In vivo evaluation of a new composite mesh (10% polypropylene/90% poly-<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid) for hernia repair

The increasing use of mesh insertion for groin hernia repair is dashed by a worrying prevalence of chronic pain frequently related as a reaction to the biomaterial implantation. Thus, new biocompatible prosthesis, designed as a composite material associating polypropylene (PP) and long-term absorbable material, are now under development. In the present study, the typical commercially available Prolene mesh has been compared to two new meshes designed with 3-fold less PP, either alone (light PP) or associated with poly-L-lactic acid (PP-PLA) accounting for 90% of the mesh weight. These PP-mesh variants were implanted in an extraperitoneal position within the abdominal wall of 90 rats. Mesh adhesion and size were determined at autopsy 2, 4 and 8 weeks after implantation (10 animals per group) and morphometric parameters of the host tissues by light microscopy. Prolene and light PP-meshes presented intra-corporeal shrinkage and tissue adhesion, both more pronounced with light-PP, whilst PP-PLA meshes were not affected in spite of a strongest fibrosis. In contrast to Prolene and even more with light PP meshes, inflammation and cell-mediated immune responses were reduced without occurrence of angiogenesis or oedema. All these findings advocate together for a better tolerance of this new composite biomaterial, more likely due to a low macrophage response that appeared statistically correlated to the absence of mesh shrinkage and to a decreased adhesion to the tissue. On the basis of these experimental observations, it could be expected that the better tolerance of this composite biomaterial may avoid both long-term pain and recurrence when used as plug in groin hernia repair.     

Evaluation of the acute scarring response to the implant of different types of biomaterial in the abdominal wall

Since the short-term, acute scarring process induced by a biomaterial may condition the evolution of the repair process, the present investigation evaluates the behavior of polytetrafluoroethylene (PTFE) and polypropylene (PL) biomaterials in the initial stages of repair. Three PTFE biomaterials (Mycro Mesh^®, Dual Mesh^® and Soft Tissue Patch^®) and one PL biomaterial (Marlex^®) were employed to repair defects created in the abdominal wall of New Zealand rabbits. Animals were sacrificed at 3 or 7 days. Specimens were obtained for light and scanning electron microscopy, and immunohistochemical analysis using the RAM-11 monoclonal antibody for rabbit macrophages. The PL implants showed substantial adhesion formation with viscera. Lower adhesion formation was detected in the PTFE implants. The evolution of the acute phase of the repair process was similar for each PTFE biomaterial. At 3 days post implant, an incipient neoperitoneum was detected which was fully established after 7 days. The behavior of the PL implant was similar, although a greater amount of reticular granulation was detected. The neoformed peritoneum was irregular. Few RAM-11-labeled macrophages were detected in all cases. The acute phase of the tissue repair process induced by the implant of PTFE and PL biomaterials generally proceeds along similar lines to a normal repair process. However, the use of microporous, laminar materials seems to favor the early establishment of a well-defined neoperitoneal layer.     

A new type of polytetrafluoroethylene prosthesis (Mycro Mesh): an experimental study

Comparisons were made of the tissue response to the implantation of two different polytetrafluoroethylene prostheses: Soft Tissue Patch (STP) and Mycro Mesh (MM). A 7 × 5 cm prosthesis of STP (n=12) or MM (n=12) was implanted into a defect of the same size (involving all layers except skin) created in the anterior abdominal wall in 24 New Zealand rabbits. The prostheses were anchored to the recipient tissue, in direct contact with the intestinal loops and connective tissue. After 14, 30, 60 and 90 days, groups of six implants were studied macroscopically and samples were taken to be processed by light microscopy, scanning electron microscopy (SEM), immunohistochemical studies and tensiometry. All animals were valid for the study. In three cases STP implants presented very loose adhesions in the peripheral zones corresponding to the sutures. They were also observed on three MM implants, in the area of the perforations. Light and scanning microscopy revealed the formation of a capsule of scar tissue surrounding both types of prosthesis. At day 90, bridges of connective tissue had formed in the perforated areas of MM. Good vascularization was established in the areas of recipient tissue corresponding to both implants. The macrophage reaction to both biomaterials was maximal at 14 days, after which it progressively decreased until day 90. Tensile testing revealed no significant differences between the two biomaterials. It is concluded that (a) behaviour in the peritoneal interface is similar in the two prostheses, (b) both biomaterials become encapsulated rather than integrated into the recipient tissue, (c) the foreign body reaction does not determine the success or failure of the implants, (d) The perforations of the MM prosthesis do not increase its resistance to stress, or at least not after 90 days of implantation into rabbit abdominal wall.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September.     

