Structure Analysis and Its Correlation with Mechanical Properties of Microcellular Polyamide Composites Reinforced with Glass Fibers.

Thin-walled and thick-walled microcellular moldings were obtained by MuCell® technology with nitrogen as a supercritical fluid. 2 mm thick polyamide 6 (PA6) with 30% wt. glass fiber (GF) samples were cut from automotive industrial elements, while 4 mm, 6 mm, and 8.4 mm thick moldings of PA6.6 with 30% wt. GF were molded into a dumbbell shape. The internal structure was investigated by scanning electron microscopy (SEM) and X-ray computed microtomography (micro-CT) and compared by numerical simulations for microcellular moldings using Moldex3D® 2022 software. Young's modulus, and tensile and impact strength were investigated. Weak mechanical properties of 2 mm thick samples and excellent results for thick-walled moldings were explained. SEM pictures, micro-CT, and simulation graphs revealed the tendency to decrease the cell size diameter together with increasing sample thickness from 2 mm up to 8.4 mm.

Processing and Mechanical Properties of Highly Filled PP/GTR Compounds.

Ground rubber from automobile tires is very difficult to recycle due to the cross-linking of the macromolecules and thus the lack of thermoplastic properties. The research consisted of assessing the processing possibility via the injection of highly filled PP/GTR compounds modified with 1.5 wt.% 2.5-dimethyl-2.5-di-(tert-butylperoxy)-hexane. GTR dosing ranged from 30 wt.% up to 90 wt.%. The evaluation of the processing properties of the obtained materials was carried out on the basis of the melt flow index test results and the signals recorded during processing by the injection molding by temperature and pressure sensors placed in the mold. The influence of the applied modifier on the changes in the mechanical properties of PP/GTR was determined with hardness, impact and static tensile tests. Moreover, thermal properties were obtained by the differential scanning calorimetry method. It has been found that it is possible to efficiently process compounds with high GTR content using injection molding. The presence of the filler allows to significantly reduce the cooling time in the injection mold and thus the time of the production cycle. It has been confirmed that 2.5-dimethyl-2.5-di-(tert-butylperoxy)-hexane modifies the rheological properties of PP and thus the PP/GTR composition. The lower viscosity of the matrix results in a more accurate bonding with the developed surface of the GTR grains, which results in better mechanical properties of the rubber-filled polypropylene.

The Impact of Selected Laser-Marking Parameters and Surface Conditions on White Polypropylene Moldings.

Laser marking of polymer materials is a technology that is increasingly used in industry. Polypropylene (PP) shows a low ability to absorb electromagnetic radiation in the near-infrared range (λ = 1064 nm). The paper presents the influence of the surface condition of white-colored polypropylene moldings on the efficiency of their marking with a laser beam. In addition, the operation of the commercial laser marking additive (LMA) Lifolas M 117009 UN, intended to support the process of laser marking of polyolefin surfaces, was verified. The study is an attempt to combine laser operating parameters, material, and geometric properties of PP moldings to obtain the expected quality of graphic symbols. The test samples were made by injection molding method with the use of a specially designed modular injection mold. The molding cavities were prepared with various methods of metal processing, thanks to which obtained moldings differed in surface condition. The marking effects were assessed based on colorimetric tests and digital image analysis. The 0.5 wt% LMA content resulted in obtaining a graphic sign with high contrast in comparison to the background. The gradual increase in the modifier content resulted in a further increase in contrast. These values depended on the degree of surface finish of the samples, and therefore on the roughness parameters. Samples with a rough surface finish showed higher contrast compared to surfaces with a high surface finish. It was also found that for the analyzed moldings, the laser-marking process should be performed with the use of a low head velocity (450-750 mm/s) and a high concentration of the laser beam (0.03-0.05 mm).

Analysis of the Innovative Channel Strut Concept Manufactured by Roll-Forming.

Due to the wide use of channel strut components, manufacturing is implemented in many industrial plants. Standard technology of profiles is based on welding of two parts of the profile and requires the regalvanizing of the joint zone causes. Thus, the production is challenging to automate on a single line. The main idea of the article is to present a concept of a channel strut, a cold-formed continuous metal component with an open or closed profile section. It would serve as a cantilever support instead of a standard solution. In the article, a unique lock system combination is proposed and analyzed both numerically and experimentally to provide steadiness of the strut without welding or other joining techniques. Two main lock shapes-semicircular and triangle-were proposed with some variations in the cutting plane. Analyses were carried out for three main profile cross-sections with different dimensions, based on the current industrial applications. The semicircular type of the lock was found to be the most stable, giving optimal strength to the strut under assumed loading, comparable to traditional solutions. The commercial FEM software MSC Marc was used for the numerical analysis.

