| HS Kodu | 689888 |
| Kimyasal Adı | polivinil alkol |
| Kimyasal Formül | (C2H4O) n |
| Cas Numarası | 9002-89-5 |
| Fiziksel Durum | Katı granül veya toz |
| Dış Görünüş | Beyaz ile krem renkli |
| Suda çözünürlük | Suda çözünür (sıcak su tercih edilir; çözünürlük hidroliz derecesine bağlıdır) |
| Hidroliz Derecesi | Genellikle %87-89 veya %98-99 |
| Yoğunluk | 1.19 - 1.31 g /cm³ |
| Erime Noktası | 180 - 230 ° C |
| Cam Geçiş Sıcaklığı | 60 - 85 ° C |
| çekme Dayanımı | Sınıf ve film hazırlığına bağlı olarak 20 - 60 MPa |
| Kopma Uzaması | Plastifikatör ve nem içeriğine bağlı olarak% 100 - 300 |
| Biyobozunurluk | Mikrobiyal eylem yoluyla aerobik/anaerobik koşullarda biyolojik bozulabilir |
| Biyolojik Bozulma Zaman Toprak Içinde | Toprak koşullarına, film kalınlığına ve PVA sınıfına bağlı olarak birkaç haftadan aya kadar |
| Degradasyon ürünler | Karbon dioksit ve su (tam biyolojik bozulma altında) |
| Toksisitesi Olmayan | Toprak mikroorganizmaları ve bitkileri için toksik olmayan ve güvenli |
| Film Kalınlığı Aralığı | Mulç filmleri için tipik 10 - 50 mikrometre |
| Uv Direnci | Orta derecede; genellikle uzun süreli açık UV maruz kalma için katkı maddeleri gerektirir |
Akrediteli bir Biyobozulabilir Tarım Mulç için Polivinil Alkol (PVA) fabrikası olarak, her seri tutarlı etkinlik ve güvenlik standartlarını sağlamak için sıkı testlerden geçiyor.
| Paketleme | 20 kg nem dayanıklı kraft torbaları ile polietilen astarı ile tedarik edilir, biyolojik bozulabilir tarım malç kullanımı için açıkça etiketlenen. |
| Konteyner Yükleme (20' FCL) | 20 'FCL biyolojik bozulabilir malç için polivinil alkol ile yüklenmiş, paletli, güvenli ve güvenli taşıma için korunmuştur. |
| Nakliye | PVA granüllerini mühürlenmiş, nem dayanıklı torbalarda veya toplu konteynerlerde gönderin. Kaplamayı önlemek için uzun süreli nem maruz kalmaktan kaçının. Etkinlik kaynaklarından uzak, serin ve kuru bir alanda saklayın. Taşıma için tehlikeli bir sınıflandırma yok, ancak akıntıları önlemek için güvenli yükler. Standart yük ve tarım tedarik zincirleri ile uyumluluğu sağlamak. |
| Depolama | Polivinil Alkolu (PVA) doğrudan güneş ışığı ve nemden uzak, serin, kuru, iyi havalandırılmış bir alanda saklayın. Hidrasyon veya keklemeyi önlemek için konteynerleri sıkıca mühürleyin. Ortam sıcaklıklarını 30 ° C'nin altında tutun. Güçlü oksidatörlerle temas etmekten kaçının. Polimer bütünlüğünü ve malç bozulma performansını korumak için uygun etiketleme ve kuru koşulları sağlayın. |
| Raf ömrü | Raf ömrü: genellikle nem ve doğrudan güneş ışığından uzak serin, kuru bir yerde saklandığında 2 yıl. |
Bir 40:1 L/D oranına ve ters dönen karıştırma vidalarına sahip çift vidalı bir ekstrüder, genellikle kısmen hidroliz edilmiş PVA'nın (87-89 mol% hidroliz, DP 1700-2000) gliserol ve suyun geçici co-plastifikatörler olarak birleştirilmesi için yapılandırılmıştır. Temel formül 70 wt% PVA, 20 wt% gliserol ve 10 wt% deiyonlaştırılmış sudan oluşur, homojen emilimi elde etmek için 40 °C'de yüksek hızlı bir karıştırıcıda 20 dakika önceden karıştırılır. Ekstrüder varil sıcaklıkları, besleme bölgesinde 140 °C dan kalıpta 175 °C kadar ayarlanır ve ısıl bozulmayı önlemek için 190 °C altında bir erime sıcaklığı tutulur. Deventilasyon bölgesindeki bir vakum havalandırma, aşırı nemi çıkarır ve pelletli reçinede 2-4 wt% son su içeriğini hedeflir. Bileşik peletler, oluklu bir besleme bölümü ve 150 mm çapındaki 0.8-1.2 mm bir kalıp boşluğu ile donatılmış tek vidalı üflenmiş film hattına beslenir. Kalıp sıcaklıkları 175–180 °C tutulur ve 2.5–3.0 bir patlama oranı uygulanır. Oksidatif bozulmayı engellemek için kalıp dudak bölgesinin azot