Oxygen permeation in SBS-g-DMAEMA copolymer membrane prepared by UV photografting without degassing

The grafting of dimethyl amino ethyl methacrylate (DMAEMA) onto styrene–butadiene–styrene triblock copolymer membrane (SBS) was induced by UV-radiation without degassing to obtain SBS-g-DMAEMA copolymer membrane. The graft copolymer membrane was characterized by electron spectroscopy for chemical analysis (ESCA). The density and the decomposition temperature of the SBS-g-DMAEMA copolymer membrane were measured. The effects of DMAEMA grafting content and operating temperature on membrane gas permeability were investigated. It was found that the density of SBS-g-DMAEMA copolymer membrane increased with increasing DMAEMA content, whereas the decomposition temperature decreased. The changes of properties of SBS-g-DMAEMA copolymer membrane reduced the gas permeability and diffusivity of oxygen and nitrogen through the membrane, but increased the gas solubility of oxygen through the membrane and the gas selectivity between oxygen and nitrogen. When the operating temperature of gas permeation was increased, the permeability, solubility and diffusivity of oxygen and nitrogen increased but the selectivity decreased.     

Polymeric complex membranes based on styrene–diene–styrene triblock copolymers for oxygen enrichment

Polymers containing a vinylpyridine, vinylimidazole or oxirane group could be used to immobilize cobalt Schiff bases (CoS), which serve as the oxygen carrier in oxygen enrichment. The graft copolymers, based on styrene–butadiene–styrene (SBS) and styrene–isoprene–styrene grafted with 4-vinylpryidine and 1-vinylimidazole, and epoxidized SBS copolymers were prepared to immobilize CoS. The equilibrium constants between CoS and polymeric materials, the oxygen coordination number and the oxygen binding constants were determined. The thermodynamic parameters of oxygen association/dissociation in various complex membranes were determined. The oxygen permeation behavior through various CoS-containing complex membranes was studied and discussed by the dual-mode facilitated transport theory. The permeation properties of oxygen and nitrogen at low pressure were also investigated.     

Properties of HTPB based polyurethane membrane prepared by epoxidation method

Hydroxyl-terminated polybutadiene (HTPB) based polyurethane (PU) was synthesized by solution polymerization. The PU was then cast into membrane. The epoxidation of HTPB based PU membrane by an in situ generated peracid method is discussed. The chemical composition of the epoxidized PU membrane was studied by infrared spectroscopy. The absorption peak at 970 cm⁻¹ for the CC double bond decreased with epoxidation time whereas the absorption peak at 1183 cm⁻¹ for oxirane group increased. The absorption peak at about 1700–1740 cm⁻¹ for the CO group and –OH group at about 3200–3700 cm⁻¹ increased with epoxidation time that indicated the side reaction of epoxidation took place. The oxirane weight content was determined by titration method. The density, tensile strength, elongations, and decomposition temperature of the epoxidized PU membranes were measured. The molecular weight between crosslinking points PU membrane was calculated. Contact angle and protein absorption of fibrinogen and albumin experiments were also determined. It was found that the density and the tensile strength of epoxidized PU membrane increased with increasing epoxidation time whereas the molecular weight between crosslinking points, elongation and the amount of protein adsorption on the epoxidized PU membrane decreased. By using Kaelble’s equation and the contact angle data, the surface tension of epoxidized PU membrane was determined. It was found that the surface tension of epoxidized PU membrane increased whereas the contact angle decreased with epoxidation time. The property changes reduced the permeability of gas through epoxidized PU membrane, but increased the gas selectivity between oxygen and nitrogen. The activation energies (E_p) for gas diffusing through various epoxidized PU membranes were obtained by the Arrhenius law; it is evident that E_p increased with the extent of epoxidation.     