Influence of Extruder's Nozzle Diameter on the Improvement of Functional Properties of 3D-Printed PLA Products.

The dynamic growth of the use of polymer construction parts manufactured individually and in a small series makes it necessary to improve additive methods in the areas of materials, equipment and processes. By observing selected phenomena occurring during the processing of polymer materials in other production technologies (e.g., extrusion and injection molding), it is possible to obtain solutions that positively affect the final performance properties of the products obtained in additive manufacturing technologies using thermoplastic filament. The aim of this research was to determine the effect of the diameter of the print head nozzle on the spatial structure (path width) and selected mechanical properties of samples produced by the FFF method with PLA material. The obtained results were compared to the samples with a solid structure produced using injection molding technology. In the experiment, the RepRap device for additive manufacturing was used, with the use of nozzles with diameters of 0.2 mm, 0.4 mm, 0.8 mm and 1.2 mm. The test objects were produced with a layer height of 0.2 mm, full filling (100%) and with constant remaining printing parameters. The conducted research allowed us to conclude that the use of layer heights lower than the standard ones gives favorable results for selected mechanical properties. The use of an extruder nozzle diameter of 0.8 mm allows one to obtain a macrostructure with a high degree of interconnection of layers and paths and favorable mechanical properties. The test results can be used in the construction of functional elements that are produced by fused deposition modeling (FDM) and fused filament fabrication (FFF) methods in prototype, unit and small-lot production.

Modification of Laser Marking Ability and Properties of Polypropylene Using Silica Waste as a Filler.

Polypropylene (PP) belongs to the group of polymers characterized by low susceptibility to absorption of electromagnetic radiation in the infrared range (λ = 1064 nm). This research consisted of assessing the possibility of using silica waste from the metallurgic industry as an additive for PP laser marking. The modifier was introduced into the polymer matrix in the range from 1 to 10 wt%. The effects of laser radiation were assessed based on colorimetric tests and microscopic surface analysis. The mechanical properties of the composites were determined during the static tensile tests. The thermal properties were investigated via differential scanning calorimetry. It was found that the introduction of silica waste into polypropylene allows for the effective marking of sample surfaces with the use of a laser beam. The greatest contrast between the graphic symbol and the background was obtained for silica contents of 3 and 5 wt%, with the use of a low-speed laser head and a strong concentration of the laser beam. The application of silica caused an increase in the modulus of elasticity and the tensile strength of the composite samples. Increases in the crystallization temperature and the degree of crystallinity of the polymer matrix were also observed. It was found that silica waste can act as multifunctional additive for polypropylene.

High-Performance of a Thick-Walled Polyamide Composite Produced by Microcellular Injection Molding.

Lightweight moldings obtained by microcellular injection molding (MIM) are of great significance for saving materials and reducing energy consumption. For thick-walled parts, the standard injection molding process brings some defects, including a sink mark, warpage, and high shrinkage. Polyamide 66 (PA66)/glass fiber (GF) thick-walled moldings were prepared by MuCell® technology. The influences of moldings thickness (6 and 8.4 mm) and applied nitrogen pressure (16 and 20 MPa) on the morphology and mechanical properties were studied. Finally, the microcellular structure with a small cell diameter of about 30 µm was confirmed. Despite a significant time reduction of the holding phase (to 0.3 s), high-performance PA66 GF30 foamed moldings without sink marks and warpage were obtained. The excellent strength properties and favorable impact resistance while reducing the weight of thick-walled moldings were achieved. The main reason for the good results of polyamide composite was the orientation of the fibers in the flow direction and the large number of small nitrogen cells in the core and transition zone. The structure gradient was analysed and confirmed with scanning electron microscopy (SEM) images, X-ray micro computed tomography (micro CT) and finite element method (FEM) simulation.

The Microcellular Structure of Injection Molded Thick-Walled Parts as Observed by In-Line Monitoring.

