Natural rubber is widely known to possess good mechanical properties. However, due to the existence of numerous reactive double bonds on the molecular backbone, natural rubber is highly susceptible to degradation by thermal aging. To overcome such shortcomings, natural rubber is frequently blended with synthetic rubbers such as chloroprene rubber. Chloroprene rubber is one of the most important specialty rubber for nontire application, for example rubber fender. The present study investigates the effects of two different blend ratios of natural rubber (standard Indonesian rubber or SIR 10) and chloroprene rubber on the cure, tensile properties, and morphology of rubber blends. The blends of SIR 10/chloroprene rubber are prepared by using laboratory kneader and laboratory two‐roll mill. Rubber blending is made from mixture of natural rubber SIR 10 and synthetic rubber chloroprene rubber with variation of SIR 10/chloroprene rubber ratio PF1 100/0; PF2 70/30; PF3 30/70; PF4 0/100 phr. Furthermore, each variable is tested to determine the rheological and mechanical properties including tensile strength, elongation at break, hardness, and compression set. The addition of chloroprene rubber also causes an increment in the tensile strength and elongation at break. However, only PF3 shows satisfied result compared to the requirements standard (ISO 17357‐1:2014 Ship and Marine Technology‐Floating Pneumatic Rubber Fenders).

In the implementation of fertilization, only about 50% of the fertilizer can be absorbed by plants while some are degraded or drifted by groundwater so that fertilization becomes inefficient which will also pollute the environment with the content of N, P, and K. The loss of N as nitrogen gas due to denitrification is up to 30–40%, the loss of N as ammonia gas due to volatilization is about 10–20, the loss of N as nitrate due to the washing by water flow is about 44%, and erosion can reach 45%. One solution to this problem is using a slow release fertilizer (SRF) where the nutrient is released slowly within a certain time. The SRF technology modifies the fertilizer utilizing chitosan coating on granule surface of the fertilizer. Liquid chitosan is used for coating and it is sprayed on the surface of fertilizer granule in the rotary pan granulator. It is found that the resistance of the chitosan coated fertilizer in the water is about 3–6 months. The characteristics of the nutrients released from SRF NPK 16‐16‐16 coated with chitosan are about 103.26 mg nutrients of N, 21.8 mg nutrients of P, and 65.62 mg nutrients of K within a month of immersion time.

Tire retreading is a prospective industry. Old tires are repaired and retreaded with suitable tread compounds to fulfill the requirement as the new ones. One of the important components in tire retreading process is cushion compound. Cushion compound consists of unsaturated rubber, in this case natural rubber Hevea brasiliensis was used, less phr of filler compared to the retread compound, and additives such as peptizer, tackifier, processing oil, antioxidant, activator, accelerator and curatives. Tackifier is an important component in cushion compound since its role to make a bonding between different layer, the initial tire after buffing and new retread layer. Tackifier should has good resistance, good compatibility and does not affect the rheological and dynamical properties of bonded rubber. The general tackifier that used in industries are hexamethyl tetramine as methylene donor and resorcinol as methylene acceptor. There is certain reaction between those two additives that determine how good the performance of cushion compound and its effect to retreading process. To obtain optimum reaction, comparison between resorcinol and hexamethyl tetramine were varied as 1:1 (FRR1), 1:2 (FRR2) and 1:3 (FRR3). Hardness test, compression test, rebound resilience, tensile and tear strength, and FTIR were done to observe the optimum variation for retread application. Compared to the control with no tackifier at all, FRR2 showed the optimum result with 21.75 MPa (min. 19 Mpa) and 454,54% elongation at break (min. 450%). The most interesting result was observation by using FTIR, it was detected that the crosslink density was significantly higher than other formulation. It is a new breakthrough which is minimum tackifier with certain treatment could give better performance.

