Polypropylene Graft Research Articles

Histologic response of porcine collagen-coated and uncoated polypropylene grafts in a rabbit vagina model

The purpose of this study was to determine whether the host tissue response in the rabbit vagina differs for 2 synthetic graft materials that are used in pelvic reconstructive surgery. One strip of porcine collagen-coated or uncoated polypropylene mesh was implanted adjacent to a sham operative site into the posterior vagina of 10 New Zealand white rabbits and harvested 12 weeks later. Rabbits were assigned randomly to group 1 (coated; n = 5), group 2 (uncoated; n = 5), or group 3 (unoperated; n = 4). Full-thickness sagittal sections of posterior vaginal wall and rectum were scored for inflammation, neovascularization, and fibroblastic proliferation. Erosion of grafts did not occur in any animal. Coated and uncoated meshes induced a mild inflammatory response with minimal fibrosis and good host tissue incorporation within the grafts. Few apoptotic and proliferating cells were seen for both graft types. Both coated and uncoated polypropylene meshes elicit a mild foreign body reaction and minimal fibrotic response without evidence of vaginal epithelial erosion.

Surface and bulk properties of glycidyl methacrylate modified polypropylene: Experimental and molecular modeling studies

AbstractModifications of polypropylene (PP) are often carried out to either functionalize them or meet specific property demands. This study considered the process of PP grafting with glycidyl methacrylate (GMA) as an intermediate step to achieve improvements in surface properties of this polymer. Abundant literature is available on this grafting process but little is known about the surface properties of the grafted PP. Present work considered both experimental and computational approaches to attain this goal. Experimentally, it was established that the melting temperature of modified PP changed with the addition of GMA, and at higher concentrations of GMA in the PP matrix, heterogeneous nucleation took place. Experimental results revealed a decrease in the surface energy (SE) as well. To discern the underlying reasons behind these changes, molecular dynamics simulations were undertaken. The computational results revealed that the changes in SE could be associated with the location of the functional group. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Impact of antimicrobial prophylaxis duration on wound infection in mesh repair of incisional hernia – preliminary results of a prospective randomized trial

BACKGROUND: Surgical site infections are the second most common cause of nosocomial infections. Antibacterial prophylaxis in clean surgery is controversial; nevertheless in surgery for incisional hernia with mesh it is recommended. This study was undertaken to evaluate the impact of the duration of antimicrobial prophylaxis on the rate of wound-related infections in patients undergoing repair of incisional hernia with polypropylene mesh and in whom closed suction drains were used. Evidence-based data on this subject are lacking. METHODS: A prospective randomized study was conducted to analyze 44 consecutive patients undergoing elective surgery for abdominal incisional hernia requiring polypropylene graft and subcutaneous drains. Two patients who had inadvertent bowel entry were excluded. The remaining patients were randomly allocated into two groups: Group 1 (21 patients) was given a single dose of preoperative antibiotic prophylaxis. Group 2 (21 patients) had antibiotic cover pre- and postoperatively until the drain tubes were removed. The primary outcome measure was the occurrence of wound infection as defined according to the criteria of the Center for Disease Control. RESULTS: The groups were well matched for all variables studied. The occurrence of wound infection was 19% in Group 1 and in 33.3% in Group 2. This difference did not reach statistical significance. Most infections were mild (cellulitis and infiltrate), only in two patients purulent discharge occurred. Removal of mesh was required in one of these patients in group 1. CONCLUSIONS: Regardless of the duration of antibiotic prophylaxis, no statistically significant difference was found in wound-related complications in patients undergoing elective repair of incisional hernia with mesh and in whom subcutaneous drainage was employed. Nevertheless, a trend towards a better outcome in the single dose preoperative antimicrobial prophylaxis regimen seems to emerge. Larger studies are needed to establish firm, evidence-based guidelines.

