Average Molar Mass Research Articles

Effects of Thermal Aging on Molar Mass of Ultra-High Molar Mass Polyethylene Fibers.

Ultra-high molar mass polyethylene (UHMMPE) is commonly used for ballistic-resistant body armor applications due to the superior strength of the fibers fabricated from this material combined with its low density. However, polymeric materials are susceptible to thermally induced degradation during storage and use, which can reduce the high strength of these fibers, and, thus, negatively impact their ballistic resistance. The objective of this work is to advance the field of lightweight and soft UHMMPE inserts used in various types of ballistic resistant-body armor via elucidating the mechanisms of chemical degradation and evaluating this chemical degradation, as well as the corresponding physical changes, of the UHMMPE fibers upon thermal aging. This is the first comprehensive study on thermally aged UHMMPE fibers that measures their decrease in the average molar mass via high-temperature size exclusion chromatography (HT-SEC) analysis. The decrease in the molar mass was further supported by the presence of carbon-centered free radicals in the polyethylene that was detected using electron paramagnetic resonance (EPR) spectroscopy. These carbon-centered radicals result from a cascade of thermo-oxidative reactions that ultimately induce C–C ruptures along the backbone of the polymer. Changes in the crystalline morphology of the UHMMPE fibers were also observed through wide-angle X-ray diffraction (WAXS), showing an increase in the amorphous regions, which promotes oxygen diffusion into the material, specifically through these areas. This increase in the amorphous fraction of the highly oriented polyethylene fibers has a synergistic effect with the thermo-oxidative degradation processes and contributes significantly to the decrease in their molar mass.

Inverse Vulcanization of Norbornenylsilanes: Soluble Polymers with Controllable Molecular Properties via Siloxane Bonds.

The inverse vulcanization produces high sulfur content polymers from alkenes and elemental sulfur. Control over properties such as the molar mass or the solubility of polymers is not well established, and existing strategies lack predictability or require large variations of the composition. Systematic design principles are sought to allow for a targeted design of materials. Herein, we report on the inverse vulcanization of norbornenylsilanes (NBS), with a different number of hydrolysable groups at the silicon atom. Inverse vulcanization of mixtures of NBS followed by polycondensation yielded soluble high sulfur content copolymers (50 wt % S) with controllable weight average molar mass (MW), polydispersity (Đ), glass transition temperature (T G), or zero‐shear viscosity (η 0). Polycondensation was conducted in the melt with HCl as a catalyst, abolishing the need for a solvent. Purification by precipitation afforded polymers with a greatly reduced amount of low molar mass species.

Cellulose nanocrystals from native and mercerized cotton

Nanocelluloses occur under various crystalline forms that are currently being selectively used for a wide variety of high performance materials. In the present study, two cellulose nanofibers (CF-I) were mercerized by alkaline treatment (CF-II) without degradation, the same molar mass of 560,000 g/mol was measured. Both samples were acid hydrolyzed, leading to cellulose nanocrystals in native (CNC-I) and mercerized (CNC-II) forms. This study focuses on the detailed characterization of these two nanoparticle morphologies (light and neutron scattering, TEM, AFM), surface chemistry (zetametry and surface charge), crystallinity (XRD, 13C NMR), and average molar mass coupled to chromatographic techniques (SEC–MALLS-RI, A4F-MALLS-RI), revealing variations in the packing of the crystalline domains. The crystal size of CNC-II is reduced by half compared to CNC-I, with molar masses of individual chains of 41,000 g/mol and 22,000 g/mol for CNC-I and CNC-II, respectively, whereas the same surface charge density is measured. This study gives an example of complementary characterization techniques as well as results to help decipher the mechanism involved in mercerization.

Effect of Extraction Procedures with Ultrasound and Cellulolytic Enzymes on the Structural and Functional Properties of Citrus grandis Osbeck Seed Mucilage.

