Progress in the Degradability of Biodegradable Film Materials for Packaging.

In today's world, the problem of "white pollution" is becoming more and more serious, and many countries have paid special attention to this problem, and it has become one of the most important tasks to reduce polymer waste and to protect the environment. Due to the degradability, safety, economy and practicality of biodegradable packaging film materials, biodegradable packaging film materials have become a major trend in the packaging industry to replace traditional packaging film materials, provided that the packaging performance requirements are met. This paper reviews the degradation mechanisms and performance characteristics of biodegradable packaging film materials, such as photodegradation, hydrodegradation, thermo-oxidative degradation and biodegradation, focuses on the research progress of the modification of biodegradable packaging film materials, and summarizes some challenges and bottlenecks of current biodegradable packaging film materials.

Research Progress of Polyvinyl Alcohol Water-Resistant Film Materials.

Polyvinyl alcohol (PVA) is one of the few biodegradable synthetic resins from petroleum-based sources that can alleviate white pollution in the environment. PVA film materials have excellent properties, such as high barrier, high transparency, high toughness, biocompatibility, and adjustable water solubility. However, due to the presence of hydrophilic hydroxyl groups in the side chain of PVA resin, when PVA film is placed in a humid or water environment, swelling or even dissolution will occur, which greatly limits its application. Therefore, it is necessary to modify PVA resin to improve water resistance without reducing other properties and can also impart various functionalities to it, thereby widening the application range. This paper reviews the water-resistant modification methods of polyvinyl alcohol and the application of water-resistant films and provides an outlook on the development trend of PVA water-resistant films.

Comparative Study on Water Vapour Resistance of Poly(lactic acid) Films Prepared by Blending, Filling and Surface Deposit.

The polylactic acid (PLA) resin Ingeo 4032D was selected as the research object, with a focus on PLA modification by using polymers such as linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) and ethylene-propylene-diene monomer grafted with glycidyl methacrylate (EPDM-g-GMA), by using fillers such as nano calcium carbonate and zeolite. In order to characterize the deposition effect of Al2O3 on the film surface by plasma-assisted atomic layer deposition, Bio-oriented PLA (BOPLA) with more uniform thickness than blown film was purchased for study. The mechanical properties, friction coefficient, surface contact angle and water vapour transmission rate of the modified PLA film were compared and discussed. The aim was to find out the most influencing factors of film's water vapour resistance.

Effects of Processing Conditions and Plasticizing-Reinforcing Modification on the Crystallization and Physical Properties of PLA Films.

The polylactic acid (PLA) resin Ingeo 4032D was selected as the research object. Epoxy soybean oil (ESO) and zeolite (3A molecular sieve) were used as plasticizer and reinforcing filler, respectively, for PLA blend modification. The mixture was granulated in an extruder and then blown to obtain films under different conditions to determine the optimum processing temperatures and screw rotation. Then, the thermal behaviour, crystallinity, optical transparency, micro phase structure and physical properties of the film were investigated. The results showed that with increasing zeolite content, the crystallization behaviour of PLA changed, and the haze of the film increased from 5% to 40% compared to the pure PLA film. Zeolite and ESO dispersed in the PLA matrix played a role in toughening and strengthening. The PLA/8 wt% zeolite/3 wt% ESO film had the highest longitudinal tensile strength at 77 MPa. The PLA/2 wt% zeolite/3 wt% ESO film had the highest longitudinal elongation at 13%. The physical properties depended heavily on the dispersion of zeolite and ESO in the matrix.

Covalent functionalization of boron nitride nanosheets via reductive activation.

Hexagonal boron nitride is well known for its unique structure and excellent physical properties, particularly in hexagonal boron nitride nanosheets (BNNSs) with high potential in multiple technological applications. However, its severe layer-by-layer aggregation and incompatibility with processing liquids or condensed phase materials pose a great challenge. Covalent functionalization of BNNSs has been a common approach to address these critical issues, yet it is extremely difficult to carry out due to the chemical inertness of BNNSs. In this study, we report a novel and general route to covalently functionalize BNNSs via a simple reduction reaction. This involves initial negative charging through effective reductive activation which enables subsequent reactions with various organic alkyl halides. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) results confirm that linear alkyl chains with varying lengths are successfully grafted onto BNNSs, which leads to matched compatibility with organic media and the exfoliation level of few-layer thickness. The increase of the alkyl chain length considerably promotes their solubility in organic solvents with iodoalkanes as the most efficient grafting agents. Incorporation of alkylated BNNSs into a polymer matrix at low filler loadings leads to significant enhancements in mechanical properties over neat polymers, suggesting their exceptional reinforcement for polymer nanocomposites. This facile and scalable reductive chemistry route is applicable to versatile chemical modifications of BNNSs with diverse functional groups and grafting agents by reactions with suitable electrophiles.