The transient nature of maximum maleic anhydride grafting of polypropylene: A mechanistic approach based on a consecutive reaction model. II. A comparison of the batch solution and molten state processes

AbstractThis article compares the batch solution and molten state chemical modification of an atactic polypropylene to yield a grafted polypropylene. Short reaction times appear to be sufficient and indeed necessary for the highest graft yields to be obtained if degradative processes occurring in both reaction media are to be avoided. The consecutive reactions for the optimized grafting reaction pathway were proposed for the solution process in an earlier article. The present work attempts to correlate this pathway with that of the molten state process. Grafted succinic anhydride groups react with two resorcine molecules to yield grafted succinyl‐fluorescein groups. This work considers the resorcine units as true molecular probes, to be able to stabilize and activate the complexes formed between the succinic anhydride groups and the propylene sequence. This work shows the unsteady and later dynamic character of the process. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 345–351, 2007

Grafting of polypropylene and poly(vinylidene fluoride) films implanted with Ar+ ions

Polypropylene (PP) and poly(vinylidene fluoride) (PVDF) films were irradiated with 100keV Argon ions and with different fluences from 1012 up to 2×1015cm−2. PP and PVDF films were grafted with styrene and PVDF was also grafted with acrylic acid (AA). The grafting yields were determined by measuring the weight differences and analysing the Fourier transform infrared (FTIR) and UV–visible (UV–Vis) spectra. The effects on the measured grafting yields for different ion fluences and monomer concentrations were studied and are reported in this paper. The grafting yield exhibit the common feature of showing a maximum as a function of the ion fluence. To our knowledge the present work study systematically for the first time the grafting process induced by the irradiation with low energy Argon beams on the surface of PVDF and PP samples.

Cytokine production following experimental implantation of xenogenic dermal collagen and polypropylene grafts in mice

We earlier showed that xenogenic Pelvicol (Bard, Olen, Belgium) implants induce a lesser inflammatory response than Prolene (Johnson and Johnson, Dilbeek, Belgium). The purpose of this study was to determine cytokine profiles in the host immune responses to Pelvicol in a mouse model. The hypothesis was that Pelvicol would induce a "T-helper2" (Th2) rather than T-helper1 (Th1) type of inflammatory response. Mice were implanted subcutaneously with Pelvicol or Prolene and the graft sites were harvested at 3 to 28 days. Histopathology was done and cytokine levels were determined by immunohistochemistry and RT-PCR. Flow cytometry was used to identify which cell population contributed to the observed cytokine production profiles. Pelvicol induced a decreased inflammation and displayed an increase in IL-10 and TGF-beta, but reduce of TNF-alpha and IFN-gamma, indicating a Th2 type dominated response as examined by immunohistochemistry and RT-PCR. Flow cytometry showed that the monocytes/maceophages were the main cell population responsible for production of these cytokines. Monocytes/maceophages from Pelvicol explants showed upregulated expression of IL-10 while Prolene explants expressed TNF-alpha. Pelvicol induced a Th2 type cytokine-dominated immune response after subcutaneous implantation in mice.

Foaming polypropylene prepared by a novel one-step silane-grafting and crosslinking method

High-melt-strength polypropylene (HMSPP) used for foaming was prepared by a novel one-step of silane grafting and crosslinking of a normal isotactic polypropylene (IPP) in a twin-screw extruder. The HMSPP has been achieved using vinyl unsaturated silane with long chain as a grafting monomer, benzoyl peroxide (BPO) as an initiator, styrene as a coagent, trace amounts of water as a catalyst for crosslinking. The function of each agent in the formulation for the IPP modification was investigated. The results indicate that all of the agents are effective and necessary, and the proportions of the components, especially BPO, highly influenced the melt flow rate (MFR) of the HMSPP. Due to the presence of traced water in the system, the crosslinking of IPP is accompanied by the grafting of silane, which leads to a one-step production of crosslinked IPP. A high-qualified foam with uniform, closed and independent cells were fabricated from the HMSPP with appropriate MFR. With the decrement of the MFR of the HMSPP, the average size of the cells and the number of the unclosed cells decrease while the density of the cells increases.

Incisional hernia treatment with polypropylene graft: results of 10 years

To report herein our results of tension-free repair of large incisional hernia with polypropylene mesh using a modification of the method that was described by Usher. Two hundred ninety-one patients who were operated on between January 1994 and December 2004 were studied. Two hundred thirty-two patients were female (79.7%), and 59 were male (20.3%). The average follow-up period was 55 months. The patients were evaluated for infection, recurrences, hematoma and seroma formation, sinuses and enterocutaneous fistula formation. Infection was observed in eight patients (2.7%). Graft removal due to infection was encountered only in two patients (0.6%). Recurrence was observed in six patients (2.1%). Two patients (0.6%) developed hematoma while another two developed seroma. No patient developed enterocutaneous fistula. By using our modified technique we can decrease the expected complications after tension-free repair of large incisional hernias.

