Quantitative study of the annealing of poly(vinyl chloride) near the glass transition

Poly(vinyl chloride) displays a normal DSC of DTA curve for the glass transition when quenched from above its T_g. However if cooled slowly or annealed near the glass transition temperature, a peak appears on the DSC or DTA curve at the T_g. In this paper quantitative studies of the time and temperature effects on the production of this endothermal peak during the annealing of PVC homopolymer and an acetate copolymer are presented. The phenomenon conforms to the Williams, Landell, and Ferry equation for the relaxation of polymer chains, the rate of the peak formation becoming negligible at more than 50°C below T_g. The energy difference between the quenched and annealed forms is small. For a PVC homopolymer annealed 2 hr at 68°C, which is T_g ?10°C, the difference is 0.25 cal/g. For a 13% acetate copolymer of PVC similarly annealed, the difference is 0.36 cal/g. The measured rates of the process give a calculated activation energy of 13–14 kcal/mole for PVC homopolymer and copolymer. This appearance of a peak on the T_g curve for a polymer when annealed near the glass temperature appears to be a general phenomenon.     

The effect of composition on the properties of nylon 612 copolymers

The series of nylon 612 copolymers was synthesized from caprolactam (C) and laurolactam (L) at 145°C. The 50/50 C/L molar ratio copolymer was found to have the minimum melting temperature (T_m ) for the series. The glass transition temperatures (T_g 's) of the copolymers were affected by the crystallinity of the copolymers. The T_g was at a minimum for the 50/50 copolymer for crystalline samples. However, for amorphous samples there was a decrease in T_g with increasing L content. Percent crystallinity was determined by differential scanning calorimetry and X-ray techniques. It was found that the degree of crystallinity was at a minimum for copolymers of 70/30 to 40/60 C/L ratios. Coefficients of linear thermal expansion (CLTE) were obtained for the copolymers at 10°C intervals from 20 to 70°C for dry and from 20 to 50°C for samples conditioned at 50% relative humidity and 50°C. The dry samples gave lower initial values, but had a greater temperature dependence than the conditioned samples. As expected, the CLTE was found to be lowest for samples exhibiting the highest crystallinity. The tensile strengths and moduli decreased rapidly with increasing L up to the 70/30 C/L ratio after which they remained relatively constant. Elongations reached maximums between 70/30 and 40/60 C/L ratios. An inverse relationship was found between crystallinity and impact strength.     

Design of polymers for migration imaging application II: Synthesis and polymerisation of p-isobutyl styrene

A copolymer series was synthesized for migration imaging applications from isobutyl methacrylate and isobutyl styrene such that each homopolymer and all copolymers had glass transition temperature (T_g) near 55°C. The T_g of poly (p-isobutylstyrene) was predicted from literature values of similar polymers to be near 55°C. Poly (p-isobutylstyrene) was synthesised by acetylation of isobutyl benzene, reduction of p-isobutylacetoph-enone to the carbinol, dehydration to p-isobutylstyrene and free radical polymerisation to the polymer. The T_g of the homopolymer was 55°C, in excellent agreement with the predicted value. Copolymers of isobutyl methacrylate and p-isobutyl styrene were synthesised and their T_g's measured across the series by DSC (57°C ± 5°C). refractive index temperature coefficient (42°C ± 5°C). The copolymer series was also characterised by melt viscosity measurements.     

Lignin valorization by forming toughened thermally stimulated shape memory copolymeric elastomers: Evaluation of different fractionated industrial lignins

Lignin‐based thermal responsive dual shape memory copolymeric elastomers were prepared with a highly branched prepolymer (HBP, A₂B₃ type) via a simple one‐pot bulk polycondensation reaction. The effect of fractionated lignin type (with good miscibility in the HBP) on copolymer properties was investigated. The thermal and mechanical properties of the copolymers were characterized by DMA, DSC, and TGA. Tensile properties were dominated by HBP <45% lignin content while lignin dominated >45% content. The copolymers glass transition temperature (T_g) increased with lignin content and lignin type did not play a significant role. Thermally stimulated dual shape memory effects (SME) of the copolymers were quantified by cyclic thermomechanical tests. All copolymers had shape fixity rate >95% and >90% shape recovery for all compositions. The copolymer shape memory transition temperature (T_trans) increased with lignin content and T_trans was 20°C higher than T_g. Lignin, a renewable resource, can be used as a netpoint segment in polymer systems with SME behavior. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41389.     