Functionalized Boron Nitride Nanosheets/Poly(l-lactide) Nanocomposites and Their Crystallization Behavior.

In this work, hydroxyl-functionalized boron nitride nanosheet (OH-BNNS) was prepared and was blended with poly(l-lactide) (PLLA) to yield PLLA/OH-BNNS nanocomposites with excellent dispersion of OH-BNNS via the interaction of carbonyl in PLLA and hydroxyl in OH-BNNS. The effects of OH-BNNS on the crystallization and melting behaviors, isothermal crystallization kinetics, macroscopic crystal morphology and crystal structure of PLLA were studied by means of various techniques. The addition of OH-BNNS nanofillers can effectively accelerate the crystallization of PLLA and enhance the nucleation density, leading to a smaller spherulite size, increased crystallinity, a more obvious crystallization peak upon cooling but weakened cold crystallization behavior upon heating. Low OH-BNNS loading can increase the relative content of α-crystal, but the relative content of less perfect α'-crystal is increased at high OH-BNNS loading due to the strong interaction between PLLA and OH-BNNS.

[Arterial blood gas and electrolytes in severe pulmonary tuberculosis with respiratory failure: analysis of 50 cases].

OBJECTIVE: To study the characteristics of arterial blood gas and electrolytes in patients with severe pulmonary tuberculosis with respiratory failure. METHOD: In 50 patients with severe pulmonary tuberculosis, the arterial blood gas and electrolytes were measured after the onset of respiratory failure to define the types of respiratory failure and acid-base imbalance. RESULTS: Severe pulmonary tuberculosis with respiratory failure was characterized by development of hypoxia, and the degree of hypercapnia may vary; more extensive tuberculous involvement or longer disease course suggest greater chance of type II respiratory failure. Increment of the anion gap occurred irrespective of the pH value. CONCLUSION: Analysis of arterial blood gas and electrolytes may help monitor the progression of severe pulmonary tuberculosis and provides valuable information for implementing treatment and making prognostic decisions.

[Delayed diagnosis or misdiagnosis of pulmonary tuberculosis: 458 cases clinical analysis].

OBJECTIVE: To explore the reason of delayed diagnosis or misdiagnosis of pulmonary tuberculosis. METHOD: The clinical data of 458 patients pulmonary tuberculosis patients undergoing treatment between January 1999 and December 2003 in our hospital were retrospectively analysed. RESULTS AND CONCLUSION: The reasons for delayed diagnosis or misdiagnosis are as follows: A careless attitude towards health condition by patients themselves; neglected bacteriological evidence or ignorance of tuberculosis by physicians.

[A study of the psychological and social factors in patients with pulmonary tuberculosis].

OBJECTIVE: To investigate the mental health and social support in patients with tuberculosis. METHODS: Questionnaires were performed in 132 patients with tuberculosis and 71 healthy volunteers using Symptom Checklist 90 (SCL-90) and Social Support Rating Scale (SSRS). Statistical analyses were processed using Student's t test and ANOVA test. RESULTS: Somatization, obsessive-compulsiveness, anxiety, phobic anxiety and paranoid ideation, psychotism and the mean of positive factors of SCL-90 of the tuberculosis group (1.77 +/- 0.51, 1.63 +/- 0.50, 1.53 +/- 0.51, 1.33 +/- 0.41, 1.40 +/- 0.45, 1.41 +/- 0.40 and 36.07 +/- 20.84, respectively) were significantly higher than those of the control group (1.30 +/- 0.49, 1.43 +/- 0.49, 1.38 +/- 0.65, 1.24 +/- 0.48, 1.49 +/- 0.69, 1.30 +/- 0.44 and 24.92 +/- 18.22, respectively) (all P < 0.01). The result of symptom self-check differed among patients with different educational levels. The SSRS results of subjective and objective supports and total score of social supports of the tuberculosis group were 6.90 +/- 2.81, 19.25 +/- 5.62 and 32.96 +/- 7.86, respectively, much lower than those of the control group (7.92 +/- 2.57, 21.54 +/- 5.82 and 36.51 +/- 9.01, respectively) (all P < 0.01). Subjective support of patients with smear positive tuberculosis was much lower than that of patients with smear negative disease (18.15 +/- 5.72 vs. 20.75 +/- 5.78, P < 0.05); Subjective support, objective support and total score of social support of the unmarried patients (17.19 +/- 4.20, 6.17 +/- 2.18, 30.35 +/- 5.96, respectively) were lower than those of the married (20.72 +/- 5.96, 7.66 +/- 3.03, 35.19 +/- 8.74, respectively) (all P < 0.01). The results of SCL-90 and SSRS had no statistical relationship. CONCLUSION: Our results suggest that the disordered mental conditions and lower social support in patients with tuberculosis need psychosocial interventions in addition to medical care.