Dynamic mechanical and dielectric properties of epoxidized SBS triblock copolymer

The morphological and dynamic properties of epoxidized styrene–butadiene–styrene block copolymers were studied and compared with their parent styrene–butadiene–styrene block copolymer (SBS). Two peaks were observed in the mechanical loss (tan δ) curve which can be attributed to segmental motion of epoxidized polybutadiene (EPPB) and polystyrene. Analysis by DSC thermograms also showed the linear increase of glass transition temperature for EPPB domain with the epoxy group content. Phase separated structures of epoxidized SBS as observed by TEM suggests a considerable degree of mixing occurred between phases after 80 mol % of the double bonds in SBS were epoxidized. The interfacial region displays a third peak and causes much steeper drop in modulus at higher temperature than T_g of EPPB. Parallel dielectric relaxation measurements were also made in the frequency range of 30 Hz–1 KHz as a function of temperature. In each dielectric constant (?′) curve, there is a maximum near the T_g of EPPB determined from the dielectric loss tangent curve. The shift in T_g of EPPB versus epoxy group content was consistent with that measured by the thermal and dynamic mechanic analysis. These findings indicated an 8°C shift in glass transition temperature as the epoxy group content in EPPB increased 10%.     

溴代及胺交联聚苯醚（PPO）膜的气体透过行为

对聚苯醚(PPO)进行了苯环溴代、甲基溴代以及胺交联,发现苯环溴代可提高O_2、N_2透过率(P),而选择性(α)基本不变。甲基溴代则相反,P降低、α有明显提高。调节两者比例可得到P、α兼优的O_2、N_2分离膜。甲基溴代后进一步胺交联可得到α更高、耐溶剂的膜材料。     

Mechanical properties,surface chemistry,and barrier characteristics of electron beam irradiated‐annealed LDPE/PA6/LDPE multi‐layer films at N2

The effects of electron beam irradiation in the nitrogen environment, on chain scission, crosslinking, crystallinity, mechanical performance, and barrier properties of LDPE/PA6/LDPE multi‐layer films were studied. The evaluation of radiation‐induced crosslinking effect by the gel content measurement and Charlesby–Pinner plot suggested more of crosslinking over chain scission, in all the layers, which was more pronounced in polyethylene phase. The FTIR analysis results showed good agreement with those observed by the gel content measurements. It is believed that the crosslinking reaction had occurred through the C? N bonds in polyamide‐6, and vinyl group in polyethylene layers. The evaluation of radiation effect on the crystallinity and crosslinking of films by FTIR technique showed that by increasing the applied doses, the crystallinity in all the layers was decreased and the crosslinking was increased. The differential scanning calorimetry of irradiated samples revealed that due to the crosslinking reaction, the crystallinity was decreased by the applied dose. The tensile strength of the films was increased and the percent elongation at break was decreased, by increasing the applied doses. This study was also indicated that the radiation‐induced crosslinking effect on the tensile properties was dominantly observed up to 50 kGy. The surface free energy analysis of the films using the contact angle measurement and geometric mean equation indicated that the surface polarity was decreased by increasing the absorbed doses. It was found that due to the decline in the surface polarity and the simultaneously formation of crosslinked network in these films, both water vapor transmission rate and oxygen permeability were significantly decreased. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis of Maleated Ionomers via Ring‐Opening Reaction of Epoxidized (Styrene‐Butadiene‐Styrene) Triblock Copolymer with Potassium Hydrogen Maleate and Study of their Properties

A novel method for synthesizing maleated ionomer of (styrene‐butadiene‐styrene) triblock copolymer (SBS) from epoxidized SBS was developed. The epoxidized SBS was prepared via epoxidation of SBS with performic acid formed in situ by 30% H₂O₂ and formic acid in cyclohexane in the presence of polyethylene glycol 600 as a phase transfer catalyst. The maleated ionomer was obtained by a ring‐opening reaction of the epoxidized SBS solution with an aqueous solution of potassium hydrogen maleate. The optimum conditions for the ring‐opening reaction and some properties of the ionomers were studied. It is necessary to use phase transfer catalyst, ring‐opening catalyst and a pH regulator (dipotassium maleate) for obtaining the epoxy group conversion over 90%. The product was characterized by FTIR spectrophotometry and transmission electron microcroscopy (TEM) to be an ionomer with domains of maleate ionic groups. With increasing ionic groups, the water absorbency and the dilute solution viscosity of the ionomer increase, whereas the oil absorbency decreases. The tensile strength and ultimate elongation of ionomers increase with ionic group content and are higher than those of the original SBS without using any ionic plasticizer, which is usually used with the sulfonated ionomer. The ionomers with 1.2–1.7 mmol ionic groups/g exhibit optimum mechanical properties and behave as thermoplastic elastomers. The ionomer can be used as a compatibilizer for the blends of SBS with oil resistant chlorohydrin rubber (CHR). Addition of 3 wt% ionomer to the blend can increase the tensile strength and ultimate elongation of the blend optimally. The compatibility of the blends enhanced by adding the ionomer was shown by scanning electron microscopy (SEM). The blend of equal weight of SBS and CHR compatibilized by the ionomer behaves as a toluene resistant thermoplastic elastomer.     