Preparation of poly(styrene‐co‐isobornyl methacrylate) beads having controlled glass transition temperature by suspension polymerization

The styrene (St) and isobornyl methacrylate (IBMA) random copolymer beads with controlled glass transition temperature (T_g), in the range of 105–158°C, were successfully prepared by suspension polymerization. The influence of the ratios of IBMA in monomer feeds on the copolymerization yields, the molecular weights and molecular weight distributions of the produced copolymers, the copolymer compositions and the T_gs of these copolymers was investigated systematically. The monomer reactivity ratios were r₁ (St) = 0.57 and r₂ (IBMA) = 0.20 with benzyl peroxide as initiator at 90°C, respectively. As the mass fraction of IBMA in monomer feeds was about 40 wt %, it was observed that the monomer conversion could be up to 90 wt %. The fractions of IBMA unit in copolymers were in the range of 35–40 wt % and T_gs of the corresponding copolymers were in the range of 119.6–128°C while the monomer conversion increased from 0 to greater than 90 wt %. In addition, the effects of other factors, such as the dispersants, polymerization time and the initiator concentration on the copolymerization were also discussed. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A new class of transparent polymeric materials. II. Synthesis and properties of poly(N-cyclohexylmaleimide-alt-isobutene) modified with lauryl methacrylate

Transparent polymeric materials with high heat resistance and low water absorption were designed based on the alternating copolymers of N-substituted maleimide (RMI) with isobutene (IB). The N-substituent of the maleimide significantly affected the glass transition temperature (T_g) and water absorption of the copolymers. Poly(N-cyclohexylmaleimide-alt-JB) [poly(CHMI-IB)] showed a T_g value as high as 192°C and relatively low water absorption. Furthermore, the incorporation of a small amount of lauryl methacrylate in the copolymers was confirmed to reduce the water absorption of the copolymer drastically, although it decreased the T_g of the copolymers at the same time. Poly(CHMI-IB), containing 4 mol % lauryl methacrylate, showed a good balance of excellent transparency, high heat resistance, acceptable mechanical properties, and low water absorption. The heat deflection temperature was as high as 141°C. The water absorption at 23°C after immersion for 14 days was 0.56% and the dimensional change after 7 days was 0.06%. They are half and one-quarter of those of poly(methyl methacrylate), respectively. © 1996 John Wiley & Sons, Inc.     

Stimuli sensitive copolymer poly(N‐tert‐butylacrylamide‐ran‐acrylamide): Synthesis and characterization

Temperature sensitive random linear and crosslinked copolymers of N‐tert‐butylacrylamide (NTBA) and acrylamide (Am) were synthesized by the solution polymerization method, using regulated dosing of comonomer Am having a higher reactivity ratio (r_Am = 1.5) than NTBA (r_NTBA = 0.5). Copolymers with varying feed ratios of NTBA and Am (80 : 20 to 20 : 80 mol %) were synthesized and characterized. For the synthesis of copolymer hydrogels, N′, N‐methylene bisacrylamide (MBA) (1.13 mol %) was used along with monomers. The effect of composition on transition properties was evaluated for the linear copolymers and their hydrogels. A definite trend was observed. The incorporation of a higher percentage of the hydrophilic comonomer Am in the structure resulted in the shifting of the transition temperature towards a higher value. The transition temperatures of the copolymers synthesized with feed compositions of 80 : 20, 70 : 30, 60 : 40, 50 : 50, 40 : 60, 30 : 70, and 20 : 80 mol % were found to be 2, 10, 19, 27, 37, 45, and 58°C, respectively. Differential scanning calorimetry (DSC) studies confirmed the formation of random copolymers. The copolymers synthesized with a monomer feed ratio of 50 : 50 with regulated dosing showed a single glass transition temperature (T_g) at 168°C, while the copolymer synthesized with full dosing of Am at the beginning of the reaction showed two T_gs, at 134 and 189°C. The copolymer samples were analyzed by Fourier transform infrared spectroscopy (FTIR) for ascertaining the composition. The composition of the copolymers followed the trend of the feed ratio, but the incorporation of NTBA in the copolymers was found to be lower than the feed ratio because of lower than quantitative yields of the reactions. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 672–680, 2005     