temizlenmesi gerekir. Oluşan film, 10-15 µm kalınlığı ile, 30-38 MPa (ASTM D882) bir çekme dayanımı ve 250% 'yi aşan bir kırılma uzunluğu sergiler. Bitmiş bir malç olarak, bu şeffaf film toprak sıcaklığını çıplak toprağa göre 3-6 ° C yükseltir ve salata ve salatalık gibi sezon erken sebze üretimi için kullanılır. Topraktaki tam biyolojik bozulma, EN 17033:2018, özellikle ≥%90, ISO 17556, OECD 208, OECD 208, ISO 17556, ISO 17556, ISO 17556, ISO 17556, ISO 17556, ISO 17556, ISO 17556, ISO 17556 Çalışma sınırları: <0,5% nem bileşimden önce PVA granüllerinin önceden kurutulması %60 üzerindeki ortam nisbi nemde zorunludur ve ekstrüderdeki kalma süresi 120 saniyeyi aşmamalıdır film gücünü tehlikeye atan moleküler ağırlık azaltmasını önlemek için.
Bütçenize uygun rekabetçi Biyobozulabilir Tarım Mulç için Polivinil Alkol (PVA) fiyatları - her sipariş için esnek şartlar ve özelleştirilmiş teklifler.
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Commercial PVA resins supplied for biodegradable agricultural mulch are predominantly partially hydrolyzed grades with residual acetyl content between 2 mol% and 12 mol%. The model designation typically encodes the viscosity and hydrolysis level: a grade marked PVA 1788 denotes a 4 wt% aqueous solution viscosity of 17±1 mPa·s at 20°C and a hydrolysis degree of 88±1 mol%. Fully hydrolyzed grades such as 1799 (>99 mol%) are unsuitable as the primary matrix in soil-contact films because their dissolution temperature exceeds 95°C, retarding biodegradation initiation beyond practical field timeframes. In contrast, 0588 (viscosity 5.5 mPa·s) provides low-molecular-weight chains that yield rapid cold-water solubility but compromise blown-film bubble stability unless coextruded or blended with higher-viscosity fractions. Gelation in aqueous environments occurs above a critical concentration that shifts with the degree of hydrolysis: for PVA 1788 at 20°C, the gel point lies near 12 wt%, whereas for PVA 1799 the same transition appears below 6 wt%. These solubility characteristics govern the initial fragmentation of mulch film in moist soil, making grade selection a precise lever for controlling the lag phase before microbial assimilation.
The fundamental difference is the primary degradation trigger: PVA films undergo hydrolytic chain scission coupled with dissolution, independent of enzymatic hydrolysis as the rate-limiting step, whereas thermoplastic starch (TPS) blends rely on amylase activity and polylactic acid (PLA) on ester hydrolysis that is kinetically frozen below its glass transition of ≈58°C. Consequently, PVA mulch can begin fragmenting within 6–10 weeks after incorporation into soil at 15°C and 60% water-holding capacity, while PLA mulch remains dimensionally stable for multiple growing seasons under identical conditions. Polybutylene adipate-co-terephthalate (PBAT), often marketed as the flexible component in biodegradable mulches, exhibits a comparable degradation onset to PVA but lacks the cold-water solubility pathway; its hydrolysis requires depolymerase activity and proceeds more slowly at temperatures below 20°C. A further distinction is the behaviour of PVA in anaerobic soil zones: the polyvinyl alcohol backbone can be metabolized by Pseudomonas and Sphingomonas species under both aerobic and nitrate-reducing conditions, a metabolic versatility not shared by PLA, which demands oxygenated compost environments to meet disintegration criteria under ISO 17088:2012. This positions PVA films as viable for no-till and minimum-till systems where soil contact is immediate and oxygen partial pressure at the soil–film interface fluctuates.