Oxygen/nitrogen separation by polycarbonate/Co(SalPr) complex membranes

An oxygen carrier, cobalt di-(salicylal)-3,3′-diimino-di-n-propylamine (Co(SalPr)), was added into a polycarbonate membrane for improving its oxygen/nitrogen selectivity. Both the oxygen permeability and oxygen/nitrogen selectivity increased when only 3 wt% of Co(SalPr) was added. The permeability kept increasing but the selectivity decreased when more than 3 wt% of Co(SalPr) was added. The oxygen to nitrogen solubility ratio decreased when 3 wt% of Co(SalPr) was added. Further increase in Co(SalPr) content led to an increase in oxygen/nitrogen solubility ratio. It was astonishing to know that the effect of Co(SalPr) content on the oxygen/nitrogen solubility ratio was totally opposite to that on the oxygen/nitrogen selectivity. A membrane gas transport model which combines the dual mobility model with pore model was adopted to explain the above phenomenon. The specific volume measurement implied that the pore diffusion was responsible for this behavior. The contribution of sorption-diffusion type transport was also investigated by examining the transport behavior of the 3 wt% Co(SalPr) containing membrane through which the pore diffusion is relatively low. The effect of upstream pressure on the oxygen permeability and solubility implied that the diffusivity of Henry's mode was much higher than that of Langmuir's mode. It was also found that the effects of upstream pressure and operating temperature on the oxygen/nitrogen selectivity were both in accordance with those on the Henry's mode solubility ratio. The above information suggested that in addition to the pore diffusion the ratio of Henry's mode diffusion dominated the O₂/N₂ separation instead of the overall O₂ to N₂ solubility ratio.     

Catalytic epoxidation of styrene–butadiene triblock copolymer with hydrogen peroxide

Styrene-butadiene-styrene linear block copolymer (SBS) can be epoxidized with hydrogen peroxide in the presence of methyltrioctylammonium tetrakis (diperoxotungsto) phosphate(3-) as the catalyst in a biphasic system. The effects of reaction time, temperature, solvent, the ratio of the organic phase to the aqueous phase, the concentration of the catalyst, hydrogen peroxide and polymer, respectively, are studied on the conversion of double bonds to oxirane groups. ¹H-NMR analysis confirms the absence of ring opening side reaction in this epoxidation reaction system up to at least 70% conversion of the double bonds. When the conversion of double bonds is over about 70% the resultant polymer is insoluble in chloroform even at reflux but soluble in polar solvents such as DMSO when heated. Toluene is a better solvent for the reaction than dichloroethane. The reaction rate constants are measured at four temperatures and the activation energy for the reaction with toluene as solvent is determined as 49.9 kJ/mol.     

Gas transport in polyurethane-polystyrene interpenetrating polymer network membranes. I. Effect of synthesis temperature and molecular structure variation

The gas (oxygen and nitrogen) transport characteristics of the interpenetrating polymer network (IPN) membranes of polyurethane/polystyrene were studied. The effect of synthesis temperature, composition, molecular weight of the polyol and aromatic content (of MDI, TDI and HDI) on the gas permeability were analyzed. In the IPN synthesis, first polyurethane was polymerized thermally, and then polystyrene was polymerized by photolytic methods at different temperatures. The permeability coefficient decreased and the separation factor increased with decreasing synthesis temperature due to the miscibility increase. The permeability coefficient showed a minimum value and the separation factor showed a maximum value at ca.25 wt.% polyurethane composition. The permeability coefficient decreased and the separation factor increased with increasing aromatic content in polyurethane component. The morphology and density behavior of the IPN's agreed well with the permeability data. The tensile strength of the membrane increased with decreasing synthesis temperature and with increasing crosslink density and polystyrene content.     