Interface formed between visceral peritoneum and experimental polypropylene or polytetrafluoroethylene abdominal wall implants

The objective of this work was to study the healing process at the interface between biomaterial and visceral peritoneum. Implants of polytetrafluoroethylene (ePTFE) and polypropylene prostheses were introduced into the abdominal wall of New Zealand rabbits. The behaviour of the biomaterials was analysed using light and scanning electron microscopy and immunohistochemistry in which a specific anti-rabbit macrophage monoclonal antibody (RAM 11) was employed. According to macroscopic observation, there was significantly fewer adhesions prosthesis-viscera to ePTFE than to polypropylene implants. After ePTFE implantation, restoration of the peritoneum took place in an orderly fashion. When polypropylene was used, the peritoneum formed was a disorderly tissue in which small areas of haemorrhage and necrosis could be seen to coincide with the appearance of adhesions. The number of labelled macrophages peaked 14 days after ePTFE or polypropylene implantation, after which it decreased gradually. It is concluded that, given the low rate of adhesion provoked by PTFE, this material is ideal for implants contiguous to the peritoneal cavity viscera. The macrophage response does not determine the use of one material or the other. The structure of the newly formed peritoneum and development of adhesions depends on the porosity of the biomaterial.     

Bioactive glass granules and polytetrafluoroethylene membrane in the repair of bone defects adjacent to titanium and bioactive glass implants

An experimental animal model was used to investigate the effect of bioactive glass (BG) granules and nonresorbable polytetrafluoroethylene (PTFE) membrane on the repair of cortical bone defects adjacent to titanium and BG implants. Thirty-two Astra® (diameter 3.5 mm) dental implants were inserted bicortically and 42 conical BG implants (diameter 2.5–3.0 mm) monocortically, into fitted holes of rabbit tibia. Before implantation, a standardized bone defect was created by drilling an extra hole (diameter 3.0 mm) adjacent to each implant site. Twenty-eight defects were filled with BG granules (diameter 630–800 m) (BG group) and 28 defects were left empty but covered with PTFE membrane (PTFE group). No material was used in 18 control defects (control group). Morphometrical evaluation with a digital image analysis system was used to measure bone repair as percentages of the defect area on scanning electron microscopy (SEM) and light microscopy pictures. Bone–implant contact was measured as percentages of the thickness of the cortical bone. At 6 and 12 wk, bone repair in defects in connection with titanium implants was 23.2% and 36.6% in the BG group, 23.2% and 32.4% in the PTFE group, and 47.2% and 46.2% in control defects. Corresponding figures for BG implants were 33.2% and 40.1% in the BG group, 16.6% and 33.5% in the PTFE group, and 25.7% and 54.9% in control defects, BG granules and new bone together filled 82.7% and 68.5% of the defect area adjacent to titanium implants, and 75.9% and 74.4% of the defect adjacent to BG implants at 6 and 12 wk, respectively. Better bone–implant contact was achieved at the defect side with BG than titanium implants (77.0% versus 45.0% at 12 wk). The results indicate that BG granules are useful in treatment of bone defects adjacent to dental implants. BG coating of the implant seems to improve osseointegration in the defect area.     

Characterising and modelling variability of tow orientation in engineering fabrics and textile composites

Variability of tow orientation is unavoidable for biaxial engineering fabrics and their composites. Since the mechanical behaviour of these materials is strongly dependent on the fibre direction, variability should be considered and modelled as exactly as possible for more realistic estimation of their forming and infusion behaviour and their final composite mechanical properties. In this study, a numerical code, ‘VariFab’, has been written to model realistic full-field variability of the tow directions across flat sheets of biaxial engineering fabrics and woven textile composites. The algorithm is based on pin-jointed net kinematics and can produce a mesh of arbitrary perimeter shape, suitable for subsequent computational analysis such as finite element forming simulations. While the shear angle in each element is varied, the side-length of all unit cells within the mesh is constant. This simplification ensures that spurious tensile stresses are not generated during deformation of the mesh during forming simulations. Variability is controlled using six parameters that can take on arbitrary values within certain ranges, allowing flexibility in mesh generation. The distribution of tow angles within a pre-consolidated glass–polypropylene composite and self-reinforced polypropylene and glass fabrics has been characterised over various length scales. Reproduction of the same statistical variability of tow orientation as in these experiments is successfully achieved by combining the VariFab code with a simple genetic algorithm.     