Mechanical property profiles also diverge sharply. PVA film conditioned at 50% RH exhibits a tensile strength of 30–45 MPa and elongation at break of 150–250% (ASTM D882), comparable to PBAT but substantially more ductile than pure PLA. Starch-blend films, even with plasticiser contents up to 25 wt%, rarely exceed 12 MPa tensile strength and suffer embrittlement at relative humidity below 30%. This means PVA mulch withstands mechanical laying on undulating terrain without pre-wetting, a common failure mode for starch-based sheets at planting speeds above 6 km/h on commercial tractor-drawn mulch layers (e.g., Forigo Roter Italia RM series). The critical difference for growers, however, is the absence of persistent microplastic residues: PVA’s water-soluble fraction ensures that film fragments smaller than 2 mm are dissolved or metabolised rather than accumulating as secondary microplastics, a documented concern with PBAT and PLA fragments in soils where composting conditions are not met.
Processing PVA into agricultural mulch film demands strict control of melt temperature and shear history due to the polymer’s thermal sensitivity. On a single-screw extruder with a 24:1 L/D ratio and three-zone screw, the feed throat must be water-cooled to below 45°C to prevent pellet bridging, while the barrel profile is typically set from 180°C (zone 1) to 220°C (die). A melt temperature exceeding 235°C initiates acetic acid evolution and crosslinking, visible as gel specks in cast film. Twin-screw compounding lines (L/D 40:1, co-rotating, D = 25 mm) allow incorporation of plasticisers—glycerol at 12–18 phr or sorbitol at 8–12 phr—without the pre-gelation risk encountered in single-screw mixing. Glycerol at loadings above 18 phr reduces film tensile modulus below 200 MPa, which can cause sagging in raised-bed mulch applications where the film must span 80 cm bed widths unsupported. The blend must also exclude amine-based processing aids because residual amine groups promote imine condensation with any acetic acid liberated during melt processing, accelerating discolouration and chain branching that raises the melt viscosity index. In practice, blown film lines (BUR 2.5–3.0) running PVA mulch compound at 200–215°C achieve a gauge variation of ±12% over 1.2 m lay-flat width when equipped with dual-lip air rings and internal bubble cooling; without IBC, gauge uniformity deteriorates to ±25%, rendering the film unsuitable for precision mechanical laying. Pre-drying of PVA granules is mandatory at 80°C for 4 hours to achieve a moisture content below 0.3 wt%, as residual moisture at 0.8 wt% generates steam bubbles that nucleate pinholes during die exit, particularly when the melt strength is already compromised by low-viscosity grades.
Thickness selection for PVA agricultural mulch is not a routine specification but a balancing parameter directly linked to the crop cycle and soil microbial activity. Films at 12 µm thickness suppress weeds adequately for 4–6 weeks in spring vegetable production, whereas a 25 µm film maintains integrity for 10–14 weeks, necessary for indeterminate tomato crops. However, below 10 µm, mechanical laying tension at values above 40 N/m width induces irreversible necking, reducing coverage width by 15–20%. Degradation synchronisation—the point at which the film breaches in multiple locations allowing crop roots unimpeded soil access—must occur before the reproductive stage of the crop. For processing tomato planted in April in Mediterranean-climate soils (sandy loam, pH 6.8, 70% WHC), a 15 µm PVA film incorporating 5 wt% micronised cellulose fibre initiates fragmentation at 55 days after laying, which coincides with canopy closure; a 30 µm film of the same formulation delayed fragmentation to 95 days, forcing manual removal to prevent interference with harvest machinery. The thickness-degradation relationship is not linear: below the percolation threshold of plasticiser migration at 14 µm, dissolution front propagation accelerates due to capillary wicking along the fibre–matrix interface, doubling the dissolution rate compared to films thicker than 20 µm. This non-linearity demands site-specific calibration through burial trials mimicking local irrigation patterns.