Investigation on preparation and property of nano‐CaCO3/PP masterbatch modified by reactive monomers

AbstractNano‐CaCO3/polypropylene (PP) masterbatch containing above 80 wt % nano‐CaCO3 was prepared by nano‐CaCO3 coated PP modified by reactive monomers. The chemical interaction, crystallization and melting behavior, thermal stability, morphology, and surface contact angle of masterbatch were investigated with IR, DSC, TEM, TGA, ESCA, and surface contact angle. The results indicated that nano‐CaCO3 was coated by PP graft copolymers in the masterbatch modified by reactive monomers. The graft ratio and crystallization and melting behavior of PP in the masterbatch depended on the type and content of reactive monomer. The crystallization temperatures of masterbatch modified by reactive monomer is methyl methacrylate > butyl acrylate > methyl acrylate ≈ mixture of acrylic acid and styrene > unmodified ≈ maleic anhydride ≈ acrylic acid > styrene. Modification by reactive monomer increased the thermal stability and surface contact angle of masterbatch. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3907–3914, 2006

Design and synthesis of structurally well-defined functional polypropylenes via transition metal-mediated olefin polymerization chemistry

Functionalization of polyolefins is an industrially important yet scientifically challenging research subject. This paper summarizes our recent effort to access structurally well-defined functional polypropylenes via transition metal-mediated olefin polymerization. In one approach, polypropylenes containing side chain functional groups of controlled concentrations were obtained by Ziegler-Natta-catalyzed copolymerization of propylene in combination with either living anionic or controlled radical polymerization of polar monomers. The copolymerization of propylene with 1,4-divinylbenzene using an isospecific MgCl2-supported TiCl4 catalyst yielded polypropylenes containing pendant styrene moieties. Both metalation reaction with n-butyllithium and hydrochlorination reaction with dry hydrogen chloride selectively and quantitatively occurred at the pendant reactive sites, generating polymeric benzyllithium and 1-chloroethylbenzene species. These species initiated living anionic polymerization of styrene (S) and atom transfer radical polymerization (in the presence of CuCl and pentamethyldiethylenetriamine) of methyl methacrylate (MMA), respectively, resulting in functional polypropylene graft copolymers (PP-g-PS and PP-g-PMMA) with controllable graft lengths. In another approach, chain end-functionalized polypropylenes containing a terminal OH-group with controlled molecular weights were directly prepared by propylene polymerization with a metallocene catalyst through a selective aluminum chain transfer reaction. Both approaches proved to be desirable polyolefin functionalization routes in terms of efficiency and polymer structure controllability.

A RAT MODEL OF POLYPROPYLENE GRAFT INFECTION CAUSED BY STAPHYLOCOCCUS EPIDERMIDIS

The aim of this study was to constitute a valid graft infection model with Staphylococcus epidermidis in rats. Rats were divided into seven groups. In groups 1 and 2, 2 cm x 2 cm polypropylene grafts were incubated with 10(8) c.f.u./mL slime-positive S. epidermidis at 37 degrees C for 2 and 24 h and were then placed subfascially to the groins of rats. In the third group, naive grafts were placed and 0.5 mL of 3 x 10(7) c.f.u. slime-positive S. epidermidis were injected on the inside of the wounds. Rifampicin (30 mg/kg) in group 4 and teicoplanin (20 mg/kg) in group 5 were applied i.p. to rats with 2-h incubated grafts for prophylaxis. The same prophylactic regimens were given to groups 6 and 7 in which rats were incubated for 24 h. At eighth day, rats were killed and wounds were assessed with macroscopic evaluation and cultures. No death occurred in any of the groups. In groups 1 and 2, 100% infection rates were achieved. However, graft infection was detected in only two (20%) of the rats in group 3 (P = 0.001). Prophylactic application of teicoplanin or rifampicin decreased the infection rates significantly in the short-incubation groups. Incubation of polypropylene grafts with slime-producing S. epidermidis for 2 and 24 h in the pre-application period achieved the occurrence of a standardized graft infection. Prophylactic use of teicoplanin and rifampicin decreased the infection rates. We propose to use this reproducible and reliable animal model of graft infection in future studies.