The aim of the study was to detect the influence of nitrogen pressure on the rheological properties and structure of PA66 GF30 thick-walled parts, produced by means of microcellular injection molding (MIM), using the MuCell® technology. The process was monitored in-line with pressure and temperature sensors assembled in the original injection mold. The measured data was subsequently used to evaluate rheological properties inside an 8.4 mm depth mold cavity. The analysis of the microcellular structure was related to the monitored in-line pressure and temperature changes during the injection process cycle. A four-times reduction of the maximum filling pressure in the mold cavity for MIM was found. At the same time, the holding pressure was taken over by expanding cells. The gradient effect of the cells distribution and the fiber arrangement in the flow direction were observed. A slight influence of nitrogen pressure on the cells size was found. Cells with a diameter lower than 20 µm dominate in the analyzed cases. An effect of reduction of the average cells size in the function of distance to the gate was observed. The creation of structure gradient and changes of cells dimensions were evaluated by SEM images and confirmed with the micro CT analysis.

The Impact of Laser Radiation on Polypropylene Molded Pieces Depending on Their Surface Conditions.

The article presents an analysis of the impact of a laser beam interaction (Nd: YVO4) with selected operational parameters on the quality of graphical marks obtained on the surfaces of polypropylene-molded pieces with different surface textures (variable parameters of the surface layer). Polypropylene test specimens were produced by injection using the original injection mold, which allowed for the obtainment of products with variable surface finish parameters determined by the surface condition of the forming cavity. The presented relationship between the parameters of laser performance, the texture of a molded piece surface, the molded piece's color, and types of masterbatches supporting the marking process allows for the assessment of the efficiency of graphic symbol application by laser marking. The original evaluation criteria for the conducted process were adopted.

Assessment of Abdominal Belts Impact on the Lungs Ventilation and Their Application in Early Physiotherapy after Major Abdominal Surgery - Prospective Trial.

UNLABELLED: Early physiotherapy is an important part of the comprehensive treatment of patients after major abdominal surgery (MAS). Accelerated mobilization should be safe and requires the use of appropriate techniques. Most of the physiotherapists and surgeons recommends using abdominal belts. Opponents claim that belts have an adverse effect on lungs ventilation. The aim of the study was to determine the effect of abdominal belt on lung ventilation efficiency in the early period after MAS. MATERIAL AND METHODS: The study involved 20 patients after MAS. Including 9 women and 11 men, aged between 40 to 90 years (x̅ 66.7). In the scheduled 7 patients and urgent 13. All of them were in the early period after surgery. Dynamic spirometry was performed twice in the postoperative period. For the first time wearing a belt, and then without the belt in the same group. Evaluated the forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and peak expiratory flow (PEF). For the analysis uses the Wilcoxon matched-pairs test and Spearman's rank correlations. P values <0.05 were considered significant. RESULTS: The value of the ventilation indicators measured wearing abdominal belt were slightly lower than the values evaluated without the belt. The results are shown in percent predicted for age and gender, FEV wearing belt 52%, without belt 53%; FEV1 59% vs 61%; PEF 46% vs 51%. There were no statistically significant differences Conclusions. There were no significant negative influence of abdominal belt on lungs ventilation in early period after MAS. There was no correlations between age, body mass index and changes in ventilation indicators.

The usefulness of anorectal manometry in patients with a stoma before and after surgery to restore the continuity of the gastrointestinal tract.

UNLABELLED: The operation to restore the continuity of the gastrointestinal tract is another surgical intervention in a given patient, which directly translates into an increased risk of complications during and after surgery. That is why proper qualification is important for the operation to restore the continuity of the gastrointestinal tract in terms of performance and efficiency of the anal sphincter apparatus, among other things. The aim of the study was to evaluate the effect of restoring physiological defecation routes on the sphincter function and to observe the parameters of anorectal manometry in patients before and after surgery to restore the continuity of the gastrointestinal tract. MATERIAL AND METHODS: The study included 29 patients scheduled for restoration of the continuity of the gastrointestinal tract, 12 women and 17 men. The average age in the group was 62 years. Anorectal manometry was performed both before surgery as well as one month and three months afterwards in all patients. The average time to have a stoma was 12 months. RESULTS: The resting pressure in the anal canal (MRP) three months after the restoration of the continuity of the gastrointestinal tract increased by 30.4%. The maximum systolic blood pressure in the anal canal (MSP) increased by 22.2%. The value of recto-anal inhibitory reflex (RAIR) decreased by 19.2%. The length of the high pressure zone in the anal canal (HPZL) increased by 27%. The study results of visceral rectal sensation thresholds decreased by 23.3% for the sensation threshold, and 14.4% for the pressure threshold. CONCLUSIONS: Restoring the continuity of the gastrointestinal tract improves the anal sphincter function which is evident in the parameters of anorectal manometry. The restoration of passage improves the sphincter function, and these changes are statistically significant.