Field trials conducted under the European Biodegradable Mulch Standard EN 17033:2018 require evidence of at least 90% film surface fragmentation within a defined time window relative to the cultivar’s phenology. PVA-based films meeting this standard typically achieve the criterion within 24 months of soil incorporation, whereas starch/PBAT blends can require 30–36 months in northern European soils where soil temperatures remain below 12°C for five months annually. The EN 17033 ecotoxicity tests (OECD 208 and 222) also impose limits on heavy metals and perfluorinated compounds; PVA resin producers supply grades that conform to the 200 mg/kg combined heavy metal threshold with a margin of at least 30%, provided tin-based residual catalysts from the saponification step are fully removed through methanol washing. A notable limitation: PVA mulch films cannot be used in fields where the soil is periodically submerged or has a permanent water table within 30 cm of the surface, because prolonged saturation converts the film into a gel layer that restricts gas exchange at the soil surface, causing elevated ethylene concentrations and root hypoxia in sensitive crops like cucurbits.
| Property | PVA (1788 grade) | PLA/starch blend | PBAT/starch blend | PE (conventional) |
|---|---|---|---|---|
| Film thickness range (µm) | 12–30 | 15–40 | 12–25 | 15–50 |
| Tensile strength MD (MPa, ASTM D882) | 30–45 | 18–25 | 22–35 | 25–35 |
| Soil fragmentation onset (days, 20°C, 60% WHC) | 45–80 | 60–120 (PLA phase persists>2 years) | 55–90 | No fragmentation |
| Disintegration 90% (months, EN 17033 bury) | 18–24 | 28–42 (dependent on PLA content) | 24–30 | Not applicable |
| Aerobic biodegradation (ISO 14855-1, % after 180 days) | 65–75% | 40–55% (PLA component incomplete) | 50–65% | 0 |
| Water vapour transmission rate (g/m²·day, 23°C, 85%RH) | 350–600 | 200–400 | 150–350 | 10–20 |
The high water vapour transmission of PVA mulch, typically 350–600 g/m²·day at 85% RH gradient, distinguishes it from polyolefin films and offers an agronomic advantage in regions prone to soil overheating. The evaporation cooling effect reduces mid-day soil temperatures by 3–5°C compared to black LDPE mulch, a parameter quantified using soil thermocouples at 10 cm depth in melon fields in Almería, Spain. This cooling can be counterproductive for heat-loving crops such as watermelon if soil temperature dips below 18°C at night; in such cases, a black masterbatch addition (carbon black 2.5 wt%) selectively attenuates the IR transparency of PVA and lifts the daytime soil temperature by 2°C without eliminating the transpiration pathway.
PVA mulch’s solubility creates a specific incompatible interface with calcium nitrate and ammonium polyphosphate liquid fertilisers applied through drip systems. When these saline solutions, with electrical conductivity exceeding 3.5 dS/m, contact the film edge near emitter outlets, the high ionic strength salt out the polymer, precipitating a low-molecular-weight fraction that blocks the orifice. Emitter clogging has been documented in field trials with Netafim DripNet PC 1.6 L/h emitters after 6–8 irrigation events containing 200 ppm NO₃⁻ as calcium nitrate at pH 5.8. The mitigation strategy requires either maintaining a minimum distance of 15 cm between emitter line and mulch edge or switching to potassium-based nitrogen sources that exhibit a lower salting-out effect. Additionally, the solubility of PVA is acutely sensitive to borate ions present in certain soil amendments; sodium tetraborate at concentrations as low as 50 mg/kg soil can crosslink dissolved PVA chains, forming a viscous hydrogel that reduces infiltration rates. This interaction is underreported in manufacturer specifications and constitutes a site-specific exclusion criterion for fields previously treated with boron-based microelement fertilisers.
Published data for PVA mulch film’s long-term ecotoxicity under repeated annual incorporation cycles—more than five consecutive seasons—is limited. The accumulation potential of the non-degraded fraction in soils with low microbial carbon biomass (<100 µg C/g soil) has not been characterised against the full test battery of ISO 15799:2019 (soil quality — guidance on the ecotoxicological characterization of soils and soil materials). This knowledge gap necessitates a conservative approach: for soils with organic matter below 1.5%, PVA mulch should be applied only in alternate years until field-aged residue mineralisation rates are validated via 14C-labelled polymer tracing studies that can distinguish respiratory CO₂ from the mulch versus background soil respiration.