Tissue engineering approach to repair abdominal wall defects using cell-seeded bovine tunica vaginalis in a rabbit model

The aim of this study was to engineer skeletal muscle tissue for repair abdominal wall defects. Myoblast were seeded onto the scaffolds and cultivated in vitro for 5 days. Full thickness abdominal wall defects (3 × 4 cm) were created in 18 male New Zealand white rabbits and randomly divided into two equal groups. The defects of the first group were repaired with myoblast-seeded-bovine tunica vaginalis whereas the second group repaired with non-seeded-bovine tunica vaginalis and function as a control. Three animals were sacrificed at 7th, 14th, and 30th days of post-implantation from each group and the explanted specimens were subjected to macroscopic and microscopic analysis. In every case, seeded scaffolds have better deposition of newly formed collagen with neo-vascularisation than control group. Interestingly, multinucleated myotubes and myofibers were only detected in cell-seeded group. This study demonstrated that myoblast-seeded-bovine tunica vaginalis can be used as an effective scaffold to repair severe and large abdominal wall defects with regeneration of skeletal muscle tissue.     

A new composite made of polyurethane and glass ceramic in a loaded implant model: a biomechanical and histological analysis

The biocompatibility and osseous integration of a new composite material made of polyurethane and a calcium silicophosphate ceramic was investigated in a loaded implant model in sheep and compared to that of commercially pure titanium. Six months after implantation, interfacial shear strength was higher between the titanium and bone than between the composite and bone. After 2 years, however, the shear strength was significantly higher in the composite group. Histologically, both implants were surrounded by bone and fibrous tissue and there were no signs of inflammation. Direct contact of bone on the composite surface increased significantly with time, whereas there was no time-dependent increase of bone contact on titanium. It can be concluded that the biocompatibility and osseous integration of the composite was very good in the loaded implant model used. It is therefore suggested that the new composite is a promising biomaterial for orthopaedic implants.     

Interfacial and biological properties of the gradient coating on polyamide substrate for bone substitute

Fabrication of bioactive and mechanical matched bone substitutes is crucial for clinical application in bone defects repair. In this study, nano-hydroxyapatite/polyamide (nHA/PA) composite was coated on injection-moulded PA by a chemical corrosion and phase-inversion technique. The shear strength, gradient composition and pore structure of the bioactive coating were characterized. Osteoblast-like MG63 cells were cultured on pure PA and composite-coated PA samples. The cells'' adhesion, spread and proliferation were determined using MTT assay and microscopy. The results confirm that the samples with the nHA/PA composite coating have better cytocompatibility and have no negative effects on cells. To investigate the in vivo biocompatibility, both pure PA and composite-coated PA cylinders were implanted in the trochlea of rabbit femurs and studied histologically, and the bonding ability with bone were determined using push-out tests. The results show that composite-coated implants exhibit better biocompatibility and the shear strength of the composite-coated implants with host bone at 12 weeks can reach 3.49 ± 0.42 MPa, which is significantly higher than that of pure PA implants. These results indicate that composite-coated PA implants have excellent biocompatibility and bonding abilities with host bone and they have the potential to be applied in repair of bone defects.     

Expression of heat shock protein 70 (HSP70) at the interface of polymer–implants in vivo