Thermal and gas permeation properties of copolymers derived from 3‐methacryloxypropyltris(trimethylsiloxy)silane and adamantyl group‐containing methacrylate derivatives

Novel copolymer membranes derived from three types of adamantyl group‐containing methacrylate derivatives and 3‐methacryloxypropyltris(trimethylsiloxy)silane (SiMA) were synthesized via free radical polymerization. The thermal and permeation properties of these copolymer membranes were investigated. Copolymer membranes with less than 11.9 mol % adamantane content exhibited good membrane forming abilities that are suitable for permeation measurement. The decomposition temperature of all copolymers increased up to approximately 40–80°C with increasing adamantane content compared with poly(SiMA). Moreover, the glass transition temperature (T_g) of all copolymers increased up to approximately 46–60°C with increasing adamantane content compared with the theoretical value, which was estimated from Fox equation. 1‐Adamantyl methacrylate copolymer had the highest fractional free volume among the three types of adamantly group‐containing methacrylate derivatives. The gas permeability coefficient of this copolymer increased by 22–45% with increasing adamantane content compared with that of poly(SiMA). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43129.     

In situ compatibilization of low-density polyethylene and polydimethylsiloxane rubber blends using ethylene–methyl acrylate copolymer as a chemical compatibilizer

The effect of the ethylene–methylacrylate copolymer as a chemical compatibilizer in the 50:50 blend of low-density polyethylene (LDPE) and polydimethylsiloxane rubber (PDMS) has been studied in detail. Ethylene–methylacrylate (EMA) reacted with PDMS rubber during melt-mixing at 180°C to form EMA-grafted PDMS rubber (EMA-g-PDMS) in situ, which acted as a compatibilizer in the LDPE–PDMS rubber blend. An optimum proportion of the compatibilizer (EMA) was found to be 6 wt % based on results of dynamic mechanical analysis, adhesion studies, and phase morphology. Lap shear adhesion between the phases increased significantly on incorporation of 6 wt % of EMA. Dynamic mechanical analysis showed a single glass transition (T_g) peak at ?119°C. This was further supported by X-ray diffraction studies, which exhibited a remarkable increase in the degree of crystallinity and phase morphology and showed a drastic reduction in the size of the dispersed phase at the optimum concentration of EMA. © 1993 John Wiley & Sons, Inc.     

Characterization of N,N-dimethylacrylamide/2-methoxyethylacrylate copolymers and phase behaviour of their thermotropic aqueous solutions

Dimethylacrylamide (DMA) has been copolymerized with 2-methoxyethylacrylate (MOEA) and solutions of the products were analysed by FTIR to yield derived reactivity ratios r_DMA = 1.11 ± 0.13 and r_MOEA = 0.63 + 0.10. The measured glass transition temperatures T_g of PDMA and PMOEA were 395 K, and 242 K, respectively. These and the values of T_g for the copolymers accorded well with the Fox relationship. Cloud point curves for copolymers in water were established over a wide range of concentration, solubility decreasing with increase in temperature. For these reversibly thermotropic solutions, the lower critical solution temperature (LCST) increased from 9°C to 80°C with decrease in content of MOEA in the copolymer from 91.1 mol% to 38.6 mol%.     