Degradation of epoxidized polyenes in the presence of phthalic acid

Viscometry was used to follow the epoxidation of polybutadiene and styrene–butadiene triblock copolymers (SBS) with monoperoxyphthalic acid (MPPA). Long reaction periods lead to an abnormal increase and then drop in reduced viscosity. The increasing viscosity is due to repulsion between oxirane group and its ring-opening product with phthalic acid, while the viscosity drop can be correlated with a decrease of molecular weight. Long-term storage of the epoxidized polyenes in the reaction solution containing phthalic acid, which is the derived product from MPPA, also leads to the dramatic decrease in molecular weights. The occurrence of degradation was confirmed by GPC analysis of molecular weight and molecular weight distribution. Chloroform accelerated the degradation reaction, possibly through the generation of hydrochloric acid. The degraded products were isolated and analyzed by GPC and NMR. A free radical mechanism was proposed for the oxidative degradation of epoxidized polyenes after excessive reaction.     

Synthesis,Characterization and Properties of Novel Amphiphilic Phosphated Ionomers by Ring‐Opening Reaction of Epoxidized Styrene‐Butadiene‐Styrene Triblock Polymer

A method for synthesis of novel phosphated ionomer of (styrene‐butadiene‐styrene) triblock polymer (SBS) from epoxidized SBS was developed. The optimum conditions for the ring‐opening reaction of the epoxidized SBS with aqueous solution of disodium hydrogen phosphate were studied. It was found that during the ring‐opening reaction phase transfer catalyst, ring‐opening catalyst and pH regulator were necessary to enhance the conversion of epoxy groups to ionic groups. The products were characterized with Fourier Transform Infrared Spectrophotometry (FTIR) and transmission electron microscopy (TEM). Some properties of the phosphated ionomer were studied. With increasing ionic groups or the ionic potential of the cation of the ionomer, the water absorbency emulsifying volume and the intrinsic viscosity of the ionomer increase, whereas the oil absorbency decreases. The ionomer possesses excellent emulsifying property, as compared with the sulfonated ionomer. The disodium phosphated ionomers in the presence of 10% zinc stearate showed better mechanical properties than the original epoxy SBS. Optimum mechanical properties occurred at the ionic group content of 0.95 mmol/g ionomer. When the ionomer was blended with crystalline polypropylene, a synergistic effect occurs with respect to the tensile strength. The ionomer behaves as a compatibilizer for blending equal amount of SBS and oil‐resistant chlorohydrin rubber (CHR) to form an oil resistant thermoplastic elastomer. SEM microphotographs indicated enhanced compatibility between the two components of the blend in the presence of the ionomer.     

Thermal dehydrochlorination of poly(vinyl chloride)—epoxidized butadiene/styrene triblock copolymer blends

The effect of the type of epoxidized butadiene/styrene block copolymer [ESBS; linear (B/S) or radial (E(B/S)_n), containing 0–27% of epoxy groups] on the thermal dehydrochlorination of poly (vinyl chloride) (PVC)-ESBS blends (ESBS content 10%) was investigated in the temperature range 170–180 °C, under a non-oxygen atmosphere. Thermal stability of the PVC-ESBS blends was estimated on the basis of induction time, t₀, and maximum rate of hydrochloride emission, V_max from the system. It was found that, for a similar degree of epoxidation of the SBS copolymer, the induction time i.e. the time after which emission of HCl begins, is longer in the series PVC < PVC-SBS < PVC-EB/S < PVC-E(B/S)_n, and the same is true for thermal stability. However, the maximum rate of emission of HCl is lowest in the case of PVC-EB/S blends, in the range of molar ratios from 0.5 to 2.0 × 1O⁻². On the basis of the dependence V_max = f(EB/VC), it was found that there is a certain content of epoxidized butadiene (EB) units in a mixture which causes the optimum stability of poly (vinyl chloride) during heating. During thermal destruction of the PVC-ESBS blends, the HC1 evolved undergoes addition both to epoxy fragments and to double bonds. The degree of conversion of EB units in time t₀ is 20% at 170 °C and 30% at 180 °C. The glass transition temperature, T_g, of PVC in the PVC-ESBS blends shifts towards higher temperatures by about 6–8 °C, proving the existence of crosslinking processes during moulding of the blends. The epoxidized butadiene/styrene radial block copolymer, E(B/S)_n, is a better thermal stabilizer of PVC than the linear EB/S copolymer.     