The structural and functional properties of Citrus grandis Osbeck (CGO) seed mucilage by different extraction practices, including conventional citrate buffer, ultrasonic-assisted (UAE), enzymatic-assisted extraction (EAE) with cellulase or Celluclast® 1.5 L and various ultrasonic-assisted enzymatic extraction (UAEE) procedures were investigated. It was found that CGO seed from agricultural and processing byproducts is an excellent new source of high methoxyl pectin with quite high intrinsic viscosity (about 108.64 dL/g) and molecular weight (about 1.9 × 106) as compared with other pectin sources. UAEE with Celluclast® 1.5 L enhanced the extraction yield most pronouncedly (about 2.3 times). Moreover, the monosaccharide composition of CGO seed mucilage is least affected by EAE with Celluclast® 1.5 L. In contrast, EAE with cellulase dramatically reduces the galacturonic acid (GalA) content to less than 60 molar%, and increases the glucose (Glc) content pronouncedly (to about 40 molar%), which may be considered as an adverse effect in terms of pectin purity. Though extraction procedures involved with ultrasound and cellulolytic enzymes generally show a decrease in GalA contents, weight average molar mass and intrinsic viscosity, EAE with Celluclast® 1.5 L is least affected, followed by UAE and UAEE with Celluclast® 1.5 L. These features can be leveraged in favor of diversified applications.

Influence of Methylation and Polymerization on Flocculant Properties of Bovine Blood.

Flocculants are used in the primary step of wastewater treatment to precipitate solids. Bovine blood is a slaughterhouse byproduct, and there is limited evidence in the literature demonstrating that it can be used as a flocculant. In this study, native bovine blood (NBB) and three types of chemically modified blood (methylated bovine blood (MeBB), polymerized bovine blood (PolyBB), and polymerized & methylated bovine blood (PMBB)) were tested against suspensions of negatively charged kaolin or positively charged hematite. The methylation reaction had the expected effect of increasing the apparent isoelectric point of MeBB and PMBB relative to that of the NBB starting material, and the polymerization reaction had the intended effect of increasing the average molar mass. NBB and PolyBB performed well with kaolin suspensions at pH ≤5.5, and MeBB showed high and consistent performance, across the pH range of 4.5–8.5. Relative to NBB, MeBB had improved potency and pH independence but also the disadvantage of increased sensitivity to overdosing. The performance of PolyBB was very similar to that of NBB. PMBB had performance enhancements similar to those of MeBB, with a modest improvement in its overdose sensitivity. The performances of MeBB and PMBB with hematite suspensions were poor at all tested doses (2–100 mg/g hematite), whereas a 30 mg/g dose of PolyBB showed 81% precipitation in an hour. The results show that simple chemical treatments can improve the utility of blood as a flocculant for negatively charged solids.

A Review of Experimental Solubilities and a General Correlation between the Temperature-Dependent Solubility and Solute and Solvent Molar Masses for Binary n-Alkane Mixtures

The solubility of a ”heavy” alkane (solute) in a ”light” alkane (solvent) is generally temperature dependent. Moreover, it is determined by the molar masses of the solute and solvent. In the current paper, published solubility data for binary normal-alkane mixtures is reviewed (solid-liquid equilibrium). A total of 43 unique solute-solvent data-sets, obtained from a total of 24 published experimental studies, are collected and presented in a systematic manner. Based on thermodynamic considerations and the experimental data, it is demonstrated that there is a log-linear relationship between the solubility and the temperature in the dilute range. Linear regression is employed to 1) obtain data-set-specific solubility-temperature best-fit parameters and 2) obtain a general correlation between the solubility and the solvent and solute molar masses and the temperature. Finally, it is demonstrated that the developed correlation carries predictive power even for multi-component mixtures by utilizing solvent and solute average molar masses.

Molecular Characteristics and Antioxidant Activity of Spruce (Picea abies) Hemicelluloses Isolated by Catalytic Oxidative Delignification.