Synthetic polymer meshes are widely applied in the modern surgical approach for repairing abdominal wall defects. The implanted material is often observed leading to post-operative complications such as deficient abdominal wall mobility and adhesion formation with the abdominal cavity and/or abdominal organs. However, the functioning of the implant is primarily affected by the wound healing process guided by inflammatory events occurring at the tissue–material interface. This could presumably be influenced by the physicochemical properties of the polymer. With regard to it, the cellular and molecular processes involved in the successful restoration of the abdominal wall function are poorly understood. The present in vivo study, therefore, exemplary investigated in a rat model, the commercially available polymer-meshes Prolene® (polypropylene, PP), Mersilene® (polyester, PE) and Vicryl® (polyglactin 910), as well as new mesh variants consisting either of PP (EB) or a combination of PP and polyglactin 910 (A plus or Vypro®). The implanted material was evaluated by light and electron microscopy, immunohistochemistry as well as morphometry over an implantation period of 90 days. The data show that polymers induce heat shock protein (HSP)70, and its expression at the interface correlates inversely with the activity of the inflammatory reaction in vivo. Further, an ascent in HSP70 expression parallels the increasing implantation period and evolving foreign-body granulomas. Accordingly, a major role for HSP70 in modulating the local acceptance of polymers and as an additional marker for in vivo testing of polymers is suggestive. ©©2000 Kluwer Academic Publishers     

Evaluation of the tissue reaction to a percutaneous access device using titanium fibre mesh anchorage in goats

The tissue reaction to a percutaneous access device, applicable as a carrier for an implantable glucose sensor, was evaluated in goats. Titanium fibre mesh structures were used for anchorage of the device in superficial as well as deeper soft-tissue locations. The percutaneous part was subcutaneously anchored with a fibre mesh sheet. The distal part was placed intraperitoneally and anchored in deeper soft-tissue layers using a fibre mesh cuff. All implants showed good healing with the surrounding tissue. Histological evaluation showed that the subcutaneous fibre mesh sheets and peritoneal fibre mesh cuffs were filled with immature connective tissue, generally free of inflammation. Problems concerning disconnection of the silicone catheter from the titanium holding element and filling of part of the peritoneal fibre mesh cuff with silicone glue have to be overcome by more appropriate preclinical testing and improved implant design. Our results demonstrate that titanium fibre mesh structures can be used effectively for soft-tissue anchorage of percutaneous access devices. A sufficient ingrowth of connective tissue was obtained in superficial as well as in deeper soft-tissue layers. The access device could have application as a carrier for an implantable glucose sensor for glucose monitoring in different tissue compartments.     

Polymers in hernia repair–common polyester vs. polypropylene surgical meshes

Within the last years meshes have become essential for the repair ofabdominal wall hernias. While the type of mesh obviously influencesthe clinical result, the selection of the best suitablemesh-modification should have favourable effects onto the rate ofcomplications. Available surgical meshes mainly differ in the typeand amount of the basic polymers. The most common meshes are madeeither out of monofilament polypropylene (PP) or multifilamentpolyester (PET). In the following contribution we studied thefunctional and histological results of standard and commerciallyavailable surgical meshes: a standard heavyweight, large pore-sizedPP-mesh (Prolene®), a heavyweight, large pore-sized PET-mesh(Parietex®, coated with bovine collagen) and a low weightsmall pore-sized PET-mesh (Mersilene®) in a standardised ratmodel. The meshes are studied by three dimensional stereography,tensiometry, light-(LM) and transmission electron microscopy (TEM),as well as morphometry over implantation intervals of 3, 7, 14, 21and 90 days. The results proved marked differences between thetested meshes in regard to textile properties, the mechanicalfunction (tensile strength, abdominal wall mobility), as well as thehistologically proved tissue reaction. Both heavyweight meshes (PPand PET) revealed an enormous and most similar strength whereas thelow weight PET-mesh primarily showed a considerable increase offlexibility. Despite their different structures and their diversehistological response all tested meshes led to a similar andsignificant reduction of the abdominal wall flexibility. However, thelocal tissue response of the interface mesh/recipient tissuesrevealed a significant reduction of the acute inflammatory activity anda significant decrease of connective tissue formation in the case ofthe low weight PET-mesh Mersilene® compared to both heavyweightmesh-modifications. Mersilene® showed an excellent andrelatively inert tissue reaction of the interface compared toProlene® and Parietex®. Modifications of the mesh-structure(e.g. larger pores) should improve the functional results, inparticular, abdominal wall flexibility. However, the use of PET inhernia surgery is at least questionable in respect to the obligatelong-term degradation of this polymer.     