Morphology and mechanical properties of styrene–butadiene–styrene/poly(methyl methacrylate–co-n-butyl acrylate) interpenetrating polymer networks

A series of interpenetrating polymer networks (IPNs) based on styrenic triblock copolymer, polystyrene-b-polybutadiene-b-polystyrene (SBS), and random copolymer of methyl methacrylate (MMA) and n-butyl acrylate (nBA) were prepared. Corresponding semi-IPNs of the same composition without a crosslinking agent were also synthesized for comparison, and toluene was used as a common solvent to investigate the influence of the presence of the common solvent during the IPN synthesis. Throughout the compositions of IPNs tested, SBS appears to form a continuous phase and the domain size decreases gradually with the increase in SBS concentration. IPNs are found to have finer domain sizes than semi-IPNs because of the higher intermixing between polymers. The microstructure of SBS could be observed using highly magnified transmission electron microscopy (TEM). The dynamic mechanical behavior of the IPNs shows the inward shifting of two glass transition peaks, corresponding to polybutadiene phase of SBS and p(MMA–co-nBA) phase respectively, which indicates enhanced intermixing. The increase in loss tangent of styrene blocks of SBS by the addition of common solvent indicates the structural change of the microstructure in SBS, and this structural change can also be confirmed through the observation of the morphology of SBS-rich phase with higher magnification. © 1997 John Wiley & Sons, Ltd.     

Characterization of 6FDA‐based hyperbranched and linear polyimide–silica hybrid membranes by gas permeation and 129Xe NMR measurements

Physical and gas transport properties of novel hyperbranched polyimide–silica hybrid membranes were investigated and compared with those of linear‐type polyimide–silica hybrid membranes with similar chemical structures. Hyperbranched polyamic acid, as a precursor, was prepared by polycondensation of a triamine, 1,3,5‐tris(4‐aminophenoxy)benzene (TAPOB), and a dianhydride, 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA). 6FDA‐TAPOB hyperbranched polyimide–silica hybrids were prepared using the polyamic acid, water, and tetramethoxysilane (TMOS) by sol–gel reaction. 5% weight‐loss temperature of the 6FDA‐TAPOB hyperbranched polyimide–silica hybrids determined by TG‐DTA measurement considerably increased with increasing silica content, indicating effective crosslinking at polymer–silica interface. CO₂, O₂, N₂, and CH₄ permeability coefficients of the 6FDA‐based polyimide–silica hybrids increased with increasing silica content. In addition, CO₂/CH₄ selectivity of the 6FDA‐TAPOB–silica hybrids remarkably increased with increasing silica content. From ¹²⁹Xe NMR analysis, characteristic distribution and interconnectivity of cavities created around polymer–silica interface were suggested in the 6FDA‐TAPOB–silica hybrids. It was indicated that size‐selective separation ability is effectively brought by the incorporation of silica for the 6FDA‐TAPOB hyperbranched polyimide–silica hybrid membranes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 291–298, 2006     

A novel acrylonitrile–butadiene–styrene/poly(ethylene glycol) membrane: preparation,characterization, and gas permeation study

Polymeric membranes were prepared by blending different grades of poly(ethylene glycol) (PEG) as the added polymer with acrylonitrile–butadiene–styrene as the backbone structure. The membranes were characterized by Fourier transform infrared, X‐ray diffractometry, dynamic mechanical thermal analysis, differential scanning calorimetry, and scanning electron microscopy. Furthermore, the gas permeation and separation properties of CO₂/CH₄ were studied. In addition, the effect of pressure (1–8 bar) and the effect of PEG content (0–40 wt%) on CO₂ and CH₄ permeability/selectivity were investigated. The results showed that, in more cases, with the introduction of PEG molecules, CO₂/CH₄ selectivity increases without significant changes in CH₄ permeability, indicating that the incorporation of intermolecular interaction is suitable for the separation of gas pairs with no molecular size domination but the solution–diffusion. From the viewpoint of gas separation applications, the resultant data are in the commercially attractive region. Copyright © 2011 John Wiley & Sons, Ltd.     