Spruce (Picea abies) wood hemicelluloses have been obtained by the noncatalytic and catalytic oxidative delignification in the acetic acid-water-hydrogen peroxide medium in a processing time of 3–4 h and temperatures of 90–100 °C. In the catalytic process, the H2SO4, MnSO4, TiO2, and (NH4)6Mo7O24 catalysts have been used. A polysaccharide yield of up to 11.7 wt% has been found. The hemicellulose composition and structure have been studied by a complex of physicochemical methods, including gas and gel permeation chromatography, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. The galactose:mannose:glucose:arabinose:xylose monomeric units in a ratio of 5:3:2:1:1 have been identified in the hemicelluloses by gas chromatography. Using gel permeation chromatography, the weight average molar mass Mw of hemicelluloses has been found to attain 47,654 g/mol in noncatalytic delignification and up to 42,793 g/mol in catalytic delignification. Based on the same technique, a method for determining the α and k parameters of the Mark–Kuhn–Houwink equation for hemicelluloses has been developed; it has been established that these parameters change between 0.33–1.01 and 1.57–472.17, respectively, depending on the catalyst concentration and process temperature and time. Moreover, the FTIR spectra of the hemicellulose samples contain all the bands characteristic of heteropolysaccharides, specifically, 1069 cm−1 (C–O–C and C–O–H), 1738 cm−1 (ester C=O), 1375 cm−1 (–C–CH3), 1243 cm−1 (–C–O–), etc. It has been determined by the thermogravimetric analysis that the hemicelluloses isolated from spruce wood are resistant to heating to temperatures of up to ~100 °C and, upon further heating, start destructing at an increasing rate. The antioxidant activity of the hemicelluloses has been examined using the compounds simulating the 2,2-diphenyl-2-picrylhydrazyl free radicals.

Synthesis and characterization of novel poly(α-methyl β-alanine-b-lactone)s through hydrogen-transfer and ring-opening polymerization

Abstract A series of novel poly(α-methyl β-alanine-b-lactone)s were prepared by a combination of hydrogen-transfer polymerization (HTP) of methacrylamide (MAm) and anionic ring-opening polymerization (AROP) of β-propiolactone (BPL), β-butyrolactone (BBL), and δ-valerolactone (DVL). For this purpose, poly(α-methyl β-alanine) (PmBA) having a living anionic end-group for a further extension was obtained via HTP of MAm. The anionic end-group on PmBA chains were used as initiation sites for AROP of BPL, BBL, and DVL. Fourier Transform Infrared Spectroscopy (FTIR) and Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR) confirmed the existence of both ester and α-methyl β-alanine (mBA) units in the final products. MALDI-MS analysis revealed that the poly(α-methyl β-alanine-b-lactone)s with average molar masses of several thousand g·mol−1 were obtained. DSC and TGA thermograms of each copolymer showed that the copolymers comprised the mBA and the corresponding ester units.

Direct and indirect effects on molecular mobility in renewable polylactide-poly(propylene adipate) block copolymers as studied via dielectric spectroscopy and calorimetry.

In this work, we study a series of sustainable block copolymers based on polylactide, PLA, and poly(propylene adipate), PPAd, both polymers being prepared from renewable resources. Envisaging a wide range of future applications in the frame of a green and circular economy, e.g., packaging materials replacing conventional petrochemicals, the employment of PPAd aims at lowering the glass transition and melting temperatures of PLA and, finally, facilitation of the enzymatic degradation and compostability. The copolymers have been synthesized via ring opening polymerization of lactides in the presence of propylene adipate oligomers (5, 15 and 25%). The direct effects on the molecular mobility by the structure/composition are assessed in the amorphous state employing broadband dielectric spectroscopy (BDS) and calorimetry. BDS allowed the recording of local PLA and PPAd dynamics in all cases. The effects on local relaxations suggest favoring of interchain interactions, both PLA-PPAd and PPAd-PPAd. Regarding the more important segmental dynamics, the presence of PPAd leads to faster polymer chain diffusion, as monitored by the significant lowering of the dielectric and calorimetric glass transition temperature, Tg. This suggests the plasticizing role of PPAd on PLA (majority) in combination with the lowering of the average molar mass, Mn, in the copolymers from ∼75 to ∼30 kg mol-1, which is the actual scope for the synthesis of these materials. Interestingly, a strong suppression in fragility (chain cooperativity) is additionally recorded. In contrast to calorimetry and due to the high resolving power of BDS, for the higher PPAd fraction, the weak segmental relaxation of PPAd was additionally recorded. Overall, the recordings suggest a strong increase in free volume and two individual dynamic states, one for 0 and 5% PPAd and another for 15 and 25% PPAd. Within the latter, we gained indications for partial phase nano-separation of PPAd. Regarding indirect effects, these were followed via crystallization. Independent of the method of crystallization, namely, melt or cold, the presence of PPAd led to the systematic lowering of crystallization and melting temperatures and enthalpies. The effects reflect the decrease of crystalline nuclei, which is confirmed by optical microscopy as in the copolymers fewer although larger crystals are formed.