Short term tissue response to carbon fibre: A preliminaryin vitro andin vivo study

Carbon in the form of pyrolytic carbon coating is used in a number of implantable medical devices. Carbon-reinforced carbon composite and other forms of diamond-like carbon coatings are being evaluated for their many potential biomedical applications. There is also a possibility of using carbon in fibre form. Though the possibility of using the fibre form of carbon in skeletal and dental implants has been recognized, a detailed study of tissue reaction to carbon fibre has not been reported so far. In this paper, we describein vitro andin vivo evaluation of carbon fibre in bone and muscle. Good cell and tissue biocompatibility of the material was observed in bone and muscle. New bone was present in contact with the fibres. Results of this study indicate that carbon fibre has potential in non-load bearing applications, such as skeletal repair and as ligament prosthesis.     

Preparation of a biphasic scaffold for osteochondral tissue engineering

Tissue engineering has been developed as a prospective approach for the repair of articular cartilage defects. Engineered osteochondral implants can facilitate the fixation and integration with host tissue, and therefore promote the regeneration of osteochondral defects. A biphasic scaffold with a stratified two-layer structure for osteochondral tissue engineering was developed from biodegradable synthetic and naturally derived polymers. The upper layer of the scaffold for cartilage engineering was collagen sponge; the lower layer for bone engineering was a composite sponge of poly(DL-lactic-co-glycolic acid) (PLGA) and naturally derived collagen. The PLGA–collagen composite sponge layer had a composite structure with collagen microsponge formed in the pores of a skeleton PLGA sponge. The collagen sponge in the two respective layers was connected. Observation of the collagen/PLGA–collagen biphasic scaffold by scanning electron microscopy (SEM) demonstrated the connected stratified structure. The biphasic scaffold was used for culture of canine bone-marrow-derived mesenchymal stem cells. The cell/scaffold construct was implanted in an osteochondral defect in the knee of a one-year old beagle. Osteochondral tissue was regenerated four months after implantation. Cartilage- and bone-like tissues were formed in the respective layers. The collagen/PLGA–collagen biphasic scaffold will be useful for osteochondral tissue engineering.     

Tissue response to hafnium

The aim of the present experimental study was to evaluate the tissue response to hafnium (Hf) a reactive metal closely related to titanium (Ti) and zirconium (Zr). Hf has not been previously evaluated as implant material in a biologic environment. In a first experiment, 21 machined Hf non-threaded implants (test) and 21 similar Ti implants (control) were inserted in the abdominal wall of 21 rats. Animals were sacrificed after 8 days (6 rats), 6 (7 rats) and 12 weeks (8 rats). In a second experiment, 18 rabbits received 18 Hf and 18 Ti threaded implants in their tibiae, one implant in each tibia. The rabbits were sacrificed after 6, 12 and 24 weeks (6 animals/time interval). The bulk metal of the abdominal wall implants, embedded together with the surrounding tissue, was electrolytically dissolved and semithin (1 m) sections of the intact tissue–implant interface were evaluated by light microscopy (morphometry). Bone-implant contact and bone area within threads were evaluated in ground sections. In soft tissues, a fluid space containing predominantly monocytes/macrophages surrounded the abdominal implants at 8 days. At 6 and 12 weeks, a fibrous capsule, consisting of layers of macrophages and fibroblasts, surrounded the implants. Macrophages, including multinuclear giant cells, always formed the innermost layer in contact with the implant surface. No quantitative or qualitative difference in the tissue organization was detected between Ti and Hf implants. In rabbits, 6 weeks after insertion, the proximal two threads located within the cortical bone were filled with bone in contact with Hf and Ti. The distal threads contained bone marrow. After 12 and 24 weeks, mature bone was present in the proximal 3–4 implant threads. No statistically significant difference was found between Hf and Ti implants at any time periods. It is concluded that Hf is an interesting metal for biomedical applications in bone and soft tissue. © 2001 Kluwer Academic Publishers     

Novel Approach of Semiconductor Manufacturing Process on Copper Dual Damascene Processes Integration

Abstract:  The performance of the manufacturing process in each of these areas determines the overall manufacturability of the process. As device geometries are reduced, understanding and minimising the sources of process-induced defects is critical to achieving and maintaining high device yields. This paper presents a comprehensive investigation of a novel metrology on semiconductor process module integration and technology on optimal integrated lithography processes and solution to the problem of defects reduction on semiconductor wafer in sub-micron processes integration. As dual damascene integration copper process is complicated and critical in semiconductor processes. It has been common knowledge that pattern collapse and missing of this process and numerous defects could be prevented by optimal the process module tuning. To investigate novel semiconductor process integration on deep pattern aspect ratio effects of sub-micron semiconductor wafer BEOL (Back-End-Of-Line) structure were included in this study. Moreover, the electrical device investigations of device checking were also included.     