Melt polymerization of copoly(ethylene terephthalate–imide)s and thermal properties

Copoly(ethylene terephthalate–imide)s (PETI) were prepared by melt polycondensation of bis(2-hydroxyethyl)terephthalate (BHET) and imide containing oligomer, i.e., 4,4′-bis[(4-carbo-2-hydroxyethoxy)phthalimido]diphenylmethane(BHEI). The apparent rate of poly-condensation reaction was faster than that of homo poly(ethylene terephthalate) (PET) due to the presence of imide units. The PETI copolymers with up to 10 mol % of BHEI unit in the copolymer showed about the same molecular weight and carboxyl end group content as homo PET prepared under similar reaction conditions. The increase in T_g of copolymer was more dependent on molar substitution of BHEI than on substitution of BHEN, reaching 91°C with 8 mol % BHEI units in the copolymer from T_g = 78.9°C of homo PET. In the case of PETN copolymer, 32 mol % of bis(2-Hydroxyethyl)naphthalate (BHEN) units gave T_g of 90°C. The maximum decomposition temperature of PETI copolymer was about the same as that of homo PET by TGA analysis. The char yield at 800°C was higher than that of homo PET. © 1996 John Wiley & Sons, Inc.     

Thermal transitions of ethylene-vinyl chloride copolymers and their blends

Differential Scanning Calorimetry (DSC) measurements were performed on a series of ethylene-vinyl chloride copolymers (E-V) prepared via reductive dechlorination of poly(vinyl chloride) with tributyltin hydride. The copolymers were identical in chain length and branching distribution; differing only in comonomer content, sequence distribution, and stereoregularity of adjacent —V— units. Extrapolation of glass transition temperatures, T_g, measured for our E-V copolymers to pure polyethylene (PE) predicted a T_g = ?85 ± 10°C for amorphous PE. E-V copolymers with greater than 60 mol percent —E— units exhibited melting endotherms from 20 to 128°C and degrees of crystallinity from 12 to 63 percent. The melting point depressions observed for our E-V copolymers were in agreement with Flory's theory, if the ? CH₂? CH₂ moiety is considered to be the crystallizable unit and the moiety is assumed to prevent the ? CH₂? CH₂? units attached on either side from being incorporated into the crystal. In general, the E-V copolymer blends with PE were incompatible, while those with PVC were compatible only for E-V copolymers with high V contents (>80 mol percent). Blends of the amorphous E-V copolymers were found compatible if their V contents differed by less than 15 mol percent, while blends where one or both E-V copolymers are crystalline were found to be incompatible. The properties of these copolymers will be discussed in terms of their microstructure.     

Study on Properties of PVC Blended with Emulsion Copolymer of N-p-tolylmaleimide and Methyl Methacrylate

Copolymers of N-p-tolylmaleimide (NPTMI) and methyl methacrylate (MMA) were synthesized by semi-batch emulsion polymerization. The thermal properties of copolymers and poly (vinyl chloride) (PVC) blended with copolymers had been investigated by thermogravimotric analysis (TGA), torsional braid analysis (TBA) and Vicat softening temperature tester. The results show that the glass transition temperature (T _g) and Vicat softening temperature (T _Vicat) of copolymers increase with increasing NPTMI feed content. The initial decomposition temperature (T _ini) and the temperature where the residual weight reached 50% (T ₅₀) also increase with increasing NPTMI feed content. The T _g and T _Vicat of the blends increase with increasing copolymer feed content. The mechanical properties and rheological behavior were also determined. The results show that the tensile strength of the blendes increase with increasing copolymer feed content while the impact strength keep at the same level. The reheological result illustrated that the blends in melt showed rheological behavior similar to that of pseudoplastic liquid. The apparent viscosity of blends in melt increase with increasing copolymer feed content. The compatibility of the blend system was also investigated by TBA and scanning electro micrograph (SEM).     