Native and fermented waxy cassava starch as a novel gluten-free and clean label ingredient for baking and expanded product development.

Amylose-free and wild-type cassava starches were fermented for up to 30 days and oven- or sun-dried. The specific volume (ν) after baking was measured in native and fermented starches. The average ν (across treatments) for waxy starch was 3.5 times higher than that in wild-type starches (17.6 vs. 4.8 cm3 g-1). The best wild-type starch (obtained after fermentation and sun-drying) had considerably poorer breadmaking potential than native waxy cassava (8.4 vs. 16.4 cm3 g-1, respectively). The best results were generally obtained through the synergistic combination of fermentation (for about 10-14 days) and sun-drying. Fermentation reduced viscosities and the weight average molar mass led to denser macromolecules and increased branching degree, which are linked to a high loaf volume. The absence of amylose, however, was shown to be a main determinant as well. Native waxy starch (neutral in taste, gluten-free, and considerably less expensive than the current alternatives to cassava) could become a new ingredient for the formulation of clean label-baked or fried expanded products.

Utilization of Bitter Orange Seed as a Novel Pectin Source: Compositional and Rheological Characterization

The seeds from bitter orange, the by-product of juice making units, hold the potential to facilitate novel, easy yet high-quality pectin extraction. To test this hypothesis, orange seed pectin (OSP) was extracted by distilled water and its compositional parameters and rheological behavior were then evaluated. Results showed that galacturonic acid was the major component of OSP (∼425 mg/g) confirming the purity of the extracted pectin, followed by glucose and some minor neutral sugars. The Mw (weight-average molar mass), Rn (number average molar mass), and Rz (z-average molar mass) values for the OSP were 4511.8 kDa, 61 nm, and 61.1 nm, respectively. Rheological measurements showed a shear-thinning behavior for OSP so that the viscosity of the gum decreased by increasing the temperature from 5 to 45°C. The Power-law model fitted as the best rheological model describing the flow behavior of OSP. The strain sweep dynamic rheological measurements confirmed an entangled network structure for OSP and the NaCl addition to the gum dispersion decreased the consistency coefficient from 35.6 to 23.18 Pa.sn , while the flow behavior index remained unchanged. These results demonstrate that the OSP can be used as a new source of pectin, with likely a wide range of applications in the food industry.

Water as a monomer: synthesis of an aliphatic polyethersulfone from divinyl sulfone and water.

Using water as a monomer in polymerization reactions presents a unique and exquisite strategy towards more sustainable chemistry. Herein, the feasibility thereof is demonstrated by the introduction of the oxa-Michael polyaddition of water and divinyl sulfone. Upon nucleophilic or base catalysis, the corresponding aliphatic polyethersulfone is obtained in an interfacial polymerization at room temperature in high yield (>97%) within an hour. The polyethersulfone is characterized by relatively high molar mass averages and a dispersity around 2.5. The polymer was tested as a solid polymer electrolyte with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the salt. Free-standing amorphous membranes were prepared by a melt process in a solvent-free manner. The polymer electrolyte containing 15 wt% LiTFSI featured an oxidative stability of up to 5.5 V vs. Li/Li+ at 45 °C and a conductivity of 1.45 × 10−8 S cm−1 at room temperature.

Mechanical and macromolecular changes during thermal degradation of polyphenylsulfone

Polyphenylsulfone was thermally aged at temperatures corresponding to its processing and was mainly shown to undergo crosslinking as observed by measurements of average molar mass, rheometry and changes in glass transition temperature. Those experiments were completed by mechanical testing thin sample films at 250 and 280 °C. The same degradation mechanisms were observed and result in a strong decrease of ultimate strain accompanied by a slight decrease in elastic modulus and yield stress. Overall results were discussed using well know structure-properties relationships.