Indonesia merupakan salah satu negara penghasil karet terbesar setelah Thailand. Sehubungan dengan produksi karet alam di Indonesia, kultur tanaman Hevea brasiliensis secara ekonomi sangat penting bagi negara tropis penghasil karet. Salah satu peluang dari pemanfaatan lateks H. brasiliensis adalah dengan memproduksi karet densitas rendah yang memiliki kadar protein yang rendah untuk digunakan sebagai bahan pembuatan sponge untuk pipa apung lepas pantai atau sarung tangan, alat kontrasepsi (kondom), dan lain-lain. Tujuan dari penelitian ini adalah untuk menghasilkan karet alam yang memiliki densitas rendah, serta kandungan nitrogen total yang rendah,melalui sentrifugasi dan proses deproteinisasi dengan penambahan enzim protease(papain)dan kombinasi denaturan (β-merkaptoetanol dan SDS) pada fraksi karet dari lateksH. brasilliensis Muell Arg. Klon PR 255. Lateks disentrifugasi pada suhu 0C dengan kecepatan 4.000 rpm selama 180 menit dan 19.000 rpm selama 60 menit. Lateks akan terpisah menjadi tiga fraksi utama; yaitu fraksi karet (atas), C serum (tengah) dan partikel koloid (bawah). Fraksi karet diperlakukan dengan tiga variasi enzimatik. Enzimatik A, dilakukan penambahan enzim papain. Enzimatik B, dilakukan penambahan enzim papain, deterjen SDS dan β-merkaptoetanol secara bersamaan. Enzimatik C, dilakukan penambahan deterjen SDS dan βmerkaptoetanol terlebih dahulu, setelah diinkubasi selama 24 jam dilakukan penambahan enzim papain. Proses inkubasi dilakukan selama 48 dan 96 jam, pada suhu 37C. Densitas karet dan kadar nitrogen total dari fraksi karet sebelum dan sesudah proses enzimatik dianalisis. Hasil penelitian menunjukkan bahwa kondisi optimal penurunan kadar nitrogen didapat pada kecepatan 19.000 rpm selama 60 menit (waktuinkubasi selama 96 jam) yaitu sebesar 88,26% dengan kadar nitrogen total sebesar 0,05% (menurundarikadar nitrogen awal 0,40%) sertadensitasnyasebesar 0,8086 g/mL (menurun dari densitas awal 0,9287g/mL).Kadar nitrogen total sebelum sentrifugasi sebesar 0,40%, dan setelah sentrifugasi sebesar 0,30%. Densitas karet tanpa sentrifugasi, sesudah sentrifugasi pada kecepatan4.000 rpm dan sesudah proses enzimatik C masing-masing sebesar 0,9287; 0,8986 dan 0,8168 g/mL.Sedangkan untuk kecepatan 19.000 rpm, densitas karet tanpa sentrifugasi, setelah sentrifugasi dan setelah proses enzimatik C masing-masing sebesar 0,9287; 0,8890dan 0,8086 g/mL.

Indonesia is one of the largest natural rubber producers in the world. However, the utilization of natural rubber is still not optimal, even though with a touch of technology, natural rubber can be utilized to create technical products that have high added value. One of the rubber products is rubber airbag. The purpose of this research is to know the effect of variations of natural rubber type Standard Indonesian Rubber (SIR) 20 and ethylene propylene diene monomer (EPDM) rubber composition processed with auxiliary chemicals on the quality of mechanical properties of rubber airbag product which is considered quite optimal. Rubber compound is made from the mixture of natural rubber SIR 20 and synthetic rubber EPDM with variation of SIR 20/EPDM ratio A) 100/0; B) 90/10; C) 80/20; D) 0/100 phr. Rubber compound is made with kneader machine and open mill. Then its mechanical properties are tested in accordance with the target technical specifications to be achieved. Testing is done both before and after its immersion in sea water at 95 °C for 29 days. Test results both before and after immersion in sea water shows that the composition of natural rubber and EPDM has significant effect on mechanical properties and chemical structure of rubber compound vulcanizate. The optimum rubber compound formula for rubber airbag is sample A with 100 phr of SIR 20 composition with excellent mechanical properties of tensile strength, hardness, rebound resilience, and abrasion resistance.