Gas separation properties of aromatic poly(amide-imide) membranes

Aromatic poly(amide-imide)s were synthesized using direct 2,2-bis[N-(4-carboxyphenyl)-phthalimidyl] hexafluoropropane (6FDIA) polycondensation with various diamines containing flexible ether groups and bulky substituents. The oxygen and nitrogen gas transport in the poly(amide-imide) membranes was investigate at 35 °C with the pressure between the interval at 2-10 atm. The proposed method is expected to promote the gas permeability of the poly(amide-imide) membrane and maintain the gas selectivity. It was found that both gas permeability and selectivity of poly(amide-imide) membranes increased with increasing fractional free volume and d-spacing. The gas permeability had good correlation with the γ-transition temperature. The bulky pendent group introduced into diamine moiety of poly(amide-imide) could efficiently promote the gas permeability. For the behaviors of gas separation, the gas diffusivity coefficient and solubility selectivity controlled the gas permeability and selectivity, respectively. The sorption behavior of the aromatic poly(amide-imide) membranes can be well explained using the dual mode sorption model. The Langmuir capacity constant and Henry’s law constant increase with FFV increasing. 6F-TBAPS has the best O₂/N₂ separation performance among the poly(amide-imide) membranes.     

Novel nanocomposite membranes prepared with PVC/ABS and silica nanoparticles for C<Subscript>2</Subscript>H<Subscript>6</Subscript>/CH<Subscript>4</Subscript> separation

Composite membranes based on polyvinyl chloride and acrylonitrile butadiene styrene (ABS) copolymer have been prepared and then filled with 2–8 wt % of silica nanoparticles. Membranes were fabricated by solution casting method using dimethylacetamide. The performance of prepared membranes were studied for methane and ethane at the feed pressure of 1.0, 1.5, 2.0, and 3.0 bar at 35°C. By increasing the percentage of ABS, permeability of methane and ethane increased. In addition, by adding the silica nanoparticles in the membrane, permeability of gas increased in all cases. The highest gas pair selectivity for C₂H₆/CH₄ could be obtained from PVC/BS (20 wt %) which loaded with 8 wt % of silica nanoparticles. The results of this study suggest that high performance gas separation nanocomposite membranes can be attained by adopting a judicious combination of blending technique for polymeric membrane, optimized loading percentage, and feed operating conditions.     

Peroxide-Initiated crosslinking of styrene-grafted polymers and copolymers of butadiene

Low molecular weight polymers and copolymers of butadiene were grafted with styrene. The graft products were then crosslinked by using dicumyl peroxide as initiator. The optimum peroxide concentration was established (5 phr). Infrared analysis showed that the reactivity of 1,2-vinyl and that of 1,4-trans double bonds in styrene-grafted polybutadiene is similar. Crosslinking of the graft product seems to involve a radical-chain polymerization of double bonds in the polymer. The reaction rate is proportional to the square root of peroxide concentration and to the concentration of polymer double bonds. Activation energy, reaction heat, reaction order, and crosslinking efficiency were also determined from DSC measurements. No relation was found between the activation energy of crosslinking and the molecular weight of backbone polymer or density of grafting. Crosslinking efficiency was to 25–50 crosslinks per molecule of decomposed peroxide. The crosslinking efficiency for grafted butadiene–styrene copolymers is somewhat lower than that for grafted polybutadienes. From thermogravimetric measurements it was found that the crosslinked grafted polymers show lower resistance to thermal degradation than ungrafted polymers.     

Crazing in thin films of styrene–butadiene–styrene block copolymers

The mechanism of craze initiation and growth and its relationship to mechanical properties has been studied in thin films of styrene–butadiene–styrene (SBS) block copolymers. Optical microscopy and transmission electron microscopy were used to examine three copolymers which has a spherical rubber domain morphology but varied in rubber content from 20 to 50%. With increasing rubber content, the crazes became longer and less numerous. Widening of the crazes was at least partially responsible for the higher strains achieved in the copolymers, especially for the composition with the highest rubber content where the crazes widened to form micronecks. Transmission electron microscopy revealed that craze initiation and growth at the craze tip occurred by cavitation in the polystyrene phase. Cavitation of the continuous phase rather than the rubber domains was attributed to the concentration of chain-end flaws in the polystyrene. Crazes in the block copolymers followed a meandering pathway and the boundaries between crazed and uncrazed material were indistinct. Incorporation of fibrillated rubber particles into the craze fibrils strengthened the craze. At higher rubber content, the craze widened in the stress direction by voiding and fibrillation, which produced a cellular morphology.