Synthesis of polypropylene graft copolymers from a hydroxyl‐groups‐containing polypropylene precursor via atom‐transfer radical polymerization

AbstractIsotactic polypropylene graft copolymers, isotactic[polypropylene‐graft‐poly(methyl methacrylate)] (i‐PP‐g‐PMMA) and isotactic[polypropylene‐graft‐polystyrene] (i‐PP‐g‐PS), were prepared by atom‐transfer radical polymerization (ATRP) using a 2‐bromopropionic ester macro‐initiator from functional polypropylene‐containing hydroxyl groups. This kind of functionalized propylene can be obtained by copolymerization of propylene and borane monomer using isospecific MgCl2‐supported TiCl4 as catalyst. Both the graft density and the molecular weights of i‐PP‐based graft copolymers were controlled by changing the hydroxyl group contents of functionalized polypropylene and the amount of monomer used in the grafting reaction. The effect of i‐PP‐g‐PS graft copolymer on PP‐PS blends and that of i‐PP‐g‐PMMA graft copolymer on PP‐PMMA blends were studied by scanning electron microscopy. Copyright © 2006 Society of Chemical Industry

The transient nature of maximum maleic anhydride grafting of polypropylene: A mechanistic approach based on a consecutive reaction model Part 1: Batch solution process

This article reports the chemical modification of an atactic polypropylene performed in solution. To model the process, a Box-Wilson experimental design was used, taking in to consideration the concentrations of maleic anhydride and dycumile peroxide, as well as reaction time, as independent variables. The dynamic character of the process is proposed on the basis of model forecasts supported by experimental results. The proposed kinetic pathway agrees with the fact that short reaction times are not only sufficient but necessary for the greatest graft yields to be attained, while preventing degradative processes in the system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1182–1190, 2006.

Gold and Gold-Palladium Coated Polypropylene Grafts in a S. epidermidis Wound Infection Model

The use of non-absorbable mesh grafts in both abdominal wall defects and inguinal hernias are impossible in the presence of contamination. This study was conducted for evaluation of the efficiencies of polypropylene mesh grafts coated with gold and palladium-gold. Ten piece of 1 x 2 cm of polypropylene mesh grafts were used in each group of naïve, gold-coated, and palladium-gold-coated. The grafts were incubated in physiological saline buffered and 0.5 McFarland slime positive Staphylococcus epidermidis for 24 h. At intervals of 6, 12, 24, 48, 72 h grafts were washed with saline and vortexed for 2 min in 2 ml of physiological saline. There were 100 microl of samples of vortexed material incubated in blood agar and 24 h later, colony numbers were assessed. In the second part of study, the grafts were implanted below the musculoaponeurotic layer at inguinal region of rats following the same procedure of incubation and washing. On the 8th day, the rats were examined for infection rate and their wound cultures were obtained. The least amount of bacterial growth was detected in the samples obtained from gold-palladium coated grafts; whereas the highest rate of growth was found in samples of naive grafts. The superficial surgical site infection rate was 0% in gold-palladium coated, 30% in gold-coated and 100% in naïve polypropylene group. The bacterial growth rate from wound cultures confirmed the superficial surgical site infection rates in all groups. Prosthetic graft infection with S. epidermidis can be prevented by coating the graft with gold-palladium or gold.

Synthesis of polypropylene graft copolymers by the combination of a polypropylene copolymer containing pendant vinylbenzene groups and atom transfer radical polymerization

AbstractThis article discusses a facile and inexpensive reaction process for preparing polypropylene‐based graft copolymers containing an isotactic polypropylene (i‐PP) main chain and several functional polymer side chains. The chemistry involves an i‐PP polymer precursor containing several pendant vinylbenzene groups, which is prepared through the Ziegler–Natta copolymerization of propylene and 1,4‐divinylbenzene mediated by an isospecific MgCl2‐supported TiCl4 catalyst. The selective monoenchainment of 1,4‐divinylbenzene comonomers results in pendant vinylbenzene groups quantitatively transformed into benzyl halides by hydrochlorination. In the presence of CuCl/pentamethyldiethylenetriamine, the in situ formed, multifunctional, polymeric atom transfer radical polymerization initiators carry out graft‐from polymerization through controlled radical polymerization. Some i‐PP‐based graft copolymers, including poly(propylene‐g‐methyl methacrylate) and poly(propylene‐g‐styrene), have been prepared with controlled compositions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 429–437, 2005

How organo-montmorillonite truly affects the structure and properties of polypropylene

