15 percent of ethylene/vinyl acetate copolymers was compounded into rigid polyvinyl chloride, with the copolymers dispersed as discrete micro-domains, produced very efficient synergistic improvement of impact strength; as the vinyl acetate content of the copolymer increased from 28 to 60 percent, the synergistic peak moved to higher copolymer content and became higher and broader. Copolymer content correlated directly with melt flow and thermal stability, and inversely to modulus, strength, and heat-deflection temperature. The vinyl acetate content of the copolymer correlated directly with elongation, impact strength, and thermal stability, but inversely to modulus, heat-deflection temperature, low-temperature flexibility, and melt flow. When the copolymer content reached 25 percent, it formed a second continuous-phase, interpenetrating the polymer network structure and acting as a polymeric plasticizer, producing thermoplastic elastoplastics.     

Hydrogels based on N-isopropylacrylamide and methacrylic acid: thermal stability and glass transition behaviour

Summary The thermal stability and glass transition behaviour of crosslinked poly(N-isopropylacrylamide) [P(N-iPAAm)], poly(methacrylic acid) [P(MAA)], their random copolymers and sequential interpenetrating polymer networks (IPNs) have been investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). P(MAA) shows a two-step process of degradation. P(N-iPAAm) shows an unique process of degradation at higher temperature. Copolymers having higher content in N-iPAAm units have a lower thermal stability than their component homopolymers and show an unique degradation process at high temperature. On the contrary, enriched MAA copolymers show better stability but they exhibit two degradation steps at the main degradation region. Sequential IPN samples exhibit a better stability than their component homopolymers and copolymers. The high temperature backbone degradation occurs in only one step, which indicates the formation of a true interpenetrating network. The T _g of the same series of materials has been also measured. A T _g vs composition plot of P(N-iPAAm-co-MAA) copolymers presents a S-shaped curve indicating that structural units interact among them through strong specific interactions. For interpenetrating polymer networks, it seems that only one T _g occurs indicating a good compatibility and interpenetration. Received: 1 December 2001 /Revised version: 12 February 2002/ Accepted: 12 February 2002     

Strain-induced crystallization kinetics of vinylidene chloride/vinyl chloride (VDC/VC) copolymers

The strain-induced crystallization (SIC) behavior of VDC/VC copolymers has a significant effect on processibility on the blown film process. However, data on SIC of VCD/VC copolymers has been very limited due to the difficulty of measuring the rapid crystallization rates induced by strain; whereas, crystallization under quiescent conditions has been studied extensively. In this work, SIC of VDC/VC copolymers has been calculated from measurements of the adiabatic temperature rise upon stretching of amorphous specimens. The effect of stretching conditions such as strain rate, total strain, and initial temperature and the effect of polymer variables such as copolymer composition, molecular weight, and plasticizer content are determined. It is found that the performance of different VDC/VC copolymers on the film-blowing process correlates much better with measurements of SIC than with quiescent crystallization behavior.     

Preparation and thermal and thermo‐oxidative stability of vinylidene chloride‐co‐vinyl chloride copolymer/synthetic hectorite nanocomposites

Poly(vinylidene chloride‐co‐vinylchloride)/organically modified hectorite (VDC‐VC/SPN) nanocomposites were prepared by melt blending VDC‐VC copolymer with SPN in the presence of dioctyl phthalate, which acted as a plasticizer. As a result, the exfoliated structure was found in the VDC‐VC/SPN nanocomposites. In nitrogen atmosphere, VDC‐VC/SPN nanocomposites exhibited a single‐step thermal degradation. The thermal stability of VDC‐VC/SPN nanocomposites is significantly influenced by the SPN, which was modified with long alkyl ternary ammonium salt. In air atmosphere, VDC‐VC/SPN nanocomposites revealed a two‐step thermo‐oxidative degradation behavior. At the first degradation stage, the weight loss pattern is similar to that of VDC‐VC composites in nitrogen, in which the thermo‐oxidative stability of VDC‐VC/SPN nanocomposites is affected by the ternary ammonium salt and oxygen rather than its morphology. At the second degradation stage, both the enhanced thermo‐oxidative stability and the flame‐retardation ability of VDC‐VC composites are strongly and closely related to the morphology of nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci ,2009     

Localized radiation grafting of flame retardants to poly(ethylene terephthalate). I. Bromine-containing monomers

Vinyl bromide was used as a model for bromine-containing flame retardants in developing methodology for localizing flame retardants either on the surface of the filament, uniformly throughout it, or predominantly at the core. SEM–x-ray microprobe techniques were used in the verification of the location of the flame retardant in the filament. The flame retardance efficiency of PVBr was then correlated with its location in the filament. Grafting other bromine-containing flame retardants showed a wide range of efficiencies which depended not only upon the location of the grafting within the filament but also upon the structure of the compound. For the various bromine homopolymer grafts, the apparent thermal stability of the graft and its flame retardance efficiency may be simply related to the alpha aliphatic hydrogen-to-bromine ratio. The lower this ratio is, the higher the efficiency. VBr copolymers and terpolymers showed wider variation in flame retardance efficiencies. This is attributed to large variations in melt viscosity of the different grafted materials. The grafts showed only small changes in their melting points and minimal changes in tenacity and stiffness. However, grafting induced large increases in the elongation.     

PA6T/1010共聚物热性能研究

以对苯二甲酸、己二胺和癸二酸、癸二胺为原料合成了新型半芳香PA6T/1010共聚物,通过差示扫描量热仪(DSC)、熔点测定仪和热重分析仪(TG)对不同组成PA6T/1010的熔融行为、结晶行为和热稳定性进行了表征。结果表明:当PA6T含量大于40%时,PA6T/1010共聚物的结晶性能明显下降,熔融峰和结晶峰均消失;当PA6T含量为40%时,共聚物共熔点降至165℃;PA6T/1010共聚物的热降解过程为一步降解,热降解温度超过400℃。     

Studies on tributyl tin methacrylate (TBTM). VI. Thermal and tensile behavior of copolymer of tri-n-butyl tin methacrylate and methyl methacrylate

The thermal and tensile properties of polytributyl tin methacrylate (PTBTM) and n-tributyl tin methacrylate–methyl methacrylate (TBTM—MMA) copolymers have been studied. Thermogravimetric study showed that with increasing the TBTM content in the copolymer the thermal stability decreases. The glass transition temperature (T_g) decreases continuously as the TBTM content increases. All the polymers showed multistep decomposition. MS study showed that in addition to monomer formation several other side reactions also take place during degradation, leading to formation of other products. Studies on tensile properties show that the tensile strength decreases with increasing TBTM content, whereas elongation at break increases. © 1992 John Wiley & Sons, Inc.