Characterization of Potential Pollutants from Poly(lactic acid) after the Degradation Process in Soil under Simulated Environmental Conditions

In recent years, the amount of produced petrochemical plastic waste has been growing at an alarming rate. According to the Plastics Europe Market Research Group (PEMRG)/Conversio Market & Strategy GmbH, in 2018 the global production of plastics amounts to 359 million tons, and in Europe—61.8 million tons. More than 80% of all marine litter is plastic, which accumulates in the environment due to its durability. Due to the growing problem, biodegradable polymer products are introduced to the market. Therefore, it is necessary to conduct research on degradation products in order to estimate the risk arising from their presence in the environment. This paper discusses research on compounds that may potentially remain in the soil after the degradation of the double green PLA polymer. The aim of the research was to prove whether products made of PLA, e.g., packaging, films and other waste can release substances harmful to the environment. Therefore, soil was selected as a medium to characterize the substances potentially released from the polymer under conditions simulating the degradation process in the environment. The soil was always used from the same producer. Before the polymer biodegradation process, it was additionally checked for pH, C and N content, number of microorganisms, etc. PLA degradation in soil was carried out in a laboratory accredited by the Polish Accreditation Center (PCA). During the research, soil samples at various stages of the degradation process under laboratory conditions were subjected to both extraction in an aqueous environment and organic solvent extraction The studies used the gas chromatography coupled with mass spectrometry (GC/MS), as well as pyrolysis gas chromatography (Py-GC/MS). In addition, the study used the gel permeation chromatography (GPC/SEC) allowing to determine the distribution of molar masses, average molar masses and polydispersity, and the infrared spectroscopy (FTIR).

In Silico Screening To Achieve Fast Lab-Scale Nitroxide-Mediated Polymerization of n-Butyl Acrylate with Maximal Control over Macromolecular Properties

Nitroxide-mediated polymerization (NMP) allows one to synthesize well-defined polymers with narrow molar mass distribution (MMD) and latent functionality. For acrylates, however, side reactions, such as backbiting and β-scission and increases in viscosity, can complicate the molecular control, affecting the MMD dispersity, the double bound content, and the degree of livingness. On top of this, acrylate polymerizations are highly exothermic and thus dedicated temperature control is recommended, even under general lab-scale NMP conditions. In the present work, we account for both side reactions, diffusional limitations and nonisothermicity, so that a detailed model-based design for NMP of n-butyl acrylate can be performed in view of a better evaluation of its commercial potential. The relevance of temperature control and semibatch feeding strategies is particularly explored, benefiting from (i) a successful benchmark to NMP lab-scale batch literature data and (ii) a previous successful benchmark under various lab-scale free radical polymerization (FRP) conditions. It is showcased that specific set points of NMP characteristics, e.g., polymerization time, number average molar mass, and unsaturation level, can be achieved for a high monomer conversion by realizing less conventional thus nonlinear number average molar mass profiles, which is highly relevant for the polymer synthesis and reaction engineering community. The current work, which puts forward a dedicated research strategy from FRP to NMP to minimize error on kinetic parameter determination steps, opens the pathway to maximize the potential of reversible deactivation radical polymerization techniques for their more elegant implementation and appreciation in the society.

Novel ABA–type Block Copolymers from Telechelic PEG–initiated Hydrogen–transfer Polymerization

ABSTRACT Novel ABA-type block copolymers were prepared using end-groups activated poly(ethylene glycol) (PEG) as an initiator for hydrogen transfer polymerization (HTP). For this purpose, PEG with average molar mass of 1450 Da (PEG-1450) was firstly treated with the equivalent amount of sodium hydride to synthesize PEG with dialkoxide end-groups, namely PEG-dialkoxide. Using the PEG-dialkoxide as a macroinitiator, base-catalyzed HTP of acrylamide, N-methoxypropyl acrylamide, and 2-hydroxyethyl acrylate were then performed to achieve the novel ABA-type block copolymers. The copolymers were obtained with high yields of about 90%. Characterization of the ABA-type copolymers was carried out using Fourier Transform Infrared Spectroscopy (FTIR spectroscopy) and Matrix Assisted Laser Desorption Ioizaton (MALDI) mass spectrometry. FTIR spectra of the copolymers exhibited some characteristic bands assigned to the functional groups arising from the mechanism of HTP. Molar mass distributions of the copolymers from the MALDI mass study pointed out that chain extensions by mass in each copolymer were almost equal. Hence, the MALDI mass spectra of the copolymers revealed that chain extensions of telechelic PEGs by β-alanine, 2-hydroxyethyl acrylate, and N-methoxypropyl β-alanine units were successfully fulfilled.