Physicomechanical properties of poly(methyl methacrylate-co-N-arylmaleimides)

The article describes the effect of incorporating low mol fractions of N-o-tolymaleimide (MO)/N-p-tolymaleimide (MP) in poly(methyl methacrylate) (PMMA) on T_g, thermal behavior, mechanical, and optical properties. The glass transition temperature (T_g) of PMMA increased by 10–12°C upon incorporation of an ～ 0.026 mol fraction of N-arylmaleimides. A further increase of N-arylmaleimide content up to 0.1 mol fraction in the copolymers resulted in a further ～ 10°C increase in T_g. The tensile strength and % elongation decreased, whereas modulus increased with increasing maieimide content. The solar transmittance and % transmittance at higher wavelengths of the copolymer sheets having a low mol fraction of N-arylmalemides (i.e., 0.026–0.05) were comparable to PMMA. © 1995 John Wiley & Sons, Inc.     

Mechanical properties of vinyl alcohol—ethylene copolymers

The stress‐strain behavior of vinyl alcohol‐ethylene copolymers, with vinyl alcohol as main component, was studied. Films of the copolymer samples, either quenched or slowly cooled from the melt, were stretched at 23, 40 and 80°C. The two former temperatures are below the glass transition (T_g) and the latter is well above the T_g of the studied samples. The drawing process was carried out at different strain rates, and the influence of the stretching parameters (temperature, strain rate) as well as the thermal history and composition of the copolymer samples are discussed in relation to the corresponding homopolymers, poly(vinyl alcohol) and polyethylene. The copolymer with the highest vinyl alcohol content exhibited a critical strain rate, showing maximum values of Young's modulus at a deformation rate around 0.66/min.     

Viscoelastic properties and coating performance of water-soluble acrylic copolymers crosslinked with melamine resin

Acrylic copolymers with different amounts of carboxyl and hydroxyl groups for obtaining practical performance of melamine-cured acrylic coatings was investigated. Property testing results indicated that glass transition temperature (T_g) and shear modulus increased, and molecular weight between crosslinks (M_c) decreased with the increase of hydroxyl and carboxyl number in the acrylic copolymers. The degree of crosslinks influenced the resistance to solvent and chemicals at a lower baking temperature. Compared with acrylic acid, itaconic acid as a carboxyl monomer was more effective in inducing a lower baking schedule. The water-soluble acrylic copolymer, which is neutralized with triethylamine, consists of 20 wt % methylmethacrylate, 55 wt % buthylacrylate, 15 wt % hydroxyethyl methacrylate, and 10 wt % itaconic acid. The copolymer showed higher crosslinks when cured with methoxymethyl melamine formaldehyde resin under a relatively lower baking schedule at 135°C for 30 min. It also has excellent solvent and chemical resistance. This coating film has a T_g value of 39°C, modulus of 2 × 10⁸ dyne/cm² in the rubbery state, and M_c value of 464. Also the acrylic copolymer films with M_c < 900 have good properties for solvent, acid, and alkali resistance. © 1995 John Wiley & Sons, Inc.     

Synthesis of thermoplastic polyurethane and its physical and shape memory properties

In this article, thermoplastic polyurethane (PU) with a shape memory property was synthesized. First, the PU prepolymer was prepared by reacting poly(tetramethylene glycol) with 4,4′‐diphenylmethane diisocyanate, then extended with various extenders such as linear aliphatic 1,4‐butanediol, benzoyl‐type 4,4‐bis(4‐hydroxyhexoxy)‐isopropylane and naphthalate‐type bis(2‐phenoxyethanol)‐sulfone or naphthoxy diethanol. The experimental results showed that the tensile strength, elongation at break, and initial modulus at 300% of these copolymer films were in the range of 31–64 Mpa, 42%–614%, and 8.26–11.5 MPa, respectively. Thermal analysis showed that the glass‐transition temperature of these copolymers was in the range of ?73°C to ?50°C for the soft segment (T_gs) and 70°C–106°C for the hard segment (T_gh) and that the melting point was in the range of 14.6°C–24.2°C for the soft segment and 198°C–206°C for the hard segment. The extender with a benzoyl or naphthalate group was better able to promote its shape memory property than was the regular polyurethane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 607–615, 2006     