Use of the TIMP in Assessment of Motor Development of Infants With Down Syndrome.

PURPOSE: Infants with Down syndrome (DS) who are admitted to rehabilitation centers are several weeks old, and the tests that they undergo are often not specific enough to highlight the main developmental disorders in the first postnatal trimester. The aim of this study was to assess the possibility of using the Test of Infant Motor Performance (TIMP) to examine motor development of children with DS. METHODS: Using the TIMP, 141 infants, including 64 infants with DS, with a mean age of 9.4 weeks, were examined. The control group represented 77 infants without developmental disorders, with a mean age of 10.0 weeks. RESULTS: The results show that children with DS achieve lower TIMP scores in comparison with children without developmental disorders. CONCLUSIONS: The TIMP is a sensitive measure of delayed motor development in infants with DS and can be used to confirm the need for therapy.

New minimally invasive technique of parastomal hernia repair - methods and review.

INTRODUCTION: Parastomal hernia is described as the most common complication in patients with ostomy. It is reported that its incidence varies from 3% to 39% for colostomies and 0 to 6% for ileostomies. Surgical repair remains the treatment of choice. There are three types of surgical treatment - fascial repair, stoma relocation and repair using prosthetic mesh via a laparoscopic or open approach. Recently there have been several meta-analyses and systematic reviews aiming to compare the results of surgical treatment, and the authors agreed that the quality of evidence precludes firm conclusions. AIM: To describe the novel concept of parastomal hernia repair - HyPER/SPHR technique (hybrid parastomal endoscopic re-do/Szczepkowski parastomal hernia repair) and its early results in 12 consecutive cases. MATERIAL AND METHODS: Twelve consecutive patients were operated on due to parastomal hernia using the new HyPER hybrid technique between June 2013 and May 2014. The patients' condition was evaluated during the perioperative period, 6 weeks and then every 3 months after surgery. RESULTS: After 6 weeks of follow-up we have not observed any mesh-related complications. All 12 patients were examined 3 months and 6 months after repair surgery for evaluation. No recurrence, stoma site infection or stoma-related problems were found. None of the patients complained of pain and none of them needed to be hospitalized again. Reported quality of life on a 0-10 scale after 6 weeks of follow-up was 8 (range: 7-10). CONCLUSIONS: The HyPER procedure for treatment of parastomal hernias proposed by the authors is a safe and feasible surgical technique with a high patient satisfaction rate and a low number of complications. The hybrid procedure seems to be a promising method for parastomal hernia repair.

Physiotherapy based on PNF concept for elderly people after conventional colon surgery.

UNLABELLED: Aging population, increases the number of major abdominal surgery (MAS) performed in the elderly. Main goal of physiotherapy after that surgery is prevention postoperative complications and reduction of functional limitation. The aim of the study was to asses functional status elderly people after MAS during early postoperative physiotherapy. MATERIAL AND METHODS: In a prospective randomized study involved 34 patients scheduled for elective MAS, aged 65+. Patients were randomly assigned to receive PNF or conventional physiotherapy. The study included forced spirometry (FVC, FEV1, PEF) and functional tests (gait speed, up&go). Measurements were performed before surgery and the fourth day after surgery. Also analyzed age, sex, BMI and the level of postoperative independence (postoperative independence scale SAP). Kolmogorow- Smirnow test was used to check normal distribution, t-Student was used to check whether two sets of data differ significantly, and r-Pearsons for correlations testing. p values <0.05 were considered significant. RESULTS: After surgery the time of gait speed test and up and go test was significant longer in comparison to preoperative value. FVC%, FEV1%, PEF% values was decrease. In the PNF group was found significantly higher postoperative independence(SAP) and shorter length of stay in hospital compared to conventional physiotherapy group. Results of SAP and functional tests were significantly positive correlated. CONCLUSIONS: Major abdominal surgery decrees efficiency of walking and lung ventilation after 65 year old in early postoperative period. Some techniques of the PNF concept used in improving older patients after the MAS may favourably affect the postoperative increase independence and reduce the time of hospitalization.