Ultra‐High Alignment of Polymer Semiconductor Blends Enabling Photodetectors with Exceptional Polarization Sensitivity

AbstractPhotodetectors that can sense not only light intensity but also light's polarization state add valuable information that is beneficial in a wide array of applications. Polymer semiconductors are an attractive material system to achieve intrinsic polarization sensitivity due to their anisotropic optoelectronic properties. In this report, the thermomechanical properties of the polymer semiconductors PBnDT‐FTAZ and P(NDI2OD‐T2) are leveraged to realize bulk heterojunction (BHJ) films with record in‐plane alignment. Two polymer blends with distinct weight average molar masses (Mw) are considered and either a strain‐ or rub‐alignment process is applied to align the polymer blend films. Optimized processing yields films with dichroic ratios (DR) of over 11 for the high Mw system and nearly 17 for the low Mw system. Incorporating the aligned films into photodetectors results in a polarized photocurrent ratio of 15.25 with corresponding anisotropy ratio of 0.88 at a wavelength of 530 nm, representing the highest reported photocurrent ratio for photodiodes that can operate in a self‐powered regime. The demonstrated performance showcases the ability of polymer semiconductors to achieve BHJ films with exceptional in‐plane polymer alignment, enabling high performance polarization sensitive photodetectors for incorporation into novel device architectures.

Lipase-catalyzed synthesis of furan-based aliphatic-aromatic biobased copolyesters: Impact of the solvent

• CALB allows the synthesis of furan based polyesters with high aromatic content. • Growing chains precipitation for high aromatic contents results in low molar masses. • Improved solubility in acetophenone leads to higher Mn and thermal properties. Enzymatic polymerization is a promising route for a greener synthesis of biobased polyesters. However, this approach is still often limited to aliphatic polyesters, which present limited properties such as low thermal resistance. In this context and till now, introduction of aromatic monomers into polyesters very often resulted in low molar mass chains. Herein, aliphatic–aromatic copolyesters based on dimethyl-2,5-furandicarboxylate were enzymatically synthesized using immobilized Candida antarctica lipase B with a particular focus on the influence of the solvent used. Two series of poly(hexylene adipate)–co-(hexylene furanoate) and poly(butylene adipate)–co-(butylene furanoate) copolyesters were successfully synthesized in diphenyl ether, displaying high molar masses (M n up to 19 000 g.mol −1 ) for aromatic monomer contents up to 70 and 50%, respectively. High aromatic content resulted in reduced molar masses due to a loss of solubility of the growing aromatic chains. Replacing diphenyl ether by acetophenone, which had never been used before as solvent for enzymatic synthesis of polyesters, led to significantly enhanced solubility and thus an increase in the average molar masses of poly(hexylene furanoate) and poly(butylene furanoate). The resulting polyesters showed greater thermal stability and higher T g , offering new perspectives for expanding the potential applications of such enzymatically-produced biobased aromatic copolyesters.

Temperature gradient interaction chromatography of linear polyethylene and isotactic polypropylene

Samples of linear polyethylene and isotactic polypropylene were separated according to their average molar mass using temperature gradient interaction chromatography (TGIC) with mobile phases at near critical composition. It is known that at the critical mobile phase composition, the adsorption of polymers is very sensitive to variations of the temperature. This effect was utilized here. The temperature of the column (Hypercarb™) was changed from 80 °C to 170 °C according to a programmed temperature gradient. Polymers were first adsorbed in the column at 80 °C and desorbed by the temperature increase. In effect, the polymers eluted at different temperatures. The higher the molar mass, the higher both the elution temperature and the elution volume. This suggests that TGIC has the potential to improve separations of polyolefins according to their molar mass and will allow to separate polyolefins according to their long-chain branching content.

Multiscale study of poly(butylene terephthalate) hydrolysis

This paper reports the hydrolysis of several PBT materials (pigmented or not). Degradation was monitored by gel permeation chromatography (chain scission), DSC (crystalline morphology), tensile test (residual mechanical properties) and DVS (polymer-water interaction). The embrittlement comes from chain scission associated with a small chemicrystallization effect. Results lead to the proposal of a kinetic model for the chain scission rate aimed to describe the auto-acceleration effect induced by carboxylic acids (chain ends) and successfully compared to results both from this work or literature. The mixed “average molar mass – crystallinity” criterion proposed in a previous paper was specified. At last, the effect of pigments is illustrated and shows that carbon black (present in particular in one masterbatch) plays an aggravating role on hydrolysis.