Water effect on the morphology of EVOH copolymers

The effect of water on the morphology of four ethylene vinyl alcohol copolymers (EVOH) with different ethylene contents was studied by differential scanning calorimetry (DSC). EVOH film samples equilibrated in controlled atmospheres at different relative humidities (RH) and 23°C were analyzed. Under dry conditions, the glass transition temperature (T_g) was unaffected by copolymer ethylene content. As RH increases, T_g decreases. It seems that the presence of water within the polymer matrix results in plasticization of the polymer. T_g varies from around 50°C (dry) to below room temperature. EVOH copolymers are glassy polymers when dry and rubbery polymers at high RHs. Fox and Gordon–Taylor's equations well describe T_g depletion at low water uptake, although severe water gain results in a considerable T_g decrease, which is not predicted by these theories. Melting temperature, T_m, and enthalpy, ΔH_m, were also analyzed. When dry, T_m decreases as ethylene content increases. No significant water effect was found on either T_m or ΔH_m. Hence, crystallinity seems to be unaffected by water presence. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1201–1206, 1999     

Reactively formed ENPT copolymers as compatibilizers in ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide)

The compatibility of ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide) (PEN/PPT/PEI) was studied by examining the transesterification of PEN and PPT. ENPT copolymers were formed in situ as compatibilizers between PPT and PEI components in ternary blends. Differential scanning calorimetric (DSC) results for ternary blends showed the immiscibility of PEN/PPT/PEI, but ternary blends of all compositions were phase‐homogeneous after heat treatment at 300°C for more than 60 min. Annealing samples at 300°C yielded amorphous blends with a clear, single glass transition temperature (T_g), as the final state. Additionally, ENPT copolymer improved the compatibility of ENPT/PPT/PEI blends, yielding a homogeneous phase in the ENPT‐rich compositions. The morphology of the ENPT/PPT/PEI blends was altered from heterogeneous to homogeneous by controlling the concentration of PPT in the ENPT copolymers as well as the concentration of the ENPT copolymers. Moreover, a homogeneous phase with a clear T_g was observed when the concentration of PPT in the ENPT copolymer fell to 70 wt% in the ENPT/PEI = 50/50 blends. Experimental results indicate how the concentration of PPT in the ENPT copolymer affects miscibility in the ENPT/PEI blends. POLYM. ENG. SCI. 46:337–343, 2006. © 2006 Society of Plastics Engineers     

Thermal analysis,glass transition temperature and rheological behaviour of emulsion copolymers of methyl methacrylate with styrene

Poly(MMA‐ran‐St) samples were synthesized under monomer‐starved conditions (drop feeding method) by emulsion copolymerization. Their thermostability was determined by thermogravimetric analysis. The glass transition temperature (T_g) of the copolymers was determined by differential scanning calorimetry (DSC) and torsional braid analysis (TBA). The results showed that the MMA–St copolymers exhibit an asymmetric T_g versus composition curve, which could not be interpreted by Johnston's equation, taking the different contributions of the diads to the T_g of the copolymer into consideration. A new sequence distribution equation taking into account the different contributions of the triads was proposed to predict the copolymer T_g. The new equation fitted the experimental data exactly. The T_g determined by torsional braid analysis (TBA) is higher than the one determined by DSC, but the difference is not constant. The rheological behaviour of the copolymers was also studied and T_gTBA‐T_gDSC increased with the increasing flow index of the copolymer. © 2003 Society of Chemical Industry