Studies of the healing of bone grafts, and the incorporation of titanium implants in grafted bone: an experimental animal model

An insufficient quality and amount of bone often necessitate the clinical use of implants together with bone transplants. The present study describes an experimental animal model for the study of implants in bone grafts. Circular defects were made bilaterally in the tibia of 36 rabbits. The defects received either autologous cortical bone (control), demineralized bone matrix (DBM), plasma-augmented DBM or were left empty (without bone graft). In all defects a titanium implant was centrally placed and anchored in the opposite cortex. Evaluation with light microscopic morphometry showed that the insertion of a threaded titanium implant centrally in a cortical defect was followed by a spontaneous healing of the defect after 6 mon. After 6 wk, all implants in cortical grafts were well integrated with a significantly higher bone-to-implant contact than in the DBM and plasma-augmented groups. After 6 mon, all experimental groups had a mean bone area within the threads ranging between 69% and 80% and a mean bone-to-implant contact between 31% and 42%. The results from the present study indicate that the model allows comparative studies on the early formation, resorption and remodelling of bone around implants after modification of implant, graft and host properties.     

Optimal design of customised hip prosthesis using fiber reinforced polymer composites

The need for new materials in orthopaedic surgery arises from the recognition of the stress-shielding effect of bone by high-modulus implants presently made of engineering alloys. A lower modulus implant material will result in the construction of a more biomechanically compatible prosthesis. In this respect, composite materials are gaining importance because they offer the potential for implants with tailor-made stiffness in contrast to metals. In the present study, the bending stiffness of composite prosthesis is matched with that of bone in both the longitudinal and radial directions by choosing optimal carbon fiber reinforced polyether ether ketone (PEEK) matrix lay-up. A numerical optimization algorithm is developed to deduce the optimal composite femoral prosthesis lay-up that matches the stiffness properties of the femoral bone in both the transverse and longitudinal directions. Effective bending moments and compressive forces acting on the hip joint are considered in the design of the optimal length and diameter of the prosthesis. The optimization algorithm was implemented, by using MATLAB(R)™ for designing the composite prosthesis to a patient’s specific requirement. Finally the efficiency of the composite stem is compared with that of metallic alloy stems in terms of stress shielding using a finite element program.     

Stress relaxation tests in polypropylene monofilament meshes used in the repair of abdominal walls

The objective of this work has been to characterize stress relaxation in the polymer material on applying different levels of constant strain. The meshes were strained at values of 5.2%, 5.4% and 5.6% which are the values at which the mesh is strained in clinical use for the repair of abdominal walls. Laws have been obtained to model the viscoelastic behavior at different strains for this material. Finally, fracture studies were carried out by environmental scanning electron microscopy to determine the fracture mechanisms of these meshes. Besides, the implantation of the meshes was practised in two different layers of abdominal wall: the superficial or preaponeurotic layer and deep or preperitoneal layer, showing the neoformation of connective tissue on the mesh, which tended to be organized differently in each layer studied; more roughly and densely in the superficial layer than in the deep one.     

管道修复用涤纶-苎麻复合机织物性能试验

针对传统管道内衬修复材料施工中易出现内壁塌陷等问题,结合目前快速发展的绿色纤维复合材料,提出在涤纶机织物内衬材料中加入苎麻纱线,制作涤纶-苎麻复合机织物材料来提高树脂对管道修复用内衬机织物的浸透性能,增强内衬材料和管壁的粘结性能。以纤维外观、抽拔实验后纤维断面形貌的电镜观察,并通过树脂与织物接触角的测试、粘结实验,综合分析了涤-麻复合机织物的树脂浸透性,同时对涤纶-苎麻复合机织物力学性能进行测试来保障内衬复合材料满足强度的要求。实验结果表明,采用上述涤-麻复合织造的方法,可以显著提高树脂的浸透性能,有利于携带更多的树脂粘结剂提高树脂与管壁的粘结性,减少塌陷发生的可能性。同时加入麻复合的机织物,拉伸顶破性能都满足高压燃气管道的修复要求。