Polypropylene (PP)/organo-montmorillonite (OMMT) nanocomposites were prepared by using a highly effective PP solid-phase graft as compatibilizer. As a very low amount of PP graft was used, the properties of the PP matrix were maintained. The effects of the OMMT on the structure and properties of PP were studied fully. The intercalated structure of the nanocomposites was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD and TEM results showed that a typical intercalated structure was formed in the composites. The results of mechanical properties showed that the impact strength and the modulus of the nanocomposites were improved significantly compared with those of the neat PP. The thermal stability and crystallization of the nanocomposites were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The thermal stability of the nanocomposites, characterized by the initial decomposition temperatures, was substantially improved compared with that of the neat PP. The DSC results showed that the crystallization temperature of nanocomposites was increased compared with the neat PP. The viscoelasticity of the nanocomposites was studies by dynamic mechanical thermal analysis (DMTA). The DMTA results showed that the OMMT could improve the modulus of PP substantially. The T g of PP was lowered by the incorporation of the OMMT. The changes of the properties were correlated with the formation of the PP/OMMT nanocomposites.

Grafting of polypropylene with N-cyclohexylmaleimide and styrene simultaneously using supercritical CO 2

Monomer mixture of styrene (St) and N-cyclohexylmaleimide (ChMI) and initiator benzoyl peroxide (BPO) were first impregnated into isotactic polypropylene (iPP) films simultaneously using supercritical carbon dioxide (SC CO 2) as a solvent and swelling agent at 35.0 °C. The composites were obtained after the monomers were grafted onto the iPP matrix at 70 °C. The effects of various conditions, such as pressure, monomer concentration, and the molar ratio of the two monomers in the soaking process, on the composition of the composites were determined. The molar ratios of St to ChMI in the composites were estimated by Fourier transform infrared spectroscopy. The thermal properties, the morphology, and the mechanical properties of the composites were characterized by different techniques. The results demonstrated that the phase size of the grafted St–ChMI was very small and the phase boundary was very ambiguous. The composites had better thermal stability than the original iPP film. The Young's modulus and tensile strength of the film increased continuously with increasing grafting percentage. The two grafted monomers in the composites had good synergetic effect.

Comparison of maleic anhydride grafting onto powder and granular polypropylene in the melt by reactive extrusion

AbstractThe grafting of powder and granular polypropylene (PP) with maleic anhydride (MA) was investigated in a reactive extrusion process with dicumyl peroxide (DCP) as an initiator. The effects of the MA and DCP contents in the feed on grafting were investigated. Under the experimental conditions applied in this study, the grafted monomer unit content was varied from 0.023 to 0.5%. The MA grafting efficiency of powder PP was higher than that obtained for the granular form of PP. In general, the grafting degree first increased with the MA or DCP content in the feed, then reached a maximum value, and finally decreased because of several possible alternative reactions during the grafting. The grafting of powder PP was more successful because of better initial mixing and less diffusional resistance during the grafting. An increase in the MA content in the feed caused significant reductions in the melt‐flow index of the graft copolymers. The results obtained with Fourier transform infrared, differential scanning calorimetry, and X‐ray powder diffraction analyses indicated that the structure, macrotacticity, crystallinity, crystallization, and thermal behavior of PP changed with grafting and depended on the grafting degree. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3675–3684, 2004

Properties and biocompatibility of polypropylene graft copolymer films.

Modifying the surfaces of polymers has received a great deal of attention, because it could bring about specific surface characteristics such as antithrombogenic property. Therefore, N-vinyl pyrrolidone/sodium acrylate (NVP/Na-AAc) binary monomers were introduced onto polypropylene (PP) films by a radiation grafting method. The effect of solvent and comonomer composition on the degree of grafting was determined. Studies of the mechanical properties and water content of such graft copolymers showed that as the grafting yield increases the elongation percent decreases. However, the water content increases with increasing grafting yield. The blood compatibility of the original PP and PP-g-NVP/Na-AAc films was evaluated by determination of the extent of platelet adsorption and thrombus formation. The blood compatibility of PP-g-NVP/Na-AAc seems to be better than that of original PP.

Polypropylene–graft–maleic anhydride-nanocomposites: I—Characterization and thermal stability of nanocomposites produced under nitrogen and in air

The morphology and thermal behaviour of polypropylene–graft–maleic anhydride (PP–g–MA) layered silicate (montmorillonite) nanocomposites were investigated using X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and thermogravimetry. The study focuses on the influence of the presence of oxygen during the preparation of PP–g–MA–nanocomposite using two different modified clays. The nanocomposites show tactoid, intercalated and exfoliated structures side by side with different dominant states depending on the clay used and on the processing conditions. The systems are described as multi-component blends rather than binary blends since the organic ions do not only change the mixing behaviour, but also influence material properties. Beside the physical barrier property of the clay layers also chemical processes were found to play an important role.